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  • 1.
    Algesten, Grete
    Umeå universitet, Ekologi och geovetenskap.
    Regulation of carbon dioxide emission from Swedish boreal lakes and the Gulf of Bothnia2005Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The global carbon cycle is subject to intense research, where sources and sinks for greenhouse gases, carbon dioxide in particular, are estimated for various systems and biomes. Lakes have previously been neglected in carbon balance estimations, but have recently been recognized to be significant net sources of CO2.

    This thesis estimates emission of carbon dioxide (CO2) from boreal lakes and factors regulating the CO2 saturation from field measurements of CO2 concentration along with a number of chemical, biological and physical parameters. Concentration of dissolved organic carbon (DOC) was found to be the most important factor for CO2 saturation in lake water, whereas climatic parameters such as precipitation, temperature and global radiation were less influential. All lakes were supersaturated with and, thus, sources of CO2. Sediment incubation experiments indicated that in-lake mineralization processes during summer stratification mainly occurred in the pelagial. Approximately 10% of the CO2 emitted from the lake surface was produced in epilimnetic sediments.

    The mineralization of DOC and emission of CO2 from freshwaters was calculated on a catchment basis for almost 80,000 lakes and 21 major catchments in Sweden, together with rates of sedimentation in lakes and export of organic carbon to the sea. The total export of terrestrial organic carbon to freshwaters could thereby be estimated and consequently also the importance of lakes for the withdrawal of organic carbon export from terrestrial sources to the sea. Lakes removed 30-80% of imported terrestrial organic carbon, and mineralization and CO2 emission were much more important than sedimentation of carbon. The carbon loss was closely related to water retention time, where catchments with short residence times (<1 year) had low carbon retentions, whereas in catchments with long residence times (>3 years) a majority of the imported TOC was removed in the lake systems.

    The Gulf of Bothnia was also studied in this thesis and found to be a net heterotrophic system, emitting large amounts of CO2 to the atmosphere on an annual basis. The rate of CO2 emission was depending on the balance between primary production and bacterial respiration, and the system was oscillating between being a source and a sink of CO2.

  • 2. Andréasson, Per-Gunnar
    et al.
    Allen, Ann
    Aurell, Oskar
    Boman, Daniel
    Ekestubbe, Jonas
    Goerke, Ute
    Lundgren, Anders
    Nilsson, Patrik
    Sandelin, Stefan
    Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity2018Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 140, nr 3, s. 264-291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation with the underlying Mårma terrane, composed of quartzofeldspathic gneisses intruded by mafic and granitic rocks, the latter including a previously dated c. 845 Ma-old granite. The granite mingled with mildly alkaline dolerites chemically similar to transitional basalts of continental rifts. Following emplacement at shallow (andalusite stability) crustal levels, the igneous complex and host rocks underwent extensive deformation, metamorphism within the sillimanite-kyanite stability field and local migmatization. The Kebnekaise and Mårma terranes amalgamated in early Ordovician as indicated by the U-Pb age of 487±7 Ma obtained from titanite fabrics of deformed granite in thrust vicinity, and by 40Ar-39Ar results. The pressure increase in both terranes suggests that amalgamation occurred during initial subduction and imbrication. Correlation of the Mårma terrane with the KNC is discussed. Results obtained in this study give no reason to ascribe an exotic affinity to the Seve terranes of the Kebnekaise Mts.

  • 3. Andrén, Thomas
    et al.
    Björck, J
    Johnsen, S
    Correlation of Swedish glacial varves with the Greenland (GRIP) oxygen isotope record1999Ingår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 14, nr 4, s. 361-371Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the delta(18)O record from the GRIP ice-core using the Younger Dryas-Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10 995 to 10 700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas-Preboreal climatic shift is dated to ca. 10 650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10 440 to 10 320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas-Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10 300 clay-varve yr BP.

  • 4.
    Bartels, Pia
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Ask, Jenny
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Andersson, Agneta
    Umeå universitet, Umeå marina forskningscentrum (UMF).
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Allochthonous Organic Matter Supports Benthic but Not Pelagic Food Webs in Shallow Coastal Ecosystems2018Ingår i: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 21, nr 7, s. 1459-1470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rivers transport large amounts of allochthonous organic matter (OM) to the ocean every year, but there are still fundamental gaps in how allochthonous OM is processed in the marine environment. Here, we estimated the relative contribution of allochthonous OM (allochthony) to the biomass of benthic and pelagic consumers in a shallow coastal ecosystem in the northern Baltic Sea. We used deuterium as a tracer of allochthony and assessed both temporal variation (monthly from May to August) and spatial variation (within and outside river plume). We found variability in allochthony in space and time and across species, with overall higher values for zoobenthos (26.2 +/- 20.9%) than for zooplankton (0.8 +/- 0.3%). Zooplankton allochthony was highest in May and very low during the other months, likely as a result of high inputs of allochthonous OM during the spring flood that fueled the pelagic food chain for a short period. In contrast, zoobenthos allochthony was only lower in June and remained high during the other months. Allochthony of zoobenthos was generally higher close to the river mouth than outside of the river plume, whereas it did not vary spatially for zooplankton. Last, zoobenthos allochthony was higher in deeper than in shallower areas, indicating that allochthonous OM might be more important when autochthonous resources are limited. Our results suggest that climate change predictions of increasing inputs of allochthonous OM to coastal ecosystems may affect basal energy sources supporting coastal food webs.

  • 5.
    Becher, Marina
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Cryogenic soil processes in a changing climate2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A considerable part of the global pool of terrestrial carbon is stored in high latitude soils. In these soils, repeated cycles of freezing and thawing creates soil motion (cryoturbation) that in combination with other cryogenic disturbance processes may play a profound role in controlling the carbon balance of the arctic soil. Conditions for cryogenic soil processes are predicted to dramatically change in response to the ongoing climate warming, but little is known how these changes may affect the ability of arctic soils to accumulate carbon. In this thesis, I utilize a patterned ground system, referred to as non-sorted circles, as experimental units and quantify how cryogenic soil processes affect plant communities and carbon fluxes in arctic soils. I show that the cryoturbation has been an important mechanism for transporting carbon downwards in the studied soil over the last millennia. Interestingly, burial of organic material by cryoturbation appears to have mainly occurred during bioclimatic events occurring around A.D. 900-1250 and A.D. 1650-1950 as indicated by inferred 14C ages. Using a novel photogrammetric approach, I estimate that about 0.2-0.8 % of the carbon pool is annually subjected to a net downward transport induced by the physical motion of soil. Even though this flux seems small, it suggests that cryoturbation is an important transporter of carbon over centennial and millennial timescales and contributes to translocate organic matter to deeper soil layers where respiration proceeds at slow rates. Cryogenic processes not only affect the trajectories of the soil carbon, but also generate plant community changes in both species composition and abundance, as indicated by a conducted plant survey on non-sorted circles subjected to variable differential frost heave during the winter. Here, disturbance-tolerant plant species, such as Carex capillaris and Tofieldia pusilla, seem to be favoured by disturbance generated by the differential heave. Comparison with findings from a previous plant survey on the site conducted in the 1980s suggest that the warmer temperatures during the last decades have resulted in decreased differential heave in the studied non-sorted circles. I argue that this change in cryogenic activity has increased abundance of plants present in the 1980s. The fact that the activity and function of the non-sorted circles in Abisko are undergoing changes is further supported by their contemporary carbon dioxide (CO2) fluxes. Here, my measurements of CO2 fluxes suggest that all studied non-sorted circles act as net CO2 sources and thus that the carbon balance of the soils are in a transition state. My results highlight the complex but important relationship between cryogenic soil processes and the carbon balance of arctic soils.

  • 6.
    Becher, Marina
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Olid, Carolina
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Buried soil organic inclusions in non-sorted circles fields in northern Sweden: Age and Paleoclimatic context2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 1, s. 104-111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although burial of surface organic soil horizons into deeper mineral soil layers helps drive the long-term buildup of carbon in arctic soils, when and why buried horizons formed as result of cryoturbation in northern Sweden remain unclear. In this study, we used C-14 and Pb-210 dating to assess when organic matter was buried within non-sorted circles fields near Abisko in northern Sweden. In addition, we used aerial photos from 1959 and 2008 to detect eventual trends in cryogenic activities during this period. We found that organic matter from former organic horizons (stratigraphically intact or partly fragmented) corresponds to three major periods: 0-100 A. D., 900-1250 A. D., and 1650-1950 A. D. The latter two periods were indicated by several dated samples, while the extent of the oldest period is more uncertainty (indicated by only one sample). The aerial photos suggest a net overgrowth by shrub vegetation of previously exposed mineral soil surfaces since 1959. This overgrowth trend was seen in most of the studied fields (92 out of 137 analyzed fields), indicating that the cryogenic activity has mainly decreased in studied non-sorted circles fields since the 1950s. This latter interpretation is also supported by the absence of buried organic layers formed during the last decades. We suggest that the organic matter was buried during the transition from longer cold periods to warmer conditions. We believe these climatic shifts could have triggered regional scale burial of soil organic matter and thus affected how these soils sequestered carbon.

  • 7.
    Becher, Marina
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Olofsson, Johan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Cryogenic disturbance and its impact on carbon fluxes in a subarctic heathland2015Ingår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 10, nr 11, artikel-id 114006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Differential frost heave, along with the associated cryogenic disturbance that accompanies it, is an almost universal feature of arctic landscapes that potentially influences the fate of the soil carbon (C) stored in arctic soils. In this study, we quantify how gross ecosystem photosynthesis (GEP), soil respiration (Re) and the resulting net ecosystem exchange (NEE) vary in a patterned ground system (non-sorted circles) at plot-scale and whole-patterned ground scales in response to cryogenic disturbances (differential heave and soil surface disruption). We found that: (i) all studied non-sorted circles (n=15) acted as net CO2 sources (positive NEE); (ii) GEP showed a weaker decrease than Re in response to increased cryogenic disturbance/decreased humus cover, indicating that undisturbed humus-covered sites are currently the main source of atmospheric CO2 in the studied system. Interestingly, Re fluxes normalized to C pools indicated that C is currently respired more rapidly at sites exposed to cryogenic disturbances; hence, higher NEE fluxes at less disturbed sites are likely an effect of a more slowly degrading but larger total pool that was built up in the past. Our results highlight the complex effects of cryogenic processes on the C cycle at various time scales. 

  • 8.
    Bigler, Christian
    et al.
    Umeå universitet, Ekologi och geovetenskap.
    Grahn, E.
    Larocque, I.
    Jeziorski, A.
    Hall, Roland
    Umeå universitet, Ekologi och geovetenskap.
    Holocene environmental change at Lake Njulla (999 m asl), northern Sweden: a comparison with four small nearby lakes along an altitudinal gradient2003Ingår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 29, nr 1, s. 13-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We assess Holocene environmental change at alpine Lake Njulla (68degrees22'N, 18degrees42'E, 999 m a.s.l.) in northernmost Sweden using sedimentary remains of chironomid head capsules and diatoms. We apply regional calibration sets to quantitatively reconstruct mean July air temperature (using chironomids and diatoms) and lake-water pH (using diatoms). Both chironomids and diatoms infer highest temperatures (1.7-2.3degreesC above present-day estimates, including, a correction for glacio-isostatic land up-lift by 0.6degreesC) during the early Holocene (c. 9,500-8,500 cal. yrs BP). Diatoms suggest a decreasing lake-water pH trend (c. 0.6 pH units) since the early Holocene. Using detrended canonical correspondence analysis (DCCA), we compare the Holocene development of diatom communities in Lake Njulla with four other nearby lakes (Lake 850, Lake Tibetanus, Vuoskkujavri, Vuolep Njakajaure) located along an altitudinal gradient. All five lakes show similar initial DCCA scores after deglaciation, suggesting that similar environmental processes such as high erosion rates and low light availability associated with high summer temperature appear to have regulated the diatom community, favouring high abundances of Fragilaria species. Subsequently, the diatom assemblages develop in a directional manner, but timing and scale of development differ substantially between lakes. This is attributed primarily to differences in the local geology, which is controlling the lake-water pH. Imposed on the basic geological setting, site-specific processes such as vegetation development, climate, hydrological setting and in-lake processes appear to control lake development in northern Sweden.

  • 9.
    Blume-Werry, Gesche
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Wilson, Scott D.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Kreyling, Juergen
    Milbau, Ann
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    The hidden season: growing season is 50% longer below than above ground along an arctic elevation gradient2016Ingår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, nr 3, s. 978-986Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is compelling evidence from experiments and observations that climate warming prolongs the growing season in arctic regions. Until now, the start, peak, and end of the growing season, which are used to model influences of vegetation on biogeochemical cycles, were commonly quantified using above-ground phenological data. Yet, over 80% of the plant biomass in arctic regions can be below ground, and the timing of root growth affects biogeochemical processes by influencing plant water and nutrient uptake, soil carbon input and microbial activity. We measured timing of above- and below-ground production in three plant communities along an arctic elevation gradient over two growing seasons. Below-ground production peaked later in the season and was more temporally uniform than above-ground production. Most importantly, the growing season continued c. 50% longer below than above ground. Our results strongly suggest that traditional above-ground estimates of phenology in arctic regions, including remotely sensed information, are not as complete a representation of whole-plant production intensity or duration, as studies that include root phenology. We therefore argue for explicit consideration of root phenology in studies of carbon and nutrient cycling, in terrestrial biosphere models, and scenarios of how arctic ecosystems will respond to climate warming.

  • 10.
    Bäckstrand, Kristina
    Stockholms universitet, Institutionen för geologi och geokemi.
    Carbon gas biogeochemistry of a northern peatland - in a dynamic permafrost landscape2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis is about biogeochemical processes of a northern peatland and their importance as a link between the climate and the terrestrial system. Increased temperatures on a global level, and particularly in the Arctic, have led to melting permafrost and changes in hydrology. In turn, this affect the natural exchange of radiatively important trace gases between land and atmosphere that may reinforce climate change. The aim of this thesis is to increase the understanding about the exchange of carbon dioxide (CO2), methane (CH4) and non-methane volatile organic compounds (NMVOCs) occurring in northern peatlands, to decrease uncertainty about their future carbon (C) balance. In order to pursue this aim, we designed a study that allowed measuring the C exchange at a subarctic peatland, accounting for spatial and temporal analysis at several levels.

    The field site was the Stordalen mire, northern Sweden. Exchange rates of CO2, and total hydrocarbons (THCs; CH4 and NMVOCs) were measured using an automatic chamber system for up to six years, at three different types of vegetation communities and permafrost regimes. The gas exchange was found to relate to different environmental and biological variables at different vegetation communities and at different temporal scales. Differences in flux rates and controls between sites could be explained with biological and environmental variables in a better way than the seasonal and interannual variability within a site.

    Snow season flux measurements were determined to be of high importance regarding the annual C budget. By excluding the snow season, the potential C source strength of a peatland is likely to be underestimated. The importance of combining the THCs with the CO2 to estimate the annual C balance was demonstrated as THC could be sufficient to shift the mire from a sink to a source of C to the atmosphere. Again, the C source strength may be significantly underestimated if only focusing on CO2 fluxes in wet peatland environments.

  • 11.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Jackowicz-Korczyński, Marcin
    Mastepanov, Mikhail
    Christensen, Torben, R.
    Bastviken, David
    Annual carbon gas budget for a subarctic peatland, northern Sweden2010Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, nr 1, s. 95-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temperatures in the Arctic regions are rising, thawing permafrost and exposing previously stable soil organic carbon (OC) to decomposition. This can result in northern latitude soils, which have accumulated large amounts of OC potentially shifting from atmospheric C sinks to C sources with positive feedback on climate warming. In this paper, we estimate the annual net C gas balance (NCB) of the subarctic mire Stordalen, based on automatic chamber measurements of CO2 and total hydrocarbon (THC; CH4 and NMVOCs) exchange. We studied the dominant vegetation communities with different moisture and permafrost characteristics; a dry Palsa underlain by permafrost, an intermediate thaw site with Sphagnum spp. and a wet site with Eriophorum spp. where the soil thaws completely. Whole year accumulated fluxes of CO2 were estimated to 29.7, −35.3 and −34.9 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum sites (positive flux indicates an addition of C to the atmospheric pool). The corresponding annual THC emissions were 0.5, 6.2 and 31.8 gC m−2 for the same sites. Therefore, the NCB for each of the sites was 30.2, −29.1 and −3.1 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum site. On average, the whole mire was a CO2 sink of 2.6 gC m−2 and a THC source of 6.4 gC m−2 over a year. Consequently, the mire was a net source of C to the atmosphere by 3.9 gC m−2 (based on area weighted estimates for each of the three plant communities). Early and late snow season efflux of CO2 and THC emphasize the importance of winter measurements for complete annual C budgets. Decadal vegetation changes at Stordalen indicate that both the productivity and the THC emissions increased between 1970 and 2000. Considering the GWP100 of CH4, the net radiative forcing on climate increased 21% over the same time. In conclusion, reduced C compounds in these environments have high importance for both the annual C balance and climate.

  • 12.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Mastepanov, Mikhail
    Stockholms universitet, Institutionen för geologi och geokemi.
    Christensen, Torben, R.
    INES, University of Lund.
    Bastviken, David
    Stockholms universitet, Institutionen för geologi och geokemi.
    Nonmethane volatile organic compound flux from a subarctic mire in northern Sweden2008Ingår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, nr 2, s. 226-237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biogenic NMVOCs are mainly formed by plants and microorganisms. They have strong impact on the local atmospheric chemistry when emitted to the atmosphere. The objective of this study was to determine if there are significant emissions of non-methane volatile organic compounds (NMVOCs) from a subarctic mire in northern Sweden. Subarctic peatlands in discontinuous permafrost regions are undergoing substantial environmental changes due to their high sensitivity to climate warming and there is need for includingNMVOCs in the overall carbon budget. Automatic and manual chamber measurements were used to estimateNMVOCfluxes from three dominating subhabitats on the mire during three growing seasons. Emission rates varied and were related to plant species distribution and seasonal net ecosystem exchange of carbon dioxide. The highest fluxes were observed from wetter sites dominated by Eriophorum and Sphagnum spp. Total NMVOC emissions from the mire (∼17 ha) is estimated to consist of ∼150 kgC during a growing season with 150 d. NMVOC fluxes can account for ∼5% of total net carbon exchange (−3177 kgC) at the mire during the same period. NMVOC emissions are therefore a significant component in a local carbon budget for peatlands

  • 13.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Institutionen för geologi och geokemi.
    Mastepanov, Mikhail
    GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University.
    Christensen, Torben, R.
    GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University.
    Bastviken, David
    Stockholms universitet, Institutionen för geologi och geokemi.
    Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden2008Ingår i: Journal of Geophysical Research – Biogeosciences, Vol. 113, s. G03026-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This is a study of the spatial and temporal variability of total hydrocarbon (THC) emissions from vegetation and soil at a subarctic mire, northern Sweden. THCs include methane (CH4) and nonmethane volatile organic compounds (NMVOCs), both of which are atmospherically important trace gases and constitute a significant proportion of the carbon exchange between biosphere and atmosphere. Reliable characterization of the magnitude and the dynamics of the THC fluxes from high latitude peatlands are important when considering to what extent trace gas emissions from such ecosystems may change and feed back on climate regulation as a result of warmer climate and melting permafrost. High frequency measurements of THC and carbon dioxide (CO2) were conducted during four sequential growing seasons in three localities representing the trophic range of plant communities at the mire. The magnitude of the THC flux followed the moisture gradient with increasing emissions from a dry Palsa site (2.2 ± 0.1 mgC m−2 d−1), to a wet intermediate melt feature with Sphagnum spp. (28 ± 0.3 mgC m−2 d−1) and highest emissions from a wet Eriophorum spp. site (122 ± 1.4 mgC m−2 d−1) (overall mean ±1 SE, n = 2254, 2231 and 2137). At the Palsa site, daytime THC flux was most strongly related to air temperature while daytime THC emissions at the Sphagnum site had a stronger relation to ground temperature. THC emissions at both the wet sites were correlated to net ecosystem exchange of CO2. An overall spatial correlation indicated that areas with highly productive vegetation communities also had high THC emission potential.

  • 14.
    Conrad, Sarah
    et al.
    Luleå University of Technology.
    Ingri, Johan
    Luleå University of Technology.
    Gelting, Johan
    Luleå University of Technology.
    Nordblad, Fredrik
    Luleå University of Technology.
    Engström, Emma
    Luleå University of Technology.
    Rodushkin, Ilia
    ALS Laboratory Group, Luleå.
    Andersson, Per
    Naturhistoriska riksmuseet, Forskningsavdelningen centralt.
    Porcelli, Don
    Oxford University, Oxford.
    Gustafsson, Örjan
    Stockholm University, Stockholm.
    Semiletov, Igor
    University of Alaska, USA.
    Öhlander, Björn
    Luleå University of Technology.
    Distributionof Fe isotopes in particles and colloids in the salinity gradient along theLena River plume, Laptev Sea2019Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 16, s. 1305-1319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Riverine Fe input is the primary Fe source to the ocean. This study is focused on the distribution of Fe along the Lena River freshwater plume in the Laptev Sea using samples from a 600 km long transect in front of the Lena River mouth. Separation of the particulate (>0.22µm), colloidal (0.22µm – 1kDa), and truly dissolved (<1kDa) fractions of Fe was carried out. The total Fe concentrations ranged from 0.15 to 57 µM with Fe dominantly as particulate Fe. The loss of > 99% of particulate Fe and about 90% of the colloidal Fe was observed across the shelf, while the truly dissolved phase was almost constant across the Laptev Sea. Thus, the truly dissolved Fe could be an important source of bioavailable Fe for plankton in the central Arctic Ocean, together with the colloidal Fe. Fe-isotope analysis showed that the particulate phase and the sediment below the Lena River freshwater plume had negative δ56Fe values (relative to IRMM-14). The colloidal Fe phase showed negative δ56Fe values close to the river mouth (about -0.20‰) and positive δ56Fe values in the outermost stations (about +0.10‰).

    We suggest that the shelf zone acts as a sink for Fe particles and colloids with negative δ56Fe values, representing chemically reactive ferrihydrites. While the positive δ56Fe values of the colloidal phase within the outer Lena River freshwater plume, might represent Fe-oxyhydroxides, which remain in the water column, and will be the predominant δ56Fe composition in the Arctic Ocean.

  • 15. Cooper, Claire L.
    et al.
    Swindles, Graeme T.
    Watson, Elizabeth J.
    Savov, Ivan P.
    Gałka, Mariusz
    Gallego-Sala, Angela
    Borken, Werner
    Evaluating tephrochronology in the permafrost peatlands of northern Sweden2019Ingår i: Quaternary Geochronology, ISSN 1871-1014, E-ISSN 1878-0350, Vol. 50, s. 16-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tephrochronology is an increasingly important tool for the dating of sediment and peat profiles for palaeoecological, palaeoclimatic and archaeological research. However, although much work has been done on tephra in temperate peatlands, there have been very few in-depth investigations of permafrost peatlands. Here we present the analysis of nine peatland cores from Abisko, northern Sweden, and show that the presence of tephra layers may be highly variable even over a scale of <10 km. Using electron probe microanalysis (EPMA) combined with age-depth profiles compiled from radiocarbon (14C) and 210Pb dating of peat records, we identify the Hekla 1104, Hekla 1158, Hekla-Selsund and the Hekla 4 tephra layers. We also infer the presence of the Askja 1875 tephra, in addition to an unassigned tephra dating from between 1971–1987 AD in two separate cores. Five of the nine analysed cores do not contain distinct tephra layers. Volcanic ash deposits in northern Scandinavia are subject to both regional-scale variations in climate and atmospheric circulation, and local-scale variations on the order of tens of kilometres in topography, vegetation, snow cover, and ground permeability. The extreme inconsistency of tephra preservation within a small study area (∼3000 km2) brings into question the reliability of tephrochronology within permafrost peatlands, and highlights the necessity of alternative methods for dating peat profiles in this region.

  • 16.
    Cornelissen, Johannes H C
    et al.
    Vrije Universiteit.
    Van Bodegom, Peter M
    Vrije Universiteit.
    Aerts, Rien
    Vrije Universiteit.
    Callaghan, Terry V
    University of Sheffield.
    Van Logtestijn, Richard S.P.
    Vrije Universiteit.
    Alatalo, Juha
    VINNOVA.
    Chapin, Stuart F.
    University of Alaska.
    Gerdol, Renato G
    Università degli Studi di Ferrara Dipartimento delle Risorse Naturali e Cultural.
    Gudmundsson, Jon
    Agricultural University of Iceland.
    Gwynn-Jones, Dylan
    University of Wales.
    Hartley, Anne E
    Florida International University.
    Hik, David S
    University of Alberta.
    Hofgaard, Annika
    Norwegian Institute for Nature Research.
    Jónsdóttir, Ingibjörg S.
    Agricultural University of Iceland.
    Karlsson, Staffan
    Vetenskapsrådet.
    Klein, Julia A
    Colorado State University.
    Laundre, Jim
    Marine Biological Labratory.
    Magnusson, Borgthor
    Icelandic Institute of Natural History.
    Michelsen, Anders
    University of Copenhagen.
    Molau, Ulf
    Göteborgs Universitet.
    Onipchenko, Vladimir G.
    Moscow State University.
    Quested, Helen M.
    Stockholms Universitet.
    Sandvik, Sylvi M
    Agder University College.
    Schmidt, Inger K.
    Royal Veterinary and Agricultural University Denmark.
    Shaver, Gus R.
    Marine Biological Labratory.
    Solheim, Bjørn S
    University of Tromsø.
    Soudzilovskaia, Nadejda A
    Vrije Universiteit, Moscow State University.
    Stenström, Anna
    Länsstyrelsen Västra Götaland.
    Tolvanen, Anne
    Finnish Forest Research Institute.
    Totland, Ørjan T
    Norwegian University of Life Sciences.
    Wada, Naoya W
    University of Toyama.
    Welker, Jeffrey M
    University of Alaska Anchorage.
    Zhao, Xinquan
    Chinese Academy of Sciences.
    Brancaleoni, Lisa
    Brancaleoni, Laura
    De Beus, Miranda A.H
    Cooper, Elisabeth J.
    Dalen, Linda
    Harte, John
    Hobbie, Sarah E
    Hoefsloot, Gerlof
    Jägerbrand, Annika K
    Göteborg University.
    Jonasson, Sven
    Lee, John A
    Lindblad, Karin
    Melillo, Jerry M
    Neill, Christopher
    Press, Malcolm C
    Rozema, Jelte
    Zielke, Matthias
    Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes2007Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 10, nr 7, s. 619-627Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.

    Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

  • 17.
    Danielsson, Sara
    et al.
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Odsjö, Tjelvar
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Bignert, Anders
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Remberger, Mikael
    Utförare miljöövervakning, Naturhistoriska riksmuseet, NRM.
    Organic Contaminants in Moose (Alces alces) and Reindeer (Rangifer tarandus) in Sweden from the past twenty years: Comments Concerning the National Swedish Contaminant Monitoring Programme in Terrestrial Biota2008Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Föreliggande rapport är resultatet av ett uppdrag från Naturvårdsverket (Överenskommelse 221 0730) som syftar till att ta fram en aktuell bild av förekomsten av ett antal pesticider eller ofullständigt kända föroreningar i svensk terrestrisk natur där alltså osäkerhet om ämnenas spridning och ackumulation i landlevande organismvärlden råder. Som matris i detta fall har vävnader och organ av älg och ren från mellersta respektive norra Sverige valts. Matriserna finns tillgängliga i Miljöprovbanken vid Naturhistoriska riksmuseet Valet av ämnen har vägletts av tidigare resultat från övervakningen av föroreningar i svensk natur samt av resultat från screeningundersökningar av ofullständigt kända ämnen som tagits fram i Naturvårdsvekets regi. Listan över analyserade ämnen innehåller enskilda substanser samt närbesläktade substanser tillhörande bl. a. följande grupper: klorbensen, HCBD, oktaklorstyren, PCB, DDT, klordan, HCH, PBDE, dioxiner, furaner, endosulfan, heptaklor, pentaklorfenol och PAH. Från Grimsö i Västmanland har vävnadsprover av årskalvar av älg insamlats till Miljöprovbanken och använts för analys av innehåll av miljögifter i denna studie. Med några få undantag är de provtagna individerna av hankön. Skillnader i halter av kadmium mellan könen har i tidigare studier visat sig icke existera. De utvalda proven av älg representerar perioden 1986-2005. Ett homogenat av muskel har beretts per år under perioden baserat på 10 g av tio individer per år. På samma sätt har prover av ren från sommarbetet S Abisko årligen insamlats i Rensjön NV Kiruna i samband med första höstslakten i mitten av september. Vävnadsprover har tagits av handjur av en ålder mellan 2 och 4 år, mestadels av 3-åriga djur. 1998 uppsköts den ordinarie slakten från första halvan av september till första halvan av november, vilket bör uppmärksammas vid tolkningen av analysresultaten. På samma sätt sköts slakten 2004 fram till mitten av december. Det förhållandet att renen förflyttas avsevärda sträckor under höstvandringen, från sommarbetet i de västra delarna av fjällkedjan till det mellansvenska skogslandet under vintern medför en ändring av föda, vilket kan inverka på exponering och bioackumulation av de studerade substanserna. Ju längre avvikelse från normal slakttid desto längre exponering via lavar som är stapelföda i skogslandet under vintern och som innehåller högre koncentrationer av många ackumulerade ämnen. För den aktuella studien valdes hanrenar av tre års ålder härrörande från Gabna, Lævas and Girjas samebyar vilka bildar ett sammanhängande område i norra Lappland. Provserien omfattar perioden 1987-2006. Ett homogenat per år bereddes baserat på 12 g muskel från tio individer per år. Många av de analyserade ämnena förekommer i koncentrationer under detektionsnivån (LOD) under alla eller de flesta av de undersökta åren (Tabell 2). Halterna funna i älg och ren är i många fall lägre än de nivåer som observerats i fisk från såväl limniska som marina områden. Som exempel har PBDE och HBCD inte ens detekterats i vare sig älg eller ren men finns närvarande i både insjöfisk och havsfisk (Bignert et al 2008). Penta- och hexaklorbensen, oktaklorstyren, polyklorerade bifenyler, - och -hexaklor-cyklohexan och polycykliska aromatiska kolväten förekommer samtliga i halter över LOD under samtliga eller större delen av åren under den undersökta perioden. Koncentrationerna av dessa ämnen har sjunkit med undantag för PAH där koncentrationerna är ungefär desamma under hela perioden. Den genomsnittliga årliga nedgången ligger mellan 3% och 10% med undantag för -HCH som visar den mest uttalade minskningen med 22% i älg och 17% i ren. Dessa resultat är samstämmiga med vad som observerats i biota från insjöar och marina områden i Sverige (Bignert et al. 2008, Bignert 2001). De sjunkande halterna i landanknuten biota under de gångna 20 åren är sannolikt orsakade av regleringar och ansträngningar för att minimera utsläpp av kända persistenta, bioackumulerande och toxiska ämnen till miljön. Ämnen hörande till PAHerna är huvudsakligen oavsiktligt spridda genom ofullständig förbränning av organiska ämnen. Källorna är många och varierande och till följd därav svåra att åtgärda med förbättringar. Detta är troligtvis förklaringen till avsaknaden av nedgående tendens för PAHer. Koncentrationerna av PFCs i både älg och ren var i allmänhet låga. Samtliga analyserade prover hade koncentrationer under LOQ. Närvaro av PFOSA, PFOS och PFOA kunde emellertid detekteras vissa år men inte i nivåer tillräckligt höga för att kvantifieras

  • 18. Denfeld, Blaize A.
    et al.
    Baulch, Helen M.
    del Giorgio, Paul A.
    Hampton, Stephanie E.
    Karlsson, Jan
    A synthesis of carbon dioxide and methane dynamics during the ice-covered period of northern lakes2018Ingår i: Limnology and Oceanography Letters, ISSN 2378-2242, Vol. 3, nr 3, s. 117-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ice-covered period on lakes in the northern hemisphere has often been neglected or assumed to have less importance relative to the open water season. However, recent studies challenge this convention, suggesting that the winter period is more dynamic than previously thought. In this review, we synthesize the current understanding of under-ice carbon dioxide (CO2) and methane (CH4) dynamics, highlighting the annual importance of CO2 and CH4 emissions from lakes at ice-melt. We compiled data from 25 studies that showed that the ice-melt period represents 17% and 27% of the annual CO2 and CH4 emissions, respectively. We also found evidence that the magnitude and type of emission (i.e., CO2 and CH4) varies with characteristics of lakes including geographic location, lake morphometry, and physicochemical conditions. The scarcity of winter and spring carbon data from northern lakes represents a major gap in our understanding of annual budgets in these lakes and calls for future research during this key period.

  • 19. Deng, J.
    et al.
    Li, C.
    Frolking, S.
    Zhang, Y.
    Bäckstrand, Kristina
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Crill, Patrick
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Assessing effects of permafrost thaw on C fluxes based on multiyear modeling across a permafrost thaw gradient at Stordalen, Sweden2014Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, nr 17, s. 4753-4770Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Northern peatlands in permafrost regions contain a large amount of organic carbon (C) in the soil. Climate warming and associated permafrost degradation are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is uncertain. We incorporated a permafrost model, Northern Ecosystem Soil Temperature (NEST), into a biogeochemical model, DeNitrification-DeComposition (DNDC), to model C dynamics in high-latitude peatland ecosystems. The enhanced model was applied to assess effects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen, Sweden. DNDC simulated soil freeze-thaw dynamics, net ecosystem exchange of CO2 (NEE), and CH4 fluxes across three typical land cover types, which represent a gradient in the process of ongoing permafrost thaw at Stordalen. Model results were compared with multiyear field measurements, and the validation indicates that DNDC was able to simulate observed differences in seasonal soil thaw, NEE, and CH4 fluxes across the three land cover types. Consistent with the results from field studies, the modeled C fluxes across the permafrost thaw gradient demonstrate that permafrost thaw and the associated changes in soil hydrology and vegetation not only increase net uptake of C from the atmosphere but also increase the annual to decadal radiative forcing impacts on climate due to increased CH4 emissions. This study indicates the potential of utilizing biogeochemical models, such as DNDC, to predict the soil thermal regime in permafrost areas and to investigate impacts of permafrost thaw on ecosystem C fluxes after incorporating a permafrost component into the model framework.

  • 20. Dinasquet, Julie
    et al.
    Richert, Inga
    Logares, Ramiro
    Yager, Patricia
    Bertilsson, Stefan
    Riemann, Lasse
    Mixing of water masses caused by a drifting iceberg affects bacterial activity, community composition and substrate utilization capability in the Southern Ocean2017Ingår i: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 19, nr 6, SI, s. 2453-2467Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The number of icebergs produced from ice-shelf disintegration has increased over the past decade in Antarctica. These drifting icebergs mix the water column, influence stratification and nutrient condition, and can affect local productivity and food web composition. Data on whether icebergs affect bacterioplankton function and composition are scarce, however. We assessed the influence of iceberg drift on bacterial community composition and on their ability to exploit carbon substrates during summer in the coastal Southern Ocean. An elevated bacterial production and a different community composition were observed in iceberg-influenced waters relative to the undisturbed water column nearby. These major differences were confirmed in short-term incubations with bromodeoxyuridine followed by CARD-FISH. Furthermore, one-week bottle incubations amended with inorganic nutrients and carbon substrates (a mix of substrates, glutamine, Nacetylglucosamine, or pyruvate) revealed contrasting capacity of bacterioplankton to utilize specific carbon substrates in the iceberg-influenced waters compared with the undisturbed site. Our study demonstrates that the hydrographical perturbations introduced by a drifting iceberg can affect activity, composition, and substrate utilization capability of marine bacterioplankton. Consequently, in a context of global warming, increased frequency of drifting icebergs in polar regions holds the potential to affect carbon and nutrient biogeochemistry at local and possibly regional scales.

  • 21. Doguzhaeva, Larisa A
    et al.
    Bengtson, Stefan
    Reguero, Marcelo A
    Mörs, Thomas
    An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods.2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 3, artikel-id e0172169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyroteuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. This hypothesis has been recently supported by newly recorded diverse bactritoid-like coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod indicative of an endochochleate branch with an origin independent from subclass Bactritoidea has been reported.

    METHODOLOGY/PRINCIPAL FINDINGS: Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitin-compatible microlaminated shell walls and broadly expanded central siphuncles. The morphological, ultrustructural and chemical data were determined and characterized through comparisons with extant and extinct taxa using Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS).

    CONCLUSIONS/SIGNIFICANCE: Our study presents the first evidence for an evolutionary lineage of internally shelled cephalopods with independent origin from Bactritoidea/Coleoidea, indicating convergent evolution with the subclass Coleoidea. A new subclass Paracoleoidea Doguzhaeva n. subcl. is established for accommodation of orthoconic cephalopods with the internal shell associated with a broadly expanded central siphuncle. Antarcticerida Doguzhaeva n. ord., Antarcticeratidae Doguzhaeva n. fam., Antarcticeras nordenskjoeldi Doguzhaeva n. gen., n. sp. are described within the subclass Paracoleoidea. The analysis of organic-rich shell preservation of A. nordenskjoeldi by use of SEM/EDS techniques revealed fossilization of hyposeptal cameral soft tissues. This suggests that a depositional environment favoring soft-tissue preservation was the factor enabling conservation of the weakly mineralized shell of A. nordenskjoeldi.

  • 22. Dörr, N.
    et al.
    Lisker, F.
    Clift, P. D.
    Carter, A.
    Gee, David G.
    Uppsala universitet, Geofysik.
    Tebenkov, A. M.
    Spiegel, C.
    Late Mesozoic-Cenozoic exhumation history of northern Svalbard and its regional significance: Constraints from apatite fission track analysis2012Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 514, s. 81-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The late Mesozoic-Cenozoic was a time of profound tectonic activity in the Arctic, with incipient spreading in the Arctic Ocean, Baffin Bay-Labrador Sea and North Atlantic, as well as the northward movement of the Greenland microplate leading to collision and deformation in Greenland, Arctic Canada and Svalbard (Eurekan Orogeny). It is, however, still unclear, how northern Svalbard, situated at the northwestern edge of the Barents Shelf, was affected by these processes. Furthermore, northern Svalbard has been proposed to have been a Cretaceous-Cenozoic sediment source to surrounding regions because it lacks a post-Devonian sedimentary cover. When erosion took place and how that related to the tectonic history of the Arctic, is yet unresolved. In order to reconstruct the erosion history of northern Svalbard, we constrained its thermal evolution using apatite fission track (AFT) thermochronology. Our data reveal AFT ages between 62 +/- 5 and 214 +/- 10 Ma, recording late Mesozoic-early Paleogene exhumation. Our data show that northern Svalbard was emergent and experienced erosion from the Early Jurassic and presumably through the Cenozoic, although total exhumation was restricted to similar to 6 km. Pronounced exhumation took place during Jurassic-Cretaceous time, probably linked to the extensional tectonics during the opening of the Amerasian Basin (Arctic Ocean). In contrast, Cenozoic ocean basin formation and the Eurekan deformation did not cause significant erosion of northem Svalbard. Nonetheless, AFT data show that Late Cretaceous-Early Paleocene fault-related exhumation affected some parts of northern Svalbard. Fault zones were reactivated due to the reorganization of Arctic landmasses during an early phase of the Eurekan deformation, which implies that this episode commenced similar to 20 m.y. earlier in Svalbard than previously understood.

  • 23.
    Elbrächter, Malte
    et al.
    Deutsches Zentrum für Marine Diversitätsforschung.
    Gottschling, Marc
    Department of Geosciences, Oslo university.
    Hildebrand-Habel, Tania
    University of Stavanger.
    Keupp, Helmut
    Abisko Scientific Research Station.
    Kohring, Rolf
    Freie Universität Berlin.
    Lewis, Jane
    University of Westminster.
    Meier, Sebastian
    Christian-Albrechts-Universität zu Kiel.
    Montresor, Marina
    Stazione Zoologica ‘A. Dohrn’, Napoli.
    Streng, Michael
    Uppsala universitet, Paleobiologi.
    Versteegh, Gerard
    Universität Hamburg.
    Willems, Helmut
    Universität Bremen.
    Zonneveld, Karin
    Universität Bremen.
    Establishing an Agenda for Calcareous Dinoflagellate Research (Thoracosphaeraceae, Dinophyceae) including a nomenclatural synopsis of generic names2008Ingår i: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 57, nr 4, s. 1289-1303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Calcareous dinoflagellates are considered to be a monophyletic group of peridinoid taxa that have the potential to produce calcified exoskeletal structures during the life cycle, or that derive from such forms. Frequently, these calcareous bodies are excellently preserved in the fossil record and have received increased attention during the past three decades with regard to their use in biostratigraphy, climate and environmental reconstruction. Fossil and extant taxa have been classified in various, partly concurring, systematic concepts, using character complexes of the theca, cyst wall ultrastructure and archaeopyle/operculum morphology. The significance of such character complexes is briefly discussed in the light of molecular data that have been accumulated during the past decade. Over the years, the number of published taxonomic names has increased, partly due to nomenclatural changes. We propose that the entirety of calcareous dinoflagellates, and non-calcareous relatives derived from them, is accommodated in a single family of the order Peridiniales, the Thoracosphaeraceae, combining the former segregated taxonomic units Calciodinelloideae, a subfamily within Peridiniaceae, and Thoracosphaerales, a separate dinoflagellate order. As a result of a meeting of calcareous dinoflagellate specialists, we outline major subjects that are in need of re-investigation and -evaluation (an Agenda for Calcareous Dinoflagellate Research). In order to contribute to a consistent and stable nomenclature and taxonomy of calcareous dinoflagellates, we list 97 published generic names assigned to known calcareous dinoflagellates in a nomenclatural synopsis, with species names indicating their types and information on type locality and stratigraphy. We evaluate the status of these names—whether validly published and, if so, whether legitimate—,a crucial first step for any revisionary work in the future.

  • 24. ENGELBRECHT, Andrea
    et al.
    Mörs, Thomas
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    REGUERO, Marcelo
    KRIWET, Jürgen
    Revision of Eocene Antarctic carpet sharks (Elasmobranchii, Orectolobiformes) from Seymour Island, Antarctic Peninsula2016Ingår i: Journal of Systematic Palaeontology, ISSN 1477-2019, E-ISSN 1478-0941Artikel i tidskrift (Refereegranskat)
  • 25.
    Erickson, Lance
    Gustavus Adolphus College.
    Mercury Dynamics In Sub-Arctic Lake Sediments Across A Methane Ebullition Gradient2014Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
  • 26.
    Ericsson, Göran
    et al.
    SLU, Umeå.
    Larsson, Thomas B
    Umeå universitet, Institutionen för idé- och samhällsstudier.
    Rosqvist, Gunhild
    Stockholms universitet.
    Jonasson, Christer
    Polarforskningssekretariatet.
    Älgen flyr när klimatet ändras2011Ingår i: Miljötrender, ISSN 1403-4743, nr 4, s. 12-13Artikel i tidskrift (Övrigt vetenskapligt)
  • 27.
    Ericsson, Göran
    et al.
    SLU, Umeå.
    Larsson, Thomas B
    Umeå universitet, Institutionen för idé- och samhällsstudier.
    Rosqvist, Gunhild
    Stockholms universitet.
    Jonasson, Christer
    Polarforskningssekretariatet.
    Älgen flyr när klimatet ändras2011Ingår i: Miljötrender, ISSN 1403-4743, nr 4, s. 12-13Artikel i tidskrift (Övrigt vetenskapligt)
  • 28.
    Eriksson, Bert
    Uppsala universitet, Kulturgeografiska institutionen.
    The zoo-geomorphological impact of fossorial rodents in sub-polar alpine environments2011Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The geomorphological impact of small fossorial mammals (adapted to digging and living underground), such as rodents can be significant, and both their direct and indirect effects may contribute to landscape formation. This thesis is based on empirical field studies of two burrowing rodent species in sub-polar environments, namely invasive House mice (Mus musculus) on sub-Antarctic Marion Island and Norwegian lemmings (Lemmus lemmus) in sub-Arctic Abisko. The spatial distribution, sediment displacements, impact on vegetation and microclimatic effects of the rodents are documented.

    Invasive mice and rats, introduced on sub-Antarctic Islands during the 19th century, lack natural enemies and are shown to have a significant direct and indirect geomorphic impact by direct sediment displacement, vegetation removal by burrowing, grazing and trampling and thereby exposing the sediments for rain, wind and frost processes.  The geomorphic impacts of lemmings are comparatively more limited as they rely on natural hollows and snow cover for protection and do not burrow to the same extent as other fossorial rodents in cold regions. Lemmings are thus suggested to have little impact on landform integrity, but can affect vegetation composition.

    A comparison of the findings from this study with published data on seven other rodent species and other physical mass transfer mechanisms in sub-polar and alpine environments suggests that fossorial rodents are a significant and sometimes dominant geomorphic force in sub-polar and alpine environments. The geomorphic work by ground squirrels, ice rats, plateau pikas and zokors is shown to be in the same order of magnitude as solifluction and rock falls. In alpine and periglacial environments these rodents are considered to act as key-stone species and ecosystem engineers through the creation of landforms by  dislocation and of soil and other impacts on soil properties, vegetation and ecosystem function

  • 29.
    Fredin, Ola
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Mountain centered icefields in northern Scandinavia2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Mountain centered glaciers have played a major role throughout the last three million years in the Scandinavian mountains. The climatic extremes, like the present warm interglacial or cold glacial maxima, are very short-lived compared to the periods of intermediate climate conditions, characterized by the persistence of mountain based glaciers and ice fields of regional size. These have persisted in the Scandinavian mountains for about 65% of the Quaternary. Mountain based glaciers thus had a profound impact on large-scale geomorphology, which is manifested in large-scale glacial landforms such as fjords, glacial lakes and U-shaped valleys in and close to the mountain range.

    Through a mapping of glacial landforms in the northern Scandinavian mountain range, in particular a striking set of lateral moraines, this thesis offers new insights into Weichselian stages predating the last glacial maximum. The aerial photograph mapping and field evidence yield evidence that these lateral moraines were overridden by glacier ice subsequent to their formation. The lateral moraines were dated using terrestrial cosmogenic nuclide techniques. Although the terrestrial cosmogenic nuclide signature of the moraines is inconclusive, an early Weichselian age is tentatively suggested through correlations with other landforms and stratigraphical archives in the region. The abundance and coherent spatial pattern of the lateral moraines also allow a spatial reconstruction of this ice field. The ice field was controlled by topography and had nunataks protruding also where it was thickest close to the elevation axis of the Scandinavian mountain range. Outlet glaciers discharged into the Norwegian fjords and major valleys in Sweden.

    The process by which mountain based glaciers grow into an ice sheet is a matter of debate. In this thesis, a feedback mechanism between debris on the ice surface and ice sheet growth is presented. In essence, the growth of glaciers and ice sheets may be accelerated by an abundance of debris in their ablation areas. This may occur when the debris cover on the glacier surface inhibits ablation, effectively increasing the glaciers mass balance. It is thus possible that a dirty ablation area may cause the glacier to advance further than a clean glacier under similar conditions. An ice free period of significant length allows soil production through weathering, frost shattering, and slope processes. As glaciers advance through this assemblage of sediments, significant amounts of debris end up on the surface due to both mass wastage and subglacial entrainment. Evidence that this chain of events may occur, is given by large expanses of hummocky moraine (local name Veiki moraine) in the northern Swedish lowlands. Because the Veiki moraine has been correlated with the first Weichselian advance following the Eemian, it implies a heavily debris charged ice sheet emanating from the mountain range and terminating in a stagnant fashion in the lowlands.

  • 30.
    Förster, Johannes
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Metabolic balance and CO2 saturation in a subarctic permafrost lake2005Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 31. Giesler, Reiner
    et al.
    Lyon, Steve W.
    Stockholms universitet, Institutionen för naturgeografi.
    Mörth, Carl-Magnus
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Karlsson, Jan
    Karlsson, E. M.
    Jantze, Elin J.
    Stockholms universitet, Institutionen för naturgeografi.
    Destouni, Georgia
    Stockholms universitet, Institutionen för naturgeografi.
    Humborg, Christoph
    Stockholms universitet, Institutionen för tillämpad miljövetenskap (ITM).
    Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden2014Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, s. 525-537Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climatic change is currently enhancing permafrostthawing and the flow of water through the landscape in subarcticand arctic catchments, with major consequences forthe carbon export to aquatic ecosystems. We studied streamwater carbon export in several tundra-dominated catchmentsin northern Sweden. There were clear seasonal differencesin both dissolved organic carbon (DOC) and dissolved inorganiccarbon (DIC) concentrations. The highest DOC concentrationsoccurred during the spring freshet while the highestDIC concentrations were always observed during winterbaseflow conditions for the six catchments considered in thisstudy. Long-term trends for the period 1982 to 2010 for oneof the streams showed that DIC concentrations has increasedby 9% during the 28 yr of measurement while no clear trendwas found for DOC. Similar increasing trends were alsofound for conductivity, Ca and Mg. When trends were discretizedinto individual months, we found a significant linearincrease in DIC concentrations with time for September,November and December. In these subarctic catchments, theannual mass of C exported as DIC was in the same orderof magnitude as DOC; the average proportion of DIC to thetotal dissolved C exported was 61% for the six streams. Furthermore,there was a direct relationship between total runoffand annual dissolved carbon fluxes for these six catchments.These relationships were more prevalent for annual DIC exportsthan annual DOC exports in this region. Our results alsohighlight that both DOC and DIC can be important in highlatitudeecosystems. This is particularly relevant in environmentswhere thawing permafrost and changes to subsurfaceice due to global warming can influence stream water fluxesof C. The large proportion of stream water DIC flux also hasimplications on regional C budgets and needs to be consideredin order to understand climate-induced feedback mechanismsacross the landscape.

  • 32.
    Granath, Gustaf
    et al.
    Uppsala universitet, Växtekologi och evolution.
    Rydin, Håkan
    Uppsala universitet, Växtekologi och evolution.
    Baltzer, Jennifer L.
    Biology Department, Wilfrid Laurier University, Waterloo, Canada.
    Bengtsson, Fia
    Uppsala universitet, Växtekologi och evolution.
    Boncek, Nicholas
    Department of Biological Sciences, Union College, Schenectady, NY, USA.
    Bragazza, Luca
    Department of Life Science and Biotechnologies, University of Ferrara, Ferrara, Italy; Swiss Federal Institute for Forest, Snow and Landscape Research, WSL Site Lausanne, Station 2, Lausanne, Switzerland; Ecole Polytechnique Fédérale de Lausanne EPFL, School of Architecture, Civil and Environmental Engineering ENAC, Laboratory of ecological systems ECOS, Station 2, Lausanne, Switzerland.
    Bu, Zhao-Jun
    Institute for Peat and Mire Research, Northeast Normal University, State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, Changchun, China; Jilin Provincial Key Laboratory for Wetland Ecological Processes and Environmental Change in the Changbai Mountains, Changchun, China.
    Caporn, Simon J. M.
    School of Science and the Environment, Division of Biology and Conservation Ecology, Manchester Metropolitan University, Manchester, UK.
    Dorrepaal, Ellen
    Climate Impacts Research Centre, Dept. of Ecology and Environmental Science, Umeå University, Abisko, Sweden.
    Galanina, Olga
    Institute of Earth Sciences, St. Petersburg State University, St. Petersburg, Russia; Komarov Botanical Institute Russian Academy of Sciences, St. Petersburg, Russia.
    Galka, Mariusz
    Laboratory of Wetland Ecology and Monitoring & Department of Biogeography and Paleoecology, Adam Mickiewicz University in Poznan, Poznan, Polen.
    Ganeva, Anna
    Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria.
    Gillikin, David P.
    Department of Geology, Union College, Schenectady, NY, USA.
    Goia, Irina
    Babe ̧s-Bolyai University, Faculty of Biology and Geology, Department of Taxonomy and Ecology, Cluj Napoca, Romania.
    Goncharova, Nadezhda
    Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Science, Syktyvkar, Russia.
    Hajek, Michal
    Masaryk Univ, Fac Sci, Dept Bot & Zool, Brno, Czech Republic.
    Haraguchi, Akira
    Univ Kitakyushu, Dept Biol, Kitakyushu, Fukuoka, Japan.
    Harris, Lorna I.
    McGill Univ, Dept Geog, Montreal, Canada.
    Humphreys, Elyn
    Carleton Univ, Dept Geog & Environm Studies, Ottawa, Canada.
    Jirousek, Martin
    Masaryk Univ, Fac Sci, Dept Bot & Zool, Brno, Czech Republic; Mendel Univ Brno, Fac AgriSci, Dept Plant Biol, Brno, Czech Republic.
    Kajukalo, Katarzyna
    Adam Mickiewicz Univ, Lab Wetland Ecol & Monitoring, Poznan, Poland; Adam Mickiewicz Univ, Dept Biogeog & Paleoecol, Poznan, Poland.
    Karofeld, Edgar
    Univ Tartu, Inst Ecol & Earth Sci, Tartu, Estonia.
    Koronatova, Natalia G.
    Russian Acad Sci, Siberian Branch, Inst Soil Sci & Agrochem, Lab Biogeocenol, Novosibirsk, Russia.
    Kosykh, Natalia P.
    Russian Acad Sci, Siberian Branch, Inst Soil Sci & Agrochem, Lab Biogeocenol, Novosibirsk, Russia.
    Lamentowicz, Mariusz
    Adam Mickiewicz Univ, Lab Wetland Ecol & Monitoring, Poznan, Poland; Adam Mickiewicz Univ, Dept Biogeog & Paleoecol, Poznan, Poland.
    Lapshina, Elena
    Yugra State Univ, Khanty Mansiysk, Russia.
    Limpens, Juul
    Wageningen Univ, Plant Ecol & Nat Conservat Grp, Wageningen, Netherlands.
    Linkosalmi, Maiju
    Finnish Meteorol Inst, Helsinki, Finland.
    Ma, Jin-Ze
    Northeast Normal Univ, State Environm Protect Key Lab Wetland Ecol & Veg, Inst Peat & Mire Res, Changchun, Jilin, Peoples R China; Jilin Prov Key Lab Wetland Ecol Proc & Environm C, Changchun, Jilin, Peoples R China.
    Mauritz, Marguerite
    No Arizona Univ, Dept Biol Sci, Ctr Ecosyst Sci & Soc Ecoss, Flagstaff, USA.
    Munir, Tariq M.
    Univ Calgary, Dept Geog, Calgary, Canada; St Marys Univ, Dept Geol, Calgary, Canada.
    Natali, Susan M.
    Woods Hole Res Ctr, Falmouth, USA.
    Natcheva, Rayna
    Bulgarian Acad Sci, Inst Biodivers & Ecosyst Res, Sofia, Bulgaria.
    Noskova, Maria
    Russian Acad Sci, Komarov Bot Inst, St Petersburg, Russia.
    Payne, Richard J.
    Univ York, Environm, York, N Yorkshire, England; Penza State Univ, Penza, Russia.
    Pilkington, Kyle
    Union Coll, Dept Biol Sci, Schenectady, NY USA.
    Robinson, Sean
    SUNY Coll Oneonta, Dept Biol, Oneonta, NY USA.
    Robroek, Bjorn J. M.
    Univ Southampton, Biol Sci, Southampton, Hants, England.
    Rochefort, Line
    Laval Univ, Dept Plant Sci, Quebec City, PQ, Canada; Laval Univ, Ctr Northern Studies, Quebec City, PQ, Canada.
    Singer, David
    Univ Neuchatel, Inst Biol, Lab Soil Biodivers, Neuchatel, Switzerland; Univ Sao Paulo, Inst Biosci, Dept Zool, Sao Paulo, Brazil.
    Stenoien, Hans K.
    Norwegian Univ Sci & Technol, NTNU Univ Museum, Trondheim, Norway.
    Tuittila, Eeva-Stiina
    Univ Eastern Finland, Sch Forest Sci, Peatland & Soil Ecol Grp, Joensuu, Finland.
    Vellak, Kai
    Univ Tartu, Inst Ecol & Earth Sci, Tartu, Estonia.
    Verheyden, Anouk
    Union Coll, Dept Geol, Schenectady, NY USA.
    Waddington, James Michael
    McMaster Univ, Sch Geog & Earth Sci, Hamilton, Canada.
    Rice, Steven K.
    Union Coll, Dept Biol Sci, Schenectady, NY USA.
    Environmental and taxonomic controls of carbon and oxygen stable isotope composition in Sphagnum across broad climatic and geographic ranges2018Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 16, s. 5189-5202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on nutrients, water and CO2 uptake from the atmosphere. As the isotopic composition of carbon (C-12(,)13) and oxygen (O-16(,)18) of these Sphagnum mosses are affected by environmental conditions, Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is inadequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is speciesspecific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation) and elevation; (ii) whether the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue delta O-18 tracks the delta O-18 isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia us ing two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holarctic realm. There were differences in delta C-13 values between species. For S. magellanicum delta C-13 decreased with increasing height above the water table (HWT, R-2 = 17 %) and was positively correlated to productivity (R-2 = 7 %). Together these two variables explained 46 % of the between-site variation in delta C-13 values. For S. fuscum, productivity was the only significant predictor of delta C-13 but had low explanatory power (total R-2 = 6 %). For delta O-18 values, approximately 90 % of the variation was found between sites. Globally modelled annual delta O-18 values in precipitation explained 69 % of the between-site variation in tissue delta O-18. S. magellanicum showed lower delta O-18 enrichment than S. fuscum (-0.83 %0 lower). Elevation and climatic variables were weak predictors of tissue delta O-18 values after controlling for delta O-18 values of the precipitation. To summarize, our study provides evidence for (a) good predictability of tissue delta O-18 values from modelled annual delta O-18 values in precipitation, and (b) the possibility of relating tissue delta C-13 values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used on a large scale for climatic reconstructions but that such models should be species-specific.

  • 33.
    Grudd, Håkan
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Tree Rings as Sensitive Proxies of Past Climate Change2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the boreal forests of the Northern Hemisphere, time series of tree-ring width (TRW) and maximum density in the latewood (MXD) are highly correlated to local instrumental summer-temperature data and are thus widely used as proxies in high-resolution climate reconstructions. Hence, much of our present knowledge about climatic variability in the last millennium is based on tree-rings. However, many tree-ring records have a lack of data in the most recent decades, which severely hampers our ability to place the recent temperature increase in a longer-timescale perspective of natural variability.

    The main objective of this thesis is to update and extend the Torneträsk TRW and MXD records in northern Sweden. Local instrumental climate-data is used to calibrate the new tree-ring records. The results show that TRW is mainly forced by temperature in the early growing season (June/July) while MXD has a wider response window (June – August) and has a higher correlation to temperature. Two reconstructions of summer temperature are made for (i) the last 7,400 years based on TRW, and (ii) the last 1,500 years based on a combination of TRW and MXD. The reconstructions show natural variability on timescales from years to several centuries. The 20th century does not stand out as a notably warm period in the long timescale perspective. A medieval period from AD 900 – 1100 is markedly warmer than the 20th century.

    The environmental impact from a large explosive volcanic eruption in 1628/1627 BC is analysed in the tree rings of 14C-dated bog pines in south-central Sweden and in absolutely-dated subfossil pines from Torneträsk. The results show evidence of an impact in the southern site at approximately this time but no detectable impact in the North.

    Subfossil trees of Fitzroya cupressoides in southern Chile were 14C-dated to approx. 50,000 years BP and amalgamated into a 1,229-year TRW chronology. This tree-ring record is the oldest in the world. The variability in this Last-glacial chronology is similar to the variability in present-day living trees of the same species. These results suggest that the growth–forcing mechanisms 50,000 years ago were similar to those at present.

  • 34.
    Hein, Catherine L.
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Öhlund, Gunnar
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Englund, Göran
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Fish introductions reveal the temperature dependence of species interactions2014Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, nr 1775, s. 20132641-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major area of current research is to understand how climate change will impact species interactions and ultimately biodiversity. A variety of environmental conditions are rapidly changing owing to climate warming, and these conditions often affect both the strength and outcome of species interactions. We used fish distributions and replicated fish introductions to investigate environmental conditions influencing the coexistence of two fishes in Swedish lakes: brown trout (Salmo trutta) and pike (Esox lucius). A logistic regression model of brown trout and pike coexistence showed that these species coexist in large lakes (more than 4.5 km(2)), but not in small, warm lakes (annual air temperature more than 0.9-1.5 degrees C). We then explored how climate change will alter coexistence by substituting climate scenarios for 2091-2100 into our model. The model predicts that brown trout will be extirpated from approximately half of the lakes where they presently coexist with pike and from nearly all 9100 lakes where pike are predicted to invade. Context dependency was critical for understanding pike-brown trout interactions, and, given the widespread occurrence of context-dependent species interactions, this aspect will probably be critical for accurately predicting climate impacts on biodiversity.

  • 35. Hines, Keith M.
    et al.
    Bromwich, David H.
    Simulation of Late Summer Arctic Clouds during ASCOS with Polar WRF2017Ingår i: Monthly Weather Review, ISSN 0027-0644, E-ISSN 1520-0493, Vol. 145, nr 2, s. 521-541Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-level clouds are extensive in the Arctic and contribute to inadequately understood feedbacks within the changing regional climate. The simulation of low-level clouds, including mixed-phase clouds, over the Arctic Ocean during summer and autumn remains a challenge for both real-time weather forecasts and climate models. Here, improved cloud representations are sought with high-resolution mesoscale simulations of the August-September 2008 Arctic Summer Cloud Ocean Study (ASCOS) with the latest polar-optimized version (3.7.1) of the Weather Research and Forecasting (Polar WRF) Model with the advanced two-moment Morrison microphysics scheme. Simulations across several synoptic regimes for 10 August-3 September 2008 are performed with three domains including an outer domain at 27-km grid spacing and nested domains at 9- and 3-km spacing. These are realistic horizontal grid spacings for common mesoscale applications. The control simulation produces excessive cloud liquid water in low clouds resulting in a large deficit in modeled incident shortwave radiation at the surface. Incident longwave radiation is less sensitive. A change in the sea ice albedo toward the larger observed values during ASCOS resulted in somewhat more realistic simulations. More importantly, sensitivity tests show that a reduction in specified liquid cloud droplet number to very pristine conditions increases liquid precipitation, greatly reduces the excess in simulated low-level cloud liquid water, and improves the simulated incident shortwave and longwave radiation at the surface.

  • 36. JADWISZCZAK, Piotr
    et al.
    Mörs, Thomas
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    First report on quill pits in early penguins2016Ingår i: Antarctic Science, ISSN 0954-1020, E-ISSN 1365-2079Artikel i tidskrift (Refereegranskat)
  • 37.
    Jantunen, Liisa
    et al.
    Environment Canada, Canada.
    Wong, Fiona
    Stockholm University.
    Gawor, Anya
    Environment Canada.
    Kylin, Henrik
    Linköpings universitet, Tema Miljöförändring.
    Helm, Paul
    Ontario Ministry of the Environment, Canada.
    Stern, Gary
    University of Manitoba, Canada.
    Strachan, William
    Environment Canada, Canada.
    Burniston, Deborah
    Environment Canada, Canada.
    Bidleman, Terry
    Umeå University.
    20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean2015Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, nr 23, s. 13844-13852Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air−water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water−air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air−surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals.

  • 38.
    Jantze, Elin
    Stockholms universitet, Institutionen för naturgeografi.
    Waterborne Carbon in Northern Streams: Controls on dissolved carbon transport across sub-arctic Scandinavia2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams.

  • 39.
    Jantze, Elin J.
    et al.
    Stockholms universitet, Institutionen för naturgeografi.
    Laudon, Hjalmar
    Dahlke, Helen E.
    Lyon, Steve W.
    Stockholms universitet, Institutionen för naturgeografi.
    Spatial Variability of Dissolved Organic and Inorganic Carbon in Subarctic Headwater Streams2015Ingår i: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, nr 3, s. 529-546Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The subarctic landscape is composed of a complex mosaic of vegetation, geology and topography, which control both the hydrology and biogeochemistry of streams across space and time. We present a synoptic sampling campaign that aimed to estimate dissolved C export variability under low-flow conditions from a subarctic landscape. The results included measurements of stream discharge and concentrations of both dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2) for 32 subcatchments of the Abiskojokka catchment in northern Sweden. For these subarctic headwater streams, we found that DOC, DIC and CO2 concentrations showed significant variability (p < 0.05) relative to catchment size, discharge, specific discharge, lithology, electrical conductivity, weathering products, and the estimated travel time of water through the subcatchment. Our results indicate that neither vegetation cover nor lithology alone could explain the concentrations and mass flux rates of DOC and DIC. Instead, we found that mass flux rates of DOC, DIC, and CO2 depended mainly on specific discharge and water travel time. Furthermore, our results demonstrate the importance of studying lateral carbon transport in combination with hydrological flow paths at small scales to establish a knowledge foundation applicable for expected carbon cycle and hydroclimatic shifts due to climate change.

  • 40.
    Jantze, Elin J.
    et al.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Lyon, Steve W.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Destouni, Georgia
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Subsurface release and transport of dissolved carbon in a discontinuous permafrost region2013Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, nr 10, s. 3827-3839Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Subsurface hydrological flow pathways and advection rates through the landscape affect the quantity and timing of hydrological transport of dissolved carbon. This study investigates hydrological carbon transport through the subsurface to streams and how it is affected by the distribution of subsurface hydrological pathways and travel times through the landscape. We develop a consistent mechanistic, pathway- and travel time-based modeling approach for release and transport of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The model implications are tested against observations in the subarctic Abiskojokken catchment in northernmost Sweden (68 degrees 21'N, 18 degrees 49'E) as a field case example of a discontinuous permafrost region. The results show: (a) For DOC, both concentration and load are essentially flow-independent because their dynamics are instead dominated by the annual renewal and depletion. Specifically, the flow independence is the result of the small characteristic DOC respiration-dissolution time scale, in the range of 1 yr, relative to the average travel time of water through the subsurface to the stream. (b) For DIC, the load is highly flow-dependent due to the large characteristic weathering-dissolution time, much larger than 1 yr, relative to the average subsurface water travel time to the stream. This rate relation keeps the DIC concentration essentially flow-independent, and thereby less fluctuating in time than the DIC load.

  • 41. Jelinski, Nicolas A.
    et al.
    Yoo, Kyungsoo
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Utilising a suite of isotopic and elemental tracers to constrain cryoturbation rates and patterns in a non-sorted circle2017Ingår i: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 28, nr 4, s. 634-648Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The empirical quantification of rates of material movement in cryoturbated soils has lagged behind the physical and chemical characterisation of these materials. We applied a novel suite of elemental (C, Hg), stable isotope (C-13) and radioisotope (Cs-137, Pb-210, C-14, Be-10) tracers in conjunction with analytical and numerical models to constrain the rates and patterns of soil movement due to cryoturbation in a non-sorted circle (NSC) near Abisko, Sweden. We present the first observations of the variability of Be-10 across a patterned-ground feature, which facilitate the interpretation of subsurface peaks in soil organic carbon, Hg and C-13 and provide constraints on the surficial histories of cryoturbated materials. Apparent rates of surficial lateral movement across the NSC estimated from Cs-137 and Pb-210 (0-2.55cm year(-1)) decreased with distance from its centre and were an order of magnitude greater than rates of subduction and subsurface movement estimated from C-14 (0.04-0.27cm year(-1)). Novel estimates of the original surficial residence times of cryoturbated parcels based on excess Be-10 and Hg inventories ranged from 238 to 3940years. Our results demonstrate the utility of the spatially explicit application of elemental and radioisotopic tracer suites to constrain cryoturbation rates in Arctic patterned ground.

  • 42. Johansson, Cecilia
    et al.
    Ingvander, Susanne
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    A model for the snow water equivalent derived from stratigraphy observations in northern Sweden2015Ingår i: Hydrology Research, ISSN 1998-9563, E-ISSN 2224-7955, Vol. 46, nr 6, s. 984-995Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new parameterization of snow water equivalent (SWE) based on snow depth (HS) has been developed from observations made in northern Sweden. When applying previous SWE parameterization from the Alps on observations from northern Sweden, the SWE values are systematically 20% lower. The new SWE parameterization is derived from a snow layer density regression model using snow layer hardness and snow particle size. The model was evaluated with a detailed field reference dataset, and then applied to the long-term Abisko Scientific Research Station stratigraphic snowpack dataset The model enables a regional adjustment of snow layer density values for northern Swedish conditions. The snow layer density model provides an accurate estimation of snow bulk density used to derive the SWE parameterization based solely on HS. Snow depth observations are made on a daily basis; by applying our new parameterization, daily values of SWE can be obtained for northern Scandinavian conditions, which can be used, for example, for hydropower production planning and risk assessments.

  • 43.
    Jonsson, Christina E.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Holocene climate and atmospheric circulation changes in northern Fennoscandia: Interpretations from lacustrine oxygen isotope records2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region.

  • 44.
    Jonsson, Christina E.
    et al.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Leng, Melanie J.
    NERC Isotope Geosciences Laboratory , BGS, UK.
    Rosqvist, Gunhild C.
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Seibert, Jan
    Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK).
    Arrowsmith, Carol
    NERC Isotope Geosciences Laboratory, BGS, UK.
    Stable oxygen and hydrogen isotopes in sub-Arctic lake wateras from northern Sweden2009Ingår i: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 376, s. 143-151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lakes in sub-Arctic regions have the potential of retaining many different aspects of water isotope composition in their sediments which can be used for palaeoclimate reconstruction. It is therefore important to understand the modern isotope hydrology of these lakes. Here we discuss the significance of variations in water isotope composition of a series of lakes located in north-west Swedish Lapland. Climate in this region is forced by changes in the North Atlantic which renders it an interesting area for climate reconstructions. We compare δ18Olake and δ2Hlake collected between 2001 and 2006 and show that the lakes in this sub-Arctic region are currently mainly recharged by shallow groundwater and precipitation which undergoes little subsequent evaporation, and that the d18O and δ2H composition of input to the majority of the lakes varies on a seasonal basis between winter precipitation (and spring thaw) and summer precipitation. Seasonal variations in the isotopic composition of the lake waters are larger in lakes with short residence times (<6 months), which react faster to seasonal changes in the precipitation, compared to lakes with longer residence times (>6 months), which retain an isotopic signal closer to that of annual mean precipitation. Lake waters also show a range of isotope values between sites due to catchment elevation and timing of snow melt. The lake water data collected in this study was supported by isotope data from lake waters, streams and ground waters from1995 to 2000 reported in other studies.

  • 45.
    Kassel, Marlene
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Effects of climate change on freezing damage in three subarctic bryophyte species2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Climate change is expected to have a strong impact on subarctic ecosystems. Increased temperatures as well as altered precipitation and snow cover patterns are predicted to change species distribution and affect biogeochemical processes in the subarctic tundra. Bryophytes are an essential vegetational component in northern ecosystems, due to their high abundance and importance in many ecological processes. In this study the effects of elevation and altered snow cover on the temporal dynamics of freezing damage in three subarctic bryophyte species (Hylocomium splendens, Ptilidium ciliare, and Sphagnum fuscum) were studied in a snow manipulation field experiment in Abisko, during early spring. Soil temperature and field moisture of moss shoots were collected. A freeze-thaw incubation experiment was conducted to investigate the freeze-thaw cycle resistance of H. splendens and P. ciliare originating from habitats with two differing snow-cover thicknesses. Freezing damage differed significantly between the bryophytes species with P. ciliare experiencing the least and S. fuscum the highest damage. Damage was higher at the low elevation, possibly attributable to acclimation effects. Snow removal led to higher damage in moss shoots, but no interactions of the different snow cover treatments with elevation, species or time were found. Freezing damage increased over time and no recovery occurred, likely due to temporal patterns in soil freeze-thaw cycles during early spring. Soil freeze-thaw cycles were the main factor influencing damage in bryophytes after snow melt. Measured environmental parameters could not explain the entire variation in damage. Damage might additionally be attributable to increased UV radiation or disturbances by herbivores.

  • 46.
    Krohn, Johannes
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Phosphorus speciation across elevation and vegetation in soils of the subarctic tundra: A solution 31P NMR approach2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In tundra, phosphorus (P) is an important macronutrient for plants and microorganisms. A major fraction of P exists as organic compounds in the topsoil which can be mineralized to bioavailable inorganic P. Since mineralization is positively related to temperature, climate warming is likely to increase P bioavailability but the extend of these changes may also depend on vegetation cover and soil properties. I assessed organic and inorganic P concentrations across an elevation and vegetation gradient in northern Sweden using one dimensional (1D) solution 31P nuclear magnetic resonance spectroscopy. I hypothesized that concentration of labile soil P will decrease with increasing elevation (decreasing temperature) and that soils with meadow vegetation will contain higher concentrations of labile P than heath soils. Concentration of labile P in the form of Resin-P and polyphosphates decreased with elevation whereas less labile orthophosphate monoesters increased. Across vegetation types, polyphosphates were more abundant in heath and meadow contained higher concentrations of monoesters. The inverse response of Resin-P and monoesters to elevation may be best explained by lowered organic P mineralization in colder climate. High concentrations of polyphosphates at the lowest elevation may indicate an increased presence of fungal communities associated with mountain birch forest. Heath seemed to be more dominated by fungal communities than meadow and higher concentration of monoesters in meadow indicated a higher soil sorption capacity. In a broader view, the results may suggest that a warmer climate increases mineralization of organic P in form of orthophosphate monoesters to more labile P forms. This effect might be enhanced by an upward movement of the tree line and might be more pronounced in heath than meadow soils due to a higher fungal activity.

  • 47.
    Kuhn, McKenzie
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Lundin, Erik J
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Giesler, Reiner
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Johansson, Margareta
    Karlsson, Jan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 9535Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Northern regions have received considerable attention not only because the effects of climate change are amplified at high latitudes but also because this region holds vast amounts of carbon (C) stored in permafrost. These carbon stocks are vulnerable to warming temperatures and increased permafrost thaw and the breakdown and release of soil C in the form of carbon dioxide (CO2) and methane (CH4). The majority of research has focused on quantifying and upscaling the effects of thaw on CO2 and CH4 emissions from terrestrial systems. However, small ponds formed in permafrost wetlands following thawing have been recognized as hotspots for C emissions. Here, we examined the importance of small ponds for C fluxes in two permafrost wetland ecosystems in northern Sweden. Detailed flux estimates of thaw ponds during the growing season show that ponds emit, on average (±SD), 279 ± 415 and 7 ± 11 mmol C m−2 d−1 of CO2 and CH4, respectively. Importantly, addition of pond emissions to the total C budget of the wetland decreases the C sink by ~39%. Our results emphasize the need for integrated research linking C cycling on land and in water in order to make correct assessments of contemporary C balances.

  • 48. Kylin, Hanna
    Ekoturismens natur- och miljöpåverkan i polarområden2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 49. Lindblad, K.E.M.
    et al.
    Nyberg, Rolf
    Karlstads universitet, Avdelningen för geografi och turism.
    Molau, U.
    Generalization of heterogeneous alpine vegetation in air photo-based image classification, Latnjajaure catchment, northern Sweden2006Ingår i: Pirineos: Revista de Ecología de Montaña, ISSN 0373-2568, E-ISSN 1988-4281, Vol. 161, nr 3a32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mapping alpine vegetation at a meso-scale (catchment level) using remote sensing presents difficulties due to a patchy distribution and heteregeneous spectral appearance of the plant cover. We discuss issues of generalization and accuracy assessment in this case study when using a digital CIR air photo for an automatic classification of the dominant plant communities. About 10 plant communities could be classified with acceptable accuracy where the chosen classification scheme determined the final outcome. If a high resolution pixel mosaic is generalized to units that match the positional accuracy of simple GPS this generalization may also influence the information content of the image

  • 50.
    Lindeberg, Carola
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Long-term changes of mercury, lead and persistent organic pollutants in arctic environments2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Arctic represents a huge area with poor infrastructure contributing to limited possibilities to establish monitoring and research programs. From the investigations that have been performed we know that the arctic environment is affected by anthropogenic emissions from lower latitudes, but knowledge about underlying transport processes, the arctic pollution extent and the rates of changes are limited. This is of particular concern since we are facing climate changes that will not only influence the pole-ward transport of pollutants, but also change conditions for the already accumulated pollutants in the arctic environment.

    In this thesis lake sediments and soil samples are used to study sub-arctic and arctic time trends and loads of PCBs, PBDE, pesticides, mercury and lead. The study sites are the area around Kangerlussuaq, located in western Greenland, and the Swedish mountains. The temporal trends for PCBs (69 congeners), PBDE (#47) and two pesticides (chlordane and hexachlorobenzene) are studied in seven surface lake sediment cores from Greenland. The concentrations of these persistent organic pollutants are one to two orders of magnitude lower compared to lake sediments from lower latitudes, but with temporal trends following emission and usage trends at lower altitudes, i.e., decreasing trends for PCBs, increasing for PBDE and no specific trends for the pesticides. A delayed deposition of the low-chlorinated PCBs compared to the high-chlorinated PCBs may support the hypothesis of ‘cold condensation’ and ‘global fractionation’ i.e., volatile compounds are fractionated during the pole-ward transport. For lead the concentration in three Greenland lake sediments is about 10 times lower than in sediments from industrial regions, but the past 200 years’ temporal trends follow emission trends in industrial regions. The mercury concentration and enrichment following the Industrial Revolution in the mid 19th century are in three lake sediments from Greenland and in twelve lake sediments from the Swedish mountains comparable with those in sediments from industrial regions; a result of the long atmospheric residence-time for mercury, making it a global pollution. Recently decreased mercury emissions in North America and Europe give declining concentrations in the sediment surfaces, especially in lakes located in the Swedish mountains. In Greenland deeper sediment cores, spanning the last 8000 years, there are substantial fluctuations in mercury concentration and stable lead isotopes (206Pb/207Pb). These fluctuations are the result of variations in deposition to the lake of aeolian material, driven by past variations in arctic climate. In surface soil the mercury concentrations and inventories from the Swedish mountains are 1.5-2 times higher than in soils from Greenland, but for both regions the concentrations are below the critical concentration set up by UN-ECE to protect the terrestrial ecosystem. No indications for mercury enrichment in colder areas, as suggested by the hypothesis of ‘cold condensation’, or in coastal areas, as suggested by the hypothesis of ‘mercury depletion events’, were observed. The highly minerogenic surface soils in sub-arctic and arctic regions have reduced capacity to store mercury, compared to boreal soils.

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