The sedimentary ancient DNA (sedaDNA) technique offers a potentially invaluable means of investigating species evolution and extinction dynamics in high-latitude environments. An implicit assumption of the sedaDNA approach is that the extracted DNA is autochthonous with the host deposit and that it has not been physically transported from older source deposits or reworked within the sedimentary profile by postdepositional mixing. In this paper we investigate whether these fundamental conditions are upheld at seven perennially frozen wetland sites across the Taimyr Peninsula and coastal lowlands of north-central Siberia. Optically stimulated luminescence (OSL) and radiocarbon (C-14) dating are used to constrain the ages of both the inorganic and organic fractions of perennially frozen deposits from which sedaDNA of extinct and extant species have been recovered. OSL and C-14 age/depth profiles, as well as single-grain equivalent dose (De) distribution characteristics, are used to assess the stratigraphic integrity of these sedaDNA sequences by (i) identifying the presence of primary or reworked organic and inorganic material, and (ii) examining the types of depositional and postdepositional processes that have affected specific sedimentary facies. The results of this study demonstrate that even though DNA preservation and stratigraphic integrity are commonly superior in perennially frozen settings, this does not, in itself, guarantee the suitability of the sedaDNA approach. The combined OSL and C-14 chronologies reveal that certain perennially frozen sites may be poorly suited for sedaDNA analysis, and that careful site selection is paramount to ensuring the accuracy of any sedaDNA study - particularly for 'latest appearance date' estimates of extinct taxa.

Chironomids, pollen and spores were used to reconstruct Holocene aquatic and terrestrial environments at Alanen Laanijarvi, northern Sweden. Chironomid analysis revealed a pattern of limnological evolution from oligotrophic conditions in a relatively deep lake during 8.6 to 5.5 cal. ka BP, followed by a period of lake shallowing from 5.5 to 2.7 cal. ka BP. Increases in acidity and littoral habitat complexity may have occurred from 2.7 cal. ka BP to the present, though some compositional changes may have resulted from human disturbance. Chironomid-inferred mean July air temperatures range between 9.8 degrees C in the Early Holocene to 11.3 degrees C in the Late Holocene. Limitations on chironomid-based quantitative temperature interpretations may exist because of low taxon richness. Diatoms were recovered from the upper sediments only, from about AD 1800. Pollen and spore analysis revealed an early colonizing vegetation of juniper, sedges and birch soon after local deglaciation, followed by birch forests until about 8.3 cal. ka BP. Alder stands occurred locally to 5.5 cal. ka BP, when pine and spruce forests developed and remain to the present day. These results suggest that little major terrestrial vegetation change may occur in some northern environments with predicted future global warming, where it is predicted to be most severe. Aquatic environments may, however, be greatly affected by a shift in precipitation regime, causing changes in allochthonous organic input, lake depth and possibly the amount of human activity or disturbance in the watershed.

Using glacial rebound models we have inverted observations of crustal rebound and shoreline locations to estimate the ice thickness for the major glaciations over northern Eurasia and to predict the palaeo-topography from late MIS-6 ( the Late Saalian at c. 140 kyr BP) to MIS-4e ( early Middle Weichselian at c. 64 kyr BP). During the Late Saalian, the ice extended across northern Europe and Russia with a broad dome centred from the Kara Sea to Karelia that reached a maximum thickness of c. 4500 m and ice surface elevation of c. 3500 m above sea level. A secondary dome occurred over Finland with ice thickness and surface elevation of 4000 m and 3000 m, respectively. When ice retreat commenced, and before the onset of the warm phase of the early Eemian, extensive marine flooding occurred from the Atlantic to the Urals and, once the ice retreated from the Urals, to the Taymyr Peninsula. The Baltic - White Sea connection is predicted to have closed at about 129 kyr BP, although large areas of arctic Russia remained submerged until the end of the Eemian. During the stadials (MIS-5d, 5b, 4) the maximum ice was centred over the Kara - Barents Seas with a thickness not exceeding c. 1200 m. Ice-dammed lakes and the elevations of sills are predicted for the major glacial phases and used to test the ice models. Large lakes are predicted for west Siberia at the end of the Saalian and during MIS-5d, 5b and 4, with the lake levels, margin locations and outlets depending inter alia on ice thickness and isostatic adjustment. During the Saalian and MIS-5d, 5b these lakes overflowed through the Turgay pass into the Aral Sea, but during MIS-4 the overflow is predicted to have occurred north of the Urals. West of the Urals the palaeo-lake predictions are strongly controlled by whether the Kara Ice Sheet dammed the White Sea. If it did, then the lake levels are controlled by the topography of the Dvina basin with overflow directed into the Kama-Volga river system. Comparisons of predicted with observed MIS-5b lake levels of Komi Lake favour models in which the White Sea was in contact with the Barents Sea.

Atmospheric circulation over the North Atlantic has undergone significant fluctuations during the Holocene. To better constrain these changes and their impacts on the Fennoscandian subarctic, we investigated molecular and inorganic proxies as well as plant wax D/H isotopes (δDC28) in a Holocene sedimentary record from Lake Torneträsk (Sweden). These data indicate a thermal maximum c. 8100 to 6300 cal. a BP with reduced soil organic matter input, followed by a long-term cooling trend with increasing soil erosion. δD data suggest a stable atmospheric circulation with predominance of westerly flow and North Atlantic moisture sourcing during the Early and Middle Holocene. A substantial depletion in δD followed by increased flood frequency starting at c. 5300 cal. a BP and intensifying c. 1500 cal. a BP suggests a reorganization of the atmospheric circulation from zonal towards meridional flow with predominantly Arctic Ocean and Baltic Sea moisture sourcing.