Carbon transformation along the Eurasian shelves in water of Atlantic origin is estimated. Nutrient, oxygen, and inorganic and organic carbon data were used in the evaluation. By comparing the relative deficit of the different chemical constituents it is possible to evaluate the transformation of carbon. It can be seen that the chemical signature in the shelf seas was modified extensively, corresponding to an export production from the upper 50 m in the Barents Sea of 28-32 g C m(-2), which is five times higher than that in the Kara-Laptev Seas and over the deep Eurasian basin. The difference in the export production, computed from the nutrient deficit, and the observed deficit of dissolved inorganic carbon is attributed air-sea exchange of CO2. With this approach the relative oceanic uptake of CO2 from the atmosphere was estimated to be 70% (44 g C m(-2)) in the Barents Sea and 15% (1 g C m(-2)) in the Kara-Laptev Seas, relative to the export production. Of the export production in the Barents Sea, about a quarter is found as DOC. The difference between the chemical signature at the Laptev Sea shelf slope and over the Lomonosov Ridge is negligible, which shows that the transformation of carbon is very small in the surface layers of the Eurasian basin. Combining the chemical transformation with reported volume transports gives an annual export production of 9.6 x 10(12) g C yr(-1) in the Barents Sea. The oceanic uptake of CO2 for the same area is 9.2 x 10(12) g C yr(-1). (C) 2001 Elsevier Science Ltd. All rights reserved.

In the summer of 2005, continuous surface water measurements of fugacity Of CO2 (fCO(2)(SW)), salinity and temperature were performed onboard the IB Oden along the Northwest Passage from Cape Farwell (South Greenland) to the Chukchi Sea. The aim was to investigate the importance of sea ice and river runoff on the spatial variability of fCO(2) and the sea-air CO2 fluxes in the Arctic Ocean. Additional data was obtained from measurements of total alkalinity (A(T)) by discrete surface water and water column sampling in the Canadian Arctic Archipelago (CAA), on the Mackenzie shelf, and in the Bering Strait. The linear relationship between A(T) and salinity was used to evaluate and calculate the relative fractions of sea ice melt water and river runoff along the cruise track. High-frequency fCO(2)(SW) data showed rapid changes, due to variable sea ice conditions, freshwater addition, physical upwelling and biological processes. The fCO(2)(SW) varied between 102 and 678 mu atm. Under the sea ice in the CAA and the northern Chukchi Sea, fCO(2)(SW) were largely CO2 undersaturated of approximately 100 mu atm lower than the atmospheric level. This suggested CO2 uptake by biological production and limited sea-air CO2 gas exchange due to the ice cover. In open areas, such as the relatively fresh water of the Mackenzie shelf and the Bering Strait, the fCO(2)(SW) values were close to the atmospheric CO2 level. Upwelling of saline and relatively warm water at the Cape Bathurst caused a dramatic fCO(2)(SW) increase of about 100 mu atm relative to the values in the CAA. At the southern part of the Chukchi Peninsula we found the highest fCO(2)(SW) values and the water was CO2 supersaturated, likely due to upwelling. In the study area, the calculated sea-air CO2 flux varied between an oceanic CO2 sink of 140 mmol m(-2) d(-1) and an oceanic source of 18 mmol m(-2) d(-1). However, in the CAA and the northern Chukchi Sea, the sea ice cover prevented gas exchange, and the CO2 fluxes were probably negligible at this time of the year. Assuming that the water was exposed to the atmosphere by total melting and gas exchange would be the only process, the CO2 Undersaturated water in the ice-covered areas will not have the time to reach the atmospheric CO2 value, before the formation of new sea ice. This study highlights the value of using high-frequency measurements to gain increased insight into the variable and complex conditions, encountered on the shelves in the Arctic Ocean. (C) 2009 Elsevier Ltd. All rights reserved.

Global and climate changes are subject to scientific, societal and political debates. Recent observational evidence and results of global climate models have identified the circumpolar North as a region particularly susceptible to future climate change. To understand and assess the consequences of these changes for environmental and societal components of the European Arctic, the Barents Sea Impact Study (BASIS), an EU-funded integrated regional impact study (IRIS) has been carried out (ENV4-CT-97-0637). In common with global integrated assessments (IAs), IRISs also take a holistic view on climate change and its impact. Contrary to IAs, however, IRISs adopt a regional to sub-regional spatial scale. BASIS was carried out by an interdisciplinary team of specialists from 13 institutions in 6 countries. Major results pertain to impacts of possible climate change on marine and terrestrial ecosystems, freshwater hydrology, marine trace gas budgets, forestry and fishery. However, in this paper we focus on the major methodological aspects of an IRIS in general and on methods applied in BASIS in particular. (C) 2003 Elsevier Ltd. All rights reserved.

Historic data from the Russian-American Hydrochemical Atlas of Arctic Ocean together with data from the TRANSDRIFT II 1994 and TUNDRA 1994 cruises have been used to assess the spatial and inter-annual variability of carbon and nutrient fluxes, as well as air-sea CO2 exchange in the Laptev and western East Siberian Seas during the summer season. Budget computations using summer data of dissolved inorganic phosphate (DIP), dissolved inorganic nitrogen (DIN) and dissolved inorganic carbon (DIC) gives that the Laptev Sea shelf is a net sink of DIP and DIN of 2.5 x 10(6), 23.2 x 10(6) mold(-1), respectively, while it is a net source of DIC (excluding air-sea exchange) of 1249 x 10(6) mol d(-1). In the East Siberian Seas the budget computations give 0.5 x 10(6), - 11.4 x 10(6) and - 173 x 10(6) mold(-1) (minus being a sink) for DIP, DIN, and DIC, respectively. In summers, the Laptev Sea Shelf is net autotrophic while the East-Siberian Sea Shelf is net heterotrophic, and both systems are weak net denitrifying. The Laptev Sea Shelf takes up 2.1 mmol CO2 m(-2) d(-1) from atmosphere, whereas the western part of the East-Siberian Sea Shelf loose 0.3 mmol CO2 m(-2) d(-1) to the atmosphere. The variability of DIP, DIN and DIC fluxes during summer in the different regions of the Laptev and East Siberian Seas depends on bottom topography, river runoff, exchange with surrounding seas and wind field. (c) 2007 Elsevier Ltd. All rights reserved.

The bubble-mediated transport and eventual fate of methane escaping from the seafloor is of great interest to researchers in many fields. Acoustic systems are frequently used to study gas seep sites, as they provide broad synoptic observations of processes in the water column. However, the visualization and characterization of individual gas bubbles needed for quantitative studies has routinely required the use of optical sensors which offer a limited field of view and require extended amounts of time for deployment and data collection. In this paper, we present an innovative method for studying individual bubbles and estimating gas flux using a calibrated wideband from the Bolin Centre for Climate Research database: http://bolin.su.se/data/.and split-beam echosounder. The extended bandwidth (16 - 26 kHz) affords vertical range resolution of approximately 7.5 cm, allowing for the differentiation of individual bubbles in acoustic data. Split-aperture processing provides phaseangle data used to compensate for transducer beam-pattem effects and to precisely locate bubbles in the transducer field of view. The target strength of individual bubbles is measured and compared to an analytical scattering model to estimate bubble radius, and bubbles are tracked through the water column to estimate rise velocity. The resulting range of bubble radii (0.68-8.40 mm in radius) agrees with those found in other investigations with optical measurements, and the rise velocities trends are consistent with published models. Together, the observations of bubble radius and rise velocity offer a measure of gas flux, requiring nothing more than vessel transit over a seep site, bypassing the need to deploy time-consuming and expensive optical systems.