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Abstract: This paper compares and contrasts the ecosystems of the Barents and Chukchi Seas. Despite their similarity in a number of features, the Barents Sea supports a vast biomass of commercially important fish, but the Chukchi does not. Here we examine a number of aspects of these two seas to ascertain how they are similar and how they differ. We then indentify processes and mechanisms that may be responsible for their similarities and differences. Both the Barents and Chukchi Seas are high latitude, seasonally ice covered, Arctic shelf-seas. Both have strongly advective regimes, and receive water from the south. Water entering the Barents comes from the deep, ice-free and “warm” Norwegian Sea, and contains not only heat, but also a rich supply of zooplankton that supports larval fish in spring. In contrast, Bering Sea water entering the Chukchi in spring and early summer is cold. In spring, this Bering Sea water is depleted of large, lipid-rich zooplankton, thus likely resulting in a relatively low availability of zooplankton for fish. Although primary production on average is similar in the two seas, fish biomass density is an order of magnitude greater in the Barents than in the Chukchi Sea. The Barents Sea supports immense fisheries, whereas the Chukchi Sea does not. The density of cetaceans in the Barents Sea is about double that in the Chukchi Sea, as is the density of nesting seabirds, whereas, the density of pinnipeds in the Chukchi is about double that in the Barents Sea. In the Chukchi Sea, export of carbon to the benthos and benthic biomass may be greater. We hypothesize that the difference in fish abundance in the two seas is driven by differences in the heat and plankton advected into them, and the amount of primary production consumed in the upper water column. However, we suggest that the critical difference between the Chukchi and Barents Seas is the pre-cooled water entering the Chukchi Sea from the south. This cold water, and the winter mixing of the Chukchi Sea as it becomes ice covered, result in water temperatures below the physiological limits of the commercially valuable fish that thrive in the southeastern Bering Sea. If climate change warms the Barents Sea, thereby increasing the open water area via reducing ice cover, productivity at most trophic levels is likely to increase. In the Chukchi, warming should also reduce sea ice cover, permitting a longer production season. However, the shallow northern Bering and Chukchi Seas are expected to continue to be ice-covered in winter, so water there will continue to be cold in winter and spring, and is likely to continue to be a barrier to the movement of temperate fish into the Chukchi Sea. Thus, it is unlikely that large populations of boreal fish species will become established in this Arctic marginal sea. [Copyright &y& Elsevier]

Abstract: The Norwegian Component of the Ecosystem Studies of Sub-Arctic Seas (NESSAS) was funded by the Research Council of Norway from 2005 to 2008. Its aim was to quantify the impact of climate variability on the structure and function of the marine ecosystem of the Barents Sea and adjacent waters in order to predict the ecosystem responses to possible future climate change and their possible economic impact. This paper reviews research highlights dealing with climate forcing and its influence. New insights were provided on the role of large-scale atmospheric forcing on the physical oceanography including the effect of Arctic and Atlantic cyclones on the variability of the ice extent in the Barents Sea and the non-linear response of the sub-polar gyre to North Atlantic Oscillation (NAO) forcing. In addition, the NAO was also shown to influence the biology, for example shrimp recruitment in the Barents Sea and primary production in the Nordic Seas, with the strength and sign of the correlations being spatially dependent. The importance of longer term climate variability in the form of the Atlantic Multidecadal Oscillation (60–80years period) was stressed, as it leads to significant changes in fish production, shifts in distribution and changes in spawning sites in the Barents Sea as well as other northern Atlantic ecosystems. Results from comparative studies between several US ecosystems and those of the Norwegian and Barents Seas are presented, including evidence of increased primary productivity in the Barents Sea in recent years and the poleward movement of zooplankton and fish. In addition recruitment patterns of major demersal and pelagic species in the Barents Sea generally show synchrony with those in the Gulf of Maine indicating a common external forcing. Possible ecosystem scenarios for the Barents Sea under anthropogenic-induced future climate change were developed including expectations of structural and functional changes due to distributional changes of many species. Of particular note is the likelihood of increases in the productivity of several fish species, including cod and herring, which potentially could result in higher fisheries yields. [Copyright &y& Elsevier]

Abstract: This paper presents palynological evidence from the late Early Triassic (late Smithian) to the Late Triassic (Rhaetian) of the Barents Sea area: A continuous palynological succession from an exploration well (7228/7-1A) in the Nordkapp Basin (SW Barents Sea) and palynological data from a series of shallow cores drilled at the Svalis Dome (Central Barents Sea) representing selected Triassic intervals. These fully marine sediments are independently dated by marine faunas. Both records show significant shifts in the distribution of the main floral elements. Changing ratios of spore-pollen taxa, grouped as hygrophytes versus xerophytes and spores versus pollen, reveal major changes of the floras within the studied interval. One distinct turnover coincides with the Smithian/Spathian boundary where lycopsid and pteridophyte spores dominated assemblages change to pollen (pteridosperms and conifers) dominated assemblages. Lower Middle Triassic assemblages are again dominated by lycopsid spores while the assemblages from the upper part of the Middle Triassic and the lower part of the Late Triassic are characterised by dominance of coniferous pollen and show the decline of pteridosperms. In the latest Triassic fern spores are abundant and diverse. In contrast to the Middle Triassic the pollen assemblages are characterized by cycadophytes and Araucariacites. These distribution patterns are interpreted to reflect climatic changes. The presented results from Norwegian Boreal areas confirm the significant differences between quantitative distribution of specific taxa as well as diversity of major groups in plant assemblages from low and mid latitudes. The present survey opens new perspectives for more detailed comparisons and climatic interpretations of floras from the Triassic period, a time during which Mesozoic vegetation established. The major changes in the dominance of specific floral elements, especially the diversification and spreading of the conifers, can probably be related to climatic changes. [Copyright &y& Elsevier]

Abstract: Concern about future anthropogenic warming has lead to demands for information on what might happen to fish and fisheries under various climate-change scenarios. One suggestion has been to use past events as a proxy for what will happen in the future. In this paper a comparison between the responses of Atlantic cod (Gadus morhua) to two major warm periods in the North Atlantic during the 20th century is carried out to determine how reliable the past might be as a predictor of the future. The first warm period began during the 1920s, remained relatively warm through the 1960s, and was limited primarily to the northern regions (>60°N). The second warm period, which again covered the northern regions but also extended farther south (30°N), began in the 1990s and has continued into the present century. During the earlier warm period, the most northern of the cod stocks (West Greenland, Icelandic, and Northeast Arctic cod in the Barents Sea) increased in abundance, individual growth was high, recruitment was strong, and their distribution spread northward. Available plankton data suggest that these cod responses were driven by bottom-up processes. Fishing pressure increased during this period of high cod abundance and the northern cod stocks began to decline, as early as the 1950s in the Barents Sea but during the 1960s elsewhere. Individual growth declined as temperatures cooled and the cod distributions retracted southward. During the warming in the 1990s, the spawning stock biomass of cod in the Barents Sea again increased, recruitment rose, and the stock spread northward, but the individual growth did not improve significantly. Cod off West Greenland also have shown signs of improving recruitment and increasing biomass, albeit they are still very low in comparison to the earlier warming period. The abundance of Icelandic cod, on the other hand, has remained low through the recent warm period and spawning stock biomass and total biomass are at levels near the lowest on record. The different responses of cod to the two warm events, in particular the reduced cod production during the recent warm period, are attributed to the effects of intense fishing pressure and possibly related ecosystem changes. The implications of the results of the comparisons on the development of cod scenarios under future climate change are addressed. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]