Stable isotopes, core logging data, relative paleointensity, dry bulk density, biogenic opal, CN-data (TC, TOC, CaCO3, TN), element concentrations, and coarse fraction of three sediment cores from the western Bering Sea

We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach, our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas export production was low. Minor increases in marine productivity occurred during intervals of Marine Isotope Stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. The terrigenous material is suggested to be derived from continental sources on the eastern Bering Sea shelf and to be subsequently transported via sea ice, which is likely to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait is considered to have had an additional impact. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard-Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.

Sea-surface temperature reconstruction of sediments from the North Pacific and North Atlantic

Holocene climate variability is investigated in the North Pacific and North Atlantic realms, using alkenone-derived sea-surface temperature (SST) records as well as a millennial scale simulation with a coupled atmosphere-ocean general circulation model (AOGCM). The alkenone SST data indicate a temperature increase over almost the entire North Pacific from 7 cal kyr BP to the present. A dipole pattern with a continuous cooling in the northeastern Atlantic and a warming in the eastern Mediterranean Sea and the northern Red Sea is detected in the North Atlantic realm. Similarly, SST variations are opposite in sign between the northeastern Pacific and the northeastern Atlantic. A 2300 year long AOGCM climate simulation reveals a similar SST seesaw between the northeastern Pacific and the northeastern Atlantic on centennial time scales. Our analysis of the alkenone SST data and the model results suggests fundamental inter-oceanic teleconnections during the Holocene.

Phyto- and zooplankton of the southeastern Barents Sea in April 2000

Spring bloom of cold-water centric and pennate diatoms was observed in two different areas of the southeastern Barents Sea in April 2000: ice-free waters off the Kolguev Island northern shelf and the eastern Pechora Sea near the Karskie Vorota (Kara Gate) Straight in polynyas and ice-free patches in one-year-old ice. Maximal values of phytoplankton abundance and biomass were found at the ice edge. The bloom was localized in shallow water areas with depths less than 50 m in mixing zones of waters of different origin: warm Atlantic, cold coastal, and Arctic (Litke current) waters. Ice melting was among factors inducing the phytoplankton bloom. Each area had a specific phytocoenosis, whose structure was determined by water origin and ice conditions. In the western Kara Sea, under a solid (up to 30 cm thick) ice cover (i.e., under conditions of a hydrological winter), a spring phytoplankton succession was observed from its initial stage. In areas located close to the ice-cover edge, simultaneously with the mass phytoplankton bloom, the early spring zoocoenosis development manifested itself in mass spawning of euphausiids and mass appearance of Cirripedia nauplii and bottom polychaete larvae.