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BERING LAND BRIDGE
The Bering Strait connects the Pacific and Atlantic oceans via the Arctic Ocean. The Strait is currently only 50 meters deep. During low sea level stands produced by continental glaciation it was emergent, forming the Bering Land Bridge connection between North America and Asia. This is the only area on Earth where the circulation between ocean basins has been blocked and a migration corridor between continental landmasses has been opened by falling sea levels of the Pleistocene epoch. Scientific drilling to recover a proximal record of the region can be most promisingly recovered in the thick (> 3 km) basinal sequences of the Norton and Hope basins immediately to the south and north of the Strait. The sedimentary record of marine transgressions and regressions within the Bering Strait region that includes intercalated terrestrial lacustrine sediments would have the potential to resolve crucial questions regarding Bering Land Bridge paleoecology and climate change. Funds to conduct a workshop to identify, select and prioritize drilling sites in Bering Sea Shelf basins with the potential to contain thick sequences of alternating marine and terrestrial sediments was approved by Joint Oceanographic Institutions/United States Science Support Program (JOI/USSSP) . Workshop to be held 21-222 June, 2005. The workshop focused on key scientific questions, identification of drilling sites with the potential to answer these questions, discussing the most appropriate platform or platforms, proposal submissions, and multi-proxy analyses. Products of this workshop will include a discussion of the potential scientific gains, a list of recommended drilling sites, and, ultimately, proposals submitted to the Integrated Ocean Drilling Program. Scientific issues included: Studies of global freshwater transport have demonstrated a net flux of water from the North Pacific to the North Atlantic through the Bering Strait at a rate of 0.8 Sverdrups per year which accounts for nearly one-third of the total freshwater input to the Arctic Ocean . Models indicate that increased flow of fresher North Pacific water through the submerged Bering Strait can also lead to suppression of NADW formation . The opening and closing of the Bering Strait clearly has global climatic implications with regard to the cause and the duration of glacial and interglacial climatic oscillations, yet the numerous and sometimes contradictory models cannot be adequately tested because an accurate chronology of the emergence and submergence of the Strait is lacking. Reconstruction of the sea level history of the Bering Strait, including the exact timing of the opening and closing of the land bridge and the rates of associated sea level changes, the presence/absence of sea/terrestrial ice, is essential to understanding its role as a trigger or pacemaker of northern hemisphere climate changes. The Bering Land Bridge served as an oscillating biological filter between marine and terrestrial for plants, animals, and humans that passed between Eurasia and North America during the Late Quaternary period. Previous exchanges of species between Asia and North America during the Miocene and Late Cretaceous indicate that the Bering Strait region experienced intervals of emergence prior to the Pleistocene. Intercontinental exchange and competition from foreign species has been sited as a causal factor in the Cretaceous, Eocene, and Pleistocene extinctions. It needs to be determined if there was a north-south and/or east west ecological gradient on the central land bridge? If so did the gradients varied in space and time? In addition to organic remains, identification and dating of tephras contained within terrestrial or marine sediments of the Bering Strait will further enhance understanding of the chronology of Quaternary eruptions and their role in global climate variations. Geochemical characterization of tephras from Bering Strait cores could provide a record of the frequency, magnitude, and timing of eruptions at volcanoes of the Aleutian Arc, Seward Peninsula, and islands in Bering Sea. Furthermore, volcanic ash deposits are one of the only possible ways of demonstrating precise correlations between terrestrial and marine deposits throughout Beringia and the Bering Sea. . The workshop participants resolved that in order to address unresolved questions regarding global ocean circulation and rapid climate changes, and to permit reconstruction of the flora, fauna, and climate of the lowlands in the center of the Beringian subcontinent, basinal features that contain both marine and terrestrial lacustrine sediments must be targeted Summary provided by http://classic.ipy.org/development/eoi/proposal-details.php?id=29