The Paleoceanography of the Bering Sea During the Last Glacial Cycle

Mea Young S. Cook, Ph.D., 2006
Lloyd Keigwin, Advisor

In this thesis, I present high-resolution stable-isotope and planktonic-fauna records from Bering Sea sediment cores (50-0ka). During MIS3 at 30-20ka in a core from near Umnak Plateau (1467m), there were episodic occurrences of diagenetic carbonates which are associated with sulfate reduction and possibly anaerobic oxidation of methane. During MIS3 at 55-20ka in a core from Bowers Ridge (2209m), N. pachyderma (s.) and Uvigerina d18O and d13C show no coherent variability on millennial time scales. A high sedimentation rate core (200cm/ky) from 1132m on Bering Slope is laminated during the Bolling, Allerod, and early Holocene, where the ages of lithological transitions match the ages of those climate events in Greenland (GISP2) within the age model uncertainties. In a compilation of published North Pacific benthic-planktonic 14C measurements (475-2700m water depth), there was no consistent change in 14C profiles between the present and the Last Glacial Maximum, Bolling-Allerod, or Younger Dryas. N. pachyderma (s.) d18O in the Bering Slope core decreases rapidly (<220y) by 0.7-0.8permil at the onset of the Bolling and end of the Younger Dryas. These isotopic shifts are accompanied by transient decreases in N. pachyderma (s.) relative abundance, suggesting that the isotopic events are transient warmings and sustained freshenings.