Ovsepyan, E.A., Ivanova, E.V., Lembke-Jene, Lester, Max, L., Tiedemann, Ralf and Nürnberg, Dirk (2017) Penultimate and last glacial oceanographic variations in the Bering Sea on millennial timescales: Links to North Atlantic climate. Quaternary Science Reviews, 163 . pp. 135-151. DOI 10.1016/j.quascirev.2017.03.012.

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Abstract

Highlights

• Mid-MIS 6 changes resemble Dansgaard-Oeschger variability during MIS 3.
• Both Termination I and II demonstrate similar two-step-like character.
• Sea surface bioproductivity was higher during MIS 6 than during MIS 4-2.
• Bottom-water conditions were less stable during MIS 6 than during MIS 4-2.
• Sea-ice cover was reduced during MIS 6 as compared to MIS 4-2.

Abstract

We present high-resolution multi-proxy records from a marine sediment core (SO201-2-85KL) from the western Bering Sea to assess orbital- and millennial-scale paleoceanographic conditions during two last glacial intervals, including both terminations. Based on changes in foraminiferal assemblages, grain-size content and previously published TOC and δ13C records, we reconstruct variations in sea-surface biological productivity, intermediate-water oxygenation and sea-ice conditions during the last 180 kyr. Our data demonstrate remarkable differences between the penultimate (MIS 6) and last (MIS 4-2) glacial. Relatively high sea surface bioproductivity and reduced sea-ice cover are reconstructed for the penultimate glacial interval, whereas low bioproductivity and expanded sea-ice cover appear to be typical for the last glacial. Millennial-scale changes in intermediate water ventilation are inferred from faunal records for the middle part of the penultimate glacial. High-amplitude environmental variability during the penultimate glacial time in the Bering Sea resembles the well-known Dansgaard-Oeschger oscillations, and roughly corresponds to similar rapid climatic fluctuations found in North Atlantic records. The Termination II and I intervals display a similar succession of high-bioproductivity events, being more pronounced during the penultimate glacial-interglacial transition, probably due to the different orbital configuration. During the late phase of Termination II, two short intervals, characterized by high sea surface bioproductivity and low oxygen content of bottom waters, resemble the Bølling and Allerød warmings, whereas an episode with low bioproductivity occurs in between, similar to the Older Dryas. Our results provide support for a close circumpolar coupling between high-latitude environments on millennial timescales at least since the penultimate glacial.

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