Glacial/Interglacial to Millennial-Scale Environmental Variability Over the Last 400,000 Years (OIS 1-10) as Recorded in Deep-Sea Sediments of the Bering Sea

Abstract:

IODP Ex. 323 sites U1339 (54.7°N), U1343 (57.4°N), U1344 (59.0°N), and U1345 (60.1°N), situated along the N/NE Bering Sea slope margin, have high sediment-accumulation-rate records of Quaternary climate/environmental variability. We have developed a new high-resolution chronostratigaphic framework for correlating and dating these sites over the last 400,000 years using a combination of absolute oxygen isotope, relative paleointensity, and directional paleomagnetic secular variation age dating. We can define synchronous environmental variability across these four sites with a resolution of ~±200 years over the entire 400,000 year time span. We see 3-5,000 year cycles of high/low terrigenous flux, derived from the continental margin and shelf, during all the interglacials, which are synchronous among the sites. Each interglacial has 9-12 of these cycles. We think these are caused by millennial-scale oscillations in Alaskan continental climate during interglacials. We also note evidence for millennial-scale relatively-warm/seasonally-ice-free conditions within selected intervals of all glacials and millennial-scale intervals of apparently cold/permanent ice conditions during all the interglacials. Although glacials are dominated by cold/permanent ice conditions and interglacials by warm/seasonally ice free conditions, it seems that almost as much time is spent in the opposite pattern as in the normal pattern.