Orbital and suborbital environmental changes in the Western Bering Sea during the last 172 ka Inferred from Diatom and Productivity Proxies

Abstract

Abstract Diatom abundance and species distribution present a subtle tool for the reconstruction of the orbital and millennial-centennial climate and environmental changes in the southwestern Bering Sea during the last 172 ka, in addition to productivity proxies (chlorine, color b*, and Ca/Ti ratio), magnetic susceptibility, and biomarker proxies derived earlier and in this paper from the sediment core SO201-2-85KL recovered at the middle Shirshov Ridge (MSR). Available data indicate that the MSR area undergoes a significant seasonal sea ice influence during cold MISs 6.5–2. During the colder MIS 2, a main area of ice discharge extended southward of the MSR, likely outside of the sea, while over the coldest MIS 6.2, the MSR area was free from ice due to the shifting of the Aleutian Low to the eastern Siberian coast and the northward transfer of the warm and wet air of storm tracks into the western Bering Sea. During the warm MIS 5.5, the sea ice influence at the MSR area was negligible, nearly the same as it was over the Holocene, and it began to increase after event 26 (120.5 ka). The millennial scale variability of diatom abundance and its species distribution were triggered by Greenland Interstadials accompanied by productivity changes. The diatom species distribution showed complicated pattern of variability of the MSR environment, consistent with the millennial-centennial changes of the Greenland air temperature over the Dansgaard -Oeschger cycles. It confirms the rapid mechanisms of atmospheric teleconnection between these remote regions on the millennial-centennial time scale.