Sea-ice response to climate change in the Bering Sea during the Mid-Pleistocene Transition

• Published in: Quaternary Science Reviews
• Main Authors: Worne, Savannah, Stroynowski, Zuzia, Kender, Sev, Swann, George E.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Bering Sea; Bering Strait; Ice Sheet; Sea ice; Subarctic
• Online Access: http://nora.nerc.ac.uk/id/eprint/530149/; https://nora.nerc.ac.uk/id/eprint/530149/1/1-s2.0-S0277379121001256-main.pdf; https://doi.org/10.1016/j.quascirev.2021.106918

Sea-ice is believed to be an important control on climatic changes through the Mid-Pleistocene Transition (MPT; 0.6–1.2 Ma). However, the low resolution/short timescale of existing reconstructions prevents a full evaluation of these dynamics. Here, diatom assemblages from the Bering Sea are used to investigate sea-ice evolution on millennial timescales. We find that sea-ice was primarily controlled by ice-sheet/sea level fluctuations that modulated warm water flow into the Bering Sea. Facilitated by an amplified Walker circulation, sea-ice expansion began at ∼1.05 Ma with a step-increase during the 900 kyr event. Maximal pack ice was simultaneous with glacial maxima, suggesting sea-ice was responding to, rather than modulating ice-sheet dynamics, as proposed by the sea-ice switch hypothesis. Significant pack ice, coupled with Bering Strait closure at 0.9 Ma, indicates that brine rejection played an integral role in the glacial expansion/deglacial collapse of intermediate waters during the MPT, regulating subarctic ocean-atmospheric exchanges of CO2.