Abstract
Sea ice and associated feedback mechanisms play an important role for both long- and short-term climate change. Our ability to predict future sea ice extent, however, hinges on a greater understanding of past sea ice dynamics. Here we investigate sea ice changes in the eastern Bering Sea prior to, across, and after the Mid-Pleistocene transition (MPT). The sea ice record, based on the Arctic sea ice biomarker IP25 and related open water proxies from the International Ocean Discovery Program Site U1343, shows a substantial increase in sea ice extent across the MPT. The occurrence of late-glacial/deglacial sea ice maxima are consistent with sea ice/land ice hysteresis and land−glacier retreat via the temperature−precipitation feedback. We also identify interactions of sea ice with phytoplankton growth and ocean circulation patterns, which have important implications for glacial North Pacific Intermediate Water formation and potentially North Pacific abyssal carbon storage.
Highlights
Sea ice and associated feedback mechanisms play an important role for both long- and shortterm climate change
The relative timing of sea ice changes in comparison to glacial/ interglacial (G/IG) cycles is uncertain, resulting from the low resolution of the U1343 δ18Ob record prior to 1.2 Ma (Fig. 2), it is clear that this interval is within the late Pleistocene as indicated by biostratigraphy, magnetostratigraphy, and tuning of long-term U1343 δ18Ob42 to the LR04 stack[16]
IP25 was identified in 26 out of 32 samples analysed during Marine isotope stages (MIS) 51 to 44 (Fig. 2), demonstrating the presence of seasonal sea ice in the eastern Bering Sea prior to the Mid-Pleistocene transition (MPT)
Summary
Sea ice and associated feedback mechanisms play an important role for both long- and shortterm climate change. Investigating the interactions of sea ice dynamics with ocean circulation and productivity patterns and identifying the role of sea ice for major climate transitions is critical for our understanding of Arctic and sub-Arctic climate One such climate transition during the Quaternary Period is the Mid-Pleistocene transition (MPT, 1.2 −0.7 Ma). Conceptual modelling has identified potential key feedback mechanisms involving sea ice, such as the so-called ‘sea ice-switch’ hypothesis (SIS)[1,2,17], which suggests that sea ice can modify the climate state, switching it between a growing and a retreating land glacier mode, via a temperature−precipitation feedback Elevated concentrations of a tri-unsaturated HBI biomarker (HBI III), shown recently to be produced by certain diatoms in polar
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