High sensitivity of Bering Sea winter sea ice to winter insolation and carbon dioxide over the last 5500 years

Summer sea ice in the Arctic Ocean has been shrinking in recent decades in tandem with increasing carbon dioxide emissions. However, winter Bering Sea sea ice extent, which forms in winter and is absent in the summer under modern climate, has remained relatively stable and/or has increased over the satellite record, suggesting that winter sea ice extent is less vulnerable to anthropogenic climate change and is more dependent on ocean-atmosphere circulation variability. Long-term projections predict a 34% loss in winter (February) sea ice extent for the Arctic as a whole by CE 2081–2100 using Coupled Model Intercomparison Project 5 (CMIP5) projections under representative concentration pathway (RCP) 8.5. However, Bering Sea winter sea ice extent in CE 2018 and CE 2019 was 60 to 70% lower than the previous mean spring (February, March, April, and May) extent from CE 1979 to CE 2017, suggesting that Bering Sea winter sea ice is diminishing more rapidly than models predict. The decline in these years was attributed to anomalous southerly atmospheric flow that also increased near-bottom water temperatures. How this recent warming and sea ice loss in the Bering Sea fits into the long-term context of climate change remains unresolved because of spatial gaps and low temporal resolution of regional paleoclimate and paleo–sea ice records. This is due in part to depositional limitations on the shallow Bering Shelf that underlies much of the Bering Sea, which has been more prone to erosion and low, irregular sediment accumulation during the Holocene.

In this study, Miriam C. Jones and colleagues used a record of peat cellulose oxygen isotopes from St. Matthew Island along with isotope-enabled general circulation model (IsoGSM) simulations to generate a 5500-year record of Bering Sea winter sea ice extent. 

Their results show that over the last 5500 years, sea ice in the Bering Sea decreased in response to increasing winter insolation and atmospheric carbon dioxide, suggesting that the North Pacific is highly sensitive to small changes in radiative forcing. They found that CE 2018 sea ice conditions were the lowest of the last 5500 years, and results suggest that sea ice loss may lag changes in carbon dioxide concentrations by several decades.

This paper was published in the journal, Science Advances, 02 Sep 2020:Vol. 6, no. 36.

High sensitivity of Bering Sea winter sea ice to winter insolation and carbon dioxide over the last 5500 years

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