Future Climate Change in the Northern Bering Sea

Abstract

The Bering Sea is undergoing major changes from increasing winter temperatures to the north, extreme minimum sea-ice years in 2018 and 2019, through to an ecosystem reorganisation and negative impacts on communities' economic and subsistence food resources. These events have emerged under a global warming background, with positive feedback processes through a weakened atmospheric Alaskan Arctic Front (AAF) that promotes a self-reinforcing process of sea-ice loss, warmer air and sea temperatures, a wavy jet stream, and southerly winds. Interannual variability is still important: during 2021–2024 the Aleutian Low-pressure system was regionally dominant in supporting a strong AAF, and sea-ice conditions were observed close to the climatological mean. Before 2017, the AAF, consisting of cold dry air mass to the north and moist relatively warm air mass to the south, was a barrier to northward movement of storms, keeping the northern Bering/Chukchi seas with a cold Arctic climate. That historical situation is ending. Of critical importance is the probable reoccurrence of low Bering Sea sea-ice years over the next decades and related ecosystem impacts. We propose that radically low sea ice will have a frequency of one to three 2018-like low sea-ice events per decade in the coming two decades, based on a historical meteorological analysis and ensemble climate model projections. Arctic temperatures to the north are increasing, weakening their contribution to the AAF. A weakened AAF and low sea-ice years needs the winter Aleutian low pressure system to be far to the west of its average position, with southerly rather than northeasterly winds, warm years and low sea-ice extent. From 1948 to 2024 meteorological records, this western location occurred with a range of zero to three times per decade. Communities need to plan for a response to intermittent occurrence of 2018-like extreme sea-ice loss and their ecosystem impacts over the coming decades.