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The annual minimum Antarctic sea ice extent (SIE) in February 2022 hits a record low in the satellite era, with less than 2 million square kilometres observed on 25 February 2022, contrasting with the slightly positive trend in the Antarctic SIE prior to 2014. However, the preceding Amundsen Sea Low (ASL) in austral spring 2021 was the deepest since 1950. According to a linear regression model, the very low ASL contributed about 60% to the record low SIE in 2022. This study further investigates the underlying mechanism. The investigation of the lagged impact of the ASL on Antarctic SIE is based on observational data and state-of-the-art simulations. We found that (a) the deepened ASL associated with strengthened southerly winds accelerates the sea ice export away from the western Antarctic continent in spring, leading to the expansion of coastal polynyas (open water areas); (b) through the positive ice-ocean albedo feedback, the lack of the sea ice off the coastline enhances solar heating in the upper ocean and further sea ice melting in summer can occur. Specifically, in spring 2021, the deepest ASL is accompanied by a large sea-ice area flux of about 17.6 × 10 ^3 km ^2 across 70° S over the Ross Sea in October and November, contributing to a significant increase in net surface radiation of 20–30 W m ^−2 and upper ocean warming of about 0.5 K in summer. Therefore, the deepened ASL in spring 2021 plays a crucial role for the record low Antarctic SIE in February 2022. In addition, it is found that both the La Niña conditions and the strong stratospheric polar vortex contributed significantly to the very strong ASL in 2021. Currently, nearly 2/3 of Earth system models in the Coupled Model Intercomparison Project Phase 6 have difficulties capturing the relationship between the ASL and the Antarctic SIE.

The Greenland high (GL-high) coincides with a local center of action of the summer North Atlantic Oscillation and is known to have significant influence on Greenland ice sheet melting and summer Arctic sea ice. However, the mechanism behind the influence on regional Arctic sea ice is not yet clear. In this study, using reanalysis datasets and satellite observations, the influence of the GL-high in early summer on Arctic sea ice variability, and the mechanism behind it, are investigated. In response to an intensified GL-high, sea ice over the Beaufort Sea shows significant decline in both concentration and thickness from June through September. This decline in sea ice is primarily due to thermodynamic and mechanical redistribution processes. Firstly, the intensified GL-high increases subsidence over the Canadian Basin, leading to an increase in surface air temperature by adiabatic heating, and a substantial decrease in cloud cover and thus increased downward shortwave radiation. Secondly, the intensified GL-high increases easterly wind frequency and wind speed over the Beaufort Sea, pushing sea ice over the Canadian Basin away from the coastlines. Both processes contribute to an increase in open water areas, amplifying ice–albedo feedback and leading to sea ice decline. The mechanism identified here differs from previous studies that focused on northward moisture and heat transport and the associated increase in downward longwave radiation over the Arctic. The impact of the GL-high on the regional sea ice (also Arctic sea ice extent) can persist from June into fall, providing an important source for seasonal prediction of Arctic sea ice. The GL-high has an upward trend and reached a record high in 2012 that coincided with a record minimum summer Arctic sea ice extent, and has strong implications for summer Arctic sea ice changes.