Influence of Arctic Sea Ice Loss in Autumn Compared to That in Winter on the Atmospheric Circulation. Issue 4 (15th February 2019)

• Record Type: Journal Article
• Authors: Blackport, Russell; Screen, James A.
• Is Part Of: Geophysical research letters. Volume 46:Issue 4(2019)
• Page Start: 2213
• Page End: 2221
• Publication Date: 2019-02-15
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL081469
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: There is growing evidence that Arctic sea ice loss affects the large‐scale atmospheric circulation. Some studies suggest that reduced autumn sea ice may be a precursor to severe midlatitude winters. Here we use coupled ocean–atmosphere model experiments to investigate the extent to which the winter atmospheric circulation response to Arctic sea ice loss is driven by sea ice loss in preceding months. We impose different seasonal cycles of sea ice by using various combinations of sea ice albedo parameters. Year‐round sea ice loss causes an equatorward migration of the eddy‐driven jet and a shift toward the negative phase of the North Atlantic Oscillation in winter. However, these circulation changes are not found when sea ice is reduced only in late summer and autumn, despite high‐latitude warming persisting into the winter. Our results imply that the winter atmospheric circulation response to sea ice loss is primarily driven by sea ice loss in winter rather than in autumn. Plain Language Summary: Arctic sea ice loss is already affecting the inhabitants and wildlife of the Arctic. There is also concern that sea ice loss might be impacting weather and climate elsewhere. Past studies have proposed that Arctic sea ice loss can affect the jet stream, which has a big influence on weather and climate in midlatitudes. It remains unclear, however, if the jet stream is more strongly affected by sea ice loss in autumn or by sea ice loss in winter. This is an important question, as if winter weather was strongly affected by autumn sea ice, severe winters might be predictable a few months in advance. We have run experiments with a climate model in which we artificially reduce the sea ice in order to study the effects of sea ice loss on the jet stream. An experiment with autumn and winter sea ice loss shows a weakening and southward shift of the jet stream in midlatitudes. However, these changes are not seen in an experiment with sea ice loss in autumn but not in winter. We conclude that the sea ice loss in winter has a bigger effect on the jet stream than does sea ice loss in autumn. Key Points: Coupled ocean‐atmosphere model experiments are forced with different seasonal cycles of Arctic sea ice loss Year‐round sea ice loss causes an equatorward jet shift and a negative North Atlantic Oscillation response in winter Autumn sea ice loss does not affect the winter atmospheric circulation, implying that winter response is driven by winter ice loss