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Arctic sea ice loss could dry out California

05 December 2017

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Arctic sea ice loss of the magnitude expected in the next few decades could impact California's rainfall and exacerbate future droughts, according to new research led by Lawrence Livermore National Laboratory (LLNL) scientists.

The dramatic loss of Arctic sea ice cover observed over the satellite era is expected to continue throughout the 21st century. Over the next few decades, the Arctic Ocean is projected to become ice-free during the summer. A new study by Ivana Cvijanovic and colleagues from LLNL and University of California, Berkeley shows that substantial loss of Arctic sea ice could have significant far-field effects, and is likely to impact the amount of precipitation California receives. The research appears in the 05 December edition of Nature Communications.

The study identifies a new link between Arctic sea ice loss and the development of an atmospheric ridging system in the North Pacific. This atmospheric feature also played a central role in the 2012-2016 California drought and is known for steering precipitation-rich storms northward, into Alaska and Canada, and away from California. The team found that sea ice changes can lead to convection changes over the tropical Pacific. These convection changes can in turn drive the formation of an atmospheric ridge in the North Pacific, resulting in significant drying over California.

Source: Lawrence Livermore National Laboratory (LLNL)

Image credit: Kathy Seibert / LLNL - Schematics of the teleconnection through which Arctic sea-ice changes drive precipitation decrease over California. Arctic sea-ice loss induced high-latitude changes first propagate into tropics, triggering tropical circulation and convection responses. Decreased convection and decreased upper level divergence in the tropical Pacific then drive a northward propagating Rossby wavetrain, with anticyclonic flow forming in the North Pacific. This ridge is responsible for steering the wet tropical air masses away from California.