Can preferred atmospheric circulation patterns over the North-Atlantic-Eurasian region be associated with arctic sea ice loss?

Berit Crasemann,Dörthe Handorf,Ralf Jaiser,Klaus Dethloff,Tetsu Nakamura,Jinro Ukita,Koji Yamazaki

doi:10.1016/j.polar.2017.09.002

Abstract

In the framework of atmospheric circulation regimes, we study whether the recent Arctic sea ice loss and Arctic Amplification are associated with changes in the frequency of occurrence of preferred atmospheric circulation patterns during the extended winter season from December to March. To determine regimes we applied a cluster analysis to sea-level pressure fields from reanalysis data and output from an atmospheric general circulation model. The specific set up of the two analyzed model simulations for low and high ice conditions allows for attributing differences between the simulations to the prescribed sea ice changes only. The reanalysis data revealed two circulation patterns that occur more frequently for low Arctic sea ice conditions: a Scandinavian blocking in December and January and a negative North Atlantic Oscillation pattern in February and March. An analysis of related patterns of synoptic-scale activity and 2 m temperatures provides a synoptic interpretation of the corresponding large-scale regimes. The regimes that occur more frequently for low sea ice conditions are resembled reasonably well by the model simulations. Based on those results we conclude that the detected changes in the frequency of occurrence of large-scale circulation patterns can be associated with changes in Arctic sea ice conditions.

Highlights

Over the last decades, the Arctic sea ice has declined throughout the year, but most strongly in late summer
In the framework of atmospheric circulation regimes, we study whether the recent Arctic sea ice loss and Arctic Amplification are associated with changes in the frequency of occurrence of preferred atmospheric circulation patterns during the extended winter season from December to March
We argue for the association with Arctic sea ice changes is reasoned by the comparison of results from reanalysis data with the output from the two atmospheric general circulation model (AGCM) simulations which differ only in terms of the Arctic sea ice conditions

Summary

Introduction

The Arctic sea ice has declined throughout the year, but most strongly in late summer (see e.g.http://www.meereisportal.de/en/seaicetrends/monthly-meanarctic). Low sea ice conditions in autumn often result in cold Eurasian winters, extreme snowfall, strong blockings and a negative phase of the Arctic Oscillation (AO) and. Francis et al (2009) investigated the dynamical response to the Arctic sea ice loss, which becomes detectable in terms of modifications of Rossby waves and the jet stream. They showed that the reduced sea ice leads to a weakening of the polar jet stream. Studies by Petoukhov and Semenov (2010), Inoue et al (2012), Mori et al (2014), and Overland (2016) showed that low sea ice conditions in autumn are linked to a strong Siberian high and cold Eurasian winters. Additional moisture provided from more opened Arctic Ocean leads to increased snow fall over Eurasia in autumn and winter as pointed out by Cohen et al (2012), Liu et al (2012), and Wegmann et al

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