Abstract
AbstractTo examine the atmospheric responses to Arctic sea-ice variability in the Northern Hemisphere cold season (October to following March), this study uses a coordinated set of large-ensemble experiments of nine atmospheric general circulation models (AGCMs) forced with observed daily-varying sea-ice, sea-surface temperature, and radiative forcings prescribed during the 1979-2014 period, together with a parallel set of experiments where Arctic sea ice is substituted by its climatology. The simulations of the former set reproduce the near-surface temperature trends in reanalysis data, with similar amplitude, and their multi-model ensemble mean (MMEM) shows decreasing sea-level pressure over much of the polar cap and Eurasia in boreal autumn. The MMEM difference between the two experiments allows isolating the effects of Arctic sea-ice loss, which explain a large portion of the Arctic warming trends in the lower troposphere and drives a small but statistically significant weakening of the wintertime Arctic Oscillation. The observed interannual co-variability between sea-ice extent in the Barents-Kara Seas and lagged atmospheric circulation is distinguished from the effects of confounding factors based on multiple regression, and quantitatively compared to the co-variability in MMEMs. The interannual sea-ice decline followed by a negative North Atlantic Oscillation-like anomaly found in observations is also seen in the MMEM differences, with consistent spatial structure but much smaller amplitude. This result suggests that the sea-ice impacts on trends and interannual atmospheric variability simulated by AGCMs could be underestimated, but caution is needed because internal atmospheric variability may have affected the observed relationship.
Highlights
The Arctic climate has experienced profound changes over the past decades, as its surface air temperature has risen 2–3 times faster than the global averaged temperatureDenotes content that is immediately available upon publication as open access
These experiments were designed to single out the influence of the Arctic sea ice variations on the atmospheric circulation during the 1979–2014 period, following a protocol developed by the Blue-Action Project, which is similar to that used by Perlwitz et al (2015) and Sun et al (2016), and recommended by Smith et al (2019)
We first compared the linear trends in the ALL multimodel ensemble mean (MMEM) to those in ERA5
Summary
YU-CHIAO LIANG,a CLAUDE FRANKIGNOUL,b,a YOUNG-OH KWON,a GUILLAUME GASTINEAU,b ELISA MANZINI,c GOKHAN DANABASOGLU,d LINGLING SUO,e STEPHEN YEAGER,d YONGQI GAO,e,f JISK J. MECKING,k TIAN TIAN,l AND YING ZHANGf,m a Woods Hole Oceanographic Institution, Woods Hole, Massachusetts b Sorbonne Université, CNRS/IRD/MNHN, UMR LOCEAN, Paris, France c Max Planck Institute for Meteorology, Hamburg, Germany d National Center for Atmospheric Research, Boulder, Colorado e Nansen Environmental and Remote Sensing Centre and Bjerknes Center for Climate Research, Bergen, Norway f Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China g Netherlands eScience Center, Amsterdam, Netherlands h National Research Council, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy i Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy j Department of Meteorology, University of Reading, Reading, United Kingdom k National Oceanography Centre, Southampton, United Kingdom l Danish Meteorological Institute, Copenhagen, Denmark m Climate Change Research Center, Chinese Academy of Sciences, Beijing, China (Manuscript received 22 July 2020, in final form 20 July 2021)
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