Impacts of Arctic sea ice on cold season atmospheric variability and trends estimated from observations and a multi-model large ensemble

Yu-Chiao Liang (1) , Claude Frankignoul (2, 1) , Young‐Oh Kwon (1) , Guillaume Gastineau (2) , Elisa Manzini (3) , Gokhan Danabasoglu (4) , Lingling Suo (5, 6) , Stephen Yeager (4) , Yongqi Gao (5, 7) , Jisk Attema (8) , Annalisa Cherchi (9, 10) , Rohit Ghosh (3, 11) , Daniela Matei (3) , Jennifer Mecking (12) , Tian Tian (13) , Ying Zhang (7, 14)

1 WHOI - Woods Hole Oceanographic Institution
2 VARCLIM - Océan et variabilité du climat
3 MPI-M - Max Planck Institute for Meteorology
4 NCAR - National Center for Atmospheric Research [Boulder]
5 NERSC - Nansen Environmental and Remote Sensing Center [Bergen]
6 BCCR - Bjerknes Centre for Climate Research
7 NZC - Nansen-Zhu International Research Center
8 Netherlands eScience Center
9 ISAC - CNR Institute of Atmospheric Sciences and Climate
10 INGV - Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Bologna
11 Department of Meteorology [Reading]
12 NOC - National Oceanography Centre [Southampton]
13 DMI - Danish Meteorological Institute
14 CAS - Chinese Academy of Sciences [Beijing]

To 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.

Mots clés: Arctic; Sea ice; Atmospheric circulation; Climate models

Domaines: Géophysique [physics.geo-ph]

Yu-Chiao Liang, Claude Frankignoul, Young‐Oh Kwon, Guillaume Gastineau, Elisa Manzini, et al.. Impacts of Arctic sea ice on cold season atmospheric variability and trends estimated from observations and a multi-model large ensemble. Journal of Climate, 2021, 34 (20), pp.8419-8443. ⟨10.1175/JCLI-D-20-0578.1⟩. ⟨hal-03608156⟩