Investigation of the atmospheric mechanisms related to the autumn sea ice and winter circulation link in the Northern Hemisphere
The relationship of Barents–Kara sea ice concentration in October and November with atmospheric circulation in the subsequent winter is examined using reanalysis and observational data. The analyses are performed on data with the 5-year running means removed to reduce the potential effects of slowly-varying external driving factors, such as global warming. We show that positive (negative) Barents–Kara sea ice concentration anomaly in autumn is associated with a positive (negative) North Atlantic Oscillation-like (NAO) pattern with lags of up to 3 months. The month-to-month variations in the lag relationships of the atmospheric anomalies related to November sea ice concentration are presented. Further analysis shows that the stratosphere-troposphere interaction may provide the memory in the system: positive (negative) sea ice concentration anomaly in November is associated with a strengthened (weakened) stratospheric polar vortex and these anomalies propagate downward leading to the positive (negative) NAO-like pattern in the late December to early January. This stratosphere mechanism may also play a role for Barents–Kara sea ice anomaly in December, but not for September and October. Consistently, Eliassen-Palm, eddy heat and momentum fluxes suggest that there is strong forcing of the zonal winds in November.
KeywordsClimate impact of Arctic sea ice Sea ice-atmosphere interaction North Atlantic Oscillation Stratosphere downward propagation
The NCEP-NCAR Reanalysis data are provided by NOAA/OAR/ESRL PSD, Boulder, Colorado, USA (http://www.esrl.noaa.gov/psd). The sea ice concentration (Cavalieri et al. 1996) data are from the National Snow and Ice Data Center, USA. The work was supported by the GREENICE project, funded by the NordForsk Top-level Research Initiative (Project no. 61841). We acknowledge fruitful discussion with Hisashi Nakamura and Javier Garcia-Serrano on this study. We thank the two reviewers for their comments which had led to improvements of this paper.
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