An Observational Estimate of the Direct Atmospheric Response to the Arctic Sea Ice Loss

The response of the cold season atmospheric circulation to the Arctic sea ice loss is estimated from observed sea ice concentration (SIC) and an atmospheric reanalysis. This is done by first estimating the lag relations at the interannual time scale between the atmosphere and the amplitude of the pan-Arctic SIC patterns that characterize the sea ice loss in each calendar month. No large-scale field significant relationship is found in October and November, but a negative NAO/AO-like signal is seen from December to February and, less significantly, March. The signal is field significant in the stratosphere and upper troposphere in December, but only in the troposphere thereafter, suggesting downward propagation. If no concomitant variability in sea surface temperature or snow cover anomalies is found, the lag relationships are attributed to SIC forcing; otherwise the response to the interannual SIC fluctuations is established by multivariate analysis. The response is then used to estimate the direct atmospheric response to the sea ice loss during 1979-2016.