The Warm-Arctic/Cold-continents pattern during 1901-2010

The Warm-Arctic/Cold-continents (WACC) winter weather pattern is investigated using the European Centre for Medium-Range Weather Forecasts 20th Century reanalysis data (ERA20C) spanning 1901-2010. Both the 1920-1940 and 1990-2010 periods are characterized by Arctic amplification (AA) and mid-latitude continental cooling, although the Arctic warming signal for 1990-2010 is twice as strong as that for 1920-1940. Significant weakening in the mid-latitude polewards temperature gradient and zonal wind, wavier upper-level flow character, and strong regional blocking frequency/intensity changes are also detected during both AA periods. These results based on statistical analyses highlight the possible role of AA in affecting mid-latitude weather patterns, but further work is needed to quantify the influence of AA on particular mid-latitude dynamical features.