J3.5 Connections Between the Spring Pacific-Arctic Dipole and Summer Sea Ice in the Beaufort-Chukchi Seas

Wednesday, 25 January 2017: 9:30 AM
605 (Washington State Convention Center )
Will Perrie, Bedford Institute of Oceanography, Dartmouth, NS, Canada; and M. Zhang and Z. Long

We identified an atmospheric circulation dipole anomaly in the Pacific-Arctic sector and showed that it is related to the sea ice in the Beaufort-Chukchi Sea, in the following September. These results are obtained using sea ice observations and model-generated data from PIOMAS (Pan-Arctic Ice-Ocean Modeling and Assimilation System), and the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis. This dipole anomaly, which we denote as the Pacific-Arctic Dipole (PAD), is the second leading EOF mode of spring (April-June) sea level pressure (SLP) in the Pacific-Arctic (600N-900N, 1200E-1200W) and it accounts for 21.6% of the variance. The PAD anomaly has a positive anomaly in the Beaufort Sea and a negative anomaly extending from East Siberia to Northwest America, and exhibits co-variance with the Beaufort High and the Aleutian Low. The dipole mode reflects the re-distribution of cyclones in the Pacific-Arctic sector, which are modulated by the co-variance between the Arctic Part of North Pacific Trough and the northwestern America ridge of the upper atmospheric steering flows. We found that the spring PAD accounts for about 20% of the interannual variance of the following summer sea ice concentration (SIC) in the Beaufort-Chukchi Sea. A positive PAD has an enhanced Beaufort high and an intensified, northward extended Aleutian Low; the resulting intensified eastern winds in the Beaufort Sea lead to enhanced ice advection and weakened sea ice thickness. Moreover, less cyclone activity leads to less mid-tropospheric level cloud cover and less water content in the atmospheric column above the Beaufort Sea and Central Arctic, which causes a net surface heat flux gain and further reductions in sea ice. With climate change, the tendency for increased thinning of the sea ice and intensified easterly winds, lead to the earlier spring ice melt and open water formations along the coast; in turn, these processes foster a stronger summer ice-albedo feedback, resulting in accelerated reductions in sea ice in the following melting summer season.
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