, ,
, ,
, ,
We identified an atmospheric circulation dipole anomaly in the Pacific-Arctic sector and we showed that it is related to the following September sea ice in the Beaufort-Chukchi Sea, 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. The dipole anomaly 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% of the variance. This dipole anomaly, which we denote as the Pacific-Arctic Dipole, has a positive anomaly in the Beaufort Sea and a negative anomaly extending from East Siberia to Northwest America, and it exhibits co-variance with the Beaufort High and the Aleutian Low. The dipole mode also reflects the re-distribution of cyclone activities in the Pacific-Arctic sector, with fewer cyclones in the Beaufort Sea and central Arctic and more cyclones in the subpolar Pacific. We also define a cyclone activity dipole index using the difference between the cyclone system density in the Arctic (700N-900N, 900E-600W) and that in the subpolar Pacific (500N-600N, 1500E-2100W), which is highly correlated with the time series of the Pacific-Arctic Dipole. We found that the spring Pacific-Arctic Dipole accounts for about 20% of the interannual variance of the following summer SIC in the Beaufort-Chukchi Sea. A positive Pacific-Arctic Dipole has an enhanced Beaufort high and the resulting intensified eastern winds in the Beaufort Sea lead to enhanced ice advection and weakened sea ice thickness. Ice is advected into warm Alaskan coastal waters which results in extensive melting. Moreover, less cyclone activity leads to less middle level cloud cover and less warm air advection in the Beaufort Sea and central Arctic, which causes a net surface heat flux gain, resulting in further reductions in sea ice.