North Pacific oscillation's impact on Arctic sea-ice and North American hydroclimate

The North Pacific Oscillation/Western Pacific pattern (NPO/WP) is a major mode of variability in the Pacific basin (0°-85°N, 120°E-120°W) during the winter months (DJFM). Empirical orthogonal function analysis performed on wintertime sea level pressure (SLP) anomalies from both the NCAR/NCEP and ERA-40 reanalysis projects reveals the NPO as the second leading mode of SLP variability. This preliminary analysis suggests that the NPO mode of variability explains 15%-20% of the total variance within the SLP field. The reflection of the NPO in the upper troposphere, the WP pattern, is evident from regression of geopotential height anomalies on the principal components of SLP anomalies. The change in Northern Hemisphere circulation associated with the NPO/WP influences North American hydroclimate, specially, over the Pacific Northwest. The NPO/WP circulation anomalies moreover impact sea ice in both the Bering Sea and Sea of Oshotsk. The most up to date sea-ice observations from both in situ and satellite sources are being analyzed to quantify this impact. Weekly sea-level pressure and circulation is also being analyzed to understand NPO evolution. The obtained findings will be discussed in context of NAO evolution.