Linking July Sea Ice Concentration Anomalies in Hudson Bay to Inter-annual and Multi-decadal Variability of North Atlantic Sea Surface Temperatures

A new atmospheric teleconnection pathway is presented that links variability in fall North Atlantic sea surface temperatures (SST) to sea ice concentration (SIC) anomalies in Hudson Bay the following July. The loss of summer sea ice cover in Hudson Bay over the past three decades is amongst the greatest of any region in the Northern Hemisphere (~20% per decade). Identifying links between SIC in this region to large-scale climate variability could yield insight into the potential cause of this dramatic decline. Co-variability between July SIC data from the Canadian Ice Service regional ice charts and North Atlantic SST data from HadISST1.1, is explored over the 1971 to 2005 period using Canonical Correlation Analysis. An atmospheric teleconnection pathway is elucidated by correlating the dominant canonical correlation time-series with atmospheric data from the NCEP Reanalysis project. It is found that 54% of the variability in July SIC is explained by fall SST anomalies in the North Atlantic. A strengthening (weakening) of the climatological ridge in 850mb north-west of Hudson Bay during winter, in response to fall North Atlantic SST anomalies, enhances (weakens) the dominant northwesterly winds that keep ice thin along the northern coast of Hudson Bay and Hudson Strait and advect cold air over the rest of the bay promoting ice growth. The resulting winter anomalies in ice thickness manifest as SIC anomalies in July. An interesting implication of the teleconnection pathway identified in this study is that if the multi-decadal signal in North Atlantic SST, known as the Atlantic Multi-decadal Oscillation (AMO), returns to a cool phase there could be some recovery in early summer sea ice cover in Hudson Bay.