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Current status of the Bering Sea ecosystem
It was cold once again this past winter, but not as cold as in the most recent years (2009 and 2010). There were also signs that the weather may become more moderate in the near future. In some ways, the conditions during the winter of 2010/2011 were similar to 2006 (an average temperature year), although sea ice persisted later in 2011, and it was slightly colder than in 2006 (Fig. 1). During the winter of 2010/2011, sea ice extended to mooring M2 (56.87°N, 164.030W), but was not solid (7/10 cover), and the front moved back and forth across the mooring (north and south) until April when the ice retreated. Unlike the spring of 2010, there were no sustained northerly winds in 2011 that retained ice on the middle shelf. By the end of May 2011, the ice front had retreated to St. Matthew Island. In early June, the ice cover was 2-4/10 north and west of St. Lawrence Island and 4-6/10 north and east of the island (Fig. 2). The late spring sea surface water temperatures in the southeastern Bering Sea were moderate to cold: 4-5°C over the outer shelf and 2-3°C over the middle shelf (not shown).
There have also been some changes in the coupled oceanatmosphere systems that drive the North Pacific and marginal seas. For example, the Pacific Decadal Oscillation (PDO; 1st mode of the EOF on sea surface temperatures) changed from positive to negative in June 2010, and was moderate to strong from June to January, weakening in early 2011. On the equator, La Niña conditions weakened, and the ENSO (El Niño Southern Oscillation) index was expected to be neutral this summer. The multivariate ENSO index is still negative and has been strongly negative since July/ August of 2010.
An important question to ask is - what will be the fate of the run of cold winter/spring conditions that began in 2007 and followed a string of very warm years from 2000 through 2005? The winter/spring...