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Research Document - 2014/070

Meteorological, Sea Ice and Physical Oceanographic Conditions on the Scotian Shelf and in the Gulf of Maine during 2013

By D. Hebert, R. Pettipas, D. Brickman, and M. Dever

Abstract

In 2013, the North Atlantic Oscillation index was below the 1981-2010 mean (-3.4 mb, -0.4 SD [standard deviation]) after having a positive anomaly last year and three years after its record low. Mean annual air temperature anomalies were from +0.1oC (Saint John, New Brunswick) to +0.8oC (Sable Island, Nova Scotia), +0.2 to +1.1 SD, above normal in 2013 but lower than those observed in 2012. There has been very little ice on the Scotian Shelf from April 2009 until the end of the season in May 2013. The ice volume during 2013 was the seventh lowest in the 52 year long record. Years 2010, 2011 and 2012 had the second to fourth lowest coverage and volume. Positive sea surface temperature (SST) anomalies prevailed throughout the region during 2013, with representative values of about +0.4 to +1.2oC (+0.4 to +1.5 SD). Long-term coastal monitoring sites at St. Andrews (New Brunswick) and Halifax (Nova Scotia) recorded annual SST anomalies of +1.0oC (+1.7 SD) and -0.04oC (-0.05 SD), respectively, in 2013, and +1.0oC below those observed in 2012, at both sites. At selected sites across the region, annual water temperature anomalies were positive in 2013: +0.1oC (+0.2 SD) for Cabot Strait 200-300 m depth range, +0.2oC (+0.4 SD) for Misaine Bank at 100 m, +0.6oC (+0.7 SD) for Emerald Basin at 250 m, +1.0oC (+1.3 SD) for Lurcher Shoals at 50 m, and +1.1oC (+0.9 SD) for Georges Basin at 200 m (the warmest year in the last 64 years). Bottom temperature anomalies in Northwest Atlantic Fisheries Organization areas 4VWX were all positive in 2013 and ranged from +0.2oC (+0.5 SD) in 4Vn to +1.0oC (+1.5 SD) in 4X. Average stratification on the Scotian Shelf strengthened slightly compared to 2012 and was the third strongest in the record. Since 1948, the stratification has slowly been increasing on the Scotian Shelf due mainly to a freshening (45%) and warming (35%) of the surface waters. A composite index consisting of 18 ocean temperature time series from surface to bottom across the region indicated that 2013 was the eighth warmest of 44 years, with an averaged normalized anomaly of +0.9 SD relative to the 1981-2010 period.

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