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THE QUEBEC REGION BULLETIN
JUNE - JULY 2010/VOLUME 13/NUMBER 3
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THE GULF OF ST. LAWRENCE
UNUSUALLY WARM
March 2010 sampling team. March 2010 sampling team. The probe used for the survey is in the middle of
the group.

DFO  M. Samson

The Gulf of St. Lawrence experienced a particularly mild winter in 2010. The air temperatures, which were recorded at nine stations situated near the Gulf, were the hottest on record since 1945 (year one for this series of data), that is, 5.1°C above normal temperatures. Sea ice was also all but absent in the Gulf; the Canadian Ice Service registered the least extensive ice coverage since it started collecting data in 1969.

This climate context formed the backdrop of the annual helicopter-based survey of the physical oceanographic conditions, conducted in March 2010. For the last 15 years, this survey has been carried out every winter using a Canadian Coast Guard Bell 212 helicopter. While the helicopter hovers 30 to 50 metres over the water, a probe is lowered as deep as 200 metres into the water to measure the temperature and the salinity at more than 85 test sites in the Gulf of St. Lawrence.

The physical oceanographic conditions of the winter mixed layer were exceptionally warm in March 2010; this was the first helicopter-based survey to produce such results. The figure shows the temperature of the surface mixed layer for the March 2010 survey together with the results of the March 2009 (a typical year) survey for comparison. Usually, the temperature of the winter mixed layer nears the freezing point virtually everywhere in the Gulf. However, in March 2010, this layer was on average 1°C warmer than usual; temperatures were even higher in certain areas (upwards of 0°C north-east of the Cabot Strait and in the Estuary).

Surface water temperatures, March 2009 and 2010 surveys

Surface water temperatures, March 2009 and 2010 surveys

The core temperature of the cold water beneath the winter surface layer affects water temperatures throughout the year, sometimes keeping the water below 0°C at the height of summer. The warmer-than-normal water temperatures recorded in March 2010 mean that the core water temperatures expected in summer 2010 will be the warmest ever recorded in 30 years


Peter Galbraith
Science