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Research Document - 2004/061

Physical Oceanographic Conditions in the Gulf of St. Lawrence in 2003

By Gilbert, D., Galbraith, P.S., Lafleur, C., Pettigrew, B.

Abstract

An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2003 is presented. Air temperatures and surface water temperatures were below normal in winter and above normal in the fall. During winter 2003, sea ice coverage within the Gulf was about 10% above the long-term mean, the first year above normal since 1995. But of more significance, a record amount of ice was advected out of the Gulf through Cabot Strait during winter 2003, and the total volume of ice formation in the Gulf was much higher than normal. Moreover, the inflow of water through the Strait of Belle Isle in the northeast Gulf was by far the largest one observed over the 9-year period of helicopter CTD surveys conducted in March. This inflow of cold and salty water from Belle Isle Strait together with the large amount of ice produced in the Gulf in the winter of 2003 caused a huge increase in the summertime thickness and volume of T < 0°C waters (+300%) and T < 1°C waters (+40%) relative to 2002. This was accompanied by a 0.65°C drop in the cold intermediate layer minimum temperature index which is now 0.54°C below the 1971-2000 normal conditions and the fifth coldest in 57 years. The annual mean runoff of the St. Lawrence River at Québec City was 13.4% below normal. This led to above normal surface salinities and below normal surface layer stratification during most of 2003. In the 30-100 m layer, the 2003 temperature was colder than normal while salinity was higher than normal. In the 100-200 m layer, the 2003 temperature was colder than normal but salinity was close to normal. Finally, in the 200-300 m layer, both temperature and salinity were close to normal. The 2003 annual mean oxygen concentration in the bottom waters (≥ 300 m) of the Lower St. Lawrence Estuary (18.3% saturation) was the second lowest ever observed.

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