Research Document - 2015/032

Physical Oceanographic Conditions in the Gulf of St. Lawrence in 2014

By P.S. Galbraith, J. Chassé, P. Nicot, C. Caverhill, D. Gilbert, B. Pettigrew, D. Lefaivre, D. Brickman, L. Devine, and C. Lafleur

Abstract

An overview of physical oceanographic conditions in the Gulf of St. Lawrence in 2014 is presented as part of the Atlantic Zone Monitoring Program (AZMP). AZMP data as well as data from regional monitoring programs are analysed and presented in relation to long-term means. The annual average freshwater runoff of the St. Lawrence River measured at Québec City and its combination with rivers flowing into the Estuary (RIVSUM II) were above-normal in 2014 (+0.7 SD and +1.1 SD respectively), as was the spring freshet (+1.9 SD and +1.8 SD). The above-normal spring freshet led to below-normal Estuarine ratio and near-normal outward transport at the Pointe-des-Monts section. The cold winter of 2014 created a thick surface mixed layer over the GSL with near-freezing temperatures, as well as a sea ice cover with the third highest seasonal maximal volume since 1969, at nearly double the climatological average. The August-September cold intermediate layer (CIL) returned to near-normal conditions after 4 years of warm conditions, as a result of the cold winter. The sea-surface temperature averaged from May to November over the Gulf was above-normal by +1.2°C, the second highest on record after 2006. A record high was reached in August with a Gulf-average anomaly of +2.5°C, breaking the +2.0°C record of August 2012. Record August highs were also set in the following regions: Estuary (+4.2°C, +4.4 SD), Northwest Gulf (+4.1°C, +4.4 SD), Anticosti Channel (+2.8°C, +3.2 SD) and Cabot Strait (+2.9°C, +3.2 SD). Deep water temperatures are increasing overall in the Gulf, with inward advection from Cabot Strait where temperature had reached a record high (since 1915) in 2012 at 200 m. Temperature averaged over the Gulf at 200 m increased overall to reach 5.3°C, the highest on record. Temperature at 300 m increased slightly in 2014 to reach 5.9°C, the highest value since 1980. Bottom area covered by waters warmer than 6°C increased in 2014 in Anticosti Channel, Esquiman Channel and Central Gulf, and reached a record value in Esquiman Channel while reducing its bottom habitat area in the temperature range of 5–6°C.

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