Research Document 2017/044

Physical Oceanographic Conditions in the Gulf of St. Lawrence in 2016

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

Abstract

An overview of physical oceanographic conditions in the Gulf of St. Lawrence (GSL) in 2016 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 was normal and its combination with rivers flowing into the Estuary (RIVSUM II) was about above-normal  in 2016 (+0.5 SD and +0.6 SD respectively). The mild early winter of 2016 created a surface mixed layer that was not near-freezing over the entire Gulf, and led to the third lowest sea ice cover maximum volume since 1969. The August cold intermediate layer (CIL) showed warmer than normal minimum temperature (+1.4 SD) and less than normal volume colder than 1°C (-2.1 SD). Sea-surface temperatures averaged over the Gulf were near normal or above normal from May to November 2016, leading to an above-normal May-November average (+0.6°C, +0.9 SD). The May to November average was however at a record high (since 1985) for the Estuary (+1.4°C, +2.4 SD). Record highs were reached in November averaged over the Gulf (+1.7°C, +2.2 SD) and in the following regions: Estuary (+1.8°C, +2.2 SD), Northwest Gulf (+1.9°C, +2.1 SD), Esquiman Channel (+2.5°C, +2.2 SD), Cabot Strait (+2.2°C, +2.5 SD), and Magdalen Shallows (+2.0°C, +2.5 SD). The timing of summer warming onset and fall cooling were normal. Deep water temperatures have been 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 depths of 250 and 300 m were at record highs in 2016 at 6.1 and 6.2°C respectively. The bottom area covered by waters warmer than 6°C finally decreased in 2016 in Anticosti Channel and Esquiman Channel, but increased sharply in Central Gulf and made its first appearance in the northwest Gulf.

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