Research Document 2020/030

Physical Oceanographic Conditions in the Gulf of St. Lawrence during 2019

By Galbraith, P.S., Chassé, J., Shaw, J.-L., Dumas, J., Caverhill, C., Lefaivre, D. and Lafleur, C.

Abstract

An overview of physical oceanographic conditions in the Gulf of St. Lawrence (GSL) in 2019 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 runoffs of the St. Lawrence River measured at Québec City and its combination with rivers flowing into the Estuary (RIVSUM II) were at their highest level since 1976. Sea-ice maximum volume was near normal, but the winter mixed layer volume was at a record high aided by the second largest inflow since 1997 of Labrador Shelf Water. The August cold intermediate layer (CIL) and the seasonally averaged minimum temperature index were near normal. Surface water temperatures were at a record low in September, but this was caused by strong vertical mixing from tropical storm Dorian rather than from heat loss to the atmosphere. The May to November average was below normal, but the warmest month of the year, August, was above normal. Deep water temperatures have been increasing overall in the Gulf since 2009, with inward advection from Cabot Strait. Gulf-wide average temperatures at 150 and 200 m are lower than the 2015 record highs but remain above normal at 3.3°C (+0.8°C, +1.6 SD) and 5.5°C (+1.0°C, +2.4 SD). New series record highs (since 1915) were set at 250 and 300 m, at 6.3°C (+1.0°C, +3.8 SD) and 6.5°C (+1.0°C, +6.6 SD) respectively. Bottom area covered by waters warmer than 6°C remained high in Anticosti Channel and Esquiman Channel and were at record highs in the northwest Gulf and Central Gulf.

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