Physical Oceanographic Conditions in the Gulf of St. Lawrence during 2021.

An overview of physical oceanographic conditions in the Gulf of St. Lawrence (GSL) in 2021 is presented as part of the Atlantic Zone Monitoring Program (AZMP). AZMP data as well as data from regional monitoring programs are analyzed 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 well below normal. The sea ice seasonal maximum volume was just shy of the series low record of 2010 and the January-April average was at a series record low. The winter mixed layer volume was second lowest of the 1996-2021 time series for waters colder than -1 °C and lowest for waters colder than 0 °C. The August cold intermediate layer (CIL) average minimum temperature was the highest of the 1985-2021 time series and the seasonally averaged minimum temperature index was the highest since 1980. On the Magdalen Shallows, the bottom area covered by waters cooler than 1 °C in August-September was at a record low. Sea surface temperatures (SST) averaged monthly over the Gulf were the highest of the satellite record (since 1981) in October and November. The May-November average SST for the Gulf was 3rd highest of the time series after 2006 and 2012. Deep water temperatures have been increasing overall in the Gulf since 2009, with inward advection from Cabot Strait. Gulf-wide average temperature has hit new series record highs (since 1915) of 4.1 °C at 150 m, 6.0 °C at 200 m, 6.7 °C at 250 m and 6.9 °C at 300 m. Bottom area covered by waters warmer than 6 °C was at a record high in all regions along the deep channels, with a notable increase in the Estuary. In the northeast Gulf, there was about the same bottom area between 6 °C and 7 °C as there was > 7 °C. [ABSTRACT FROM AUTHOR]