After record heat in July, mercury reached a historic high in September in the waters of the Gulf of St. Lawrence.
What we are currently experiencing is completely disproportionate. The water is 5.2°C warmer than it should be, warns Peter Galbraith, a scientific researcher in physical oceanography at the Maurice Lamontagne Institute.
While the surface water temperature of the Gulf of St. Lawrence is expected to be around 6°C in September, the mercury temperature reached 11°C, according to satellite measurements – a high usually reached in early August.
In July, the Gulf of St. Lawrence reached record temperatures across eastern Quebec. From Gaspésie to the north coast, surface waters have exceeded normal temperatures by three degrees. However, the situation deteriorated in September in the Gulf and the St. Lawrence Estuary as well as in Chaleur Bay.
Normally the curve [de température] drops after peaking in July, but this year the temperature has remained about the same, says Peter Galbraith.
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Peter Galbraith compares the estuary to a “refrigerator” that is said to contain the coldest water of the St. Lawrence. (archive photo)
Photo: Radio-Canada / Julie Tremblay
A heat wave occurs when the temperature exceeds the 90th percentile for five days. Last summer the heat wave lasted a month.
In forty years of data, 2023 is the hottest year on record. Second is 2021, recalls Mr. Galbraith.
Impact on marine life
The warming of water has concrete effects on the behavior of various marine species such as lobsters and shrimps, where we observe changes in their movements.
While Gaspé lobstermen reported a season of plenty, the situation in the United States is quite different.
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Catches are rising as fishermen feared the worst after the start of the season was delayed by poor weather conditions. (archive photo)
Photo: Radio-Canada / René Godin
The southernmost lobster populations have declined because the water there is probably too warm.
The northern shrimp is another species whose environment is changing. It swims in water that is deeper than the lobster, between 150 and 350 meters deep, where the water temperature breaks centuries-old heat records.
Result: Shrimp are disappearing from the estuary and the Gulf of St. Lawrence. Biomass levels are the lowest since 1990.
Canada’s Department of Fisheries and Oceans is even considering a possible closure of the shrimp fishery, in whole or in part.
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The shrimp fishery will decide its fate at the end of October. (archive photo)
Photo: Radio-Canada
For other marine life, it depends on their life cycle. When organisms spawn on the surface, they are affected, but organisms that can swim a few meters would escape, the researcher describes.
Will ice cover the St. Lawrence River this winter?
While temperature increases remain worrisome, there is no way to predict what the condition of the Gulf of St. Lawrence ice will be next winter.
It is still too early to make a prediction, says Peter Galbraith.
Instead, we have to wait for the weather forecast for the month of December to know if the river will be covered with ice.
Ice cover could come sooner if a polar vortex arrives in December, scientist says.
According to Denis Leduc