'Everything about the Gulf of St. Lawrence was warmer in 2021': federal scientist

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Warming ocean temperatures — especially in deep water — set more records in the Gulf of St. Lawrence in 2021, according to climate data released Tuesday by the Department of Fisheries and Oceans.

"Everything about the Gulf of St. Lawrence was warmer in 2021," said federal research scientist Peter Galbraith, based at the Lamontagne Institute in Mont-Joli, Que.

Galbraith and other DFO scientists released data on physical conditions in the gulf, measuring temperatures, salinity, water flow and ice cover in 2021.

Average sea surface temperatures in October and November were the highest since remote sensing data started 40 years ago.

DFO researchers recorded temperatures of 4.1 C at 150 metres, 6 C at 200 metres, 6.7 C at 250 metres and 6.9 C at 300 metres. Those were the highest readings since data collection began in 1915.

Across the gulf, the bottom area along deep channels covered by waters warmer than 6 C was at a record high, with a notable increase in the estuary. The estuary is the innermost part of the Gulf of St. Lawrence, where the St. Lawrence River enters into the gulf.

A cold intermediate layer from 50 to 150 metres — which usually stays cold in summer — was also the warmest in the 40-year record.

And perhaps most dramatic is a warming trend in deeper water between 150 and 300 metres.

"2015, 2016 was the first year where it was higher than any year prior and every year since we've beaten that last year's record. So we're at really 100-plus year record highs," Galbraith said after a briefing on 2021 conditions.

Increase in deep water temperature outpaces climate change

Galbraith said warming in the deeper water in the gulf has outpaced projections based on climate change.

"Our surface warming that we've observed falls in line with global warming of about one degree per 100 years," he said. "But in the deep layers, it's been one-and-a-half degrees in 12 years."

The last year with below-normal temperatures at 300 metres depth was in 2009. Since then, they have risen steadily.

More warm water out there

Galbraith predicted the situation is likely to continue as deep water from the continental shelf that slowly flows into the gulf and diffuses is also very warm.

That flow is a mix of warmer Gulf Stream water moving north and colder water moving south in the Labrador Current.

Galbraith said the Gulf Stream has become dominant but it's not clear whether this is a permanent event.

"I don't think we understand the dynamics of the water going around the Grand Banks well enough to know for certain they're never going to come back on."

In the meantime, "all we're seeing is still more and more warm water and we don't really expect any cooling."

Habitat changing

So far, some parts of the gulf — such as the Magdalen Shallows — remain cool enough for important commercial species like snow crab, while the deep water habitat is being affected in the northern gulf.

The thermal range for northern shrimp is compressing, which may force them further up the water column.

The changing habitat is important for species whose lifecycle is tied to seasons that may now be shorter or longer and warmer.

"If the warming happens too soon or too late, it'll change the favoured temperature for this egg for whatever species that is," said Galbraith. "Small things tend to have big impacts that we hadn't even thought of a while ago."

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