Atlantic Canada ocean temperatures set records again in 2022

Ocean temperatures in Atlantic Canada set record highs again in 2022, according to the latest assessment released by the federal Department of Fisheries and Oceans.

Results from the annual Atlantic Zone Monitoring Program show surface, intermediate and bottom temperatures were well above normal last year.

"It was widespread. It was everywhere," said Peter Galbraith, a DFO research scientist in Mont-Joli, Que. "It was really, really warm across the zone."

Fisheries and Oceans uses 45 indices — a combination of multiple indicators — to measure ocean conditions related to temperatures in the Gulf of Maine south of Nova Scotia, the Scotian Shelf, the Gulf of St. Lawrence and off Newfoundland and Labrador.

'Those are alarm bells'

The data is gathered using shipboard measurements, gliders, fixed and floating buoys and satellites.

In 2022, 43 indices were above normal and 16 were the highest ever recorded, DFO said in its report on oceanographic conditions posted this month.

"Those are alarm bells. It means pay attention and be careful," said Pierre Pepin, a biologist with DFO in St. John's.

"That's fundamentally what those things mean. And the degree to which that gets integrated into the decision-making process is still in development."

In the Gulf of St. Lawrence, multiple records were set in 2022.

Average sea surface temperatures in the gulf from May to November were the warmest since record-keeping began in 1981: 1.6 C above normal.

In August, surface temperatures again set 41-year records, averaging 18.2 C — which is 2.2 C above normal. In September, temperatures averaged 15.5 C, or 2.5 C above normal.

Galbraith called these variations "really huge."

September was also noteworthy because Hurricane Fiona churned up seas and lowered the surface temperatures by 6 C over a two-week period — yet those temperatures still reached new highs.

Century-old heat record set in 2015 surpassed

The gulf's summer cold intermediate layer — water below the surface left over from the previous winter — was the second warmest since tracking began in 1985.

Meanwhile, deeper water set high temperature records at 150, 200, 250 and 300 metres, crossing the 7 C threshold for the first time.

That is a full degree higher than in 2015, when a 100-year-old record was broken.

"Every year since 2015, it's been inching up," said Galbraith.

Warmer water originating from the Gulf Stream is now dominant in deeper layers and the deepest channels have seen large decreases in oxygen levels.

DFO says the St. Lawrence Estuary, from Quebec City to Pointe-des-Monts, Que., and the Gulf of St. Lawrence are both currently undergoing "significant changes" in chemical and biological conditions.

Climate-change trends

The DFO report states that surface waters in the Atlantic during ice-free months "have been mostly tracking climate-change driven warming trends in the atmosphere" and set records in the summer of 2022.

Bottom temperatures were substantially above normal across the zone, including record highs in the northern Gulf of St. Lawrence, off southern Newfoundland and on the Scotian Shelf.

"The thing that we're starting to see or at least that I'm starting to see in these data is that the one-offs are becoming a lot more frequent and when you have one-offs that become more frequent, it's an indicator of change," said Pepin.

"I think it's fair to say that there's a strong component of climate change in there."

Why warming is expected to continue

Warm water is expected to endure for years in the Gulf of St. Lawrence and Scotian Shelf, according to DFO.

The deep water sucked into the gulf from the Atlantic mixes well offshore.

It takes two years to get from the continental edge slope to the Laurentian Channel, two more years to reach the Cabot Strait between Newfoundland and Cape Breton and another three years to reach the inner estuary.

Galbraith said there's no sign yet of a dominating "blob" of colder water from the Labrador Current entering the mix.

Winners, losers and mackerel

"All we see is still warm water there," he said. "So there is no respite for the Gulf of St. Lawrence and Scotian Shelf. They're going to keep undergoing warm conditions for at least several more years."

This is potentially a change for the worse for some coldwater species like snow crab, which can tolerate a narrow thermal band, or northern shrimp — especially in portions of the gulf where oxygen levels have dropped with the arrival of warmer water.

"Warm waters are not the preferred environment for most of these species," said Pepin. "They tend to have lower productivity. They tend to have lower survival rates. They try to move out of very warm waters."

In the Gulf of St. Lawrence, DFO is reporting healthy halibut stocks and thriving lobster populations.

Responses to warming water can be misleading, Pepin said, pointing to the behaviour of mackerel "that basically follows warm water everywhere."

"You're going to see them more frequently. It doesn't necessarily mean that they're abundant in those areas. It means that you see them more frequently," he said. 

"And so it gives the impression that something has changed. But you have to be careful as to how you interpret those kinds of observations."