Effects of warmer Atlantic Ocean now being felt in northern Manitoba, experts say

The warming climate is causing renewed concern in northern Manitoba, as a marine heat wave that hit the Atlantic Ocean last summer could lead to Manitoba’s northern port having one of the earliest ice-free dates on record.

“I’ve been working up here for 40 years now and it’s noticeable just how much that things have changed,” said Andrew Derocher, a biological sciences professor with the University of Alberta who works in Churchill, Man., on the shore of Hudson Bay.

“This has been an unusual year,” he said. “The ice has been quite light for large parts of the winter period. It was a bit slow to form, and we had some very warm water in Hudson Bay in 2023.”

Data from Polar Bears International, an advocacy and research group, shows southern Hudson Bay has been losing five days of sea ice cover per decade. The ice breakup date has also come earlier every year since 2020. 

Last year, the ice on southern Hudson Bay broke up on June 25.

A graph with a red line, labelled "ice-free days," trending upward and a blue line, labelled "day of the year," trending downward.
Data from Polar Bears International shows the number of ice-free days per year, in red, and the day on which ice broke up each year, in blue, in southern Hudson Bay. (CBC)

Sea ice data showed open water in parts of Hudson Bay as early as mid-April this year.

Though the full spring breakup hasn’t happened yet, all signs point to an earlier breakup this year. Exactly when that happens, and its impacts, remain to be seen.

Unprecedented sea temperatures off the Atlantic coast last summer led to a warmer ocean and fewer icebergs off the coast of Newfoundland and Labrador this year.

Fisheries and Oceans Canada previously said sea surface temperatures last summer measured almost seven degrees above normal in the Atlantic — the highest temperatures measured since 1982.

Derocher said the effects of that warmer ocean water are now being felt in northern Manitoba.

“It’s really quite clear that there are large areas of quite thin ice,” he said. “It’s not the best habitat for seals, and it’s not the best habitat for bears.” 

Potential for bad year: prof

Alex Crawford is an assistant professor in the department of environment and geography at the University of Manitoba.

He is currently studying the region’s ecosystem and the impacts of a marine heat wave — a period of unusually warm temperatures in the ocean, generally defined as five or more consecutive days when surface waters are in the uppermost 10 per cent of historical temperatures.

“We are set up to have a really, really potentially bad year” due to the Atlantic heat wave, said Crawford.

WATCH | Warmer ocean could mean fewer icebergs on the shores of Newfoundland:

Where are the icebergs? Newfoundland to see fewer this season

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Duration 1:48

A warmer ocean this year means less sea ice and fewer icebergs will likely show up on the shores of Newfoundland, and that’s impacting tourism and businesses. Experts say this could be more common for future iceberg seasons.

Plant life can act like an early warning system, he said. It’s too early to know this season what effect the heat wave may have on plant life in northern Manitoba, but that’s one of the things Crawford is watching for.

“Seagrasses are one of these kind of foundational plants that you can find in various ecosystems around the world.… There have been in the past massive die-offs of eelgrass,” he said.

“You might not care about grass, but guess what? A lot of the other organisms that live in those regions depend on that eelgrass.”

The gradual environmental change in the region could also have a major impact on one of the world’s most famous polar bear populations, warns Polar Bears International.

It has been tracking the loss of sea ice and shorter seasons for decades. Geoff York, the group’s senior director of conservation and policy, said because of the shorter season for sea ice, Hudson Bay’s bears now spend far longer on land than their ancestors did. 

“It’s a month longer on shore than their grandparents would have spent,” said York. “That’s mostly a key month of the season when they’re out catching young ring seals in the spring and early summer.” 

Desrocher said spending more time ashore during the year will be harder on the bears in the long run. 

WATCH | Polar bears spend more time on land as sea ice thins:

Hudson Bay ice feeling impact of marine heat wave

53 minutes ago

Duration 3:07

Polar bears could be spending more time on land this year as Hudson Bay sea ice thins due to a marine heat wave in the Atlantic Ocean.

“They’re burning up about a little over a kilogram of body mass per day when they’re not feeding. There’s not enough here on land to feed them,” he said.

“So if you add another month of ice free time, that means they’ve got to come ashore with an extra 30 kilograms of fat and muscle to live that period and at some point.”

If the ice-free period keeps growing, “we no longer get successful reproduction and we start to see increasing mortality” for the bears, said Desrocher. 

York said while it may seem like a problem isolated to Hudson Bay’s ecosystem, the warming climate causing sea ice loss isn’t limited to the Arctic.

“The Arctic also acts, in a sense, as the Earth’s air conditioning unit, if you want to look at it that way,” said York. “So as that AC unit starts to fail, that’s not great for the rest of us.”

Despite the thinner ice pack, the bear population appears to be faring well so far this year, said York.

“We’ve seen some really fat happy bears out on the ice,” he said.