Boiling point? Canada’s warming oceans enter uncharted territory

Local Journalism Initiative
Tue, August 15, 2023 

Home to the longest coastline in the world, Canada is seeing a patchwork of superheating in all three oceans as global sea surface temperatures reached unprecedented heights in July.

There are entrenched hot spots of water in Canada’s Atlantic and Arctic oceans and temperatures are trending upwards in an alarming manner in the Pacific, months before seas typically reach peak warming at the end of August or September.

Increased marine warming due to human-caused climate change has been expected and documented for decades. But this summer’s extremes are bewildering, more severe and occurring faster than predicted, causing alarm in the scientific community, said Susanna Fuller, a vice-president at Oceans North.

“It’s absolutely pushing into uncharted territory,” Fuller said.

“We have predicted trends from a lot of modelling and long-term observations, but these new record highs kind of set a new baseline,” she said, noting a significant measure of uncertainty already exists when making climate predictions.

“When scientists say they are shocked and things are off the chart, it results in much more uncertainty ... how to manage and adapt [to climate impacts],” Fuller added.

Identifying the specific factors driving the most recent localized superheating in each of Canada’s oceans will require more investigation, but generalized impacts on ocean ecosystems are pretty well understood and the solution to mitigate or prevent them is crystal clear, she added.

“It all just underscores the incredible urgency of reducing greenhouse gas emissions. That's the most important thing we can possibly do,” Fuller said.

Sea surface temperatures across the entire North Atlantic had smashed records by June, with temperatures starting to climb on Canada’s East Coast in mid-July — regularly reaching 5 C above normal in the waters of Nova Scotia, the Gulf of St. Lawrence, and especially west of Newfoundland — which has been in the clutches of a severe marine heat wave for more than two weeks.

Temperature increases in Canada’s Atlantic are likely tied to atmospheric heat waves that are shattering heat records in Europe and elsewhere in the world and making it more difficult for the ocean to continue buffering the lion’s share of climate impacts, said Anya Waite, CEO of the Ocean Frontier Institute at Dalhousie University in Nova Scotia.

“It’s just evidence of extreme global warming, which is a concern at any point,” Waite said.

“This is just showing us that the heat has nowhere to go anymore.”

The ocean has absorbed nearly 90 per cent of the excess heat caused by greenhouse gas emissions in the past 50 years, more than half of which is stored in the top 700 metres of the ocean.

But current spikes in sea and air temperatures speed the melting of Arctic ice, increasing the flood of freshwater into the ocean that might be slow or even stop critical ocean currents in the North Atlantic, Waite said.

The exceptional water temperatures coincide with scientific debate over how fast a system of currents, the Atlantic Meridional Overturning Circulation (or AMOC), might be weakening as a result of climate change, with a recent study suggesting the possibility of its collapse as early as mid-century, she said.

The AMOC transports warm, salty water from the South Atlantic and tropics via the Gulf Stream to the colder North Atlantic. Typically, as freshwater is converted to ice, denser salty water sinks to the deep ocean to gather nutrients and is cycled, often over centuries, south again to rise and replenish oceans in warmer regions.

But research suggests that cycle has slowed over the course of the last half-century, Waite said.

The increased amount of buoyant freshwater in the Arctic and Atlantic oceans may be disrupting this vital cycling of incoming warm water to cooler depths.

“It can potentially interfere with that sinking [process] that's carrying all the heat into the deep ocean and saving us, in a way, from climate change,” she said.

The situation is also being aggravated by El Niño, Waite said.

The cyclical climate pattern in the Pacific Ocean taking place this year is predicted to cause more intense and disruptive weather worldwide. The climate pattern usually causes warmer and drier conditions in the northern United States and Canada and increased rainfall and storms in the southern states and South America.

El Niño, which typically reaches peak effect in late winter and early spring, will likely amplify the climate extremes of drought, fire and flood experienced across Canada. The Maritime provinces, especially Nova Scotia, were ravaged this year, she said.

“The warming ocean has huge impacts on our weather and it really can trigger both these torrential rains and drought that lead to more wildfires,” Waite said.

Approximately 40 per cent of the world’s oceans meet the threshold for a marine heat wave, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).

Marine heat waves involve sea surface temperatures that are higher than normal for at least five days.

The U.S. agency is forecasting up to half the ocean will reach the same state by September and likely stay that way until the end of the year.

Most of Canada’s southern Arctic waters and hot spots around Hudson Bay and Baffin Island have ranged between 4 C and 5 C above normal for much of the past month, according to Environment Canada’s sea and ice monitoring data.

Warm ocean temperatures speed up the melting of ice, which further compounds the warming, Fuller said. This contributes to the “Arctic amplification effect,” which means the polar region is heating up to four times faster than the rest of the globe, recent research shows.

“When there is no ice, the water is darker and absorbs sunlight more, which means it gets even warmer,” she said.

“So you get this feedback effect where the warmer the water gets, the faster the ice melts.”

The Arctic marine heat wave season has extended by nearly a month in the last two decades, research shows. These events increase over time and are more intense than other areas of the ocean and have powerful impacts on the Arctic ecosystem.

Arctic communities are particularly vulnerable because warming waters and loss of sea ice can harm the entire food web from plankton to whales and shift the range of animals and marine creatures that people hunt and rely on for food, such as Arctic char, belugas or seals, Fuller said.

Changes in weather from climate change also damage important infrastructure, like transportation networks, buildings and roads. Storm surge is a big problem for communities on the shores of the western Arctic, she noted.

The federal government recently allocated $54 million to prevent the shoreline of the Inuvialuit hamlet of Tuktoyaktuk from disappearing. Coastal erosion, flooding and permafrost thaw have caused a metre of shoreline to disappear annually, threatening homes and key community buildings like health centres and its college near the Mackenzie River delta in the Northwest Territories.

Communities in the Arctic also rely on ice and frozen permafrost to travel, hunt and ship supplies and their disappearance isolates and threatens people physically and culturally, Fuller said.

“Imagine if the 401 [highway] just disappeared and people couldn't get from community to community,” she said.

“We have Arctic communities that are facing almost catastrophic changes.”

A large marine heat wave lurking offshore for most of the spring arrived in early August on Canada’s West Coast and in Washington state and Oregon south of the border.

Temperatures at the ocean’s surface are as much as 4 C above normal, but still haven’t broken last year’s records, said Andrew Leising, a NOAA research oceanographer.

Marine heat waves in the Pacific Northwest are no longer uncommon in the summer and often have negative impacts on marine ecosystems, such as causing harmful algae blooms that can kill shellfish. Warm water can also push fish like salmon north in search of cold water and diminish the amount and quality of plankton, a key food for many marine species.

However, despite the current record-breaking global water temperatures and atmospheric heat waves, and the pending El Niño effect, it’s too early to tell if the infamous Blob will resurface in the Pacific, Leising said.

The Blob was a massive, prolonged and severe marine heat event that began in 2014 and lasted two years. It had cascading impacts on the ecosystem and food web, causing massive die-offs of salmon, seabirds, sea lions, kelp forests and sea stars. The resulting toxic algae blooms decimated shellfish along the Pacific and may have caused a spike in humpback whale fatalities.

“Blob-class” events last longer than standard marine heat waves and feature warm water at greater depths, Leising said.

“It wasn’t just at the surface,” he said. “In some places, it was warming the water down to 120 or 140 metres.”

And although the Blob was amplified by the effects of an El Niño year, it originated due to a long-lasting ridge of high pressure over the ocean that blocked waters from cooling over the winter.

“They called it the ‘ridiculously resilient ridge,’” said Leising, who runs a Blob Tracker website.

“There are a lot of similarities to the Blob years, but when you dig into the details of the atmospheric pattern and how it's evolving, it's a bit different right now.”

However, when El Niño reaches its peak next spring, it will be clearer if conditions are in place for a possible resurgence of the Blob, he said.

But the warmer ocean temperatures can have impacts on marine life, whether they are short- or long-term, he stressed.

“If I'm an animal or I'm a fish sitting off the coast of B.C., do I really care what’s causing all this warm water?” he asked.

“I don’t think I do. It’s warm water and I’m getting hit by it.”


Rochelle Baker, Local Journalism Initiative Reporter, Canada's National Observer