'Unprecedented' marine heat wave hits Canada's East Coast this summer

The Atlantic Ocean off Canada's East Coast experienced an "unprecedented" marine heat wave this summer. 

Surface temperatures reached record highs throughout the region — including a huge weeklong spike off Newfoundland that averaged 6.7 C above normal.

Fisheries and Oceans climate scientist Peter Galbraith compiled the data for the World Meteorological Organization, a United Nations agency that monitors extreme weather events around the planet. 

Environment and Climate Change Canada submitted the data to the agency in September.

Galbraith compared sea surface temperatures that have been measured by satellite since 1982.

"In terms of what we have recorded, it's unprecedented," Galbraith told CBC News. "We just don't have anything close to that in our data record."

Marine heat waves are periods of unusually warm temperatures in the ocean. They are generally defined as five or more consecutive days when surface waters are in the uppermost 10 per cent of historical temperatures.

The month-long Atlantic event took place during the last three weeks of July and the first week of August.

Galbraith averaged the temperatures from the Scotian Shelf, Gulf of St. Lawrence, the Newfoundland Shelf and the Labrador Shelf.

In July, the ocean surface was two to four degrees above normal — the warmest in the 41 years that satellite data has been collected.

Galbraith said that off Newfoundland's Flemish Cap, where the surface temperature is normally 12 C, it was 18.6 C.

"Anything over like 1 degree Celcius is already off normal. So 6.5 degrees is the largest single weekly anomaly for a fairly large area in the whole satellite record for our Eastern Canadian waters," he said. "It's a huge difference"

Galbraith has been monitoring ocean conditions in the Gulf of St. Lawrence and the Atlantic Ocean for many years.

"I was surprised by the spatial extent of it. Usually part of the Atlantic zone is warm, but not all of it. And this was spreading across the whole zone," he said.