Atlantic wolffish and cod and Greenland halibut are at risk of slow suffocation as climate change drives oxygen depletion in the cold waters off eastern Canada, one of the world’s richest fishing grounds, a team of oceanographers reports in the journal Nature Climate Change.
“Observations in the very inner Gulf of St. Lawrence show a dramatic oxygen decline, which is reaching hypoxic conditions, meaning it can’t fully support marine life,” said lead author Mariona Claret of the University of Washington. “The oxygen decline in this region was already reported, but what was not explored before was the underlying cause.”
The researchers linked the “dramatic drop” in dissolved oxygen levels to shifts in the Gulf Stream and the Labrador Current, driven by “ever higher ratios of carbon dioxide in the atmosphere,” Climate News Network reports. “As carbon dioxide and other greenhouse gas levels have risen in the past 100 years, the Gulf Stream has shifted northward, and the Labrador Current has weakened,” with the result that “more warm, salty, and oxygen-depleted water from the Gulf Stream is getting into one of the world’s great waterways.”
Cod and halibut are “two of the world’s most prized commercial catches,” Climate News Net notes.
Fisheries officials in Canada “have been measuring the salinity and temperature in the St. Lawrence seaway since 1920, and oxygen levels since 1960,” adds correspondent Tim Radford. “The latest study finds that the changes there have been more than twice the average change of 2% measured for the Atlantic and the oceans as a whole.”
The scientists caution that the computer simulation on which they based their conclusions may have delivered a “very conservative picture” of the actual problem, Radford adds, and that the situation in the Gulf could eventually influence oxygen variability in the open North Atlantic Ocean.