The Gulf of St. Lawrence is losing oxygen faster than anywhere else

Global warming has significantly altered the Earth's atmosphere. While the oceans in general have long suffered from low levels of oxygen, the Gulf of St. Lawrence is warming and losing oxygen faster than almost every ocean in the world. In a recent study, researchers investigated the causes of this rapid deoxygenation.

The Gulf of St. Lawrence is a large part of the ocean that drains the Great Lakes of North America and is home to an incredibly diverse marine ecosystem. The researchers suggest that the unprecedented drop in oxygen levels in the Gulf of St. Lawrence is attributed to two of the most powerful currents in the ocean: the Gulf Stream and the Labrador Current. Changes in these currents have caused Canada's invasion of the Gulf of St. Lawrence of water containing less oxygen.

"The decline of oxygen in this region has already been reported, but what has not been explored before was the underlying cause," said Principal Researcher Mariona Claret of the University from Washington, who did the work at McGill University. "The observations in the very interior of the Gulf of St. Lawrence show a dramatic decline in oxygen, which reaches hypoxic conditions, which means that it can not fully support marine life.

The Fisheries Agency of Canada has been monitoring the temperature and oxygen of the St. Lawrence region for decades, but the link between the two has never been considered.

To determine the causes of oxygen loss in the region and the role played by climate, the researchers used the NOAA geophysical fluid dynamics laboratory model results. The model results combined with historical observations have shown that the Gulf Stream has shifted north and that the Labrador Current has weakened due to high levels of carbon dioxide over the last century. As the level of carbon dioxide increases, Gulf Stream's hot, salty, and low-oxygen water penetrates the deepest parts of the Gulf of St. Lawrence. Since hot water retains oxygen less effectively, it results in increased loss of oxygen. The movement of ocean circulation on a large scale causes warming and deoxygenation in the Gulf of St. Lawrence.

"We report a change of oxygen on the coast to a change in large-scale currents on the high seas," Claret said. "Being able to potentially associate coastal changes with the southern tilt of the Atlantic is very exciting.