Already one of the fastest-warming bodies of water in the world, the Gulf of Maine recorded its second-hottest year ever in 2022, another ominous indicator of how global warming threatens the rich marine world off New England.
The Gulf of Maine Research Institute reported recently that average annual sea surface temperature for the sprawling ocean waters clocked in at 53.66 degrees Fahrenheit last year, more than 3.72 degrees above a 30-year average measured earlier this century. In 2021, the average annual sea surface temperature was even slightly higher, at 54.09 degrees.
The rapid rise in water temperatures has dire consequences, such as the loss of marine species, some of which are major sources of food and commercial fishing activities, and rising sea levels that can damage coastal communities.
“It’s part of a multidecadal trend that ... has profound implications for not just people who rely on the Gulf of Maine for their livelihoods and well-being but also for coastal communities,” said Dave Reidmiller, director of the Climate Center at the Gulf of Maine Research Institute.
Home to more than 3,000 aquatic species and birds, the gulf is “one of the most biologically productive marine ecosystems” in the North Atlantic, according to the Gulf of Maine Association. It covers a 36,000-square-mile area from the tip of Cape Cod to Cape Sable in Nova Scotia, and its historically cold waters are a key reason why the gulf is such a viable environment for marine life.
The temperature of the gulf has been rising rapidly for more than a century, at a rate more than three times that of the world’s oceans, according to the institute’s report released last week. It surpassed the average temperature of the global oceans in the 1990s.
Rising gulf temperatures are also, in large part, why New England itself is warming faster than the planetary average, scientists say.
Temperature increases have “drastic impacts on fisheries and the ecosystems,” said Svenja Ryan, a research associate at the Woods Hole Oceanographic Institution, or WHOI. “Our coastal community really strongly depends on fisheries, such as lobsters. ... They’re actually moving further northward into Canadian waters, where they’re facing a habitat that they’re more used to from the past.”
Its world-famous lobster fishery is the foundation of Maine’s coastal economy, yielding hundreds of millions of dollars in landings each year and supporting thousands of jobs. But shortages of food as a result of a warming gulf aren’t just limited to lobster, scientists say.
“If anyone eats anything from the ocean, you’ve got to care about marine heat waves,” said Brenda Ekwurzel, a climate scientist at the Union of Concerned Scientists. “More often, these heat waves are lasting longer, and we’re having mass mortality events, which is really, really concerning. If it happens to be at the base of the food chain and we are eating fish that are at the higher end of the food chain, it really can have a big impact.”
We’re “getting to the edge of habitability for certain species,” Ekwurzel said.
But Janet Duffy-Anderson, chief scientific officer of the Gulf of Maine Research Institute, emphasized that although lobsters are moving north, warmer waters are bringing more species farther north from the Mid-Atlantic, including sea bass, squid, and blue crabs. With a strong stewardship and adaptation in the coming years, she said, New England fisheries can redirect the industry and maintain a “robust blue economy.”
“Can we build a new fishery around these species that are coming from the Middle Atlantic? In the short term, yes,” Duffy-Anderson said. “There are opportunities to be successful here and capitalize on having new species in the region. In the long term, though, it’s very difficult to be able to say whether or not that’s going to be sustained.”
In August 2022, researchers at WHOI found that warming in the Gulf of Maine during the 20th century had reversed 900 years of cooling.
“One of the reasons that the Gulf of Maine is warming so rapidly is because of where it sits in the North Atlantic with regards to ocean circulation,” said Nina Whitney, an adjunct scientist at WHOI and research assistant professor at Western Washington University who was the lead author of the 2022 WHOI paper. “Anthropogenic — or man-made — warming is causing ocean circulation to change.”
The Gulf of Maine is fed by both cold water from the Arctic and warmer saline water from the Gulf Stream. As ice melts in Greenland and the Arctic Ocean, the pulses of freshwater can change ocean circulation patterns, according to the National Centers for Environmental Information, or NCEI, and weaken the cold current that flows into the Gulf of Maine.
“What we’ve observed is that in the recent decade, we’ve had a smaller influence of these colder, fresher waters from the Arctic because they’re being diverted into the open ocean, and a stronger influence from the Gulf Stream,” Ryan said, contributing to higher water temperatures in the Gulf of Maine.
Another factor, the NCEI has said, is “the overall warming of the global ocean as greenhouse gas concentrations rise.”
Scientists also stressed the warming water poses another threat in the Gulf of Maine. Because water expands as it heats, the sea level in Maine is estimated to rise an additional 1.1 to 1.8 feet by 2050, according to the Maine Climate Council.
The rate of sea level rise is “not reversible on human timescales,” according to Reidmiller.
“If, for example, we were capable of reducing all greenhouse gas emissions to zero globally tomorrow, atmospheric temperatures would stabilize within a decade or so,” Reidmiller said. “But because of the strong inertia of the ocean system, sea level rise would continue for centuries, if not millennia.”
Reidmiller said the 2022 temperature levels are an “undeniable” indicator of a long-term trend, warning the warming of the gulf will continue to accelerate and that adaptation to a changing environment will be necessary.
“The stark reality is that while last year was the second-hottest year on record, it’s likely to be one of the coolest ones going forward,” Reidmiller said.
Dharna Noor of the Globe staff contributed to this report.