‘This is in the next five to 10 years.’ Cape waters are heating up. Here’s why it matters.
Cape Cod Times
May 18, 2023
Ocean temperatures are rising — that’s no surprise.
It’s also no secret that the Gulf of Maine is among the fastest warming water bodies on the planet. But that highly publicized statement, generally applied to the northern reaches of the gulf, is only the start of a longer sentence. Glen Gawarkiewicz, a senior scientist in physical oceanography at the Woods Hole Oceanographic Institution, provided the rest of it recently, saying “and southern New England is not far behind.”
He is among many scientists watching with concern, especially in light of data showing marked increases in global sea surface temperatures this spring. Above average temperatures were not only observed in the northern part of the Gulf of Maine, but also in its southern reaches: Massachusetts and Cape Cod bays.
According to the National Oceanic and Atmospheric Administration‘s National Centers for Environmental Information, for example, on April 28 surface temperature north of Provincetown reached 47.1 degrees Fahrenheit, which was 4.7 degrees above April averages, and .1 degree above May averages. The April long-term average is 42.4 degrees and the May long-term average is 47 degrees.
Similar above-average temperatures were observed southeast of Nantucket, and at Woods Hole. Those temperatures spell out long-term challenges for the region, which is already seeing some of the effects of climate change.
“The problem is we’re going to get a triple whammy here, between ocean warming, sea level rise and storms,” said Gawarkiewicz. “I just don’t think the magnitude of the problem is really being comprehended.”
Svenja Ryan, an associate research scientist in physical oceanography at the Woods Hole institution, is also worried.
“We’re reaching unprecedented levels of ocean temperature in a large percentage of the global ocean,” she said.
And it’s especially evident here.
“Living here in New England I think a lot of people can feel the ocean is warming,” she said. “And we see more extreme events: more flooding events, more storms, more intense events.”
What’s causing sea temperatures to rise?
There are a number of factors that contribute to the rate of rising ocean temperatures in the region, the scientists said. Among these are global warming resulting from human-released greenhouse gases, in tandem with natural cycles like the El Nino and La Nina patterns that cause alternating periods of warmer temperatures and lower temperatures, and changes in ocean and atmospheric currents.
“An increasingly important factor is the Gulf Stream,” said Gawarkiewicz.
The Gulf Stream is “a strong ocean current that brings warm water from the Gulf of Mexico into the Atlantic Ocean,” extending up the East Coast, caused by a system of circular currents and winds called the North Atlantic Subtropical Gyre, according to NOAA.
In recent years, the Gulf Stream has shifted northward, influenced by pulses of colder and denser water from melting Arctic ice sheets.
“It is sending warm water north in the form of eddies called warm core rings,” Gawarkiewicz said, explaining “there was nearly a doubling of the number of warm core rings formed annually by the Gulf Stream in the year 2000 and that has brought a lot of warm water in proximity to the Gulf of Maine and contributed to the increasing appearance of warm water species.”
There is no single, simple answer for the warming
Ryan said there is no single, simple answer for the warming. “One of the challenges is to try to figure out how much is human made and how much is natural variability,” she said.
That said, she noted, “there’s no doubt there’s an overall warming trend,” especially in the upper 2,000 meters of the ocean. And there is no small amount of influence from greenhouse gas emissions. While human activity may not be entirely to blame, it has accelerated natural warming, Ryan said.
The trouble is, the extent of long-term human influence on global ocean warming trends can be “masked” by El Nino and La Nina events.
Added atmospheric warmth, and higher land and ocean temperatures could come this summer.
This spring, Ryan said, “we are in a neutral state” between La Nina and El Nino. While it could go back to a La Nina state, she said “there’s some indication of an El Nino developing.” This would bring in added atmospheric warmth and result in higher land and ocean temperatures this summer. It is of no little concern that the trend toward warming sea temperatures occurred even during the recently ended La Nina, which brings cooler conditions.
“We see very high anomalies in the mid latitudes” in both the Atlantic and Pacific oceans, Ryan said.
From about 2010, research reveals an apparent shift in ocean circulations, allowing “more warm water from the Gulf Stream to enter the shelf,” she said. “In the Gulf of Maine in particular there’s the Northeast Channel. We see the strongest warming rates around this channel where more Gulf Stream water can enter the Gulf of Maine.”
The extent to which natural processes are contributing to warming is more difficult to observe because they happen on longer, geologic time scales and scientific observations are all relatively recent.
“There’s other factors that come into the play, like a changing of the winds due to the North Atlantic Oscillation (recurring pressure patterns in the atmosphere) that changes the storm tracks and the currents,” she said.
There are also shifts in the polar jet stream, a west-to-east current of air that circles the northern hemisphere.
“For the Gulf of Maine, geographic location plays a key role. It is close to the axis of the jet stream in the atmosphere. Warming of the atmosphere in the Arctic has affected the jet stream, making it wavier,” Gawarkiewicz said. “It has also been descending for winter later in the season in some years (2012, 2016) which reduces the heat loss from the ocean in winter.”
During what he calls “the big warming” of 2012, “the jet stream brought the cold air down pretty late.”
“The normal heat loss from ocean to atmosphere was reduced by as much as 50%,” he said.
That left ocean temperatures already elevated when natural seasonal warming started.
“That caused enormous ecosystem disruption. It affected the lobsters in the Gulf of Maine. It affected when they molted. The puffin chicks were starving because their normal food was not there. It was just an enormous ecological impact in 2012,” he said.
By comparison, both 2021 and 2022 were warmer than 2012 in the Gulf of Maine, he said.
Why is the Gulf of Maine region heating up faster than most other water bodies?
So, what about the Gulf of Maine makes it one of the fastest warming water bodies on the planet? Ryan explained it is “special” because there is an interplay of two very different water masses.
“We have the Gulf Stream that ushers in a huge amount of heat, and then on the other side we have this cold Arctic water from the Labrador Sea that flows southward along the shelf. That’s just unique in the global ocean where you have these very strong contrasting water masses,” she said.
At the same time the Gulf Stream has shifted northward, the scientists said, the current from the Labrador Sea has weakened. All of this combines to allow more warm water to flow into the region.
Changing sea temperatures bring ecosystem changes, too
Changes in sea temperatures also mean changes in the behavior of marine life and the marine ecosystem, driving some marine life to deeper, colder waters farther off shore or farther north, and inviting in warmer waters species.
Some traditional New England fisheries, such as lobster and cod, have seen shifts not only in habitat, but also in population in recent years. For example, lobsters have a “pretty sharp cutoff” when it comes to tolerance for warming water, Gawarkiewicz said, and as a result “they’ve been moving further off shore.”
In January 2017, he said, he received numerous photographs from fishermen of unusual bycatch they were bringing in off of Block Island.
“They were catching warm water fish. It turned out to be one of these warm core rings,” he said.
Ryan agreed. “The water is noticeably warmer, and we see it in the data. Even the kind of fishing they would do 20-30 years ago, now we catch completely different fish. You see more tropical species,” she said.
How the fishing community is helping scientists understand changes
Gawarkiewicz appreciates how the fishing community has “really gotten behind doing cooperative research with scientists.”
He said he can “figure things out” about the changing warm and cold water circulation patterns in the ocean just from fishing community reports — a scientific goldmine, he said — about the species they are bringing up and where they are catching it.
The number of reports of the presence of warmer water fish he’s received even just since 2021 illustrate “just how extreme things are getting.”
“They’re just these warning alarms: we have to take this seriously,” he said.
What happens next?
More scientific study, particularly sub-surface temperature and salinity observations, are needed to get an even more detailed picture of what’s going on, scientists said.
“This is just a very large-scale problem,” Gawarkiewicz said. “Civilization is going to have to deal with these massive problems in the near future. This is not like our grandchildren’s problem. This is in the next five to 10 years.”
Addressing warming “is going to take political will.”
“There really needs to be concerted action by the government, as well as international cooperation, which is in short supply,” he said.
Even if humans stopped pumping greenhouse gases into the atmosphere now, “we would still feel it for decades,” Ryan said.
But, Gawarkiewicz said, “you always have to have hope. There’s a lot of ingenuity in the scientists and engineers around the world. The problem is that this problem was identified in the early 1980s. We just never addressed the emissions issues.”
Signs of encouragement do exist.
There are encouraging signs: an increasing emphasis on developing green energy, such as offshore wind and solar farming. Efforts are underway on the federal and state levels to curb greenhouse gas emissions, such as Massachusetts Clean Energy and Climate Plan that calls for cutting emissions by at least 50% below 1990 baseline levels by 2030, and to achieve net zero emissions by 2050.
Gawarkiewicz admitted it’s not an easy burden as a scientist to have an understanding of just how significant the global warming trends and changes are.
“I try to focus on the tiny things I can do, and not get down about things I cannot change,” he said. “We really have to revere our planet if we’re going to make headway on this. It’s really going to take a lot of effort.”
The Cape Cod Times is placing a special emphasis on reporting about heat effects this spring and summer as part of its ongoing Perilous Course project examining the human-centered damage and risks driven by the climate crisis.
Heather McCarron writes about climate change, environment, energy, science and the natural world. Reach her at firstname.lastname@example.org, or follow her on Twitter @HMcCarron_CCT