For one scientist, climate change in the Northeast announces itself in the abnormal appearances of warm-water fish – an abundance of mahi-mahi and unprecedented sightings in January of Gulf Stream flounder and juvenile black sea bass in shallow waters off the New England coast.
“Nobody had ever seen that before,” said Glen Gawarkiewicz, an oceanographer from the Woods Hole Oceanographic Institution in Massachusetts.
For another scientist, the phenomenon materializes in ocean temperatures, which have been rising for more than a generation, influencing coastal weather and pushing snowfall farther inland.
“Our winters now are not like our winters before,” said Lenny Giuliano, the state meteorologist in Rhode Island.
As water temperatures rise in the Atlantic Ocean and its connected gulfs and bays, the warmth may spread inland and generate temperature variations at the county level.
The water-to-land effect appears along the Great Lakes, which also are warming, said Mark Wysocki, New York state climatologist and a professor at Cornell University.
“There’s a very strong connection,” Wysocki said.
Though the Southwest saw the greatest rise in average air temperatures during the past five decades, data from the National Oceanic and Atmospheric Administration shows the Northeast warmed the most over both longer and shorter time spans.
Nowhere more so than Rhode Island: The state’s average temperature has increased 3.64 degrees compared with its 20th-century norm, according to NOAA records dating back to 1895.
Other states trail closely: New Jersey came in 3.49 degrees warmer; Connecticut, 3.22; Maine, 3.17; Massachusetts, 3.05; and New Hampshire, 2.93.
In the short term, Delaware and New Jersey were tied for the highest increase in average temperature among the lower 48 states, according to NOAA records for a five-year period ending in October. Closely behind were Rhode Island and Connecticut, followed by Arizona, California and Florida.
“Of course, we’re talking about a weather event … but it may have a longer-term climate signature, too,” Robinson said, adding it “definitely needs some study.”
Wysocki points to a naturally occurring shift in an air pattern called the North Atlantic Oscillation, which can play a role in air temperatures in the Northeast.
Many agree that water temperatures probably play a role.
“You see so much variability in temperature over land throughout the year,” said Ambarish Karmalkar, a climate researcher at the University of Massachusetts and the U.S. Department of the Interior’s Northeast Climate Adaptation Science Center. “Variability over the ocean is much smaller. … It takes much longer to warm the ocean, and takes much longer to cool it.”
That means the ocean works like a thermos, providing a lasting heat source even as winter temperatures descend around it. The effect always existed but is more pronounced.
Though researchers said the dynamic hasn’t fully been studied, NOAA data shows the effect down to the county level. Over the past five years, the four Connecticut counties hugging the coastline averaged 2.9 degrees warmer than normal, compared with 2.6 degrees for the four inland counties.
In Rhode Island, a half-degree difference separated Washington County on the coast and Providence County in the north. In Massachusetts, temperatures in Nantucket and Boston registered nearly a full degree higher than average compared with inland areas around the town of Amherst in Hampshire County.
Differences of 1 or more degrees separated Wicomico County on Maryland’s Delmarva Peninsula from the interior of the state, as well as Philadelphia from the Allegheny Mountains and downstate New York from the Adirondacks.
It’s even more amplified in Pennsylvania and New York where mountain ranges act as natural barriers, blocking warmer air coming from the coast.
“It’s hard for a marine climate to move far inland,” Wysocki said.
Counties along the New Hampshire and Maine coastlines lack any clear pattern. Maine as a whole hovered 1.9 degrees above average during that five-year time span – the middle of the pack among all states.
But five years is too small a window to observe definitive conclusions, said Sean Birkel, Maine’s state climatologist and a professor at the University of Maine.
“In general, the entire (Northeast) region has warmed over the past several years,” Birkel said.
One conclusion has emerged among the regions’ scientists: The Atlantic Ocean is warming, and dramatically so.
Gawarkiewicz studies the area of the Atlantic where the shallower waters of the continental shelf slide into the depths of the ocean. This area acts as a two-lane highway where cold waters from Canada and Greenland slip south closer to shore, while tropical waters pulled by the Gulf Stream pass north farther out to sea.
Over the past decade, an “extraordinary” change has hit the Gulf Stream, causing its path to become unstable, wobbling off the normal course and often bringing warmer waters nearer to shore, Gawarkiewicz said.
The stream emits more “warm core rings” – eddies of water up to 60 miles wide that spin toward land and can hold warm temperatures for months. Along the way, the rings can increase water temperatures in a given area as much as 12 degrees above average.
Gawarkiewicz pointed to a University of Massachusetts study showing such rings have spiked from about 18 annually before the new millennium to 33 annually now. Researchers tracked three of them in August and found they increased water temperature 5.5 degrees in the Georges Bank, an area of the continental shelf off Massachusetts that is larger than the state itself.
Other warming hot spots have hit locations such as Block Island, a 9-square-mile destination for vacationers and wildlife near the Rhode Island coast.
“They were catching Gulf Stream fish off Block Island in January,” Gawarkiewicz said.
Researchers suspect the rings play a role in the unusually high number of dead humpback whales along the Atlantic coast the past few years, Gawarkiewicz said.
Though scientists preliminarily concluded they died from ship strikes and fishing gear entanglement, they don’t know why it’s happening more frequently. Warming waters offer one possibility, as they could draw the whales closer to busier coastlines.
In general, climatologists and other researchers in the Northeast said that although there’s no doubt global climate change drives warmer air and water temperatures overall, there’s still much to learn about the interaction between the two. Among the most important inquiries is determining what’s here to stay and what will change with the wind.
“What is the future going to look like with (changing) patterns?” Wysocki said. “And for how long do they kind of lock themselves in?”