Researchers with the New England Aquarium were conducting a regular survey of the waters south of Martha’s Vineyard and Nantucket in Massachusetts last week when something caught their eye.
What they spotted, a whale without a dorsal fin, led the researchers to think that it might be a North Atlantic right whale, a critically endangered species that the aquarium has been closely monitoring. But the whale’s skin was blotchy, and if it were a right whale, something would have been wrong.
“I kind of had a weird feeling about it,” Orla O’Brien, an associate research scientist, said in an interview. “Something didn’t seem right.”
So when the whale resurfaced and Ms. O’Brien and her observation partner, Kate Laemmle, a research technician, were able to see its distinctly shaped head and mottled gray and white skin, they could not believe their eyes: Could it be a gray whale? In the Atlantic Ocean?
“It was really hard to mentally understand it,” Ms. O’Brien said.
But a gray whale it was, a sighting the aquarium described in a statement on Tuesday as “an incredibly rare event.”
Gray whales are regularly found in the North Pacific, but sightings in the Atlantic, from which the whales had vanished by the 18th century, are extremely rare. Experts say that it is not clear why they had disappeared, but that whaling may have been a factor.
There have been five sightings of gray whales in the Atlantic and Mediterranean over the past 15 years, according to the aquarium. The most recent was off the coast of Florida in December, and the New England Aquarium believes that whale is the same gray whale that researchers spotted off Nantucket last week.
Scientists say that climate change is largely to blame for the strange sightings. The Northwest Passage, which connects the Atlantic and Pacific Oceans between the Canadian mainland and the North Pole, has been ice-free during the summer months in recent years, in part because of rising global temperatures. Without ice, gray whales were able to swim through the passage, something that would not have been possible in the last century, the aquarium said.
The whale spotted by Ms. O’Brien and Ms. Laemmle did not appear to be in bad condition, and the two observed the whale feeding, “which is good,” Ms. O’Brien said.
“But you’re left with the ‘How did it get there?’ part,” she said. “Which is, on the whole, not a positive story as it’s only because of warming temperatures that these passages are being created to have transit through.”
Ms. O’Brien said she and Ms. Laemmle were not able to assess the whale’s age or sex, but planned to send photographs to researchers in the Pacific to help identify it. She also said that the only way to track the whale would be through reports of other sightings.
Joshua Stuart, a quantitative ecologist at Oregon State University who published a study on gray whales in October, said the gray whale sighting in the Atlantic was “super cool” but there were two important pieces of context.
First, whales are able to swim between the ocean basins because of melted ice in the Arctic, which he said “is an expected result of climate change.”
Second, Dr. Stuart said, the gray whale is coming out of what is known as an “unusual mortality event” over the past four years, most likely because of a loss of prey in the Arctic. According to the most recent estimates, there are believed to be about 14,000 gray whales, down from 27,000 in 2019, he said.
Dr. Stuart said the mass die-out appears to be tapering off. In mass mortality events, gray whales start to feed on things they don’t normally eat or show up in places they are not normally seen, like the Atlantic.
“There’s a potential that some of these unusual sightings in the Atlantic could be the result of that,” he said. The gray whales in the Pacific and Arctic “are just not getting what they need to survive so they’re searching for food elsewhere, so we see them in all kinds of weird places.”
But the sporadic sightings of gray whales outside their usual habitat could be a sign of things to come, he said.
“What is really cool is that we could be watching the recolonization of the Atlantic gray whale in real time,” Dr. Stuart said.
He said he did not expect a full recolonization of Atlantic gray whales to happen anytime soon, noting that the process could take decades, even centuries. But because of the rapid rate of warming waters, Dr. Stuart said, “we might be witnessing the very beginning of that.”
Still, Ms. O’Brien said it was too soon to tell if something like that would happen.
“The timeline is beyond what we would be able to observe,” she said. “For that many whales to come over and stay here would take a very long time.”