According to NOAA, more than 90% of the warming that has occurred on Earth over the past 50 years has happened in the ocean. As water temperatures rise, the animals that live in it adjust — and sharks are no exception.
Great white sharks, for instance, tend to avoid water warmer than 82 degrees. When surface temperatures climb beyond that threshold, they move — either deeper or further north.
“That tends to be a major break for them,” said Dr. Chris Lowe, professor of marine biology and director of the Shark Lab at California State University Long Beach. “It pushes them either deeper or further north.”
Every summer, sharks along the East and Gulf Coasts migrate up toward Cape Cod and Atlantic Canada as southern waters warm. What’s changing is the timing — and the geography.
A 1,400-pound puzzle off Florida
One of the clearest examples this season involves Breton, a massive great white shark tagged by OCEARCH in 2020. In mid-July, Breton was pinged off the coast of Florida — far south of where sharks like him typically spend this time of year. Water temperatures at his location registered at 87 degrees, well beyond what great whites prefer.
Researchers believe he may be following food sources, and note that sharks are capable of diving deep to escape surface heat for extended periods.
Adaptable, not alarming
Marine biologists are watching these shifts carefully — not with alarm, but with curiosity. Sharks appearing earlier, later, or in unexpected locations is data worth paying attention to.
“There are going to be range extensions where sharks aren’t normally seen, because the waters are warming in different areas,” said Joe Yaiullo, curator and co-founder of the Long Island Aquarium. “They’re very adaptable. They’ve been around hundreds of millions of years.”
Yaiullo also offered a reassuring perspective: the fact that apex predators like great whites are thriving is actually a sign of a healthy ocean ecosystem. Humans, he noted, are not what sharks are looking for.
“If the water is salty, there will be sharks. The fact that these apex predators are doing really well is a great sign — and something that shouldn’t really be feared.”
Simple precautions go a long way
For beachgoers, experts recommend a few common-sense measures: avoid swimming at dawn or dusk, steer clear of areas with large numbers of seals or fish schools, and pay attention to any posted warnings.
Sharks follow food. This summer, that food — and the warming water carrying it — is showing up in new places. The ocean is changing, and its oldest inhabitants are changing with it.