Jeremy Siegel: This is GBH’s Morning Edition. Heat has been top of mind around Boston this week. Today we are finally making our way out of a heat wave after several days of 90-plus temperatures. That is something you can certainly feel when you step outside, but the outdoor air is not the only place where heat matters. According to NOAA, sea surface temperatures have been increasing since the late 1800s, and 2023 was the warmest year on record. For our weekly science deep dive, we are taking a look at the science behind warming ocean waters and to talk more about it. We are joined by two experts. First off, our weekly guest meteorologist Dave Epstein. Good morning Dave.

Dave Epstein: Good morning.

Siegel: And we are also joined by Doctor Megan Winton, senior scientist at the Atlantic White Shark Conservancy. Good morning to you.

Dr. Megan Winton: Good morning. Thanks so much for having me.

Siegel: Thanks for joining us. So, Dave, I’ll start with you. What do we know so far about warming ocean waters?

Epstein: Yeah. Well, one of the things that we know is that the waters off the coast of Massachusetts and Maine, and into the Gulf of Maine, are some of the fastest-warming waters on the planet. In some cases, they’re warming up to three times as fast as the rest of the oceans, an average of about 0.9 degrees Fahrenheit per decade since the 1980s. So we are definitely seeing a change in our ocean temperatures right off our coastline.

Siegel: Megan, you study animals in the water, you study sharks. What does warming ocean water mean for the animals that live in the water?

Winton: Like Dave said, the Northwest Atlantic Ocean is one of the most rapidly warming regions of the oceans as climate change impacts are starting to take place. And what we’re seeing with the distribution of a lot of fish species is that they’re moving further north and into deeper waters as well. So there’s no question that the distribution of sharks — so I’m really focused on studying white sharks here at the Atlantic White Shark Conservancy. But the distribution of these species and some of their prey species are likely to shift north as climate change continues.

Siegel: I want to dig a little bit more into that. But first, Dave, what is the connection between the outdoor heat, what we feel every day when we go outside, and the surface water temperatures?

Epstein: So the warmer waters lead to warmer air, because you have more evaporation out of the warmer waters, and more moisture in the air makes it harder for the air to cool off. So if you have a little more moisture in the air, it doesn’t get as cool. So our nights are warming almost doubly as fast as the days. And that’s one of the reasons why we don’t see the cooler nights that people sort of experience back in the 50s, 60s, 70s, and even 80s when, yes, you had hot days, plenty of them, but the nights tended to cool off. That’s not happening as much. And certainly this week we’ve noticed that.

Siegel: So, Doctor Winton, we are seeing more of these high temperatures. We’ve also recently seen reports of more shark encounters across the East Coast. What role does climate change play, if any, in the changing patterns of shark sightings and also shark attacks?

Winton: That’s a really great question. So water temperature is a constraining, limiting factor for a lot of shark species. Most shark species are cold blooded right? So their body temperature and their physiology is determined by the temperature of the water they’re in. So it provides a really practical constraint on where they can go and where they can be. One thing that’s really complicated in terms of determining what the impact of climate change is on shark populations and their distribution right now is a lot of shark populations, including the population of white sharks, is making a comeback after populations declined really dramatically in the 1970s and 80s as fishing pressure really ramped up. So right now, what we’re seeing with a lot of shark species, including the white shark, is that their populations have been protected and managed in a more effective way over the past several decades. So we’re seeing populations making a comeback. And in the case of white sharks off of Cape Cod, what we’re seeing right now is really the population reclaiming its historical range. But the population was so low for so long that they weren’t frequent visitors to our waters. But what’s going to happen in the future is going to be very telling. So we already are seeing warmer water temperatures off the coast of Cape Cod every year. Since we started monitoring the population of white sharks really intensely in 2014, there’s no question that every year we’re getting reports of more warm water species in the waters off the Cape and Islands. So things are changing here really quickly, and it is very likely in the future that white sharks could be more year-round residents of our waters in Massachusetts, because right now they really only come here in the summer. And in fall. But we are also likely to see populations of their prey, which here seals are really important prey species for white sharks. So we’re likely to see some of those species shift further north. And the white sharks could ship with them as well. And so, you know, it’s complicated. We’ve got two very different kind of processes going on right now. But that’s why continued monitoring and research, looking at the distributions and movements of these species, are so important right now as our oceans are changing so rapidly.

Siegel: So a lot remains to be seen. But we can, in essence, expect to see more of these animals changing where they are because of the temperature in the water.

Winton: Yeah. So the distribution of different shark species could change as water temperatures warm. They could also occur longer in Massachusetts waters than they do right now.

Siegel: That was Doctor Megan Winton, senior scientist at the Atlantic White Shark Conservancy. And our meteorologist Dave Epstein, with our weekly deep dive into the science behind the weather. Thank you so much to both of you.

Winton: Thank you.

Winton: Thanks so much.

Siegel: For more on sharks and the work of the Atlantic White Shark Conservancy, head to our website GBHnews.org. There you can also find our Ask Dave series, where GBH meteorologist and gardening expert Dave Epstein answers all of your questions. And if you have a climate or garden related question for Dave, you can always text them to us at this number: (617) 300-2008. You can also send an email to thewakeup@wgbh.org. This is GBH 89.7.

Waters in the Gulf of Maine, the Atlantic patch off New England’s coasts, are warming faster than the rest of earth’s oceans — and that affects ocean life that calls the gulf home.

One species researchers are looking at is great white sharks. If current trends continue, sharks that now only visit the Cape’s waters during warmer months could become year-round residents.

Right now, it’s hard to tell how much of their population resurgence off Cape Cod is due to warming waters and how much can be attributed to other factors, said Megan Winton, a research scientist at the Atlantic White Shark Conservancy in Chatham.

“The Northwest Atlantic Ocean is one of the most rapidly warming regions of the oceans as climate change impacts are starting to take place,” Winton said. “And what we’re seeing with the distribution of a lot of fish species is that they’re moving further north and into deeper waters as well.”

According to NOAA, sea surface temperatures have been increasing since the late 1800s, and 2023 was the warmest year on record.

“In some cases, they’re warming up to three times as fast as the rest of the oceans, an average of about 0.9 degrees Fahrenheit per decade since the 1980s,” GBH meteorologist Dave Epstein said.

Sharks are typically cold-blooded, which limits their habitat ranges, Winton said. Great white sharks prefer waters between 50 and 80 degrees, according to NOAA.

“Things are changing here really quickly, and it is very likely in the future that white sharks could be more year-round residents of our waters in Massachusetts, because right now they really only come here in the summer and in fall,” Winton said. “Seals are really important prey species for white sharks. So we’re likely to see some of those species shift further north. And the white sharks could ship with them as well.”

Shark populations off Cape Cod have indeed risen in the last decade, since the Atlantic White Shark Conservancy began intensely monitoring them, Winton said.

But warming waters don’t tell the full story, she said.

“A lot of shark populations, including the population of white sharks, are making a comeback after populations declined really dramatically in the 1970s and 80s as fishing pressure really ramped up,” Winton said.

After human activity caused a decline in shark numbers, more effective protections for shark populations have helped those populations grow again.

“In the case of white sharks off of Cape Cod, what we’re seeing right now is really the population reclaiming its historical range,” Winton said. “The population was so low for so long that they weren’t frequent visitors to our waters. But what’s going to happen in the future is going to be very telling.”

Warmer waters can also impact humans, and lead to warmer air for us on land, Epstein said.

“You have more evaporation out of the warmer waters, and more moisture in the air makes it harder for the air to cool off,” Epstein said. “Our nights are warming almost doubly as fast as the days. And that’s one of the reasons why we don’t see the cooler nights that people sort of experience back in the 50s, 60s, 70s, and even 80s when, yes, you had hot days, plenty of them, but the nights tended to cool off. That’s not happening as much.”