A ma in a bright orange suit holds his left arm in the air as an elephant seal opens its mouth to bellow.

These high-tech seals are charting future sea level rise

Deep-diving seals equipped with satellite-enabled temperature probes are exploring uncharted waters, gathering data to help predict how fast West Antarctica’s glaciers may melt.

On a rocky island just off the coast of West Antarctica, ecologist Lars Boehme is standing face-to-face with a 1,500-pound elephant seal, eyeing the animal’s bulbous nose and jowls to see if he’s finished shedding his fur.

When the seal opens his mouth wide to bellow, Boehme waves his hand in front of his face like he’s just smelled something foul.

“You can hear the amount of air going in and out,” Boehme said of the animal, which is the length of a small car and has a distinctively sour musk. “It’s like an air conditioner.”

Boehme is on a two-month scientific expedition to Thwaites Glacier, a Florida-sized glacier that sits at the center of West Antarctica. It’s melting fast and could eventually trigger roughly 11 feet of global sea level rise. Scientists on the voyage are working to decode if, and when, that might happen.

Boehme and three colleagues have come to one of the Schaefer Islands on a crisp day in mid-February to enlist an army of seals to help gather climate data.

Three men in orange suits sort through a box of equipment on a rocky island. Behind them, dozens are penguins walk around.
Lars Boehme, Bastien Queste, an oceanographer from the University of East Anglia, and Gui Bortolotto prepare to affix a sensor to a seal that will measure temperature, salinity and depth as it swims off the coast of West Antarctica.Carolyn Beeler/The World

As penguins squawk in the background and waddle around on small ridges, Boehme and his team look for seals to tag with sensors that will track the layer of warm water that’s thought to be melting Thwaites.

Scientists believe changing winds are forcing a layer of warmer, denser circumpolar deepwater up from the deep ocean and onto the shallower continental shelf in front of West Antarctica. But they don’t know exactly how. Clues from these seals, showing where that warm water is working its way toward the continent, how much of it there is, and how it changes seasonally, are key to understanding if, and how fast, West Antarctica’s glaciers might collapse.

“We record temperature, salinity and depth whenever a seal dives, and when the seal comes back to the surface, the data is transmitted in real time back to a ground station back home,” said Boehme, an ecologist and oceanographer at the University of St. Andrews in Scotland, who has been doing this work for 15 years.

Related: How can a seal track climate change? 

The data transmitted via satellite from the Amundsen Sea is available to scientists around the world almost instantly and can teach them more about seal behavior.  

It also paints a more detailed picture of how the circumpolar deepwater is flowing toward West Antarctica’s glaciers. The seals can track this water during the Antarctic winter, when humans and their scientific instruments can’t get there.

“In the winter, when it’s minus 40 degrees [Celsius], pitch dark, we get data from below the sea ice and we don’t have to be here, which is quite nice,” Boehme said.

Seals as allies in science

Back on the island, the massive male elephant seal hasn’t finished his annual molt yet. If Boehme put a sensor on him, it would fall off with his old fur in a matter of days. So Boehme, who’s wearing a neon-orange snowsuit that practically glows in the intense southern sun, finds another candidate.

Across the beach, there’s a sleek gray Weddell seal lounging on his stomach who has finished molting. To catch him, Boehme and a colleague use a large canvas bag with ropes for handles like a net. They stand on either side of the animal and try to slide it over the seal’s head as it looks up at them and twists and rolls around, appearing annoyed.

After a few minutes of scuttling around on the rocky beach in this strange dance, the scientists get the bag over the seal’s head to subdue him, then kneel beside him to inject him with anesthesia.

“They have no land predators here, this is why you can do that,” Boehme explained — the seals have no reason to flee when humans approach. “If you would be in the Arctic, this seal would be in the water when we came in with the ship.”

Boehme measures the seal and attaches a sensor about the size of a smartphone to the back of his head with epoxy. It has an antenna that makes it look like the seal has a unicorn horn.  

A man attaches a sensor onto a seal
Lars Boehme attaches a sensor to a Weddell seal on one of the Schaefer Islands off the coast of West Antarctica.Linda Welzenbach/Rice University

Boehme said this process doesn’t hurt the seals and the sensors don’t impact their reproduction or long-term survival.

“I like to think that they are our allies on this.”

Gui Bortolotto, University of St. Andrews

“I like to think that they are our allies on this,” said Gui Bortolotto, Boehme’s colleague at the University of St. Andrews and a marine ecologist who also trained as a veterinarian.

Weddell seals dive up to 2,000 feet deep, into the top layer of circumpolar deepwater. Elephant seals dive even deeper, into the trenches in the seafloor that funnel dense warm water toward West Antarctica’s ice shelves.

A seal turns it head. Atop its head is the transponder that will track climate data.
Transponders tracking temperature, salinity and depth as seals dive stay on the animals for about a year. They fall off when seals shed their fur during their annual molt.Linda Welzenbach/Rice University

This layer of warm water has long existed in the deep ocean. But now, it’s being pushed up onto the continental shelf and toward West Antarctica. Scientists believe changing winds are forcing the water toward the region’s ice shelves, and the changes may be linked to a warming atmosphere. But they need more data to know exactly what’s happening. And an army of data-gathering seals can help.   

“Every time I see them and think about these guys helping us, I think how lucky we are that [their biology] fits perfectly to fill the gaps that we need of data,” Bortolotto said, standing on the frigid island.

Two men kneel in front of a Weddell seal affixed with a transponder.
Gui Bortolotto and Lars Boehme keep an eye on a Weddell seal after tagging him with a sensor. Boehme will monitor him until he’s fully out of anesthesia and it’s safe for him to swim away.Carolyn Beeler/The World
About half an hour after the process started, the seal opens his eyes and starts to wake up. Boehme moves to sit on the ice-covered shore, between the seal and the water, to make sure the animal doesn’t slide off the beach and swim away before the anesthesia has fully worn off.

Seals as a gateway to Antarctica

Seals brought some of the first people to the Antarctic 200 years ago, but for a very different reason.

They were sealers armed with clubs, in search of Southern fur seals hunted for their silky pelts. Among them was Nathaniel B. Palmer, who was in his early 20s when his crew became the first Americans to spot the Antarctic Peninsula. (The icebreaker that carried Boehme and Bortolotto and roughly two dozen other scientists to Thwaites is named after Palmer.)

By the early 1800s, sealers like Palmer had wiped out entire colonies of Southern fur seals on islands farther north, so “every year that sealers went out, they were having to go further and further south in the south Atlantic to find the seal breeding grounds,” said Beth Moore, curator at the Nathaniel B. Palmer House in Stonington, Connecticut.  

On one of these missions in 1820, Palmer became one of the first people see Antarctica and one of a handful of people with competing claims on discovering it.  

He was on the South Shetland Islands scouting for seals in November of that year when he spotted part of the Antarctic Peninsula.  

“He basically says, ‘I’m looking at something, it’s not an iceberg, it’s a landmass and it’s not on my charts or maps so I’m going to write down where it’s located,’” Moore said. “‘But I’m going to do what I was sent to do, which is look for seals.’”

After he noted it down in his logbook, creating what Moore said is the oldest extant record of a sighting of the continent, he went right back to scouting for seals.

Southern fur seals were hunted to near extinction on islands around Antarctica within decades, or even years, of their discovery by sealers. At their primary breeding ground on South Georgia Island, they were considered commercially extinct by the early 1900s. It took decades for the population to rebound, but they now number in the millions there.

Seals fill ‘gaps in time and space’

Today, Antarctica’s seals are protected under an international treaty. Boehme has to get permits and go through ethical reviews to tag Weddell and elephant seals.

“I try to treat them like humans,” Boehme said from back on the icebreaker. “They have their own lives, they have families, so it is a big ethical question,”

Scientists have been using these kinds of sensors on marine mammals for about 20 years, and Boehme estimates there are 60-80 animals in the Southern Ocean currently wearing them.

A bar chart shows lines that go from deep blue to red showing temperature changes in water levels as the seals go deeper in the ocean.
The chart above shows the temperature readings collected by a single seal. The data from each dive is color-coded to show the temperature at a certain depth.Courtesy of Lars Boehme/University of St. Andrews

On the two-month expedition aboard the Palmer, Boehme attached sensors to 11 Weddell seals and one elephant seal during six days in the field, including one day out on thick pieces of floating sea ice. He could track their movements and the data they were sending back in near-real-time from the ship on the trip home, when it reached far enough north to regain internet access.

So far, those seals have collected more than 2,500 temperature and salinity profiles during roughly 40,000 dives, including dives that have tracked circumpolar deepwater.

A seal rests on a rocky beach. It has a transponder on its head.
Seals tagged in the Amundsen Sea in previous years have taught scientists more about their behavior and about the pathways warm water is taking toward West Antarctica’s glaciers.Carolyn Beeler/The World

The seals are telling scientists more about how they behave in a changing underwater environment and gathered data in an ice-choked bay the Palmer couldn’t break into while it was in the Amundsen Sea.   

“[The seals] are filling in the gaps in time and space,” Boehme said.

The seals will swim under sea ice through the Antarctic winter, collecting data until their sensors fall off during their next molt.  

Boehme can’t say much more what the seals have found so far, in keeping with the academic practice of not discussing results before they’re published in a peer-reviewed journal.

Seals tagged nearby in 2014 recorded new pathways where circumpolar deepwater was making its way onto the continental shelf. They also revealed the layer of warm water is thicker during the Antarctic winter than in the summer in some places.

Three men walk along the rocky beach, with sea ice and a big blue sky behind them.
Lars Boehme, Bastien Queste and Gui Bortolotto on one of the Schaefer Islands off the coast of West Antarctica.Carolyn Beeler/The World
Boehme hopes the more precise sea level rise predictions that will come out of this data and complementary work during a five-year research collaboration on Thwaites Glacier will prepare us better for our changing future. And help us understand how it might impact the seals.  

“Understanding the melting, the potential sea level rise, really helps us to better protect ourselves and all ecosystems,” Boehme said.

Climate change data, he said, “is an offer from the scientists to say, let’s do something and make it, maybe not even a better world anymore, but a world that we can cope with.”

This is the fourth in a series of deep dives into the science and people of the Nathaniel B. Palmer’s 2019 voyage to Thwaites Glacier in West Antarctica. Listen Mondays on The World and check back online throughout June to learn what scientists found as they studied the sea that’s melting this Florida-sized piece of ice. Follow us on Instagram for videos, quizzes and more photos from Thwaites.

Invest in global news with heart!

The World is a nonprofit newsroom powered by listener support. When you make a recurring gift, you’re making an investment that allows The World to cover the most important international stories with nuance and care. Our listeners are at the heart of what makes The World such an invaluable source for global news. Will you create a recurring donation today to power The World all year long?