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Journey to Antarctica: How Scientists Are Using Seals to Measure the Warming Ocean

About 50 seals are collecting essential data on water temperatures deep beneath the ice

seals and antennas antarctica

A female Weddell seal tagged with a temperature probe that will relay data via satellite to a central database.

Linda Welzebach/Rice University Permit: FCO 29/2018

This is the fifth dispatch in a series from Jeff Goodell, who is in Antarctica investigating the effect of climate change on Thwaites glacier.

Aboard the Nathanial B Palmer, the research vessel and icebreaker I’ve hopped on for a two-month journey to Antarctica, there is much talk about how the fate of the civilized world – or at least major coastal cities – may be determined by the movement of warm circumpolar deepwater currents under Thwaites glacier in West Antarctica. How far and how fast that warm current is flowing under Thwaites, melting it from below, will broadly determine how quickly the glacier collapses, potentially setting off a cascading ice sheet failure in West Antarctica that could result in 10 feet of sea-level rise in the not-so-distant future. Ten feet of sea-level rise means goodbye Miami, Boston, Shanghai and virtually every other coastal city you want to name.

The trouble is, measuring warm circumpolar deepwater in Antarctica is extremely difficult – especially under the ice. High tech underwater moorings can help, but they only cover limited areas and don’t measure the top 1,000 feet of the ocean. Remote submersible devices, such as the Hugin we have aboard the Palmer, gather megabytes of precise ocean data, but they are expensive  and best suited to targeted research projects.

Mother Nature has better ways. As it turns out, seals are terrific research assistants in Antarctica. Weddell and elephant seals, in particular, regularly swim through exactly the waters scientists want to explore, and they do it all year long, even under thick ice. Why not give them a digital notebook and let them record what they see? And that’s pretty much what a seal tag does. Using what amounts to a temperature probe hooked up to a satellite phone, seal tags record where seals swim, how deep they dive and what the ocean’s temperature and salinity is wherever they travel. When a seal surfaces, the tag beams the results up to a satellite, which is then relayed to a central database, giving scientists real-time data that they use to calculate changes in ocean circulation, as well as to better understand the behavior of the seals themselves.

Right now, there are about 50 seals compiling data in the ocean around Antarctica, with many more working in oceans around the world. Researchers studying tagged seals have noticed no change in their behavior or reproduction rate after they are tagged.

Here on the Palmer, the man in charge of seal tagging is Lars Boehme, 44, an oceanographer and ecologist at University of St. Andrews in Scotland. Boehme, who grew up in a coastal town in Germany, is a witty, cheerful guy who looks like he always has something more important to do than comb his hair. He first sailed across the Atlantic alone when he was 18 (he’s done it twice) and considered a career as a sail-maker before giving it up for science. On the Palmer, Boehme has earned the nickname “the seal whisperer” for his obvious connection with seals and his respect for their intelligence and remarkable capabilities (at dinner this week, he wowed a group of us by explaining how a seal can track fish by using its whiskers to detect the minute disturbances the fish makes in the water as it swims).

A few days after the Palmer left port in Chile, Boehme gave a talk to the 30 or so scientists and support staff on the ship about how seal tagging works. “We are looking for elephant and Weddell seals who come up onto the beaches to molt,” Boehme said. Every summer, which runs from December through March in Antarctica, seals shed their entire coats in a few days. The idea is to find the seals just after they molt and glue the seal tag to their head (he uses ordinary epoxy, the same kind of stuff you can buy at Home Depot). If all works well, it will stay on their head, tracking their moves and sending back data, until they molt the next year, when the tag will harmlessly fall away. Boehme explained that he checks to see if a seal has molted by pulling its fur. “If you can pull it out, it means they’re still molting,” he said. “If it’s firm, they are done.” Boehme injects Zoletil, a drug commonly used by dog and cat veterinarians, to tranquilize the seals before he attaches the tag. He usually injects the drug with a dart, which he shoots into its back through a blowgun because it allows him to keep a safe distance away and not disturb the animal. If a seal happens to be injured (male elephant seals are often wounded in brutal mating battles over females), he will also inject it with an antibiotic to help it recover.

Sometimes, a seal wakes up from the tranquilizer and immediately tries to head toward the water. If it’s not completely recovered from the drug, it may become confused, and it can drown, just like a human. To prevent this, Boehme explained, he often places himself between the seal and the ocean while the seal is recovering, knowing it will shy away from him and avoid the water. “Recovery from the tranquilizer only takes 10 minutes or so, and then they can go back in the water and resume their normal lives,” Boehme explained. Over the last 10 years, he has tagged over 150 seals and never had one drown.

Boehme views seals as more than a tool to better understand climate change. He also wants to better understand the seals themselves. “I’m interested in what is going on in their heads,” he says, tapping on his skull. “The better we understand them, the more we can do to protect them and the environment they live in.”

When we arrived at the beach on Schaefer Island, a Weddell seal was laying on the rocks a few yards from the edge of the cold Antarctic waters. Schaefer Island is a tiny spit of land less than a mile from the coast of Antarctica, windblown, with icebergs like fortresses around us. Weddell seals are smaller than elephant seals, and don’t dive as deep, but they are still big, impressive animals. This one was a female. She was more than five feet long and Boehme estimated she weighed about 600 pounds. Her fur was light brown, her eyes closed. She wasn’t moving. I wondered if she was dead. “She’s just taking a nice long nap in the sunshine,” Boehme explained. Meanwhile, we humans all had on at least five layers of high-tech winter gear, insulated boots and several pairs of gloves. And we were still freezing. “When you come to Antarctica,” Boehme said, “you feel like an alien, while all the animals are well-adapted and comfortable.”

antenna seal antarctica

Oceanographer Lars Boehme (right) tags a seal so it can collect data on temperatures deep beneath the ice in Antarctica. Photo credit: Linda Welzebach/Rice University Permit: FCO 29/2018

A few yards away, a big male elephant seal eyed us. He was about three times the size of the female Weddell seal — Boehme estimated he weighed nearly a ton. When he walked over to check if it might be a candidate for tagging, the seal lifted his head and opened his pink mouth, revealing long fang-like teeth, and roared like a lion. Boehme seemed amused. “He’s cranky,” Boehme said. He determined that the seal had not molted yet, so it was unsuitable for tagging.

With that, he focused on the Weddell seal sunbathing on the rocks. He had already checked her fur – she had molted. But Boehme was concerned that the seal was too close to the water and could make a run for it under light sedation. So instead of using a blow dart to tranquilize her, which injects the drug into the muscle and is slow to take effect, they would use a head bag to quickly gain control of her and then use a syringe to inject the tranquilizer intravenously. It was a little more difficult, but in Boehme’s view, it was safer for the seal.

Boehme and Bastion Queste, an oceanographer at University of East Anglia who was assisting him, approached the seal with a heavy green canvas bag with straps on each side. It woke at their approach, its big dog-like eyes looking at them curiously. Boehme and Queste tried to slip the bag over her head, but she twisted away. Who are these strange upright creatures and what are they trying to do to me? Unlike in the Arctic, where seals are preyed upon by polar bears and flee any movement, seals in Antarctica have no natural predators. And so they have no fear. But they are also highly intelligent.

Boehme and Queste moved with the seal, but it danced away again, surprisingly graceful and fast. They wrestled and danced with the seal for a few minutes. Then, in one quick move, it was done. The seal was hooded. At first, it was hard not to make a disturbing visual association with a Klansman or executioner. But it was apparent that the seal was not hurt. In fact, she calmed down. Boehme gently lowered the seal’s head to the ground, and the rest of the team quickly came over. Gui Bortolotto, a veterinarian and marine mammal ecologist at University of St. Andrews who is working with Boehme, brought over a syringe. Boehme found a spot in the vein that runs along the seal’s back and injected the tranquilizer. You could see the seal go limp immediately. Boehme and his team withdrew to give the tranquilizer a few moments to take effect.

Working quickly, Boehme checked that the tag was functioning properly. Then he and Bortolotto and Queste knelt down beside the seal, measured its length (8 and a half feet) and rolled it on its side to measure its girth (about 63 inches). They folded back the hood to reveal the seal’s head, while keeping its eyes covered. The seal was waking, so Bortolotto gave her a small additional shot of Zoletil. As soon as she relaxed again, Bortolotto cleaned the seal’s head while Boehme spread epoxy on the base of the tag. Then he set it on the seal’s head, moving with a kind of gentleness that he might use if he were crowning a queen. He positioned the tag exactly where he wanted it and neatly spread the epoxy along the edges of the tag, wiping away any excess. He pressed the tag firmly into the seal’s head with two fingers while the epoxy set. Then, quietly, Boehme and the others stood up, removed the bag from over the seal’s eyes, and stepped back.

The seal’s breathing stuttered a bit, which Boehme assured me was normal. Then she slowly opened her eyes and looked around, as if waking from a dream. She didn’t know it, but she now had a plastic box with an antennae glued to her head. It looked ridiculous, almost comical. And a lot of people will say it’s depressing to see a beautiful wild animal tampered with like this, even if she were unaware of it and felt no pain. Some people might even be outraged by it. But to me, this partnership between seal and scientist was moving, even heroic. Within the next hour, she would slide into the cold Antarctic waters and be off on her journey, diving into the deep, surfacing, and sending data back to Boehme, doing her part to help scientists learn about the warming waters and the risk of ice-sheet collapse. Perhaps she would even help humans figure out a way to save themselves from their own worst impulses.



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