Seals reveal changes in Antarctica’s most threatened glacier


An elephant seal rests on the beach of Robert Island, in the South Shetland Islands archipelago, Antarctica.

An elephant seal rests on the beach of Robert Island, in the South Shetland Islands archipelago, Antarctica.
Photo: Natacha Pisarenko (AP)

Meltwater from Antarctic glaciers is changing the composition of the region’s oceans more than previously known, a new study finds. The measurements that made these findings possible were collected by an unusual group of researchers: seals.

The study, published Friday in Communications: Earth and Environment, uses measurements of water temperature and salinity to show how meltwater from glaciers is changing the composition of the ocean near the Pine Island Glacier. one of the fastest retreating glaciers on the continent. The researchers found that warmer and cooler meltwater was distributed in patches throughout the ocean, including portions that rise near the surface. Those surface layers bring iron and other nutrients to the ocean surface, which encourages the growth of algae and other biomass and keeps the ocean relatively ice-free.

“In this part of the sea, the glaciers are melting so fast they are called ‘Doomsday Glaciers‘”Said Yixi Zheng, lead author of the study and a graduate researcher at the University of East Anglia. “We really care about what is happening in that region. We want to know how fast they are melting and the impact of these glaciers on the climate system ”.

While meltwater from glaciers is best measured in winter, when its hydrographic signature is clearer, this has always posed a problem for scientists. Not only is the Pine Island Glacier extremely remote, but the ocean near the glacier is covered in ice 10 months out of the year, making access to deeper parts of the ocean with human instruments nearly impossible to obtain.

Seals, however, can and do swim under sea ice. Zheng and his team used a data set collected by seals swimming near the Pine Island Glacier and equipped with sensors that collected temperature, salinity and water pressure. The seals were then monitored between July and September 2014.

“The seals are so amazing,” Zheng said. “They are very good at finding small holes in the sea ice. Sometimes I feel like we should give them a Ph.D. They are doing better than many scientists. “

As versatile as seals may be, they are not perfect researchers. You can’t control where a seal will swim, so you can’t ask them to patrol a specific area. That makes them somewhat erratic contributors, but the team was lucky with the ones they had.

“We have been very, very lucky in this region. Right in front of the glacier, we had this seal hanging around, enjoying a winter vacation, ”Zheng said. It’s not so surprising that a seal chooses to settle near a melting glacier: As Zheng’s study shows, meltwater on the ocean surface near glaciers encourages algae, which means more food for the seals. .

Researchers have also used stamps in other studies. Some of the most charismatic mammals in Antarctica also helped solve what caused a huge hole to form in the region’s sea ice. Scientists too seals monitored from space as an indicator of the health of the various Antarctic ecosystems. Those ecosystems support crucial fisheries that humans depend on, and what happens to the continent’s huge ice reserves has implications for coastal populations around the world. In a region that changing rapidly, any additional data that investigators can collect to be able to monitor what is happening is vital in planning what comes next.

Zheng, who tagged seals on a trip to Antarctica in 2019, said he sees many opportunities for seals to help scientists collect measurements and believes that seal tag data will become more popular in future studies. . Seal-equipped sensors, Zheng said, cost between about $ 4,1000 and nearly $ 7,000. That may sound expensive, but it is astronomically cheaper than sending a team of scientists with expensive equipment camping in Antarctica to collect similar data.

“We really love seal tag data and are trying to make the most of it,” Zheng said.

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