Hefty elephant seals regularly dive more than 2,500 feet underwater, holding their breath for 30 minutes while swimming in the dark, frigid ocean depths.
This remarkable ability makes these mammals well-suited to collect critical data about deep, warming ocean waters that scientists believe could accelerate the thaw of the vulnerable West Antarctic glaciers. If melted completely, these glaciers, which once included the Manhattan-sized iceberg that broke off the Pine Island Glacier last year, would raise sea levels by some 10 feet, according to the seal-study's researchers.
NASA recently confirmed that ice losses in the West Antarctic are ramping up, "probably in response to global warming."
To better understand how the ice may thaw, scientists attached sensors to the foreheads of 14 southern elephant and Weddell seals, who hunt for fish in these deep waters, in 2014. The seals made over 11,000 deep dives before their annual molting, or skin shedding, naturally detached the devices — but not before providing scientists with an unprecedented amount of information.
"It's a world away from what we had before," Helen Mallett, a researcher at the University of East Anglia who led the study, said in an interview. The study was published in the journal Geophysical Research Letters last week.
Wild research seals near West Antarctica.
Image: Lars Boehme (SMRU)
Of these 11,000 dives, 6,700 provided good, scientifically useful "profiles" of the water's temperature at different depths. Until the seals, it took 20 years of scientists using long cables to gather just 1,000 profiles, said Mallet.
This is an immensely difficult part of the world to study. It's remote. It's deep. And for much of the year, surface ice and perilous icebergs makes getting there impossible.
"In winter it's inaccessible to humans," said Mallett. "It's too harsh."
This wasn't the first time researchers had employed seals to visit ocean depths, but it was a first for this vulnerable region. It could only be done because scientists spotted seals living in the area.
The West Antarctic ice sheets are particularly vulnerable to melting because they extend far over the ocean, so there's no land to protect their icy undersides from influxes of warmer water.
The water, coming from northern oceans, certainly isn't "warm," in the sense that bathwater is warm. In fact, Mallett characterizes it as "slightly less freezing water" compared to water closer to the frigid the Antarctic surface.
Still, this slightly warmer water is enough to thaw the undersides of the ice sheets, eating away at them. These glaciers matter because they act as plugs, holding the ice on land back. If the glaciers go, so could the land ice, exposing more vulnerable ice in a vicious melting cycle.
"There's nothing to stop it from getting faster," said Mallet.
A NASA map, derived from satellite imagery, showing the velocity of Antarctic ice moving toward the ocean.
It's still unknown just how rapidly warmer ocean waters will erode the glaciers. But Mallett hopes the seal monitoring can change that.
"In terms of pinning that down for the near future, it's so difficult to do," she said. "We just don’t know enough of what's going on there. We don’t have enough to work with yet."
But it seems researchers will have the opportunity to learn more, using both seals and even submarines.
Mallet said another study coauthor was given enough funding to use these wild seals for another three years. Meanwhile, the British research submarine "Boaty McBoatface" is also headed to Antarctica, as part of the Thwaites Glacier collaboration to investigate how warmer waters are altering these vulnerable glaciers.