Marine geophysicist Kelly Hogan of the British Antarctic Survey mapped the seafloor in front of the glaciers. For two months in the winter of 2019, Hogan was part of a joint US-UK expedition to the region, a trip that began at Punta Arenas, Chile. After a five-day crossing to Antarctica on the US research vessel Nathaniel B. Palmer, Hogan arrived at the Thwaites study site and found herself staring at a massive wall of ice. “We approached Thwaites at night,” Hogan recalls. “It was dark and foggy. I went to the bridge to talk to the captain, and as we were talking this 25-meter cliff emerged out of the gloom.”
The fiery orange submarine, which she named Ran after the Norse goddess of the sea, hadn’t yet resurfaced from its first mission in the watery depths around the face of West Antarctica’s Thwaites Glacier.“She’s a very temperamental lady,” Wåhlin said of the $3.6 million, unmanned submarine, while peering through her binoculars on an overcast March day.
Over the next two months, the scientists traversed the 80-mile wide embayment in front of the glacier in a back-and-forth pattern known as “mowing the lawn.” The researchers used a multibeam echosounder mounted under the ship to collect sonar images of the seafloor that were assembled into a 3D map. Together, they revealed massive seafloor channels moving warm water to the base of the glacier.
“They are important because Thwaites is vulnerable to changing quickly under climate change,” Hogan says. “One of the drivers is warm water getting underneath the floating parts and increasing the melting. The fact we have these big underwater channels going all the way up to the base of the glacier—because they are deeper and larger, you get more of that warm water and would increase the ability to melt.”