Giving the Thwaites Glacier in West Antarctica-one of the largest glaciers in the world-the nickname, the "Doomsday Glacier," doesn't instill much confidence in its ability to remain a body of dense ice. A study published Monday in the journal Nature Geoscience instills even less confidence, with data showing the glacier could speed up its rate of retreat at any moment, leading to a collapse that could increase the global sea level by more than two feet.
"Just a small kick to Thwaites could lead to a big response," Ali Graham, a Florida University marine scientist and lead author of the study, says in a news release.
A multi-national research team employed the bright orange Rán robotic vehicle loaded with imaging sensors to map an area of the seabed in front of the glacier that was about the size of Houston. It was the first time in history the glacier front was accessed.
"It was truly a once in a lifetime mission," Graham says in the release, noting that the team wants to sample the seabed sediments to more accurately date the ridge-like features created by glacier movement. "But the ice closed in on us pretty quickly and we had to leave before we could do that on this expedition."
Calling the data beautiful, if not concerning, Graham mapped a critical area of the seafloor in front of the glacier in high-resolution, learning that Thwaites, at some point in the last 200 years, over a duration of less than six months, retreated at a rate of more than 1.3 miles per year-twice the documented rate seen from satellite imagery between 2011 and 2019. "Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th century," Graham says.
"Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future-even from one year to the next-once the glacier retreats beyond a shallow ridge in its bed," Robert Larter, a marine geophysicist from the British Antarctic Survey and coauthor of the study, says in the release.
To understand Thwaites' past retreat, the team analyzed rib-like formations submerged about half a mile beneath the polar ocean. Figuring in the tidal cycle for the region, as predicted by computer models, they determined that one rib was formed every day. "It's as if you are looking at a tide gauge on the seafloor," Graham says. "It really blows my mind how beautiful the data are."
The effort comes as part of a five-year project to use the geological record of the sea floor in front of Thwaites to reconstruct the history of the glacier and investigate how it has responded to the atmosphere and ocean.
Computer modeling warns that Thwaites could lose ice more rapidly in the next few decades, leading to significant increases in sea levels. Finding the sustained pulses of rapid retreat in the glacier's history leads scientists to believe another occurrence of this movement could happen again.
"Similar rapid retreat pulses are likely to occur in the near future," the authors write, "when the grounding zone migrates back off stabilizing high points on the sea floor." That leads to "major uncertainty for future sea-level projections" and brings us all to hope those Thwaites fingernails hold strong.