A new study by British and American scientists has found that tidal action beneath the Thwaites Glacier in Antarctica will “inexorably” accelerate melting this century. The researchers warn that this faster melting could destabilize the entire West Antarctic ice sheet, leading to its eventual collapse.
This massive glacier, roughly the size of Florida, is of particular interest to scientists due to its rapid rate of change and the significant impact its loss would have on sea levels, earning it the nickname “Doomsday Glacier.” It also acts as an anchor holding back the West Antarctic ice sheet.
Over 2 kilometers (1.2 miles) thick in some areas, Thwaites has been likened to a . Were it to collapse, sea levels would rise by 65 centimeters (26 inches). This is a significant amount, considering oceans are currently rising 4.6 millimeters a year. But if it led to the eventual loss of the entire ice sheet, sea levels would rise 3.3 meters.
While some computer models suggest that reductions in greenhouse gas emissions under the 2015 Paris Agreement may mitigate the glacier’s retreat, the outlook for the glacier remains “grim,” according to a report by the (ITGC), a project that includes researchers from the British Antarctic Survey, the U.S. National Science Foundation and the U.K.’s Natural Environment Research Council.
Thwaites has been retreating for over 80 years, but this process has accelerated in the past 30 years, according to Rob Larter, a marine geophysicist who contributed to the research. “Our findings indicate it is set to retreat further and faster.” The new research also indicates that other dynamics currently not incorporated into large-scale models could speed up its demise.
Using a torpedo-shaped robot, scientists have determined that the underside of Thwaites is insulated by a thin layer of cold water. However, in areas where the parts of the glacier lift off the seabed and the ice begins to float, tidal action is pumping warmer sea water, at high pressure, as far as 10 kilometers under the ice. This process disrupts that insulating layer and will likely significantly speed up the rate at which the grounding zone—the area where the glacier sits on the seabed—retreats.
A similar process has been observed on glaciers in Greenland.
The group also identified a worst-case scenario in which 100-meter-or-higher ice cliffs at the front of Thwaites are formed and then rapidly calve off icebergs, causing runaway glacial retreat that could raise sea levels by tens of centimeters in this century. However, the researchers said it’s too early to know if such scenarios are likely.
A key unanswered question is whether the loss of Thwaites Glacier is already irreversible. Heavy snowfalls, for example, regularly occur in the Antarctic and help replenish ice loss, Michelle Maclennan, a climate scientist with the University of Colorado at Boulder, explained during a news briefing. “The problem though is that we have this imbalance: There is more ice loss occurring than snowfall can compensate for,” she said.
Increased moisture in the planet’s atmosphere, caused by global warming evaporating ocean waters, could result in more Antarctic snow—at least for a while. At a certain point, though, that’s expected to switch over to rain and surface melting on the ice, creating a situation where the glacier is melting from above and below. How fast that happens depends in part on nations’ progress to slow climate change.