The researchers, led by Stef Lhermitte, satellite expert at Delft University of Technology in the Netherlands, used satellite data to document the growth of the damaged areas from 1997 to 2019. The images showed highly crevassed areas and open fractures in the glaciers.
While rapid ice loss and melt of these Antarctic glaciers have been well documented, the new study suggests there could be future disintegration of the ice shelves to come.
“We knew they were sleeping giants and these were the ones losing a lot of miles (of ice), but how far and how much still remains a large uncertainty,” Lhermitte said. “These ice shelves are in the early phase of disintegration, they’re starting to tear apart.”
Thwaites Glacier is one of the largest and most unstable ice streams in Antarctica. It’s a giant mass of more than 192,000 square kilometers (74,000 square miles) — an area similar in size to the US state of Florida, or Great Britain.
The two glaciers effectively act as arteries connecting the West Antarctic ice sheet to the ocean. At their base are permanent floating ice shelves that act as a buttress to the fast-flowing ice behind it. The region holds enough ice to raise global sea levels by 1.2 meters (4 feet) according to NASA.
So what’s happening to the glaciers now?
Human-induced warming of our oceans and atmosphere because of the increasing release of heat-trapping greenhouse gases is weakening the planet’s ice shelves.
This ocean warming has increased the melting and calving (the breaking off of ice chunks) of Pine Island and Thwaites glaciers, studies show, while declining of snowfall means the glaciers can’t replenish themselves.
The damage researchers found pointed to a weakening of the glaciers’ shear margins — areas at the edges of the floating ice shelf where the fast moving ice meets the slower moving ice or rock underneath.
“Typically the ice shelf acts like slow traffic. It’s floating on the ocean but it buttresses the ice traffic behind it,” Lhermitte said. “So if you weaken this slow car, then the ice discharges more rapidly.”
That’s exactly what the researchers observed — and they believe these severely weakening parts of the glacier will accelerate mass ice loss. The study makes the case that this process should be included in models that project sea level rise, which it’s not currently a part of.
Researchers found that while the tearing of Pine Island Glacier’s shear margins has been documented since 1999, their satellite imagery shows that damage sped up dramatically in 2016.
Similarly, the damage to Thwaites Glacier began moving further upstream in 2016 and fractures rapidly started opening up near the glacier’s grounding line, which is where the ice meets the rock bed.
Researchers warn the process is creating a feedback loop — where the weakening ice shelf is speeding up the damage to the glacier’s vulnerable shear margins, which in turn leads to more damage and disintegration of the ice shelf.