NASA discovers an enormous cavity in Thwaites Glacier signaling rapid decay over just three years.

I keep vigil.

More devastating news out of West Antarctica. The Thwaites glacier base is attached to the marine bedrock, or it use to be anyways. New NASA satellite imagery shows rapid deterioration of Thwaites from a gigantic ocean carved cavity in the most vulnerable area of Antarctica to climate change. Thwaites is known to scientists that study glacial ice as the "most dangerous glacier in the world".

From NASA:

A large cavity- two-thirds the area of Manhattan and almost 1,000 feet (300 meters) tall - growing at the bottom of Thwaites Glacier in West Antarctica is one of the several disturbing discoveries reported in a new NASA-led study of the disintegrating glacier. The findings highlight the need for detailed observations of Antarctic glaciers' undersides in calculating how fast global sea levels will rise in response to climate change.

Researchers expected to find some gaps between ice and bedrock at Thwaites' bottom where ocean water could flow in and melt the glacier from below. The size and explosive growth rate of the newfound hole, however, surprised them. It's big enough to have contained 14 billion tons of ice, and most of that ice melted over the last three years.

"We have suspected for years that Thwaites was not tightly attached to the bedrock beneath it," said Eric Rignot of the University of California, Irvine, and NASA's Jet Propulsion Laboratory in Pasadena, California. Rignot is a co-author of the new study, which was published today in Science Advances. "Thanks to a new generation of satellites, we can finally see the detail," he said.

snip

About the size of Florida, Thwaites Glacier is currently responsible for approximately 4 percent of global sea level rise. It holds enough ice to raise the world ocean a little over 2 feet (65 centimeters) and backstops neighboring glaciers that would raise sea levels an additional 8 feet (2.4 meters) if all the ice were lost.

snip

Another changing feature is a glacier's grounding line - the place near the edge of the continent where it lifts off its bed and starts to float on seawater. Many Antarctic glaciers extend for miles beyond their grounding lines, floating out over the open ocean.

Just as a grounded boat can float again when the weight of its cargo is removed, a glacier that loses ice weight can float over land where it used to stick. When this happens, the grounding line retreats inland. That exposes more of a glacier's underside to seawater, increasing the likelihood its melt rate will accelerate.

NASA JPL provided a terrifying image of the crater in Thwaites. I am unable to upload it to the Image Library as the file is too large, take a look at the JPL link. Gobsmacking!

The huge cavity is under the main trunk of the glacier on its western side - the side farther from the West Antarctic Peninsula. In this region, as the tide rises and falls, the grounding line retreats and advances across a zone of about 2 to 3 miles (3to 5 kilometers). The glacier has been coming unstuck from a ridge in the bedrock at a steady rate of about 0.4 to 0.5 miles (0.6 to 0.8 kilometers) a year since 1992. Despite this stable rate of grounding-line retreat, the melt rate on this side of the glacier is extremely high.

"On the eastern side of the glacier, the grounding-line retreat proceeds through small channels, maybe a kilometer wide, like fingers reaching beneath the glacier to melt it from below," Milillo said. In that region, the rate of grounding-line retreat doubled from about 0.4 miles (0.6 kilometers) a year from 1992 to 2011to 0.8 miles (1.2 kilometers) a year from 2011 to 2017. Even with this accelerating retreat, however, melt rates on this side of the glacier are lower than on the western side.

The interaction between the ice and the ocean has more complexity than scientists previously thought according to NASA. We are heading rapidly into unchartered territory, I’m scared to death.

Meanwhile, at nearby Pine Island Glacier, the ice platform is crumbling.

Inspired by @StefLhermitte, I used @ESA_EO#Sentinel1 data to make this 18-month animation of Pine Island Glacier @AntarcticPIG. Find a hi-res version for download here: https://t.co/0fmiOhvXBq. Not long until the next calving event. pic.twitter.com/TNlDpuH05g

Meanwhile at Brunt ice shelf.

Did you mean this part, @iceadvices ? pic.twitter.com/ptxbjhOcME