Top Antarctic experts update the public on the grim near-term future of Thwaites Glacier.
Thwaites Glacier is one of nine glaciers comprising the highly vulnerable West Antarctic ice sheet. If the western ice cap collapses, it would raise the global sea level by eleven feet.
Thwaites Glacier is the cork keeping the West Antarctic's land ice from emptying into the sea. If it is lost, it will destroy the other eight glaciers, and human civilization will never be the same again.
According to experts who have dedicated their careers to studying a deteriorating glacier nicknamed the Doomsday Glacier, the worst-case scenario is not imminent and may not happen this century. But. There will be enough damage to cause chaos in the near term.
We know there is data of evident and significant ice damage occurring daily to the Thwaites glacial tongue (the marine extension of the land-based glacier). The damage results from warming ocean temperatures melting the Antarctic underbelly, lengthy vertical cavities toward the surface carved into the already weakened Thwaites Tongue and the Eastern and Western Ice Shelves, and abundant meltwater entering the Southern Ocean. The devastating impact on the ice will only deepen as the years and decades unfold.
In recent weeks, satellite imagery revealed a major crack-up of ice in the Amundsen Sea Embayment, of which Thwaites is a significant part. The shattered ice image raised alarm bells about a rapid rise in sea level. The crack-up did not occur on the glacier or shelves but from sea ice and melange ( cemented sea ice and icebergs in the calving front) break up. Both sea ice and the melange are effective in resisting the calving front, keeping the marine extension of the glacier stable. Their loss has resulted in both sea ice and the melange being flushed into the open ocean. Only days ago, the icebergs were anchored to the seabed. In this animation provided by Kris Van Steenbergen, we can see that the icebergs are indeed moving; each is about 1 kilometer (.62 miles) in size. Kris also shared animated imagery of the "tongue glacier itself is doing at the bottom left here! An important signal is that the glacier wants to push out ice quickly but cannot now because the glacier tongue still seems to be fixed." As an aside, Kris shares a view of the Crossen ice shelf pushing the ice mass to the east. The imagery is worrisome and may mean that back pressure has begun to fail at the location west of the Thwaites tongue.
The Bluesky thread below is from Rob Larter. Rob's bio is as follows:
Larter began his ITGC work as a lead principal investigator on the THOR project. He and his team will investigate sediments deposited in the seas near the Thwaites Glacier, and reconstruct past changes in environmental conditions and the glacier's response, adding context to projections of future change.
As of spring 2022, Larter is a co-principal investigator on THOR and has assumed the UK lead PI role for the Science Coordination Office, joining Ted Scambos of the US.
Rob Larter has taken the time to address the fear of a massive breakup at Thwaites Glacier, resulting in catastrophic sea level rise. Below is his Bluesky thread, which is updating the current situation. It is a rare treat from one of the most brilliant minds on Antarctica's ice cap.
Rob's bluesky thread is below. There are gifs that can not be posted here.
Through the International Thwaites Glacier Collaboration more than a hundred researchers have been conducting studies on many aspects of the glacier over the past six years. Overall, our results paint a grim picture for the future of the glacier and thus the wider West Antarctic Ice Sheet.
We expect the rapid retreat of the glacier observed over the past couple of decades to continue and to accelerate during the latter part of this century and beyond. This sector of West Antarctica will contribute increasingly to an accelerating rate of global sea-level rise.
The current changes that some people are getting agitated about are occurring on the small remnant of ice shelf - a floating extension - that projects from the front of Thwaites Glacier. The ice shelf has been progressively thinning and fracturing over many years.
Until a couple of years ago there were two distinct sectors of ice shelf in front of Thwaites Glacier, separated by a "shear zone" that allowed them to move independently. In front of the fast-flowing central axis of the glacier the Thwaites Glacier Tongue repeatedly grew and broke off.
Up until the early years of this century the Glacier Tongue typically grew to a length of more than 70 km before calving as a giant tabular iceberg. The last tongue became iceberg B22a. In more recent years it has extended a much shorter distance before each time it broke off.
Ice flowing from the axis of the glacier is now highly fractured, so instead of forming a tongue it breaks very soon after flowing into the ocean. As a result, this part of the glacier is now fronted by a mélange of icebergs (typically 1–2 km across) and sea ice.
This leaves the Thwaites Eastern Ice Shelf, which extends from the slower flowing eastern part of the glacier, as the only intact area of ice shelf at the front of the glacier.
Several years ago scientists studying the Thwaites Eastern Ice Shelf as part of the International Thwaites Glacier Collaboration identified that changes underway there would lead to it being lost soon, probably within 10 years. tc.copernicus.org/articles/16/…
Since this research began, a new shear zone that cuts diagonally across the ice shelf has developed rapidly, allowing flow of the main part of the ice shelf to accelerate. This has resulted in substantial change over the past two and a half years, as shown by this pair of Sentinel-1 images.
Here are those two images as an animated gif, clearly showing the changes that have occurred from September 2022 until now. So what does this mean for the future of the ice shelf and the glacier itself?
The ice shelf is undoubtedly going through its death throes. Breakup events observed on other ice shelves show the exact timing of final break up is impossible to predict. Fortunately, however, unlike many other ice shelves, this one has not been doing much recently to slow the flow of the glacier.
Over the past couple of years, while the ice shelf has accelerated seaward, the rate of flow of the glacier has not increased in response. The fact that this ice shelf is not holding back the glacier is shown most clearly by the development of large rifts across the upstream part of the ice shelf.
These observations are described further in this explainer article and the research paper it includes a link to. thwaitesglacier.org/news/thwaite…
So in summary, yes the Thwaites Eastern Ice Shelf is expected to be lost sometime over the next couple of years, perhaps even this Antarctic summer. However, this is not expected to result in an abrupt increase in the rate of ice loss from the glacier.
In the longer term though, over the rest of this century and beyond, the outlook from Thwaites Glacier and the wider West Antarctic Ice Sheet is grim. Progressively increasing rates of ice loss, contributing to an accelerating rate of global sea-level rise, are expected.
Note: I posted this article on Medium.