Change to #ThwaitesGlacier, #Antarctica constitutes the largest uncertainty in #sealevel rise forecasts. The Science Coordination Office of the International Thwaites Glacier Collaboration recently summarised some key findings in a briefing document - https://t.co/jAjLsl1Hog

Today the 2025 State of the Cryosphere report was published by over 50 leading cryosphere scientists. An urgent warning about the global consequences of the meltdown of ice, including the risk of shutdown of the Atlantic Ocean current system #AMOC. 🌊 https://t.co/lnERZaNdje

An Antarctic glacier shrank by nearly 50% in two months, the fastest retreat in modern history. It could spell trouble for sea levels, report finds. https://t.co/8njVjmuH8V

A lot of new knowledge has been gained through research conducted as part of the ITGC, but much more still remains to be done. The costs of such research are minor compared to the costs of adaptation investments that depend on the information it will provide for reliable planning

• Where and when will glacier retreat accelerate? • How stable are the shear margins that bound Thwaites Glacier? • How much of what we have learnt about the Thwaites system can be translated to improve our understanding of other ice shelf/glacier systems globally?

• How do tidal pumping, meltwater drainage, sediments and ice in grounding zones interact to affect melting, ice flow and glacier retreat? • Where and when might tall, rapidly-calving ice cliffs form during Thwaites Glacier's retreat?

• How do ice-ocean interactions in the hidden world beneath ice shelves affect melt rates, and therefore control their ability to hold back glacier flow? • How will the slope, irregularities and geology of the bed affect future ice flow and glacier retreat?

Much further research is still needed to better define how fast Thwaites Glacier will contribute to future sea-level. Some key questions are • How will conditions in the area evolve in the coming decades? • Is the retreat of Thwaites Glacier now really unstoppable?

Even without ice cliff-driven retreat or tidal intrusions into the grounding zone though, latest models predict continuing rapid ice loss this century that will accelerate further through the next century, e.g. https://t.co/ZBFTLLyiQy

Major advances in modelling have been made, but new challenges have also been identified. One ITGC modelling study suggests that glacier collapse in this century through Marine Ice Cliff Instability is less likely than some had previously suggested. https://t.co/UXqBqqV7Vs

Critical data to support improved ice sheet modelling have been gathered, including on the characteristics of the glacier bed and on what controls its lateral boundaries. https://t.co/iMrMcfDdB9 https://t.co/qGn3WduMOb

Analyses of rocks obtained by drilling thru the ice near the edge of a nearby glacier show ice thickened after past thinning several thousand years ago. However, recovery took several millennia and a return of conditions in which it took place is unlikely. https://t.co/rYgDX50uv6

Marine geological studies show ice shelves in front of Thwaites and Pine Island glaciers detached from seabed ridges ("pinning points") in the 1940s, initiating the modern retreat. However, most acceleration of ice loss has occurred since the 1980s. https://t.co/kud1C9InlV

Imprints on the seabed left by the retreat of the glacier indicate a past episode of retreat even faster than is seen today when its grounding zone separated from a seabed ridge. https://t.co/lagsRTGSiB

Previously unrecognised tidally-driven seawater intrusions into the base of the glacier (its “grounding zone”) may hasten melting and retreat and this process is not included in current ice sheet models. https://t.co/oWxrUFwOI8

Robotic underwater vehicles discovered a host of new melt processes and imaged the undersides of ice shelves. Representing this new knowledge in ice sheet models is now an important challenge. https://t.co/dXQML2CBs3 https://t.co/zUbntSUzaD https://t.co/zLtLZFLYu0

In this and following posts I summarise some key findings. Firstly, the last remaining area of ice shelf in front of Thwaites Glacier, the Thwaites Eastern Ice Shelf, is nearing break-up. https://t.co/WjVph8OxSW

This is because results show some processes are more complex than previously recognized, others we still don’t have enough data on or clear enough understanding of, and still others that are newly identified.

Latest models incorporating ITGC results indicate continuing rapid grounding zone retreat that will eventually accelerate as Marine Ice Sheet Instability takes hold. The possibility that ice loss will occur faster than current models predict cannot be discounted though.

Put simply, the outlook is grim. It is highly likely that Thwaites Glacier will eventually be lost, which will destabilise adjoining parts of the West Antarctic Ice Sheet, increasing the committed long-term rise in global mean sea level by more than 3 m.