Thread by @StefLhermitte

New paper 'Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment' 🇦🇶 just came out in @PNASNews. We use 🛰️ to show structural weakening of the Pine Island and Thwaites ice shelves and its impact on the mass loss of these glaciers pnas.org/content/early/…

More background and videos on the damage processes and why they matter on tudelft.pageflow.io/pig-damage. Thx also to @Sainan_Sun @bert_polar @NASA_ICE @EtienneBerthie2 @FrankPattyn @JanWuite @NASA_ICE @CopernicusEU

Although I recommend to check tudelft.pageflow.io/pig-damage, perhaps also here a short thread on our results [1/n].

We use satellite imagery to show how the shear margins of both @AntarcticPIG and @ThwaitesGlacier have weakened. Here you see a @NASA_Landsat 🛰️ time lapse of @AntarcticPIG showing how the shear margin is tearing apart [2/n]

A similar weakening can be seen on @ThwaitesGlacier where the shear margin between eastern ice shelf and glacier tongue turned into a complete damaged zone [3/n]

We hypothesize that this damage preconditions these ice shelves for further disintegration. First, because it already compromises the integrity of both ice shelves. [4/n]

An example of this preconditioning can be seen in the unprecedented retreat of the @AntarcticPIG ice shelf front over the last years where the ice shelf lost 30% of its area. [5/n]

Second, because the weakening due to damage makes the future response of both ice shelves more sensitive to varying and extreme future atmospheric, oceanic, and sea ice conditions. [6/n]

Third, because the damage initiates a feedback process, where damage enhances speedup, shearing, and weakening, hence again promoting additional damage. [7/n]

To assess the importance of this damage feedback, we ran the BISICLES ice sheet model ice sheet model in an idealized setup with different weakening scenarios. [8/n]

The model results highlight the importance
of the damage feedback as a driver for ice shelf instability and grounding line retreat. E.g. the damage model runs result in a stronger grounding line retreat (up to 200%) than the model runs with only strong oceanic melting. [9/n]

This illustrates that weakening these glaciers at their most vulnerable locations, as can be seen in the satellite observations, is a very effective way of causing additional grounded ice mass loss from Pine Island and Thwaites glaciers with important future implications. [10/n]

It also underlines the need for incorporating these feedback processes, which are currently not accounted for in most ice sheet models, to improve sea level rise projections. [11/n].

Bonus: If you want to see how this damage looks like from an airplane? Check out this video made by @NASA_ICE on their Operation IceBridge flight over @AntarcticPIG in 2019 (svs.gsfc.nasa.gov/13441) [The End / 12]