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NSFPLR-NERC: Processes, drivers, predictions: Modeling the response of Thwaites Glacier over the next century using ice/ocean coupled models

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Geosciences

Abstract

We propose to conduct coupled ice-ocean numerical simulations of Thwaites Glacier (TG) to predict its future contribution to global sea level change, and to provide both statistical and structural error estimates using three state-of-the-art ice flow numerical ice-flow models (ISSM, Úa and STREAMICE) coupled with the ocean model MITgcm. We will implement and improve the representation of several key physical processes (calving, ice damage, mechanical basal conditions) that have either not been included, or poorly represented in previous ice-flow modelling work.

We will quantify the relative role of different proposed external drivers of change (e.g., ocean-induced ice-shelf thinning, loss of ice-shelf pinning points), and explore systematically the stability regime of TG with the aim of identifying internal thresholds separating stable and unstable grounding line retreats.
Using inverse methodology, we will produce new physically consistent high-resolution (300 m) data sets on ice-thicknesses from available radar measurements. Furthermore, we will generate several new remote sensing data sets on ice velocities and rates of elevation change. These will be used to constrain and validate our numerical models, and will also be highly valuable as stand-alone data sets.

Planned Impact

We will engage with policy makers and the public in several ways. Individually, each academic institution will make use of local options and opportunities available to them. Jointly, we will commission the production of series of short high-quality videos explaining to the general both the results of our work and the generally modelling methodology.

PI Mathieu Morlighem and Co-PI Daniel Goldberg will each share the results of this study through seminars dedicated to undergraduate students and include this project in their respective courses "Modeling the Earth" (General Education class, UC-Irvine) and "Ice and Climate" (Geography course, UoE), thereby exposing many undergraduate and graduate students to the field of glaciology for the first time. In addition, the ISSM team organizes a yearly workshop. This workshop aims at fostering discussions in ice sheet modeling, where new results specific to this field can be presented. It also showcases the new capabilities developed for ISSM, and involves young research scientists that are starting in the field of Cryospheric Science. Within this workshop, time will be allocated to present the new capabilities resulting from this project, and significant scientific results in which ISSM is involved. This workshop will therefore be a platform for presenting the software and scientific products of this project to a young audience. Finally, we plan on integrating a Thwaites Model to the Virtual Earth System Laboratory, a platform used by high-school and middle school students to model ice sheets and glaciers with a simple web-based interface. The Thwaites model will be a simplified version of our modeling effort and will allow the public to "play" with the model and test its sensitivity to ocean warming.

Co-PI Das is actively involved in outreach and classroom activities through Lamont Open House, World Science Festival and museum activities at NY. She will use these venues for reaching out to the public about the science and results of this project. Policy makers will be targeted through contributions that face this audience, e.g. NERC Planet Earth and NERC Science Days.

To reach the general public in much broader way we plan the production of professional videos for a specific project-related YouTube channel. As a project involving numerical models and big data, our proposed research is exceptionally well suited for visually compelling presentations depicting physically realistic-looking flow of ice masses. These can be generated directly from our proposed model runs. We aim to target informed audience interested in global climate issues, and to produce series of highly-professional videos. These will explain both the results of our science, but also demystify how ice-flow modelling is done. We will explain our work in simple terms, but also include more background information than one would typically expect to be provided in the traditional news media. Together with the BAS press office we have already had informal discussions with companies generating computer graphics for a number of BBC documentaries and have arrived at realistic cost estimates. We understand that as a part of this NSF+NERC call there may well be an argument for a combined outreach plan, and we can envision our plans to from a part of such a jointed effort.

Publications

10 25 50
 
Description The project focussed on examining the key processes and risks associated with Thwaites Glacier, using robust modelling methodologies internally validated with three separate ice-sheet models.

The findings of the project suggest that many "doomsday" scenarios regarding Thwaites may not actually be real hazards, but that ocean-driven ice loss is a real threat in coming centuries. Gudmundsson et al 2023 focussed on the potential "collapse" of Thwaites Ice Shelf in the coming decades. Using three models we established that whether this occurs or not, losses are principally driven by ice-ocean interactions in the next century. Morlighem et al (2024), in collaboration with another ITGC project, showed that the proposed mechanism of ultra-fast ice loss, the Marine Ice Calving Instability, is unlikely to occur -- mainly because ice-shelf removal, thought to trigger the process, instead results in rapid thinning and advance which offsets the instability.

In progress is a coupled ice-ocean modelling experiment by 3 separate models to investigate the impact of emissions scenario (RCP26 vs RCP85) on losses from Thwaites over the next century. Edinburgh's investigations have completed but partners' have not -- still, it appears that regardless of scenario loss rates from Thwaites will increase up to 5-fold by 2100. Our recent paper by Gourmelen et al (2025) suggests that subglacial runoff due to lake drainage could accelerate this further.
Exploitation Route it informs that the biggest threat to thwaites glacier is ice ocean interactions -- which will influence others not to focus on ice shelf collapse or marine cliff collapse
Sectors Environment

URL https://www.nytimes.com/2024/08/21/climate/antarctic-ice-cliff-collapse.html
 
Description Findings have been presented in a SAGES (Scottish Assoc of Geoscience Env and Society) public outreach event, attended by 100 members of the general public More recently there has been media coverage of outputs. In each, the authors engaged with the media. https://www.nytimes.com/2024/08/21/climate/antarctic-ice-cliff-collapse.html https://www.science.org/content/article/doomsday-may-be-delayed-antarctica-s-most-vulnerable-glacier https://eos.org/research-spotlights/phytoplankton-shield-ice-shelves-from-summer-heat
First Year Of Impact 2024
Sector Environment
Impact Types Societal

 
Title Amundsen Sea sector MITgcm/WAVI coupled model output forced with idealised ocean boundary conditions over 180 years 
Description This data set represents the model results plotted in the figures in Bett et al. (2024), produced using the MITgcm/WAVI ice/ocean coupled model. The model domain is the Amundsen Sea sector, where the simulations start in approximately the year 2015 and run for 180 years. Simulations are forced using idealised ocean boundary conditions which represent cold and warm conditions, along with a third extreme case where no ice shelf melting is applied. These simulations were produced in order to examine the ice/ocean processes that occur during future evolution of the region. For full descriptions of the results plotted in each figure see Bett et al. (2024). Funding was provided by NERC Grant NE/S010475/1, ITGC THWAITES MELT (NE/S006656/1), ITGC THWAITES PROPHET (NE/S006796/1) and the European Union Horizon 2020 grant PROTECT (869304). 
Type Of Material Database/Collection of data 
Year Produced 2024 
Provided To Others? Yes  
URL https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01837
 
Title Model data for "The transferability of adjoint inversion products between different ice flow models" 
Description Inputs and outputs of experiments run for the paper "The transferability of adjoint inversion products between different ice flow models", published in The Cryosphere. Geometry inputs are from BedMachine Antarctica v.1 (Morlighem, 2019). Surface mass balance inputs derive from RACMO2.1 (Lenaerts et al., 2012). Velocity measurements and errors derive from a dataset first described in Mouginot et al. (2014). 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
URL https://zenodo.org/record/4701343
 
Title Model data for "The transferability of adjoint inversion products between different ice flow models" 
Description Inputs and outputs of experiments run for the paper "The transferability of adjoint inversion products between different ice flow models", published in The Cryosphere. Geometry inputs are from BedMachine Antarctica v.1 (Morlighem, 2019). Surface mass balance inputs derive from RACMO2.1 (Lenaerts et al., 2012). Velocity measurements and errors derive from a dataset first described in Mouginot et al. (2014). 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
URL https://zenodo.org/record/4701342
 
Title Model output from Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier 
Description This model output dataset accompanies the draft paper 'Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier'. 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
URL https://zenodo.org/record/5105687
 
Title Model output from Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier 
Description This model output dataset accompanies the draft paper 'Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier'. 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
URL https://zenodo.org/record/5105686
 
Title hockenden97/Inverting_ice_surface: Paper release 
Description This code accompanies the draft paper 'Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier'. 
Type Of Technology Software 
Year Produced 2021 
URL https://zenodo.org/record/5494600
 
Title hockenden97/Inverting_ice_surface: Paper release 
Description This code accompanies the draft paper 'Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier'. 
Type Of Technology Software 
Year Produced 2021 
URL https://zenodo.org/record/5494599