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

Lead Research Organisation: Northumbria University
Department Name: Fac of Engineering and Environment


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.
Description The Antarctic ice sheet is currently losing mass, but the causes for the mass loss remain unclear. It has been suggested that the reduction in the thickness ofthe floating ice shelves that surround the ice sheet, for example, due to ocean warming or changes in ocean circulation, may be responsible for some of the observed ice loss. However, this hypothesis has remained untested. Here, we use a state-of-the art numerical ice flow model to calculate the direct mass loss due to observed changes in ice shelves between 1994 and 2017. We find that the magnitude and spatial variability of modelled changes of inland ice are in good agreement with observations, suggesting that a substantial portion of the recent ice loss from the grounded Antarctic ice sheet has been driven by changes in its thinning ice shelves. The process we consider (ice shelf buttressing) relates to changes in forces within the ice alone and is therefore effectively instantaneous (i.e., only limited by the speed of stress transition within the ice). Besides providing a possible explanation for a large part of the ongoing mass loss, this finding also shows that we are not protected against the impact of the Antarctic ice sheet on global sea levels by a long response time.
Exploitation Route We've quantified the impact of ice-shelfs on upstream flow of the Antarctic Ice Sheet. This has a number of possible uses. For example, this could be used to select areas most important for additonal field observations.
Sectors Environment

Description Our findings have generated considerable interest in the press. BBC, for example, had a article on our GRL paper: https://www.bbc.co.uk/news/science-environment-50625396 And out Nature paper on ice-thickness estimates was widely reported on, for example: https://nationalpost.com/news/world/denman-glacier-deepest-land-canyon-on-earth-antarctica
First Year Of Impact 2020
Sector Environment