Propagation of ocean-driven ice-shelf thinning and consequences for the interior of Antarctica and global sea level.

Lead Research Organisation: British Antarctic Survey
Department Name: Science Programmes

Abstract

By exploiting three important new advances in ice sheet modelling, and major new Antarctic-wide datasets, we aim to predict how far and how fast the observed ocean-driven thinning of floating ice shelves will propagate into the interior of the Antarctic ice sheet, and assess the consequences for global sea level over decadal-to-century timescales. Whereas previous studies have used simplified models, idealised forcing, or limited domains, we will use a comprehensively initialised model of ice flow throughout Antarctica, including all mechanical processes that propagate thinning into the interior, to produce a highly-realistic simulation that can predict the response of the grounded ice sheet to the ice-shelf thinning observed by satellite. We will validate the simulations against further satellite observations, before using them with scenarios of ice-shelf melt, guided by ocean models, to produce a probabilistic forecast of the future sea-level contribution from Antarctica to 2100.

Planned Impact

By reducing uncertainty around the interaction between oceans and ice sheets, and the future contribution of Antarctica to sea level rise, the proposed research will benefit:
1) The Environment Agency in management of the coastal environment.
2) Government departments, e.g. Treasury, DECC, DEFRA, in making decisions about resource allocation.
3) Other partners in the UK Living With Environmental Change partnership (LWEC) in understanding the risks of climate change and assessing options for avoiding or managing such risks. See http://www.lwec.org.uk/ for details of LWEC.
4) Business and industry in making investment decisions about long-lived infrastructure projects.
5) Local Authorities in making planning decisions.
6) The general public in allowing them to make informed decisions about energy use, and in playing an active and informed role in debates about coastal management, climate change, and the allocation of resources by government.
 
Description Improved knowledge of how the ice is flowing within the interior of the Antarctic ice sheet.

Improved techniques for estimating the uncertainty in key model parameters such as the viscosity of ice or the sliperiness of sediment beneath the ice, and new methods for reducing uncertainty in projections of future ice sheet behaviour.

Model simuations confirm that the present climate can drive a slow but sustained sea level contribution from West Antarctica.

Additional submarine melting in newly formed ocean cavities, at rates similar to those observed, can provide a positive feedback to retreat.

For sufficiently intense submarine melting the simulated retreat can accelerate over time, even without ice shelf or ice cliff collapse.

Bayesian methods can be used to provide better information about the probability of sea level contributions from Antarctica.

The future contribution to sea level depends upon the amount of melting that occurs beneath ice shelves, caused by oceanic delivery of heat.
Exploitation Route So far research on this project has focussed on understanding the present day state of Antarctica. This will form the starting point for predictive modelling of how the ice sheet will behave in future under different forcing.
Since the above comment, we have published results from a number of model simulations showing how the Amundsen Sea sector of the ice sheet will behave in future under different forcing.
These findings have been cited by Pattyn et al., Current Climate Change Reports (2017), 3, 174-184 DOI 10.1007/s40641-017-0069-7 as part of a review that emphasises that numerical modeling of the Antarctic ice sheet has gone through a paradigm shift over the last decade.
Sectors Construction,Energy,Environment,Transport
URL https://www.bas.ac.uk/project/ocean-driven-ice-shelf-thinning-in-antarctica/
 
Description Influence on Policy, Practice, Patients and the Public Our article (Arthern, R. J., and C. R. Williams, The sensitivity of West Antarctica to the submarine melting feedback, Geophys. Res. Lett., 44, 2352-2359, 2017) has been cited in the the UKCP18 Marine report (https://www.metoffice.gov.uk/pub/data/weather/uk/ukcp18/science-reports/UKCP18-Marine-report.pdf). UK Climate Projections is a climate analysis tool that forms part of the Met Office Hadley Centre Climate Programme, which is supported by the Department of Business, Energy and Industrial Strategy (BEIS) and the Department for Environment, Food and Rural Affairs (Defra). As noted in the introductory material of the UKCP18 Marine report. https://www.metoffice.gov.uk/pub/data/weather/uk/ukcp18/science-reports/UKCP18-Marine-report.pdf "The UKCP18 marine projections have been devised in consultation with a variety of UK stakeholder groups. The purpose of this report, along with the associated data products, is to facilitate vulnerability assessments to aid coastal decision makers. The emphasis of the UKCP18 marine projections is on changes in coastal sea level, including extreme water levels that arise from storm surges and surface waves."
First Year Of Impact 2018
Sector Environment
Impact Types Societal,Policy & public services
 
Title Fields and parameters related to the flow of ice in the Antarctic Ice Sheet recovered using inverse methods and satellite data 
Description We can learn about the flow of ice in Antarctica by evaluating the key parameters that control the flow speed. These parameters include the basal drag coefficient and the ice viscosity. They can be estimated by adjusting their values so that model velocities at the upper surface agree with satellite observations. This dataset was produced using inverse methods to obtain the parameter values. In this approach a cost function that describes the mismatch between model and satellite data is minimised iteratively by making small adjustments to the parameters at each iteration to improve the fit. The result is better information about the flow field in the Antarctic ice sheet. Once the flow field is available it can be used as an initial state from which begin temporally evolving simulations using the model. A number of different examples are included to show how varying different parameters alters the temporally evolving simulations. The contributing datasets used to constrain the model are listed by Arthern et al (2015) and Arthern and Williams (2017). Multidecadal model simulations span up to 100 years of simulation time. This work was funded by NERC standard grant NE/L005212/1. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
Impact The ice sheet model has now been rewritten in Julia and forms the basis of an open source ice sheet model used for coupled ice/ocean simulations. See https://github.com/RJArthern/WAVI.jl for details. 
URL https://data.bas.ac.uk/full-record.php?id=GB/NERC/BAS/PDC/01632
 
Description Online introduction to project and description of progress so far. 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Introduction to project and description of progress so far.
Year(s) Of Engagement Activity 2015
URL https://www.bas.ac.uk/project/ocean-driven-ice-shelf-thinning-in-antarctica/