Dynamical control on the response of Pine Island Glacier

Lead Research Organisation: University of Cambridge
Department Name: Scott Polar Research Institute

Abstract

It is expected that sea-level rise will impact coastal communities worldwide over the coming decades to centuries. In the UK, the vulnerability of coastal communities and assets is best characterised in terms of the likely frequency of the over-topping of sea-defences. For example, when they were built, the sea-defences for the city of London (including the Thames Barrier) were designed to protect London from all except the 1-in-1000 year flood event. A rise of 50 cm in global sea level will reduce this level of protection to 1-100 years, and a rise of 100 cm would reduce it to 1-in-10 years.

Pine Island Glacier is one of five glaciers in West Antarctica that are currently contributing sea-level rise at a significant and accelerating rate. The portion currently affected by thinning contains sufficient ice to raise global sea-level by around 25 cm - its neighbours account for another 50 cm.

Given the rate of ice-loss and the potential implications for sea-defence planning there is a clear requirement to understand and predict the future of Pine Island Glacier and its neighbours. However, as highlighted by the Intergovernmental Panel on Climate Change (IPCC, 2007), understanding the way that dynamic changes are transmitted through the glaciers draining ice sheets is so poorly understood that the IPCC believed it was the least well understood, and potentially the largest, contribution to sea-level rise in the coming century.

ISTAR-C will directly address this lack of knowledge, by seeking to understand the processes that are responsible for transmitting the effect of thinning of the floating ice shelf, upstream such that thinning can now be seen on much of the trunk and tributaries of Pine Island Glacier.

ISTAR-C will also use the most up-to-date methods available to measure the properties (rock-type and water-content) of the bed beneath several locations on Pine Island Glacier to determine their influence on the propagation of thinning. We will test the hypothesis that it is these bed conditions that are responsible for the fact that the tributaries of Pine Island Glacier appear to be thinning at different rates. Testing this hypothesis will give us a much better understanding on which to predict the future magnitudes of ice-thinning rates for the glacier.

To achieve these objectives we will collect data from Pine Island Glacier during two field seasons. These will include precise measurement of variations in ice-flow from the ice-shelf up the glacier and into its tributaries. We will image the bed of the glacier using radar and seismic techniques, and use satellite remote sensing to measure the changing configuration of the glacier in areas that cannot be accessed on the ground. We will use the data we have collected to drive and verify a set of computer simulations of the dynamics of Pine Island Glacier. Each of these will test a particular aspect of the glacier flow, and allow us to test our current knowledge and hypotheses against real data. The models that emerge from the exercise will be demonstrably more reliable in simulating past changes on the glacier, and thus have reduced uncertainty in predicting the future evolution of such changes, and the consequential contribution to sea-level rise.

Overall, this programme will deliver significant improvements in understanding of how glaciers in general interact with their beds, and very specific lessons about one of the most rapidly-changing and significant glaciers on the planet, Pine Island Glacier.

Planned Impact

The research undertaken in iSTAR-C will improve understanding of the causes of rapid change observed in parts of the West Antarctic ice sheet (WAIS) and how these may contribute to sea-level rise in future. While production of sea-level rise projections is not included within iSTAR-C, this programme will deliver understanding that underpins such projections, and will reduce uncertainty, and increase confidence, in those projections. Thus, the most significant economic and societal impacts of iSTAR-C will be realised as the science outcomes from iSTAR-C are taken up by beneficiaries beyond the immediate colleagues of the Co-Is; there are researchers and non-research scientists and engineers, who are directly undertaking sea-level rise projections.

Within this group we identify several key beneficiaries who will be users of iSTAR-C outcomes.

1. Academic researchers: (e.g., Proudman Oceanographic Institute, UK Climate Impacts Programme) who have a role in producing local, regional and global sea-level projections, and delivering to users.

2. Intergovernmental Panel on Climate Change (IPCC). The IPCC is by far the most influential group synthesising and delivering sea-level rise projections to policy-makers.

3. Governmental and non-governmental advisors. (E.g.; Dept. of Energy and Climate Change, UK Environment Agency) closely monitor science regarding sea-level protection and are influential in bringing science in the agenda of policy-makers.
Engaging with these and similar groups will maximise the value of iSTAR-C.

In an even wider frame, iSTAR-C and projects like it, which seek to improve the underlying science on which we base our projections of future state of the planet, should play an important role in re-establishing public confidence in science. The nature of the iSTAR-C programme, which focuses on an exciting work in an inspiring area, and on current and unarguable changes in the Earth System, will draw the attention of many people not normally turned on by science. This will give iSTAR-C a great opportunity to engage with individuals and we will not squander this opportunity. We will seek to present and frame iSTAR-C outcomes without policy-prescriptive implications, but in a spirit of informing rational evidence-based debate. We will seek a dialogue with groups and individuals who share this goal.
 
Description The research in this project involves numerical modelling of ice flow based on data acquired by collaborating institutions in Antarctica. The field seasons took place on Pine Island Glacier during the austral summers 2013-14 and 2014-15. Data collected on these expeditions were processed during 2015-17 and passed on to numerical modellers who used them improve the quality of their models and make more robust predictions. Achievements to date include: 1) development of the computational framework needed to model the flow of ice and meet project objectives, 2) integration of essential new processes in the Community Ice Sheet Model (CISM), and 3) successful testing of the improved CISM.

The modelling outcomes from the grant revealed contrasting hydrological controls on bed properties during the acceleration of Pine Island Glacier in the 1990s, 2000s and 2010s. We found the central part of the glacier bed to be weaker; yet the research also showed regions of increased basal resistance to flow along hydrological pathways. Many of these pathways followed the shear margins that separate the fast flowing ice in the glacier's trunk and tributaries from the surrounding slow moving ice. The work therefore showed that the hydrology and shear margins collectively act as a stabilisation mechanism that dampens the glacier's response to grounding line retreat and interactions with the ocean.
Exploitation Route The Community Ice Sheet Model (CISM) used in this project is part of the Community Earth System Model (CESM). Both models are based on freely available code, which means that code developments in this project directly benefits the users of CISM and CESM.
Sectors Environment,Government, Democracy and Justice

URL http://www.spri.cam.ac.uk/research/projects/istar/
 
Description This impact from this project hinges on the outcomes from numerical modelling of Pine Island Glacier, which commenced in 2016 subsequent to the full acquisition of data during the iSTAR field campaigns in 2013/14 and 2014/15. The Community Ice Sheet Model (CISM) was configured and applied to Pine Island Glacier, and modelling outcomes reveal contrasting hydrological controls on bed properties during the glacier's acceleration. The work showed that hydrology and dynamics of shear margins are stabilising the glacier's response to grounding line retreat and the ice sheet's interaction with the ocean. In terms of non-academic impact, the work has informed the general public through social media and outreach at the Polar Museum in Cambridge, while helping policy-makers and assisting with the mitigation of global sea level rise.
First Year Of Impact 2018
Sector Environment,Government, Democracy and Justice
Impact Types Societal

 
Description Bridging grant from the Isaac Newton Trust
Amount £42,609 (GBP)
Funding ID 12.22(i) 
Organisation University of Cambridge 
Sector Academic/University
Country United Kingdom
Start 09/2012 
End 09/2014
 
Description Cambridge - Canterbury international research collaboration 
Organisation University of Canterbury
Department Gateway Antarctica
Country New Zealand 
Sector Academic/University 
PI Contribution This collaboration provided a new network of scientists from UK and New Zealand. The scientists are collaborating on developing new geophysical techniques for exploration of glaciers and ice shelves in Antarctica.
Collaborator Contribution The partner provided financial support to Dr Poul Christoffersen and Dr Marion Bougamont, who were awarded international scholarships and spent five months at Gateway Antarctica in Christchurch, New Zealand, in 2017.
Impact During the visit, Dr Christoffersen gave three seminars, one conference presentation and one public lecture. Dr Bougamont gave two seminars and one conference presention.
Start Year 2017
 
Description Panel debate ("ICE") on BBC's "The Forum" broadcast on World Service and Radio 4 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact In this 45-minute programme, I was able to carefully explain my work in polar regions to the listeners while debating the consequences of climate change with the presenter and the other panelists.

This radio programme reached a lot of listeners in the UK and abroad via multiple broadcasts on BBC Radio 4 and the BBC World Service. A Christmas repeat on BBC Radio 4 (Saturday 28 December 2013) shows wide public interest.
Year(s) Of Engagement Activity 2013
URL http://www.bbc.co.uk/programmes/b03m8612
 
Description Research on ice-sheet stability featured as highlight in Nature Climate Change 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact The article "Reactivation of Kamb Ice Stream tributaries triggers century-scale reorganization of Siple Coast ice flow in West Antarctica" by Bougamont et al. was selected as a Research Highlight by the editors of Nature Climate Change. The article's main findings was summarised as a Research Highlight in Nature Climate Change (vol. 5) under the title: "West Antarctic ice stability".
Year(s) Of Engagement Activity 2015
URL http://www.nature.com/nclimate/journal/v5/n11/full/nclimate2857.html
 
Description Research on ice-stream flow featured as highlight in Eos Magazine 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact The article "Variable deceleration of Whillans Ice Stream, West Antarctica" by Beem et al. was selected as a Research Highlight by the editors of Journal of Geophysical Research. The article's main findings was summarised as a Research Spotlight in Eos magazine (vol. 95 no. 21) under the title "Antarctica's Whillans Ice Plain ice flows are highly variable".
Year(s) Of Engagement Activity 2014
URL http://onlinelibrary.wiley.com/doi/10.1002/2014EO210015/full
 
Description Research on subglacial lakes featured as highlight in Eos Magazine 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact The article - Significant groundwater contribution to Antarctic ice streams hydrologic budget - by Christoffersen et al. was selected as a Research Highlight by the editors of Geophysical Research Letters. The article's main findings was summarised as a Research Spotlight in Eos magazine (vol. 95 no. 35) under the title: Tracking the sources and sinks of Antarctica's subglacial waterways.
Year(s) Of Engagement Activity 2014
URL http://onlinelibrary.wiley.com/doi/10.1002/2014EO350021/full