Assessing the sensitivity of major East Antarctic outlet glaciers to recent and future changes in the ocean-climate system

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

Abstract

The Earth's atmosphere and oceans are warming as a result of increased concentrations of greenhouse gases. Glaciers melt when the Earth warms and water that was stored as ice on land runs off into the ocean and increases sea-level. Over the last few decades, measurements have shown that sea-level is increasing by around 3 millimetres per year, and that this is due to the expansion of the warmer ocean water and the runoff from glaciers. In the 20th century, the sea-level contribution from melting ice was dominated by small mountain glaciers and ice caps, but it is now known that the vast ice sheets in Greenland and Antarctica are contributing an equally large amount to sea level and that their contribution is accelerating.

One of the main ways in which ice sheets contribute to sea-level (especially in Antarctica, but also in Greenland) is through rapidly-flowing outlet glaciers that transfer ice from the interior to the margins, where it breaks off as icebergs. Recent measurements, mostly using observations from satellites, have shown that many outlet glaciers are thinning and retreating and, in some cases, their flow is also accelerating. This helps explain why their ice discharge is increasing. These changes in outlet glaciers are complex, but scientists think that they are caused by warmer ocean temperatures and, in some cases, by the landscapes underneath the outlet glaciers, especially if they flow through deep valleys that are below sea level and get deeper inland under the ice.

The most dramatic changes have been observed in Greenland and West Antarctica, which store around 6 and 4 m of sea-level equivalent, respectively. Thus, unlike smaller mountain glaciers, changes in outlet glaciers could contribute several metres to global sea-level, possibly over quite short time-scales (just a few centuries according to some predictions). It is for this reason that a lot of research is aimed at monitoring outlet glaciers in Greenland and West Antarctica. Most of the ice in Antarctica is, however, stored in East Antarctica, which holds a sea-level equivalent of around 53 m. It is perhaps surprising, therefore, that there are so few measurements of outlet glaciers in the East Antarctic Ice Sheet (EAIS), but this is probably because it was traditionally thought to be much more stable than West Antarctica. Recently, however, evidence has been uncovered which indicates that parts of the EAIS, especially those parts that that overlie deep valleys and basins, might have retreated quite dramatically when climate was slightly warmer in the past. Moreover, observations of just one or two glaciers in these same regions indicates that they are also thinning and retreating, similar to those in Greenland and West Antarctica. Thus, there is a small but growing body of evidence suggesting that some parts of the EAIS might also be vulnerable to global warming.

Unfortunately, we do not have enough observations to know exactly what is happening in different parts of East Antarctica and there is a large amount of uncertainty about whether its outlet glaciers are sensitive to changes in the ocean and/or atmosphere. This project has been designed to specifically address this uncertainty. We will use satellite measurements to determine recent changes on some of the largest and most important outlet glaciers from different regions of East Antarctica. This will tell us where the most dramatic changes have taken place and which areas are more stable. We will then use a computer model to see what kind of changes would take place if air or ocean temperatures increase in the future. This will tell us which glaciers are most sensitive and what their contribution to sea level might be over the next few centuries. Even where glaciers are currently stable, it is important to know by how much climate would need to change before they might react. This new knowledge is vitally important to help governments plan for future changes in sea-level.

Planned Impact

Who will benefit from the proposed research?

There are four main groups who will benefit from our research:

1. Scientists and International Scientific Panels/Working Groups
2. Policymakers
3. Teachers, Educators, Schoolchildren
4. General Public

How will they benefit?

1. Scientists from a range of disciplines will benefit from the new knowledge we will generate on the recent and future sensitivity of outlet glaciers in East Antarctica. These are identified, together with several international scientific panels and working groups, under the 'Academic Beneficiaries' section of the Proforma.

2. Our research specifically targets major uncertainties in the dynamics and sea level contribution of the East Antarctic Ice Sheet which is directly relevant to Policymakers. We will deliver the first detailed observations of dynamic change from a widespread sample of major East Antarctic outlet glaciers and, through data-calibrated modelling, provide new projections of their likely impact on near-future sea-level. IPCC draws consensus from scientific papers that we intend to publish, but we will also target policymakers through contributions such as NERC Planet Earth, NERC Science Days, and invitations to local MPs, e.g. Stokes has previously been invited to present results of his research at the House of Commons.

3. Teachers, educators, schoolchildren will benefit from our collaborative impact activities with OASES (Outdoor And Sustainability Education Specialists) North East who have been successfully delivering and promoting outdoor learning and global sustainability education for over 15 years (see 'Pathways to Impact' document). We will work closely with OASES to deliver a 'Children 4 Climate Change' (CC4C) project that will work with the poorest and most vulnerable communities in north east England (see Letter of Support from Joanne Appleby).Through the project, teachers and schoolchildren will receive clear, informative and current information about climate change, explore what young people feel about the issue, and encourage them to think about how we should all respond. The young people will be assisted to ensure their voices are heard through the production of short films that will then be screened within their school and made available on a dedicated 'C4CC' website. We also plan to continue existing activities in secondary/tertiary education where Stokes has given talks in schools and at conferences aimed at educators (e.g. British Association Science Festival) and written articles for secondary education magazines (e.g. 'Physics Review' A-level magazine).

4. The topic of climate change and the enigmatic behaviour of large polar ice sheets has clear potential to engender a wider interest from the general public. Our project will benefit the public in providing an improved understanding and awareness of ice sheets and their role in the global climate system. The C4CC project (see point 3) will involve screenings of climate change films and a dedicated project website. In addition to our more formal collaboration with schools, we will work with an award-winning children's author (see Letter of Support from Darragh Martin) to write a book on climate change in Antarctica (see 'Pathways to Impact'), aimed at young people. Climate change is rarely communicated via this medium in popular culture and we believe there is clear potential to communicate the broad scientific issues in an attractive, exciting and accessible manner. As with previous outputs that have been covered in a variety of national and international media, newsworthy results will be disseminated through University press releases. Indeed, some of our pilot studies on East Antarctica (Miles et al., 2013: Nature; Jamieson et al., 2016: Geology; Langley et al., 2016: Geophys. Res. Lett.) have received widespread coverage in a number of national and international media (BBC Website, Washington Post).

Publications

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Description We have estimated the impact of ice-shelf thinning on ice flow of the Antarctic Ice Sheet and the associated impact of global sea level.
Exploitation Route These findings inform other numerical models and suggest alternative and better ways of numerically calculating the flow of the Antarctic Ice Sheet.
Sectors Environment

URL https://www.the-cryosphere.net/12/3229/2018/tc-12-3229-2018.pdf
 
Title Ua 
Description A numerical ice-flow model partly developed as a part of the project. In use by a number of research groups worldwide. 
Type Of Material Computer model/algorithm 
Year Produced 2018 
Provided To Others? Yes  
Impact The model allows, for example, for the impact of ice-shelf thinning on upstream flow of the Antarctic Ice Sheet to be estimated using data assimilation methods. 
URL https://github.com/GHilmarG/UaSource