Improved Prediction of 21st Century West Antarctic Climate Change: the Role of the Amundsen Sea Low

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

Abstract

The West Antarctic Ice Sheet contains over 2.2 million cubic kilometers of ice, which if it all melted would raise global sea level by about 5 metres. Over the last few decades West Antarctica has experienced a significant warming. Air temperatures have increased across the surface of the ice sheet, but in addition warmer ocean currents have been melting the ice sheet where it reaches the ocean. The net result has been that some of the ice flowing down to the coast of West Antarctica has been accelerating and thinning so that the coastal area of West Antarctica is now contributing almost 10% to the current rise in global sea level.
The climate of West Antarctica is strongly influenced by the storms over the Southern Ocean between the Antarctic Peninsula and the Ross Sea which force warm, maritime air across the ice sheet. There are a large number of storms in this area of the Southern Ocean which are collectively called the Amundsen Sea Low. This is a highly variable feature and is influenced by the ozone 'hole' and climatic conditions across the tropical Pacific Ocean.
It is extremely important to know how the climate of West Antarctica will change over the coming century so that we can produce accurate estimates of sea level rise. However, the only tools we have to predict the future are computer models that simulate the atmosphere, ocean and ice across the Earth. These models run as part of initiatives such as the Intergovernmental Panel on Climate Change have a relatively coarse spatial resolution of about 200 km, which is not sufficient to accurately resolve the complex mountainous terrain of areas such as the coast of West Antarctica. For this project we will run a model with a resolution of 10 km through the 21st century to create the most detailed information yet produced of how temperature, snowfall and wind speed/direction will change as greenhouse gas concentrations increase and the ozone hole recovers. Such data will be of value to those modelling the West Antarctic Ice Sheet and enable the production of better predictions of how the ice sheet will change over the coming century and the contribution it will make to sea level rise.

Planned Impact

The research proposed here will have a wide range of economic, societal and academic impacts, with the main beneficiaries being:

- The Intergovernmental Panel on Climate Change (IPCC). The IPCC is the primary focus for assessing past and potential future climate change and its reports are definitive reviews of humankind's current understanding of climate change science. They have identified the West Antarctic Ice Sheet's contribution to sea level rise as one of the most significant unknowns for the coming decades. The outcome of this research will be cited by future IPCC reports.

- Policy makers. Improved predictions of Antarctic climate change and especially the contribution to sea level rise will aid planning by policy makers. We will contribute to the DECC 'Tackling Climate Change' strategy. Mitigation plans can be refined and the work will aid the formulation of greenhouse gas emission targets.

- The general public. Climatic change across West Antarctica and the consequent rise in sea level has been reported extensively by the media and is of wide public interest. This work will result in greater public awareness of the complex nature of the changes taking place and the influence of both natural and anthropogenic forcing.

- The academic community. The primary predicted quantities of temperature and precipitation for West Antarctica will be of great value to many areas of polar science. The data will be used to drive ice sheet models, but will also be of value to oceanographers, sea ice researchers and marine biologists concerned with climate change who require knowledge of the changing nature of precipitation and temperature and the hydrological cycle.

Activities planned that will engage with the above communities include:

- Publication of the research results in the peer reviewed and popular literature, along with engagement in the synthesis activities of organisations such as the Scientific Committee on Antarctic Research.

- Presentation of the results at international scientific conferences, and also at UK meetings and to regional organisations and schools.

- Many news film crews visit the Antarctic to report on climate change there and we would ensure that our research results were promulgated during interviews with scientists on the bases.

- BAS has good links with the UK Department for Energy and Climate Change and we will ensure that research results contribute to the policy making process.

- We plan to host two workshops during the project, the first of which will fully exploit the cross disciplinary nature of the planned research bringing together meteorologists, glaciologists and oceanographers. The second workshop will involve the broader interested community, including energy policy makers, insurance companies, as well as scientists.

Publications

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Raphael M (2016) The Amundsen Sea Low: Variability, Change, and Impact on Antarctic Climate in Bulletin of the American Meteorological Society

 
Description We have developed a high horizontal resolution, atmosphere-only climate model tuned for the specific conditions of West Antarctica. Runs of 10 days were carried out and compared with in-situ observations.A 35 year hindcast model run starting in 1979 was carried out to simulate past conditions and investigate the factors that influenced summer temperatures across West Antarctica. We showed that El Nino events across the tropical Pacific Ocean gave increased summer ice melt over the ice shelves. Westerly winds off the Amundsen Sea Embayment are associated with greater melt under the ice shelves and we shows that there was a high frequency of westerlies with a positive phase of the Southern Annular Mode (SAM) and an eastward shift of the Amundsen Sea Low. We showed that the projected future increase in El Niño episodes and positive SAM could therefore increase the risk of disintegration of West Antarctic ice shelves.
Exploitation Route Very high horizontal resolution model fields of temperature and precipitation are of value in many fields, including glaciology, oceanography and Earth system science studies and we anticipate that the fields produced by this project will be used in these science disciplines.
Sectors Environment