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Antarctica and Climate Change

This article appears in Geoscientist Volume 15 No.2 P 6-7 Website www.geolsoc.org.uk

Colin Summerhayes Email: cps32@cam.ac.uk
Scientific Committee on Antarctic Research (SCAR)

The international body responsible for the co-ordination of scientific research in Antarctica (SCAR, the Scientific Committee on Antarctic Research) has recently reorganised its scientific research agenda to focus its future efforts on five major scientific research programmes. Two of these deal with the evolution of the Earth’s climate system, one with the present day and the Holocene; the other with the Cenozoic and Pleistocene. National delegates representing the 32 SCAR Member countries approved the programmes when they met in their 28th session during the week of October 3-8, 2004, in Bremerhaven, Germany. Details of the programmes are available on the SCAR web site at http://www.scar.org.

The Antarctica and the Global Climate System (AGCS) program will investigate how the atmosphere and the ocean connect the climate of the Antarctic to that of the rest of the world. It will use atmospheric and oceanic data, climate signals from ice cores dating back up to 10,000 years, satellite data and the output of global and regional coupled atmosphere-ocean climate models, to understand how the present climate system works, and how it is affected by human activities, and to develop forecasts to 100 years in the future.

Fifty years ago, at the time of the International Geophysical Year (1957-58) the Antarctic was thought of as rather isolated from conditions at more northerly latitudes, but recent data and model outputs show that Antarctica is closely coupled to the global climate system. In the southern hemisphere, Antarctica and its surrounding Southern Ocean are the main sinks for heat arriving at the equator from the sun and moving towards the poles. Although 80% of the heat is carried by the atmosphere, and only 20% by the ocean, the Antarctic Circumpolar Current (ACC), which is four times as big as the Gulf Stream, inhibits the poleward flux of heat via the ocean and so plays an important role in keeping the continent cold.

Antarctica is connected to the global climate system through long range links known as teleconnections. Warm North Atlantic Deep Water moving south from near Greenland at depths of 2000-3000 meters, is ‘balanced’ by the northward flow of cold Subantarctic Mode Water near the surface, Antarctic Intermediate Water further down, and Antarctic Bottom Water at the bottom. The North Atlantic Deep Water and the Antarctic Bottom Water are major constituents of the so-called ‘thermohaline conveyor belt’ that keeps the ocean oxygenated and regulates the Earth’s temperature. Understanding how the ‘conveyor’ works globally demands that we improve understanding of ocean processes in the Antarctic.

Investigating the links between Antarctica and the rest of the world has shown that El Niño events in the tropical Pacific bring cold, dry conditions to the Antarctic Peninsula, and warmer, temperatures and higher levels of precipitation over the coastal region of the southern Amundsen Sea off West Antarctica. The program will study how these connections work in detail. There is rapid winter season warming on the western side of the Antarctic Peninsula, where temperatures are rising faster than elsewhere in the southern hemisphere. This region has also experienced the disintegration of a number of floating ice shelves. The AGCS program will investigate the causes.

The Antarctic Climate Evolution (ACE) program is a complementary cross-disciplinary investigation of the Cenozoic and Pleistocene climate and glacial history of Antarctica. It will collect information on past climate change, and integrate it with ice sheet and climate models to identify the processes that govern Antarctic climate change, and those which feed this change back around the globe. It will also provide detailed case studies of past climate changes, against which models of future change in Antarctica can be tested. Results will improve forecasts of how Antarctic climate is likely to respond to future global change.

Antarctica has been glaciated for some 34 million years, but its ice sheets have fluctuated considerably, driving changes in global sea level and climate throughout the Cenozoic Era. Variations in ice-volume can change global sea levels by tens of meters or more, and alter the capacity of ice sheets and sea ice to act as major heat sinks or insulators. So it is important for us to determine the scale and rapidity of the response of large ice masses and associated sea ice to climatic forcing. For that reason the Intergovernmental Panel on Climate Change (IPCC) has called for an assessment of the stability of the cryosphere (the ice, snow and permafrost system) in the face of rising CO2 levels.

The ACE program will link geophysical surveys and geological studies on and around the Antarctic continent with ice-sheet and climate modeling experiments. It will determine both climate conditions and climatic changes at selected times in the past. These will include periods of unusual warmth and cold during the glaciations of the last 2 million years, and other periods in the more distant past when global temperatures were several degrees warmer than today, along with older cooling events.

The program will also examine

  1. the evolution of the Antarctic landscape, to provide climatic and environmental constraints at different times;
  2. the influence of tectonics on the behaviour of the ice sheets; and
  3. the influence of plate tectonics on the opening of gateways for ocean currents and their role in climate change.

Implementation of these programmes will require successful bids for support from national funding agencies, but assuming these are successful, SCAR will have played a major role in shaping the priorities of Antarctic research for a decade. These programmes will make significant contributions to achieving the goals of the International Polar Year in 2007-2008.
For more information contact info@scar.org.

Scientific Committee on Antarctic Research (SCAR),
Scott Polar Research Institute,
Lensfield Road, Cambridge, CB2 1ER, UK