The climate in Antarctica has impact worldwide
The vast ice-bound expanses of Antarctica serve as a global thermostat, regulating the world’s climate system. The white ice cover cools the atmosphere through the albedo effect, whereas the dark sea surface absorbs heat from the sun and plays a crucial role in the ocean’s heat budget. Cold surface water with high salinity plunges to the depths, driving the ocean currents that transport heat from one part of the earth to another. The Southern Ocean takes up carbon dioxide from the atmosphere, thus playing an important part in the carbon cycle.
Exchange of water between the Southern Ocean and the global bottom water circulation is a crucial piece in the climate puzzle. Altered water exchange affects global climate; such alterations can be brought about by changes in wind patterns around Antarctica and influenced by the Antarctic ice sheet.
The Southern Ocean is a major factor in the global carbon cycle because it links the physical climate system and the marine ecosystem. Atmospheric CO2 is taken up by the ocean, and over 40% of the total annual uptake of CO2 occurs here. However, model simulations and observations indicate changes over the past 50 years, and imply that total CO2 uptake has decreased in the past couple decades.
The Southern Ocean’s ability to take up CO2 can change as a result of warming in the ocean (warm water takes up less CO2), and as a consequence of altered circulation and interactions in the ocean–atmosphere–ice system. What role the Southern Ocean will play in the carbon cycle remains unclear, as does the effect of possible changes.
Water released when ice melts in Antarctica is absolutely central to assessments of the possible future rise in sea level. Glaciers – particularly those of the Antarctic Peninsula in West Antarctica – appear to be shrinking. Studies have revealed a strong correlation between temperatures in Antarctica and global sea level, which in turn correlates with global temperature over the past 520 000 years. Antarctica is expected to contribute to the rise in sea level projected over the next century. Loss of ice along the coast of Antarctica (calving and melting) is expected to exceed the increase in the mass of the inland ice sheet caused by greater precipitation; thus the overall effect is that Antarctica will continue to contribute to sea level rise. Collapse of those parts of the Antarctic ice cap that are in contact with the ocean – or where the bedrock is below sea level – would raise sea level considerably more than predicted, and in a very short time. Present knowledge shows, nonetheless, that such an event would raise sea level only a few decimetres during this century.
- A.J. Turner et al. 2009. Antarctic climate change and the environment. Antarctic Science. DOI:10.1017/S0954102009990642.
- Intergovernmental Panel on Climate Change (IPCC) 2013. Fifth assessment report contribution.
- Eelco .J. Rohling et al. 2009. Antarctic temperature and global sea level closely coupled over the past five glacial cycles. Nature Geoscience 2, 500 - 504. DOI:10.1038/ngeo557