In short, as ocean warming melts the ice sheet at the continental and ice shelf margins, melting increases in these areas, and steepens the gradients of glaciers or ice flows, such as the Ferrigno Ice Stream, which feed in from the upland parts of the continents.
The presence of the rift valley facilitates this flow and thus rapidly depletes the central ice cover.
As Dr. Bingham points out, neither the knowledge that ice is melting more rapidly at warmer sea margins, nor the existence of significant topographical features on the continent, is news in the scientific community.
What’s significant about the new research is that it establishes a connection between the two.
‘Essentially,’ he says, ‘we’ve found that while one sees evidence for ice loss around much of the Antarctic margin, the losses are especially pronounced, and steered further inland, where ancient rifting has dissected the landscape beneath the ice.’
Why is Antarctica Important?
The new research will add considerably to the understanding of how the Antarctic ice sheet impacts upon global sea levels. At its very simplest, the equation is this: when the global average temperature is low, more of the earth’s water is locked away in the form of ice (the cryosphere) and sea level is relatively low. In warmer periods, the ice melts, the cryosphere is smaller and more water is released into the oceans: as a result, sea level is higher.
In addition to this, the existence of major ice sheets itself produces a controlling mechanism over global temperatures, through its actual temperature and through the amount of the sun’s heat which is reflected back into space by the surface of the ice. ‘The fact that there is an ice-covered continent overlying one of the poles on the Earth is one of the most significant, if not the most significant, reasons we have the climate we live in today,’ says Dr. Bingham.
Sea Level Rising?
Ice coverage and sea levels fluctuate over cycles of millions of years, so the increased wasting rates of the Antarctic ice sheet aren’t going to lead to significant sea level rise any time soon. What’s most likely is a limited increase in sea level over the next century, with potential impacts for low-lying areas already at risk from flooding – in the light of which any research which helps to increase understanding of the processes affecting ice sheet wasting is only to be welcomed.
Bingham, R. G., Ferraccioli, F., King, E. C., Larter, R. D., Pritchard, H. D., Smith, A. M. and Vaughan, D. G. Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts. (2012). Nature. Accessed July 25, 2012.
Wilson, R. C. L., Drury, S. A. and Chapman J. L. The Great Ice Age. (2001). Routledge.