Monday, September 06, 2010

Greenland not melting quite as fast as previously thought. Wait for the media silence

A year ago we were inundated by fears that the ice-sheet in Greenland was melting.
The Greenland ice sheet is losing its mass faster than in previous years and making an increasing contribution to sea level rise, a study has confirmed.

In breathless panic Roger Black the BBC's environment correspondent flagged up the scary results of this.
The team used weather data, satellite readings and models of ice sheet behaviour to analyse the annual loss of 273 thousand million tonnes of ice.

Melting of the entire sheet would raise sea levels globally by about 7m (20ft).

Problem is of course that they got their sums wrong.

Today the University of Delft have released a study which pours cold water on the panic. Using the same GRACE satellite system to provide the data they new study states,
Based on this principle, previous estimates for the Greenland ice cap calculated that the ice was melting at a rate of 230 gigatonnes a year (i.e. 230,000 billion kg). That would result in an average rise in global sea levels of around 0.75 mm a year. For West Antarctica, the estimate was 132 gigatonnes a year. However, it now turns out that these results were not properly corrected for glacial isostatic adjustment, the phenomenon that the Earth’s crust rebounds as a result of the melting of the massive ice caps from the last major Ice Age around 20,000 years ago. These movements of the Earth’s crust have to be incorporated in the calculations, since these vertical movements change the Earth’s mass distribution and therefore also have an influence on the gravitational field.

Or errr... guys your figures are wrong.
Researchers from the Jet Propulsion Laboratory in Pasadena (US), TU Delft and SRON Netherlands Institute for Space Research have now succeeded in carrying out that correction far more accurately. They did so using combined data from the GRACE mission, GPS measurements on land and sea floor pressure measurements. These reveal that the sea floor under Greenland is falling more rapidly than was first thought. One of the researchers, Dr Bert Vermeersen of TU Delft, explains: 'The corrections for deformations of the Earth’s crust have a considerable effect on the amount of ice that is estimated to be melting each year. We have concluded that the Greenland and West Antarctica ice caps are melting at approximately half the speed originally predicted.' The average rise in sea levels as a result of the melting ice caps is also lower.

Of course we can expect this reassement to get the same amount of coverage as the previous panic.

No comments: