The Greenland and West Antarctic ice caps are melting at half the speed previously predicted, shows a team from the Jet Propulsion Laboratory, Delft University of Technology (TU Delft, The Netherlands) and SRON Netherlands Institute for Space Research in Nature Geoscience.
The melting of the ice caps has been charted since 2002 using the measurements produced by the two GRACE satellites. From space they detect small changes in the Earth's gravitational field and these changes are related to the exact distribution of mass on Earth, including ice and water. When ice melts and lands in the sea, this therefore has an effect on the gravitational field.
Based on this principle, previous estimates for the Greenland ice cap calculated that the ice was melting at a rate of 230 giga-tons per year (i.e. 230,000 billion kg), which would result in an average rise in global sea levels of around 0.75 mm a year. For West Antarctica, the estimate was 132 giga-tons per 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.
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.
"The innovative aspect of our method is that we simultaneously matched the current changes in the ice mass and glacial isostatic adjustment to the observations, instead of assuming that a particular glacial isostatic adjustment model is correct," says Dr Vermeersen. "For Greenland in particular, we have found a glacial isostatic adjustment model that deviates rather sharply from general assumptions. But at present there are too few data available to verify this independently. A more extensive network of GPS readings in combination with geological indicators for the local and regional changes in sea level changes around Greenland over the last 10,000 years, will possibly be able to provide conclusive evidence on this matter in the years to come."
Xiaoping Wu, Michael B. Heflin, Hugo Schotman, Bert L. A. Vermeersen, Danan Dong, Richard S. Gross, Erik R. Ivins, Angelyn W. Moore&Susan E. Owen, 'Simultaneous estimation of global present-day water transport and glacial isostatic adjustment', Nature Geoscience 3, 642 - 646 (2010) Published online: 15 August 2010 | doi:10.1038/ngeo938
David H. Bromwich, Julien P. Nicolas, 'Sea-level rise: Ice-sheet uncertainty', Nature Geoscience 3, 596 - 597 (2010) Published online: 15 August 2010 | doi:10.1038/ngeo946
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Sexual Fantasies: Threesomes Are Normal, Golden Showers Not So Much
- The Vampire Deer Of Afghanistan
- Resveratrol Reverses Benefits Of Exercise - Study
- Okay With Disgusting Images? You Vote This Way 95 Percent Of The Time
- Aging Brains Aren't Necessarily Declining Brains
- Cui Bono? B-corporations And The University
- Information-Theoretic Security: Creating 21st Century Cryptography Standards
- "It's vital to understand that while crapping where you eat is not linked to having conservative..."
- "16 people who were originally doing less than 30 minutes exercise a day then did how much low volume..."
- "Trouble is without citations this article reads like a slew of anecdotes. It begins promisingly..."
- "Do you work for Hank? Or do you just parrot his line of bullshit, and try to legitimize it with..."
- Two-faced anti-GMO groups: Block crop and food innovations then claim Big Ag prevents GMO innovations
- Why support erodes for GMO labeling (Hint: It’s not because of spending by Big Ag)
- Genetic “hall of mirrors” with large palindromes, yet smaller: What’s mighty about the mouse
- Gut bacteria an easy scapegoat for disease, but connections hard to prove
- Vermont Rube Goldberg-like GMO labeling law exempts GMO filled natural supplements
- Downside to GMOs: Yields have become so good, they exceed processing capacity
- More penalties on the way for hospitals that treat the poor? New U-M study suggests so
- Cancer cell fingerprints in the blood may speed up childhood cancer diagnosis
- Study of Chile earthquake finds new rock structure that affects earthquake rupture
- Tracking a gigantic sunspot across the Sun
- Massive geographic change may have triggered explosion of animal life