Polar Ice Sheets Becoming Main Contributors to Sea Level Rise, Say Scientists
14.03.2011 - Water & Oceans, Ice & Snow, Bi-polar
A study published this month in the Geophysical Research Letters shows that the Greenland and Antarctic Ice Sheets are losing mass at an accelerating pace. This study of changes in ice sheet mass balance suggests that the ice sheets are currently becoming the main contributor to global sea level rise – well in advance of predictions the Intergovernmental Panel on Climate Change outlined in 2007. Until recently, thermal expansion had been the main contributor to sea level rise.
The team compared two independent measurement techniques to examine changes in ice sheet mass balance and the acceleration of ice loss. The first method compared the difference between interferometric synthetic aperture radar data from satellites and radio echo soundings on the one hand and regional climate model data from Utrecht University on the other. The second method used eight years of data collected by the NASA/German Aerospace Center's Gravity Recovery and Climate Experiment (GRACE) satellites, which track minute changes in Earth's gravity field due to changes in the Earth's mass distribution, which includes ice movement.
Reconciling the differences between the different techniques, the team found them to agree on the total amount and rate of mass loss in their eight years of data overlap. The researchers also observed that each year within the same time span, the Greenland Ice Sheet lost mass faster than it had the year before – an average of 21.9 gigatonnes a year. In Antarctica, the year-over-year speedup in ice mass lost averaged 14.5 gigatonnes, which led the team to conclude that if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea levels by 15 centimetres by 2050.
