New satellite data details rate of melting
FRISCO — Yet another major study — the third within a week — confirms that the Antarctic ice sheets are going to big factors in the rise in sea level during the next few decades.
Led by scientists from the University of Leeds, the study shows that Antarctica is losing about 159 billion tons of ice each year — twice as much as during the last detailed survey. The latest assessment relied on detailed measurements of ice sheet elevation change from data collected by the European Space Agency’s CryoSat-2 satellite mission, which carries an altimeter specially designed for this task.
A team of scientists from the UK Centre for Polar Observation and Modelling, led by researchers at the University of Leeds, have produced the first complete assessment of Antarctic ice sheet elevation change. The satellite surveys almost the entire Antarctic continent, to within 215 kilometers of the South Pole and five times as much sampling along coastal regions where ice losses are concentrated.
“Although we are fortunate to now have, in CryoSat-2, a routine capability to monitor the polar ice sheets, the increased thinning we have detected in West Antarctica is a worrying development,” said study leader Professor Andrew Shepherd, with the University of Leeds. “It adds concrete evidence that dramatic changes are underway in this part of our planet, which has enough ice to raise global sea levels by more than a metre. The challenge is to use this evidence to test and improve the predictive skill of climate models,” Shepherd said.
Glacier thinning was most pronounced in the Amundsen Sea sector of West Antarctica, where several other recent studies warned that the large reaches of the West Antarctic Ice Sheet are inexorably disintegrating.
On average West Antarctica lost 134 gigatonnes of ice, East Antarctica three gigatonnes, and the Antarctic Peninsula 23 gigatonnes in each year between 2010 and 2013 – a total loss of 159 gigatonnes each year.
The polar ice sheets are a major contributor to global sea level rise and, when combined, the Antarctic losses detected by CryoSat-2 are enough to raise global sea levels by 0.45 millimetres each year alone.
The detailed data from above West Antarctica reinforces similar conclusions from other survey approaches, including ground-based measurements. The data also shows that the average rate of ice thinning in West Antarctica has also increased, and this sector is now losing almost one third (31 percent) as much ice each year than it did during the five year period (2005-2010) prior to CryoSat-2′s launch.
“We find that ice losses continue to be most pronounced along the fast-flowing ice streams of the Amundsen Sea sector, with thinning rates of between 4 and 8 metres per year near to the grounding lines of the Pine Island, Thwaites and Smith Glaciers,” said l.ead author Dr Malcolm McMillan from the University of Leeds.
This sector of Antarctica has long been identified as the most vulnerable to changes in climate and, according to recent assessments, its glaciers may have passed a point of irreversible retreat.
“Thanks to its novel instrument design and to its near-polar orbit, CryoSat allows us to survey coastal and high-latitude regions of Antarctica that were beyond the capability of past altimeter missions, and it seems that these regions are crucial for determining the overall imbalance,” Shepherd said.
“Although we are fortunate to now have, in CryoSat-2, a routine capability to monitor the polar ice sheets, the increased thinning we have detected in West Antarctica is a worrying development. It adds concrete evidence that dramatic changes are underway in this part of our planet, which has enough ice to raise global sea levels by more than a metre. The challenge is to use this evidence to test and improve the predictive skill of climate models.”
“The increasing contribution of Antarctica to sea-level rise is a global issue, and we need to use every technique available to understand where and how much ice is being lost,” said Professor David Vaughan of the British Antarctic Survey. “Through some very clever technical improvements, McMillan and his colleagues have produced the best maps of Antarctic ice-loss we have ever had. Prediction of the rate of future global sea-level rise must be begin with a thorough understanding of current changes in the ice sheets – this study puts us exactly where we need to be.”
“This study does a nice job of revealing the strong thinning along the Amundsen Coast, which is consistent with theory and models indicating this region is in the early stages of collapse,” said Dr Ian Joughin at the University of Washington, author of a recent study simulating future Antarctic ice sheet losses.