"Science Stunner: Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s, Antartica’s Ice Loss Up 50% In Past Decade"
Based on the new study in Science, this chart shows changes in global sea level due to ice sheet melting since 1992. The background image shows thickening (blue) and thinning (red) of Antarctica’s ice sheets over the same period. Credit: ESA/NASA/Planetary Visions via NBC.
A major new international study reconciles “an ensemble of satellite altimetry, interferometry, and gravimetry data sets” to determine polar ice-sheet ice loss with the highest accuracy to date. The study, “A Reconciled Estimate of Ice-Sheet Mass Balance” (subs. req’d) was published in the journal Science Thursday.
The NASA Jet Propulsion Laboratory news release explains the study’s significance:
An international team of experts supported by NASA and the European Space Agency (ESA) has combined data from multiple satellites and aircraft to produce the most comprehensive and accurate assessment to date of ice sheet losses in Greenland and Antarctica and their contributions to sea level rise.
In a landmark study published Thursday in the journal Science, 47 researchers from 26 laboratories report the combined rate of melting for the ice sheets covering Greenland and Antarctica has increased during the last 20 years. Together, these ice sheets are losing more than three times as much ice each year (equivalent to sea level rise of 0.04 inches or 0.95 millimeters) as they were in the 1990s (equivalent to 0.01 inches or 0.27 millimeters). About two-thirds of the loss is coming from Greenland, with the rest from Antarctica….
“Both ice sheets appear to be losing more ice now than 20 years ago, but the pace of ice loss from Greenland is extraordinary, with nearly a five-fold increase since the mid-1990s,” [JPL's Erik] Ivins said. “In contrast, the overall loss of ice in Antarctica has remained fairly constant, with the data suggesting a 50-percent increase in Antarctic ice loss during the last decade.”
The NBC Evening News had a very good story on this study and the general acceleration of ice sheet melt:
The JPL release is accompanied by this remarkable photo:
Turbulent Water Overflow: Over the course of several years, turbulent water overflow from a large melt lake carved this 60-foot-deep (18.3 meter-deep) canyon (note people near left edge for scale). Image credit: Ian Joughin, University of Washington
The international collaboration that made this study possible was truly unique:
The study was produced by an international collaboration — the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) — that combined observations from 10 satellite missions to develop the first consistent measurement of polar ice sheet changes. The researchers reconciled differences among dozens of earlier ice sheet studies by carefully matching observation periods and survey areas. They also combined measurements collected by different types of satellite sensors, such as ESA’s radar missions; NASA’s Ice, Cloud and land Elevation Satellite (ICESat); and the NASA/German Aerospace Center’s Gravity Recovery and Climate Experiment (GRACE).
“What is unique about this effort is that it brought together the key scientists and all of the different methods to estimate ice loss,” said Tom Wagner, NASA’s cryosphere program manager in Washington. “It’s a major challenge they undertook, involving cutting-edge, difficult research to produce the most rigorous and detailed estimates of ice loss from Greenland and Antarctica to date. The results of this study will be invaluable in informing the IPCC as it completes the writing of its Fifth Assessment Report over the next year.”
Finally, here is a graphic on the astonishing surface ice melt in Greenland this summer:
Extent of surface melt over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. Via NASA/JPL.
We can’t dawdle much longer if we want to avoid an ice-free planet….