Tech

May 17, 2013

NASA satellite data help pinpoint glaciersí role in sea level rise

The Aletsch Glacier in Switzerland is the largest valley glacier in the Alps and it has been losing mass since the mid-19th century. A new study using data from two NASA satellites found that glaciers like this one lost an average of 571 trillion pounds of ice per year from 2003 to 2009, which contributed to about 30 percent of the total observed global sea level rise during the same period.

A new study of glaciers worldwide using observations from two NASA satellites has helped resolve differences in estimates of how fast glaciers are disappearing and contributing to sea level rise.

The new research found glaciers outside of the Greenland and Antarctic ice sheets, repositories of 1 percent of all land ice, lost an average of 571 trillion pounds (259 trillion kilograms) of mass every year during the six-year study period, making the oceans rise 0.03 inches (0.7 mm) per year. This is equal to about 30 percent of the total observed global sea level rise during the same period and matches the combined contribution to sea level from the Greenland and Antarctica ice sheets.

The study compares traditional ground measurements to satellite data from NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) and Gravity Recovery and Climate Experiment (GRACE) missions to estimate ice loss for glaciers in all regions of the planet. The study period spans 2003 to 2009, the years when the two missions overlapped.

“For the first time, we have been able to very precisely constrain how much these glaciers as a whole are contributing to sea level rise,” said Alex Gardner, Earth scientist at Clark University in Worcester, Mass., and lead author of the study. “These smaller ice bodies are currently losing about as much mass as the ice sheets.”

The study was published May 16 in the journal Science.

ICESat, which stopped operating in 2009, measured glacier change through laser altimetry, which bounces lasers pulses off the ice surface to inform the satellite of changes in the height of the ice cover. ICESat’s successor, ICESat-2, is scheduled to launch in 2016. GRACE, still operational, detects variations in Earth’s gravity field resulting from changes in the planet’s mass distribution, including ice displacements.

The new research found all glacial regions lost mass from 2003 to 2009, with the biggest ice losses occurring in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. In contrast, Antarctica’s peripheral glaciers – small ice bodies not connected to the main ice sheet – contributed little to sea level rise during that period. The study builds on a 2012 study using only GRACE data that also found glacier ice loss was less than estimates derived from ground-based measurements.

Current estimates predict all the glaciers in the world contain enough water to raise sea level by as much as 24 inches (about 60 centimeters). In comparison, the entire Greenland ice sheet has the potential to contribute about 20 feet (about 6 meters) to sea level rise and the Antarctic ice sheet just less than 200 feet (about 60 meters).

“Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend to not worry about it,” said study co-author Tad Pfeffer, a glaciologist at the University of Colorado in Boulder. “But it’s like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there’s ice in those glaciers, it’s a major contributor to sea level rise.”

To make ground-based estimates of glacier mass changes, glaciologists perform on-site measurements along a line from a glacier’s summit to its edge. Scientists extrapolate these measurements to the entire glacier area and carry them out for several years to estimate the glacier’s overall mass change over time. While this type of measurement does well for small, individual glaciers, it tends to overestimate ice loss when the findings are extrapolated to larger regions, such as entire mountain ranges.

“Ground observations often can only be collected for the more accessible glaciers, where it turns out thinning is occurring more rapidly than the regional averages,” Gardner said. “That means when those measurements are used to estimate the mass change of the entire region, you end up with regional losses that are too great.”

GRACE does not have fine enough resolution and ICESat does not have sufficient sampling density to study small glaciers, but the two satellites’ estimates of mass change for large glaciered regions agree well, the study concluded.

“We now have a lot more data for the glacier-covered regions because of GRACE and ICESat,” said Gardner. “Without having these independent observations, there was no way to tell that the ground observations were biased.”

The research involved 16 researchers from 10 countries, with major contributions from Clark University, the University of Michigan, Scripps Institution of Oceanography in San Diego, Trent University in Ontario, the University of Colorado at Boulder and the University of Alaska Fairbanks.




All of this week's top headlines to your email every Friday.


 
 

 
University of Rhode Island photograph by Tom Glennon

NASA kicks off field campaign to probe ocean ecology, carbon cycle

University of Rhode Island photograph by Tom Glennon The Research Vessel Endeavor is the floating laboratory that scientists will use for the ocean-going portion of the SABOR field campaign this summer. NASA embarks this week o...
 
 
NASA photograph by Carla Thomas

NASA’s high-flying laser altimeter to check out summer sea ice, more

NASA photograph by Carla Thomas This summer, the Multiple Altimeter Beam Experimental Lidar, or MABEL, will fly above Alaska and the Arctic Ocean on one of NASA’s ER-2 high-altitude aircraft. Sea ice in summer looks dramatica...
 
 
SOFIA

Outer space to inner space: SOFIA inside Lufthansa Technik hangar

NASA photograph by Jeff Doughty NASA’s Stratospheric Observatory for Infrared Astronomy is shown inside the Lufthansa Technik hangar in Hamburg, Germany where it is beginning its decadal inspection. Flight, aircraft maint...
 

 
NASA photograph by Tony Landis

New life for an old bird: NASA’s F-15B test bed gets new engines

NASA photograph NASA’s F-15B flight research test bed carries shuttle thermal insulation panels on its underbelly during a research flight in 2005. NASA Armstrong’s F-15B aeronautics research test bed, a workhorse at th...
 
 
NASA photograph by Tom Tschida

Towed glider benefits from center’s new 3-D printer capability

NASA photograph by Tom Tschida The major components of NASA Armstrong’s new high-resolution 3-D additive manufacturing printer occupy a shelf in the center’s subscale aircraft research lab. Robert “Red” ...
 
 
NASA photograph by Emmett Given

NASA completes testing on 3-D printer

NASA photograph by Emmett Given United Space Alliance engineer Cynthia Azzarita, left, and Boeing Company engineer Chen Deng, members of the Human Factors Integration Team at NASA’s Johnson Space Center, conduct a “...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>