Greenland's Thinning Ice
 
With temperatures around the world climbing, melt waters from the
continental ice sheets of Greenland and Antarctica are raising sea levels.
Those ice sheets are melting from both above and below. Much of the ice
lost from ice sheets comes from a process called calving where ice erodes,
breaks off, and flows rapidly into the ocean. A large volume of ice is also
lost from ice sheets melting on their surfaces.
 
https://www.youtube.com/watch?v=Rl7mPdZCRKg
 
To determine to what extent Greenland's glaciers are being melted from
underneath, NASA recently began a 5-year airborne and ship-based mission
called Oceans Melting Greenland (OMG).
 
Previous research has shown that Greenland's glaciers, which flow like
rivers of ice into the ocean, sit on the ground deeper below sea level than
had been thought. Warm ocean currents sweep across and erode the hidden
glacier faces. As a result, they're melting faster - a few feet a day in
summer - than anyone suspected.
 
Oceanographer Josh Willis is the Principal Investigator for the OMG
mission. He says, "We're investigating how the ice interacts with the
ocean, and how much the oceans are melting away the glaciers from the edges
of the ice sheet."
 
For this study, a NASA aircraft is flying the Glacier and Ice Surface
Topography Interferometer (GLISTIN) instrument around Greenland for a few
weeks each year.
 
Willis says, "GLISTIN is making very high resolution maps of the ice,
showing us how fast the glaciers are thinning and retreating right at the
edge."
 
The aircraft will also continue dropping more than 200 ocean probes each
year through 2020 to measure how temperature and salinity change between
the ocean surface and the sea floor - from the cold meltwater at the
surface down to the warmer, heavier saltwater below. This will help
determine how changes in the ocean affect the ice.
 
In addition, OMG has completed surveys using a ship equipped with sonar to
measure the seafloor shape and depth, which affect where and how much the
warm water from the Atlantic eats away at the coastal glaciers. The mission
also conducted airborne measurements of gravity off the coast of Greenland,
giving the team more information about the depth of water in those
locations.
 
While OMG is looking at the effects on ice sheets from below, NASA's
Operation IceBridge mission is surveying polar ice from above. The overlap
of OMG and IceBridge is providing the most accurate measurements to date of
changes in Greenland's ice sheet mass.
 
Glaciologist Ala Khazendar, a member of the OMG science team says,
"IceBridge's highly-accurate Airborne Topographic Mapper is the gold
standard of measuring the surface elevation changes of the ice sheet. With
OMG uncovering how much ice is being lost at the periphery of the ice
sheet, and IceBridge telling us how the thickness of the glaciers is
changing further upstream, we can better attribute Greenland's ice loss
either to changes in the ocean or warming of the atmosphere, which directly
melts the ice from above."
 
"Greenland contains enough ice to raise global sea levels by 20 feet
(6 meters) if it all melted," notes Willis. "Right now we think
this will take at least several hundred years, but data from OMG are
helping scientists better understand how much the oceans are melting
Greenland's ice. From now through 2020, OMG will be making annual visits to
measure the oceans and ice together, helping scientists study changes to
Greenland's ice sheet and how those changes may impact Earth's environment.
 
For more science news about our ever-changing home planet, stay tuned to
science.nasa.gov.
 
 
Regards,
 
Roger

--- PQUSA