The Washington Post asks Ian Joughin about a recent study, in the journal Science Advances, using a GPS network which
measures ice sheet mass loss in Greenland and re-evaluates previous studies.
Not exact matches
But gravity -
measuring satellites have shown that the continent's
ice sheets have been losing
mass since at least 2002.
When the Gravity Recovery and Climate Experiment (GRACE) satellites began
measuring gravity signals around the world in 2002, scientists knew they would have to separate
mass flow beneath the earth's crust from changes in the
mass of the overlying
ice sheet.
The second is the gravity method, which utilizes NASA's GRACE satellite pair to essentially weigh the
ice sheets from space (it
measures minute changes in their flight path due to the shifting gravity field of
mass below).
GNET, short for «Greenland GPS Network,» uses Earth's natural elasticity to
measure the
mass of the
ice sheet.
To infer the
ice sheet's
mass, the team
measured ice flowing out of Antarctica's drainage basins over 85 percent of its coastline.
The satellites
measure changes in gravity to determine
mass variations of the entire Antarctic
ice sheet.
Because
ice sheets contain so much
ice and have the potential to raise or lower global sea level so dramatically,
measuring the
mass balance of the
ice sheets and tracking any
mass balance changes and their causes is very important for forecasting sea level rise.
The only comprehensive study of the Antarctic
Ice Sheet mass was a 10 + year study based on continuous 24/365 satellite measurements over the period 1993 to 2003, covering 80 % of the AIS with estimates from other methods for the remaining 20 %, which can not be
measured by satellites (coastal areas and polar regions).
Although the satellites are considered the gold - standard for
measuring and observing sea levels, hurricanes / typhoons, ozone holes, sea
ice, atmospheric CO2 distribution, polar
ice sheet masses and etc., the same 24/7 technology used to
measure temperatures across the entire habitable world is now being ignored (i.e., denied) due to the above inconvenient evidence.
Over the past quarter - century, both the extent of melting and the length of the melt season on the Greenland
ice sheet have been growing, as local temperatures have risen.6 Satellites
measure the extent of melting by differentiating between areas of the
ice mass that are fully frozen and those with surface meltwater.
Second, and less important but still rather spectacular, was the melting of virtually every square inch of the surface of this
ice sheet over a short period of a few days during the hottest part of the summer, a phenomenon observed every few hundred years but nevertheless an ominous event considering that it happened just as the aforementioned record
ice mass loss was being observed and
measured.
As explained in the press release, the scientists began with the
measure of sea level rise between 2005 and 2013, then deducted the amount of rise due to meltwater (e.g., melting
ice sheets and loss of glacier
mass worldwide) and then the amount of rise due to the expansion of water from the warming in the upper portion of the world's oceans (which scientists have good data on).
Those instruments
measure gravity anomalies (and hence
mass) and so are will be great at
measuring the loss of
ice from the
ice sheets etc..
PRESS RELEASE Date Released: Tuesday, December 20, 2005 Source: Goddard Space Flight Center In the first direct, comprehensive
mass survey of the entire Greenland
ice sheet, scientists using data from the NASA / German Aerospace Center Gravity Recovery and Climate Experiment (Grace) have
measured a significant decrease in the
mass of the Greenland
ice cap.
Hager, B. H. Weighing the
ice sheets using space geodesy: A way to
measure changes in
ice sheet mass.