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Measuring melting ice is a fairly precise business in 2019—thanks to satellites, weather stations and sophisticated climate models.
By the 1990s and 2000s, scientists were able to make pretty good estimates, although work from previous decades was unreliable due to less advanced technology.
Researchers - Amount - Ice - Greenland - Year
Now, researchers have recalculated the amount of ice lost in Greenland since 1972, the year the first Landsat satellites entered orbit to regularly photograph the Danish territory.
"When you look at several decades, it is best to sit back in your chair before looking at the results, because it is a bit scary to see how fast it is changing," said French glaciologist Eric Rignot, of the University of California at Irvine.
Rignot - Study - Proceedings - National - Academy
Rignot co-authored the study, published in the Proceedings of the National Academy of Sciences (PNAS),with colleagues in California, Grenoble, Utrecht and Copenhagen.
"It's also something that affects the four corners of Greenland, not just the warmer parts in the south," he said.
Glaciologists - Methods - Ice - Melting
Glaciologists use three methods to measure ice melting.
Firstly, satellites measure altitude with a laser: if a glacier melts, the satellite picks up its reduced height.
Technique - Variations - Gravity - Loss - Decrease
A second technique involves measuring variations in gravity, as ice loss can be detected through a decrease in gravitational pull. This method has been available since 2002 using NASA satellites.
Thirdly, scientists have developed so-called mass balance models, which compare mass accumulated (rain and snow) with mass lost (ice river discharges) to calculate what is left.
Models - Field - Measurements - Percent - Margin
These models, confirmed with field measurements, have become very reliable since the 2000s, according to Rignot—boasting a five to seven percent margin of error, compared to 100...
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