The measurement of melting ice in 201
In the 1990s and 2000s, scientists were able to make pretty good estimates, although the work of previous decades was unreliable due to less advanced technologies.
Now the researchers have recalculated the amount of ice lost in Greenland since 1972. This year, the first Landsat satellites landed in orbit to regularly photograph the Danish territory.
"If you look at it for several decades, you should first sit back and look at the results, because it's a bit scary how fast you see it changes," said French glaciologist Eric Rignot of the University of California in Irvine.
Rignot was co-author of the study, which was 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 of the South," he said.
Ice melt six times faster
Glaciologists use three methods to measure ice melting
First, satellites measure altitude with a laser: when a glacier melts, the satellite assumes its reduced altitude ,
A second technique involves measuring gravity swings since ice loss can be detected by a reduction in gravity. This method has been available since 2002 with NASA satellites.
Third, scientists have developed so-called mass balance models that compare the accumulated masses (rain and snow) with the lost masses (ice flow discharges) to calculate the remaining values.
These field-confirmed models have it. According to Rignot, they have been very reliable since the 2000s – with an error rate of five to seven percent compared to 100 percent a few decades ago.
The research team used these models to "go back in time" and reconstruct the Greenland ice in the 1970s and 1980s.
The limited data available for that period – medium-quality satellite photos, aerial photographs, ice cores and other observations – helped to refine them.
"We added some history that did not exist," Rignot said.
The results: In the 1970s, Greenland collected an average of 47 gigatons of ice per year. In the eighties it lost an equal volume.
Meltdown continued at this rate in the 1990s before increasing even further in the 2000s (187 Gt / year) and since 2010 (286 Gt / yr). 19659004] The ice melts six times faster than in the 1980s, researchers estimate – and the Greenland glaciers alone have contributed since 1972 to a rise in sea level by 13.7 millimeters, they believe.
"This is an excellent work by a well" An established research group that uses novel methods to extract more information from available data, "said Colin Summerhayes of the Scott Polar Research Institute at Cambridge.
Like a similar one Study carried out by the same team in Antarctica, the new study provides a longer term view of the rapid melting of ice that has been observed in Greenland in recent years.
"These new data allow us to understand the recent dramatic changes in the contribution "The ice loss we've seen The past eight years have been as much as lost in the past four decades," said Lancaster University environmental science lecturer Amber Leeson ,
Melting glaciers are causing sea level rise
Jérémie Mouginot el al. "Forty-six Years of Greenlandic Mass Balance Between 1972 and 2018", 19459014, PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1904242116
© 2019 AFP
Researchers calculate decades of "scary" Greenland ice melting (2019, April 22)
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