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Scientists calculate decades of “scary” greenland ice melting

The Zachariae glacier on Greenland's east coast is visible on a photo taken by a NASA satellite Measurement of melting ice is a fairly accurate company in 201 9 thanks to satellites, weather stations and sophisticated climate models. During the 1990s and 2000s, scientists were able to make pretty good estimates, although work from previous decades was unreliable due to less advanced technology. Now, scientists have recalculated the loss of ice in Greenland since 1972, when the first Landsat satellites went into orbit to regularly photograph the Danish territory. "Looking at decades, it is best to sit back in your chair before looking at the results, because it is a little scary to see how quickly it changes," said French glaciologist Eric Rignot, of the University of California in Irvine. Rignot co-author the study, published in Proceedings of the National Academy of Sciences ( PNAS ), with colleagues in California, Grenoble, Utrecht and Copenhagen. "It is also something that affects Greenland's four corners, not just the warmer parts of the south," he said. Ice Melting Six Times Faster Glaciologists use three methods to measure ice melting First, satellites measure the height by a laser: if a glacier melts, the satellite occupies its reduced height. A second technique involves measuring variations in gravity, since ice loss can be detected by a decrease in gravity pressure. This method has been available since 2002 using NASA satellites. Satellites are used to measure ice loss in Greenland Thirdly, researchers have developed so-called mass balance…

The Zachariae glacier on Greenland’s east coast is visible on a photo taken by a NASA satellite

Measurement of melting ice is a fairly accurate company in 201

9 thanks to satellites, weather stations and sophisticated climate models.

During the 1990s and 2000s, scientists were able to make pretty good estimates, although work from previous decades was unreliable due to less advanced technology.

Now, scientists have recalculated the loss of ice in Greenland since 1972, when the first Landsat satellites went into orbit to regularly photograph the Danish territory.

“Looking at decades, it is best to sit back in your chair before looking at the results, because it is a little scary to see how quickly it changes,” said French glaciologist Eric Rignot, of the University of California in Irvine.

Rignot co-author the study, published in Proceedings of the National Academy of Sciences ( PNAS ), with colleagues in California, Grenoble, Utrecht and Copenhagen.

“It is also something that affects Greenland’s four corners, not just the warmer parts of the south,” he said.

Ice Melting Six Times Faster

Glaciologists use three methods to measure ice melting

First, satellites measure the height by a laser: if a glacier melts, the satellite occupies its reduced height. A second technique involves measuring variations in gravity, since ice loss can be detected by a decrease in gravity pressure. This method has been available since 2002 using NASA satellites.

Satellites are used to measure ice loss in Greenland

Thirdly, researchers have developed so-called mass balance models that compare the mass accumulated (rain and snow) with mass lost (ice floods) to calculate what remains.

These models, confirmed by field measurements, have become very reliable since the 21st century, according to Rignot, with a five to seven percent margin of error compared to 100 percent a few decades ago.

The research group used these models to “go back in time” and reconstruct Greenland’s ice levels in the 1970s and 1980s.

The limited data available for these satellite-quality satellite media, aerial photos, ice cores and other observations helped to refine them.

“We added a little bit of history that didn’t exist,” says Rignot.

Result: In the 1970s, Greenland accumulated an average of 47 gigatonnes of ice per year. Then it lost an equivalent volume in the 1980s.

The melting continued at this rate during the 1990s, before a sharp acceleration during the 2000s (187 Gt / year) and even more since 2010 (286 Gt / year) 19659004] Ice melts six times faster than the 1980s, researchers appreciate – and Greenland’s glaciers alone have contributed to a 13.7 millimeter increase in sea levels since 1972, they believe.

“This is an excellent job at a well-established research group with new methods for extracting more information from available data,” says Colin Summerhayes, of the Scott Polar Research Institute in Cambridge.

As with a similar study conducted by the same team in Antarctica, the new study has provided a long-term view of the rapid ice melting observed in Greenland in recent years.

“With these new data we can present the latest dramatic changes of Greenland’s contribution to the global sea level in a long-term context – The loss of ice we’ve seen in the past eight years is as much as disappearing in the previous four decades, says Amber Leeson, a lecturer in Environmental Data Science at Lancaster University.


Melt glaciers that cause sea levels rise to ever higher prices


More information:
Jérémie Mouginot and others, “Twenty-five years of mass balance in Greenland from 1972 to 2018,” PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1904242116

© 2019 AFP

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Scientists calculate decades of “scary” Greenland ice melting (2019, April 22)
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