NASA satellites bearing advanced laser technology have recorded the most accurate picture of large-scale ice sheet melting in Greenland and Antarctica to date.
Melting ice sheets in Greenland and Antarctica contributed to 14 millimetres of sea level rise between 2003 and 2019, according to a study published today in the journal Science.
“Into the future with that 14 millimetres happening every 16 years, it adds up to a pretty significant amount of sea level rise”, lead author Dr Benjamin Smith an associate professor at the University of Washington told ABC News.
If all the melt observed in this study was to flood an area the size of Australia, we would all be wading through 66 centimetres of water, Professor Smith calculated.
Two satellites, the ICESat-1 and the more advanced ICESat-2, were equipped with “laser altimeters” that bounced light pulses off the ice sheets to determine their height.
Researchers compared measurements taken in the early 2000s by ICESat-1 with measurements taken in 2018 and 2019 by ICESat-2.
“The two sets of measurements intersect each other at millions of points, it’s those intersections that let us map how the ice changed between ICESat-1 and ICESat-2,” Professor Smith said.
“This is a much more significant climatic signal than what you might see if you just surveyed for two or three years,” Professor Smith said.
ABC News reports previous satellite data from NASA shows the rate of global mean sea level rise is accelerating by an average of 3.4mm a year.
Melting ice from Greenland and Antarctica contributes to about a third of the sea level rise we’re seeing, Professor Smith said.
The latest data showed melting was more extreme in Greenland than in Antarctica.
Greenland’s ice sheet lost an average of 200 gigatonnes of ice a year, contributing up to two thirds of the sea level rise.
The majority of this ice loss was from thinning of coastal glaciers, which have been impacted by warmer summer temperatures melting the ice on the surface, and warmer ocean temperatures eroding the edges of the ice.
“Greenland melts at the surface quite a bit every year whereas the surface of Antarctica does not melt over a significantly large areas of the continent,” he told ABC News.
The satellite data showed Antarctica lost an average of 118 gigatonnes of ice in the same time frame.
While there are gains in ice coverage in the interior, due to increased snowfall, these did not outweigh the losses in coastal areas.
“The total amount of thinning vastly outweighs the small amount of thickening in the interior of the ice sheets,” Professor Smith said.
The majority of Antarctica’s contribution to sea level rise comes from its glaciers flowing into the ocean as warmer water erodes the ice.
This process is far more rapid in West Antarctica than in East Antarctica where it is quite patchy, with areas of thickening and thinning.
Glaciologist Professor Matt King said a strength of this research was that it observed both
Wed 11th Feb 2015
picture by Peter Mathew
grounded ice such as glaciers and land ice extending onto the sea, whereas previous studies focused on just one or the other.
“We know that ice on land responds to ice extending onto the sea, so looking at the ice sheet as a whole is an advance,” said Professor King of the University of Tasmania.
Study co-author Professor Helen Amanda Fricker of the University of California said sea ice has previously been excluded because melting ice on land directly contributes to sea level rises, whereas sea ice melt does not.
But, she said, scientists need to know how ice sheets are changing if we are going to be able to predict how grounded ice might leave the Antarctic continent.
Professor Fricker is calling for more on-the-ground research in East Antarctica, where Australia’s research bases are located.
“Key systems are changing in East Antarctica, it’s in Australia’s backyard,” she said.
Professor King agreed, saying “Satellite studies provide a great continental view, but we also need good field measurements to understand what’s going on in these vulnerable places.”
“We don’t really know enough about East Antarctica to understand the changes going on,” he said.
“So, we are left with a general state of confusion, flying blind from both direction
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