[ad_1]
Media playback is not supported on your device
Scientists have published a new analysis of how the Greenland and Antarctic ice sheets have changed, from 2003 to 2019.
The study shows that ice losses from thawing have outpaced increases in snowfall, resulting in a 14mm rise in global sea levels during the period.
We have had a number of reports very similar to this recently.
What makes it interesting is that it uses data from the highest resolution satellite system dedicated to the study of the poles: IceSat.
Image copyright
POT
Work: IceSat-2 orbits Earth at an altitude of about 500 km
This system flies space lasers over glaciers and other ice fields to track its ever-changing shape.
The US space agency (NASA) has now launched two of these altimeter instruments.
The first, IceSat, ran between 2003 and 2009; the second, IceSat-2, was installed in 2018.
Thursday’s report is a first attempt to link observations from both satellites.
“We have essentially put the two separate missions into one giant mission to tell the story of what happened over the 16 years,” said Dr. Ben Smith, a glaciologist at the University of Washington.
“Working with this long period of time, we may be much less concerned with seeing short-term behaviors that are not as relevant to the long-term evolution of the ice sheets, as if it snowed a bit more this year than last year” The 16 years give us a clear picture, “he told BBC News.
Media playback is not supported on your device
The main results of the analysis underline the impacts of a warmer climate.
Greenland is losing an average of approximately 200 gigatons (billion tons) of ice per year. Antarctica is shedding an average of about 118 gigatons per year.
A gigatona of ice is enough water to fill 400,000 Olympic swimming pools.
In other words, the sum of the loss of ice from both polar regions (5,088 gigatons) during the study period could fill Lake Michigan in the United States.
The interior of Greenland at the highest elevations, above 2,000 m, is actually accumulating mass for more snowfall, but this cannot compete with the melting around the coast, where warmer atmospheric and ocean temperatures are eating up the surface and fronts of glaciers.
Media playback is not supported on your device
- Antarctic ‘doomsday’ glacier trip
- Greenland ice faces melting ‘death sentence’
It is not a very different image in Antarctica. In the east of the continent, the height of the ice sheet is increasing, again due to more snowfall, but the gains are outweighed by melting in the west, particularly on those glaciers that reach the Amundsen and Bellingshausen seas.
Thwaites and Pine Island are two of those glaciers whose thinning trends have recently drawn attention.
All the numbers in the IceSat analysis are at the same stage as the recent Imbie reports for Greenland and Antarctica. Imbie compared many different satellite data sets to try to come up with a single coherent narrative.
Image copyright
Kate Ramsayer / NASA
Antarctica has the equivalent of almost 60 meters of sea level elevation enclosed in its ice.
One area in which the new IceSat study stands out is in its detailed assessment of Antarctic ice shelves. These are the floating ridges of glaciers that line the entire continent, and Imbie did not consider them to the same degree.
“About a third of ice loss in West Antarctica comes from ice shelves,” said Professor Helen Amanda Fricker of the Scripps Institution of Oceanography.
“The reason this is important is because the ice shelves retain the crushed ice behind, and any thinning causes this restraining force to be reduced. So what is happening is that the crushed ice in West Antarctica is now flowing faster to the ocean. “
The fraction of a third is most likely an understatement. That’s because in producing their report, IceSat scientists only considered those ice surfaces that could be seen on both missions. And with some ice shelves retreating into the area in the intervening years, there will be mass losses that have simply been omitted from the calculations.
Image copyright
NASA / SCRIPPS / S.ADUSUMILLI
IceSat-2 resolution allows you to map cracks in the surface of the ice sheet
Dr. Anna Hogg works with European satellite systems that measure the shape of ice sheets with radar instruments.
You’ve been impressed by the keen vision of the new IceSat mission.
“It is exciting to see how the new IceSat-2 high-resolution laser can be used to observe cracks 80m deep in Antarctica, such as those on the Ross Ice Shelf,” he told BBC News.
“These results provide independent confirmation that Greenland and Antarctica are losing ice at an increasingly rapid rate.”
“In the future, we must use this satellite data revolution to help improve our understanding of oceanographic and atmospheric processes that are driving change in remote polar regions,” he told BBC News.
The IceSat study is published in the journal Science.
[email protected] and follow me On twitter.
[ad_2]
