A special issue of Nature has published a series of studies that investigate how space monitoring of Antarctica offers crucial insights into the response to a warming climate.
Here are their main findings:
Since 1992, three trillion tons of ice from Antarctica have been lost
The Antarctic ice sheet lost around three trillion tons of ice between 1992 and 2017, according to research from the University of Leeds.
This figure corresponds to an average sea level rise of about eight millimeters (1/3 inch), with two-fifths of this rise in the last five years alone.
The finds mean that people in coastal communities run a greater risk of losing their homes and becoming so-called climate refugees than previously feared.
In one of the most complete photos of the Antarctic ice sheet so far, an international team of 84 experts have combined 24 satellite surveys to deliver the results.
It discovered that Antarctica lost ice until 2012 at a constant speed of 76 billion tons per year – a 0.2 mm (0.008 inch) contribution per year to sea level rise.
Since then, however, there has been a sharp, triple increase.
At some point since the last ice age, the West Antarctic ice sheet was smaller than now
Researchers previously believed that since the last ice age, about 15,000 years ago, the West Antarctic Ice Sheet (WAIS) became smaller
However, new research published by Northern Illinois University shows that between 14,500 and 9,000 years ago, the ice sheet below sea level was even smaller than today.
In the following millennia, the loss of the enormous amount of ice that previously weighed on the seabed caused the seabed to rise.
Then the ice sheet began to grow again in the direction of today’s configuration.
“Today’s WAIS is retreating, but there was a time since the last ice age that the ice sheet was even smaller than it is today, but it did not collapse,” said geologist professor Reed Scherer of Northern Illinois University. on the study.
“That is important information that we need when trying to figure out how the ice sheet will behave in the future,” he said.
The East Antarctic ice sheet was stable during the last warm period
The stability of the largest ice sheet on Earth is an indication for scientists that it could hold if temperatures keep rising.
If all the East Antarctic ice sheet were to melt, the sea level would rise by 53 meters.
However, unlike Greenland and West Antarctic ice sheets, it appears to be resistant to melting when conditions are warm, according to research from Purdue University and Boston College.
Their research showed that land-based sectors of the East Antarctic ice sheet were largely stable throughout the Pliocene (5.3 to 2.6 million years ago).
This was when the carbon dioxide concentrations in the atmosphere were close to what they are today – around 400 parts per million.
“Based on this evidence from the Pliocene, today’s carbon dioxide content is not enough to destabilize the ice on the Antarctic continent,” said Jeremy Shakun, lead author of the paper and assistant professor of earth and environmental science at Boston College .
“This does not mean that Antarctica at current atmospheric carbon dioxide levels does not contribute to the rise in sea level.
“Sea-based ice can contribute very well and is already contributing, and that alone means an estimated 20-meter rise in sea level,” he said.
Decisions in the next decade will determine whether Antarctica contributes to a meter rise in sea level
One of the greatest uncertainties in future sea level rise predictions is how the Antarctic ice sheet responds to man-made global warming.
Scientists say the time to save this unique ecosystem is running out and if the right decisions are not made in the next ten years, there is no turning back.
Researchers at Imperial College London assessed the state of Antarctica in 2070 on the basis of two scenarios representing the opposite extremes of action and inactivity in the field of greenhouse gas emissions.
Under high emissions and low regulations, Antarctica and the Southern Ocean are undergoing major and rapid changes, with global consequences.
By 2070, global warming and the atmosphere have caused dramatic loss of large ice sheets, leading to a greater loss of grounded ice from the Antarctic ice sheet and an acceleration of global sea level rise.
Under the low emission and tight regulatory narrative, reducing greenhouse gas emissions and implementing effective policies to minimize changes in Antarctica helps, which looks a lot in 2070 as it did in the early decades of the century.
This ensures that the ice plates of Antarctica remain intact, thus delaying ice loss through the ice sheet and reducing the threat of sea level rise.
What saved the West Antarctic ice sheet 10,000 years ago will not make it today
The retreat of the West Antarctic ice masses after the last ice age was surprisingly reversed about 10,000 years ago, scientists found.
In fact, it was the shrinking itself that stopped the shrinking: released from the weight of the ice, the earth’s crust was lifted and the recoil of the ice cap triggered.
According to research by the Potsdam Institute for Climate Impact Research (PIK), this mechanism is far too slow to prevent dangerous sea level rise due to ice loss in West Antarctica in the present and near future.
Researchers believe that only rapid reductions in greenhouse gas emissions are possible.
“The warming after the last ice age reduced the ice masses of West Antarctica,” said Torsten Albrecht of the Potsdam Institute for Climate Impact Research.
“Unfortunately, given the speed of current climate change caused by burning fossil fuels, the mechanism we have detected is not working fast enough to protect today’s ice sheets from melting and seas rising.”
The ice shelves of the world may be destabilized by forces from above and below
Researchers discovered that warm ocean water that flows in channels under Antarctic ice plates thins the ice from below so that the ice bursts in the channels.
Surface melt water can then flow into these fractures, further destabilizing the ice sheet and increasing the chance of substantial pieces breaking away.
The researchers, led by the University of Texas at Austin, documented this mechanism during a major ice demolition or calving event in 2016 at Antarctica’s Nansen Ice Shelf.
The findings are concerned because ice shelves, floating expansions of continental glaciers, slow the ocean ice flow and help control the speed of sea level rise, according to the study.
“We learn that ice shelves are more vulnerable to rising ocean and air temperatures than we thought,” said Professor Christine Dow, lead author of the study.
‘There are double processes going on here. One that destabilizes from below and another from above.
“This information can have an impact on our expected timelines for the collapse of ice shelves and the resulting rise in sea level due to climate change,” he said.