Scientists release the highest resolution map of Antarctica

<pre><pre>Scientists release the highest resolution map of Antarctica

A special issue of Nature has published a series of studies that analyze how monitoring of Antarctica from space provides crucial information about its response to a warming climate.

These are his main findings:

Three trillion tons of ice have been lost from Antarctica since 1992

The ice sheet in Antarctica lost about three trillion tons of ice between 1992 and 2017, according to a study conducted by the University of Leeds.

This figure corresponds to an average elevation of sea level of approximately eight millimeters (1/3 of an inch), with two fifths of this increase in the last five years alone.

The findings mean that people in coastal communities are at greater risk of losing their homes and becoming so-called climate refugees than previously feared.

In one of the most complete images of the change of the Antarctic ice sheet to date, an international team of 84 experts combined 24 satellite surveys to show the results.

It was found that until 2012, Antarctica lost ice at a constant rate of 76 billion tons per year, a contribution of 0.2 mm (0.008 inches) per year to sea level rise.

However, since then there has been a sharp increase of three times.

At some time since the last Ice Age, the ice sheet of West Antarctica was smaller than it is today

Researchers previously believed that since the last ice age, about 15,000 years ago, the West Antarctic ice sheet (WAIS) was becoming smaller and smaller.

However, new research published by Northern Illinois University shows that between approximately 14,500 and 9,000 years ago, the ice sheet below sea level was even smaller than today.

During the following millennia, the loss of the enormous amount of ice that previously weighed on the seabed caused an uplift at the bottom of the sea.

Then, the ice sheet began to grow back to the current configuration.

"The WAIS of today is receding again, but there has been a time since the last ice age when the ice sheet was even smaller than it is now, but it did not collapse," said Reed Scherer, professor of geology at the University of North Illinois. in the study.

"That's important information we should have while trying to figure out how the ice sheet will behave in the future," he said.

The ice sheet of East Antarctica remained stable during the last warm period

The stability of Earth's largest ice sheet is an indication to scientists that it could be maintained as temperatures continue to rise.

If the entire ice sheet of East Antarctica melted, the sea level would rise by 175 feet (53 meters).

However, unlike the ice sheets of Greenland and West Antarctica, it appears to be resistant to melting as conditions warmer, according to a study by Purdue University and Boston College.

His research showed that the land sectors of the eastern Antarctic ice sheet were mostly stable throughout the Pliocene (5.3 to 2.6 million years ago).

This is when the concentrations of carbon dioxide in the atmosphere were close to what they are today: around 400 parts per million.

"Based on this Pliocene evidence, current current levels of carbon dioxide are not enough to destabilize land ice on the Antarctic continent," said Jeremy Shakun, lead author of the paper and assistant professor of environmental and land sciences. at Boston College. .

"This does not mean that at current levels of carbon dioxide in the atmosphere, Antarctica will not contribute to sea level rise."

"Sea-based ice could, and in fact is already beginning to contribute, and that alone has an estimated 20 meters of sea level rise," he said.

Decisions in the next decade will determine if Antarctica contributes to one meter of sea level rise

One of the biggest uncertainties in future predictions of sea level rise is how the Antarctic ice sheet reacts to global warming induced by humans.

Scientists say that time is running out to save this unique ecosystem and that if the right decisions are not made in the next ten years, there will be no turning back.

Researchers from Imperial College London evaluated the state of Antarctica in 2070 under two scenarios that represent opposite extremes of action and inaction on greenhouse gas emissions.

Under the narrative of high emissions and low regulations, Antarctica and the Southern Ocean undergo a generalized and rapid change, with global consequences.

By 2070, the warming of the ocean and the atmosphere has caused a dramatic loss of large ice shelves, which has caused a greater loss of ice from the Antarctic ice sheet and an acceleration in the rise in sea level world.

Under the narrative of low emissions and strict regulations, the reduction of greenhouse gas emissions and the implementation of effective policies helps to minimize the changes in Antarctica, which in 2070 is very similar to what happened in the first decades of the century.

This makes the Antarctic ice shelves remain intact, reducing the loss of ice from the ice sheet and reducing the threat of sea level rise.

What saved the ice sheet of Western Antarctica 10,000 years ago will not save it today

The removal of ice masses from West Antarctica after the last Ice Age was surprisingly reversed some 10,000 years ago, the scientists found.

In fact, it was the contraction itself that stopped the contraction: relieved by the weight of the ice, the earth's crust rose and caused the ice sheet to advance.

According to research by the Potsdam Institute for Climate Impact Research (PIK), this mechanism is too slow to avoid the dangerous rise in sea level caused by the loss of ice in West Antarctica in the present and in the near future.

According to the researchers, only rapid reductions in greenhouse gas emissions can occur.

"The warming after the last Ice Age caused ice masses in West Antarctica to be reduced," said Torsten Albrecht of the Potsdam Institute for Climate Impact Research.

"Given the speed of current climate change due to the burning of fossil fuels, the mechanism we detect unfortunately does not work fast enough to prevent the current ice sheets from melting and causing the seas to rise."

The world's ice shelves may be being destabilized by forces from above and below

The researchers found that the warm ocean water that flows into the channels beneath the Antarctic ice shelves is reducing ice from below so much that the ice in the channels is cracking.

The molten surface water can flow into these fractures, further destabilizing the ice shelf and increasing the chances of substantial pieces coming off.

The researchers, led by the University of Texas at Austin, documented this mechanism at a major ice-breaking or calving event in 2016 on the Nansen ice shelf in Antarctica.

The findings are worrisome because ice shelves, which are floating extensions of continental glaciers, reduce the speed of ice flow in the ocean and help control the rate of sea level rise, according to the study.

"We are learning that ice shelves are more vulnerable to rising ocean and air temperatures than we thought," said Christine Dow, lead author of the study.

& # 39; There are dual processes happening here. One that is destabilized from below, and another from above.

"This information could have an impact on our projected schedules for the collapse of the ice shelf and the resulting increase in sea level due to climate change," he said.