It is not in the Arctic, but in Antarctica, where the Earth is at stake
05/20/2021 at 8:04 AM CEST
It is not the melting of the Arctic, but the Antarctic that really threatens the planet as a result of climate change. Scientists have just verified that if current emission rates continue in 2060, the situation in Antarctica will enter a point of no return that will trigger irreversible effects for the entire planet.
By: Julie Brigham-Grette and Andrea Dutton (The Conversation)
While US Secretary of State Anthony Blinken recently drew attention to the dire situation in the Arctic on his official trip to Iceland, the truth is that an even greater threat lurks on the other side of the planet.
New research shows that it is actually Antarctica that will test the decisions countries make on greenhouse gas emissions. It will be the Antarctic region that will really determine the survival of coasts and coastal cities, from New York to Shanghai.
The Arctic is losing ice as global temperatures rise, and that is directly affecting biodiversity and causing feedback loops that favor further warming.
But the big driver for sea level rise is Antarctica. It contains enough land ice to raise global sea levels by more than 200 feet, roughly ten times what the Greenland ice sheet could raise it, and we are already seeing disturbing signs.
Scientists have long known that the Antarctic ice sheet exhibits physical tipping points, beyond which ice loss can accelerate uncontrollably.
The new study, published in the journal Nature, notes that the Antarctic ice sheet could reach one of those critical tipping points in a few decades, when the children who go to primary school today are raising their families.
The results obtained show that an argument often used for not reducing greenhouse gas emissions adequately, since technological advances may save us in the future, will probably fail.
2060: critical threshold
The new study claims that if emissions continue at their current rate, By about 2060, the Antarctic ice sheet will have crossed a critical threshold and it will have committed the world to a rise in sea level that will no longer be reversible on human timescales.
Capturing carbon dioxide from the atmosphere at that time will no longer stop the loss of ice and by 2100 the sea level could be rising more than 10 times faster than today.
Antarctica has several protective ice shelves that fan out into the ocean, facing glaciers that constantly flow from the frozen continent. These protective barriers slow down the flow of glaciers into the sea. But those platforms can ‘thin’ and break as warmer water moves underneath them.
And as those ice shelves break, towering ice cliffs can collapse that will no longer be able to support themselves.
Two types of instability can occur. Parts of the Antarctic ice sheet are ‘anchored’ below sea level on a bedrock that slopes toward the center of the continent, so warming ocean water can eat away at the lower edges of this ice sheet. ice, destabilizing them and causing them to retreat down the slope rapidly.
And, above water, surface melt and rain can open fractures in the ice. When ice cliffs become too high to hold, they can catastrophically collapse, accelerating the speed of ice flow into the ocean.
The study used computer models based on the physics of ice sheets and found that, above 2 ° C warming, Antarctica will experience a sharp jump in ice loss, caused by the rapid loss of ice through the huge Thwaites Glacier.
This glacier is in charge of draining an area the size of Florida or Great Britain and is the focus of an intense study by American and British scientists, due to its worrying situation.
To get an idea of the situation, the planet is currently on the way to surpass those 2ºC of warming, taking into account the climate policies of the countries.
Other projections do not take into account the instability of ice cliffs and thus generally arrive at lower estimates for the rate of sea level rise.
While much of the journalistic reporting on this investigation focused on the differences between these two approaches, in reality they both reach the same fundamental conclusions: the magnitude of sea level rise can be drastically reduced if targets are met of the Paris Agreement and physical instabilities in Antarctica.
The stage from 2100
Furthermore, the new study, led by Robert DeConto, David Pollard and Richard Alley, is one of the few that looks beyond this century and predicts what will happen after 2100.
The study shows that if today’s high emissions continue unabated until 2100, sea level rise would “explode & rdquor;, surpassing six centimeters per year by 2150. By 2300, sea level would be ten times higher than it is expected to be if countries meet the goals of the Paris Agreement.
A warmer, smoother ice sheet and a warming ocean that also maintains its heat for centuries prevent the protective ice sheets of Antarctica from re-freezing, leading to a very different world. authors.
The vast majority of measures to comply with the Paris Agreement assume that emissions will exceed the targets of keeping warming below 1.5 ° C or 2 ° C, but that future technological advances will then be available to remove enough carbon dioxide. carbon in the air and thus lower the temperature again later.
Although most countries, including the US, the EU and Great Britain, have set emission reduction targets, current global policies would only result in a 1% reduction by 2030. “Instead, it’s about reducing emissions quickly,” warns the study.
Some researchers suggest that the ice cliffs of Antarctica may not collapse as fast as those of Greenland. But given their size and current rates of warming, which are faster than in historical records, what if instead they collapsed more quickly?
The three messages from Antarctica
As countries prepare to increase the targets of the Paris Agreement ahead of the United Nations meeting in November, Antarctica has three important messages that we would like to highlight as polar and ocean scientists.
-First, every fraction of a degree centigrade matters.
-In second place, allowing global warming to exceed 2 ° C is not an option realistic for coastal communities or the global economy. The comforting prospect of technological solutions that allow a later return to normalcy is an illusion that will leave the coasts under many inches of water, with devastating economic impacts.
-In third place, today’s policies must have a long-term vision, because they can have irreversible impacts on the ice of Antarctica and the world. During the last decades, much of the attention on rapid climate change has focused on the Arctic and its rich mosaic of indigenous cultures and indigenous ecosystems that are under threat.
But as scientists learn more about Antarctica, it becomes clear that it is this continent, with no permanent human presence at all, that will determine the state of the planet where today’s children and their children will live.
Study published in Nature: https://www.nature.com/articles/s41586-021-03427-0
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