Post by Andrei Tchentchik on Mar 12, 2020 18:54:51 GMT 2
(.#A.079).- Antarctica, the melting of the Thwaites glacier would create the domino effect.
In Antarctica, how the melting of a Florida-sized glacier could trigger a domino effect
02/18/2019
By Pierre Ropert
In western Antarctica, a huge glacier, the Thwaites Glacier, is on the way to break away from the frozen continent. It could cause a chain reaction which, over time, would cause the sea level to rise by more than 2 meters.
Molten water flows from an ice cliff • Credits: Michael Melford - Getty
120 km wide, 600 km long and up to 3 km thick in places, the Thwaites glacier, which is roughly the size of Florida (or a quarter of France) is likely to become detach from the ice in the more or less long term. And according to a study published on January 30, 2020 in the journal Science Advances, this glacier indeed holds a sad record: it is one of the fastest melting in Antarctica.
"We have suspected for years that Thwaites was not firmly attached to the bedrock beneath it," commented glaciologist Eric Rignot, co-author of the publication and researcher at NASA's Jet Propulsion Laboratory. Thanks to NASA's IceBridge operation since 2010, researchers have been able to observe that a huge cavity had gradually formed under the glacier: 14 billion tonnes of ice have already melted, in digging a hole with a length of 10 km by 4 wide, and a height of 300 meters. And satellite data has identified several other smaller cavities at various locations under the ice.
The Thwaites glacier seen from the sky. • Credits: NASA / OIB / JEREMY HARBECK
A domino effect
Eroded from the inside, this gigantic glacier is already responsible alone for 4% of the rise in water levels. However, the larger the underground cavity, the less Thwaites is in contact with the rocky ground, and the more it is likely to come off. If it were to melt completely, it would be responsible for a rise in sea level of up to 65 cm.
Worse even, according to Eric Rignot, this "glacier of death" risks above all causing a domino effect, as he told FranceTVInfo :
By retreating, the glacier should come off and, as in a domino fall, should drag the other glaciers of West Antarctica, creating a catastrophic scenario. (...) Which means that West Antarctica is, in the long term, doomed to disappear, I do not think that the public and the media realize very well the importance of what is happening in Antarctica and in the polar regions: it's a disaster.
Recently invited by La Method Scientifique, the glaciologist and CNRS research director at the glaciology laboratory Catherine Ritz reminded the mechanics of this melting ice (41 '):
This loss of ice occurs because the glaciers have accelerated and send more ice towards the ocean, especially in West Antarctica. And the reason they accelerated is because the glaciers, by floating on the sea, create platforms that touch each other at the edges and slow them down. Apparently ocean warming has thinned these platforms, which have broken more easily, friction has decreased, and the glaciers have started to accelerate. As in Western Antarctica the continental basement is frankly below sea level, this situation is mechanically unstable. (...) We think that one of the glaciers that lost the most mass, that of Pine Island, has already gone into this instability. The other glacier, that of Thwaites, more and more results show that this glacier also leaves in this instability. And frankly the simulations show that even with the current climate it is quite possible that it continues to retreat ... And this glacier has the capacity to empty half of West Antarctica. Ultimately, it can cause 2 meters of sea level rise alone.
If all the glaciers of the West Antarctic region were to detach and be affected by the melting of the ice, the level of the oceans could indeed rise, still according to the study, by 2.4 meters .
A global font
Another study published two weeks earlier in the Journal of the American Academy of Sciences (PNAS) confirmed that Antarctica is melting much faster than expected. If between 1979 and 1990, Antarctica lost an average of 40 billion tonnes of ice mass per year, since 2009, the average figure rises to 252 billion tonnes each year.
Since 1993, the level of the oceans has risen about ten centimeters. If the figure seems low, Eric Rignot says predict "a rise in ocean levels of several meters in the coming years". The ice cap of East Antarctica, if it melts, could indeed cause, according to the study published in PNAS, a rise in sea level by 52 meters.
Pierre Ropert.
F I N .
In Antarctica, how the melting of a Florida-sized glacier could trigger a domino effect
02/18/2019
By Pierre Ropert
In western Antarctica, a huge glacier, the Thwaites Glacier, is on the way to break away from the frozen continent. It could cause a chain reaction which, over time, would cause the sea level to rise by more than 2 meters.
Molten water flows from an ice cliff • Credits: Michael Melford - Getty
120 km wide, 600 km long and up to 3 km thick in places, the Thwaites glacier, which is roughly the size of Florida (or a quarter of France) is likely to become detach from the ice in the more or less long term. And according to a study published on January 30, 2020 in the journal Science Advances, this glacier indeed holds a sad record: it is one of the fastest melting in Antarctica.
"We have suspected for years that Thwaites was not firmly attached to the bedrock beneath it," commented glaciologist Eric Rignot, co-author of the publication and researcher at NASA's Jet Propulsion Laboratory. Thanks to NASA's IceBridge operation since 2010, researchers have been able to observe that a huge cavity had gradually formed under the glacier: 14 billion tonnes of ice have already melted, in digging a hole with a length of 10 km by 4 wide, and a height of 300 meters. And satellite data has identified several other smaller cavities at various locations under the ice.
The Thwaites glacier seen from the sky. • Credits: NASA / OIB / JEREMY HARBECK
A domino effect
Eroded from the inside, this gigantic glacier is already responsible alone for 4% of the rise in water levels. However, the larger the underground cavity, the less Thwaites is in contact with the rocky ground, and the more it is likely to come off. If it were to melt completely, it would be responsible for a rise in sea level of up to 65 cm.
Worse even, according to Eric Rignot, this "glacier of death" risks above all causing a domino effect, as he told FranceTVInfo :
By retreating, the glacier should come off and, as in a domino fall, should drag the other glaciers of West Antarctica, creating a catastrophic scenario. (...) Which means that West Antarctica is, in the long term, doomed to disappear, I do not think that the public and the media realize very well the importance of what is happening in Antarctica and in the polar regions: it's a disaster.
Recently invited by La Method Scientifique, the glaciologist and CNRS research director at the glaciology laboratory Catherine Ritz reminded the mechanics of this melting ice (41 '):
This loss of ice occurs because the glaciers have accelerated and send more ice towards the ocean, especially in West Antarctica. And the reason they accelerated is because the glaciers, by floating on the sea, create platforms that touch each other at the edges and slow them down. Apparently ocean warming has thinned these platforms, which have broken more easily, friction has decreased, and the glaciers have started to accelerate. As in Western Antarctica the continental basement is frankly below sea level, this situation is mechanically unstable. (...) We think that one of the glaciers that lost the most mass, that of Pine Island, has already gone into this instability. The other glacier, that of Thwaites, more and more results show that this glacier also leaves in this instability. And frankly the simulations show that even with the current climate it is quite possible that it continues to retreat ... And this glacier has the capacity to empty half of West Antarctica. Ultimately, it can cause 2 meters of sea level rise alone.
If all the glaciers of the West Antarctic region were to detach and be affected by the melting of the ice, the level of the oceans could indeed rise, still according to the study, by 2.4 meters .
A global font
Another study published two weeks earlier in the Journal of the American Academy of Sciences (PNAS) confirmed that Antarctica is melting much faster than expected. If between 1979 and 1990, Antarctica lost an average of 40 billion tonnes of ice mass per year, since 2009, the average figure rises to 252 billion tonnes each year.
Since 1993, the level of the oceans has risen about ten centimeters. If the figure seems low, Eric Rignot says predict "a rise in ocean levels of several meters in the coming years". The ice cap of East Antarctica, if it melts, could indeed cause, according to the study published in PNAS, a rise in sea level by 52 meters.
Pierre Ropert.
F I N .
