Apr 12, 2021 06:00:00

One-third of Antarctica's ice shelves can collapse when average temperatures rise by another 2.75 degrees Celsius

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OVERVIEW

Ice shelves are ice formed so that they protrude from the land into the sea. There are various ice shelves in Antarctica, including the Ross Ice Shelf, which is the largest ice shelf in the world, but one-third of them have been found to collapse when the average temperature of the earth rises by 4 degrees Celsius. It was announced.

Surface melt and runoff on Antarctic ice shelves at 1.5 ° C, 2 ° C and 4 ° C of future warming --Gilbert ---- Geophysical Research Letters --Wiley Online Library
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091733

Guest post: The fate of Antarctic ice shelves at 1.5C, 2C and 4C of warming | Carbon Brief
https://www.carbonbrief.org/guest-post-the-fate-of-antarctic-ice-shelves-at-1-5c-2c-and-4c-of-warming

When the temperature rises in Antarctica in the summer, the surface of the ice melts and water flows into the crevasse , but the amount of water that flows in exceeds a certain level, and when they freeze again, the pressure pushes the crevasse apart. The phenomenon that the ice shelf collapses occurs. This process caused the Larsen A Ice Shelf to collapse in 1995 and the Larsen B Ice Shelf to collapse in 2002. The Larsen B Ice Shelf is said to have a history of 12,000 years and its surface area is estimated to be 3275 square kilometers.

Antarctic ice shelves grow when snow accumulates faster than they melt, and conversely decrease when the amount of snow melts exceeds the amount of snowfall. This balance between surface melting and snowfall is called the surface mass balance (SMB) and is closely related to the formation of ice shelves. Ella Gilbert, a climate scientist at the University of Reading in the United Kingdom, said how the SMB changes and shelves when the average global temperature rises 1.5, 2 or 4 degrees above the pre-industrial temperature. We investigated whether it affects ice by simulation. As a result, at moderate temperature rises such as 1.5 ° C and 2 ° C, the melting of ice shelves falls within the range compensated by snowfall, but at 4 ° C, the SMB collapses and snowmelt water increases, and the Antarctic Peninsula shelves. It has been shown that 34% of the ice area, or about 500,000 square kilometers, is at risk of collapse.

Regarding Gilbert's comparison of temperatures with those before the Industrial Revolution,

the purpose of the Paris Agreement on climate change control is to 'keep the world's average temperature rise from before the Industrial Revolution to less than 2 degrees Celsius. In addition, the average temperature rise. It is thought that the reason is that we aim for less than 1.5 degrees. According to data from the EU meteorological intelligence agency 'Copernicus Climate Change Service' released in 2021, the average temperature in 2020 is about 1.25 degrees higher than before the Industrial Revolution. When Mr. Gilbert compared the simulation results with the actual amount of snowmelt, the numerical value calculated by the simulation was slightly higher.

'It's also important which ice shelf the snowmelt occurs on,' Gilbert said. If snowmelt occurs in only a small area of the ice shelf, it is less likely to collapse, but if it occurs in most of the ice shelf, it is more likely to collapse. From a geographic and structural point of view, Gilbert estimates that there are six ice shelves that are likely to collapse, including the Abbot Ice Shelf and the Shackleton Ice Shelf.

Since ice shelves float on water, even if ice shelves collapse, they do not directly lead to sea level rise. However, ice shelves play a major role in the formation and maintenance of glaciers on land, and without ice shelves, continental ice tends to flow into the sea, which certainly has an indirect effect on sea level rise. 'Maintaining ice shelves means reducing global sea level rise, which has a positive impact on us,' Gilbert said.