More than half of the ice sheets hitting Antarctica are preventing huge glaciers from entering the ocean and raising sea levels due to climate change, researchers said Wednesday.
Due to the warm air, the molten water flowing in the deep rupture damages the structural integrity of this natural barrier. Nature.
“If ice shelves are filled with melted water, things can happen very quickly,” said Jonathan Kingslake, co-author of Glaciologist at Columbia University’s Lamont-Doherty Earth Observatory.
“There could be big consequences for the sea surface.”
Scientists are particularly concerned about the poor state of the ice sheets behind West Antarctica’s Pine Island and the White Glaciers, which could extend the world’s oceans by more than three meters if destabilized.
The two glaciers cover a larger area than Germany.
Up to one kilometer thick, ice shelves are solid ice extensions of land-bound glaciers.
Because they are already floating on the ocean water, they do not rise above sea level when the huge chunk is broken as an iceberg.
But part of the Antarctic ice sheet – which prevents large-scale glaciers from sliding into the ocean – has already become a major contributor to sea level rise.
The United Nations’ Climate Change Science Advisory Panel, the IPCC, has predicted that by the end of the century, the oceans will have risen by one meter, and even more by then.
Millions of people live within a few meters of sea level.
Ice shelves are often built on landforms such as the mouth of a bay, which helps them resist the pressure of glaciers pushing them towards the sea.
But climate change is erasing them in more ways than one.
Previous research has shown that sea water is passing through the grounding line at warmer temperatures – where the ice shelf begins – and below the glaciers, lubricating their motion toward the ocean.
New findings show that even from above atmospheric temperatures ice is attacking shelves.
Violent fracturing
The Earth’s average temperature has risen by one degree Celsius since the 19th century, enough to increase the intensity of droughts, heat waves, and tropical cyclones.
But the air over Antarctica has warmed more than twice as much.
One result of this is the appearance of long crevices parallel to the shoreline – at the top of the ice shelves – up to ten meters deep.
The surface ice melts, water is poured into the debris and the possibility of a process called hydrofecturing increases.
When this happens, the water – which is heavier than ice – “violently forces the fracture to open the zip and cause the shelf to disintegrate quickly,” the researchers said in a statement.
The Antarctic Peninsula, which is warmer than other parts of the continent, has shown in dramatic fashion what this could result in.
The main part of the Larsen Ice Shelf on the peninsula – which has been stable for more than 10,000 years – disintegrated in 1995 and again in 2002 in several parts. This was followed by the collapse of the nearby Wilkins Ice Shelf in 2008 and 2009.
In both cases, there is the full potential for hydrofeeding.
To find out which regions of the continent are most vulnerable, Kingslake and his colleagues used a machine-learning algorithm to analyze satellite images and prepare the first complete mapping of Antarctica’s ice shelves and their craves.
They estimate that glaciers are 50 to 70 percent more likely to be hydrofractured than Buttress.
Jeremy Basis, a scientist at the University of Michigan, also wrote in a commentary on Nature, “Together, the author’s findings point to the part of the ice shelf that is most sensitive to atmospheric temperature.”
“They show that most of the sections that are currently stable could collapse as atmospheric temperatures rise.”
ન્સી Agency France-Press
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