This weekend several media reported about the impending rupture of a gigantic ice shelf on the Antarctic Peninsula. Satellite images leave no doubt. A huge chunk of ice as big as North and South Holland combined, is about to break off from the Larsen C Ice Shelf at the South Pole. “A clear signal of the thermometer of the planet.”
Barbara Debusschere wrote in de Volkskrant:
A huge ice sheet as big as North and South Holland threatens to tear off from the part of Antarctica that is hanging in the sea. “Alarming. We did not expect that global warming would already affect the largest ice shelfs,” say researchers.
The gigantic chunk of ice that is about to break off is part of theLarsen CIce Shelf, the largest plate in the eastern part of the Antarctic Peninsula. Larsen C is an extension of the ice cap on land and has been there for thousands of years, possibly even a hundred thousand. All that time it was never subject to this type of decay.
But based on satellite images British and German glaciologists show that one crack in a short time has become so large that it is now “inevitable that a huge piece breaks off” – so they write in the journal The Cryosphere. In the least severe scenario 4,600 square kilometers will disappear in the sea, while in another 6,400 square kilometers. It means that the ice sheet loses respectively nine to twelve percent of its surface, good for an area as large as North and South Holland combined.
And that is disturbing. The breaking up of ice shelves pulls an important ‘plug’ from the glaciers of Antarctica. The ice shelf works like a ‘brake’ without which the glaciers slide into the sea accelerated, which makes the sea level rise. In 2002, the smaller Larsen B Ice Shelf already disintegrated, which meant that the glaciers were no longer held back by the ice and flocked into the sea upto eight times faster – and the sea level did rise. This effect can also be expected on the Larsen C Ice Shelf.
The stability of the entire Larsen C Ice Shelf is now threatened. The researchers warn explicitly for this. “When this piece breaks off, the front of the ice shelf becomes unstable, and risks to collapse completely. That would be dramatic because then all glaciers in this area would slide into the sea very rapidly,” says Michiel van den Broeke, Professor of Polar Meteorology (University of Utrecht) and not involved in the research.
When the large piece breaks off, Larsen C will be smaller than ever since the last ice age. “A clear signal that things are heating up,” says Van den Broeke. “Larsen C is hundreds of meters thick. But now it warms up from two sides: through the warmer air and through the warmer seawater.” Since the eighties, experts see that as a result of this in the Antarctic Peninsula and West Antarctica, the warmest areas of Antarctica, more and more ice shelves are thinning or breaking down, and that because of this also the land ice is losing mass. Van den Broeke: “That even the Larsen C Ice Shelf, which is five times larger than the Larsen B Ice Shelf that already disappeared, now already no longer withstands the global warming, is unexpected. A clear signal of the thermometer of the planet.“
The article by Barbara Debusschere – in Dutch – can be read on the webpages of de Volkskrant – please click here.
A visualization of how the ice shelf rupture impacts glaciers:
For NASA report and images of the Larsen B Ice Shelf collapse in 2002: go here.