Something Below The Ice Is Slicing Through An Ice Shelf In Antarctica

Satellite data showing the ice canyon on the right. Gourmelen/ESA

If a giant hole wasn't enough, we've got more bad news. Scientists have discovered a huge inverted canyon under an ice shelf in Antarctica, which might cause its demise much quicker than expected.

Using the ESA’s CryoSat satellite and the Copernicus Sentinel-1 mission, researchers looked at the Dotson ice shelf in West Antarctica. Here, they found a channel 5 kilometers (3 miles) wide that runs for 60 kilometers (37 miles) along the bottom of the shelf. From the surface, everything seems normal and flat.

The Dotson ice shelf has an area of about 3,500 square kilometers (1,350 square miles) and is between 300 and 490 meters (1,000 and 1,600 feet) thick. This canyon on the western side, however, has reduced that thickness by about half. A study describing these findings is published in Geophysical Research Letters.

“Channels have started to be noted over the last 10 years, [but] their prevalence in Antarctic ice shelves has only recently been shown,” Dr Noel Gourmelen from the University of Edinburgh, the study’s lead author, told IFLScience.

The channel is up to 200 meters (650 feet) deep in places and runs the entire length of the Dotson ice shelf. It is getting deeper by about 7 meters (23 feet) each year and has caused notable crevassing at the surface. The whole shelf could melt through in 40 years, much quicker than the 170 years it would take if it was melting evenly.

From the surface, the sheet looks relatively flat. Gourmelen et al

The team thinks that these channels are being created by ocean circulation under the shelf, a process that has been sustained for at least 25 years. As Earth rotates, warm water about 1°C (34°F) in temperature cuts through the shelf, much quicker than if the melting was uniform.

“Melt from Dotson ice shelf results in 40 billion tonnes [44 billion US tons] of freshwater being poured into the Southern Ocean every year, and this canyon alone is responsible for the release of 4 billion tonnes [4.4 billion US tons] – a significant proportion,” Dr Gourmelen said in a statement.

“Since shelves are already suffering from thinning, these deepening canyons mean that fractures are likely to develop and the grounded ice upstream will flow faster than would be the case otherwise.”

While we don’t yet know the full extent of the problem, the signs aren’t great. It’s not clear how these canyons form, but it appears they are having a dramatic effect on the shelf – and this only adds to sea-level rise, as inland ice flows faster into the ocean.

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