Rapid melting recorded at world’s largest ice shelf

Part of the world’s largest ice shelf is melting 10 times faster than expected due to the sea warming around it, research shows.

The discovery suggests that the Ross Ice Shelf, a floating slab of Antarctic ice the size of France which juts into the ocean, is more vulnerable to global warming than previously thought.

Loss of ice shelves removes a barrier to glaciers transporting water to the ocean, allowing sea levels to rise.

A team from Cambridge University spent several years investigating how the Ross Ice Shelf’s north-west sector interacted with the ocean beneath it.

Former Cambridge scientist Dr Craig Stewart, now at the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, said: “The stability of ice shelves is generally thought to be related to their exposure to warm deep ocean water, but we’ve found that solar heated surface water also plays a crucial role in melting ice shelves.”

The team took measurements of temperature, salinity, melt rate and ocean currents using instruments passed through a 260-metre (850ft) borehole.

Four years’ worth of data were also collected from an oceanographic mooring installed under the ice shelf.

In addition, a custom-made radar system was employed to survey the changing thickness of the ice.

The instruments showed that surface water heated by the sun flowed into the cavity under the ice shelf, causing melt rates almost to triple in the summer.

Dr Stewart added: “Climate change is likely to result in less sea ice, and higher surface ocean temperatures in the Ross Sea, suggesting that melt rates in this region will increase in the future.”

The findings are published in the latest issue of the journal Nature Geoscience.

Co-author Dr Poul Christoffersen, from Cambridge University’s Scott Polar Research Institute, pointed out that collapsing ice shelves can double or triple the speed at which glaciers flow to the ocean.

“The difference here is the sheer size of the Ross Ice Shelf, which is over 100 times larger than the ice shelves we’ve already seen disappear,” he said.

“The observations we made at the front of the ice shelf have direct implications for many large glaciers that flow into the ice shelf, some as far as 900 kilometres (559 miles) away.”