Scientists have identified sudden and unrelenting ice loss in the Southern Antarctic Peninsula, shifting the region from a stable area to Antarctica’s second largest contributor of sea level rise.
The highly concerning findings, published today in the journal Science, show that up until 2009 the region was stable, but since then ice has been shed into the ocean at a rate of 60 cubic km – 55 trillion litres of water – every year, and there is no sign of it letting up.
“To date, the glaciers added roughly 300 cubic km of water to the ocean. That’s the equivalent of the volume of nearly 350,000 Empire State Buildings combined,” explained Dr Bert Wouters, study lead author and a Marie Curie fellow at the UK’s University of Bristol.
The cause for this ice loss is, according to the researchers, warming oceanic temperatures, which themselves are a result of the depletion of the ozone layer and climate change.
Not only is the scale of the ice loss significantly contributing to global sea level rise, but it is causing minor changes to the Earth’s gravity field, according to measurements by the Gravity Recovery and Climate Experiment (GRACE).
The findings have come as a shock to the scientists, due to the previous stability of the ice sheet in this area.
“The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us,” said Wouters. “It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted.”
Over the last few decades, a warming climate has resulted in stronger and more aggressive westerly winds around Antarctica, which have pushed the Southern Ocean’s warm waters towards the pole.
The scientists believe that six years ago the ice sheet passed a critical point that resulted in the ice loss, as a result of these warm waters depleting the floating ice shelves from below.
“It appears that sometime around 2009, the ice shelf thinning and the subsurface melting of the glaciers passed a critical threshold which triggered the sudden ice loss,” explained Wouters.
“However, compared to other regions in Antarctica, the Southern Peninsula is rather understudied, exactly because it did not show any changes in the past, ironically.”
The changes were observed using a European Space Agency satellite, the CryoSat-2, which is designed to sense ice remotely.
Located 700km above the Earth’s surface, the satellite sends a radar pulse to the ice, which reflects it back to detectors on the satellite. By measuring the time the pulse takes to travel, the scientists are able to precisely determine the elevation of the ice surface and detect how much of it had been lost.
The measurements, which spanned over half a decade, showed that some areas of the glaciers were dropping by a whopping 4m every year.
However, there is no indication at present that the ice loss will stop any time soon.
A large portion of the ice is located on bedrock below the sea level, which deepens further inland, and there are fears that the warm water will continue to move inland, increasing the area that has melted.
To know for sure, the scientists plan to up the research so that far more data is collected.
“A detailed knowledge of the geometry of the local ice shelves, the ocean floor topography, ice sheet thickness and glacier flow speeds are crucial to tell how much longer the thinning will continue,” added Wouters.