Scientists have observed a starling sudden loss of ice in a previously stable area of Antarctica.
A team of researchers looked at measurements of the elevation of the Antarctic ice sheet taken by satellites over the Southern Antarctic Peninsula and found that around 2009, multiple glaciers in the region started to shed ice at a rate of 14.5 trillion gallons of water per year; no ice loss was observed in the years leading up to 2009, the University of Bristol reported. The findings suggest the region is now the second largest contributor to sea level rise in Antarctica. The data was collected using the European Space Agency's CryoSat-2 satellite.
"To date, the glaciers added roughly 300 cubic [kilometers] of water to the ocean. That's the equivalent of the volume of nearly 350,000 Empire State Buildings combined," said Bert Wouters, a Marie Curie Fellow at the University of Bristol, who lead the study.
The ice loss in the region is so severe that it causes small but detectable changes in Earth's gravitational field.
"The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us," Wouters said. "It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted."
The findings are especially puzzling because the change cannot be linked to variations in snowfall or air temperature. As an alternative, the researchers believe the phenomenon is a result of the warming oceans. These glaciers feed into ice shelves floating on the ocean surface, and they act as a buttress to the ice resting on inland bedrock that works to slow down the flow of glaciers into the ocean. Winds around Antarctica have been stronger in recent decades as a result of warmer climates and ozone depletion. These winds push warm waters from the Southern Ocean to the poles, where they melt the present glaciers.
The ice shelves have lost about one-fifth of their thickness over the past 20 years, which is reducing the amount of resisting force on the glaciers. This is concerning because the ice of the Southern Antarctic Peninsula rests on underwater bedrock, and if the glaciers retreat, the warm water could move inland and cause even more dramatic ice melts.
"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. 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," Wouters said. "To pinpoint the cause of the changes, more data need to be 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."
The findings were published in a recent edition of the journal Science.
