Antarctica is a truly massive continent. At over 5 million square miles, the whole of the US could fit securely within its borders. It boasts the highest, driest, coldest, and windiest landscape of all seven continents. And the fact that it is losing ice is nothing new. It's the rate at which parts of the continent are melting that is raising new concerns.
In a new study just published in the journal Science, a research team from the University of Bristol, in the UK, studied satellite data to measure glacier loss over the past 10 years. They keyed in on the Antarctic Peninsula, a craggy arm of the continent that juts from its northwest corner into the frigid waters of the Weddell Sea. And what they found were accelerating rates of loss along this poorly studied region.
"To date, the glaciers added roughly 300 cubic km of water to the ocean," says Bert Wouters, a Marie Curie Fellow at the University of Bristol and lead author of the study. "That's the equivalent of the volume of nearly 350,000 Empire State Buildings combined."
The team examined data collected from the European Space Agency's Cryosat 2 satellite, honing in on the Peninsula in order to gauge ice loss for that specific region. According to their data, the ice loss appeared stable until around 2009. But things have changed radically in the years since.
"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 says.
The team attributes the change, not to rising air temperatures or shifting weather patterns, but to warmer seas affecting submerged ice shelves that hold back larger glaciers. As the submerged shelves melt, the natural contours of the region funnel the glaciers into the seas. The cause of the warmer sea temperatures? Increased global warming.
The total contribution to sea level rise from Antarctic ice melt has recently been estimated at between 2.6 and 2.9 millimeters annually. But what is disconcerting to scientists is the percentage contribution from the Peninsula. The Bristol team's numbers show a yearly contribution of .16 millimeters from the Peninsula alone, totalling about 56 billion tons of ice melt annually - "a major fraction of Antarctica's total oceanic contribution."
"The fact that so many glaciers in such a large region suddenly started to lose ice came as a surprise to us. It shows a very fast response of the ice sheet: in just a few years the dynamic regime completely shifted."
Scientists continue to monitor the ever-shrinking continent.
"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."
