Melting glaciers, fast-disappearing gauge of climate change

A crack widens in the San Rafael glacier in Chile's extreme south, and a ten-storey iceberg crashes into the lake by the same name -- a dramatic reminder of the impacts of global warming.

In the lake San Rafael, about 100 icebergs float today, pieces broken off from the glacier that 150 years ago stretched out over two-thirds of the body of water now free of ice cover.

The San Rafael glacier is one of 39 in the Northern Patagonian Ice Field (3,500 square kilometres or 1,350 square miles), which with the Southern Patagonian Ice Field (11,000 km2) in Chile's Aysen region forms one of the world's biggest ice masses.

According to the European Space Agency satellite images show San Rafael to be one of the world's most actively calving glaciers and the fastest-moving in Patagonia, "flowing" at a speed of about 7.6 kilometres (4.7 miles) per year -- "receding dramatically under the influence of global warming."

Glaciers are bodies of slowly-moving ice on land that can be several hundred or several thousand years old.

Seasonal glacier melt is a natural phenomenon that with global warming has accelerated "significantly," Jorge O'Kuinghttons, a regional head of glaciology at Chile's water directorate, said.

At the moment, Patagonia's glaciers are retreating faster than anywhere else in the world.

"Glaciers are an excellent indicator of climate change," said Alexis Segovia, another government glaciologist who works in the remote region of southern Chile.  

All but two of Chile's 26,000 glaciers are shrinking, he said, due to rising temperatures caused by manmade greenhouse gas emissions.

It is a vicious cycle. 

Ice-covered surfaces of Earth reflect excess heat back into space, and if these are reduced through melting, temperatures rise even more.