Monday, August 31, 2009

Gigatons of Ice

While we all know that global warming is accelerating, this article has some nice imagery.

The glaciers of Greenland are the fat, restless fingers of its vast ice sheet, constantly moving, stretching down into fjords and pushing ice from the sheet into the ocean, in the form of melt water and icebergs.

Before their first expedition, [glacier scientists] Hamilton and his colleague Leigh Stearns, from the University of Kansas, used satellite data to plan exactly where they would land on a glacier.

"When we arrived there was no glacier to be seen. It was way up the fjord," he says. "We thought we'd made some stupid goof with the co-ordinates, but we were where we were supposed to be." It was the glacier that was in the wrong place. A vast expanse had melted away.

When Hamilton and Stearns processed their first measurements of the glacier's speed, they thought they had made another mistake. They found it was marching forwards at a greater pace than a glacier had ever been observed to flow before. "We were blown away because we realised that the glaciers had accelerated not just by a little bit but by a lot," he says. The three glaciers they studied had abruptly increased the speed by which they were transmitting ice from the ice sheet into the ocean....

Driven by the loss of ice, Arctic temperatures are warming more quickly than other parts of the world: last autumn air temperatures in the Arctic stood at a record 5C above normal. For centuries, the ice sheets maintained an equilibrium: glaciers calved off icebergs and sent melt water into the oceans every summer; in winter, the ice sheet was then replenished with more frozen snow. Scientists believe the world's great ice sheets will not completely disappear for many more centuries, but the Greenland ice sheet is now shedding more ice than it is accumulating.

The melting has been recorded since 1979; scientists put the annual net loss of ice and water from the ice sheet at 300-400 gigatonnes (equivalent to a billion elephants being dropped in the ocean), which could hasten a sea level rise of catastrophic proportions.

As Hamilton has found, Greenland's glaciers have increased the speed at which they shift ice from the sheet into the ocean. Helheim, an enormous tower of ice that calves into Sermilik Fjord, used to move at 7km (4.4 miles) a year. In 2005, in less than a year, it speeded up to nearly 12km a year. Kangerdlugssuaq, another glacier that Hamilton measured, tripled its speed between 1988 and 2005. Its movement – an inch every minute – could be seen with the naked eye. |The Sermilik fjord in Greenland: a chilling view of a warming world - Guardian|(emphasis added)

What will we call Iceland after all the glaciers melt?

1 comment:

Language Lover said...

Speaking of nice imagery, check this out: