Melt ponds

Melt ponds are pools of open water that form on sea ice in the warmer months of spring and summer. The ponds are also found on glacial ice and ice shelfs. Ponds of melted water can also develop under the ice.

Melt ponds are usually darker than the surrounding ice. The distribution and size of melt ponds is highly variable.

These ponds absorb the sun's energy, rather than reflecting it as ice does, thereby having a significant influence on Earth's radiation balance. This differential, which has not been scientifically investigated until recently, has a large effect on the rate of ice melting and the extent of ice cover. [cite web | title = Scientists use Satellite to "Pond-er" Melted Artic Ice | publisher = NASA | date = 2 October, 2003 | url = http://www.nasa.gov/centers/goddard/news/topstory/2003/0918meltwater.html | accessdate=2008-01-01]

Melt ponds can melt through to the ocean's surface. [cite web |url=http://www.crrel.usace.army.mil/sid/perovich/SHEBAice/meltpond.htm |title=Melt ponds |accessdate=2008-01-01 |format= |work= ] Salt water entering the pond, increases the melt rate because the salty water is warmer than the fresh water of the pond.

Water from melt ponds over the surface can run into crevasses or "moulin" (tubes leading under ice sheets or glaciers), turning into meltwater. The water may reach the underlying rock. The effect is an increase in the rate of ice flow to the oceans, as the fluid behaves like a lubricant in the basal sliding of glaciers. [cite web |url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17607 |title=Melt Ponds on Greenland's Ice Cap |accessdate=2008-01-01 |format= |work= ]

Effects of Melt Ponds

The effects of melt ponds are diverse. Research by Ted Scambos, from the National Snow and Ice Data Center has supported the melt water fracturing theory, that suggests the melting process associated with melt ponds has a substantial affect on ice shelf disintegration. [cite web |url=http://nsidc.org/iceshelves/larsenb2002/ |title=Larsen B Ice Shelf Collapses in Antarctica |accessdate=2008-01-01 |format= |work= ] Seasonal melt ponded and penetrating under glaciers shows seasonal acceleration and deceleration of ice flows affecting whole icesheets. [ [http://www.sciencemag.org/cgi/content/abstract/297/5579/218 Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow] Originally published in Science Express on 6 June 2002, Science 12 July 2002: Vol. 297. no. 5579, pp. 218 - 222.] Accumulated changes by ponding on ice sheets appear in the earthquake record of Greenland and other glaciers [ [http://www.news.harvard.edu/gazette/2006/04.06/05-ekstrom.html Global warming yields 'glacial earthquakes' in polar areas] ] : "Quakes ranged from six to 15 per year from 1993 to 2002, then jumped to 20 in 2003, 23 in 2004, and 32 in the first 10 months of 2005." [ [http://environment.newscientist.com/article/dn8889.html Glacial earthquakes rock Greenland ice sheet] 12:36 24 March 2006, NewScientist.com news service] Ponding in the extreme is lakes and lakes in association with glaciers are examined in the particular case of the Missoula Floods.

See also

* Moulin (geology)
* Glacier ice accumulation
* Polar ice packs

References