Melt ponds are pools of open water that form on

sea ice Sea ice arises as seawater freezes. Because ice is less density, dense than water, it floats on the ocean's surface (as does fresh water ice). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world' ...

in the warmer months of spring and summer. The ponds are also found on

glacial A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

ice and

ice shelves An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to Displacement (fluid), displace the more dense surround ...

. Ponds of melted water can also develop under the ice, which may lead to the formation of thin underwater ice layers called false bottoms. Melt ponds are usually darker than the surrounding ice, and their distribution and size is highly variable. They absorb

solar radiation Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible light perceptible to the human eye as well as invisible infrared (typically p ...

rather than reflecting it as ice does and, thereby, have a significant influence on Earth's radiation balance. This differential, which had not been scientifically investigated until recently, has a large effect on the rate of ice melting and the extent of ice cover. Melt ponds can melt through to the ocean's surface.

Seawater Seawater, or sea water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximat ...

entering the pond increases the melt rate because the salty water of the ocean is warmer than the fresh water of the pond. The increase in salinity also depresses the water's

freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

. Water from melt ponds over land surface can run into

crevasse A crevasse is a deep crack that forms in a glacier or ice sheet. Crevasses form as a result of the movement and resulting stress associated with the shear stress generated when two semi-rigid pieces above a plastic substrate have different rate ...

s or moulins – tubes leading under ice sheets or glaciers – turning into

meltwater Meltwater (or melt water) is water released by the melting of snow or ice, including glaciers, glacial ice, tabular icebergs and ice shelf, ice shelves over oceans. Meltwater is often found during early spring (season), spring when snow packs a ...

. 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 A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, ...

in the basal sliding of glaciers.

Effects of melt ponds

The effects of melt ponds are diverse (this subsection refers to melt ponds on ice sheets and ice shelves). Research by Ted Scambos, of the

National Snow and Ice Data Center The National Snow and Ice Data Center (NSIDC) is a United States information and referral center in support of polar and cryospheric research. NSIDC archives and distributes digital and analog snow and ice data and also maintains information ab ...

, has supported the melt water fracturing theory that suggests the melting process associated with melt ponds has a substantial effect on ice shelf disintegration. Seasonal melt ponded and penetrating under glaciers shows seasonal acceleration and deceleration of ice flows affecting whole icesheets. Accumulated changes by ponding on ice sheets appear in the earthquake record of Greenland and other glaciers: "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."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. File:Sea Ice MeltPonds.png, File:Greenland Ilulissat.jpg,

References

{{pond Climatology Earth phenomena Ponds Sea ice

Effects of melt ponds

See also

References