Melt pond

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 shelves. 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 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.^[1]

Melt ponds can melt through to the ocean's surface.^[2] Seawater 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.

Water from melt ponds over land surface can run into crevasses or moulins – 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.^[3]