Lakes, Ponds and Pools

Saline lakes may also arise by the evaporation of seawater, trapped in arms of the sea cut off by the rising of the land, as the deglaciation reduced the load of the ice sheet. Even in very salty water there may be some life in the form of algae, flagellates and bacteria. In some saline lakes a layer of freshwater floats on top of the denser saline layer beneath. If there is a thick ice cover on top, this will insulate the liquid layers from the cold air above and some of these lakes are warmed by solar radiation or geothermal heat to reach temperatures near the bottom as high as 35C.

In a lake of this type, for example Lake Bonney in South Victoria Land (in the McMurdo Dry Valleys), extensive algal mats occur attached to the gravel bottom. These mats grow and produce gases which render them buoyant. They detach in pieces and rise through the water to positions underneath the ice. Here the algal mats slowly collect solar heat and melt their way upwards through the ice which is 3-4 metres thick on Lake Bonney. When they reach the surface the mat pieces dry and blow away, sometimes colonizing other locations.

Lake Bonney was among the first lakes discovered on the Antarctic continent. Scott in 1903 first observed this lake and described two nearly separate small basins. In 1912, Scott's second expedition discovered that the two lobes had joined more completely and the lake had apparently enlarged. Today, Lake Bonney continues to grow, as do other lakes in this Dry Valley region.

A strange type of lake occurs on land adjacent to ice shelves. In these lakes the outflow has been dammed by the ice of the shelf, so that the lower layers of the lake on the seaward side are in contact with the sea under the ice shelf and the lake surface rises and falls with the tide. Permanent ice cover prevents wind-generated turbulence from mixing the layers. In such a lake a freshwater community in the upper layer may overlie a marine community beneath.

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Glossary

Ice Shelves
Websites

 • Ice Shelves
Facts about ice shelves.
 • Ice cores and climate change
An explanation as to how our climate has changed over the years and how ice cores show us that record.
 • Obtaining information from ice cores
A description of the information that can be obtained from ice cores.
 • Dating a core
An explanation of how we can date ice cores when the layers in ice cores are not usually visible.
 • Antarctic Adventure 1997
Information on the geography and climate of Antarctica.
 • Meteorology
A general description of the climate of Antarctica.
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