Amictic lakes are "perennially sealed off by ice, from most of the annual seasonal variations in temperature."
Amictic lakes exhibit inverse cold water
stratification
Stratification may refer to:
Mathematics
* Stratification (mathematics), any consistent assignment of numbers to predicate symbols
* Data stratification in statistics
Earth sciences
* Stable and unstable stratification
* Stratification, or st ...
whereby water temperature increases with depth below the ice surface 0 °C (less-dense) up to a theoretical maximum of 4 °C (at which the density of water is highest).
Hutchinson–Löffler (1956)
classified amictic and other types of lakes based on physical/thermal processes.
[ ] These processes are influenced by
solar radiation
Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument.
Solar irradiance is measured in watts per square metre ( ...
and
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...
. They are strongly tied with seasonality and thus associated with latitude and altitude. Amictic lakes occur in
Arctic
The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), Finland, Iceland, N ...
,
Antarctic, and alpine regions and due to permanent ice-cover, these physical/thermal influences have a limited effect on circulation in the
water column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
. For this reason, amictic lakes are commonly referred to as lakes that ''never'' mix.
''"Mixing"'' in this context, however, refers to homogenization of the water column and so the term ''"amictic"'' is not meant to imply that the lake water is stagnant.
With the rare exception of lakes near the edges of the permanent icecaps in
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...
and
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
, amictic lakes do experience melting around the lake's perimeter during summer, resulting in a "moat" of water surrounding a thick pan of ice that remains in the centre of the lake. This melting occurs as a result of heat absorbed by water and sediments below the ice, particularly in the shallow-water areas, when snow does not cover the ice, and also by heat flow and
meltwater runoff from the surrounding land. Mixing below the ice occurs due to density currents generated by heat from direct solar radiation and from meltwater runoff which may differ in density from the lake water due to both temperature and
suspended sediment content, depending on its source and flow path. Despite these processes, the effects of wind at the lake surface are highly reduced due to the ice cover, and so vertical mixing of the water column may be incomplete. This may result in anoxic conditions, which has implications for biogeochemical processes within the lake.
List of amictic lakes
Antarctica
*
Lake Vanda
Lake Vanda is a lake in Wright Valley, Victoria Land, Ross Dependency, Antarctica. The lake is long and has a maximum depth of . On its shore, New Zealand maintained Vanda Station from 1968 to 1995. Lake Vanda is a hypersaline lake with a salin ...
in
Eastern Antarctica
*
Lake Bonney in
Victoria Land
Victoria Land is a region in eastern Antarctica which fronts the western side of the Ross Sea and the Ross Ice Shelf, extending southward from about 70°30'S to 78°00'S, and westward from the Ross Sea to the edge of the Antarctic Plateau. I ...
*
Lake Vostok
Lake Vostok (russian: озеро Восток, ''ozero Vostok'') is the largest of Antarctica's almost 400 known subglacial lakes.
Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the cen ...
in
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
See also
*
Dimictic lake
A dimictic lake is a body of freshwater whose difference in temperature between surface and bottom layers becomes negligible twice per year, allowing all strata of the lake's water to circulate vertically. All dimictic lakes are also considered ho ...
*
Holomictic lake
*
Meromictic lake
A meromictic lake is a lake which has layers of water that do not intermix. In ordinary, holomictic lakes, at least once each year, there is a physical mixing of the surface and the deep waters.
The term ''meromictic'' was coined by the Austr ...
*
Monomictic lake
Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into cold and warm types.
Cold monomictic lakes
Cold monomictic lakes are lakes that are covered by ice thro ...
*
Polymictic lake
*
Thermocline
A thermocline (also known as the thermal layer or the metalimnion in lakes) is a thin but distinct layer in a large body of fluid (e.g. water, as in an ocean or lake; or air, e.g. an atmosphere) in which temperature changes more drastically with ...
References
{{reflist
Lakes by type