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Amictic
Amictic lakes are "perennially sealed off by ice, from most of the annual seasonal variations in temperature." Amictic lakes exhibit inverse cold water stratification 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 and wind. They are strongly tied with seasonality and thus associated with latitude and altitude. Amictic lakes occur in Arctic, Antarctic, and alpine regions and due to permanent ice-cover, these physical/thermal influences have a limited effect on circulation in the water column. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holomictic Lake
Holomictic lakes are lakes that have a uniform temperature and density from surface to bottom at a specific time during the year, which allows the lake waters to mix in the absence of stratification. Details Holomictic lakes mix at least occasionally, in contrast to meromictic lakes. Most lakes on Earth are holomictic; meromictic lakes are rare, although they may be less rare than commonly thought. Amictic lakes are sealed off by ice and never mix. There are four types of holomictic lakes: * Polymictic (mixing many times annually) * Cold Monomictic (mixing once annually; exhibiting negative stratification) * Warm Monomictic (mixing once annually; exhibiting positive stratification) * Dimictic (mixing twice annually) * Oligomictic (mixing less than once annually) See also * 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 atmos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymictic Lake
Polymictic lakes are holomictic lakes that are too shallow to develop thermal stratification; thus, their waters can mix from top to bottom throughout the ice-free period. Polymictic lakes can be divided into cold polymictic lakes (i.e., those that are ice-covered in winter), and warm polymictic lakes (i.e., polymictic lakes in regions where ice-cover does not develop in winter). While such lakes are well-mixed on average, during low-wind periods, weak and ephemeral stratification can often develop. See also * Amictic lake * Holomictic lake * Meromictic lake * Monomictic lake * Dimictic 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 External links "Circulation: annual patterns of dimictic lakes" at Encyclopædia Britannica Online Lakes by t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 holomictic, a category which includes all lakes which mix one or more times per year. During winter, dimictic lakes are covered by a layer of ice, creating a cold layer at the surface, a slightly warmer layer beneath the ice, and a still-warmer unfrozen bottom layer, while during summer, the same temperature-derived density differences separate the warm surface waters (the epilimnion), from the colder bottom waters (the hypolimnion). In the spring and fall, these temperature differences briefly disappear, and the body of water overturns and circulates from top to bottom. Such lakes are common in mid-latitude regions with temperate climates. Examples of dimictic lakes * Lake Mendota * Lake Superior * Lake Simcoe * Opeongo Lake, Lake Opeongo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Stratification
Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers, the Epilimnion comprising the top warm layer, the thermocline (or Metalimnion): the middle layer, which may change depth throughout the day, and the colder Hypolimnion extending to the floor of the lake. Definition The thermal stratification of lakes refers to a change in the temperature at different depths in the lake, and is due to the density of water varying with temperature. Cold water is denser than warm water and the epilimnion generally consists of water that is not as dense as the water in the hypolimnion. However, the temperature of maximum density for freshwater is 4 °C. In Temperate climate, temperate regions where lake water warms up and cools through the seasons, a cyclical pattern of overturn occurs that is repeated from year to year as the cold dense water at the top of the lake sinks (see stab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Bonney (Antarctica)
Lake Bonney ( ) is a saline lake with permanent ice cover at the western end of Taylor Valley in the McMurdo Dry Valleys of Victoria Land, Antarctica. It is long and up to wide. A narrow channel only wide (''Lake Bonney at Narrows'') separates the lake into ''East Lake Bonney'' () and ''West Lake Bonney'' (). To the north and south of the lake lie peaks that are over above sea level, and the Taylor Glacier is positioned to the west of the lake. It is deep and is perpetually trapped under of ice. It was first visited by the British National Antarctic Expedition of 1901-1904. It was named by the Robert Falcon Scott expedition of 1910-1913, for Thomas George Bonney, professor of geology at University College London, England from 1877 to 1901. Lake Bonney is one of the main lakes studied by the National Science Foundations, McMurdo Long Term Ecological Research site. Starting in 2007 NASA is funding an autonomous submersible robot called ENDURANCE to explore the water vo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 throughout much of the year. During their brief "summer", the surface waters remain at or below 4 °C. The ice prevents these lakes from mixing in winter. During summer, these lakes lack significant thermal stratification, and they mix thoroughly from top to bottom. These lakes are typical of cold-climate regions (e.g. much of the Arctic). An example of a cold monomictic lake is Great Bear Lake in Canada. Warm monomictic lakes Warm monomictic lakes are lakes that never freeze, and are thermally stratified throughout much of the year. The density difference between the warm surface waters (the epilimnion) and the colder bottom waters (the hypolimnion) prevents these lakes from mixing in summer. During winter, the surface waters cool to a te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Austrian Ingo Findenegg in 1935, apparently based on the older word ''holomictic''. The concepts and terminology used in describing meromictic lakes were essentially complete following some additions by G. Evelyn Hutchinson in 1937. Characteristics Most lakes are ''holomictic''; that is, at least once per year, physical mixing occurs between the surface and the deep waters. In so-called monomictic lakes, the mixing occurs once per year; in dimictic lakes, the mixing occurs twice a year (typically spring and autumn), and in polymictic lakes, the mixing occurs several times a year. In meromictic lakes, however, the layers of the lake water can remain unmixed for years, decades, or centuries. Meromictic lakes can usually be divided into th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 central East Antarctic Ice Sheet, which is at above mean sea level. The surface of this fresh water lake is approximately under the surface of the ice, which places it at approximately below sea level. Measuring long by wide at its widest point, it covers an area of making it the 16th largest lake by surface area. With an average depth of , it has an estimated volume of , making it the 6th largest lake by volume. The lake is divided into two deep basins by a ridge. The liquid water depth over the ridge is about , compared to roughly deep in the northern basin and deep in the southern. The lake is named after Vostok Station, which in turn is named after the ''Vostok'' (Восток), a sloop-of-war, which means "East" in Russian. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. It was discovered by Captain James Clark Ross in January 1841 and named after Queen Victoria. The rocky promontory of Minna Bluff is often regarded as the southernmost point of Victoria Land, and separates the Scott Coast to the north from the Hillary Coast of the Ross Dependency to the south. The region includes ranges of the Transantarctic Mountains and the McMurdo Dry Valleys (the highest point being Mount Abbott in the Northern Foothills), and the flatlands known as the Labyrinth. The Mount Melbourne is an active volcano in Victoria Land. Early explorers of Victoria Land include James Clark Ross and Douglas Mawson. In 1979, scientists discovered a group of 309 meteorites in Antarctica, some of which were found near the Allan Hills in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eastern Antarctica
East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almost entirely within the Eastern Hemisphere and its name has been accepted for more than a century. It is generally higher than West Antarctica and includes the Gamburtsev Mountain Range in the center. The geographic South Pole is located within East Antarctica. Apart from small areas of the coast, East Antarctica is permanently covered by ice and it has relatively low biodiversity, with only a small number of species of terrestrial plants, animals, algae, and lichens. The coasts are the breeding ground for various seabirds and penguins, and the leopard seal, Weddell seal, elephant seal, crabeater seal and Ross seal breed on the surrounding pack ice in summer. Location and description Almost completely covered in thick, permanent ice, East A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Ecosystem
A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems (''lentic'' refers to stationary or relatively still freshwater, from the Latin ''lentus'', which means "sluggish"), which include ponds, lakes and wetlands, and much of this article applies to lentic ecosystems in general. Lentic ecosystems can be compared with lotic ecosystems, which involve flowing terrestrial waters such as rivers and streams. Together, these two ecosystems are examples of freshwater ecosystems. Lentic systems are diverse, ranging from a small, temporary rainwater pool a few inches deep to Lake Baikal, which has a maximum depth of 1642 m. The general distinction between pools/ponds and lakes is vague, but Brown states that ponds and pools have their entire bottom surfaces exposed to light, while lakes do not. In addition, some lakes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 salinity more than ten times that of seawater and more than the salinity of the Dead Sea. Lake Vanda is also meromictic, which means that the deeper waters of the lake don't mix with the shallower waters. There are three distinct layers of water ranging in temperature from on the bottom to the middle layer of and the upper layer ranges from . It is only one of the many saline lakes in the ice-free valleys of the Transantarctic Mountains. The longest river of Antarctica, Onyx River, flows west, inland, into Lake Vanda. There is a meteorological station at the mouth of the river. The lake is covered by a transparent ice sheet year-round, though melting in late December forms a moat out to approximately from the shore. The surface of the ice i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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