The climatic snow line is the boundary between a

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

-covered and snow-free surface. The actual snow line may adjust seasonally, and be either significantly higher in elevation, or lower. The permanent snow line is the level above which snow will lie all year.

Background

Snow line is an umbrella term for different interpretations of the boundary between

-covered surface and snow-free surface. The definitions of the snow line may have different temporal and spatial focus. In many regions the changing snow line reflect

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's axial tilt, tilted orbit around the Sun. In temperat ...

al dynamics. The final height of the snow line in a

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher t ...

environment at the end of the melting season is subject to climatic variability, and therefore may be different from year to year. The snow line is measured using automatic cameras,

aerial photograph Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other airborne platforms. When taking motion pictures, it is also known as aerial videography. Platforms for aerial photography include fixed-wing ai ...

s, or

satellite image Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell i ...

s. Because the snow line can be established without on-the-ground measurements, it can be measured in remote and difficult to access areas. Therefore, the snow line has become an important variable in hydrological models. The average elevation of a transient snow line is called the "climatic snow line" and is used as a parameter to classify regions according to climatic conditions. The boundary between the accumulation zone and the ablation zone on

glacier 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 ...

s is called the "annual snow line". The glacier region below this snow line was subject to melting in the previous season. The term "orographic snow line" is used to describe the snow boundary on surfaces other than glaciers. The term "regional snow line" is used to describe large areas. The "permanent snow line" is the level above which snow will lie all year.

Snow lines of global regions

The interplay of

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

and

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

affects the precise placement of the snow line at a particular location. At or near the

equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

, it is typically situated at approximately above

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

. As one moves towards the

Tropic of Cancer The Tropic of Cancer, also known as the Northern Tropic, is the Earth's northernmost circle of latitude where the Sun can be seen directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun ...

and

Tropic of Capricorn The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reach ...

, the parameter at first increases: in the

Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...

the permanent snow line can be as high as . Beyond the

Tropics The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

, the snow line becomes progressively lower as the latitude increases, to just below in the

Alps The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia. ...

and falling all the way to sea level itself at the

ice cap In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Description By definition, ice caps are not constrained by topogra ...

s near the

poles Pole or poles may refer to: People *Poles (people), another term for Polish people, from the country of Poland * Pole (surname), including a list of people with the name * Pole (musician) (Stefan Betke, born 1967), German electronic music artist ...

Scetch showing the actual elevation of the Snow Line in different Latitudes by Alexander Keith Johnston 1848

In addition, the relative location to the nearest coastline can influence the elevation of the snow line. Areas near a coast might have a lower snow line than areas of the same elevation and latitude situated in a

landmass A landmass, or land mass, is a large region or area of land that is in one piece and not noticeably broken up by oceans. The term is often used to refer to lands surrounded by an ocean or sea, such as a continent or a large island. In the fiel ...

interior due to more winter snowfall and because the average summer

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

of the surrounding lowlands would be warmer away from the sea. (This applies even in the tropics, since areas far from the sea will have larger diurnal temperature ranges and potentially less moisture, as observed with

Kilimanjaro Mount Kilimanjaro () is a dormant volcano in Tanzania. It is the highest mountain in Africa and the highest free-standing mountain above sea level in the world, at above sea level and above its plateau base. It is also the highest volcano i ...

and presently glacier-free

Mount Meru Mount Meru (Sanskrit/Pali: मेरु)—also known as Sumeru, Sineru or Mahāmeru—is a sacred, five-peaked mountain present within Hindu, Jain and Buddhist cosmologies, revered as the centre of all physical, metaphysical and spiritua ...

.) A higher elevation is therefore necessary to lower the temperature further against the surroundings and keep the snow from melting. Furthermore, large-scale oceanic currents such as the

North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward. Characteristics The NAC ...

can have significant effects over large areas (in this case warming northern Europe, extending even to some Arctic Ocean regions). In the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

the snow line on the north-facing slopes is at a lower elevation, as the north-facing slopes receive less sunlight (

solar irradiance 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 ( ...

) than south-facing slopes. The converse will occur in the Southern Hemisphere.

Glacier equilibrium line

The glacier

equilibrium Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibr ...

line is the point of transition between the

accumulation zone On a glacier, the accumulation zone is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation, ( melting, evaporation, and sublimation). The annual equilibrium line separates the accumulation and ablation ...

and

ablation zone Ablation zone or ''ablation area'' refers to the low-altitude area of a glacier or ice sheet below firn with a net loss in ice mass. This loss can result from melting, sublimation, evaporation, ice calving, aeolian processes like blowing snow, ...

. It is the line where the mass of these two zones is equal. Depending on the thickness of the glacier, this line can seem as though it is leaning more towards one zone but it is determined by the actual mass of ice in either zone. The rates of

ablation Ablation ( – removal) is the removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes, or by other means. Examples of ablative materials are described below, including spacecraft material for as ...

and accumulation can also be used to determine the location of this line. This point is an important location to use in determining whether a glacier is growing or shrinking. A higher glacier equilibrium line will indicate that the glacier is shrinking, whereas a lower line will indicate that the glacier is growing. The terminus of a glacier advances or retreats based on the location of this equilibrium line. Scientists are using

remote sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

to better estimate the locations of this line on glaciers around the world. Using

satellite imagery Satellite images (also Earth observation imagery, spaceborne photography, or simply satellite photo) are images of Earth collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell im ...

, scientists are able to identify whether the glacier is growing or receding. This is a very helpful tool for analyzing glaciers that are difficult to access. Using this

technology Technology is the application of Conceptual model, conceptual knowledge to achieve practical goals, especially in a reproducible way. The word ''technology'' can also mean the products resulting from such efforts, including both tangible too ...

we can better gauge the

effects of climate change Effects of climate change are well documented and growing for Earth's natural environment and human societies. Changes to the climate system include an Instrumental temperature record, overall warming trend, Effects of climate change on the ...

on glaciers around the world.

Records

The highest mountain in the world below the snow line is

Ojos del Salado Nevado Ojos del Salado is a Dormant volcano, dormant complex volcano in the Andes on the Argentina–Chile border. It is the highest volcano on Earth and the highest peak in Chile. The upper reaches of Ojos del Salado consist of several overlapp ...

.Regional Climate and Snow/Glacier Distribution in Southern Upper Atacama (Ojos del Salado) – an integrated statistical, GIS and RS based approach
/ref>

References

*Charlesworth J.K. (1957). The quaternary era. With special reference to its glaciation, vol. I. London, Edward Arnold (publishers) Ltd, 700 pp. *Flint, R. F. (1957). Glacial and Pleistocene geology. John Wiley & Sons, Inc., New York, xiii+553+555 pp. *Kalesnik, S.V. (1939). Obshchaya glyatsiologiya eneral glaciology Uchpedgiz, Leningrad, 328 pp. (in Russian) *Tronov, M.V. (1956). Voprosy svyazi mezhdu klimatom i oledeneniem he problems of the connection between climate and glaciation Izdatel'stvo Tomskogo Universiteta, Tomsk, 202 pp. (in Russian) *Wilhelm, F. (1975). Schnee- und Gletscherkunde now- and glaciers study De Gruyter, Berlin, 414 pp. (in German) *Braithewaite, R.J. and Raper, S.C.B (2009). "Estimating Equilibrium Line Altitude (ELA) From Glacier Inventory Data." ''Annals of Glaciology'', 50, pp. 127–132. . *Leonard, K.C., and Fountain, A.G. (2003). "Map-Based Methods for Estimating Glacier Equilibrium-Line Altitudes." ''Journal of Glaciology'', vol. 49, no. 166, pp. 329–336., . *Ohmura, A., Kasser, P., and Funk, M. (1992). "Climate at the Equilibrium Line of Glaciers." ''Journal of Glaciology'', vol. 38, no. 130, pp. 397–411., . *Carrivick, J.L., Lee, J. and Brewer, T.R. (2004). "Improving Local Estimations and Regional Trends of Glacier Equilibrium Line Altitudes." ''Geografiska Annaler: Series A, Physical Geography'', vol. 86, no. 1, pp. 67–79. . *Benn, D.I., and Lehmkuhl, F. (2000). "Mass balance and equilibrium-line altitudes of glaciers in high-mountain environments." ''Quaternary International'', 65/66, pp. 15–29.

Footnotes

{{reflist Snow Snow or ice weather phenomena Climate zones Montane ecology