From Wikipedia, the free encyclopedia
Main article:
gives off , resulting in this
snowmelt pattern.
In , snowmelt is
produced from melting . It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual
in many parts of the world, in some cases contributing high fractions of the annual runoff in a watershed. Predicting snowmelt runoff from a
may be a part of designing water control projects. Rapid snowmelt can cause . If the snowmelt is then frozen, very dangerous conditions and accidents can occur, introducing the need for
to melt the .
Sorry, your browser either has JavaScript disabled or does not have any supported player.
to play the clip in your browser.
Snowmelt flowing into lake at Okanagan Mountain Provincial Park
There are several energy fluxes involved in the melting of snow. These fluxes can act in opposing directions, that is either delivering heat to or removing heat from the . Ground heat flux is the energy delivered to the snowpack from the soil below by conduction. Radiation inputs to the snowpack include net
(solar radiation including visible and ultraviolet light) and longwave () radiation. Net shortwave radiation is the difference in energy received from the sun and that reflected by the snowpack because of the snowpack . Longwave radiation is received by the snowpack from many sources, including ozone, carbon dioxide, and water vapor present in all levels of the atmosphere. Longwave radiation is also emitted by the snowpack in the form near-, where snow has an emissivity between 0.97 and 1.0. Generally the net longwave radiation term is negative, meaning a net loss of energy from the snowpack. Latent heat flux is the energy removed from or delivered to the snowpack which accompanies the mass transfers of , , or . Sensible heat flux is the heat flux due to
between the air and snowpack.
In northern Alaska, the melt-date has advanced by 8 days since the mid-1960s. Decreased snowfall in winter followed by warmer spring conditions seems to be the cause for the advance. In Europe, the recent heat wave has especially been anomalous at higher altitudes. For the first time on record, some of the highest Alpine peaks in Europe are snow-free. Although it would seem that the two are related, the question of how much of this is due to climate change firmly remains a center of debate.
Increased water runoff due to snowmelt was a cause of many famous floods. One well-known example is the
of 1997, when the
flooded. Flooding in the Red River Valley is augmented by the fact that the river flows north through
and into . As snow in , , and
begins to melt and flow into the Red River, the presence of downstream ice can act as a dam and force upstream water to rise. Colder temperatures downstream can also potentially lead to freezing of water as it flows north, thus augmenting the ice dam problem. Some areas in
are also prone to snowmelt flooding as well.
The date of annual melt is of great interest as a potential indicator of climate change. In order to determine whether the earlier disappearance of spring snow cover in northern Alaska is related to global warming versus an appearance of a more natural, continual cycle of the climate, further study and monitoring is necessary.
Large year-to-year variability complicates the picture and furthers the debate. Inter-annual variability of springtime snow pack comes largely from variability of winter month precipitation which is in turn related to the variability of key patterns of atmospheric circulation.
A study of the mountains in the western United States show a region wide decline in spring snow-pack since the mid-1900s, dominated by loss at low elevations where winter temperatures are near freezing. These losses are an indication of increased temperatures which lead to snow loss via some combination of increased regularity of rain versus snow and increased melting during winter months. These natural variations make it challenging to quantify trends with confidence, to deduce observed changes to predict future climate, or to clearly detect changes in snow-pack due to human impact on warming trends.
Gray, D.M., Male, D. H. (1981). . Pergamon Press.  .
. (1969). "Radiation in the Atmosphere". Inter. Geophys. Ser. 12.
Stone, Robert (2002). "Earlier Spring Snowmelt in Northern Alaska as an Indicator of Climate Change.". Journal of Geophysical Research 107 (4089). :.
Burt, Christopher. . Unprecedented Snow Melt and Heat in the European Alps. Weather Underground 2012.
Hoffman, David. . Climate Monitoring and Diagnostics Laboratory Summary Report No. 24. U.S. Department of Commerce 2012.
Minder, Justin (2009). "The Sensitivity of Mountain Snowpack Accumulation to Climate Warming". Journal of Climate 23: . :.
accelerates snow melt in the
2005 (Less dust)
2006 (More dust)
2008 (Less dust)
2009 (More dust)
: Hidden categories:}