Epishelf, supraglacial, subglacial, and periglacial lakes formation

And №37) How water and energy cycles are linked in the polar regions?

Water and energy cycles are very important elements in planet functioning and climate formation. What is energy? It is transfer of all types of matter through land, atmosphere, hydrosphere and ets. So energy is the most important component of ecosystem. There are few types of energy: internal and external. Internal heating: energy that comes from tectonic and volcanic activities. External: incoming solar and cosmic radiation.

It needs to remember that every transfer of matter is also energy transfer. Thus, we have very complicated mechanism of matter and energy mixing. Let’s consider relations between energy and matter where the matter is water.

Taking into account The Global Water Cycle we can see that there are a lot of interactions between water and terrestrial, hydrological elements.

There are a lot of transformations that need energy to change their state phase. (note:look at the picture and say everything what you want)

Water balance equation: (P+G_in) – (Q+ET+G_out) = ∆S

∆S = P – ET – Q - D (The equation balances the change in water stored within the basin (S) with inputs and outgoes). The input is precipitation (P) and the outgoes are evapotranspiration (which is to be estimated), streamflow (Q), and groundwater recharge (D). If the change in storage, precipitation, streamflow, and groundwater recharge are all estimated, the missing flux, ET, can be estimated by rearranging the above equation as follows:

ET = P - ∆S – Q – D

λE = R_n – G – H (where λE is the energy needed to change the phase of water from liquid to gas, R_n is the net radiation, G is the soil heat flux and H is the sensible heat flux.)

Radiation balance: Q = (K↓ - K↑) + (L↓ + L↑)

K↓ - incoming shortwave radiation; K↑ - outgoing shwr = aK↓; L↓ - incoming longwave radiation = ɛ_ssT_s⁴; L↑ - outgoing lgwr = ɛ₀sT₀⁴

(K↓ - K↑) + (L↓ + L↑) = H + LE + G,

H – sensible heat flux; LE – latent heat flux; G – ground heat flux

Also you can tell about energy that stored in snowpack, glaciers; wind as source of energy (and also transfer water,snow).

A – interflow B – baseflow C – runoff D – evaporation E – precipitation F – interception J – throughfall H – net rainfall G – canopy interception loss

№9 Terrestrial water balance. Spatial distribution of water balance components in the Polar Regions.

P = R + E + ∆S,

P – precipitation, R – streamflow, E – evapotranspiration.

R: Channel precipitation, Groundwater, Interflow, Overland Flow

E: is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere

P: any product of condensation

 

Epishelf, supraglacial, subglacial, and periglacial lakes formation

Epishelf lakes. When ice shelves completely block the mouth of a fiord, a unique type of lake is created called an epishelf lake. This is caused by meltwater that flows into the fiord every summer but is impounded behind the ice shelf. Since freshwater is less dense than seawater, it floats on top of the ocean in a layer that is as deep as the ice shelf. A thick perennial ice-cover on the surface of the fiord helps to prevent the wind from mixing the two layers together.

Supraglacial lakes. A supraglacial lake is any pond of liquid water on the top of a glacier. Although these pools are ephemeral, they may reach kilometers in diameter and be several meters deep. They may last for months or even decades at a time, but can empty in the course of hours. Lakes may be created by surface melting during summer months, or over the period of years by rainfall, such as monsoons. They may dissipate by overflowing their banks, or creating a moulin.

Subglacial lakes. is a lake under a glacier, typically an ice cap or ice sheet. The water below the ice remains liquid since geothermal heating balances the heat loss at the ice surface. The pressure causes the melting point of water to be below 0°C. The ceiling of the subglacial lake will be at the level where the pressure melting point of water intersects the temperature gradient. In Lake Vostok the ice over the lake is thus much thicker than the ice sheet around it.

The water in the lake can have a floating level much above the level of the ground threshold. In fact, theoretically a sub-glacial lake can even exist on the top of a hill, provided that the ice over it is so much thinner that it creates the required hydrostatic seal.

The floating level can be thought of as the water level in a hole drilled through the ice into the lake. It is equivalent to the level at which a piece of the ice over it would float if it were a normal ice shelf. The ceiling can therefore be conceived as an ice shelf that is grounded along its entire perimeter, which explains why it has been called a captured ice shelf. As it moves over the lake, it enters the lake at the floating line, and it leaves the lake at the grounding line.

Periglacial lakes are exist in periglacial territory after glacier retreat. (moraine – thawing – lake formation).