Lecture 5 - Supraglacial Hydrology

Flashcards about superglacial hydrology of glaciers with fill-in-the-blanks, vocabulary, and question and answer styles.

Why is it important to read the assigned paper on mass balance before the seminars?

To ensure thorough comprehension and readiness for discussions.

What does the term 'q m' represent in the context of glacier energy balance?

The amount of energy available on the glacier surface for melt, crucial for understanding supraglacial hydrology.

What are the primary components that make up the energy available for melt on a glacier surface?

Shortwave and longwave radiation, sensible and latent heat fluxes, heat from precipitation, and heat from conduction.

What is supraglacial hydrology concerned with?

The upper area of the glacier, encompassing snowpack, firn, supraglacial lakes and streams.

What is 'firn' in the context of glaciers?

Snow that has lasted at least one year and is being compressed into glacier ice.

What does ELA stand for in glaciology, and what does it represent?

The division between the accumulation and ablation areas on a glacier.

Where can supraglacial streams drain?

They can run directly into a proglacial channel or dive into the ice through a moulin or crevasse.

What are the two thermal states that snow can exist in?

Isothermal (at melting point) and cold (below melting point).

What is an ice lens in a snowpack?

A layer of ice within the snowpack formed by refreezing meltwater.

What are the two primary pathways for meltwater movement within a snowpack?

Vertical (through pore spaces) and horizontal (along ice lenses).

What is irreducible water content in a snowpack?

The water that saturates snow crystals and does not contribute to downstream flow.

What is superimposed ice, and how does it form?

Meltwater that penetrates and refreezes, forming ice layers or lenses.

Saturated snow towards the base of the snowpack can be modeled by what?

Darcyan flow.

Why is modeling water flow in unsaturated dry or cold snow so challenging?

Difficult due to irreducible water content, latent heat effects and ice layer formation.

What are the two states that the firn can exist in?

Saturated or unsaturated.

How does water storage capacity in firn compare to that of the snowpack, and why?

Storage is typically greater due to the larger depth of the firn layer compared to the snowpack.

What is an aquifer, and why are they important in the context of firn?

A large subsurface storage mechanism within the firn that fills with meltwater in the spring and drains in the autumn.

Why is the seasonal variation of water storage in firn important to understand?

Important for energy balance modeling and the longevity of ice shelves.

What causes supraglacial streams to form?

They form where there isn't much percolation into the ice surface.

Under what conditions do supraglacial lakes tend to form?

In areas of low surface elevation, relatively flat areas, and where the snowpack and firn are saturated.

What is hydrofracture, and how does it relate to the drainage of supraglacial lakes?

The lake volume becomes so large that it exerts significant weight on the ice below, leading to drainage through a crevasse.

What primarily causes the formation of supraglacial lakes on debris-covered glaciers in the Himalayas?

Differential melt processes due to varying debris thickness.

Why are supraglacial lakes in Greenland a hot topic of research?

They contribute to increased drainage to the bed, affecting ice velocity, and can result in localized speed ups.

How might the drainage of meltwater lakes on ice shelves contribute to ice shelf breakup?

Drainage of meltwater ponds can contribute to ice shelf breakup.

According to the study of the Larsen B ice shelf breakup, how does tidal flexure influence ice shelf stability?

Tidal flexure weakens the ice shelves and can cause chain reaction drainage events.

What effect does a snowpack have on the delay in transit of meltwater through the system?

A delay in the transit of meltwater through the system.

What are the key components of the supraglacial system that contribute to water storage?

Aquifers, snowpack, firn and supraglacial lakes.

On what timescale do glaciers themselves store water?

Glaciers store water as ice on years to century timescales.

On what timescale does water storage occur for snow cover, firn and further down in the glacier environment?

Days to months

How does storage and runoff in the snowpack change through the melt season?

Increases through the melt season as the snowpack becomes saturated and more energy is available for melt.

How efficient is meltwater transit in areas of glacier ice verses areas with a snowpack?

Much more efficient with channels being carved into the glacier surface.

What is the impact of a snowpack on the mean daily discharge of meltwater?

A smaller mean discharge.

What can be said of water discharge in areas where there is a fern layer against where there is not?

The dotted line shows a higher peak in water discharge where there is no fern layer.

What is meant by 'Gaining Stream'?

There does not appear to be a clear answer based on this lecture.

What typically causes Yucca Alps outbursts?

Are caused by geothermal heat or volcano errutions within an ice body.

What is contributing to the increase in glacier lake outbursts?

Increased in the number of glacier lakes due to climate change.

What are the main considerations when analyzing meltwater storage on glaciers?

How long water is stored and whether it will be released slowly or catastrophically.

What determines the hydrological regime of superglacial systems?

Snow, fern and ice, their features, formation controls, saturation and storage capacity contribute to how long meltwater can be stored.

In the next lecture, what will be discussed regarding the unglacial system?

Water being stored within the ice body.

What takes in or releases energy when there are changes in states, such as water to ice or water vapor to ice?

Latent heat transfers