GL 1 Flashcards by Holly Bee

What is a glacier?

Moving body of ice due to gravity

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How far do some glaciers move per day?

Up to 25cm per day

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Why are glaciers important and how many people rely on them?

Drinking water, crop irrigation, tourism, recreation and hydroelectricity
1/3 of the world’s population rely on glaciers

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Where are glaciers found

High latitude (poles) and altitude (mountainous) locations, where the temperature is regularly below 0 degrees Celsius (Cryosphere)

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Examples of accumulation (inputs) of snow.

Wind blown snow, Precipitation, desublimation (condensation into ice), avalanche debris.

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Examples of ablation (outputs) of snow

Meltwater, Calving (breakaway of ice), Rock debris, wind-blown snow, avalanche debris, solar energy, sublimation (evaporation from ice).

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Where does accumulation occur?
Where does ablation occur?
What is the line of equilibrium?

accumulation at head
ablation at snout
line of equilibrium is where inputs = outputs

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Describe the formation of glaciers

Snow falls, which contains ait, more snow falls, compacting the pre existing snow. Snow that survives one winters freezing and one summers thawing is called firn. In summer meltwater percolates into the firn, in winter it refreezes, causing it to become denser. After several years and a depth of 20m, there is very little air left and glacial ice is formed.

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What is mass balance?
Positive?
Negative?

Mass balance is the growth or retreat of a glacier
Positive - growth
negative - retreat

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What is till?

Unsorted material deposited directly by glacial ice

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Glacier advance and retreat

Positive mass balance means glacier advances, becoming thicker
Negative mass balance means glacier retreats, but is still flowing forward due to gravity, causing the glacier to become thinner.

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Mass balance graph and description:

In winter there is lots of accumulation, in spring and autumn there is equal amounts of accumulation and ablation in summer there is more ablation then accumulation.

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What percentage of glaciers currently have a negative mass balance

75%

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What is a ice period

permanent ice at the poles

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What is an interglacial period?

Periods of warm, causing glaciers to have a negative mass balance

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What is a Glacial period?

Period of cold, causing glaciers to have positive mass balance.

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Name the glacial and interglacial starting from the present

Holocene (present), Devensian, Ipswichian, Wolstonian, Hoxian

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Are we currently in interglacial or glacial period

Holocene (Interglacial)

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Why do cycles of Interglacial or Glacial periods exist?

Milankovitch cycles.

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Perihelion meaning.
Aphelion meaning.

Closest point to the sun
Furthest point from the sun

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Winter solstice
Summer solstice
Equinox

Shortest day
Longest day
Equal insolation of both hemisphere

What are Milankovitch cycles?

Orbital variations.

Stretch (eccentricity) of the orbit description

Impact of orbital shape (more oval vs more circular)

Axis tilt (Obliquity).

Tilt of the earth changes

Wobble (precession)

earth wobbles in orbit

What is long term climate change and glacial and interglacial periods caused by?

Milankovitch cycles

What is positive feedback in relation to glacial budget

Positive feedback amplifies changes in a glacial budget. Cooling leads to further cooling, warming leads to more warming

What is surface albedo?

Earth's reflectivity

Why is it important to have high surface albedo?

More reflective surfaces, so more insolation is reflected back into space, causing decrease in temperature.

What happens when there is low surface albedo?

Ice has melted, so there are less reflective areas, Insolation is absorbed into water, causing the temperature to increase

Positive feedback relationship in with positive mass balance

Cooling of climate, Artic sea water freezes (ice cover increases), Darker surfaces hidden, increased albedo, decreased absorption of insolation...

Positive feedback in relationship with negative mass balance

Increases in temperature, Artic sea ice melts, darker surfaces revealed, Albedo reduced, Increased absorption of solar radiation.

Why is it hard to undo glacial melting

Warming leads to more warming due to positive feedback loops.

Negative feedback in relation to glacial budget

Negative feedback reduces changes in a glacial budget. Warming leads to cooling

What is the thermohaline ocean circulation

Brings warm salty water to northwest Europe, causing warm winter conditions.

What happens to cold water vs hot water

Cold water sinks Hot water rises

What is the Younger Dryas period

Towards the end of the last glacial period when temperatures were rising, change to ocean currents led to a rapid period of cooling known as the Younger Dryas.

How long did Younger Dryas period last

2 thousand years

Explain how thermohaline currents caused the Younger Dryas period

Northern regions heated by the oceans. Ocean circulation is driven by Coldwater sinking in the North Atlantic. freshwater from melting glaciers made surface water less dense, keeping it from sinking. Air became colder, ice reformed

Give 3 short term causes of climate change

Solar forcing (sunspots), Volcanic eruptions, Anthropogenic (human) factors.

What is solar forcing?

Energy released by sun (sun spots)

What was the little ice age caused by?

Low level of solar outputs

When was the little iceage?

1645-1715

What happened during the little ice age?

Sea ice expanded into Atlantic, Baltic sea, rivers in the UK froze over. Permanent snow in Scotland mountains. Glaciers advanced

Why do volcanic eruptions impact glaciers

Volcanoes release sulphur dioxide and ash, reflect income solar radiation, leading to a decrease in temperature.

Give one examples of Volcanoes that have impacted on climate change

Laki, Iceland, 1783, Europe was 3 degrees Celsius lower.

What is Anthropogenic factors of short term climate change

Human activity linked to combustion of fossil fuels, releasing greenhouse gasses, causing enhanced greenhouse effect.

How much has temperatures increased by due to anthropogenic factors

1.2 degrees Celsius since 1880

What was ice extent like during the Devensian? What else did this impact upon?

Ice reached much further south, covering parts of the UK. Sea ice reached Iceland and Greenland. Due to this coastlines were much bigger as there were lower sea levels

Why are Glaciers found at high latitudes?

Axis tilt of earth means they get less sunlight, meaning snow can fall consistently and meltwater will refreeze

Why are glaciers found at high altitudes?

Low pressure, cool air (due to work done to rise), causing snowfall