Glaciation

What are Milankovitch cycles?

The variation in the earths orbit (eccentricity) the angle (obliquity) and the earths axis (precession).

What is meant by eccentricity?

When the earth's natural orbit is not completely circular due to the gravitational pull of Saturn and Jupiter leading to the orbit becoming slightly elliptical.

What is the term for when the Earth is closest to the sun and what does it mean for the climate?

The term is Perihelion and it means that the climate should be warmer.

What is the term for when the earth orbits the sun from a further distance?

Aphelion is the term and this usually means that the climate should be cooler.

What is meant by Obliquity?

Changes in the tilt of the earth's rotational axis, this is the cause of seasons

What are the variations of tilt angles?

20-24 degrees

What does it mean when the angle of the tilt is increased?

It usually means that seasons become more extreme meaning that there is more solar insolation in the summers, and less in the winters which then results in deglaciation.

What does it mean if the Angle of the earth's tilt is decreased?

Seasons become milder and less extreme, this will lead to the build up of snow and ice due to a absence of summer melting. This will consequentally lead to the triggering of glaciations.

What are precessions?

They are wobbles in the earth's rotational axis.

Why does the earth wobble?

Due to the tidal forces caused by the gravitational pull of the sun and moon

What do axial precessions do from a seasonal aspect?

The precessions make seasonal contrasts greater in one hemisphere and lesser in the other.

What happens when precessions allow sea ice to build up?

When sea ice builds up in one hemisphere the ice will reflect solar radiation driving a feedback loop that can plunge the planet back into an ice age.

How do ice sheet dynamics impact Thermohaline Circulation?

With the melting of glaciers and the rise in temperatures in the sea, the warming water in the arctic disturbs global ocean currents. The gulf stream will have less water to draw North and maintain warm ocean temperatures. This will eventually lead to the cooling of Northern oceans.

What does increased global warming lead to from a climate perspective?

More evaporation

As a result of air pollution- more cloud cover

What do cloudy skies do to combat the amount of warming?

The clouds will reflect the energy back to space due to their high albedo which will then lead to less radiation being absorbed by the earth.

How to volcanic eruptions lead to positive feedback in the atmosphere?

Volcanic eruptions inject gases into the atmosphere which then will contribute to the greenhouse gas effect in the short term. However with the ejection of Sulfur Dioxide the sulfuric acid reflect the sunlight back into space which then leads to global cooling that lasts several years.

How does Sulfuric acid form condensation nuclei?

Sulfur dioxide mixes with the atmosphere and oxides to form sulfuric acid, this acid then quickly condenses into fine sulfuric aerosols. Finally these sulfate particles act as hygroscopic condensation nuclei, meaning that water vapour readily condenses onto them to form cloud droplets.

What is the cryosphere?

Refers to cold environments where water is in its solid form of ice.

What is a glacier?

A large slow moving mass of ice

How are glaciers formed?

Through compacted layers of snow

How much do glaciers take up globally?

10% of the worlds land mass

What’s different about niche glaciers?

They are much smaller and occupy gullies/hollows

What are corrie glaciers?

Larger than niche glaciers, they occupy hollows on the face of the bedrock in moutainous regions.

What happens when ice accumulates on a corrie glacier?

The sufficient thickness of the ice begins to scour the hollow out even more through erosion, this results in smooth ampitheatres on the valley walls

What sometimes happens with Corrie Glaciers and Valley Glaciers?

Occasionally the corrie glaciers will spill over the corrie lip and feed into valley glaciers.

Define Alpine/ Valley glaciers

They are confined to mountain valleys

They flow from high to low elevations

Shape of the glacier is controlled by the valley

What is a Piedmont Glacier?

a glacier that spreads out as a wide lobe as it leaves a narrow mountain valley to enter a wider valley or plain

What is meant by an ice cap?

An ice mass that covers less than 50,000km²

Ice flows away from the highest point and towards the ice’s periphery

What are the inputs in a glacier system

Precipitation in the form of snow,ice and avalanches

What is the storage of the Glacier System?

The glacier itself

What are the outputs of the Glacial System?

Water Vapour

Sublimation

Ablation

Moraine

What is meant by ablation?

Melting that produces water

What is a moraine?

Material that deposits at the snout

What is the Zone of Accumulation?

Upper sections of the glacier where inputs exceed outputs

What is meant by Net Gain?

When the Snout advances

What is meant by the Zone of Ablation?

Lower sections of a glacier, where outputs exceed inputs

What is meant by Net Loss?

When the Snout retreats

What is the Equilibrium Line?

a line that separates the two zones, represents the snow line

What is meant by Net Balance?

difference between the total accumulation and total ablation during one year

Why is their negative glacial budget in the summer?

Due to more ablation as a result of higher temperatures. This means that more ice will melt, leading to retreation

Why is there positive glacial budget in the winter?

Due to more accumulation than ablation since there is more snowfall and less melting. This results in the glacier advancing.

Which glacier is the longest in Europe?

Aletsch Glacier in Switzerland- 14 miles long

How much has the Aletsch glacier retreated since 1984?

Receeded over 1300 meters

How much of the Rhone Glacier has retreated?

60% of its volume since 1850

What happens to the Ice movement during Deformation?

The ice crystals slip and slide past each other, they then orientate themselves in the direction the ice is flowing

Why do ice crystals become deformed?

Due to the downward force of gravity which leads to them moving downhill

Where does Deformation take place?

In cold and warm based glaciers

How do glaciers move?

Gravity

Mass of ice

Basal slip

What is Basal Sliding?

Physical sliding of glacier over bedrock which is enabled and lubricated by meltwater between the base of the glacier and the valley floor

What is Regelation Creep?

When ice meets an obstacle, high pressure on the upstream side leads to the lowering of the melting point, then causing ice to become water. The water then flows around the obstacle and refreezes in a place of lower pressure

What is internal deformation?

When crystals deform under high pressure as a result of the layers of ice. Individual ice crystals re-orient, slip, and slide past one another along microscopic planes of weakness

What are the different glacial flows?

Extensional Flow

Compressional Flow

Rotational Flow

What is Extentional Flow?

When the slope becomes steeper the ice accelerates and thins out and then fractures under brittle stress to form crevasses

What is Compressional Flow?

Occurs when the slope gentles or flattens out. The ice slows down, and trailing ice pushes into the slower ice ahead, causing the mass to pile up, thicken, and override itself.