GL 1 Flashcards
What is a glacier?
Moving body of ice
How far do some glaciers move per day?
Up to 25cm per day
Why do glaciers move?
Gravity forcing them down
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
What is happening to many glaciers around the world?
What does this cause?
Many glaciers around the world are melting (negative mass balance).
This is causing sea levels to rise 2.6m in the last 60 years, causing extinction of animals, loss of resources, ecosystems and habitats
Where are glaciers found
High latitude (poles) and altitude (mountainous) locations, where the temperature is regularly below 0 degrees Celsius (Cryosphere)
Examples of accumulation (inputs) of snow.
Wind blown snow, Precipitation, desublimation (condensation into ice), avalanche debris.
Examples of ablation (outputs) of snow
Meltwater, Calving (breakaway of ice), Rock debris, wind-blown snow, avalanche debris, solar energy, sublimation (evaporation from ice).
Where does accumulation occur?
Where does ablation occur?
What is the line of equilibrium?
accumulation at head
ablation at toe
line of equilibrium is where inputs = outputs
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.
What is mass balance?
Positive?
Negative?
Mass balance is the growth or retreat of a glacier
Positive - growth
negative - retreat
Draw a Glacier flow diagram
:)
What is till?
Unsorted material deposited directly by glacial ice
What is a moraine?
Deposited sediment from a retreating glacier
Moraines formation
Till is deposited by glacier, debris dropped on top of glacier and material eroded from plucking.
Retreating glacier causes sediment to be deposited, causing a recessional moraine to form
Glacier advance and retreat
Positive mass balance means glacier advances, becoming thicker and ploughs over moraines.
Negative mass balance means glacier retreats, but is still flowing forward due to gravity, causing the glacier to become thinner.
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.
What percentage of glaciers currently have a negative mass balance
0.75
How much of the earth’s surface is covered by glaciers?
0.1
How much of the world’s freshwater is stored in glaciers?
0.75
What is a ice period
permanent ice at the poles
What is an interglacial period?
Periods of warm, causing glaciers to have a negative mass balance
What is a Glacial period?
Period of cold, causing glaciers to have positive mass balance.
When was the Holocene period
Interglacial or Glacial?
11,500 ybp to present
Interglacial
When was the Devensian period?
Interglacial or Glacial?
80,000 ybp to 11,500 ybp
Glacial
When was the Ipswichian period?
Interglacial or Glacial?
80,00 ybp to 100,000 ybp
Interglacial
When was the Wolstonian period?
Interglacial or Glacial?
100,000 ybp to 140,000 ybp
Glacial
When was the Hoxian period?
Interglacial or Glacial?
140,000 ybp to 200,000ybp
Interglacial
Why do cycles of Interglacial or Glacial periods exist?
Changes in long-term cyclical change, due to changes in Earth’s orbits around to sun, leading to a variation of insolation received by the earth, caused mostly by Milankovitch cycles.
What is the current tilt of the axis of the earth?
23.5 degrees
Perihelion meaning.
Aphelion meaning.
Closest point to the sun
Furthest point from the sun
Winter solstice
Summer solstice
Equinox
Shortest day
Longest day
Equal insolation of both hemisphere
What are Milankovitch cycles?
How much of they impact the amount of incoming insolation
Orbital variations.
Causing up to 25% variation
Stretch (eccentricity) of the orbit description
Impacts
Time frame
Impact of orbital shape (more oval vs more circular). At most elliptical there is 23% more insolation then at furthest point. Every 100,000 years
Axis tilt (Obliquity).
Impacts
Time frame
Tilt of the earth, varies between 22.1 and 24.5 degrees. Tilted towards the sun causes warmer climates, vice versa.
Over 41,000 years
Wobble (precession)
Impacts
Time frame
earth wobbles in orbit due to the relationship between the sun and moon (Tidal forces). Causes variations in temperatures. Takes 25,771.5 years
What is long term climate change caused by?
Milankovitch cycles
What is responsible for glacial and interglacial periods?
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
How much insolation is reflected and absorbed by ice and snow (high albedo)
90% reflected to space
10% absorbed
(lower temperatures)
How much insolation is absorbed/reflected with water (low albedo)
6% reflected
94% absorbed
(temperatures 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
Give an example of negative feedback in relation to glacial budget
Younger Dryas, due to thermohaline
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 (Devensian) when temperatures were rising, the disruption to this ocean current in the North Atlantic led to a rapid period of cooling known as the Younger Dryas.
When did the Younger Dryas occur?
13.25 thousand ybp to 11.25 thousand ybp
How long did Younger Dryas period last
2 thousand years
What was the drop of temperature in Greenland during the Younger Dryas?
-35 to -50 degrees celcius
What was the change of ice accumulation in the Younger Dryas period
0.25 -> 0.32
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. 12,800 years ago, freshwater made surface water less dense, keeping it from sinking. Air became colder for more then 100 years due to lack of northward transport of warm water. Northern Hemisphere has conditions like the last ice age. Rewarming occurred 11,600 years ago, within less then a decade ocean circulation was restored.
https://www.youtube.com/watch?v=kqWIwp1beIw
Give 3 short term causes of climate change
Solar forcing (sunspots (increased solar outputs), Volcanic eruptions, Anthropogenic (human) factors.
What is solar forcing?
Energy released by sun
What is solar output linked to?
Sun spot activity
How often do sunspots fluctuate?
On an 11 year cycle
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, Iceland and Greenland were impossible to ship too.
Baltic sea, rivers in the UK (like the Thames) froze over.
Permanent snow in Scotland covered Cairngorm mountains.
Glacier advanced in the Alps and threatened nearby towns
Why do volcanic eruptions impact glaciers
Volcanoes release sulphur dioxide and ash into stratosphere, these reflect income solar radiation, leading to a decrease in temperature.
Give three examples of Volcanoes that have impacted on climate change
Laki, Iceland, 1783, Europe was 3 degrees Celsius lower.
Tambora, Sumbawa Island, 1815, reduced temperatures by 0.7 degrees Celsius for 3 years
Mount Pinatubo, 1991, decreased temperatures by 0.4 degrees Celsius.
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
How much of the Himalayas glaciers are in retreat?
0.95
How far were glaciers in the Himalayas retreating?
10-60m a year. Many small valley glaciers retreat 1km since the little ice age. Small glaciers have already dissapeared
How much higher are temperature in the Himalayas? What effect is this having?
+ 1.6 degrees overall. Decreasing amounts of snowfall
What percentage of glacier mass in the Himalayas are at risk?
1/4 of glacial mass could disappear by 2050
How far has the Chota Shigiri Glacier in the Himalayas retreated?
950m from 1962 to 2008
Where is the Glacier National Park USA
Montana
By what year will the Glacier National park be glacier free?
2030
How many Glaciers have disappeared in the Glacier national park since 1850?
In 1850 there were 150, in 2010 there was 25
Why do New Zealand have areas of glacial growth?
Westerly atmospheric circulation, causing increased snowfall. Causing positive mass balance
Why do areas in New Zealand have zero ice mass balance?
Equal amounts of loss and gain of ice
Why are some areas in New Zealand glacial retreats
Glacial lakes have begun to grow at snouts. Causing calving away from the glacier into icebergs. Glaciers with lakes attached have lost 10% of mass over 30 years.
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
