Topic 2 EQ1 Flashcards
What is a greenhouse Earth?
When there is no ice or glaciated landscapes on Earth
What is an Icehouse Earth?
An Earth where there are ice sheets present. Fluctuates between glacial and interglacial periods.
What are glacial periods?
A cold period of time during an ice age. For example the Pleistocene epoch.
What is an interglacial period?
A warmer period of time within an ice age
What is the Pleistocene epoch?
A glacial epoch in the quaternary period which started approximately 2.6 million years ago. It lasted 2 million years and ended approx. 11,500-12,000 years ago.
What is the Holocene epoch?
An interglacial epoch which started approximately 11,500 - 12,000 years ago and it is the epoch we are in.
What are stadials?
Short lived pulses of ice advances
What are interstadials?
Warmer periods where ice retreats
When was the Loch Lomond Stadial?
Occurred between 12,000 and 10,000 years ago and marked the end of the Pleistocene epoch.
What was the last known glacial advance?
Devensian which occurred approximately 18,000 years ago
What caused the start of the quaternary ice age?
It was due to the continental drift between the North and South American continents 3 million years ago which created the Panama Isthmus. It re routed the ocean currents North - West towards Europe which created the Gulf Stream which scientists think that it transported extra moisture to the Arctic atmosphere which fell as snow which triggered the build up of the Greenland ice sheet.
What are the three Milankovitch cycles?
Eccentricity
Obliquity
Precession
What is the Eccentricity cycle?
The shape of the Earth’s orbit varies from circular to elliptical over 100,000 year cycles which affects the amount of solar radiation the Earth receives.
What is the Obliquity cycles?
The tilt of the Earth’s axis varies between 21.5°c and 24.5°c over 41,000 year cycles which affects the seasons.
What is precession of the equinoxes?
The Earth wobbles as it spins on its axis. It varies over 21,000 year cycles which result in changes in the intensity of seasons.
How can the Milankovitch cycles cause long term climate change?
They can combine together to minimise the amount of solar energy reaching the Northern hemisphere during summer (leading to cooler summers)
Support for Milankovitch’s theory
Glacials have occurred at regular intervals of approximately 100,000 years which is the time for the cycle to occur.
Impact of the Milankovitch cycles
Change global temperatures by between 0.5°c and 1°c.
What are climate feedback mechanisms?
Feedback effects are those that can either amplify a small change and make it larger (positive feedback) or diminish the change and make it smaller (negative feedbacks)
Positive feedback increasing the warming
- decrease in albedo
- methane emissions from melting permafrost
- calving ice sheets - further loss of snow leading to less albedo
Positive feedback increasing cooling rates
Small increases in snow raise surface albedo so more solar energy is reflected back to space leading to further cooling which could lead to further snowfall and ice cover.
Negative feedback decreasing the warming
Increasing global warming leads to more evaporation and over time pollution from industrialisation adds to global cloud cover. Increasingly cloudy skies could reflect more solar energy back to space which would slow down warming which is called global dimming.
What is albedo?
The reflective coefficient of a surface
What is calving ?
The breaking up of chunks of ice at the glacier snout or ice sheet front to form icebergs as the glacier reaches a lake or ocean.
What is thermohaline circulation?
A global system of surface and deep water ocean currents driven by differences in temperature (thermo) and salinity (haline) between areas of the oceans .
How can solar forcing cause short term climate change?
- sunspots increase solar energy
- sunspot vary as a result of magnetic storms on the suns surface and they have a 11 year cycles
- reliable records for 400 years
- maunder minimum 1645-1715 had no sunspot activity
- variation in solar radiation caused by sunspot activity is only 0.1%
How can volcanic causes contribute to short term climate change?
Eruptions with a high volcanic explosivity index eject huge amounts of ash, sulfur dioxide, water vapour and carbon dioxide which high level winds distribute around the globe. Sulphur particles increase the reflection of radiation from the sun back into space.
What is the most significant volcanic eruptions in recorded history?
1815, Tambora in Indonesia ejected 200 million tonnes of sulphur dioxide into the atmosphere and in the following 2-3 years temperatures were recorded to be 0.4-0.7°c lower.
What was the Loch Lomond stadial
A short term advance of ice 12,500 years ago during the retreat which started 18,000 years ago. 11,500 years ago temperatures were 6-7°c lower. Glaciers readvanced in many parts of the world including the formation of ice caps in the Scottish highlands
What caused the Loch Lomond Stadial?
It may have been triggered by the drainage of the huge proglacial Lake Agassiz disrupted the THC which cut off heat from the Gulf Stream.
What was the little ice age?
Between 1350 and 1900 conditions were slightly cooler by around 1 -2 °c. Rivers were frozen in the UK, Europe and New York. Polar bears were spotted in Iceland and farms were abandoned in Scandinavia. Curling became a national sport in Scotland. Some researchers say that the little ice age could have developed into a stadial if it wasn’t for the industrial revolution.
What was the cause of the little ice age?
Volcanic activity has been suggest but climate change on a timescale of a hundred years and 1-2°c can’t be solely explained by volcanoes.
Maunder minimum 1645 -1715
What is the cryosphere?
The parts of the Earths crust and atmosphere subject to temperatures below 0°c for at least part of each year. All the ice sheets and glaciers.
What are the four main roles of the cryosphere?
The albedo effect
Store within hydrological cycle
Exchange of mass and energy to other stores
A barometer of climate change due to the constant growth and retreat
What is an ice cap?
Smaller version of ice sheet occupying upland areas. Usually dome shaped. 3 - 10,000 km sq unconstrained
What is an ice field?
Ice covering an upland area but not thick enough to cover the topography. 10-10,000 sq km unconstrained
What is a valley glacier?
A glacier confined between valley walls and terminating in a narrow tongue. 3 - 1500 sq km constrained
What is the piedmont glacier?
A valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out like a fan. 3 - 1000 sq km constrained
What is a Cirque glacier?
A smaller glacier occupying a hollow on the mountain side - carved out a Corrie or cirque. 0.5 - 8 sq km constrained
What is an ice shelf?
Large area of floating glacier ice extending from the coast where several glaciers have reached sea and coalesce. 10 - 100,000 sq km unconstrained.
Where do warm based (temperate or wet) glaciers occur?
High altitude areas outside the polar regions such as alps and sub arctic areas
Temperature of surface layer of warm based glaciers.
Fluctuates above and below melting point depending of the time of year
Impact of increased pressure of overlying ice in warm based glaciers
Water exists as a liquid at temperatures below 0°c causing the basal ice to melt continuously
Effects of pressure, geothermal energy and percolation of meltwater in warm based glaciers
Contribute to prevent the glacier freezing to its bed.
Features at the base of warm based glaciers
Lots of debris and significant subglacial depositional features
Where are cold based (polar) glaciers located?
High latitude
Surface temperatures of cold based glaciers
Extremely low at -20 -30°c
Average temperature of ice of cold based glaciers
0°c
Temperature at the base of cold based glaciers
Still below 0 °c as the geothermal heat is not enough to raise the temperature even though the ice may be up to 500m thick
Features at the base of cold based glaciers
Very little surface melt in the very short and cool polar summer so little percolation occurs. The glacier is permanently frozen so there is no debris
What is a polythermal glacier?
The underneath is warm and wet based glacier and the margin is cold based. Large glaciers are cold based in their upper regions but warm based lower down when they extend into warmer climatic zones
What are surging glaciers
Have high rates of flow and May move up to 100 meters a day, for example the Greenland outlet glaciers which average 30 meters a day
Present glacial ice cover
Over 10% of the Earth’s water and 75% of worlds fresh water is locked up in ice about 1.8% of total fresh water
Percentage of current glacier ice in Antarctica
85%
Percent of total glacier ice in the Greenland ice chest Outtel
Nearly 11%
Where is the remaining ice cover
Distributed among ice caps such as Northern Canada and Alaska
What is the environmental lapse rate
The rate of atmospheric temperature decreases with altitude at a given time and location
Two factors that influence the distribution of ice cover
Latitude and altitude
How do high latitudes impact ice cover?
The suns rays hit the ground at a lower angle so the solar energy received has to heat a larger area
How does high altitude impact ice cover
Impacted by the environmental lapse rate whereby temperatures decline by 1°c for every 100m
Local factors affecting ice cover
Aspect and relief
How does relief and aspect impact ice cover
In mountainous areas, they both combine to affect the distribution of cirque glaciers. In the northern hemisphere, north- and east - facing close are both more sheltered and shadier and so snow accumulates
Pleistocene maximum vs present day
Three times greater than present day
Antarctic and Greenland ice sheets during Pleistocene
Only covered a slightly greater area than today
Major extensions during the Pleistocene
In North America (Laurentide and Cordilleran)
The Scandinavian ice sheet in Europe
Grew to 3000- 4000
Other extensions during the Pleistocene
Southern South America, South Island New Zealand, Siberia, Himalayas
Meaning of peri glacial
Refers to the climate conditions and landscape that characterised the areas near the margins of glacier ice the Pleistocene. Now therm it has widely been used to include non-glacial cold climate areas
Characteristics of a Peri glacial climates
- highest average annual temperature range between 1°c to -4°c
- daily temperature below 0°c for at least 9 months and below -10°c for at least 6 moths
- temperature rarely rise above 18°c
- typically under 600 mm precipitation a year(100 in winter and 500 in summer
How much of the Earths surface experiences periglacial conditions today?
20%
How much of the Earths surface experienced periglacial conditions in the Pleistocene?
33%, extending across much lower latitudes
How far did periglacial conditions extend?
Across Europe it went as far as Southern France, Northern Italy and the Balkans
What is permafrost?
Permanently frozen ground but technically it refers to soil and rock remaining frozen as long as the temperature doesn’t rise above 0°c in the summer for two consecutive years
What is continuous permafrost?
Forms in the coldest areas of the world where it extends downward for hundreds of meters
What is discontinuous permafrost
More fragmented and thinner
What is sporadic permafrost?
Occurs at the margins of periglacial environments and is usually very fragmented and very thin; often it occurs on shady hillsides or beneath peat
What is the active layer?
Top layer of soil in permafrost environmental that thaws during the summer and freezes during the winter
How much of the Earths surface is currently experiencing permafrost?
25%
How does climate influence the distribution and character of permafrost?
Climate is the main control, as temperature and the amount of moisture available determine the presence or absence, depth and extent of permafrost
How does proximity to water affect permafrost on a local scale?
Lakes are relatively warm and remain unfrozen throughout the year with a deep active layer and act as insulation.
How does slope angle and orientation affect permafrost
North facing - low solar radiation
High slope orientation - more solar radiation
How does the character of the ground surface affect permafrost on a local scale?
Dark compact rocks absorb a greater amount of solar radiation
How can vegetation cover affect permafrost on a local scale?
Insulates ground from extreme temperatures with leaf litter
How can snow affect permafrost on a local scale?
Less solar radiation would be absorbed and more reflected as a result of the albedo affect
4 periglacial processes
- 9% expansion of water freezing
- contraction and cracking of rapidly freezing soils creating patterned ground
- the migration of sub surface water to the freezing front by suction which causes the formation of segregated ice leading to the formation of ice lens
- mass movement of the active layer downslope by solifluction
What are block fields?
Accumulations of angular, frost - shattered rock, which pile up on flat plateau surfaces
What are Tors?
Crown hill tops which form where more resistant rock occurs
What is scree?
Forms when rock fragments fall and accumulate on the lower slope or base of cliffs.
What are pro talus ramparts?
Created if a patch of snow settles at the base of cliff. When rock falls it settles at the base of the snow patch creating a rampart
What are rock glacier?
Form when large amounts of frost shattered rock mixes with ice. Look like streams/fans or angular rocks. They are conjoined with interstitial ice below and move slowly like glaciers, at rates of up to 1 m a year.
What is a frost creep?
Slow form of mass movement; material moves downslope just a few centre metres a year
What is solifluction?
Occurs in regions underlain by permafrost. During the summer months the active layer melts forming a mobile water-saturated layer.
What are asymmetric valleys?
Different rates of solifluction and frost creep lead to one side of the valley being significantly steeper than the other.
For example, in the Northern hemisphere, south facing slopes are more exposed to the sun and thaw more frequently.
What is Nivation?
When snow gets into a hollow in the ground, it can increase the size of the hollow. The temperature often fluctuates around 0°c so a lot of freezing and thawing happens
What forms as a result of Nivation?
Nivation hollows
What is Aeolian action?
Due to limited vegetation cover, the wind is able to pick up and transport fine dry sediment from the ground.
What are Loess?
Excessive wind blow deposits
What is meltwater erosion?
During the short summer, thawing creates meltwater which erodes the stream or river channel. Re freezing in the winter causes reduction in discharge and sediment deposition in the river.
What is a braided stream?
A stream with multiple channels as they are separated by islands of deposited materials
