Glaciated Landscapes and Change Flashcards
What is the Pleistocene Period?
A geological period from about 2 million years ago to 11,700 years ago, the early part of the quaternary which included the most recent age.
What are Interglacial Periods?
Warmer periods similar to present i.e. greenhouse periods.
What are Greenhouse Conditions?
Much warmer interglacial conditions.
What are Glacial Periods?
Cold, ice-house periods within the Pleistocene.
What are Ice-house Conditions?
Very cold glacial conditions.
What is a Polar Environment?
Glacial environments are found in the high latitudes of the Antarctic and Arctic. They are characterised by extremely cold temperatures (average annually of -30 to -40°C and low levels of precipitation.
What is an Alpine Environments?
Glacial environments are found at high altitudes in mountain ranges in the mid-low latitudes e.g. European Alps, the Himalayas and Andes. They are characterised by high levels of precipitation and a wide temperature range with frequent freeze-thaw cycles.
What is a Glaciers Environment?
Slow moving bodies of ice in valleys, which shape the landscape in both polar and alpine environments.
What is a Periglacial Environment?
These environments do not feature glaciers, but are usually found next to glacial areas. They are characterised by permafrost and occur in high latitude areas whereas seasonal temperatures vary above and below freezing point e.g. Siberia, Alaska and northern Canada.
What is the Timeline of the different Glacial Periods?
-Start of the Pleistocene epoch/Quaternary period (2.6 million years ago)
-Devensian Glacial Ended (last glacial maximum) (18,000 years ago)
-End of the Pleistocene/Start of the Holocene Epoch (11,500 years ago)
-Lock Lomond Stadial (last UK glacial advance) (10,000-12,000 years ago)
What are Stadials and Interstadials?
Short term fluctuations within ice-house and greenhouse conditions; stadials are colder periods that lead to ice re-advances, interstadials are shorter periods of warmth.
What are the Short Term Causes of Climate Change?
-Variations in solar output
-Volcanic causes
What are the Long Term Causes of Climate Change?
-Continental Drift
-Eccentricity of the orbit
-Axil Tilt
-Wobble
What are Variations in Solar Outputs (short term)?
The dark areas of the sun (sunspots) are caused by intense magnetic activity in the sun’s interior. An increase in the number of sunspots means that the sun is more active and giving off more energy. They appear to vary over an 11 year cycle.
What are Volcanic Causes (short term)?
Large eruptions can eject huge volumes of ash, sulphur dioxide, water vapour and carbon dioxide into the atmosphere (volcanic aerosols) which are globally distributed by winds. This aerosol blocks the sun’s radiation, cooling the Earth. The ash tends to settle back on Earth within a few months, however the sulphur gas can remain in the atmosphere for up to three years which reflect the radiation back into space.
What is Continental Drift (long term)?
3 million years ago the North and South American tectonic plates collided. This rerouted ocean currents so that warm Caribbean waters were forced northwest, creating the Gulf Stream.
What is the Eccentricity of the Orbit (long term)?
The shape of the Erath’s orbit varies from circular to elliptical over 100,000 year cycles. The Earth receives less solar radiation in the elliptical orbit when the Earth is farthest from the sun.
What is Axil Tilt (long term)?
The title of the Earth’s axis varies between 21.5° and 24.5° over 41,000 year cycles. This changes the severity of the seasons.
What is Wobble (long term)?
The Earth wobbles as it spins on its axis, which means that the season during which the Earth is nearest to the sun varies.
What are the Facts about Loch Lomond Stadial (the Younger Dryas event)?
-Ice sheets began retreating about 18,000 years ago, with rapid deglaciation by 15,000 years ago.
-12,5000 years ago the temperatures plunged downwards and by 11,500 years ago , glacial conditions occurred with temperatures 6-7°C after the event.
-Glaciers readvanced in many parts of the world including the formation of ice caps in the Scottish Highlands.
What are the Facts about The Little Ice Age (the longest glacial oscillation in historical times)?
-Proxy records from historical document and paintings add increased detail to our knowledge of past climate.
-Between 1350 and 1900, conditions were slightly colder between 1°C and 2°C.
-Between 1550 and 1750 there was a low trough of very cold conditions.
-The release of carbon dioxide triggered climate warming, which dramatically halted the cold period.
There were many impacts:
-The widespread abandonment of upland farms in Scandinavia and Iceland.
-Many glaciers in Europe re-advanced down valleys; the Little Ice Age was a period of predominantly positive net mass balance leaving prominent terminal moraines.
-Arctic Sea ice spread further south.
-The release of carbon dioxide triggered climate warmning, which dramatically halted the cold period.
What is the Cryosphere?
Consists of ice sheet and glaciers, together with sea ice, lake ice, permafrost and snow cover.
What are Warm Based Glaciers?
These occur in high altitude areas outside the polar regions e.g. the Alps. The temperature of the ice is often close to zero and mild summer temperature causing melting -> land based.
What are Cold Based Glaciers
These occur in polar glacial environments such as Greenland and Antarctica. These glaciers are frozen onto the bedrock below and melting only occurs on the surface in the summer months -> marine glaciers + land based.
What is an Ice Sheet?
Complete submergence of regional topography; forms a gently sloping dome of ice several kilometres thick in the centre.
Average size - 10-100,000 km².
Example - Greenland and Antarctica.
What is an Ice Cap?
Smaller version of ice sheet occuplying upland areas; outlet glacier and ice sheet drain both ice sheets and ice caps.
Average size - 3-10,000 km².
Example - Vatnajökull, Iceland.
What is an Ice Field?
Ice covering an upland area, but not thick enough to bury topography; many do not extend beyond highland source.
Average size - 10-10,000 km²
Example - Patagonia, Chile and Columbia Canada.
What is a Valley Glacier?
Glacier confined between valley walls and terminating in a narrow tongue; forms from ice caps/sheets or cirques; may terminate in sea as tidewater glacier.
Average size - 3-1,500 km².
Example - Aletsch Glacier, Switzerland and Athabasca, Canada.
What is a Piedmont Glacier?
Valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out like a fan.
Average size - 3-1,000 km².
Example - Malaspina, Alaska.
What is a Cirque Glacier?
Smaller glacier occupying a hollow on the mountain side - carves out a corrie or cirque; smaller version is known as a niche glacier.
Average size - 0.5-8 km².
Example - Hodges Glacier, Grytviken, Sotuh Gerogia.
What is an Ice Shelf?
Large are of floating glacier ice extending from the coast where several glaciers have reached the sea and merge.
Average size - 10-100,000 km².
Example - Ronne and Ross Ice Shelf, Antarctica.
What is Accumulation?
The addition of mass to the glacier (inputs) e.g. avalanches from slopes above, rock debris, wind deposition, meltwater, precipitation (mainly snow).
What is Ablation?
The loss of mass from the glacier (outputs) e.g. evaporation (sublimation), rock debris, breaking away of ice blocks and ice bergs (calving), melting (water).
How is a Glacier Mass Balance/Annual Budget calculated?
Using the total accumulation and ablation within a year.
How does the Glacial System work?
-Glacials gain mass through the transformation of snow into ice and then flow downhill (in response to gravity) and eventually lose mass due to melting.
-Glaciers accumulate mass from snow falling onto its surface, snow avalanching from the valley sides and by accretion of rime ice by direct freezing of atmospheric moisture onto the glacier.
-Glaciers lose or ablate mass by melting as a result of warm air temperature or applied pressure, evaporation, wind erosion or by calving into icebergs along a floating ice front.
-In extremely cold and arid areas, such as the interior of Antarctica ice, mass can also be lost by sublimation (ice changing directly into water vapour).
What is Systems Analysis?
It involves viewing any part of the physical or human as a entity that consists of stores and transfers of energy and matter, and operates because it receives a constant supply of energy and matter, which in turn are lost from the system as outputs. Changes in the level of inputs may cause instability within the system, and in response to the new amounts of energy, the system initiates feeback processes. The snowballing effect may ultimately cause a shift in the system to a new state of equilibirum.
What is the Glacier Mass Balanace?
Glaciers gain mass in the accumulation zone, i.e. the upper part of the glacier where input (winter snowfall etc) exceeds output (summer melting etc). Mass is lost in the lower ablation zone where outputs exceed inputs. At the transition between the two zones accumulation equals ablation. This boundary is called the equilibrium line, which in turn approximately coincides with the position of the snowline. The gains and the loses of ice experienced by a glacier constitute its mass balance or glacial budget.
How is Glacial Ice Distributed?
-In the South Pole there is more present day ice coverage and less late pleistocene ice sheets -> hasn’t reduced as much.
-In the Northern hemisphere there is a lot more of the lat pleistocene ice sheet have melted -> around northern Europe (Russia, the UK and Skandinavida).
-The late Pleistocene ice sheet in South America have all melted.
-The Laurentide and Cordilleran ice sheets covered east and west of North America stertching around 3000 km in width.
-Major ice extentsions were over North America and Europe (this grew to a thickness of around 3000-4000 m).
-At present, ice covers over 10% of the Earth’s land area which accounts for 75% of the world’s freshwater (about 1.8% of all water on Earths).
-Ice covers at the Pleistocene maximum was more than 3x greater than the present day.
-About 85% of all current glacier ice is contained in Antarctica.
What are the Factors affecting Ice Mass Distribution?
-Latitude
-Altitude
-Aspect
How does Latitude Affect Ice Mass Distribution?
Particulary important fro polar ice masses. In high latitude the sun’s rays hits the ground at a lower angle, so the solar energy received must heat a larger area.
How does Altitude Affect Ice Mass Distribution?
Particulary important for alpine glaciers. High altitudes are impacted by the environmental lapse rate (ELR) whereby tempertaure decline by 1°c for every 100m above sea level.
How does Aspect Affect Ice Mass Distribution?
This can determine the amount of snow falling and where it settles. In the northern hemisphere, north and east facing slopes are both more sheltered and shadier.
What are Periglacial Environments?
Refers to non-glacial cold environments, which are characterised by periods of extreme cold, dry conditions.
They are also referred to as the tundra - a term describing the treeless vegetation of dwarf shrubs, grasses, lichens and mosses.
What are is Permafrost?
-Permafrost is permanently frozen ground where subsoil temperatures remain below 0°c fro at least two consecutive years.
-Around 20% of the Earth experiences periglacial conditions - mainly in the northern hemisphere. During the Pleistocene glaical periods, this was higher at 33% and at much lower latitudes than today.
What is Continuous Permafrost?
Forms in the coldest areas of the world where mean annual temperatures are below -6°c. It is found at the highest latitudes. It can extend downwards for hundreds of metres.
What is Discontinuous Permafrost?
It is shallower and permanently frozen ground is fragmented by patches of unfrozen ground (talik). The surface layer of the ground melts during the summer months.
What is Sporadic Permafrost?
It occurs where the mean annual temperature is only just below freezing and permafrost covers amounts of less than 50% of the slandscape.
What is Isolated Permafrost?
It occurs when less than 10% of an area is affected.
How does Snow Change in a Glacier?
-Snow falls on the 1st layer and collects on the glacier. Fresh layers of snow fall each day and build up.
-As snow becomes compacted it starts freezing together on the 2nd layer, becoming quite granular -> this is called granular snow.
-As the granular snow becomes increasingly compressed it forms névé or firm on the 3rd layer.
-As the snow layers increase and the process continues and the layers become deeper. The névé (or firm) transforms into glacier ice on the 4th layer.
What affected rates of Accumulation and Ablation?
-Amount of precipitation
-Average temperatures
-Levels of solar insolation
-Levels of wind speed
-Latitude
-Continentality (distance from the sea as seas/waters are warmer influencing temperature around glaciers/permafrost).
What are the Short Term Affected of variation in Glaciers?
Positive and negative regimes
-A positive regime is when the glacier is increasing in mass i.e. accumulation exceeding ablation during the winter period.
-A negative regime is when the glacier is decreasing in mass i.e. when ablation exceeds accumulation during the summer.
What are the Long Term Affected of variation in Glaciers?
Trends and Glacier Health
-Trends van be summarised over a decade from annual net balance.
-These long term trends determine the ‘health’ of a glacier and whether it will significantly advance or retreat and if thinning/retreating contributes to increased concerns over global sea level rises.
-Currently it’s estimated that nearly 75% of the world’s ice masses are experiencing ‘rising trends’ in their net negative balances.
What is Net Balance?
The difference between the accumulation and ablation.
Cumulative is the difference added overtime.
What are Negative Feedback Cycles?
-A negative feedback cycle acts to minimise the effect of new inputs in order to regain stability and equilibrium.
-E.g. if there is more snowfall, the glacier would advance (grow) meaning more ice would enter the ablation zone so more snowmelt would occur.
-This would mean that a balance would be gained whereby the input of snowfall would equal the output of snowmelt.
-The system remains balanced.
What are Positive Feedback Cycles.
-A positive feedback cycle amplifies the effects of an input which would cause a shift in the system.
-E.g. if a glacier has a positive mass balance and the glacier surface area is increasing, there will be an increase in ice albedo. This will cause a further reduction in air temperature, thus increasing accumulation and initiating a positive feedback cycle in which the glacier will continue to advance (this works the other way round too).
-The system will not be balanced.
What is the Greenland Ice Sheet Casestudy?
-One of the world’s two remaining ice sheets.
-Covers an area of 1.7 million km².
-It conatins more than 2.5 million km³ of stored ice.
-In the centre, ice is 3 km thick which depresses the earth’s crust by 1km in depth.
-A number of changes have occured to the mass balance of the ice sheet recently.
-Accumulation of snowfall in the central area is +520 km
-Ablation of melting and edges is -290
-Ablation by calving icebergs is -200
-Ablation of sublimation is -60
-Total ablation is -550
-Mass balance is -30
