EQ1 - How has climate change influenced the formation of glaciated landscapes? Flashcards
In what epoch was the most recent major ice age?
Pleistocene epoch
- spanned from 2.5m to 11,700 years ago
What is a glacial period?
Where colder temperatures cause glacial advances
- sea levels fall
What is an interglacial period?
Where warmer temperatures cause glacial retreats
- sea levels rise
What was the name of the most recent period of glacial advance (around 21,000 years ago) ?
Last Glacial Maximum
During the last Glacial Maximum, a large area of the northern hemisphere was covered by ice sheets (including the UK)
True or False?
True
The world is currently in a glacial period - naturally, over time temperatures will drop and glaciers will advance.
True or False?
False - we are in an Interglacial period
- temperatures are higher and most glaciers are retreating
What can be used to evidence temperature fluctuations during glacial/interglacial periods in the past?
Ice Cores
How do ice cores show temperature fluctuations?
They reveal atmospheric gas concentrations over time
- this can be used to determine atmospheric composition and temperature
What is the name of the epoch that began 11,700 years ago?
Holocene epoch
Define an ‘Icehouse’ phase
Period of long-term cooling and presence of polar ice
- as experienced in the Pleistocene
Define a ‘greenhouse’ phase
Period of higher global temperatures where ice is minimal
e.g during Cretaceous period
What is the most significant long-term driver of climate change?
Milankovitch cycles
What are Milankovitch cycles?
Changes in the earth’s orbit and axial positioning, affecting the distribution of solar energy across the planet
Name the 3 components (types) of Milankovitch cycles
- Eccentricity
- Axial tilt
- Precession (wobble)
In ice cores, what does low concentrations of carbon dioxide suggest?
A glacial period
- interglacial usually high CO2 (as much warmer)
Though the Pleistocene is considered a ‘single ice age’, there were actually multiple periods of glacials/interglacials within it
True or False?
True
What are stadials and interstadials?
Short-term fluctuations within ice-house/greenhouse conditions
- stadials are intense cold
- interstadials are relative warmth
What is eccentricity?
The variation in the path of the earths orbit
- either more elliptical or more circular
How long do cycles of eccentricity typically last?
Around 100,000 years
How does Eccentricity affect global climate?
Changes the amount of solar radiation received by the Earth
What is Axial tilt?
The angle in which the earth rotates on
What is the range of which axial tilt varies?
Between 21.8 - 23.4 degrees
How does axial tilt affect climate?
Changes the intensity of sunlight received at the poles
This affects seasonality of climate - (greater the tilt, greater the difference between winter and summer)
What is Precession (wobble)?
How the earth wobbles on it’s axis (like a spinning top)
How does precession affect climate?
The wobble of the earth on it’s axis changes the point at which it is closest to the sun
- this can cause long term changes to when different seasons occur along the Earth’s orbital path
How long does a cycle of Eccentricity last?
100,000 years
How long does a cycle of Axial tilt last?
41,000 years
How long does a cycle of Precession (wobble) last?
21,000 years
What occurence seems to support Milankovitch’s theory that orbital variation heavily impacts solar radiation/climate?
Glacials seem to have occurred at regular intervals of 100,000 years
(the same length as each eccentricity cycle)
What is the actual impact, in Degrees Celsius (‘C), that Milankovitch cycles have on global temperatures?
Only change temperatures by 0.5-1’C
What mechanism is used to explain large temperature changes (more than +/- 5’C) in history?
Climate Feedback Mechanisms
Many scientists see Milankovitch cycles as a possible ‘trigger’ for major glacial/interglacial periods, but NOT as the driving factor.
True or False?
True - it is climate feedback mechanisms which sustain the process
Explain positive and negative feedback effects?
Where a small change is either amplified (positive) or diminished (negative)
What effect does an increase in snow/ice have on the Earth’s surface albedo (reflectivity)?
Raises surface albedo (reflectivity), so more solar energy reflected back into space
Is the albedo effect an example of positive or negative feedback?
POSITIVE Feedback - more solar energy reflected leads to further cooling
How does the melting of snow/ice due to CO2 emissions create a positive feedback loop?
It decreases albedo effect + releases methane from melted permafrost
How do increasing global temperatures affect evaporation and cloud cover? (negative feedback)
More evaporation leads to more cloud cover
Cloud cover reflects solar energy back to space, diminishing warming
- This process is known as global dimming
How do ice sheet dynamics affect thermohaline circulation (THC) and global temperatures?
Warming water in the Arctic disrupts ocean currents, reducing the flow of warm water from Gulf Stream to Northern Europe
- Potentially leading to cooling in this region
What is ‘calving’?
The breaking up of chunks of ice at the glacier snout/ice sheet to form icebergs
- Occurs as the glacier reaches a lake or ocean
What is the Thermohaline Circulation?
Global system of surface and deep-water currents
- known as the ‘ocean conveyor’
What are currents in the Thermohaline circulation driven by?
Differences in temperature (thermo) and salinity (haline), between areas of the oceans
What 2 factors have been responsible for short-term fluctuations in climate?
- Solar Forcing
- Volcanic Activity
What causes the amount of energy emitted by the Sun to vary?
The number/density of Sunspots
What are Sunspots?
Dark spots on the surface of the sun
- they affect the amount of energy emitted by the Sun
- Caused by intense magnetic storms
What was the ‘Maunder Minimum’ (1645-1715), coinciding with the height of the Little Ice Age?
A long period with no Sunspot activity
Despite the ‘Maunder Minimum’ phenomenon, what is the actual % variation in solar radiation caused by Sunspot activity?
0.1%
- Suggests that sunspots alone are insufficient to explain climate fluctuations
What % of 20th century global warming do scientists attribute to solar output variation (sunspots)?
20%
How do large volcanic eruptions impact global climate?
Released substances such as ash, sulphur dioxide and CO2 are recirculated globally by high-level winds
What was the decrease in global temperature in the 2-3 years following an eruption releasing 200m tonnes of sulphur dioxide in Indonesia, 1815?
Temperatures dropped by 0.4 - 0.7’C
- caused short-lived global cooling
Define the ‘Cryosphere’
Parts of the Earth’s crust and atmosphere subject to temperatures below 0’C for at least part of the year
What type of ice mass?
Complete submergence of a regional topography
Ice Sheet
What type of ice mass?
Smaller type of ice sheet occupying upland areas
Ice Cap
What type of ice mass?
Ice covering an upland area, but not thick enough to bury topography
Ice field
What type of ice mass?
Glacier confined within valley walls and terminating in a narrow tongue
Valley Glacier
What type of ice mass?
Valley glacier which extends beyond the end of a mountain valley into a flatter area and spreads out like a fan
Piedmont Glacier
What type of ice mass?
Smaller glacier occupying a hollow on the mountainside - carves out a corrie or a cirque
Cirque Glacier
What type of ice mass?
Large area of floating glacier ice extending from the coast where several glaciers have reached from the sea
Ice shelf
What 2 categories are glaciers traditionally divided into?
Warm based (temperate) or cold based (polar)
Where do warm based (temperate) glaciers usually form?
High altitude areas outside the polar region (e.g the Alps)
Where do cold based (polar) glaciers usually form?
High latitude areas (e.g Greenland)
Describe the temperature of a) the surface b) the base of warm based (temperate) glaciers?
Surface seasonally fluctuates above/below melting point
Closer to base usually close to melting point (warmer)
What 3 factors cause basal ice in temperate glaciers to melt continuously, despite the temperature being below 0’C?
- Pressure of overlying ice
- Geothermal energy (from valley floor)
- Percolation of meltwater
Why is the average temperature of ice in polar glaciers much lower than 0’C?
The surface temperature is extremely cold (-20 to -30’c) and geothermal heat is insufficient to raise basal ice temp. to 0’C (melting point)
Why is meltwater percolation NOT present in polar glaciers compared to temperate glaciers?
The polar summer is short and still very cold - meltwater from surface is minimal
What % of the world’s freshwater is locked up in ice?
75%
- however this counts for only 1.8% of ALL water available on earth
Why are high latitude (polar) glaciers much colder?
Suns rays hit the ground at a lower angle, so the solar energy received has to heat a larger area
What impacts the temperature of high altitude (alpine) glaciers?
Environmental Lapse Rate (ELR) - temperatures decline by 1’C for every 100m
How many times greater was ice cover at the Pleistocene Maximum compared to today?
3x
The Antarctica and Greenland ice sheets historically covered a far greater area than they do today.
True or False?
False - ice sheet area cover there has only slightly decreased
What is the range of average annual temperatures often experienced in a Periglacial climate?
1’C to -4’C
For how many months of the year is the temperature below -10’C in a typical periglacial climate?
6 months of the year
How many mm of precipitation is common per year in periglacial climates?
Under 600mm per year - very low
What % of the Earth’s land surface experiences periglacial conditions in the present day vs the Pleistocene?
Around 20% (Present Day)
33% (Pleistocence)
True or False?
During the Pleistocene, areas of lower latitude experienced periglacial conditions
True - included areas such as Southern France and the Balkans
