Environmental Processes and Change: The Global System
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Course
Geography (GEOG10401)
Institution
The University Of Manchester (UOM)
Overview
What caused the ice ages? How can long-term tectonic processes change the global climate? Why should we think about river basin processes at the global scale? How does vegetation influence climate? Has the Earth ever been in a Snowball state? What role do volcanoes play in the climate sys...
GEOG10401 – Environmental Processes and Change: The Global System
Week 1 – The earth system and drivers of global change
Components of the earth system
• The 5 components of the earth system are: atmosphere, lithosphere, biosphere,
hydrosphere and cryosphere
• Environmental processes create change
• For processes to operate, energy is needed to drive the system and cause the
components to interact. The majority of the energy comes from the sun
• Time and scale are considered in the global system:
- Spatial scale involves thinking from short-term (seconds, days or years) to long-term
(thousands or millions of year) scale
- Temporal scale involves thinking from local to the regional to the continental to the
global scale
Climate change
• People became aware the earth’s climate has changed, starting from an early idea of
the earth being a big hot molten rock and has since cooled down
• Through further research of fossils, Curvier demonstrated extinction in the geological
record and studied the Adams Mammoth (which was discovered in 1799 in the River
Lens delta), and identified the specie being adapted to living in the frozen north due
to it being woolly and fatty, and this specie no longer exists on this earth
• He therefore recognised a major climate change must have occurred, because the
same fossil was also found on continental Europe and regions of temperate climate
(regions with temperatures that’s not extremely hot or cold, in which most have the
four seasons). As a result, the past climate must have been much colder
Extreme events
• Extreme interactions between components can cause extreme events
• E.g. landslides – interaction between the hydrosphere and the lithosphere, and
wildfires – interaction between the biosphere and the climate
Sources of energy for earth surface processes
Two major energy sources
External energy – solar radiation
• 17.8 x 1016 W of radiation energy reaches the upper atmosphere, in which 30% is reflected
back into space
• The remainder 70% heats up the atmosphere and the earth’s surface, which creates an
average global surface temperature of 15°C
• About 33% of this heat drives the hydrological cycle and the many surface processes
,Internal energy – of the earth
• The earth’s internal heat drives tectonic processes and movements
• Radioactive decay is a major source of geothermal heat that drive tectonic processes
• Heat flow to the surface of the planet due to the long-term cooling of the earth
(because heat rises to cooler areas, while if the whole area is the same – heat
wouldn’t rise)
Exogenic and endogenic processes
• Exogenic processes refers to external processes and phenomena, such as flooding,
erosion and glacial processes
• Endogenic processes refer to internal processes and phenomena, such as tectonic
movements, earthquakes and volcanoes
• Landforms formation are created from the interaction between exogenic and
endogenic processes
• Solar radiation & gravity (because gravity is also a factor, especially in mountainous
area) drive exogenic processes, such as weathering and erosion
• Internal energy drive endogenic processes, such as plate tectonic, volcanic activity
and seismicity
Redistribution of heat around the planet
• There’s more heat in the low latitude – equatorial region, while cooler air in the high
latitude – polar region. Therefore, between the low latitude and the high latitude
regions, there’s strong thermal gradient
• Nature tries to redistribute and move the excess energy around the planet, from the
low latitude to the high latitude, by moving the heat around the planet via
atmospheric processes (mainly) and ocean currents
Global heat flux (movement) in the ocean – thermohaline circulation
• Thermohaline circulation is a major dominate ocean current, it’s a fundamental
feature of the climate system
• Thermohaline refers to temperature and salinity (as it influences the density of the
water)
• Solar heating warms the ocean in the low latitude, such as the Mid-Atlantic, Mid-
Pacific and Indian Ocean.
Temperature-driven variations in
water density and salinity produces
major flows and currents
• The major flux of water up to the
northern hemisphere which make the
climate temperate (mild temperature),
is called the Gulf Stream. In the north
Atlantic, there’s warm current moving
into the north to the middle of the
, high latitude (in the west coast of Europe and Greenland). The water cools down in
the winter time and so a lot of evaporation occur, which causes the water to get
more denser and saltier. This results in the water sinking to deeper levels, creating a
bottom southwards flow, whereby the water gets reheated as it flows south. This is
known as North Atlantic Deep Water.
Therefore, changes in thermo energy and salinity of the water drives the system
• The UK has similar latitude to Toronto and Moscow, however the climate in the UK is
temperate, while the temperature in Canada and Moscow in the winter is extremely
cold. This is due to the Gulf Stream, as it brings warm temperate water off the coast
of UK
Geography of tectonic plates being key influence of global climate
• Tectonic activity can create landforms, for example at the constructive plate
boundary mountain ranges can be create, which influence the movement of air
masses and how the continental region will be heated, because high elevated land
can be heated in the summer time and influence the monsoon climate
• The geography of the tectonic plates is a key influencer on the global climate
because:
- The tectonic processes influence the form and size of the ocean basins and land
masses, in which the thermohaline circulation is conditioned by the geography of the
continent and ocean basin. Therefore, it influences the movement of heat/energy
transfer around the planet via by the ocean, which influence the climate.
Tectonic processes which has changed dramatically overtime in the earth’s history
where there has been super continent and continent being different places
- Furthermore, tectonic processes can create large areas of uplifted land, creating a
plateau and high elevation of mountain chains, which get heated up in the summer
and draw in moisture from around it. This influences large-scale atmospheric
circulation and vertical heat exchange. Therefore, it influences continental scale
patterns of atmospheric motion and energy, and therefore the climate.
- Moreover, tectonic processes influence the amount of elevated crust, which is an
important control on global patterns of weathering and erosion – the location and
elevation of mountain chains and high plateau landscapes across the earth’s surface
is a key influence on climate over a range of timescales
- Other endogenic processes include volcanoes, they influence the climate because it’s
a supplier of CO2, ash and aerosols to the atmosphere which usually has short-term
impact on the climate
, Four main tectonic processes that influenced global climate in the “Last Great Cooling”
• There are 4 main examples from the recent geological past, of where particular type
of tectonic processes set in motion a cascade
of processes in different scale, which has
influenced the global climate:
- Asia
- Antarctica
- The Mediterranean
- Central America
• The earth has gone through a sequence of
hothouse (when the climate has been
warmer than presence, where there has been no glacier on any continent of the
planet) and icehouse (when the climate has been cooler than presence, where there
has been a very active cryosphere and extensive glaciation)
• This has much been governed by the changes and the concentration of CO2. So,
when there’s high levels of CO2, the planet was warmer, while when there’s low
level of CO2, the planet was colder
• In the past geological years, there has been a long-term change of high and low CO2,
which may have been influenced by volcanic activity producing CO2 and weathering
processes which reduces the amount of CO2 in the atmosphere
• The diagram below of the sequence from icehouse to hothouse is a very generalised
progression of change over the past 500million years, because there have been
periods of rapid changes
• The long-term driver of change is the composition of the atmosphere – the CO2
content of the atmosphere (and methane at different times)
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