Geography - Earth's Life Support Systems

How does water help regulate the climate

Oceans - absorb, store and slowly release heat, Benguela current takes cold water away from the poles and North Atlantic Drift takes warm water towards the poles

Clouds - ice crystals reflect around 1/5 of incoming solar radiation

Water vapour - absorbs some outgoing long-wave radiation, keeps global climate 15 degrees higher than otherwise

Uses of water for humans, flora and fauna

Humans - makes up 65-95% of all living organisms, medium for all chemical reactions in the body, food production is water intensive - used to irrigate crops, drinking water and sewerage services are crucial to global health

Flora - needed in photosynthesis to make glucose and starch, required to remain rigid, transports mineral nutrients in soil

Fauna - fur covered animals cool by panting, respiration releases water vapour

Water importance facts

70% of earth is covered in oceans

global population is increasing by 1.1% each year

humans consume 4 million metric tonnes of water a year

Water cycle key terms

Evaporation, condensation, precipitation, throughfall, interception, stemflow, plant uptake, overland flow, saturated overland flow, infiltration, percolation, groundwater flow, throughflow, transpiration, evapotranspiration, sublimation

Define dew point

Critical temperature at which condensation occurs - latent heat released as changes state, less dense than surrounding air as it spreads apart, so thence rises

Environmental lapse rate

the rate at which temperature decreases as you rise through the troposphere

6.5 degrees per km

This is as the air is unsaturated

Adiabatic Lapse rates

The change in temperature of a contained parcel of air due to a change in its pressure - no exchange of heat with surroundings

Dry ALR - around 10 degrees per 1000m

Saturated ALR - around 5 degrees per 1000m

Stable vs unstable parcel of air

Stable - if the parcel is the same temp as the surrounding environment it will stop rising and eventually sink

Unstable - if the parcel of air is warmer than the surrounding environment and continuing to rise

SLOW carbon cycle

1. CO2 dissolves into the oceans

2. Marine organisms such as clams and corals, fix it into calcium carbonate to use for their shells and skeletons

3. When they die they settle on the ocean floor, over millions of years heat and pressure convert them into sedimentary rock where they lie for 150 million years

4. This rock is sometimes subducted into the upper mantle at tectonic plate boundaries where it is vented into the atmosphere by volcanic eruption

5. Otherwise it is brought to the surface and chemically weathered

6. Partly decomposed organic material may also be buried beneath younger sediments to form carbonaceous rocks which then act as carbon sinks - fossil fuels

FAST carbon cycle

Phytoplankton or land plants absorb atmospheric CO2 and combine with water to make carbohydrates

Respiration does the opposite, releasing CO2 back

Decomposition of dead organic matter also releases CO2 back into the atmosphere

Also carbon exchange at ocean surface - atmospheric CO2 dissolves into ocean which releases CO2 (through this individual carbon atoms are stored through natural sequestration for around 350 years)

Importance of carbon

1. Structural/building material - backbone of organic molecules

2. Energy storage - stores chemical energy in glucose, starch fats. Photosynthesis captures solar energy

3. Greenhouse gas / climate regulation - absorbs heat maintaining earth average temperature

4. Energy and industrial use - fossil fuels, heat, electricity, transport

Key stores for carbon

Lithosphere - >99.9%, shells of old sea creatures

Hydrosphere - 0.038%, 50x more than atmosphere, dissolved in sea water as bicarbonate

Fossil fuels - 4000 billion tonnes - 0.004%

Pedosphere

Atmosphere

Biosphere

What is upwelling and how is it affected by temperature

Bringing cold water to the surface - carbon dissolves more readily at lower temperatures

Key terminology carbon cycle

respiration, oxidation, weathering, combustion, decomposition, photosynthesis, volcanic activity, ocean-atmosphere gas exchange

Biological pump vs physical pump

Biological - phytoplankton photosynthesise using the dissolved CO2 in the water, transferring to the biosphere and then the lithosphere meaning carbon moves from the fast to the slow carbon cycle

Physical - downwelling and upwelling, cold water absorbs more carbon - absorbs then sinks allowing more absorption

Key facts Amazon

6,000,000 km2 of area

6692km - Amazon River

50% of all tropical rainforest in the world

2200g/m2/yr - net primary productivity

20% lost to deforestation since 1970

recycles 50-60% of its water

25% of evaporation happens from leaves

Geology in the Amazon

A large area of southern Brazil is covered by the impermeable crystalline Brazilian Shield, meaning there is minimal water storage and lots of run off

Relief in the Amazon

Lowland area surrounded on all sides by higher relief meaning it acts as a funnel for South America - 1,100 tributaries into the Amazon

In areas of gentle relief there is a lot of infiltration and percolation, but in areas such as the Andes in the west, steep catchments make rapid run-off and reduce infiltration rates, increasing overland flow

Temperature in the Amazon

Does not fall below an average of 25 degrees all year - <3000mm of precipitation in march, leads to high evaporation and levels of atmospheric humidity and hence thunderstorms and precipitation

Madeira Basin

Largest tributary basin of the Amazon River, covers over 1.3 million km

upper reaches are up to 6000m above sea level in the Bolivian Andes

How does high relief in Madeira Basin affect water cycle

Low temperatures - snow and ice packs locks water in cryosphere, more sublimation and more seasonal water fluctuations in surrounding rivers

Harsh climate and thin soils - little vegetation and so little interception and transpiration

Exposed rock - decreased infiltrations

Steep slope angles - less infiltration and percolation but more overland flow

Facts for the Amazon carbon cycle

400-700 tonnes of biomass per hectare

2.4 billion tonnes of carbon absorbed per year

NPP 2500g/m2/year

trees can reach heights in excess of 48m

rapid decomposition rate due to climate

Limestone is more than 50% calcium carbonate - weathering thus releases more carbon into the atmosphere

Causes for deforestation

70-80% of the land use is cattle ranching - In 2019 Brazil contributed 14% to global beef supplies

Mining - illegal mining increased by 25% between 2018-2019

Road building - 95% of forest clearance is near to transport networks, also could compact soil

Urbanisation - between 1980-2000 Brazil urban Amazon population almost tripled from 4.7 million to 13.7 million

Forest fires - could become a carbon source, humans start 99% of the fires

Soya cultivation - linked to cattle farming as main source of feed, reduces inputs of organic material into the soils

Management - protecting primary forest

62.44% of forest is currently under some sort of conservation

80% is being conserved by 2030

Carbon credit financing pays indigenous tribes to stop logging - in 2013, Natura (a large TNC) paid the Surui people to purchase 120,000 tones of carbon credits

Management - restoring degraded areas

2015 Paris Agreement pledged to restore 12 million He of forest

progress has been slow due to changing political landscape, COVID-19 and wildfires and they were only 20% towards target in 2023

cannot reliable reproduce the biodiversity of primary forest

Management - changing agricultural practises

integrated land management - rotational cropping, annually alternating arable crops with livestock means you avoid soil fertility by preventing nutrient depletion and allowing manure to be returned to the soil

Recreation of Terra Preta - ancient Amazonian soils enriched with charcoal, compost, human waste and organic residues which support long term fertility - could allow permanent, sustainable cultivation