Water + Carbon

• Water Stores:
  - Atmospheric water - water found in atmosphere; water vapour with some liquid + crystals
  - Cryospheric water - water locked up as ice  
  - Hydrosphere - discontinuous layer of water near the surface of Earth. Includes all liquid and      frozen surface water, groundwater and atmospheric water vapour.
  - Oceanic water - water in Earth’s ocean + seas (72% of Earth’s surface is oceanic water)
  - Terrestrial water - groundwater, soil moisture, lakes, wetlands, rivers
  
  

• Periglacial Environments:
  - Found in areas of high altitude and latitude
  - Experience intense frosts during winter and snow-free ground in summer
  - Large anticyclonic continental polar air masses responsible for cold & dry conditions
  - Temperatures fluctuate ENOUGH for freeze/thaw cycle to take place. CRUCIAL for processes to operate, shape the landscape. 
  - Waxing & waning of ice = location is ever-changing in congruence with (inter) glacial cycles

• Water in the Atmosphere:
  - Increase in atmospheric water vapour → increase in rising temperatures
  - Evaporation happens when energy from solar radiation hits surface of water/land
  - Humidity and temperature of air, solar energy and availability of water are all factors
  - Absolute humidity is the measure of water vapour (moisture) in the air, regardless of temperature. It is expressed as grams of moisture per cubic metre of air (g/m³).
  - Relative humidity measures water vapour but RELATIVE to the temperature of the air. Expressed as amount of water vapour in the air as % of total amount that could be held.
  - Advection Fog: warm air moves over cooler surface and its temperature drops
  - Radiative Fog: heat radiating from surface at night cools bottom air to form fog at surface

• Thermohaline Ocean Circulation:
  - TOC is driven by density differences of water (density depends on temperature and salinity)
  - Salinity and temperature differences arise from heating/cooling at sea surface
  - Evaporation & sea ice formation enhance salinity; precipitation, run-off & ice-melt decrease it
  - Wind driven currents are confined to surface waters, while TOC is not
  - Thermohaline consists of deep water formation and spreading of deep waters (supplies heat to polar areas)
  - Also upwelling of deep water and near-surface currents (required to close the flow)
  
  

• El Nino
  - Warming of ocean in Southern Pacific, resulting in changes in atmosphere
  - Warming of sea surface, often followed by La Nina (cooler than usual)
  - An El Niño occurs when sea surface temperatures are 0.5℃ (or more) above average
  - Water stores heat for longer, wind has less strength and can even change direction
  - ENSO = El Nino Southern Oscillation (has three phases: El Nino, neutral, La Nina)  
  - El Nino: trade winds die down, rain clouds over Peruvian coast. Warmer coastal waters have less nutrients and affect fisheries. 
  - Neutral: fisheries supported by upwelling bringing nutrients from depth.
  - La Nina: Very strong trade winds. Upwelling of cold water from deep ocean contributing to lower sea temperatures. 
  - 2015-16 El Nino was one of the strongest ever recorded, covering an extremely large area
  - Caused cyclones, floods + failed harvests & reached category 5 on Saffir-Simpson several times
  - Pool of warm water hovering around equator caused strong El Nino ( → weak La Nina)
  - Can also affect global carbon cycle as wildfires are caused, releasing CO₂ 
  
  

• Flood Hydrographs
  - Terms in dictionary below

Human Impact on Hydrological Scale
- Cloud Seeding: strategy to encourage precipitation
  Silver iodine particulates released into atmosphere, act as hygroscopic nuclei (required for rain)
  Water vapour gathers around particulates until they are heavy enough to fall
  Can generate rain/snow, balances water supply + demand (happens in Idaho, USA)

- Deforestation: trees get cut down for human use
  Lack of trees mean less interception & increased overland flow (less lag time) and flooding risk

- Natural Flood Management: constructing things to combat floods
  Constructed low-level bunds (soil embankments), planted more trees (benefits locals + wildlife)
  Restored woody debris dams in small streams and restored wetlands to increase interception

- Urbanisation: movement of people into urban areas
  Increased abstraction from aquifers means ground subsidence (New Mexico)
  Building of homes on floodplains and removal of wetlands increases flood risk

- Afforestation: replanting trees
  Reduces carbon footprint, increased levels of interception
  However, in Ireland, sitka spruce is being planted - good for carbon capture, but bad for local   ecology, as it has a shallow root system, which means reduced infiltration. Increased flood risk.

- Grand Ethiopian Renaissance Dam:
Produces hydroelectric power, feeds into the national grid of Ethiopia. May lead to more erosion.
Increased evaporation rates + rise in surrounding water table. Alleviates potential flooding.

- Ogallala Aquifer, USA:
Covers 450,000 square km. Made of aeolian + fluvial sediments (high porosity + permeability)

• Carbon Stores:
  - CO₂  originates in Earth’s interior, stored in the mantle. Escapes at constructive/destructive plate boundaries.
  - Carbon sequestration: process by which carbon sinks remove carbon dioxide
  - Atmosphere: layers of gases enveloping planet.         Cryosphere = ice      
  Lithosphere: solid, outer part of Earth (Earth’s crust)   Hydrosphere = water 

• Slow Carbon Cycle:
  - Takes up to 100-200 million years
  - Natural and artificial carbon sinks remove CO₂ from the atmosphere
  - Geologic: separation and capture of carbon at point of emissions, followed by storage and deep underground geologic formations (Carbon Capture and Storage)
  - Biologic: net removal of carbon from atmosphere by plants and microorganisms
  - Burial and compaction, chemical weathering
  
  1.  Movement of carbon from atmosphere to lithosphere (rocks) begins with rain. Atmospheric carbon combines with water to form carbonic acid that falls to the surface in rain.
  Acid dissolves rocks and releases calcium, magnesium, potassium, or sodium ions. Rivers carry ions to the ocean.
  
  2. In the ocean, the calcium ions combine with bicarbonate ions to form calcium carbonate. Over time, layers of shells and sediment are cemented together and turn to rock, storing the carbon in stone (limestone).
  
  3. Only 80% of carbon-containing rock is currently made this way. Remaining 20% contain carbon from living things (organic carbon) that have been embedded in layers of mud. Heat and pressure compress the mud and carbon over millions of years, forming sedimentary rock such as shale.
  
  4. The slow cycle returns carbon to the atmosphere through volcanoes. Earth’s land and ocean surfaces sit on several moving crustal plates. When the plates collide, one sinks beneath the other, and the rock it carries melts under the extreme heat and pressure. The heated rock recombines into silicate minerals, releasing carbon dioxide.
  
  5. Chemistry regulates this. If carbon dioxide rises in the atmosphere because of an increase in volcanic activity, for example, temperatures rise, leading to more rain, which dissolves more rock, creating more ions that will eventually deposit more carbon on the ocean floor.
  Takes a few hundred thousand years to rebalance the slow carbon cycle through chemical weathering. Creating Dynamic Equilibrium.
  
  
  

• Carbon in the Ocean:
  - Vertical Deep Mixing: Upward and downward movement of water in the ocean as a result of temperature difference
  - Phytoplankton: plant, performs photosynthesis so takes in CO₂
  - Has a physical and biological carbon pump
  
  Physical Carbon Pump:
  
  1.  Cold Polar ocean water can dissolve more than twice as much CO₂ than in warm equatorial waters.
  2.  Means that as major ocean currents move waters from tropics to poles, they are cooled, can take up more CO₂ from the atmosphere
  3.  As water is cooled, they head to high latitudes, they become denser and sink into deep ocean, taking accumulated CO₂ with them.
  4.  Water returns along ocean bed to tropics, where it upwells, warms and releases some CO₂ back into the atmosphere. Cycle repeats.
  
  Biological Carbon Pump:
  
  1.  Growth of marine plants, such as phytoplankton, take CO₂ and other chemicals from sea water to make plant tissue. Happens in upper layers of ocean as photosynthesis requires light.
  2.  Most of CO₂ taken up by phytoplankton is recycled near the surface; a substantial fraction (30%) sinks into the deeper waters, before being converted into CO₂ by marine bacteria
  3.  Only 0.1% reaches seafloor to be buried in sediments.
  
  - The pH of surface water has fallen by 0.1pH (30% more acidic)
  - Bad for organisms, which have alkaline shells
  - Rising temperatures of oceans mean they are less able to absorb CO₂ emitted by humans
  
  

• Fast Carbon Cycle:
  - Chemical weathering: carbonic acid reacts with unstable rock.
  - Ions such as potassium, sodium are released from the rocks and enter the ocean.
  - Calcium ions combined with bicarbonate ions form calcium bicarbonate
  - This is absorbed by plankton, corals and other shell building creatures. Restored in lithosphere.
  
  

- Photosynthesis, Respiration, Decomposition, Combustion
- Transfers + flows on plant, sere and continental scales. (Sere = community of plants at any stage of succession)
- Photosynthesis occurs in all plants, takes in CO₂ and forms oxygen and glucose
- Respiration takes in oxygen and releases CO₂, happens in all organisms. (Animals release methane (CH₄))
- Decomposition is the breakdown of organic matter by fungi/bacteria (decomposers)
- CO₂ is released during decomposition
- Is heavily temperature-dependent and presence of water is also key (warmer temp = more microbial activity)
- Combustion: when organic material burns, carbon is released as CO₂.
- Occurs naturally by wildfires caused by lightning strikes. Human activities cause significant amount of combustion: burning fossil fuels such as coal, oil, gas leads to net CO₂ increase
- Volcanic Eruptions: huge amount of volcanic gas, aerosol droplets and ash are released
- Sulfur dioxide can cause global cooling, volcanic CO₂ can promote global warming
- Negative Feedback in Carbon Cycle: increased photosynthesis by plants and increased global temperatures allow vegetation to grow in new areas. This vegetation absorbs CO₂ for photosynthesis, decreasing warming effect.
- Negative Feedback 2: Higher CO₂ levels cause more phytoplankton to grow. CO₂ taken in through photosynthesis, decreasing phytoplankton levels. 

- Positive Feedback: increased temp → ice melts → release more CO2 → increased temp