WATER AND CARBON CYCLES

• Morphological systems


  The simplest form of system, in which some of the component parts or elements are identified, and the links between them are shown
• Morphological systems


  • They allow geographers to investigate the functioning of certain elements within a drainage basin, and the interrelationships within it, albeit in a simplified form
• Cascading system


  Characterised by the way energy or matter flows through it, consisting of stores and flows
• Stores


  Locations where matter or energy is held in a system
• Processes


  Actions or series of actions that achieve a particular result
• Transfers


  Change in location in a system
• Transformations


  Changes in the state of the components of a system or a change of energy
• The water cycle and carbon cycle are both cascading systems
• Process-response system


  Integrates characteristics of both morphological and cascading systems, used to analyse interactions between movements of energy or matter and changing environmental components
• The drainage basin hydrological cycle is an example of a process-response system
• Dam construction has both intentional and unintentional systematic impacts on the hydrological and fluvio-geomorphological effects
• Increased evaporation losses, thermal stratification, increased water loss through seepage, seismic stress, and deposition and sediment infilling are some of the impacts of dam construction
• The carbon cycle flows may also be affected by the construction of a dam as part of a broader series of process responses
• The water cycle, carbon cycle, climate systems, coastal landscape systems, dryland landscape systems, glacial and periglacial landscape systems, and geological and tectonic systems are examples of systems in physical geography
• Closed system


  No transfer of energy or matter across the external boundaries of the system
• Open system


  Flows of energy and matter across the boundaries of the system
• Closed system


  A system in which there is no transfer of matter or energy across the external borders of the system
• Open system


  A system in which there are flows of energy and matter across the boundaries of the system
• Apart from the Universe, no natural system is truly closed. Only in laboratory conditions (which are not natural) do closed systems exist on Earth
• The planet is an open system with regard to energy. Energy flows from the Sun to Earth, and some is re-radiated back into space
• The Earth can be considered a closed system with regard to matter. Although in the geological past there was some input of water and materials from meteorites, the Earth generally contains all of the matter that it will ever have
• Some matter, such as water, is recycled through the atmosphere and through rocks
• The Earth can be considered a closed system in relation to water and carbon, for example (although both cycles are driven by solar activity, and might still be viewed as open systems with respect to incoming solar radiation)
• A drainage basin or local forest ecosystem receives energy and matter from the Sun, precipitation and higher elevations. These inputs pass through the system, performing functions such as erosion and deposition, to produce outputs of heat, water and sediment
• Carbon sequestration processes taking place in a local ecosystem are balanced by carbon losses from the area (e.g. the removal of timber to other places)
• Equilibrium


  A state of balance between inputs and outputs
• Steady state equilibrium


  A long-term balance is maintained, although there may be short-term changes in the system's state
• Static equilibrium


  A system in which there is no change over time
• Dynamic equilibrium


  A system in which there are short-term fluctuations occurring over a changing long-term mean or baseline
• Over a short-term period, for example weeks or months, no change may be visible, and equilibrium could be said to be static
• A steady state equilibrium is said to exist when there are minor changes to a system, but it always returns to its original form (possible because negative feedback occurs)
• Over a longer term, change may be visible, and dynamic equilibrium is said to occur; i.e. the whole system is very gradually changing due to changes in the wider environment, such as long-term tectonic plate movement affecting a location's altitude and/or climatic characteristics
• UK coastal landscape systems are in a state of dynamic equilibrium when viewed over millennia due to processes like gradual isostatic uplift of Scottish beaches and gradual sinking of the south-east of England following the last major glacial advance
• Mean river flow generally stays the same for a period of days, but following a storm, stream flow (discharge) may increase over the short term. After a few days or longer, stream flow returns to 'normal'
• There may also be seasonal variations in discharge in some climatic zones: the year-on-year pattern generally remains the same, i.e. there is still a steady state equilibrium
• Longer-term cyclical variations lasting for years and decades may occur, associated with events like El Niño or longer-lasting climatic oscillations. But even these changes will usually be reversed, allowing conditions to return to 'normal' after some years
• Over a long-term timescale of millennia, climates can permanently alter, along with stream flows. For example, many streams in southern England had much higher flows during the most recent periglacial climatic phase around 9,000 years ago
• Subsequent changes leading to the climate we experience in the UK today are part of this long-term dynamic trend
• Humans have only been measuring natural phenomena for a relatively short period of the Earth's history and this can make it difficult to identify long-term trends and the equilibria states (or otherwise) of different systems
• Reliable long-term data are required to identify long-term trends and to differentiate them from short-term fluctuations