wk 2: cycles and perturbations

biogeochemical cycle

• pathway that describes how a substance moves through the various components (I,e, spheres) of the earth system

• examples

  • elements: carbon, nitrogen, phosphorus

  • molecules: water, silica

  • materials: rock

  • synthetic compounds: long lasting toxins

components of a cycle

• reservoir A (holding tanks for substance)

• flux 1 (transport the substance)

• real cycles have many reservoirs and fluxes

• fluxes need energy

hydrological cycles - the water cycle

• key reservoir: ocean, lake, ice, rivers, clouds

• what are the processes/fluxes that move the water along the reservoirs?

  • evaporation, condensation, precipitation, surface runoff

• energy source that drives the cycle

  • the sun

  • pull of gravity

carbon cycles

• carbon describes organic material

• combination of co2 + water = growth of organic material/vegetation—is where carbon is stored

• creation of fossil fuels from dinosaur carbon + all that lived before in soil

• atmospheric carbon = co2—stored in atmosphere

  • can be dissolved in water—holds carbon

  • stored in lithosphere as sedimentary rocks

earth system—spheres and cycles

• spheres: define main components of earth system

• cycles: describe how substances move among the spheres

  • tgt describe the structure of earth system

    • determines how the earth system will respond to change

• spheres are open bc they exchange ____ and _____

• are cycles open or closed?

equilibrium—steady state/cyclical

• a cycle can be constant or cyclical

• constant: component of cycle stays same

• cyclical: size of the reservoirs + fluxes change, but changes in repeatable patterns at regular intervals

  • time intervals might be different but are predictable

  • e.g. seasons: come every year, predictable (happen quickly compared to ice ages)

perturbations/disturbance

• any sort of external force that changes something in the cycle

• e.g. disturbs flux 1, new reservoirs or fluxes might be added

• perturbations examples

  • landslide into creek

  • changes of earth’s orbit around the sun

  • pollution of a pristine environment

  • changes to the co2 concentration in the atmosphere

  • development of agriculture

  • changes in the economic system

response to disturbances

• cycle will adjust, wants to reach equilibrium

• if there is more energy available, cycle might run faster

  • size of fluxes or reservoirs might need to get bigger or new ones added

types of system response

• linear response (simplest response)

• size of response is proportionate to the perturbation

• e.g. filling of empty kids pool, use small hose pool fills up slowly, big hose pool fills up quickly, when hose is off water level stops changing immediately

  • only very simple systems behave like this

  • earth systems have much more complicated responses

response—feedback loops

• situations where the response of the system affects the magnitude of the disturbance which in turn affects the response of the system

Response: positive feedback loops

• e.g. relationship btw temp in arctic and extent of arctic sea ice

  • sea ice determines how much of incoming solar energy is absorbed at the surface and how much is reflected back to space

Response: negative feedback loop

• respond to a disturbance decreases the initial disturbance itself

• e.g. temperature and clouds: warmer temp = higher humidity, because warmer air can hold more moisture, higher humidity = more clouds, clouds reflect more of the solar radiation back to space, results in air cooling → reduces humidity

• make disturbance disappear through process called self regulation

system responses: spatial scales

• large spatial scales

  • e.g climate change, ice ages—disturbance and response affect entire globe

• small spatial scales

  • e.g. construction of dam—response is limited to local area

• across spatial scales

  • e.g. ENSO—changes in sea surface temperature in Galapagos (southern hemisphere) → regional changes affect weather patterns across the globe, can result in mild weather changes or storms

    • linked to droughts or flooding

    • changes produce secondary effects: influence food production, wildfires → change mortality in plants/animals/humans

system response: temporal scales

• long time scales

  • e.g. ice ages, evolution, ocean circulation

• short time scales

  • e.g. weather changes from volcanic eruptions, seasonal changes in weather

• across time scales

  • e.g. co2 emitted today will stay in atmosphere and affect the climate system for about 100 yrs

    • disturbance now → response later