EQ1: how does the carbon cycle operate to maintain planetary health? Flashcards
describe the different forms that carbon can exist in, depending on the store
- atmosphere: as carbon dioxide (CO2) and carbon compounds such as methanols (CH2)
- hydrosphere: as dissolved CO2
- lithosphere: as carbonates in limestone, chalk and fossil fuels, as pure carbon in graphite and diamonds
- biosphere: as carbon atoms in living and dead organism
what are carbon fluxes and flows measured in?
pentagrams or gigatoness per year.
what are the two main geological origins of carbon?
- the formation of sedimentary carbonate rocks (limestone) in oceans.
- derived from plants and animals in shale, coal, and other rocks
give an example of carbon resulting from the formation of sedimentary rocks in oceans
the Himalayas form one of the earths largest carbon stores. This is because the mountains started life as ocean sediments, rich in calcium carbonate derived from crustaceans, corals and plankton. Since these sediments have been unfolded, the carbon they contained has been weathered, eroded and transported back to he oceans
describe how carbon is derived form plants and animals, coal and other rocks
these rocks were made up to 300 million years ago from the remains of organisms. these remains sank to the bottom of rivers, lakes and seas and were subsequently covered by silt and mud. as a consequence, the remains continued to decay anaerobically and were compressed by further accumulations of dead organisms and sediment. the subsequent burning of these fossil fuels has, of course, released the large amounts of carbon they contained back in the atmosphere.
define the carbon cycle
the cycle by which carbon moves from one earth sphere (atmosphere, hydrosphere, lithosphere and biosphere) to another. It is a closed system but is made up of interlinked subsystems which are open and have inputs and outputs.
define carbon stores
carbon stores function as sources (adding to carbon in the atmosphere), and sinks (removing carbon from the atmosphere).
define carbon fluxes
(also known as flows or processes) are movements of carbon from one store to another; they provide the motion in the carbon cycle.
what are the two natural geological processes of releasing carbon
- carbon dioxide in the atmosphere reacts with moisture to form sea carbonic acid. when this falls as rain, it reacts with some of the surface minerals and slowly dissolve them i.e there is chemical weathering
- pockets of carbon dioxide exist in the Earth’s crust. Volcanic eruptions and earthquakes can release these gas pockets. This outgassing occurs mainly along mid-ocean ridges, subduction zones at a magma hotspot.
define chemical weathering
the decomposition of rock minerals in their original position by agents such as water, oxygen, carbon dioxide and organic acids.
define outgassing
the release of gas previously dissolved, trapped or frozen or absorbed, in some material (e.g rock)
define carbon sequestration
the process by which carbon dioxide is removed from the atmosphere and held in solid or liquid form. it is the process that facilitates the capture and storage of carbon
what is the largest carbon store?
ocean (the oceanic store of Carbon is 50 times bigger than the atmospheres)
what is most of the oceanic carbon stored in?
-marine algae
-plants
-coral
the rest occurs in dissolved form
what is a carbon pump?
the processes operating in the oceans that circulate and store carbon
what are the three types of oceanic carbon pumps?
- biological pumps
- physical pumps
- carbonate pumps
describe biological pumps in the ocean
Move carbon dioxide from the ocean surface to marine plants (phytoplankton) by processes known as photosynthesis. this effectively converts carbon dioxide into food for zooplankton (microscopic animals) and their predators. most CO2 is taken up by phytoplankton and around 30% sinks into deeper waters before being converted back into carbon dioxide by marine bacteria.
describe physical pumps in the ocean
more carbon compounds to different parts of the ocean in downwelling and upwelling currents. downwelling occurs in those parts of the ocean where cold, denser water sinks. These currents bring dissolved carbon dioxide down to the deep ocean. once there, it moves in slow-moving deep ocean currents, part of the thermohaline circulation, return to the surface upwelling. The cold deep ocean water warms as it rises towards the ocean surface and some dissolved carbon dioxide is rebased back into the atmosphere.
describe carbonate pumps in the ocean
carbonate pumps form sediment from dead organisms that fall to the ocean floor. Particularly significant here are the hard outer shells and skeletons of crustaceans, fish and corals. All are rich in calcium carbonate.
what us phytoplankton
consists of the microscopic plants and plant-like organisms drifting or floating in the sea (of freshwater) along with diatoms, Protozoa and small crustaceans.
define photosynthesis
the process by which green plants and some other organisms use sunlight to synthesise (extract nutrients from carbon dioxide and water).
define the thermohaline circulation
the global system of surface and deep ocean currents driven by temperatures (thermo) and salinity (haline) different parts of the oceans
what is terrestrial sequestration
when plants (primary producers in the ecosystem) sequester carbon out of the atmosphere during photosynthesis. in this way, carbon enters the food chains and nutrient cycle of terrestrial ecosystems. with animals, respiration, waste and death sequesters or releases carbon.
what two time scales do carbon fluxes vary on?
diurnally: during the day, fluxes are positive- that is, from the atmosphere into the ecosystems; at night the reverse situation applies
seasonally: during winter, carbon dioxide concentrations increase because of the low levels of plant growth. However, as soon as spring arrives and all plants grow again, those concentrations begin to decrease until the onset of autumn.
