6.2 Biological processes sequestering carbon

Question 1

6.2a Ocean sequestering

carbon stores

Answer 1

the oceans store 93% of carbon dioxide in undersea algae, plants and coral, with the remainder in dissolved form

Question 2

6.2a Ocean sequestering

carbon cycle pumps

what are carbon cycle pumps?
what are the different types?

Answer 2

carbon cycle pumps are the processes operating in oceans to circulate and store carbon

the three types are biological, carbonate and physical

Question 3

6.2a Ocean sequestering

carbon cycle pumps: biological pump

Answer 3

sequestration of carbon dioxide to oceans by the photosynthesis of phytoplankton

phytoplankton are the base of the marine food web (their huge numbers make up half the planet’s biomass)

the Arctic and Southern Oceans are very productive areas because of continental shelves and nutrient upwellings increasing they have even faster growth rates, called net primary productivity (NPP)

carbon is then passed up the good chain by consumer fish and zooplankton, which in turn release carbon dioxide back into the water and atmosphere via respiration

most is recycled in surface water

dead organic matter and faecal pellets sink to the ocean floor forming calcareous ooze, and either decompose or are turned into sediment

phytoplankton sequester over 2 billion metric tonnes of carbon dioxide annually to the deep ocean

Question 4

6.2a Ocean sequestering

carbon cycle pumps: carbonate pump

Answer 4

the carbonate pump relies on inorganic carbon sedimentation

marine organisms use carbonate compounds (such as calcium carbonate) to form outer shells and inner skeletons

when organisms die and sink, man shells dissolve before reaching the sea floor sediments

this carbon becomes part of deep ocean currents

shells that do not dissolve build up slowly on the sea floor, forming limestone sediments

Question 5

6.2a Ocean sequestering

carbon cycle pumps: physical pump

Answer 5

thermohaline circulation drives physical carbon pump

carbon dioxide in the oceans is mixed up much more slowly than in the atmosphere, so there are large spatial differences in carbon dioxide concentrations

the colder the water, the more potential for carbon dioxide to be absorbed (polar oceans store more water than tropical oceans and deep ocean store more water than surface)

as major ocean currents such as the North Atlantic Drift (Gulf Stream) move waters from the tropics to the poles, the water cools and can absorb more atmospheric carbon dioxide

high latitude and arctic zones with deep oceans have cool water, which sinks because of its higher density, taking carbon dioxide accumulated at the surface downwards

Question 6

6.2a Ocean sequestering

thermohaline circulation in physical pump

Answer 6

a