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1.3.5 What are the carbon cycle processes in the ocean? (Shell building…
1.3.5
What are the carbon cycle processes in the ocean?
Ocean floor sediments - largest carbon store
Ocean regulates climate
Control how much carbon in the atmosphere (regulate climate)
Warm water = holds less carbon = more in the atmosphere
Ocean will become less efficient at keeping carbon out of the atmosphere
Ocean absorbs more carbon dioxide
water = more acidic
harms wildlife
1/3 of human generated carbon
Biological pump
Carbon is exchanged between the
oceans
and
atmosphere
through marine organisms.
Globally, nearly
50%
of all carbon fixation by photosynthesis takes place in the ocean. Around
50 Gt
of carbon is drawn from the atmosphere by the pump each year.
Phytoplankton
only food source for some animals
very small
base of marine food web
make CO2
need sunlight, nutrients & water to grow
nutrients fertilise phytoplankton = growth - up-welling bring nutrients up
take in CO2 and release O2
Shell building organisms
Absorb carbonate ions to form shells
Make needles and shields
Silicate and calcium carbonate
Over millions of years, shells fossilise
Found in stones for building
Fossils = geological history
Die but don't decompose
Falls to sea floor = lithicates in rock
Physical pump
Mixing of surface and deep ocean waters by
vertical
currents, allowing carbon to be distributed more evenly. CO2 enters the oceans from the atmosphere by
diffusion
, surface currents transfer the water
towards the poles
where it,
cools, becomes more dense and sinks
. This
downwelling
occurs in only a few places.
Downwelling
carries dissolved carbon to the
ocean depths
where it may remain for
centuries
. Eventually, deep ocean currents transfer the carbon to areas of
upwelling
. There this cold, carbon-rich water rises to the surface and CO2 diffuses back into the atmosphere.