A combination of cyclical processes enables the ocean to absorb
more carbon than it emits. Three key functions drive this absorp-
tion. First is the
“
solubility pump,
”
whereby CO
2
dissolves in sea
water in direct proportion to its concentration in the atmosphere.
Second is water temperature: CO
2
dissolves more easily in colder
water, thus greater absorption occurs in polar regions. Third is
mixing of CO
2
to deeper levels by ocean currents. Convergence of
carbon-enriched currents at the poles feed into the so-called ocean
‘
conveyor belt,
’
a global current which cycles carbon into ocean
depths with a very slow (about 1 500 years) turnover back to the
surface. A
‘
biological pump
’
begins with carbon captured through
photosynthesis in surface water micro-organisms, which make up
80
e
90 percent of the biomass in the ocean. These tiny plants and
animals feed carbon into the food chain, where it is passed along to
larger invertebrates,
fi
sh, and mammals. When sea plants and an-
imals die and part of their organic matter sinks to the ocean
fl
oor, it
is transformed into dissolved forms of carbon. The seabed is the
largest reservoir of sequestered carbon on the planet. However, the
ef
fi
ciency of the oceans to capture carbon relies on the structure
and health of the upper layer marine ecosystem (
Williams, 2009).