 Figure 6: Carbon cycling in the world’s oceans. The Oceans are absorbing both heat and carbon from the atmosphere,
flow of carbon dioxide across the air-sea interface is therefore alleviating the impacts of global warming in the environ-
a function of CO
2
solubility in sea water (Solubility
ment. Covering more than two-thirds of the earth’s surface, the
Pump). The amount of CO
2
dissolved in sea water
oceans store the sun’s energy that reaches earth’s surface in the
is mainly influenced by physico-chemical conditions
form of heat, redistribute it, from the coast to the mid-ocean, shal-
(sea water temperature, salinity, total alkalinity) and
low to deep waters, polar to tropical, and then slowly release it back
biological processes, e.g. primary production. The
to the atmosphere. These storage and circulation processes prevent
solubility pump and the biological pump enhance the
uptake of CO
abrupt changes in temperature, making coastal weather mild and
2
by the surface ocean influencing its val-
ues for dissolved CO
some high latitude areas of the globe habitable. However this huge
2
and transferring carbon to deep
waters. All these mechanisms are strongly connected,
heat storage capacity can have undesirable consequences with the
subtly balanced and influential to the ocean’s capacity
advent of climate change. With global warming, the ocean is ab-
to sink carbon. The net effect of the biological pump
sorbing a large portion of the excess heat present in the atmosphere
in itself is to keep the atmosphere concentration of
(almost 90%), resulting in a measurable increase of surface water
CO
2
around 30% of what it would be in its absence temperatures (an average of approximately 0.64C over the last 50
(Siegenthaler and Sarmiento, 1993). years) (Levitus et al., 2000; IPCC, 2007b). As water warms, it ex-
Oceans carbon fluxes
Mol of carbon per square metre
Net carbon
release
1
0.5
-0.5
-1
Net carbon
uptake
Source: Marine Institute, Ireland, 2009.
Figure 7: Carbon fluxes in the oceans. (Source: adapted from Takahashi et al., 2009).
23
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