Blue Carbon
WATER-COLUMN STRATIFICATION AND LOSS OF COASTAL PUMPS Warming and melting is enhancing seasonal water-column strati- fication in the ocean on a global scale, mainly in temperate seas. Some coastal ”flushing” mechanisms – so-called dense-shelf water cascading – may also be weakened with climate change, resulting in slower “cleaning” of polluted coastal waters, more algae blooms and dead zones, and lack of transport of food particles to organisms living in the deep sea and on the sea floor. The resulting reduction in nutrient flux will cause a decline in primary production and pos- sibly in ocean productivity. 4 SHIFTS IN DISTRIBUTION OF SPECIES AND MIGRATORY ROUTES The distribution of plankton, fish and other marine fauna has shift- ed hundreds of kilometers toward higher latitudes, especially in the North Atlantic, the Arctic Ocean, and the Southwest Pacific Ocean. Additionally ocean warming has noticeable effects on the migratory routes of many species. 5 1958 - 1981 1982 - 1999 1982 - 1999 1982 - 1999 000 - 2002
OCEAN ACIDIFICATION The ocean is absorbing excess CO 2 from the atmo- sphere which is causing changes in the biogeochemi- cal carbonate balance of the ocean, and thus signifi- cant acidification of ocean waters. The ocean is thus somehow alleviating the impacts of global warming in the biosphere. With climate change and ocean acid- ification a large reduction in the ability of the ocean to take up atmospheric CO 2 is expected. The reduc- tion of pH and calcium carbonate saturation levels in the oceans will affect thousands of species from the wide range of marine organisms which need carbon- ate in their development and for forming shells and skeletons. The structure of marine ecosystems are ex- pected to be severely impacted by acidification with potential extinctions and large-scale reduction in bio- diversity and ecosystem services, primarily because of the speed at which these water chemistry changes are occuring. 6 2000 - 2002
1
2000 - 2002
1958 - 1981
1982 - 1999
2000 - 2002
Global ocean acidification
Oceanic CO 2 concentration
Ocean water acidity
atm 380
pH
8.14
360
8.12
1958–1981
1982–1999
2000–2002
340
8.10
Mean number of species per CPR sample
Mean number of species per CPR sample Mean number of speci s per CPR sam le
Mean number of species per CPR sample
0.0
0.1
320
8.08
0.0
0.0
0.1
0.0
0.1
0.1
Figure 13. Plankton migration shift. Figure 14. As carbon concentrations in the atmosphere increase, so do concentrations in the ocean, with resultant acidification as a natural chemical process. Source: based on Ahlenius, H., 2008; Personal communication with Chris Reid, SAHFOS, Novem- ber 2007.
300
8.06
1985 1990 1995 2000 20051985 1990 1995 2000 2005
Source: IPCC, 2007.
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