Environmental Engineering Reference
In-Depth Information
Ocean Acidity
Little attention has been paid to the fact that increasing the amount of
carbon dioxide in the atmosphere causes water to become more acid.
The percentage increase in acidity of the oceans so far has not been
determined, and the increased temperature of ocean water counteracts
the effect of increased carbon dioxide because heat drives off gas dis-
solved in water. The ocean currently absorbs at least half of the carbon
dioxide humans produce, but a ten-year study by scientists published in
2007 concluded that the amount of carbon dioxide absorbed by the
ocean is decreasing.
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Researchers have been concerned that increased ocean acidity will
be harmful to most shelled creatures because increased acidity makes
it harder for these creatures to grow their shells. However, recent
research has revealed a previously unknown complexity in this equa-
tion.
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It seems that some shell-building creatures, including crabs,
shrimp, lobsters, urchins, limpets, and those red and green algae
that have calcium carbonate skeletons, build more shell when there
is a slight acidifi cation of the water in which they live. Apparently
the organisms are able to manipulate their organic biochemistry to
counteract small changes in ocean acidity. How they do this is not
known.
Ocean Currents
Global warming may have a signifi cant effect on the behavior of the
major currents in the world ocean. These currents are driven by three
things: the earth's rotation, which cannot change; the temperature dif-
ference between the poles and the equator, which is changing as the earth
warms; and salinity differences between one part of the ocean and
another, which is changing as melted ice pours into the ocean. The effect
these changes will have on oceanic circulation is uncertain, but climate
scientists believe there is reason for concern.
Tipping Points
Tipping points are instances of very rapid change preceded by long
periods of slow change. The rapid change occurs in the same way as the
slowly increasing pressure of a fi nger eventually fl ips a switch and turns
on a light. Once the switch has occurred, the new and hostile climatic
event lasts for perhaps centuries or even millennia. Earth's climate system
can jump within a few years from one stable operating mode to a com-
pletely different one.
