How does rising atmospheric CO2 affect marine organisms?

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Rapid Climate Change: Past and Future
Stocker, T.F.  2000.  Past and future reorganizations in the climate system.  Quaternary Science Reviews 19: 301-319.

What was done
The author reviews what is known and/or hypothesized about the role of the deep ocean circulation in causing rapid climate change.

What was learned
The coupled atmosphere-ocean system apparently has thresholds beyond which large-scale reorganizations of the deep ocean circulation can occur.  Historically, such reorganizations have typically occurred during glacial times; and since the demise of the last great continental ice sheets in the Northern Hemisphere, "abrupt climate change of the magnitude typical for the glacial has no longer been observed."  Nevertheless, it has been hypothesized that a future climate warmed by elevated levels of greenhouse gases might result in increased precipitation in the vicinity of North Atlantic Deep Water formation, which could reduce sea surface salinity there and lead to a reduction of the thermohaline circulation in the Atlantic Ocean.  In fact, there are some indications from the Greenland-Norwegian-Iceland Sea that surface-to-deep exchange of water has been interrupted there since about 1980.  However, the Gulf Stream still churns away and Northern Europe does not appear to be headed for cooler times yet.

What it means
Who knows?  In the words of the author, "it must be clearly noted that the present models are useful in furthering our understanding of non-linear processes in the climate system, but they are not predictions."  Much more work will need to be conducted in this field of research before we will be able to determine what the future may hold for us in terms of warming-induced changes in the global ocean's thermohaline circulation and its feedbacks to regional and global climate.

Reviewed 15 May 2000