OXYGEN HOLES

Matthias Hofmann and Hans-Joachim Schellnhuber

Oceanic acidification affects marine carbon pump and triggers extended marine oxygen holes

Abstract

Rising atmospheric CO2 levels will not only drive future global mean temperatures toward values unprecedented during the whole Quaternary but will also lead to massive acidification of sea water. This constitutes by itself an anthropogenic planetary-scale perturbation that could significantly modify oceanic biogeochemical fluxes and severely damage marine biota. As a step toward the quantification of such potential impacts,we present here a simulation-model-based assessment of the respective consequences of a business-as-usual fossil-fuel-burning scenario where a total of 4,075 Petagrams of carbon is released into the atmosphere during current millenium.... Because mineral ballast ,notably CaC03, is found to play a dominant role in carrying organic matter through the water column,a reduction of its export fluxes weakens the setrength of the biological carbon pump. There is ,however,a third effect with severe consequences: Because organic matter is oxidized in shallow waters when mineral-ballast weaken,oxygen holes
(hypoxic zones) start to expand considerably in the oceans in our model world - with potentially harmful impacts on a variety of marine ecosystems.

Proceedings of the National Academy of Sciences of the United States of America,
February 13,2009