Australia: The Land Where Time Began

A biography of the Australian continent 

Southern Ocean CO₂ Sink Saturation Due to Recent Climate Change

In this paper Quéré et al. estimate that, based on observations of atmospheric CO₂ and an inverse method, the Southern Ocean CO₂ sink weakened by petagrams of carbon per year per decade relative to be expected to result from the large increase in atmospheric CO₂ between 1981 and 2004. They attributed this weakening to the increased winds that have been observed over the Southern Ocean, as a result of human activities, which has been projected to continue increasing into the future. Consequences of this weakening include an efficiency reduction of the CO₂ sink in the Southern Ocean in the short term, about 25 years, and possibly as well as a higher level of atmospheric CO₂ stabilisation on a multicentury time scale.

It is suggested by observations of the winds of the Southern Ocean that the trend of increasing wind strength may result from atmospheric ozone depletion (Thompson & Solomon, 2002). It is suggested by models that part of the trend may also result from surface temperature gradient changes as a result of global warming (Fyfe, Boer & Flato, 1999; Shindell & Schmidt, 2004). A continued intensification in the Southern Ocean winds throughout the 21^st century is projected by models, assuming the increase in atmospheric CO₂ continues. According to Quéré et al. the oceans will continue to provide a sink for CO₂ as long as the CO₂ concentrations in the atmosphere continue rising, but if:

1)      The fraction of emissions of CO₂ the oceans are able to absorb may decrease if the observed intensification of Southern Ocean winds continues into the future, and

2)      the level at which atmospheric CO₂ will stabilise on a multicentury time scale may be higher if there is an outgassing of natural CO₂ from the Southern Ocean.

Sources & Further reading

1. Quéré, C. L., C. Rödenbeck, E. T. Buitenhuis, T. J. Conway, R. Langenfelds, A. Gomez, C. Labuschagne, M. Ramonet, T. Nakazawa, N. Metzl, N. Gillett and M. Heimann (2007). "Saturation of the Southern Ocean CO₂ Sink Due to Recent Climate Change." Science 316(5832): 1735-1738.