Australia: The Land Where Time Began

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Atlantic Ocean CO2 uptake reduced by weakening of the AMOC

Between 1990 and 2006 there was a rapid decline in the amount of carbon dioxide taken up by the subpolar Atlantic Ocean from the atmosphere, related to warming at the surface of the ocean. The results from model simulations indicated there was a reduced meridional overturning circulation of the Atlantic Ocean (AMOC) at the same time as the reduced CO2 levels. It has been uncertain to what extent the slowing of the circulation system, that is responsible for transporting warm surface waters to the northern high latitudes, and deep waters that are cool to the south, contributed to the uptake of carbon. The authors1 tracked the uptake of CO2 in the subtropical and subpolar regions of the North Atlantic Ocean for the last 2 decades by using data on the oceanic transport of volume, heat and CO2. They assumed that the natural part of the carbon involved related to the atmospheric levels in the preindustrial atmosphere, the remainder being the proportion that is anthropogenic carbon, thereby separating the natural carbon from the anthropogenic carbon. Their results showed that the CO2 released by human activity occurred almost exclusively in the in the subtropical gyre.

They also found that the uptake of natural CO2, that is the result of processes that are part of the Earth system, was the dominant CO2 component in the subpolar gyre. According to the authors1 they attributed the reduced uptake of contemporary CO2 in the subpolar region of the of the North Atlantic to the reduction of the natural component. They suggest their results show that the CO2 uptake reduction was largely the result of the slowing of the meridional overturning circulation, by a reduction of heat loss from the ocean to the atmosphere, and a concomitant decline of the storage in subpolar waters of the anthropogenic CO2,

It has been estimated that the global ocean takes up contemporary CO2 1.6 ± 0.9 PgCyr-1 from observation-based CO2 flux climatology referenced to the year 2000.


Sources & Further reading

  1. Perez, Fiz F., Herle Mercier, Marcos Vazquez-Rodriguez, Pascale Lherminier, Anton Velo, Paula C. Pardo, Gabriel Roson, and Aida F. Rios. "Atlantic Ocean Co2 Uptake Reduced by Weakening of the Meridional Overturning Circulation." Nature Geosci 6, no. 2 (02//print 2013): 146-52.
Author: M. H. Monroe
Last Updated 08/02/2013

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