Geophys. Res. Lett. http://doi.org/2pz (2015)

Increasing anthropogenic emissions are causing a greater amount of CO2 to enter the ocean, resulting in it becoming more acidic. It has been shown that ocean acidification can impact the biological formation of calcium carbonate — which facilitates carbon sequestration through export to the deep ocean. To calculate how calcification rates in the Southern Ocean have changed from 1998 to 2014, Natalie Freeman and Nicole Lovenduski from the University of Colorado, Boulder, USA, used satellite estimates of productivity, calcium carbonate (particulate inorganic carbon) and sea surface temperature.

They find a 4% decrease in calcification across the Southern Ocean for the summer months (December–February) over the 16-year time period. This finding was further investigated in four subregions with significant trends. In the three selected regions in the Indian and Pacific sectors there were reductions of ∼9%. Analysis of the changes in calcification shows that particulate inorganic carbon is the primary driver, with ∼24% decrease in those regions. The Atlantic region, however, showed an increase in calcification (14%) because of a shift in the Polar Front location, which allowed the calcifying species to become more dominant.