Graph of the Day: Iceland Sea pH, 1985-2008

The graphs show Iceland Sea winter surface water changes in pH, and the saturation state of aragonite. The anthropogenic increase of atmospheric carbon dioxide affects the Nordic Seas both at the surface and at depth. In the surface, the pH has decreased from 8.13 to 8.08 between 1985 and 2008, and the aragonite saturation, which is naturally low 10 anyway, decreased from 1.6 to 1.5 between 1985 and 2008. In the deep water, the pressure effect adds to the low temperature, and above the depths of about 1500 m, the aragonite saturation horizon is shoaling at a rate of about 4myr−1. This shoaling results from extensive vertical mixing which transmits atmospheric signatures to waters as deep as 1500m (Messias et al., 2008). Large areas of the benthos are thus 15 undergoing a rapid transition from being exposed to waters that are supersaturated to being exposed to waters that are undersaturated with respect to aragonite. There is an urgent need to clarify the effects of these changes on associated benthic ecosystems, especially at shallower depths, where the population of carbonate forming benthic biota are much greater.

J. Olafsson, S. R. Olafsdottir, A. Benoit-Cattin, M. Danielsen1, T. S. Arnarson, and T. Takahashi, Rate of Iceland Sea acidification from time series measurements [pdf], Biogeosciences Discuss., 6, 5251–5270, 2009 (Updated)