To date ca. 400 billion tons of fossil fuel-derived carbon have entered the ocean as carbon dioxide diffusing in from the atmosphere, and this has resulted in a decrease in ocean pH of 0.1 units, compared with pre-industrial times. Caldeira and Wickett (2003) have calculated that a decrease in surface pH of 0.7 units will result by ca. year 2300, if fossil fuel emissions continue unabated (see Figure 1)

Long time-series data sets at marine monitoring stations such as ESTOC have already measured a decline in ocean pH (see Figure 2).

Many (although not all) experimental studies have found detrimental impacts of acidification on marine organisms (see Figure 3), in particular on calcifying organisms (i.e. those which synthesise mineral calcium carbonate to form shells or skeletons).

NOCS carries out a variety of research on the biology, chemistry, modelling and palaeoceanographic record of ocean acidification.

We are testing the responses of a variety of organisms to higher CO2 (lower pH) levels. Shelled organisms including both small (e.g. unicellular coccolithophores) and large (e.g. oysters) are being tested for susceptibility. The responses of individual taxa are tested in laboratory tanks and we also test the natural planktonic community response during on-deck incubations. We are comparing the distributions of chemical parameters and biological organisms (biogeography) to investigate the ranges of pH values and saturation states that different organisms can tolerate.

We are deploying established measurement systems (DIC, Alk, pH, pCO₂) to determine how ocean carbon chemistry is being affected by enhanced CO2 uptake by the ocean. A novel sensor is being developed for the measurement of the effect pH. We are investigating the influence of changes in pH on metal speciation and bioavailability.

We use simple box models, Earth system models of intermediate complexity (GENIE) and ocean GCMs (e.g. OCCAM) to predict future impacts of ocean acidification on ocean chemistry and atmospheric CO2, and to model the carbon biogeochemistry changes through past (de-)acidification events in Earth System history.

NOCS is currently investigating the consequences of ocean acidification for climate relevant processes such as carbon export fluxes and dimethyl sulphide (DMS) production

We are examining the fossil sedimentary record of past (de-)acidification events (millions of years ago in Earth history) to see how different organisms survived (or not) these past times of acidification. In addition to evaluating the ability of different taxa to survive past periods of acidification, we are also investigating the overall Earth System response to these events.

For more information see the work being carried out by each researcher.