RAPID: Intercomparison of the Southern Ocean Sea Water pCO2 in IPCC AR5 Coupled Carbon/Climate Models

Earth And Space Research, Seattle WA

Investigators

Abstract

Southern Ocean uptake of anthropogenic CO2 is currently estimated to be responsible for about 40% of the global oceanic CO2 uptake. Fluxes of CO2 into the ocean are driven by the differences in the partial pressure (pCO2) between the atmosphere and the surface ocean layer. As the surface ocean layers increase their pCO2 values, the uptake rate of the Southern Ocean should slow, unless other process (e.g. deep advection, surface cooling?) counteract this. Measurements of Southern Ocean pCO2 values over the past several decades have indicated a warming of the massive Antarctic Circumpolar Current (ACC) system, also leading to increasing surface pCO2. Upwelled water south of the various ACC fronts further brings increased (respired) pCO2 levels to the surface, but may be offset by poleward shifts in the strong westerly wind systems south of the fronts which encircle the Antarctic. Such shifts in the westerlies serve to reduce the area of the ocean over which pCO2 exchange can take place. The interplay of these different yet interacting physical factors is a useful diagnostic for the success of the next generation of climate-earth systems models in predicting future atmospheric CO2 concentrations, and the skill brought to future climate projections. RAPID funding support will allow the examination of the variations, over decadal time sales, of the Southern Ocean pCO2 fields in the next variants of the Intergovernmental Panel on Climate Change (IPCC) coupled carbon/ climate models (earth system models) being produced as part of the next IPCC Assessment Report (IPCC AR5). Intercomparisons of Southern Ocean pCO2 trends over time, as revealed by in IPCC AR5 EaSMs, provides a way of assessing the skill of best available climate model predictions. RAPID support is appropriate due to the short time window between the arrival of the model output in a publicly accessible archive and the deadline for papers analyzing the model output to be accepted for publication. AR5 chapter authors are prohibited from citing research which has not been accepted for publication in a peer-reviewed journal, and papers must be accepted by August 2012 in order to be referenced in the AR5.