Southern Ocean Seasonal Cycle Experiment 2012 : seasonal scale climate and carbon cycle links

In early May 2012, South Africa will take delivery of a new polar research ship, the SA Agulhas II, representing a significant investment of R1.6 billion in polar infrastructure to further strengthen South Africa’s presence in the polar region, particularly in support of its stewardship of the Southern Ocean and Antarctic Treaty obligations. This investment follows closely on recent DST–CSIR infrastructure investments in the Centre for High Performance Computing, used to run global ocean–climate models, an ocean robotics observational capability and five other new research facilities. Together, these investments offer opportunities to enhance South Africa’s advanced numerical and technological capacity as well as its impact on Southern Hemisphere polar climate and ecosystem science by using its geographical advantage. We are planning the first scientific programme that will capitalise on these major infrastructure investments: the Southern Ocean Seasonal Cycle Experiment (SOSCEx). The Southern Ocean is arguably the main source of medium-term uncertainty in terms of the effectiveness of global CO 2 mitigation plans. The reason for this is that the Southern Ocean plays both an important role in the uptake of anthropogenic CO 2 (50% of all ocean uptake) as well as in the very large (90 Gt/Cy) natural CO 2 exchange between the oceans and the atmosphere. The Southern Ocean is the only region where deep-ocean CO 2 reservoirs (38 000 Gt C) exchange directly with the smaller atmospheric reservoir (700 Gt C). Moreover, although 85% of all ocean productivity is supported by nutrients derived from the Southern Ocean, little is known about the sensitivity of these carbon and nutrient fluxes to climate change driven adjustments or – most importantly – at what scales these links couple. One of the important gaps in the reliable prediction of the response of the Southern Ocean carbon cycle to climate change is its sensitivity to seasonal, subseasonal forcings (in time) and mesoscales (in space). The Southern Ocean Carbon and Climate Observatory (SOCCO), a CSIR-led consortium, is planning SOSCEx, which will be a new type of large-scale experiment. SOSCEx reflects a shift from the historical focus on shipbased descriptive Southern Ocean oceanography and living resource conservation, to systemscale dynamics studies spanning much greater time and space scales. Our limited grasp on these climate and climate-feedback sensitivities are linked to key knowledge gaps on the scales that link climate to carbon. Moreover, existing global models show only weak agreement in terms of the seasonal cycle of the upper-ocean in both physical and biogeochemical indicators such as primary productivity (Lenton A, Tilbrook B 2011, personal communication, Aug 01). The seasonal cycle is one of the strongest modes of variability in the primary productivity and the carbon cycle of the Southern Ocean. Additionally it reflects the coupling between climate forcing and important ecosystem responses, such as productivity. 1