The Southern Ocean (SO) is the most exciting and extreme region of the world ocean, with the strongest winds, coldest temperatures, and most intense storms. It is believed also to be among the largest 'sink' for atmospheric CO2, accounting for about one third of the uptake of CO2 by the global ocean and nearly one tenth of the global emissions of CO2 on average each year. Thus the evolution of the SO carbon sink has the potential to alter the rate and extent of climate change. In spite of its importance, we don't know the state, variability, or climatic drivers of the contemporary SO carbon sink and there is much controversy over its recent evolution. The climate of the SO has been changing over recent decades: in particular, winds have intensified, (attributed in part to the depletion of stratospheric ozone and in part to increasing temperature gradients arising from climate change), ocean acidification is occurring, and there is a long term decline in krill stocks. These effects take place on top of large natural variability and poorly quantified climatic trends. SONATA will achieve a step change in our understanding of the contemporary SO carbon sink by delivering new data and new insights, integrating observations from the ocean, from the atmosphere, and model results. We will develop three complementary streams of research, an 'Oceanic', an 'Atmospheric', and a 'Processes and drivers' view, and will bring them together using advanced mathematical frameworks to provide a single assessment with multiple constraints and reduction of uncertainties. The Oceanic view will use existing and new observations of ocean carbon. We will undertake a new calibration experiment to better assess the large number of pH measurements now being made by about 200 sophisticated profiling floats introduced by the US SOCCOM programme. These have the potential to greatly increase the number of observations that can be used to calculate air-sea CO2 fluxes, but only if adequately calibrated. In addition we will develop and use a new technique to construct estimates of the seasonal and temporal evolution of the air-sea flux, using a model of the upper water column constrained with available hydrographic and carbon-system observations. The Atmospheric view will collect new atmospheric CO2 data in remote SO locations comprising Halley Station (75S), the Falkland Islands (51S), and aboard the BAS research ship James Clark Ross; new atmospheric O2 data will come from a ship track that repeats a SO transect every 8 weeks, as well as from Halley Station in coastal Antarctica. Using these data and an inverse framework approach, SONATA will provide an independent assessment of the SO carbon sink, which will deliver particularly on the geographic distribution of the changes, with O2 data helping to inform the drivers. The Processes and drivers view will use two climate-scale carbon models and a series of hindcast simulations to identify the relative contributions of (a) atmospheric CO2 concentration, (b) natural climate variability, (c) climate change, and (d) stratospheric ozone depletion to recent SO carbon trends and variability. Ocean and atmosphere observations, including new data from SONATA and SOCCOM, will be used to optimise the model and validate the results. Idealised forcing with climate models will provide the 'fingerprints' of climatic drivers that are needed to understand the observed patterns of change. Finally the three streams of research will be integrated using a Bayesian fusion mathematical approach that considers the strengths and weaknesses of each stream of information and minimises the joint uncertainty. The SO ocean carbon sink will be assessed annually in this way. We will then test the added value of including new streams of observations in the future, including from floats, gliders, drifters, Autonomous Surface Vehicles, additional ground-based observations and satellite CO2 data.

Warming of the climate system is unequivocal, and very likely due to the increase of carbon dioxide (CO2) and other greenhouse gases in the atmosphere. CO2 is the most important and fastest-growing greenhouse gas. It is released to the atmosphere mainly by the burning of fossil fuel from human activities and by deforestation. Governments around the world have pledged to limit global warming to 2 degree Celsius above pre-industrial levels. According to current knowledge, such a commitment requires that the global emissions of CO2 peak at the latest between 2015 and 2020, and decrease sharply afterwards. The political discussions to develop an international agreement that would limit global warming are based on scientific knowledge provided by the international community. Key to those discussions is the provision of the latest up to date information, and the transparency of the scientific debate and information. The Global Carbon Project (GCP), established in 2001, coordinates international research on the carbon cycle. Since 2004, the GCP with the support of the community has compiled, analysed and published information on the "global CO2 budget", including the CO2 emissions and their partitioning among the atmosphere, ocean and land reservoirs. This effort has provided tremendous information to help the policy process and the public understand the human and natural factors that control the concentration of CO2 in the atmosphere. The annual CO2 budget has growth beyond the capacity of the GCP. At the same time, the demand is growing for more and better information, more background supporting material, more transparency in the methods and process, and traceability of the information. The community is trying to organise itself further to support this important effort. This proposal aims to establish an office of the GCP in at the Tyndall Centre for Climate Change Research of the University of East Anglia. This location would be ideal to support the publication of the annual CO2 budget because of its already well-established research on the carbon cycle, the strength and complementary work done in its existing programmes, and its unparallelled record of providing high quality policy-relevant science to UK and international policymakers. The UK GCP office would provide key support, and further credibility and visibility to the annual CO2 budget. Scientists have begun to think about how to produce carbon information services to assist in the necessary transition towards a low-carbon economy. One way proposed by the GCP is to institutionalise the more operational aspects of the GCP activities, such as the publication of CO2 budgets, through the establishment of an International Carbon Office. The development of such an ambitious project needs careful thinking and strong commitment from stakeholders. The UK GCP office would work with existing organisations to establish the structural basis of an ICO and determine its potential and viability in the long term.