A Carbon and transient tracer measurement programme in the Atlantic and Southern Ocean under Oceans 2025

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The oceans act as a heat reservoir, exchanger and transporter, and on time scales longer than a few days it is necessary to include their influence in order to predict weather or climate. Over times of years to centuries, they are also a sink for much of the carbon we are currently releasing into the atmosphere: the heat and carbon budgets are in fact intimately related. The oceans have absorbed almost half the accumulated fossil fuel emissions since the industrial revolution, without which the atmospheric content would be about 60ppm higher than it is today. Ocean uptake of carbon has therefore slowed the pace of human-induced climate change substantially. Theme 1 of the Oceans 2025 proposal includes a programme aimed at studying the role of the large scale ocean circulation in climate, with a focus on the overturning circulation of the Atlantic and the Southern Oceans. A major aim, both in as a scientific product in itself and as a stepping-stone to better understanding of the underlying processes, is to estimate new property budgets and transports of heat, mass, freshwater, and carbon. The new observations which form the basis for this are ocean sections in the Atlantic and Southern Oceans, to be undertaken in the years 2008-2010 by NOC and collaborators. This programme was designed to include carbon and chemical tracer measurements, since these are essential to deliver the carbon inventories. NOC does not have the expertise specialised measurements however, and this proposal is to fund UEA to make them. We already have evidence that the carbon budget of both the Atlantic and Southern Oceans is changing quite rapidly. We do not know to what extent this is a response to human-induced climate change and how much is variation that would occur naturally. The research proposed will enable essential observations to help us document this change, understand its causes, and predict the future of the oceanic sink for the CO2 that we are emitting into the oceans.