Investigating the role of the Southern Ocean in uptake and storage of anthropogenic carbon and heat using transient tracers

University of Exeter - College of Life and Environmental Science

This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP).  The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus six Research Organisation partners:  British Antarctic Survey, British Geological Survey, Centre for Ecology and Hydrology, the Met Office, the Natural History Museum and Plymouth Marine Laboratory. The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme please see

Of all the CO2 released into the atmosphere by humans since pre-industrial times, the oceans have taken up about 30%, lessening the effects of this greenhouse gas. Among them, although occupying only a quarter of the global ocean area, the seas surrounding Antarctica, so called the Southern Ocean, accounts for half the global ocean’s uptake of anthropogenic carbon (Cant) and about three-quarters of the excess heat that has accumulated in the Earth system as a result of these emissions (Fralicher et al., 2014).

This primary role of the Southern Ocean in controlling the rate at which ocean reservoirs of heat and carbon communicate with the surface is due to its unique circulation pattern (Morrison et al., 2015). It is the only place where there is direct upwelling from old deep waters to the sea surface over a very large region, providing the window for exchange between the global deep ocean and the atmosphere, as well as ventilating much of the global ocean by forming subtropical mode, intermediate and bottom waters.

In this context, information provided by passive anthropogenic transient tracers such as chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF6) is a powerful tool (Jenkins and Smethie, 1996). Those compounds, also released into the atmosphere by human activity, are a good proxy for Cant. They enter the ocean surface through air-sea exchange, marking the water with specific properties and then, as they are transported into the interior, trace the pathways of the oceanic circulation. Their known time-varying (transient) sources allow for estimate interior ventilation time scales (ages) and Cant uptake by the ocean (and analogically for passive heat).

The University of Exeter and the British Antarctic Survey are looking for a student to join two expeditions under the ORCHESTRA/NERC program ( to make CFCs/SF6 measurements, across the Antarctic Circumpolar Current and the Weddell Sea, substantially increasing the number of observations in the Southern Ocean and contributing to model developments.

We will use the newly collected, and existing observational data, to provide insight into both the time scales and the dynamics of the ventilation. We will then quantify the associated uptake and storage of heat and Cant and assess for change. The various sources of uncertainty will be tackled by developing the transient tracer based methods in comparison with other methods and outputs from the CMIP5&6 (Coupled Model Inter-comparison Project) and GFDL (Geophysical Fluid Dynamics Laboratory) models.

This is an exciting multidisciplinary opportunity to contribute to leading-edge research in a rarely visited part of the world. The student will get a solid knowledge of the Southern Ocean circulation and biogeochemistry in connection with our changing planet.

Please see for more information regarding applications.

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South West England