Dr P Brown, Prof N Bates, Prof A Naveira-Garabato
No more applications being accepted
Funded PhD Project (European/UK Students Only)
About the Project
The Southern Ocean (SO) is thought to account for the uptake of ~40% of all global human-derived (anthropogenic) carbon dioxide and >75% of anthropogenic heat, thus being disproportionately influential in the ongoing mitigation of increasing atmospheric CO2 levels and related climate effects. SO CO2 fluxes are a delicate balance of multiple processes; temperature-driven solubility effects, biological carbon drawdown driven by vertical nutrient supply, upwelling-derived outgassing of remineralised carbon, sea-ice formation and melt, and circulation features such as large-scale overturning or mesoscale eddies together combine to make flux estimates difficult and highly uncertain. Our understanding of their present state and future behaviour are limited by both spatial and temporal sparsity of observations, and the inability of models to replicate them, particularly circulation-driven biological effects. Recently, biogeochemical floats (sampling the water column’s top 2000m every 10 days) have massively increased data coverage and led to new flux estimates suggesting a much smaller regional CO2 sink than previously thought. However, float sampling strategies are thought to be insufficient to capture the intensity of short-lived major flux events and features (such as eddies), and the variability of their occurrence, which may compromise their estimates. High frequency glider observations offer the opportunity to fill these gaps, thereby reconciling disparities between integrated observational budget estimates and biogeochemical models, and reducing uncertainties in flux estimates.
The studentship will capitalize on biogeochemical glider deployments within the Atlantic sector of the Southern Ocean planned as part of the NERC ORCHESTRA project. Float-derived parameterizations for pH based on oxygen observations, combined with salinity-based estimates of alkalinity, have previously enabled the full determination of the carbonate system (dissolved inorganic carbon, pCO2). These will be applied for the first time to novel oxygen data from gliders and allow: parameterization testing (and by extension the evaluation of flux estimates derived from floats); interrogation of the carbon system on as yet unobtainable time (<24 hours) and spatial (<10km) scales (particularly within and without the confines of eddies) enabling the constraining and importance of short-lived major flux events; generation of new parameterizations to better capture short-term flux events and variability; application of techniques to historical and future glider missions, improving constraints of regional CO2 fluxes and driving processes. Together, these will greatly expand our understanding of the variability of the carbon system, and provide invaluable information for its autonomous monitoring into the future.
Your major activities within the first year could include:
- Application of pH parameterizations to historical glider data to estimate CO2 fluxes
- Participation in a GO-SHIP cruise in 2018-19 across Drake Passage, analysing for biogeochemical parameters and participation in deployment of gliders.
- Investigation of spatial variability of mixed layer carbon system from novel / historical cruise and satellite data, particularly with relation to eddies.
During the project it may become important to focus more on any one of the processes or to keep a more holistic view. The student will participate and contribute to the full range of activities associated with marine biogeochemical and physical research including work at sea and in the laboratory.
The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for the environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at the University of Southampton, and hosted at the National Oceanography Centre, Southampton. Specific training will include:
1) biogeochemical and physical theory and laboratory and data analysis for the marine carbon system
2) the theory, optimization, maintenance and deployment of novel autonomous ocean gliders equipped with biogeochemical sensors
3) sea-going skills, and training collecting, processing and interpreting measurements and the scientific motivation for taking these data.
Funding Notes
To be eligible for a full NEXUSS award (stipend and fees) a student must have:
No restrictions on how long they can stay in the UK
Been 'ordinarily resident' in the UK for 3 years prior to the start of the grant.
Not been residing in the UK wholly or mainly for the purpose of full-time education. (This does not apply to UK/EU nationals)
Potential PhD students are requested to apply using the University of Southampton postgraduate application form. For information on the application process and documents required please refer to the following webpage: http://noc.ac.uk/education/gsnocs/how-apply
References
de Villiers, S., Siswana, K., and Vena, K., (2014), In situ measurement of the biogeochemical properties of Southern Ocean mesoscale eddies in the Southwest Indian Ocean, Earth Syst. Sci. Data, 7, 415-422, doi:10.5194/essd-7-415-2015, 2015.
Monteiro, P. M. S., L. Gregor, M. Lévy, S. Maenner, C. L. Sabine, and S. Swart (2015), Intraseasonal variability linked to sampling alias in air-sea CO2 fluxes in the Southern Ocean, Geophysical Research Letters, 42(20), 8507-8514, doi: 10.1002/2015GL066009.
Williams, N. L., L. W. Juranek, K. S. Johnson, R. A. Feely, S. C. Riser, L. D. Talley,
J. L. Russell, J. L. Sarmiento, andR. Wanninkhof (2016), Empirical algorithms to estimate water column pH in the Southern Ocean, Geophys. Res. Lett., 43, 3415–3422, doi:10.1002/ 2016GL068539.