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Cambridge NERC Doctoral Landscape Awards (Training Partnerships)

Graduate Research Opportunities

Lead supervisor: Nicky White, Earth Sciences

Co-supervisor: Andy Woods, Earth Sciences

Brief summary: 
Rather amazingly, seismic reflection (i.e. acoustic) profiling can be used to image circulation of the oceans: a whole new subject has opened up with fabulous implications for how oceans evolve and affect climate!
Importance of the area of research concerned: 
Recently, it has been shown that seismic reflection profiling yields spectacular and well-resolved acoustic images of different water masses in the oceans. These images have already provided new and exciting insights into important oceanographic phenomena (e.g. structure and evolution of thermohaline fronts, internal eddy formation, diapycnal mixing). Just as satellite imagery revolutionized our understanding of the physical, chemical and biological evolution of the sea surface, the nascent discipline of `seismic oceanography' is likely to have an equally profound impact upon our quantitative understanding of four-dimensional (4D) oceanic circulation.
Project summary : 
This project will address the general problem of 3D acoustic imaging of the water column and its implications for time-lapse imaging by analyzing a 3D seismic dataset located offshore South America. It is divided into three stages. First, detailed acoustic images will be generated by developing and applying a novel processing strategy to this 3D dataset which is located within an oceanographically significant deep-water location. Secondly, these images will be interpreted and calibrated with the aid of extensive legacy hydrographic measurements, notably temperature and salinity. Thirdly, these models will form the basis of a fluid dynamical understanding of important phenomena such as diapycnal mixing.
What will the student do?: 
We will exploit a range of methodologies which come from disciplines as diverse as signal processing to fluid dynamics. These methodologies can be divided into four groups. First, we will use seismic processing packages to carry out basic and specialized processing of field tapes. Secondly, we will use in-house algorithms to determine seismic response from hydrographic observations, enabling calibration of seismic reflection imagery. Thirdly, we will adapt in-house algorithms to auto-track reflectivity and to calculate internal wave and turbulent vertical displacement spectra. Finally, we will use analytical and numerical fluid dynamical modeling to develop a quantitative understanding of water mass interactions.
References - references should provide further reading about the project: 
Sheen, K., White, N., Caulfield, C., & Hobbs, R.W., 2012. Seismic imaging of a large horizontal vortex at abyssal depths beneath the Sub-Antarctic Front. Nature Geosciences, vol. 5, 542-546, doi:10.1038/NGEO1502.
Sheen, K., White, N., Caulfield, C. & Hobbs, R.W., 2011. Estimating Geostrophic Velocity Fields from Seismic Images of Oceanic Structure. J. Atmos. Ocean. Tech., doi: 10.1175/JTECH-D-10-05012.1.
Sheen, K.L., White, N., & Hobbs, R., 2009. Estimating mixing rates from seismic images of oceanic structure. Geophys. Res. Letts., vol. 36, L00D04.
You can find out about applying for this project on the Department of Earth Sciences page.