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The University of Southampton
NEXUSS - Next Generation Unmanned Systems Science

Tobias Ehmen


Sub-mesoscale variability in the ocean, referring to changes that occur on a space scale of 1-10 km and time scale of days (like eddies or meanders), is poorly understood. The challenge is to observe oceanic thermohaline structures on sufficiently fine space and time scales. One promising approach is seismic oceanography, which applies acoustic reflection techniques, as originally developed by the hydrocarbon industry, to image temperature and salinity gradients within the water column. Along with oceanographic data (temperature, salinity and current speed measurements) a 3D seismic dataset from the narrowest part of Mozambique Channel will be analysed. Through eddy interactions the Mozambique Channel is thought to act as a 'pacemaker' for the Agulhas Current system and plays an important role in global heat transport.

In addition, the implementation of autonomous technology for acoustically mapping oceanic structure will be discussed. Such techniques are key for enabling both the horizontal and vertical structure of the ocean to be mapped at resolutions of 10 m, while avoiding the expensive use of more traditional seismic data acquisition. Furthermore, autonomous instrumentation could overcome the current difficulties of extracting temporal variability and collecting coincident acoustic and oceanographic data. The Mozambique data will be used to forward model potential autonomous seismic sources. Possible autonomous vessels for towing sources include wave gliders, combined with an array of moored or autonomous hydrophones and gliders.


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