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SUMMARY:Imaging Moving Wet Stuff: An Introduction to Seismic Oceanography 
 - Professor Nicky White (University of Cambridge)
DTSTART:20150313T154500Z
DTEND:20150313T161500Z
UID:TALK58438@talks.cam.ac.uk
CONTACT:Jack Wright
DESCRIPTION:Over the last 50 years\, controlled source seismic reflection 
 imaging of the sub-surface has made spectacular strides. In the 1960s\, yo
 u were doing well if you could make ghostly images of anticlines. Now\, we
  can map buried landscapes in three dimensions and watch injected carbon d
 ioxide flow through saline aquifers. A few years ago\, it was realised tha
 t this technique can also be used to image the detailed structure of therm
 ohaline circulation within the oceanic realm. It turns out that typical se
 ismic reflection experiments are ideally suited to image what physical oce
 anographers confusingly call fine structure (i.e. length scales of 10s to 
 1000s of metres). However\, it is crucial that the seismic records are fir
 st carefully reprocessed since acoustic impedance changes within the water
  column are one or two orders of magnitude smaller that those encountered 
 in the solid Earth. The resulting two-dimensional images are spectacular v
 ertical slices through the water column down to abyssal depths. They have 
 vertical and horizontal resolutions of 5--10 meters and we can image tempe
 rature changes as small as 0.03 degrees Centigrade. Thanks to hydrographic
  calibration\, we are confident that our images are real but we see a vari
 ety of puzzling features which do not have straightforward physical oceano
 graphic explanations. The most significant issue that can be tackled conce
 rns diapycnal (i.e. across density boundaries) mixing. Recent work has sho
 wn that spectral analysis of seismic images reveals important details abou
 t the nature of this mixing process.
LOCATION:Tilley Lecture Theater\, Department of Earth Sciences
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