Estimating mixing rates from seismic images of oceanic structure

• Published in: Geophysical Research Letters
• Main Authors: Sheen, K L, White, N. J., Hobbs, R. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU 2009
• Subjects: 02 - Geodynamics; Geophysics and Tectonics; Munk; South Atlantic Ocean
• Online Access: http://eprints.esc.cam.ac.uk/1119/; http://eprints.esc.cam.ac.uk/1119/1/Sheen_White_JGR_36_Sep_2009.PDF; https://doi.org/10.1029/2009GL040106

An improved understanding of the spatial distribution of diapycnal mixing in the oceans is the key to elucidating how meridional overturning circulation is closed. The challenge is to develop techniques which can be used to determine the variation of diapycnal mixing as a function of space and time throughout the oceanic volume. One promising approach exploits seismic reflection imaging of thermohaline structure. We have applied spectral analysis techniques to fine-structure undulations observed on a seismic transect close to the Subantarctic Front in the South Atlantic Ocean. 91 horizontal spectra were fitted using a linear combination of a Garrett-Munk tow spectrum for internal waves and a Batchelor model for turbulence. The fit between theory and observation is excellent and enables us to deduce the spatial variability and context of diapycnal mixing rates, which range from 10−5 to 10−3.5m2s−1.