Detection of oceanic convection utilizing submarine-observed acceleration
Bedell, Kevin F.
Guest, Arlene A.
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The feasibility of using submarine-recorded acceleration and navigational data to detect deep convection in the ocean was explored by comparing actual submarine observations of vertical velocity with vertical velocity of a hypothetical submarine driven through a field of oceanic turbulence predicted by Large-Eddy Simulation (LES). The actual submarine data included time series of three-dimensional acceleration and submarine velocity from the inertial navigation system (INS), gravity and keel depth. Of all these fields, vertical velocity derived from the INS proved most useful for comparison with the simulated vertical velocity fields. The actual observations were analyzed as a function of submarine depth and speed. The spectral energy density was computed for several standard depths, with the largest vertical accelerations found for the times when the submarine was at the shallowest depths. Spectral shape also varied with depth, with the strongest high- frequency/wavenumber intensity for the shoalest cases. The submarine may have experienced a combination of surface gravity wave motion and mixed-layer turbulence in the shallowest case, but there was probably no significant oceanic convection at any of the other depths because of stability of the water column. Spectra of the hypothetical submarine transiting an LES-predicted field of turbulence were contrasted with the spectra of the observed vertical velocity. Although the observed signal's spectral intensity exceeded the spectral intensity for the highest frequency motions of the simulated turbulence, the LES-predicted convection intensity for scales greater than 4OOm was significantly greater than the corresponding signal obtained for the submarine during times when the submarine was not encountering oceanic turbulence.
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