Finestructure contamination by internal waves in the Canary Basin
Gostiaux, L.; van Haren, H. (2012). Finestructure contamination by internal waves in the Canary Basin. J. Geophys. Res. 117. dx.doi.org/10.1029/2012JC008064
In: Journal of Geophysical Research. American Geophysical Union: Richmond. ISSN 01480227; eISSN 21562202, meer
 
Auteurs   Top 
 Gostiaux, L.
 van Haren, H., meer



Abstract 
Over a range of 132.5 m, 54 temperature sensors (1 mK relative accuracy) were moored yearlong while sampling at 1 Hz around 1455 m in the open Canary Basin. Coherence between individual records shows a weak but significant peak above the local buoyancy frequency N for all vertical separations Delta z < 100 m, including at sensor interval Delta z = 2.5 m. Instead of a dominant zerophase difference over the range of sensors, as observed for internal waves at frequencies f < sigma < N, with f denoting the inertial frequency, this superbuoyant coherence shows piphase difference. The transition from zerophase difference, for internal waves, to piphase difference is abrupt and increases in frequency for decreasing Delta z < 10 m. For Delta z > 10 m, the transition is fixed at Nt similar or equal to 1.6N, which is also the maximum value of the smallscale buoyancy frequency, and limits the internal wave band on its highfrequency side. In the time domain it is observed that this highfrequency coherence mainly occurs when nonlinearities in the temperature gradient, such as steps in the temperature profile, are advected past the sensors. A simple kinematic model of finestructure contamination is proposed to reproduce this observation. The canonical 2 slope of the temperature spectrum above N is not observed in the in situ data, which rather slope as 8/3. The 8/3 slope can, however, be reproduced in our model, provided the jumps in the temperature profile are not infinitely thin. 
