Publication Date:
2022-05-25
Description:
Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 53 (2006): 207-225, doi:10.1016/j.dsr2.2005.08.021.
Description:
Four drifting floats were used to measure the magnitude of the vertical derivative
of horizontal velocity in waters above the rough bathymetry of the Mid Atlantic
Ridge. This derivative is typically the dominant component of the velocity gradient
(the shear). Two floats were at the site of the Brazil Basin Tracer Release Experiment
(BBTRE) in the South Atlantic, and two were near the site of the Guiana Abyssal
Gyre Experiment (GAGE) in the North Atlantic. Floats operated for one year except
for one BBTRE float which operated for 100 days. Shear was measured over a vertical
span of 9.5 m using drag elements that caused the floats to rotate slowly in response
to shear. For each float, the first, second and fourth moments of shear were elevated
above levels associated with the Garrett-Munk model internal-wave spectrum. Three
of the four floats were tracked as they moved over mountainous terrain, allowing
shear intensity to be measured as a function of height above the bottom. A deep
BBTRE float showed enhancement of rms shear near the bottom. Floats at both
areas provided measurements at 2000 m above the bottom, with differing results: The
GAGE site had a lower fourth moment of shear (diapycnal diffusivity proxy) than the
BBTRE site. However, application of normalization factors accounting for differences between the sites in bottom roughness, latitude-dependent internal-wave dynamics, and tidal current speeds brings the results into agreement.
Description:
This work was funded
by the National Science Foundation under grants OCE9416014 and OCE9906685.
Keywords:
Internal waves
;
Internal wave shear
;
Diapycnal mixing
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
451951 bytes
Format:
application/pdf
