Spatial variability of turbulent mixing in the abyssal ocean

Science

Volumn 276, Issue 5309, 1997, Pages 93-96

  Polzin, K L ^a   Toole, J M ^a   Ledwell, J R ^a   Schmitt, R W ^a  

^a WOODS HOLE OCEANOGRAPHIC INSTITUTION   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; GEOLOGY; PRIORITY JOURNAL; SEA; TURBULENT FLOW;

ABYSSAL ZONE; SPATIAL VARIABILITY; TURBULENT MIXING;

ATLANTIC, BRAZIL BASIN; ATLANTIC, MID-ATLANTIC RIDGE;

EID: 0030620558     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.276.5309.93     Document Type: Article

References (48)

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37. Our estimate of the turbulent heat flux may be biased low for several reasons. First, more than 45% of the Brazil Basin might be categorized as "rough." The areal fractions assigned in Table 1 are based on our quasi-zonal sections. This breakdown does not, for example, include contributions to the rough-bottom category from the northern and southern boundaries of the Brazil Basin. Second, we most likely under-sampled the mixing on the 0.8°C isotherm where it lies close to the bottom over rough bathymetry. Many of our HRP stations in the eastern Brazil Basin were atop ridge spurs and consequently did not sample temperatures this low. A reanalysis of the heat budget of Hogg et al. at somewhat warmer bounding temperature for which we have more microstructure observations could address this. Third, there may be regional variation in the intensity of the mixing above rough bathymetry due to changes in the small-scale bottom roughness, near-bottom currents, and stratification, all of which affect the generation of internal waves.
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39. 4 is the potential density referenced to 4000 dbar.
40. -1.
41. H. Mercier and K. Speer, in preparation.
42. M. Hall, personal communication.
43. -2 Δε/Δz over a 100-m interval about the 0.8°C potential isotherm. The neglected terms in this equation (set in a coordinate system aligned with the density field) associated with nonlinearities in the seawater equation of state that cause densification of water on mixing [T. McDougall, in Proceedings of Hawaiian Winter Workshop, SOEST Special Publication, 13 to 19 January 1991 (Univ. of Hawaii at Manoa, 1991), pp. 355-386] only exacerbate the problem with the mass budget closure.
44. zρ) peak about the crests of the MAR spurs and decrease with still greater depth within the canyons.
45. With a flat bottom and uniform stratification, the flow would be zonal. However, basin-scale bottom-depth variations [Speer and Zenk (24)] and eddy-driven horizontal recirculations extending from the western boundary [M. A. Spall, J. Mar. Res. 52, 1051 (1994)] may strongly distort this interior circulation from simple zonal flow.
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48. We thank E. Montgomery, D. Wellwood, T. Donoghue, B. Guest, T. Bolmer, S. Sutherland, and L. St. Laurent for support of our field program and data analysis, and the officers and crew of the R/V Seward Johnson. Supported by the NSF Division of Ocean Sciences. The HRP was developed with support from the Department of Defense and the Office of Naval Research. s