Measurements of water characteristics at depths greater than 10 km in the Marianas Trench

doi:10.1016/0146-6291(78)90004-8

Deep Sea Research

Volume 25, Issue 2, February 1978, Pages 169-173

https://doi.org/10.1016/0146-6291(78)90004-8 Get rights and content

Abstract

Measurements of the temperature, salinity, oxygen, and nutrients have been made at depths of 9978 and 10,933 m in the Challenger Deep of the Marianas Trench by means of free-vehicle hydrographic casts. At depths below about 6000 m the deep appears to be filled with a uniform water type characteristic of that at the sill depth. The relations of salinity, oxygen, and silicate to potential temperature in the abyssal waters are not significantly different from those north of the Marshall Islands, about 2000 km to the east, except that the various ridges along the westward path prevent the densest waters from reaching the Marianas Trench.

References (9)

A.F. Amos et al.
Water masses and circulation patterns in the region of the Blake-Bahama Outer Ridge
Deep-Sea Research
(1971)
A. Bradshaw et al.
Direct measurement of thermal expansion of seawater under pressure
Deep-Sea Research
(1970)
H.L. Bryden
New polynomials for thermal expansion, adiabatic temperature gradient and potential temperature of seawater
Deep-Sea Research
(1973)
N.P. Fofonoff
Potential temperature of seawater for an arbitrary reference pressure
Deep-Sea Research
(1977)

There are more references available in the full text version of this article.

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Citation Excerpt :
While it may be true that salinity may compensate temperature to obtain neutral stratification, we do not observe it in our data. In addition Mantyla and Reid (1978) did not observe a change between their 7000 and 11,000 dbar salinity data points. Mantyla and Reid's presentation of a nearly 4000 m large unstable water column is therefore not very likely.
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Free-vehicles operate under the principle that an untethered, negatively buoyant object will descend freely to the sea-bed, and will ascend freely back to the surface if made positively buoyant. Free-vehicle methods have been employed in oceanic exploration for decades (Ewing and Vine, 1938; Hvorslev and Stetson, 1946; Phleger and Soutar, 1971; Mantyla and Reid, 1978 and others). Ewing et al. (1946) noted the following regarding free-vehicles:
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NoteMeasurements of water characteristics at depths greater than 10 km in the Marianas Trench

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Deep-Sea Research

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Measurements of water characteristics at depths greater than 10 km in the Marianas Trench