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An introduction to the physical oceanography of six seamounts in the southwest Indian Ocean

An introduction to the physical oceanography of six seamounts in the southwest Indian Ocean
An introduction to the physical oceanography of six seamounts in the southwest Indian Ocean
Exploratory surveys of six seamounts in the Southwest Indian Ocean provide a description of physical processes induced by seamounts along the Southwest Indian Ridge. Mean currents (15–25 cm s?1) in the vicinity of each seamount were dominated by mesoscale eddies. The dominant seamount-driven process was the generation of internal tides by the barotropic tide interacting with the seamount crests. This led to enhanced shear in the vicinity of the crests resulting in mixing where stratification was weak, for example in the core of an anticyclonic mesoscale eddy or where there had been a winter mixed layer. Tidally driven up- and downwelling was observed at the seabed with associated variability in bottom temperature of up to 3 °C over a tidal cycle. Vertical displacement of isopycnals by internal tidal waves reached 200 m peak to trough. Fluorescence in the surface (eutrophic) layer could thus extend down to the seamount crest on each tidal cycle. Apparently spatial variations in short conductivity/temperature/depth sections across each seamount were probably aliased temporal variations from the strong tidal signal. Evidence for Taylor caps or other potential trapped circulations at the seamount crest was weak, most likely because currents associated with mesoscale eddies were too strong to allow their formation.
Southwest Indian Ridge, Seamounts, Ocean circulation, Internal tides
0967-0645
44-58
Read, Jane
913784a2-30c1-4aa7-aa60-63824998e845
Pollard, Raymond
0c78b909-8a95-4bd2-82fd-9b11022888fd
Read, Jane
913784a2-30c1-4aa7-aa60-63824998e845
Pollard, Raymond
0c78b909-8a95-4bd2-82fd-9b11022888fd

Read, Jane and Pollard, Raymond (2017) An introduction to the physical oceanography of six seamounts in the southwest Indian Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 136, 44-58. (doi:10.1016/j.dsr2.2015.06.022).

Record type: Article

Abstract

Exploratory surveys of six seamounts in the Southwest Indian Ocean provide a description of physical processes induced by seamounts along the Southwest Indian Ridge. Mean currents (15–25 cm s?1) in the vicinity of each seamount were dominated by mesoscale eddies. The dominant seamount-driven process was the generation of internal tides by the barotropic tide interacting with the seamount crests. This led to enhanced shear in the vicinity of the crests resulting in mixing where stratification was weak, for example in the core of an anticyclonic mesoscale eddy or where there had been a winter mixed layer. Tidally driven up- and downwelling was observed at the seabed with associated variability in bottom temperature of up to 3 °C over a tidal cycle. Vertical displacement of isopycnals by internal tidal waves reached 200 m peak to trough. Fluorescence in the surface (eutrophic) layer could thus extend down to the seamount crest on each tidal cycle. Apparently spatial variations in short conductivity/temperature/depth sections across each seamount were probably aliased temporal variations from the strong tidal signal. Evidence for Taylor caps or other potential trapped circulations at the seamount crest was weak, most likely because currents associated with mesoscale eddies were too strong to allow their formation.

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Accepted/In Press date: 2015
Published date: 1 February 2017
Keywords: Southwest Indian Ridge, Seamounts, Ocean circulation, Internal tides
Organisations: Marine Biogeochemistry

Identifiers

Local EPrints ID: 378903
URI: https://eprints.soton.ac.uk/id/eprint/378903
ISSN: 0967-0645
PURE UUID: 957f5535-0f94-484f-84c2-8cfdcbfacf15

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Date deposited: 09 Jul 2015 12:36
Last modified: 10 Dec 2019 06:38

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