Subduction along a Midocean Front and the Generation of Intrathermocline Eddies: A Theoretical Study*

Ou, Hsien-Wang; Gordon, Arnold L.

doi:10.1175/1520-0485(2002)032<1975:saamfa>2.0.co;2

Cited by 24 publications

(22 citation statements)

References 16 publications

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“…Two mechanisms have been proposed for the formation of ITEs by Spall [1995] and Ou and Gordon [2002]. Both are associated with the subduction of mixed layer water across an upper ocean front.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…With the mechanism of Spall [1995] relatively small ITEs (or more precisely SCVs) are formed with the size of the Rossby radius of deformation. The ITEs created by the mechanism of Ou and Gordon [2002] can become larger, because their size depends on the available excess of mixed layer water. Hence we believe that the latter is the most likely formation mechanism, because high‐salinity cores are already visible close to the subduction area near 100°E.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The subduction of STUW at the tropical front may be accompanied by the formation of ITEs of STUW by either the proposed mechanism of Spall [1995] or of Ou and Gordon [2002]. Local instabilities of the SEC, which carries the STUW westward, might also be a cause for the formation of isolated saline ITEs.…”

Section: Hydrographic Observations Of Two Intrathermocline Eddiesmentioning

confidence: 99%

“…A pairing with a cyclonic vortex or the large‐scale flow might be able to transport the SCVs for a long distance from their original location of formation [ Riser et al , 1986]. Ou and Gordon [2002] propose a different scenario for the generation of ITEs in relation to subduction along a mid‐ocean front, which is based on steady state balances. Their mechanism poses a potential vorticity constraint on the mixed layer waters.…”

Section: Introductionmentioning

confidence: 99%

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Intrathermocline eddies in the Southern Indian Ocean

et al. 2006

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[1] In 2001, two relatively saline intrathermocline eddies (ITEs) were observed southeast of Madagascar at 200 m depth. They are characterized by a subsurface salinity maximum of over 35.8 at potential temperatures between 18°and 22°C. The oxygen concentrations within the high salinity cores are slightly elevated compared with those of the surrounding water. Their horizontal extent is about 180 km, several times the Rossby deformation radius, while their thickness is about 150 m. The observed circulation around the ITEs is anticyclonic and maximum velocities of 20 to 30 cm/s are observed at 200 m depth. In these cores the potential density anomaly (25.0 < g < 25.9 kg/m 3 ) has a relatively low vertical gradient and therefore a low planetary potential vorticity. The hydrographic properties of these ITEs are distinctly different from those of the surrounding thermocline water, and especially from the much fresher water mass in the East Madagascar Current. Strong evidence has been found that the distant formation area of the water mass in the ITEs is the subtropical Southern Indian Ocean east of 90°E and south of 25°S, where Subtropical Underwater (STUW) is formed with similar characteristics. Similar high-salinity cores as the ITEs are also found in the thermocline around 200 m depth along an almost zonal section between Madagascar and 100°E. Differences between the hydrographic properties of these cores and the ITEs near Madagascar may partly be explained by interannual variations in the temperature and salinity of the surface mixed layer water in the possible formation area.

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Section: Summary and Discussionmentioning

confidence: 99%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Hydrographic Observations Of Two Intrathermocline Eddiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intrathermocline eddies in the Southern Indian Ocean

et al. 2006

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“…Various formation mechanisms were proposed, including baroclinic instability of undercurrents (Jungclaus, 1999), lateral frictional processes near capes or promontories (D'Asaro, 1988b;Molemaker et al, 2015), diapycnal mixing whether by bottom friction (McWilliams, 1985) or locally intensified internal wave breaking (Lelong & Sundermeyer, 2005;Stuart et al, 2011), winter convection (Testor & Gascard, 2003), or subduction along frontal zones (Ou & Gordon, 2002;Thomas, 2008). They are associated with low values of Ertel potential vorticity (PV) and Brunt-Väisälä frequency, and fairly high Rossby numbers.…”

Section: Introductionmentioning

confidence: 99%

Intrathermocline Eddies Embedded Within an Anticyclonic Vortex Ring

Meunier

Tenreiro

Pallàs‐Sanz

et al. 2018

Geophysical Research Letters

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High‐resolution hydrographic measurements reveal the presence of three intrathermocline eddies (ITEs) embedded within a loop current eddy. ITEs are lenticular bodies of nearly homogeneous water, which contrasts with the well‐stratified surrounding water. Their radii and thickness ranged between 19–32 km and 150–250 m. Negative relative vorticity within their cores (down to −0.85 times the Coriolis frequency), along with a large negative stratification anomaly, results in low Ertel potential vorticity and intense negative Ertel potential vorticity anomalies. Vortex stretching and relative vorticity have comparable contributions to potential vorticity anomaly, resulting in Burger numbers of order unity. The similarity of thermohaline properties within the ITE's cores and the surrounding loop current eddy water suggests that these ITEs likely form by intense mixing events followed by Rossby adjustment.

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Subthermocline eddies observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific Ocean in Spring 2014

Zhang

et al. 2015

Geophysical Research Letters

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In Spring 2014, two subthermocline eddies (STEs) were observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific (STNWP). The first one is a warm, salty, and oxygen‐poor lens, with its temperature/salinity /dissolved oxygen (T/S/DO) anomalies reaching 1.16°C/0.21 practical salinity unit (psu)/−29.9 µmol/kg, respectively, near the 26.62σ0 surface. The other is a cold, fresh, and oxygen‐rich lens, with its T/S/DO anomalies reaching −1.95°C/−0.34 psu/88.0 µmol/kg, respectively, near the 26.54σ0 surface. The vertical extent of the water mass anomalies in the warm (cold) STE is about 190 m (150 m), and its horizontal length scale is 22 ± 7 km (18 ± 10 km). According to their water mass properties, we speculate that the warm and cold STEs are generated in the North Pacific Subtropical and Subarctic Front region, respectively. The observed STEs may play an important role in modifying the intermediate‐layer water properties in the STNWP, and this needs to be confirmed by more focused observations in the future.

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Subduction along a Midocean Front and the Generation of Intrathermocline Eddies: A Theoretical Study*

Cited by 24 publications

References 16 publications

Intrathermocline eddies in the Southern Indian Ocean

Intrathermocline eddies in the Southern Indian Ocean

Intrathermocline Eddies Embedded Within an Anticyclonic Vortex Ring

Subthermocline eddies observed by rapid‐sampling Argo floats in the subtropical northwestern Pacific Ocean in Spring 2014

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