Antarctic bottom water flow in the western part of the Romanche Fracture Zone based on the measurements in October of 2011

Tarakanov, R. Yu.; Makarenko, N. I.; Morozov, E. G.

doi:10.1134/s0001437013050147

Cited by 11 publications

(29 citation statements)

References 10 publications

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“…We used the bottom topography from the 1‐min digital array (Smith & Sandwell, ) V.18.1. However, our measurements in 2011 in the region showed that the difference between the digital bottom array and the actual depths can be as high as 700 m (Tarakanov et al, ). Therefore, we carried out a detailed survey of the region with parallel tracks separated by 1–2 miles using the ELAC LAZ 4700 echo sounder.…”

Section: Data and Data Processingmentioning

confidence: 94%

“…The width of the valley at a level of the 4,150‐m isobath is 5–10 km (Figure b); the choice of this particular isobath for characterizing the width is related to the dynamic structure of the spillway in the western part of the Romanche fracture. This isobath approximately corresponds to an isotherm of θ = 1.2 °C, which is approximately the upper boundary of the spillway layer (Tarakanov et al, ). It is likely that the sill depth of the Northern Valley in this segment does not exceed 4,300 m. In the eastern direction the valley depth becomes deeper than 5,200 m already at 22°10′W.…”

Section: Bottom Topography In the Deep Spillway Regionmentioning

confidence: 99%

“…From 2011, the Shirshov Institute of Oceanology of the Russian Academy of Sciences has been conducting field research in the western part of the Romanche FZ. In 2011, a hydrographical survey consisting of a section of five stations with CTD and LADCP casts across the fracture channel at 22°10′W, one station in the fracture channel 18 km west, and one station in the gap in the Southern Wall of the fracture at 22°27′W was made (Figure b; Tarakanov et al, ). In addition, echo sounding of the bottom topography has been performed along the vessel's route.…”

Section: Introductionmentioning

confidence: 99%

“…However, the existence of a deep spillway in this area was established from indirect indications: by the erosion of the lower part of the deep thermocline with θ < 1.2 °C as the current overflows the sill in this gap, and by a sharp temperature increase (from 0.51 to 0.65 °C) over a distance of only 15 miles to the east along the pathway in the fracture channel. The latter observations made it possible to estimate the coefficient of vertical turbulent exchange k z in the area of the spillway as O(10 −2 ) m 2 /s (Tarakanov et al, ). This value is 2 orders of magnitude greater than the canonical value (Munk & Wunsch, ), which is necessary to maintain the existing density stratification in the deep layer of the World Ocean, and 3 orders of magnitude greater than the values observed in the open ocean (Gregg, ; Polzin et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

et al. 2018

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Structure of the deep spillway was studied on the basis of conductivity‐temperature‐depth, lowered acoustic Doppler current profiler, and mooring measurements in 2011–2014 in the Romanche fracture zone (22°27′–22°32′W). The spillway exists quasi‐permanently in the regime of hydraulic control overflow and consists of two flows in the layer θ < 1.20 °C (deeper than 4,150 m). The first flow enters the fracture from the south through a gap in the Southern Wall. The second flow is directed to the east along the narrow valley of the fracture. The sill depths of these passages are 4,570 and 4,430 m, respectively. The depths over the surrounding ridges are shallower than 4,100 m. Both flows descend to the local depression of the fracture with 5,000‐m depth. Bottom potential temperatures over both sills were 0.51 °C, and the measured velocities were 20–40 cm/s. When the flows descend down the slope, they accelerate in supercritical regime. Maximal measured velocities were up to 65 cm/s. Analysis of the 189‐day time series of velocities on the mooring deployed in the flow descending from the gap showed a very high level of fluctuation energy: 10 times greater than the energy of the barotropic tide at this point. The only energy source of these fluctuations is the available potential energy of the deep thermocline in the West Atlantic transforming to the kinetic energy of the deep spillway. The total transport of the bottom water below θ = 1.2 °C based on the lowered acoustic Doppler current profiler measurements is estimated at 0.29–0.35 Sv, which agrees with the predicted values.

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Section: Data and Data Processingmentioning

confidence: 94%

Section: Bottom Topography In the Deep Spillway Regionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

et al. 2018

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“…Before the bottom water enters the Romanche Fracture Zone its temperature is 0.674 • C; the coldest temperature at the entrance to the Chain Fracture Zone is 0.682 • C (Mercier and Morin, 1997). The recent measurements in 2011 recorded a temperature of 0.508 • C before the Romanche Fracture Zone and 0.648 • C in the fracture at 22 • 20 W (Morozov et al, 2012;Tarakanov et al, 2013). The potential temperature at the entrance to the Vema Fracture Zone is = 1.33 • C (Mantyla and Reid, 1983).…”

Section: Introductionmentioning

confidence: 99%

Transport of Antarctic bottom water through the Kane Gap, tropical NE Atlantic Ocean

2013

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Abstract. We study low-frequency properties of the Antarctic Bottom Water (AABW) flow through the Kane Gap (9 • N) in the Atlantic Ocean. The measurements in the Kane Gap include five visits with CTD (Conductivity-TemperatureDepth) sections in 2009-2012 and a year-long record of currents on a mooring using three AquaDopp current meters. We found an alternating regime of flow, which changes direction several times during a year. The seasonal signal seems to dominate. The maximum daily average values of southerly velocities reach 0.20 m s −1 , while the greatest north-northwesterly velocity is as high as 0.15 m s −1 . The velocity and transport at the bottom are aligned along the slope of a local hill near the southwestern side of the gap. The distribution of velocity directions at the upper boundary of AABW is wider. The transport of AABW ( < 1.9 • C) based on the mooring and LADCP (Lowered Acoustic Doppler Current Profiler) data varies approximately within ±0.35 Sv in the northern and southern directions. The annual mean AABW transport through the Kane Gap is almost zero.

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Extremely long Kelvin‐Helmholtz billow trains in the Romanche Fracture Zone

Haren

Gostiaux

Morozov

et al. 2014

Geophysical Research Letters

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In the Atlantic Ocean, the densest water mass Antarctic Bottom Water "AABW" can only cross the Mid-Atlantic Ridge from its southwestern to northeastern basins in limited, because deep, conduits. At the southwestern entrance of one of these, the equatorial Romanche Fracture Zone, AABW crosses a sill at 4550 m depth in a 7 km narrow channel before plunging into the deep. At the sill-slope, the rapidly flowing AABW causes shear-induced turbulent mixing with the overlying water masses. We present an excerpt of 1 Hz sampled, half-yearlong moored observations from 99 high-resolution temperature sensors that demonstrate and quantify the turbulence details. On top of quasi-steady shear flow, an internal tide modulates the mixing. Together, they constitute a means for an extremely long train of >250 consecutive Kelvin-Helmholtz billows in a day that vary between 5 and 100 m in vertical scale.

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Antarctic bottom water flow in the western part of the Romanche Fracture Zone based on the measurements in October of 2011

Cited by 11 publications

References 10 publications

Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

Structure of the Deep Spillway in the Western Part of the Romanche Fracture Zone

Transport of Antarctic bottom water through the Kane Gap, tropical NE Atlantic Ocean

Extremely long Kelvin‐Helmholtz billow trains in the Romanche Fracture Zone

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