Bottom water flows in the tropical fractures of the Northern Mid-Atlantic Ridge

Morozov, E. G.; Tarakanov, R. Yu.; Frey, D. I.; Demidova, T. A.; Makarenko, N. I.

doi:10.1007/s10872-017-0445-x

Cited by 46 publications

(27 citation statements)

References 26 publications

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“…Part of AABW from the Brazil Basin penetrates to the Guyana Basin through the Equatorial Channel (Hall et al, ). These waters propagate further to the East Atlantic through numerous fracture zones of the Mid‐Atlantic Ridge north of 3°N latitude (Morozov et al, ). The other part flows to the north up to the deep ocean east of the Newfoundland Bank.…”

Section: The Vema Fracture Zonementioning

confidence: 99%

“…The coldest part of these waters spreads to the east through the Vema Fracture Zone in the Mid‐Atlantic Ridge located approximately at 11°N. In 2014–2016, several CTD/LADCP sections were occupied across the fracture at the main sills (Morozov et al, ). On the basis of these results, it was confirmed (after (Mantyla & Reid, )) that the Vema Fracture Zone plays the most important role in transporting bottom waters to the Northeast Atlantic among all fracture zones of the Mid‐Atlantic Ridge in the Northern Hemisphere.…”

Section: The Vema Fracture Zonementioning

confidence: 99%

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Regional Modeling of Antarctic Bottom Water Flows in the Key Passages of the Atlantic

et al. 2019

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The goal of this research is to modify and apply a version of high-resolution three-dimensional numerical model for simulations of bottom circulation and to study the flows of Antarctic Bottom Water in abyssal channels of the Atlantic Ocean using this model. We adjusted the Institute of Numerical Mathematics Ocean Model σ-level ocean circulation model for several regions with intense bottom currents in abyssal channels. High vertical resolution near the seafloor allowed us to study the abyssal part of the ocean circulation, while high horizontal resolution is necessary for modeling currents in narrow underwater channels and fracture zones. We used our direct velocity measurements carried out at key points of the currents in the channels for verification of the model. This approach was applied in the regions with different seafloor topography: in the long and narrow Vema Channel with a strong bottom current and in several fracture zones of the Mid-Atlantic Ridge with rough bathymetry. On the basis of simulated three-dimensional velocity fields, we analyzed the spatial structure of the bottom currents along the entire length of the channels, determined maximum velocities at different sections, investigated the influence of the Ekman flux on the structure of the flows, and compared our model results with in situ observations. We also calculated the total transports of Antarctic Bottom Water through the fractures in several underwater ridges of the Atlantic Ocean.Plain Language Summary Deep and bottom waters of the ocean are formed in the polar regions and occupy a significant part of the ocean volume. Propagation of these coldest waters plays an important role in the heat transport of the ocean and influences the Earth's climate. At the same time, the lower part of oceanic circulation is less investigated than its upper part. The most intense bottom currents are formed in the narrow abyssal channels connecting ocean basins. Direct deep-water measurements at these points are technically complicated and time consuming; modern computer models are usually focused mostly on the simulations of circulation in the upper layer. The goal of this work is to study intense bottom currents in the key passages of the Atlantic using a numerical model. We adjust our ocean circulation model based on available velocity measurements in the most interesting parts of the currents and compute the spatial structure of the currents in the entire channel. These calculations allow us to get the entire pattern of bottom water motions through underwater ridges and to study some hydrodynamic features of deep-water flows.

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Section: The Vema Fracture Zonementioning

confidence: 99%

Section: The Vema Fracture Zonementioning

confidence: 99%

Regional Modeling of Antarctic Bottom Water Flows in the Key Passages of the Atlantic

et al. 2019

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“…The core of this flow in the Northern Hemisphere deflects to the right in accordance with the geostrophic balance; it is confined to the North Atlantic Ridge. At the same time, a partial outflow of these waters to the East Atlantic occurs through a series of fractures (Strakhov,Bogdanov,7th N Degrees,Vernadsky,Doldrums,Arkhangelsky,10th N Degrees, Vema, Marathon, Cabo Verde, and Kane) (Morozov et al, 2018;Tarakanov et al, 2017). The flow through the Vema fracture at 11°N is the main source of cold bottom waters in the East Atlantic basins north of this fracture up to the West European Basin (Lherminier et al, 2007;Mantyla & Reid, 1983;van Aken, 2007).…”

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confidence: 99%

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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“…Distinctive high silicate values of AABW are noted as far as the subpolar North Atlantic. Efforts to measure this flow have concentrated on constriction points such as the deep current meter measurements in the Vema Channel , close to the Rio Grande Rise in the South Atlantic (Zenk & Morozov, ) or hydrographic estimates of the flow using shipboard hydrography (Morozov et al, ) or dynamic height moorings (Frajka‐Williams et al, ).…”

Section: Introductionmentioning

confidence: 99%