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Multiple Abyssal Jets Flowing Into the Vema Deep, Romanche Fracture Zone

Frey, D. I. ; Krechik, V. A. ; Bashirova, L. D. ; Ostroumova, S. A. ; Smirnova, D. A. ; Kuleshova, L. A. ; Ponomarenko, E. P. ; Morozov, E. G. ; Ligi, M. ; Dudkov, I. Yu ; Sivkov, V. V.

Journal of geophysical research. Oceans, 2023-02, Vol.128 (2), p.n/a [Periódico revisado por pares]

Washington: Blackwell Publishing Ltd

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  • Título:
    Multiple Abyssal Jets Flowing Into the Vema Deep, Romanche Fracture Zone
  • Autor: Frey, D. I. ; Krechik, V. A. ; Bashirova, L. D. ; Ostroumova, S. A. ; Smirnova, D. A. ; Kuleshova, L. A. ; Ponomarenko, E. P. ; Morozov, E. G. ; Ligi, M. ; Dudkov, I. Yu ; Sivkov, V. V.
  • Assuntos: Abyssal currents ; abyssal mixing ; Abyssal zone ; Acceleration ; Antarctic Bottom Water ; Aquaporins ; Basins ; Bottom currents ; bottom flows ; Bottom topography ; Bottom water ; Channels ; Connecting ; Expeditions ; Fracture zones ; Geophysics ; Gravity ; Gravity currents ; Heat transport ; Jets ; Kinematics ; Ocean basins ; Ocean currents ; Oceans ; Polar environments ; Polar waters ; Pycnocline ; Pycnoclines ; Romanche Fracture Zone ; Ships ; Vema Deep ; Vertical profiles ; Water circulation ; Water currents ; Water flow
  • É parte de: Journal of geophysical research. Oceans, 2023-02, Vol.128 (2), p.n/a
  • Descrição: Strong acceleration of abyssal flows in narrow deep‐water channels and fracture zones is a key feature of bottom circulation in the Atlantic Ocean. In the Equatorial Atlantic, these bottom currents transport Antarctic Bottom Water (AABW) over the Mid‐Atlantic Ridge from west to east. The main pathway for Antarctic waters in this region is the Romanche Fracture Zone. The deepest point of this fracture zone is the Vema Deep; its maximum depth based on the published data is 7,856 m. This deep basin is filled by waters of Antarctic origin overflowing a sill in a narrow channel. During the expedition on the R/V Akademik Ioffe (August 2022), we revealed a strong flow in the middle part of the Romanche Fracture Zone and collected new data on thermohaline and kinematic structures of this gravity current. Our survey is the first observational evidence of the intense flow into the Vema Deep. At the sill, the flow splits into branches flowing through three distinct channels of intricate configuration located in the southern transform valley of the fracture zone. The northern channel is proved to be the main pathway of the coldest and densest bottom waters to the Vema Deep. We also found that vertical structure of the flow is presented by two individual jets, namely the deep and bottom jets. The total transport of AABW through the Romanche Fracture Zone at this location was estimated at 1.40 Sv; the velocities exceeding 10 cm/s were found at depths greater than 5,000 m. Plain Language Summary Abyssal basins of the Atlantic Ocean are filled with cold and dense Antarctic waters. Propagation of these waters plays an important role in the heat transport of the ocean and influences the Earth's climate. The most intense bottom currents of Antarctic waters are formed in the narrow abyssal channels connecting deep ocean basins. In particular, fracture zones of the Mid‐Atlantic Ridge connect deep basins of the western and eastern Atlantic. The equatorial Romanche Fracture Zone is the deepest fracture zone in the tropical Atlantic and provides transport of the coldest bottom waters from the Brazil to the Guinea and Sierra Leone basins. Direct measurements from ships remain the main source of information about the structure of currents in the abyssal fracture zones. In this work, we present new field observations at the entrance to the Vema Deep, which is the deepest point of the Romanche Fracture Zone. New measurements revealed several jets of the Antarctic Bottom Water flow guided by distinct channels in the bottom topography. It was also shown that the location of the abyssal pycnocline affects the vertical structure of the abyssal currents in this region. Comparison with historical measurements shows an increase in bottom temperatures exceeding 0.06°C. Key Points Flow of the Antarctic Bottom Water (AABW) in the Romanche Fracture Zone intensifies at the entrance to the Vema Deep The flow splits into multiple jets observed in three distinct channels of the fracture zone AABW temperatures in the Vema Deep increased by 0.066°C over the last 30 years
  • Editor: Washington: Blackwell Publishing Ltd
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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