Abyssal Upwelling in Mid‐Ocean Ridge Fracture Zones. Issue 5 (10th March 2018)

• Record Type: Journal Article
• Authors: Clément, Louis; Thurnherr, Andreas M.
• Is Part Of: Geophysical research letters. Volume 45:Issue 5(2018)
• Page Start: 2424
• Page End: 2432
• Publication Date: 2018-03-10
• Subjects: Mid‐Atlantic Ridge fracture zones -- near‐inertial waves -- turbulent mixing; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL075872
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Turbulence in the abyssal ocean plays a fundamental role in the climate system by sustaining the deepest branch of the overturning circulation. Over the western flank of the Mid‐Atlantic Ridge in the South Atlantic, previously observed bottom‐intensified and tidally modulated mixing of abyssal waters appears to imply a counterintuitive densification of deep and bottom waters. Here we show that inside fracture zones, however, turbulence is elevated away from the seafloor because of intensified downward propagating near‐inertial wave energy, which decays below a subinertial shear maximum. Ray‐tracing simulations predict a decay of wave energy subsequent to wave‐mean flow interactions. The hypothesized wave‐mean flow interactions drive a deep flow toward lighter densities of up to 0.6 Sv over the mid‐ocean ridge flank in the Brazil Basin, and the same process may also cause upwelling of abyssal waters in other ocean basins with mid‐ocean ridges with fracture zones. Key Points: The energy of downward propagating near‐inertial waves in mid‐ocean ridge fracture zones decays toward the seabed Approximately half of the turbulence profiles in fracture zones have local maxima above the seafloor These patterns are consistent with an interaction between the waves and subinertial along‐fracture‐zone flow