SOFAR Float Observations of an Intermediate-Depth Eastern Boundary Current and Mesoscale Variability in the Eastern Tropical Atlantic Ocean

David M. Fratantoni Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

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Philip L. Richardson Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

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Abstract

Two neutrally buoyant SOFAR floats vigorously looped and meandered at depths of 950–1150 m in the eastern tropical Atlantic Ocean. The float trajectories illustrate a poleward flow along the tropical eastern boundary and significant intermediate-depth mesoscale variability in the low-latitude eastern basin. One float, caught within an energetic cyclonic eddy near the eastern boundary, looped cyclonically 14 times while translating 600 km northward parallel to the African coastline. A second float, launched near the Mid-Atlantic Ridge, meandered eastward with a Lagrangian zonal wavelength of 400 km and meridional amplitude exceeding 200 km. Satellite infrared imagery indicates that horizontal shear associated with the system of near-surface zonal equatorial currents may contribute to the observed intermediate-depth variability.

Corresponding author address: Dr. David M. Fratantoni, Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.

Email: dfratantoni@whoi.edu

Abstract

Two neutrally buoyant SOFAR floats vigorously looped and meandered at depths of 950–1150 m in the eastern tropical Atlantic Ocean. The float trajectories illustrate a poleward flow along the tropical eastern boundary and significant intermediate-depth mesoscale variability in the low-latitude eastern basin. One float, caught within an energetic cyclonic eddy near the eastern boundary, looped cyclonically 14 times while translating 600 km northward parallel to the African coastline. A second float, launched near the Mid-Atlantic Ridge, meandered eastward with a Lagrangian zonal wavelength of 400 km and meridional amplitude exceeding 200 km. Satellite infrared imagery indicates that horizontal shear associated with the system of near-surface zonal equatorial currents may contribute to the observed intermediate-depth variability.

Corresponding author address: Dr. David M. Fratantoni, Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543.

Email: dfratantoni@whoi.edu

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