Observations of Internal Gravity Waves by Argo Floats

Tyler D. Hennon School of Oceanography, University of Washington, Seattle, Washington

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Stephen C. Riser School of Oceanography, University of Washington, Seattle, Washington

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Matthew H. Alford School of Oceanography, and Applied Physics Laboratory, University of Washington, Seattle, Washington

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Abstract

This study examines the global variability of the internal wave field near a depth of 1000 m using data from a set of 194 Argo floats equipped with Iridium communications, capable of measuring hourly temperature and pressure during the park phase of their 10-day cycles. These data have been used to estimate vertical isotherm displacements at hourly intervals, yielding a global measure of the heaving due to internal gravity waves. The displacement results have been employed to examine the global variability of these waves and how the displacement power spectrum compares to the canonical Garrett–Munk spectrum. Using the data, the authors find correlations between internal wave intensity and seafloor roughness, proximity to the seafloor, and the magnitude of the local barotropic velocity. The measurements also show large seamount-trapped waves at high latitudes and coastally trapped subinertial waves. These observations provide a rough global census of the nature of these waves that can ultimately be used in studies of ocean mixing.

Corresponding author address: Tyler Hennon, University of Washington, School of Oceanography, P.O. Box 357940, Seattle, WA 98195-7940. E-mail: thennon@uw.edu

Abstract

This study examines the global variability of the internal wave field near a depth of 1000 m using data from a set of 194 Argo floats equipped with Iridium communications, capable of measuring hourly temperature and pressure during the park phase of their 10-day cycles. These data have been used to estimate vertical isotherm displacements at hourly intervals, yielding a global measure of the heaving due to internal gravity waves. The displacement results have been employed to examine the global variability of these waves and how the displacement power spectrum compares to the canonical Garrett–Munk spectrum. Using the data, the authors find correlations between internal wave intensity and seafloor roughness, proximity to the seafloor, and the magnitude of the local barotropic velocity. The measurements also show large seamount-trapped waves at high latitudes and coastally trapped subinertial waves. These observations provide a rough global census of the nature of these waves that can ultimately be used in studies of ocean mixing.

Corresponding author address: Tyler Hennon, University of Washington, School of Oceanography, P.O. Box 357940, Seattle, WA 98195-7940. E-mail: thennon@uw.edu
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