Premium
Direct Observations of Near‐Inertial Wave ζ ‐Refraction in a Dipole Vortex
Author(s) -
Thomas Leif N.,
Rainville Luc,
Asselin Olivier,
Young William R.,
Girton James,
Whalen Caitlin B.,
Centurioni Luca,
Hormann Verena
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl090375
Subject(s) - refraction , wavelength , dipole , geology , inertial wave , anticyclone , physics , geophysics , optics , atmospheric sciences , wave propagation , longitudinal wave , mechanical wave , quantum mechanics
Generated at large horizontal scales by winds, near‐inertial waves (NIWs) are inefficient at radiating energy without a shift to smaller wavelengths. The lateral scales of NIWs can be reduced by gradients in the Coriolis parameter ( β ‐refraction) or in the vertical vorticity ( ζ ‐refraction) or by strain. Here we present ship‐based surveys of NIWs in a dipole vortex in the Iceland Basin that show, for the first time, direct evidence of ζ ‐refraction. Differences in NIW phase across the dipole were observed to grow in time, generating a lateral wavelength that shrank at a rate consistent with ζ ‐refraction, reaching ∼ 40 km in 1.5 days. Two days later, a NIW beam with an ∼ 13 km horizontal and ∼ 200 m vertical wavelength was detected at depth radiating energy downward and toward the dipole's anticyclone. Strain, while significant in strength in the dipole, had little direct effect on the NIWs.