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Inertial instability and sea spirals
Author(s) -
Shen Colin Y.,
Evans Thomas E.
Publication year - 2002
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 - 10.1029/2002gl015701
Subject(s) - baroclinity , anticyclone , instability , geology , vortex , geophysics , spiral (railway) , shear (geology) , current (fluid) , mechanics , vorticity , oceanography , physics , petrology , mathematical analysis , mathematics
The ubiquitous occurrence of submesoscale cyclonic spirals in the sea as inferred from space imagery is interpreted in terms of the inertial instability of a horizontally sheared current in the oceanic mixed layer. The instability is shown to weaken anticyclonic current shear while enhancing cyclonic shear, which, in turn, becomes unstable and creates a cyclonic vortex; concurrently, surface tracer particles concentrated along the evolving cyclonic shear are wound up into a spiral, mimicking the spiral slick patterns seen in the imagery. The entire process, investigated with a fully nonlinear nonhydrostatic 3D numerical model, is contrasted with the baroclinic frontal process considered previously. The differences point to a clear need for field observations of this significant phenomenon, which are presently almost totally lacking.