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Low‐frequency interaction between horizontal and overturning gyres in the ocean
Author(s) -
Spall M. A.
Publication year - 2008
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 - 10.1029/2008gl035206
Subject(s) - baroclinity , geology , advection , wind stress , zonal and meridional , ocean gyre , downwelling , boundary layer , climatology , atmospheric sciences , boundary current , buoyancy , mechanics , ocean current , oceanography , physics , subtropics , fishery , biology , upwelling , thermodynamics
Low‐frequency variability of the horizontal circulation in an idealized, eddy‐permitting, numerical model drives the dominant mode of low‐frequency variability in the meridional overturning circulation. This coupling takes place through the influence of lateral advection in the cyclonic high‐latitude boundary current on the mixed layer depth along the boundary. The mean and low‐frequency variability of the meridional overturning circulation are well predicted by a diagnostic estimate that assumes the downwelling is controlled by the thermal wind shear within the mixed layer along the boundary, which is in turn determined by a simple balance between lateral advection and surface cooling. The more general result is the demonstration that the mean and low frequency variability of the meridional overturning streamfunction are controlled by the baroclinic pressure gradient within the mixed layer along the boundary, which may be influenced by numerous factors such as low‐frequency variability in lateral advection, wind stress, surface buoyancy fluxes, or ice melt and freshwater runoff.