An idealized modeling study of the midlatitude variability of the wind-driven meridional overturning circulation
Spall, Michael A.
MetadataShow full item record
KeywordEddies; Large-scale motions; Meridional overturning circulation; Ocean dynamics; Planetary waves
The frequency and latitudinal dependence of the midlatitude wind-driven meridional overturning circulation (MOC) is studied using theory and linear and nonlinear applications of a quasigeostrophic numerical model. Wind forcing is varied either by changing the strength of the wind or by shifting the meridional location of the wind stress curl pattern. At forcing periods of less than the first-mode baroclinic Rossby wave basin crossing time scale, the linear response in the middepth and deep ocean is in phase and opposite to the Ekman transport. For forcing periods that are close to the Rossby wave basin crossing time scale, the upper and deep MOC are enhanced, and the middepth MOC becomes phase shifted, relative to the Ekman transport. At longer forcing periods the deep MOC weakens and the middepth MOC increases, but eventually for long enough forcing periods (decadal) the entire wind-driven MOC spins down. Nonlinearities and mesoscale eddies are found to be important in two ways. First, baroclinic instability causes the middepth MOC to weaken, lose correlation with the Ekman transport, and lose correlation with the MOC in the opposite gyre. Second, eddy thickness fluxes extend the MOC beyond the latitudes of direct wind forcing. These results are consistent with several recent studies describing the four-dimensional structure of the MOC in the North Atlantic Ocean.
Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(8),(2021): 2425–2441, https://doi.org/10.1175/JPO-D-20-0317.1.
Suggested CitationSpall, M. A. (2021). An idealized modeling study of the midlatitude variability of the wind-driven meridional overturning circulation. Journal of Physical Oceanography, 51(8), 2425–2441.
Showing items related by title, author, creator and subject.
Richardson, Philip L. (2007-07-23)Recent global warming caused by humans and the prediction of a reduced Atlantic Ocean meridional overturning circulation in the future has increased interest in the role of the overturning circulation in climate change. ...
Spall, Michael A.; Nieves, David (American Meteorological Society, 2020-02-10)The mechanisms by which time-dependent wind stress anomalies at midlatitudes can force variability in the meridional overturning circulation at low latitudes are explored. It is shown that winds are effective at forcing ...
Mechanisms of multidecadal Atlantic meridional overturning circulation variability diagnosed in depth versus density space Kwon, Young-Oh; Frankignoul, Claude (American Meteorological Society, 2014-12-15)Multidecadal variability of the Atlantic meridional overturning circulation (AMOC) is examined based on a comparison of the AMOC streamfunctions in depth and in density space, in a 700-yr present-day control integration ...