Document Type

Article

Publication Date

1-1991

Digital Object Identifier (DOI)

https://doi.org/10.1175/1520-0485(1991)021<0083:ADOTAC>2.0.CO;2

Abstract

Temperature and velocity time series, obtained by surface moorings during the Seasonal Response of the Equatorial Atlantic Experiment, are used to investigate the role of ocean dynamics upon the annual cycle of equatorial sea surface temperature (SST) and upper ocean heat. The annual cycle in SST is explained by different mechanisms, each operant at different phases of the cycle. The boreal springtime decrease in SST results from upwelling in response to the seasonal intensification of easterly wind stress. This upwelling causes the seasonal formation of the cold tongue along the equator in the central and eastern portions of the basin. An early summer increase in SST is attributed to the meridional convergence of Reynolds' heat flux associated with surface current instability-generated waves. After the instability waves abate, SST and mixed layer depth remain relatively steady from late summer through fall when the advective terms are small and cancelling, suggesting that surface heating is then balanced by a diffusive flux at the base of the mixed layer. SST increases in wintertime following the seasonal relaxation in easterly wind stress, thus, completing its annual cycle. This increase is attributed to the concentration of the surface flux over a mixed layer that is shoaling due to both the basin-wide adjustment of the thermocline and the local reduction in turbulent energy production. Thus, SST variations are found to be most closely controlled by ocean dynamics during those times when the thermocline is adjusting basin-wide to the seasonal changes in wind stress; either directly by large advective fluxes (boreal spring-summer) or indirectly by mediating mixed layer depth (boreal winter). Analyses at 75 m depth show zonal and vertical advection to be important, and within a control volume over the upper 150 m all of the advective terms are important.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Journal of Physical Oceanography, v. 21, issue 1, p. 83-96

© Copyright 1991 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to permissions@ametsoc.org. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).

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