Annual cycle of poleward heat transport in the ocean: Results from high-resolution modelling of the North and Equatorial Atlantic

Böning, Claus W. and Herrmann, P. (1994) Annual cycle of poleward heat transport in the ocean: Results from high-resolution modelling of the North and Equatorial Atlantic Journal of Physical Oceanography, 24 . pp. 91-107. DOI 10.1175/1520-0485(1994)024<0091:ACOPHT>2.0.CO;2.

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The annual cycle of meridional heat transport in the North and equatorial Atlantic Ocean is studied by means of the high-resolution numerical model that had been developed in recent years as a Community Modeling Effort for the World Ocean Circulation Experiment. Similar to previous model studies, there is a winter maximum in northward heat transport in the equatorial Atlantic and a summer maximum in midlatitudes. The seasonal variation in heat transport in the equatorial Atlantic, with a maximum near 8°N, is associated with the out-of-phase changes in heat content to the north and south of that latitude in connection with the seasonal reversal of the North Equatorial Countercurrent. The amplitude of the heat transport variation at 8°N depends on model resolution: forcing with the monthly mean wind stresses of Hellerman–Rosenstein (HR) gives an annual range of 2.1 PW in the case of a 1/3° meridional grid, and 1.7 PW in the case of a 1° grid, compared to 1.4 PW in a previous 2° model. Forcing with the wind stresses of Isemer–Hasse (IH) gives 2.5 PW in the 1/3° and 2.2 PW in the 1° model case. The annual range of heat transport in the subtropical North Atlantic is much less dependent on resolution but sensitive to the wind stress: it increases from 0.5 PW in the case of HR forcing to almost 0.8 PW with IH forcing.

The annual cycle of heat transport can be understood in terms of wind-driven variations in the meridional overturning; variations in horizontal gyre transport have only little effect both in the equatorial and in the subtropical Atlantic. In all model solutions the seasonal variations in the near-surface meridional Ekman transport are associated with deep seasonal overturning cells. The weak shear of the deep response suggests that the large variations in heat transport on seasonal and shorter time scales should be of little consequence for observational estimates of mean oceanic heat transports relying on one-time hydrographic surveys.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
DOI etc.: 10.1175/1520-0485(1994)024<0091:ACOPHT>2.0.CO;2
ISSN: 0022-3670
Date Deposited: 18 Feb 2008 17:27
Last Modified: 17 Jan 2018 10:45

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