Animals & nature · 1976
Why do waters just south and north of the equator exchange heat so differently?
The study points to wind-driven upwelling south of the equator and downwelling north of it in the eastern Pacific and Atlantic as a factor maintaining colder waters to the south. Sensible and latent heat fluxes are greatly reduced in these cold-water regions, while net radiation differs only slightly between the southern and northern equatorial zones.
Details
The study examined the oceanic heat budget using ship observations collected during 1911–70 and compiled by one-degree square areas.
In the eastern Pacific and Atlantic, clockwise-turning surface airflow crossing the equator favors upwelling to the south and downwelling to the north, particularly during Northern Hemisphere summer. The wind-induced vertical motion is considered a factor maintaining the tongues of cold water immediately south of the equator and the sharp increase in water temperature northward across it.
Net radiation is only slightly higher in the Southern Hemisphere equatorial zone, but sensible and latent heat fluxes are greatly reduced in the cold-water regions, especially during Northern Hemisphere summer.
As a result, the ocean exports heat at 53 W m−2 south of the Atlantic equator and 62 W m−2 south of the Pacific equator. In the Northern Hemisphere equatorial zone, by comparison, the Atlantic exports only 29 W m−2, while the Pacific imports 3 W m−2.
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