Question

Explain why the Atlantic exhibits the anomalous northward heat transport in the southern hemisphere

Answer 1

We first show that the ocean is warmer than the land in general which, acting alone, would make
the Southern Hemisphere warmer because of its greater fraction of ocean.
it was caused by greater humidity and greenhouse trapping over the ocean
than over the land. However, for any given temperature, greenhouse trapping is actually
greater over the land than the ocean. Instead, oceans are warmer than land because of
smaller surface albedo. However, inter-hemispheric differences in total albedo are negligible
because the impact of differences in land-sea fraction are offset by Southern Hemisphere
ocean and land reflecting more than their Northern Hemisphere counterparts.
it is shown that northward cross-equatorial ocean heat transport is critical for
the Northern Hemisphere to be warmer. This is examined in a simple box model based on
the energy budget of each hemisphere. This inter-hemispheric difference forced by ocean
heat transport is enhanced by the positive water vapor-greenhouse feedback, and is partly
compensated by the southward atmospheric energy transport, which is accomplished by
locating the Intertropical Convergence Zone in the Northern Hemisphere. However, to fully
explain the temperature difference in this way requires a northward ocean heat transport
at the extreme of observational estimates. A better fit to data is found when a larger
basic state greenhouse trapping in the NH, conceived as imposed by continental geometry,
is also imposed.