Diffusion Coupling of Bottom to Deep Water in the Atlantic

Dr. Anders Levermann
Potsdam Institute for Climate Impact Research


Date: Tuesday, May 10, 2005
Time: 3:00 p.m.
Location: Clark 507, Quissett Campus


We give a theoretical discussion of the coupling between Atlantic Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW). We propose that AABW is driven mainly by NADW through diffusive exchange of buoyancy forcing. Based on minimal assumptions on the geometry of the circulation we derive robust expressions for the overturning strength and the vertical extension of the AABW cell as a function of the strength of NADW in equilibrium. The result is a characteristic curve, which shows an increase of AABW strength with NADW and saturation for strong NADW volume fluxes. In contrast, the vertical extension of the AABW cell decreases and then saturates with increasing NADW strength. The theoretical results are supported by comparison with simulations using the coupled climate model CLIMBER-3alpha.

*Co-sponsored by PO and OCCI