Bottom topography and oceanic variability

Abstract:

Many fundamental theories of ocean circulation

neglect bottom topography. Indeed, ocean models with a flat bottom are still often used to study different phenomena. Here we examine evidence that the bottom affects eddies throughout the water column. Current meter data point to the existence of a mode of variability which is largest at the surface and decreases to near zero at the bottom. We show that the gravest baroclinic mode over a sloping bottom has the same shape, even with very weak slopes. Then we examine how topography affects ocean jets, like the Antarctic Circumpolar Current. Having relatively modest bottom bumps can suppress baroclinic instability, favoring lateral (barotropic) instability instead. Taken together, the results suggest topography exerts an important influence on variability, and thus that flat bottom models may be misleading.

Joe LaCasce did his PhD in the MIT/WHOI Joint program in physical oceanography. He was a post-doc at IFREMER in Brest, France before returning to Woods Hole as an assistant scientist. He moved to Norway in 2002 and has been a professor at the University of Oslo since 2007.