Climatological baroclinic forcing of the barotropic flow in the East Greenland Current in Fram Strait

摘要

Baroclinic forcing of the barotropic flow in the East Greenland Current in Fram Strait (EGCFS) is studied using theoretical analysis and climatological data. First, the validity of the arrested topographic wave (ATW) vorticity balance is reexamined. Then, a distribution of the net (depth-averaged) relative geostrophic flow and the associated along-isobath variations of the bottom density are estimated from the Polar Science Center Hydrographic Climatology (Seattle, Washington, United States). The effect of the along-isobath bottom density variations is referred to as JEBAR b in order to distinguish it from the famous JEBAR (joint effect of baroclinicity and relief), which involves depth-integrated density variations. It is shown that the JEBAR b is able to maintain a significant bottom geostrophic flow in the climatological EGCFS. Estimates of the JEBAR b at 79°N correspond to an increase of the magnitude of the flow by ～3 cm s?1 over a distance of 200 km along the continental slope. An analytical solution for the flow that is driven by a constant JEBAR b term and satisfies the ATW vorticity balance is then obtained in a domain bounded by two parallel isobaths. Finally, the JEBAR b is related to the JEBAR. It is shown that while the JEBAR b maintains the curl of the Coriolis force associated with the bottom geostrophic flow, the JEBAR maintains the curl of the net Coriolis force associated with the absolute geostrophic flow. In the climatological EGCFS over the continental slope, the JEBAR is nearly equal to the JEBAR b .