WHOI PO

Mooring data from the Celtic Sea are used to describe baroclinic energy flux at the continental shelf break. Most of the baroclinic energy flux is associated with the M2 internal tide and has a mode-2 structure. Using harmonic analysis, currents and density anomalies are decomposed into coherent (constant phase relative to the barotropic tide) and incoherent (varying phase relative to the barotropic tide) components. Coherent and incoherent components are presumed to indicate local or remote-generation, respectively, of the baroclinic tide. The energy-flux divergence between the moorings and the dominance of the coherent signal suggest a local generation site for the baroclinic tide. However, the directions of energy propagation indicate that two onshelf moorings, separated by 30 km in the along-shelf direction, receive baroclinic energy from two distinct generation sites. We hypothesize that strong wind events at the shelf break alter tidal energy propagation via two processes: firstly, lowered stratification may alter the criticality of the shelf-break topography and hence internal wave reflection at the slope; secondly, 2-3 day period variability may result from interference between inertial and M2 frequency waves.