Large internal waves advection in very weakly stratified deep Mediterranean waters

The Eastern Mediterranean Sea contains relatively small trenches O(1-10 km) horizontal width that go deeper than 4000 m. At a first glance, these deep waters are homogeneous, with weak currents <0.1 m s(-1). This viewpoint is modified after evaluation of new detailed yearlong temperature observations using 103 high-precision sensors that reveal intense variability of internal waves. Even though temperature variations are within the range of a few mK only, requiring precise correction for the adiabatic lapse rate during post-processing, the images are permanently dynamic. The weak density stratification of buoyancy close to the inertial frequency supports large turbulent overturns indirectly governed or advected by large internal waves. In strongly stratified (near-surface) waters low-frequency inertial internal motions are horizontal, but here they attain a vertical current amplitude sometimes comparable to horizontal currents. This results in occasionally very large internal wave amplitudes (250 m peak-trough), which are generated via geostrophic adjustment presumably from local collapse of fronts. Citation: van Haren, H., and L. Gostiaux (2011), Large internal waves advection in very weakly stratified deep Mediterranean waters, Geophys. Res. Lett., 38, L22603, doi:10.1029/2011GL049707.