Tidal motions in the deep Mediterranean

TL;DR

This study investigates the subtle tidal motions in the deep Mediterranean Sea, revealing their influence on temperature records and internal wave dynamics despite their small surface amplitudes.

Contribution

It provides new insights into the presence and effects of internal tides and inertio-gravity waves in a region known for minimal tidal activity.

Findings

Surface tides have an amplitude of 0.1 m in the Northwestern Mediterranean.

Internal wave temperature signals can be corrected for semidiurnal barotropic tides.

Baroclinic tides are present within the inertio-gravity wave band, with energy enhancements near boundaries.

Abstract

The Mediterranean Sea is known for its limited tidal motions. For example, surface barotropic tidal elevations have an amplitude of 0.1 m in the Northwestern Mediterranean. Nevertheless, these small tides are noticeable in temperature records at the 2500-m deep seafloor, but only under near-homogeneous conditions when buoyancy frequency N < f, the inertial frequency. After transfer of pressure to temperature units via the local adiabatic lapse rate, the observed internal-wave temperature signals may thus be corrected for 1.5x10-5-degrC amplitude semidiurnal barotropic tides. The remaining baroclinic tides are embedded in the broad and featureless inertio-gravity wave band, with some energy enhancement near its boundaries, also under tenfold-larger energetic stratified water conditions.