Variability and Mixing of the Surface Layer in the Tyrrhenian Sea. MILEX-80
SACLANT ASW RESEARCH CENTRE LA SPEZIA (ITALY)
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Data from the 1980 Tyrrhenian Sea mixed-layer experiment MILEX-80 are reported. Results from the experiment are presented and discussed. The high south-north gradients in the mixed-layer depth are explained by an Ekman pumping mechanism upwelling and downwelling caused by a maximum in the west wind blowing through the Bonifacio Strait. It is also argued that this band of wind maximum or jet is chiefly responsible for the pair of counter-rotating eddies observed to be quasi-permanent features of this zone. Measured currents in the area were found to be up to twice as great as the currents estimated from the density field. This suggests a strong barotropic component to the currents in the north Tyrrhenian Sea. Some results from mixed-layer models are presented and compared with the data. These illustrate the need to generalize one-dimensional mixed-layer models to 3-dimensions to properly model the mixed layer in areas, such as the MILEX-80 zone, where there is a high spatial variability in the wind field. The wind-stress curl is estimated using two independent methods and compared with historical data for the same area. The first method involves estimating the upwelling and downwelling required to obtain a heat balance in the region. The second method results from a relation between inertial period temperature variance in the thermocline and inertial pulsations in the Ekman mass flux divergence caused by wind stress curl. The two methods show good agreement with each other and with the historical data.
- Physical and Dynamic Oceanography