We made four short criss-crossings of the Almeria-Oran front overnight, which is spectacularly sharp in salinity and density, before retrieving and packing up the instrument. The ecoCTD watch noticed a massive aggregation of jelly fish right at the front on every crossing of the front, except the last.
On May 28, we deployed the Lagrangian float from the ship. The float is designed to stay with water of the same density in which it is placed, and since the flow is along constant density surfaces, the float follows the water extremely well. In this study, we are aiming to follow the trajectory of water in three-dimensions, as it gets horizontally advected, but also subducted (vertically) at the front. Later, the float was recovered from a small boat.
On Friday, the winds had died down completely and the sea surface was flat, making it an ideal day for flying from the ship.
This map of sea surface height (from satellite) and the geostrophic currents shows the large-scale pattern of the flow. There is much more variability at smaller scales that does not show up on this image. The yellow pins are waypoints and outline our ship track, which went back and forth across the front (between less and more dense waters) and where there was a strong jet (of almost 80 cm/s). The streaks are the trajectories of the some of the drifters that were deployed in the early stages of the experiment.
At night we deployed a second drifter array in a tight configuration (separated by approximately 1km). At each release location, we deployed 4 drifters — one near surface and the others with drogue depths of 10,30,50m. The separation of these drifters in time, would give an estimate of the vertical shear in the flow. The tight array would help capture the effect of small-scale processes.
For the drifters with a 50 m deep drogue, we used a peg-board to unravel the line between the drogue and the surface buoy.