After a port call in Port-Mahon, R/V L’Atalante headed North under SWOT swath. With the help of satellite chlorophyll images, we targeted a marked front just North of Menorca island. While crossing the front we observed a distinct current jet by the acoustic Doppler velocimeter. The SeaSoar was also measuring behind the ship, revealing that this front is a clear frontier between two different water masses: east of the front seawater profile is warmer and fresher (blue shape profiles), while being colder and saltier in the west (red shape profiles).
Left: Vessel ADCP overlying a Chlorophyll (Sentinel 3) image; Right: Temperature-salinity diagram from the towed SeaSoar revealing a frontier between distinct water masses.
Several types of buoys were deployed to measure ocean drift. In particular WOCE buoys have a drogue at depth, allowing to measure ocean currents without being perturbed by surface winds. Their successive positions reveal a cyclonic (anti-clockwise) motion west of the front, and anticyclonic (clockwise) eastward. The frontier between these two structures is revealed by chlorophyll images. However they are rather small (about 10km in radius) to be resolved by satellite altimetry today, and are examples of structures we expect to spot using SWOT data. Other smaller buoys were deployed such as the yellow Spotter, coupled with eoDyn devices measuring drift but also waves height and period.
Such marked front in Chlorophyll is very likely to shape barrier between phytoplankton communities. Thanks to the Mediterranean Institute of Oceanography (MIO), the C-SWOT campaign has onboard a cytometer. The cytometer is an automatic instrument using laser beam scattering and fluorescence in different colours, it can investigate differences in phytoplankton morphologies. It will take regular measurement every hour throughout the campaign and will link ocean dynamics to biology.