Instabilities in ocean currents can be identified through synergistic use of data from the Copernicus Sentinel-3 satellites.
10 November 2020
03 November 2019
By Aida Alvera Azcarate (University of Liege) and Hayley Evers-King (EUMETSAT)
In the southern part of the Mediterranean Sea, the Algerian current runs along the coast of Northern Africa. The current is part of the general circulation pattern in the western Mediterranean, which can be complex, including features such as the highly variable Alboran Gyres.
Figure 1 shows the current along the Algerian coast and a clear connection through both temperature and the overlaid currents, to the waters in the west of the image.
The Algerian current frequently becomes unstable, forming meanders and eddies. The animation in Figure 2 shows a series of images, as in Figure 1, of sea surface temperature from the Sentinel-3 SLSTR instruments.
As the meanders travel off-shore they generate a current that results in upwelling of colder waters. These physical dynamics create a biological response in the phytoplankton (microscopic, plant-like organisms), that can be seen through ocean colour imagery.
In Figure 3, an image from the Sentinel-3 OLCI sensor, shows increased chlorophyll-a concentrations, associated with colder, more nutrient rich waters of the meander. The meanders can eventually break off entirely to form large eddies, which can be more than 100 km in diameter, and may persist at time frames between several months and years. Comparison with the SST images in Figure 2 shows how cold waters, induced by the circulation, are likely a source of nutrients for the increased phytoplankton growth evidenced by the distribution of chlorophyll-a concentration. Estimates of high chlorophyll-a concentration, very near the coast, may also be affected by the presence of re-suspended sediments.
Anticyclonic eddy in the Mediterranean Sea
In May 2019, an anticyclonic eddy formed between the islands of Mallorca and Sardinia.
Major eruption of La Soufrière volcano
Major eruption of the Caribbean volcano La Soufrière in early April 2021.
Major dust outbreaks - Africa, Middle East & China
Meteosat-8 spots series of dust outbreaks in March 2021.
Spotting Etesian winds in solar imagery using moonglint
Etesian winds spotted in the solar spectrum in Feb 2021.
Arctic blast turned US white
Band of ice from freezing rain over Texas clearly seen in RGB imagery on 19 Feb 2021.