marine current mesoscale marine eddy 2010-03-16T12:16:11Z ENVO ENVO:01000069 Mesoscale marine eddies are characterized by currents which flow in a roughly circular motion around the center of the eddy. The sense of rotation of these currents may either be cyclonic or anticyclonic. Ocean eddies are also usually made of water masses that are different to those outside of the eddy. Marine mesoscale eddies are between about 10 and 500 km in diameter, and persist for periods of days to months. They may be formed when an ocean current develops an instability. This instability grows, causing the current to meander, and eventually an eddy is pinched off from the meander. ORCID:0000-0002-4366-3088