Probably two currents meeting and created a Mesoscale Eddy:
"Mesoscale ocean 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. Oceanic eddies are also usually made of water masses that are different to those outside of the eddy. That is, the water within an eddy usually has different temperature and salinity characteristics to the water outside of the eddy. There is a direct link between the water mass properties of an eddy and its rotation. Warm eddies rotate anti-cyclonically, while cold eddies rotate cyclonically.
Because eddies may have a vigorous circulation associated with them, they are of concern to naval and commercial operations at sea. Further, because eddies transport anomalously warm or cold water as they move, they have an important influence on heat transport in certain parts of the ocean."
