This map shows the pattern of thermohaline circulation also known as "meridional overturning circulation".  This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean.  The entire circulation pattern takes ~2000 years.
BlankMap-World6.svg
Thermohaline_Circulation_2.png (=database)
BlankMap-World6.svg: Canuckguy (talk) and many others
Thermohaline_Circulation_2.png: Robert Simmon, NASA.  Minor modifications by Robert A. Rohde also released to the public domain
derivative work: Miraceti (talk)