A sverdrup (abbreviated as sv; not to be confused with the sievert) is a unit used to express volume transport in ocean currents. It is named for Harald Sverdrup, a pioneering oceanographer of the 20th century. A sverdrup equals 1 million cubic meters per second, or roughly half the volume of the Louisiana Superdome per second. The Gulf Stream flow, for example, is at least 55 sv, about 300 times the usual flow of the Amazon River.
Source: Garrison, Tom. Essentials of Oceanography, Second Edition.