Sverdrups

The Sverdrup, abbreviated Sv, is a unit of measure used in physical oceanography to express large-scale water transport. One Sverdrup equals 1,000,000 cubic metres per second (10^6 m^3 s^-1). It is commonly used to quantify meridional transport in major ocean currents and basin-scale flows.

The unit is named after Harald Ulrik Sverdrup, a Norwegian oceanographer who helped develop the theoretical framework for wind-driven ocean circulation in the mid-20th century. The Sverdrup balance, relating wind stress curl to net meridional transport, provided a foundational concept for understanding large-scale ocean circulation and the use of Sverdrups in reporting transport magnitudes.

In practice, transports of notable ocean systems are expressed in Sverdrups. The Gulf Stream and its North Atlantic extension are typically cited in the range of tens of Sverdrups, commonly around 30–40 Sv. The Antarctic Circumpolar Current is larger, on the order of about 100–150 Sv. These values are approximate and can vary with time, location, and measurement methods.

Sverdrup theory offers a simplified, conceptual framework for wind-driven circulation, linking the curl of wind stress to meridional transport under certain assumptions about steadiness, linearity, and zonal averaging. Real oceans exhibit deviations caused by topography, nonlinear processes, stratification, and mesoscale eddies, so Sv values serve as order-of-magnitude estimates for large-scale flows rather than precise measurements.