Surface currents in operational oceanography: Key applications, mechanisms, and methods

Abstract

This paper reviews physical mechanisms, observation techniques and modelling approaches
\ndealing with surface currents on short time scales (hours to days) relevant for operational
\noceanography. Key motivations for this article include fundamental difficulties in reliable
\nmeasurements and the persistent lack of a widely held consensus on the definition of surface
\ncurrents. These problems are augmented by the fact that various methods to observe and
\nmodel ocean currents yield very different representations of a surface current. We distinguish
\nbetween four applicable definitions for surface currents; (i) the interfacial surface current, (ii) the
\ndirect wind-driven surface current, (iii) the surface boundary layer current, and (iv) an effective
\ndrift current. Finally, we discuss challenges in synthesising various data sources of surface
\ncurrents - i.e. observational and modelling – and take a view on the predictability of surface
\ncurrents concluding with arguments that parts of the surface circulation exhibit predictability
\nuseful in an operational context.