Evidence that Agulhas Current transport is maintained during a meander

Abstract

In April 2010, full-depth hydrographic and direct velocity measurements across a solitary meander in the Agulhas Current were collected at nominally 34°S. During a second cruise in November 2011, a transect across the nonmeandering Agulhas Current was captured. These data provide the first full-depth, in situ picture of the meandering Agulhas Current and allow us to investigate how the velocity structure and transport of the meandering current differs from its nonmeandering state. An analysis of the horizontal momentum equations show that the meander is in geostrophic balance. However, sampling bias causes large differences between geostrophic and direct velocity measurements during meandering, especially near the surface. As the current meanders offshore, its core speed weakens by more than 70 cm s-1 and its width broadens by almost 40 km. These two effects compensate so that the southwestward transport of the Agulhas current is largely unchanged during meandering. At the same time, the meander generates a strong inshore counterflow, which weakens the net Eulerian transport across the 300-km line by almost 20 Sv. © 2014. American Geophysical Union. All Rights Reserved.