Variations in the Malvinas Current volume transport since October 1992

Abstract

We present a set of new current meter measurements collected to monitor the Malvinas Current (MC) near its merger with the Brazil Current at 40-41°S from December 2001 to February 2003 below a Jason-1 altimeter track. These measurements are compared to former measurements obtained 8 years earlier at the same location; they also provide new information on the core of the MC on the continental slope above the 1000-m isobath where a mooring had been previously lost. There, most of the velocity variation is along-isobath (80% of the variance) and shows a significant annual cycle. The two data sets provide coherent means and statistical parameters on the vertical structure of the flow. A 14-year-long time series of MC volume transport is derived using satellite altimetry. The good correlation between the altimetry-derived transport and the transport estimated from the current meter data persists in time (over 0.7 for each measurement period). A spectacular shift in the spectral composition of transport variations was observed: from 1992 until the end of 1997 transport variations occurred at rather short periods (50-90 days and to some degree around 180 days) whereas, after year 2000, longer periods including a seasonal cycle predominated. Altimetry-derived anomalies of surface geostrophic velocities along the core of the MC show a similar shift in spectral composition suggesting a remote-forcing origin. © 2009 by the American Geophysical Union.