Seasonal and interannual variability in the Mozambique Channel from moored current observations

Ridderinkhof, H., van der Werf, P. M., Ullgren, J. E., van Aken, H. M., Van Leeuwen, P. J. and de Ruijter, W. P. M. (2010) Seasonal and interannual variability in the Mozambique Channel from moored current observations. Journal of Geophysical Research, 115 (C6). C06010. ISSN 0148-0227 doi: 10.1029/2009JC005619

Abstract/Summary

Direct observations from an array of current meter moorings across the Mozambique Channel in the south-west Indian Ocean are presented covering a period of more than 4 years. This allows an analysis of the volume transport through the channel, including the variability on interannual and seasonal time scales. The mean volume transport over the entire observational period is 16.7 Sv poleward. Seasonal variations have a magnitude of 4.1 Sv and can be explained from the variability in the wind field over the western part of the Indian Ocean. Interannual variability has a magnitude of 8.9 Sv and is large compared to the mean. This time scale of variability could be related to variability in the Indian Ocean Dipole (IOD), showing that it forms part of the variability in the ocean-climate system of the entire Indian Ocean. By modulating the strength of the South Equatorial Current, the weakening (strengthening) tropical gyre circulation during a period of positive (negative) IOD index leads to a weakened (strengthened) southward transport through the channel, with a time lag of about a year. The relatively strong interannual variability stresses the importance of long-term direct observations.