Capturing the Transport Variability of a Western Boundary Jet: Results from the Agulhas Current Time-Series Experiment (ACT)
Open Access
- 1 May 2015
- journal article
- research article
- Published by American Meteorological Society in Journal of Physical Oceanography
- Vol. 45 (5), 1302-1324
- https://doi.org/10.1175/jpo-d-14-0119.1
Abstract
The volume transport of the Agulhas Current was measured over a 3-yr period by an array of seven current meter moorings and four current- and pressure-recording inverted echo sounders (CPIES) deployed at 34°S. CPIES extended the array farther offshore in order to capture, for the first time, the full Agulhas Current during meander events. Transports derived from CPIES are well correlated with overlapping current meter transports (0.89). The Eulerian mean current is 219 km wide and 3000 m deep, with peak surface speeds of 1.8 m s−1 and a weak northward undercurrent on the continental slope below 1200 m. A new algorithm to capture the western boundary jet transport at each time step T is defined as the poleward transport out to the first maximum of the vertically integrated velocity beyond the half-width of the mean jet. The mean transport of the Agulhas Current jet, so defined, is −84 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) with a standard error of 2 Sv. Sampling and instrumental errors are explicitly estimated and amount to an additional 9 Sv. A more traditional estimate, based on net transport integrated to a fixed distance offshore Tbox, gives a mean transport of −77 ± 5 Sv. This transport is 10 Sv greater than an equivalent transport at 32°S, corresponding to a latitudinal increase equal to that predicted by Sverdrup dynamics. The time series of T and Tbox show important differences during solitary meander events and at longer time scales. In terms of an annual cycle, the Agulhas Current appears strongest during austral summer, a similar phase to the Gulf Stream and Kuroshio.Keywords
This publication has 48 references indexed in Scilit:
- Impact of the Indonesian Throughflow on Agulhas leakageOcean Science, 2013
- Satellite observations of an annual cycle in the Agulhas CurrentGeophysical Research Letters, 2012
- Seasonal Variability of the Atlantic Meridional Overturning Circulation at 26.5°NJournal of Climate, 2010
- A Time Series of Agulhas Undercurrent TransportJournal of Physical Oceanography, 2009
- Upstream control of Agulhas Ring sheddingJournal of Geophysical Research: Oceans, 2002
- Vertical structure and transport on a transect across the North Atlantic Current near 42°N: Time series and meanPublished by American Geophysical Union (AGU) ,2000
- The importance of flow in the Mozambique Channel to seasonality in the Greater Agulhas Current SystemGeophysical Research Letters, 1999
- Western boundary currentsReviews of Geophysics, 1995
- Seasonal and low frequency variations in dynamic height anomaly and transport of the Gulf StreamDeep Sea Research Part I: Oceanographic Research Papers, 1995
- A technique for objective analysis and design of oceanographic experiments applied to MODE-73Deep Sea Research and Oceanographic Abstracts, 1976