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Title: The East Madagascar Current: Volume transport and variability based on long-term observations
Authors: Ponsoni, Leandro
Aguiar González, Miguel Borja 
Ridderinkhof, Herman
Maas, Leo R.M.
UNESCO Clasification: 251007 Oceanografía física
Keywords: Boundary currents
Circulation/ Dynamics
Geographic location/entity
Indian Ocean
Mesoscale processes
Issue Date: 2016
Journal: Journal of Physical Oceanography 
Abstract: This study provides a long-term description of the poleward East Madagascar Current (EMC) in terms of its observed velocities, estimated volume transport, and variability based on both ~2.5 yr of continuous in situ measurements and ~21 yr of satellite altimeter data. An array of five moorings was deployed at 23°S off eastern Madagascar as part of the Indian-Atlantic Exchange in present and past climate (INATEX) observational program. On average, the EMC has a horizontal scale of about 60-100 km and is found from the surface to about 1000-m depth. Its time-averaged core is positioned at the surface, at approximately 20 km from the coast, with velocity of 79 (±21) cm s-1. The EMC mean volume transport is estimated to be 18.3 (±8.4) Sverdrups (Sv; 1 Sv ≡ 106 m3 s-1). During the strongest events, maximum velocities and transport reach up to 170 cm s-1 and 50 Sv, respectively. A good agreement is found between the in situ transport estimated over the first 8 m of water column [0.32 (±0.13) Sv] with the altimetry-derived volume transport [0.28 (±0.09) Sv]. Results from wavelet analysis display a dominant nearly bimonthly (45-85 days) frequency band of transport variability, which explains about 41% of the transport variance. Altimeter data suggest that this band of variability is induced by the arrival of westward-propagating sea level anomalies, which in turn are likely represented by mesoscale cyclonic and anticyclonic eddies. Annual averages of the altimeter-derived surface transport suggest that interannual variabilities also play a role in the EMC system.
ISSN: 0022-3670
DOI: 10.1175/JPO-D-15-0154.1
Source: Journal of Physical Oceanography [ISSN 0022-3670], v. 46 (4), p 1045-1065
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