Publication Date:
2014-07-15
Description:
Recently it has been shown that anti-cyclonic eddies are generated in the Comoros Basin contesting the long held notion of a single large anti-cyclonic cell, the Comoros Gyre. Limited knowledge exists about the meso-scale activity within the basin, a potential key source of variability for the Mozambique Channel and subsequently the Agulhas Current. In this paper an automated eddy tracking scheme, applied to satellite altimetry data and a high resolution model simulation, is used to determine the characteristics of the anti-cyclonic eddies generated in the Comoros Basin. The generation and characteristics of cyclonic eddies are also investigated. The eddy tracking scheme revealed that anti-cyclonic eddies are primarily generated west of the tip of Madagascar due to barotropic instabilities whereas cyclonic eddies are mainly generated along the northwest coast of Madagascar as a result of baroclinic instabilities. Anti-cyclonic eddies, with a mean lifespan of about three months, reside in the basin for half their lifespan before propagating into the Mozambique Channel. On the other hand, the majority of cyclonic eddies, with a similar mean lifespan, dissipate within the basin. Initially the anti-cyclones, with translation speeds of 6-8km day -1 and mean radii of 80-100km, follow the trajectory of the North East Madagascar Current and turn south upon reaching the African coast. The cyclonic eddies tend to be smaller (~60km) and have slower translation speeds (2.5-3.5km day -1 ) than their anti-cyclonic counterparts.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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