Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 46, Issue 21, Pages 12156-12164Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GL083925
Keywords
mesoscale eddies; tropical Atlantic Ocean; altimetry; seasonal variability; barotropic instability
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Funding
- Alti-ETAO project
- French National Institute of Sciences of the Universe (INSU/CNRS)
- EU H2020 TRIATLAS project [817578]
- IRD
- Cultural Cooperation and Action Service (SCAC) of the French Embassy in Benin
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We study mesoscale eddy characteristics in the tropical Atlantic Ocean, using 23 years of daily altimetry sea level anomalies. Eddies are mainly generated in the eastern boundary upwelling systems and in the Brazil Current region. Their westward propagation speed reaches 20 cm/s in equatorial areas, decreasing with latitudes. They present typical amplitudes of 1-5 cm. The largest and most energetic eddies are observed in the equatorial region, especially in the North Brazil Current (NBC) retroflection. The seasonal cycle of the eddy characteristics shows higher amplitudes along the NBC retroflection and the western part of the North Equatorial Countercurrent. A new criterion, based on altimetry data, determines the probability that barotropic instability of mean surface currents is responsible for eddy generation. We find a strong likelihood that the latter plays a key role along the North Equatorial Countercurrent, whereas other mechanisms must be invoked for the NBC region.
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