Abstract
AbstractWe investigate the lag between warm interannual Sea Surface Temperature (SST) events in the eastern‐equatorial Atlantic, the Atlantic Niños, and the occurrence of Benguela Niños along the southwestern Angolan coast. While it is commonly agreed that both events are associated with equatorial and subsequent coastal‐trapped wave propagations driven remotely by a relaxation of the trade‐winds, it is surprising that SST anomalies off Angola tend to precede the ones in the eastern‐equatorial sector by ~1 month. To explain this counterintuitive behavior, our methodology is based on the experimentation with a Tropical Atlantic Ocean model. Using idealized wind‐stress perturbations from a composite analysis, we trigger warm equatorial and coastal events over a stationary and then, seasonally varying ocean mean‐state. In agreement with the linear dynamics, our results show that when the interannual wind‐stress forcing is restricted to the western‐central equatorial Atlantic, the model yields equatorial events leading the coastal ones. This implies that neither the differences in the ocean stratification between the two regions (thermocline depths or modal wave contributions) nor the seasonal phasing of the events explains the observed temporal sequence. Only if wind‐stress anomalies are also prescribed in the coastal fringe, the coastal warming precedes the eastern‐equatorial SST anomaly peak, emphasizing the role of the local forcing in the phenology of Benguela Niños. A weaker South‐Atlantic Anticyclone initiates the coastal warming before the development of eastern‐equatorial SST anomalies. Then, equatorward coastal wind anomalies, driven by a convergent anomalous circulation located on the warm Atlantic Niño, stop the remotely forced coastal warming prematurely.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.