Why Do Benguela Niños Lead Atlantic Niños?
| Autor: | Joke F. Lübbecke, Marie-Lou Bachèlery, Serena Illig |
|---|---|
| Jazyk: | angličtina |
| Předmět: |
010504 meteorology & atmospheric sciences
Lead (sea ice) 0207 environmental engineering 02 engineering and technology Tropical Atlantic Oceanography 01 natural sciences Physics::Geophysics Geophysics 13. Climate action Space and Planetary Science Geochemistry and Petrology Physics::Space Physics Earth and Planetary Sciences (miscellaneous) 14. Life underwater 020701 environmental engineering Geology Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences |
| Zdroj: | Journal of Geophysical Research: Oceans |
| ISSN: | 2169-9291 2169-9275 |
| DOI: | 10.1029/2019jc016003 |
| Popis: | We 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. |
| Databáze: | OpenAIRE |
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