Preprints
https://doi.org/10.5194/egusphere-2025-4429
https://doi.org/10.5194/egusphere-2025-4429
26 Sep 2025
 | 26 Sep 2025
Status: this preprint is open for discussion and under review for Ocean Science (OS).

Intraseasonal modulation of Sea Surface Temperatures in the North Tropical Atlantic by African Easterly Waves

Marc Kakante Mendy, Florent Gasparin, Manon Gévaudan, Moussa Diakhaté, Issa Sakho, and Julien Jouanno

Abstract. The sea surface temperature (SST) variability in the North Tropical Atlantic plays a crucial role in the regional climate by modulating the Intertropical Convergence Zone (ITCZ) and influencing precipitation, convective systems, and tropical cyclones. While atmospheric synoptic-scale intraseasonal variability in this region is dominated by African Easterly Waves (AEWs), their impact on SST remains poorly understood. This study investigates the modulation of SST by AEWs using a regional configuration of a coupled ocean-atmosphere model and PIRATA mooring air-sea observations. Results reveal a significant AEWs signature in SST anomalies, with temperature fluctuations exceeding ±0.5 °C. A heat budget analysis shows that AEWs mainly influence SST through modulation of the latent heat flux, shortwave radiation, and vertical mixing. The contribution of the ocean mixing and that of the air-sea fluxes appear of similar order, likely reflecting the influence of near-inertial currents. The dominant 3–5-day AEWs exhibit a stronger impact than their 6–9-day counterparts. These findings highlight the role of AEWs in driving SST variability and mixed-layer dynamics, underscore the importance of accurately representing them in coupled climate models, and call for further investigation into their influence on the mean and seasonal upper-ocean state.

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Marc Kakante Mendy, Florent Gasparin, Manon Gévaudan, Moussa Diakhaté, Issa Sakho, and Julien Jouanno

Status: open (until 21 Nov 2025)

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  • AC1: 'Comment on egusphere-2025-4429', Marc Kakante Mendy, 01 Oct 2025 reply
Marc Kakante Mendy, Florent Gasparin, Manon Gévaudan, Moussa Diakhaté, Issa Sakho, and Julien Jouanno
Marc Kakante Mendy, Florent Gasparin, Manon Gévaudan, Moussa Diakhaté, Issa Sakho, and Julien Jouanno

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Short summary
The North Tropical Atlantic plays an important role in shaping climate in the region. In our study we examined how African Easterly Waves influence the ocean surface. Using numerical modelling and buoy records, we found that these waves can warm or cool the sea by more than half a degree. The faster waves have the strongest impact. Because sea temperature affects rainfall and storms, understanding these waves can help improve weather and climate forecasts.
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