ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Coastal Ocean Processes
Disentangling Eastern Pacific Warming: El Niño 2023–2024 vs Seasonal Panamá Bay Influence
Provisionally accepted
Franklin Isaac Ormaza-González1*
Carlos Martillo-Bustamante1
Elvis Espinoza Villacís1Jean-Noel Proust2Francois Michaud3Jean-Frederic Lebrun4- 1ESPOL Polytechnic University, Guayaquil, Ecuador
- 2Universite de Rennes, Rennes, France
- 3Sorbonne Universite, Paris, France
- 4Universite des Antilles, Pointe-a-Pitre, Guadeloupe
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Understanding the drivers of coastal ocean warming in the eastern Pacific is critical for distinguishing local variability from large‑scale climate phenomena such as El Niño. This study tests the hypothesis that anomalous warming in northern Ecuadorian coastal waters during January 2024 was primarily driven by the seasonal intrusion of Panamá Bay waters rather than the developing 2023–2024 El Niño event. Oceanographic and meteorological data were collected aboard the Pourquoi Pas? research vessel and compared against climatology (1940–2024), the 1997–1998 El Niño, and satellite observations. Winds were predominantly westerly, exceeding climatological averages while sea surface temperatures showed a pronounced south–north gradient. Salinity and mixed‑layer depths remained within seasonal ranges. The Intertropical Convergence Zone persisted north. Comparative analysis revealed weak or absent El Niño signals, with no discernible climatic impacts, wind, rain, thermocline and 20 C depths, T/S relationships, which were within seasonal values corroborated with biological and meteorological indicators. Instead, the seasonal incursion of Panamá Bay waters was the dominant warming driver. These findings refine understanding of eastern Pacific variability and provide the first deep profiles from this region, including serendipitous evidence of Antarctic Intermediate Water at ~1500-2000 m, thereby enhancing observational coverage in a historically undersampled area.
Keywords: Eastern Pacific, El Niño, Halocline, Panamá Bay, thermocline
Received: 31 Oct 2025; Accepted: 09 Dec 2025.
Copyright: © 2025 Ormaza-González, Martillo-Bustamante, Espinoza Villacís, Proust, Michaud and Lebrun. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Franklin Isaac Ormaza-González
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