Reconstructing ocean-atmosphere interactions in La Guajira upwelling system through organic and mineral proxies over the past 1800 years Rodriguez-Burgos, A. M. Briceño-Zuluaga, F. J. Evangelista, H. Flores-Aqueveque, V. Nogueira, J. Castillo, A. Quiroga-Camargo, W. E. /Mendez-Millan, Mercedes /Sifeddine, Abdelfettah Late Holocene Southern Caribbean Marine productivity Climate-ocean coupling Sediment geochemistry Climate variability The Caribbean upwelling system enhances the productivity of North Colombian coastal waters, supporting the trophic network and regional biodiversity. Despite knowledge of its mechanisms and drivers, Caribbean upwelling remains understudied, and its response to climate change is uncertain. This study presents the first paleoclimatic reconstruction of upwelling in La Guajira, Colombia (a climate-sensitive region) by analyzing environmental indicators from a marine sediment core (GUACO-4) collected off Bahia Hondita. Organic matter proxies (total organic carbon, total nitrogen, delta 13C, delta 15N) were used to trace its origin and nutrient cycling, while mineral and metal compositions informed ocean-land interactions and thermal changes. Five climatic phases were identified: the Roman Warm Period, the Dark Ages Cold Period, the Medieval Climate Anomaly, the Little Ice Age, and the Current Warm Period. delta 13C values (-21.5 to -19.7 %o) and C/N ratios (4.47-5.90) indicate a mainly marine origin of organic matter, and delta 15N values (4.24 to 5.58 %o) suggest active denitrification. Warm periods aligned with El Nino-like conditions and stronger coupling between the North Atlantic Subtropical High and the Intertropical Convergence Zone, intensifying the Caribbean Low-Level Jet and enhancing productivity. In contrast, during the Little Ice Age, La Nina-like conditions and system decoupling weakened the Jet. Today, increased variability adds uncertainty to future upwelling dynamics. Climate-driven changes in wind patterns could either strengthen or weaken upwelling. This unpredictability could impact marine productivity, with potential consequences for fisheries and local communities that rely on these ecosystems. 2026 text https://www.documentation.ird.fr/hor/fdi:010095903 fdi:010095903 Rodriguez-Burgos A. M., Briceño-Zuluaga F. J., Evangelista H., Flores-Aqueveque V., Nogueira J., Castillo A., Quiroga-Camargo W. E., Mendez-Millan Mercedes, Sifeddine Abdelfettah. Reconstructing ocean-atmosphere interactions in La Guajira upwelling system through organic and mineral proxies over the past 1800 years. 2026, 682, 113461 [11 p.] EN COLOMBIE, LA GUAJIRA ATLANTIQUE NORD CARAIBES MER