Suppression of local upwelling in the Gulf of Panama predicted a season in advance

Abstract. Wind-driven upwelling of subsurface ocean waters to the surface ensures nutrient-rich waters reach the epipelagic zone, supporting some of the most diverse ecosystems and largest fish stocks in the global ocean. In early 2025, the Gulf of Panama experienced a collapse of the local upwelling system not previously observed in historical records, with notable impacts on regional physical and biogeochemical conditions. Predictability of upwelling collapse in relatively local systems on seasonal timescales has yet to be assessed. Here, the predictability of upwelling in the Gulf of Panama is explored in an operational seasonal forecasting system. First, the extreme weakening of the northerly jets driving upwelling and the corresponding extreme sea surface temperatures of 2025 are shown to have been accurately predicted a season in advance. Crucially, hindcasts from the period 1993 to 2024 demonstrate high probabilistic and deterministic skill, and also capture the strong upwelling of 1998. By validating against a high-resolution global ocean reanalysis, an increase in temperature forecast skill with depth is uncovered, making the case for exploiting subsurface information for improved early-warning and description of upwelling events. Lastly, the occurrence of warm upwelling, specifically in 1998, raises a discussion of the most suitable upwelling indicators for the region. The seasonal forecast system sufficiently resolves wind stress-derived Ekman Pumping and the exceptionally weak vertical ocean velocity in 2025. This study demonstrates the capability of seasonal forecasts to provide early warning of upwelling collapse.