Publication in PNAS on changes in ocean circulation in the Gulf of Panama

16 09 2025

Dr Michał Chiliński from the Faculty of Biology at the University of Warsaw, a fellow of the Max Planck Society (Max-Planck-Gesellschaft, MPG), is a co-author of an article published in PNAS demonstrating that in 2025 the trade winds were not strong enough to break through the stable surface layer of the ocean and trigger the so-called upwelling – the process of bringing cold, nutrient-rich deep waters to the surface. As a result, biological production in this region declined dramatically.

An international team of scientists led by researchers from the Smithsonian Tropical Research Institute (STRI) analysed both satellite data from the past 40 years and measurements collected since 2023 from the research yacht s/y Eugen Seibold operated by the Max Planck Institute for Chemistry. For the first time in decades, they observed an almost complete disappearance of the seasonal upwelling phenomenon in the Gulf of Panama. This key oceanographic process, which typically occurs every year from January to April, sustains phytoplankton, supports local fisheries, and protects coral reefs from overheating. In 2025, however, this mechanism suddenly collapsed – it appeared with a delay of several weeks, lasted exceptionally briefly, and was record-breakingly weak.

Dr Chiliński was responsible for comparing the contemporary measurement data with historical atmospheric and oceanic data from the ERA5 reanalysis prepared by the European Centre for Medium-Range Weather Forecasts (ECMWF). The analyses showed that the collapse of the upwelling was an unprecedented phenomenon – for the first time in at least 85 years such a marked weakening of the trade winds was recorded.

The scientists emphasize that the breakdown of such a previously stable mechanism is a warning signal – tropical upwelling systems may be more sensitive to climate change than previously thought. Further research and the development of monitoring systems will be crucial to determine whether the 2025 event was an isolated incident or the beginning of a new trend in this key region of the tropical Pacific.