Upwelling refers to the rising of deep ocean waters. For the first time in decades, this phenomenon has collapsed in the Gulf of Panama. The previously stable mechanism, which is crucial for marine ecosystems and the local economy, appeared late, lasted only briefly and was record-breakingly weak. This was investigated by an international team of scientists, including Dr Michał Chiliński from the Faculty of Biology at the University of Warsaw. The results of the study were published in the journal “PNAS”.
For decades, seasonal upwelling in the Gulf of Panama has provided cool, nutrient-rich waters, fuelled phytoplankton, which forms the basis of marine food chains, supported high fisheries productivity and provided natural “cooling” of coral reefs, protecting them from the effects of heat stress and bleaching.
In 2025, this stable mechanism suddenly collapsed – the phenomenon began with a delay of several weeks, lasted for a record short time and was exceptionally weak. Researchers link it to atmospheric anomalies and warn that similar episodes could threaten ecosystems and economies dependent on tropical upwelling systems in the future.
The results of the research conducted by a team of scientists led by the Smithsonian Tropical Research Institute (STRI) were published in the journal “PNAS”. Dr Michał Chiliński from the Faculty of Biology at the University of Warsaw also participated in the research.
Warning signal
For at least four decades, the Gulf of Panama has experienced an exceptionally stable and predictable seasonal upwelling phenomenon – trade winds from the north between January and April brought cool, nutrient-rich deep waters to the surface. This process was fundamental to the functioning of the entire ecosystem.
However, in 2025, an unprecedented collapse occurred. The collected data – both satellite data from the last 40 years and long-term in situ measurements – indicate that the upwelling appeared more than six weeks late, lasted only 12 days (its average length is 66 days) and reached minimum temperatures (23.3°C), while historical values reached as low as 14.9°C. This means not only a radical shortening of the ocean surface cooling period, but also a significant weakening of the entire phenomenon.
Analyses indicate that the source of the problem was unusual wind conditions. Although the episodes of northerly winds themselves were similar in strength to those in previous years, they occurred much less frequently, were shorter and had less effect on the ocean surface. The total “wind stimulus” driving upwelling was therefore unprecedentedly low.
“The consequences of such a collapse could be extensive and severe. It is highly likely that primary productivity, i.e. the ocean’s ability to produce biomass at the base of food webs, will decline, which will directly affect not only the ecosystem but also the region’s economy, particularly fisheries. In addition, the lack of cool water inflow increases the vulnerability of coral reefs to prolonged heat stress and mass bleaching,” says Dr Michał Chiliński, adding: “The collapse of this rhythm in the environment disrupts the stability of ecosystems and, consequently, the security of the communities that depend on it. We must remember that the good condition of the environment and the stability of diverse ecosystems should be treated as a priority not only by environmental researchers, but by everyone who takes the future of humanity seriously.”
The authors of the study emphasise that this is a warning sign: tropical upwelling systems, despite their enormous ecological and economic importance, remain poorly monitored and studied. In the context of global climate change, their stability may be fragile and locally sensitive to changes in atmospheric circulation. It is therefore crucial to strengthen observation systems, develop forecasting models and improve our understanding of the links between oceanography, ecology and human activity. Only in this way can we assess whether the event of 2025 was a unique incident or the beginning of a new trend that will radically transform living conditions in one of the key regions of the tropical Pacific.
Contribution of the UW researcher
Data collected on board the Max Planck Institute for Chemistry’s research yacht s/y Eugen Seibold, which has conducted numerous measurements in the Gulf of Panama and the open Pacific since 2023, also played a key role in the research. Analyses showed that in 2025, the trade winds were unable to break through the stable surface layer of the ocean, which prevented effective upwelling and led to a decline in biological production.
Dr Michał Chiliński from the UW’s Faculty of Biology, a Max Planck Society (Max-Planck-Gesellschaft, MPG) scholarship holder, was responsible for comparing contemporary measurement data with historical atmospheric and oceanic analyses from the ERA5 reanalysis of the European Centre for Medium-Range Weather Forecasts. The results confirmed the uniqueness of this year’s anomaly – for the first time in at least 85 years, such a marked weakening of the trade winds was recorded in the first months of the year, and thus a disturbance of the entire upwelling system.
Since 2022, Dr Chiliński has been collaborating with the Max Planck Institute for Chemistry, including the research team of s/y Eugen Seibold, as part of which miniature stations for measuring atmospheric aerosols developed in the MICE (Micro Instruments to Characterise atmospheric Environment) project were installed on board the yacht. These sensors, operating almost continuously despite difficult ocean conditions, have provided unique data and, in 2025, enabled the programme to be expanded with further research installations.
