For more than 40 years, the Gulf of Panama experienced a predictable seasonal ocean cooling phenomenon that supported marine biodiversity, fisheries and coral reefs. However, in 2025, this natural process weakened dramatically lasting just 12 days instead of its usual 66 days according to a new scientific study.
The phenomenon known as ocean upwelling, normally occurs between December and April when northerly winds push warm surface water away from the coast. This allows colder, nutrient-rich water from deeper ocean layers to rise, supporting phytoplankton growth and sustaining the marine food web.
Researchers from the Smithsonian Tropical Research Institute, the Max Planck Institute for Chemistry and collaborating institutions identified the 2025 season as the weakest in at least four decades.
Upwelling Season Delayed and Reduced by 82%
The disruption was significant. Instead of beginning around January 20, the cooling period started on March 4, a delay of approximately 42 days. It lasted only 12 days, compared with the historical average of 66 days representing an 82% reduction.
The coldest water temperature recorded during the season was 23.3°C, considerably warmer than the historical seasonal minimum of around 19°C.
Satellite observations also detected an unusually weak cooling signal, indicating that the normal movement of nutrient rich deep water towards the surface had been substantially reduced.
Unusual Wind Patterns Behind the Disruption
Scientists primarily linked the weakened upwelling to changes in northerly wind patterns. These winds normally drive the seasonal movement of deeper water, but during 2025 they occurred less frequently and lasted for shorter periods.
Although some individual wind events remained strong they did not continue long enough to sustain the usual cooling process.
Measurements collected aboard the research vessel S/Y Eugen Seibold also revealed unusually strong layering or stratification, in the water column. This restricted the mixing of deeper and surface waters.
Researchers identified a possible connection with the position of the Intertropical Convergence Zone during the 2024–2025 La Niña episode. However, the precise atmospheric causes remain uncertain. The study does not establish that human-caused climate change directly triggered the event.
The weakening of upwelling could have consequences throughout the marine ecosystem. Deep ocean water normally supplies nutrients that encourage phytoplankton growth, forming the foundation of the food chain.
A reduction in this nutrient supply could affect marine species such as sardines, mackerel and squid, which depend directly or indirectly on the productivity supported by upwelling.
The disruption could also create difficulties for commercial and small scale fisheries, potentially affecting the livelihoods and food security of coastal communities.
Coral reefs face an additional concern. Cold water rising from deeper ocean layers provides natural relief from tropical heat. With this cooling mechanism weakened, corals could experience prolonged thermal stress, increasing their vulnerability to bleaching.
Scientists caution that the study documented changes in ocean temperatures and wind patterns but did not establish the extent of any resulting fishery losses, coral bleaching or other ecological damage.
Scientists Call for Stronger Ocean Monitoring
The Panama event highlights how vulnerable tropical ocean systems can be to changes in atmospheric circulation. Despite their importance to marine ecosystems and coastal economies, tropical upwelling regions remain less extensively monitored than several major upwelling systems in temperate regions.
Researchers believe that combining satellite observations, oceanographic sensors, research vessel measurements and improved climate models will be essential to identifying future disruptions.
The findings published in the journal Proceedings of the National Academy of Sciences, underline the importance of understanding seasonal ocean processes and their influence on biodiversity, fisheries and coastal communities.
Whether the 2025 disruption was an isolated anomaly or an early indication of more frequent changes remains uncertain. However, scientists warn that repeated weakening of upwelling could have far reaching consequences for tropical marine ecosystems and the people who depend on them.