Ocean temperatures along Costa Rica’s Pacific coast are running unusually high, with researchers recording water up to 2°C (3.6°F) warmer than normal in some areas. One of the most striking readings came from Playa Herradura on the Central Pacific coast. A monitoring station recorded a surface temperature of 32.6°C (90.7°F) on August 18, well above the station’s average of 29.4°C (84.9°F).
Several readings at Herradura reached or exceeded 32°C (89.6°F) during August, according to data discussed by Rodney Mora, an oceanographer and physicist with the University of Costa Rica’s Center for Research in Marine Sciences and Limnology, known as CIMAR. The warmer water is being influenced by El Niño, a natural climate pattern that raises temperatures across the tropical Pacific. However, Mora said El Niño does not fully explain what researchers are seeing. The longer-term warming of the planet’s oceans is also contributing.
The heat is not evenly distributed and temperatures in the equatorial Pacific have risen as much as 3°C (5.4°F) above normal, while waters closer to Costa Rica have generally registered increases of up to 2°C. For anyone going to the beach, warmer water may seem like little more than a noticeable change while swimming. The broader consequences, however, can be serious.
Higher ocean temperatures place coral reefs under stress and can cause coral bleaching, a process in which corals lose the algae that provide much of their color and energy. Prolonged or repeated bleaching can weaken reefs and affect the fish and other species that depend on them.Marine animals may also move to cooler waters, potentially changing where fish are found and affecting coastal communities that depend on fishing and tourism.
Warm water expands as its temperature rises, adding to sea-level increases. Combined with strong waves and unusually high tides, this can worsen coastal flooding and erosion in already vulnerable areas. That concern is particularly relevant along the Puntarenas coast. A separate UCR study found that Caldera has lost about 22 meters (72 feet) of beach since 2014, with the shoreline retreating at an estimated rate of 1.76 meters (5.8 feet) per year. Researchers said warmer water, high tides, waves and El Niño could combine to increase flooding risks.
CIMAR measurements taken over nearly four decades in the Gulf of Nicoya show a continuing rise in sea temperature. If that trend remains unchanged, researchers estimate the increase could reach approximately 2.2°C (4°F) over a century.Costa Rica’s Caribbean waters are also warming. Records indicate an increase of roughly 0.02°C per year, or about 0.2°C per decade.
Researchers say the findings highlight the need for better coastal planning and continued monitoring. Communities that rely heavily on beaches, fisheries and marine tourism are likely to face the greatest effects if unusually warm conditions become more frequent
