The sea surface temperature in the Fijian archipelago in the southwestern Pacific has reached its highest level in more than 600 years, according to a new study by an international research team. Utilizing a new coral record obtained from a giant colony of Diploastrea heliopora in Fiji, the scientists concluded that 2022 was the warmest year in the region since 1370. These massive corals act as vital archives of past climate variability, recording long-term climatic and environmental changes in their chemical composition over centuries.
To gather data for the reconstruction, the team collected a more than 2-meter-long core from the slowly growing coral colony and analyzed its skeletal chemical composition. This was combined with 26 years of instrumental measurements of water temperatures to determine temperature variations over the course of 627 years. The southwestern Pacific region plays a significant role in climate variability, influencing phenomena such as the El Niño-Southern Oscillation, which has global implications for human activities and natural ecosystems.
Corals, with their long lifespan, serve as living temperature sensors by reflecting the chemical composition of the surrounding ocean in their skeletons. By tracking changes in the ratio of skeletal Strontium over Calcium, researchers can gauge temperature fluctuations. The study revealed that current sea surface temperatures in the Fijian archipelago are the highest in 653 years, with persistent warming rates in the western and central Pacific potentially impacting ecosystems and nations in the region. This research also highlights how late 20th-century warming has synchronized ocean temperature trends across the tropical and subtropical Pacific Oceans, leading to significant shifts in rainfall patterns.
The study represents a collaboration between institutions from three continents, including the Universidad Nacional Autónoma de México, Universidad Autónoma de Baja California, the University of Leicester, the University of New South Wales, Monash University, Université de Bordeaux, the Helmholtz-Zentrum Hereon, and Johannes Gutenberg University Mainz. Using the uranium-thorium dating method to determine the age of coral layers, researchers were able to provide a precise and absolute timeline for the reconstruction. The findings suggest that without intervention, Pacific Island nations and their ecosystems will face detrimental impacts from increased droughts, heavy rainfall events, and other consequences of rising sea temperatures in the region.