Fijian coral study reveals over 600 years of rising sea temps across Southwestern Pacific

Fijian coral study reveals over 600 years of rising sea temps across Southwestern Pacific
by Robert Schreiber
Berlin, Germany (SPX) Sep 19, 2024

An international research team has revealed that sea surface temperatures in the southwestern Pacific, particularly around the Fijian archipelago, are currently the highest they have been in over 600 years. The findings stem from a study of coral records, which show that the year 2022 marked the warmest in the region since the year 1370. The research utilized the giant coral species 'Diploastrea heliopora', which provided essential data for reconstructing historical temperature trends. These corals serve as natural archives of climatic changes, with their chemical makeup offering valuable insight into centuries of environmental shifts.

A core sample over two meters in length was extracted from a coral colony in Fiji that grows between 3 to 6 millimeters per year. This core allowed scientists to examine 627 years of temperature variations, augmented by 26 years of direct water temperature measurements. The southwestern Pacific region plays a crucial role in global climate systems, significantly influencing events like the El Nino-Southern Oscillation, which in turn affects weather patterns, human activity, and ecosystems worldwide.

Corals as Indicators of Temperature Changes
The study, co-led by researchers from the Universidad Nacional Autonoma de Mexico and the University of Leicester, presents the longest continuous coral-based reconstruction of sea surface temperatures using the Strontium/Calcium (Sr/Ca) ratio as a proxy. This research offers an unprecedented look at the long-term climatic trends in the Pacific. Scientists from Johannes Gutenberg University Mainz (JGU) contributed by ensuring precise dating of coral growth layers. "We used the uranium-thorium dating method to determine the age of each deposited layer. This enabled us to confirm the accuracy of the annual layer counts," explained Professor Denis Scholz, head of the Isotope-geochemical Palaeoclimatology / Speleothem Research group at JGU.

Due to their long lifespan, corals act as "living temperature sensors." The study found that the Sr/Ca ratio in coral skeletons reflects ocean temperatures, with lower ratios corresponding to higher temperatures. This data indicates that the Fijian sea surface temperatures are currently the highest they've been in 653 years. The synchronization of warming rates between the western and central Pacific could have negative impacts on the ecosystems and communities of Pacific Island nations.

Long-term Climate Insights
The study sheds light on how warming patterns in the tropical and subtropical Pacific have evolved over the last six centuries, showing that temperature changes across these regions have become increasingly synchronized, especially since the late 20th century. This synchronization plays a key role in shifting rainfall patterns in the region. Current climate models predict more extreme weather events, including droughts and heavy rainfall, which could have devastating consequences for Pacific Island inhabitants and their ecosystems if climate change mitigation efforts are not intensified.

A Global Collaboration
The research was a collaborative effort, bringing together experts from institutions across three continents, including Universidad Nacional Autonoma de Mexico, Universidad Autonoma de Baja California, the University of Leicester, the University of New South Wales, Monash University, Universite de Bordeaux, the Helmholtz-Zentrum Hereon, and Johannes Gutenberg University Mainz.

Research Report:Coral Sr/Ca-SST reconstruction from Fiji extending to ~1370 CE reveals insights into the Interdecadal Pacific Oscillation