Fijian coral reveals new 627-year record of Pacific Ocean climate

An international team of climate scientists has used a 627-year coral record in Fiji to reveal unprecedented insights into ocean temperatures and climate variability in the Pacific Ocean since 1370.

The study published in Scientific progressco-authored by Dr Ariaan Purich of Monash University and Professor Matthew England and Dr Rishav Goyal of UNSW, shows how human-induced climate change interacts with long-term patterns of climate variability in the Pacific.

The new coral records show that local ocean temperatures were warm between 1380 and 1553, comparable to those of the late 20th and early 21st centuries. However, when combined with other coral records, the observed Pacific-wide warming since 1920, largely due to human-induced emissions, marks a significant departure from the natural variability recorded in previous centuries.

The records also show that the current ocean temperature is the highest in 653 years.

This work provides new insights into how climate trends are driving changes in weather patterns and more extreme weather events that will have significant implications for millions of people living in the Indo-Pacific region.

Ocean temperatures influence coral growth, which preserves traces of past environmental conditions over centuries. This remarkable 627-year coral record (1370–1997) provides the longest continuous reconstruction of sea surface temperature to date.

The study comes a week after scientists revealed in Nature a 400-year coral record showing how the Great Barrier Reef is facing catastrophic damage from record ocean temperatures.

The team used coral data from Fiji to reconstruct the Pacific Interdecadal Oscillation, a large-scale phenomenon that influences climate variability in the Pacific Ocean, nearly doubling the length of previous reconstructions. This long reconstruction allowed for examination of the interaction between variability and climate change, revealing atypical basin-wide warming over the past century.

Dr Ariaan Purich said understanding long-term climate variability in the Pacific is essential for predicting future climate change.

“This new, long reconstruction helps us disentangle the climate change signal from natural variations in the Pacific. Understanding the past helps us project future climate change; our new reconstruction shows us that current Pacific-wide warming is a hallmark of the era of climate change.”

The study was led by Dr Juan Pablo D’Olivo of the National Autonomous University of Mexico and Professor Jens Zinke of the University of Leicester, in collaboration with an international team of Earth and climate scientists from Mexico, the UK, France, Germany and Australia.

The new record is based on a geochemical analysis of the Sr/Ca ratio in coral – an indicator of past ocean temperature – that was collected from a colony of a giant boulder coral called Diploastrea heliopora in the Fiji archipelago.

Dr Ariaan Purich said the findings have many implications for future climate.

“Temperature variations in the Pacific influence weather systems. Large-scale warming can lead to a drying climate in the Coral Sea region. This will impact the populations and ecosystems of vulnerable Pacific island nations.”

The study provides further motivation for the international community to continue working to limit warming to 1.5°C by developing large-scale renewable energy resources, electrifying the economy and phasing out coal and gas.