Pacific Ocean temperatures have never been this high in 650 years

We’ve all heard that temperatures are rising. But in the southwestern Pacific, around the Fijian archipelago, sea surface temperatures have hit an all-time high — the highest in over six centuries — greatly harming coral in the region.

This startling discovery, revealed through coral research, comes from an international team of experts in climate science, proving once more the severe implications of rising temperatures.

In fact, the team’s research indicates that 2022 was the hottest year in these regions since 1370. These findings were revealed by examining a massive colony of Diploastrea heliopora, a giant coral species found in Fiji.

Coral reefs in rising sea surface temperatures

Aside from their breathtaking beauty and diverse ecosystems, coral reefs serve as profound archives of past climatic and environmental shifts. 

Specifically, changes in the chemical composition of these long-lived massive corals provide invaluable data that traces centuries of climatic changes in the tropics, shaping the narrative of human experiences with climate fluctuations.

A notable scientist contributing to this research is Professor Denis Scholz, head of the Isotope-geochemical Palaeoclimatology / Speleothem Research group at the Johannes Gutenberg University Mainz (JGU) Institute of Geosciences.

Coral colony and sea temperatures 

Speaking of valuable, the team procured a 2-meter-long (6.5-foot) core from the aforementioned giant coral colony.

Considering the coral only grows 3 to 6 millimeters (0.12 to 0.24 inches) annually, this is no small feat.

Experts then analyzed the core’s skeletal chemical composition, drawing conclusions on temperature variations spanning 627 years.

This data was further enriched by 26 years of instrumental water temperature measurements.

Ever heard of the El Niño-Southern Oscillation? It’s one of the primary phenomena influencing global climate, affecting human activities and natural ecosystems across the globe. 

The southwestern Pacific region plays a significant role in modulating this very oscillation.

Living temperature sensors

We have thermometers and other temperature measuring devices. But nature has provided researchers with living temperature sensors in the form of corals.

These underwater wonders record the chemical composition of their surrounding ocean in their skeletons, day in and day out.

One particular aspect of this recording is the skeletal Strontium to Calcium ratio. When this ratio dips, it points to higher temperatures.

According to Professor Denis Scholz, head of the Isotope-geochemical Palaeoclimatology / Speleothem Research group at the JGU Institute of Geosciences, the current Strontium/Calcium ratio in the Fijian archipelago coral implies the highest sea surface temperature in the past 653 years.

“We used the uranium-thorium dating method to determine the age of each deposited layer. Thus, we were able to independently check and finally confirm the identification of the counting of individual annual layers. This enabled the precise and absolute dating of the coral,” explained Scholz.

Looking through past to predict future

These findings don’t merely paint a picture of our past, but they also provide a glimpse into our future. 

Given the current climate model simulations, researchers are predicting more frequent bouts of droughts and heavy rainfall events in different areas of the Pacific throughout the 21st century. 

And if no measures are taken to counter these effects, the results could be disastrous for both the ecosystems of the vulnerable Pacific islands and their inhabitants.

Implications for marine biodiversity

The rich marine life in the southwestern Pacific is under threat from the rising temperatures of its seas. Coral reefs, which are like underwater rainforests, are home to about 25% of all ocean species. 

Warmer water temperatures can lead to coral bleaching, which harms these beautiful ecosystems and reduces the variety of life they support. 

This not only affects the corals themselves but also disrupts the natural balance among species and threatens the health of fisheries that island communities rely on for food and income.

Uniting for a common goal

This alarming study is a result of global collaboration spanning three continents. 

Involved universities and organizations include Universidad Nacional Autónoma de México (UNAM), Universidad Autónoma de Baja California, the University of Leicester, the University of New South Wales (UNSW), Monash University, Université de Bordeaux, the Helmholtz-Zentrum Hereon, and Johannes Gutenberg University Mainz.

In the face of these startling revelations on rising sea surface temperatures, how will you respond? Let’s redefine our approach to ecological responsibility.

The study is published in the journal Science Advances.

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