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Imagine being able to go back tens of thousands of years to see how the coral reefs thrived around the Hawaiian Islands, or being able to compare what the climate was like. An international scientific research expedition is setting out to do just that. An international scientific research expedition, carried out on behalf of the International Ocean Discovery Program (IODP) and including local partners at the University of Hawaiʻi and the state, aims to recover a record of past climate and reef conditions off the coast of Hawaiʻi Island. The two-month research expedition will start at the end of August.

Coral reef ecosystems and sea-level change are both impacting the islands, making this research important to everyone in Hawaiʻi. UH Mānoa’s School of Ocean and Earth Science and Technology studies coral reefs and shoreline geology where Professor Kenna Rubin, an inorganic geochemist at UH Mānoa’s Department of Earth Sciences, is participating in the expedition.

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“These detailed, high-resolution temporal and compositional records anticipated from this expedition will add greatly to our knowledge of past local oceanographic, climate and sea level responses to climate change, as well as helping scientists better understand the volcanic subsidence history of the Big Island,” said Rubin.

Critical piece for future mitigation

The impacts of this research in Hawaiʻi will be adding to existing studies of sea-level change as recorded here by coral reefs, particularly during large fluctuations in sea level that happened during climate instabilities and ice sheet collapses. Such information is a critical piece of future climate-change mitigation and resilience strategies.

Coral reefs are very sensitive to sea level and other changes in environmental conditions. As fossils, they provide a record of past conditions over hundreds, thousands and millions of years of Earth’s history. There is, however, a discontinuity in the global record over the past 500,000 years, especially during periods of major and abrupt climate instability. The IODP Expedition 389 “Hawaiian Drowned Reefs” focuses on this missing link and is led by co-chief scientists: Professor Christina Ravelo, Ocean Sciences Department at the University of California, Santa Cruz; and Professor Jody Webster, School of Geosciences, University of Sydney, Australia.

“The Hawaiʻi fossil reefs are storytellers of the past climate and ocean changes and of the reef ecosystem responses to those changes,” said Ravelo. “We are eager to unlock and share these stories through careful study of the fossils that we hope to recover.”

The expedition aims to recover cores from water depths between 134 and 1,155 meters at a maximum of 20 locations. Even though this will be the first time that a seafloor coring system will be deployed in this area, the anticipated sites are well studied.

“We hope that information recorded in the fossil reefs will help scientists make improved predictions about the rate and magnitude of sea-level rise, what impact global warming and cooling has on short-term climate phenomena like droughts, floods and marine heat waves, and how coral reef ecosystems respond to these changes,” said Webster.

In order to recover the material that scientists will use for their analyses in the coming years, a seafloor corer will be deployed off the multipurpose vessel MMA VALOUR during the expedition. The seafloor corer will be provided and operated by a renowned geotechnical industry specialist, to be lowered to the ocean floor to recover up to 110-meter-long cores beneath the seabed.

Scientists from Australia, Austria, China, Denmark, France, Germany, India, Japan, the Netherlands, Great Britain and the United States will participate in the expedition.

The cores will be archived and made accessible for further scientific research after a one year-moratorium period following the onshore phase of the expedition. All expedition data will be open access and resulting outcomes will be published.

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