For the first time, an international research team has succeeded in obtaining a high-resolution continuous record of environmental data from shallow-water corals off the coast of Hawai’i (USA) by coring fossil coral reefs. These cores were obtained during an International Ocean Discovery Program (IODP) expedition led by Co-Chief Scientists Professor Jody Webster (School of Geosciences, the University of Sydney, Australia) and Professor Christina Ravelo (Ocean Sciences Department at the University of California, Santa Cruz, USA). The cores have now been opened, analyzed and sampled by the scientific team, following almost a month of intensive work at the University of Bremen during February 2024. Professor Hildegard Westphal from the Leibniz Centre for Tropical Marine Research (ZMT) and the University of Bremen was also actively involved in the on-shore phase of the IODP Expedition 389 “Hawaiian Drowned Reefs”

The expedition aimed to recover a record of past climate and reef conditions off the coast of Hawai’i. During the offshore phase of the expedition a total of 426 meters of cores were recovered from below the seabed at water depths from 130 to 1240 meters. Corals store past environmental conditions in their skeletons. Researchers will use cutting-edge methods in their laboratories to extract information about sea level or climate changes from these tremendously important high-resolution archives. Looking back in Earth’s history will provide valuable insight into the mechanisms that cause climate change, including abrupt events, and into the impact of these changes on reef growth and health.

Prof. Jody Webster: “We were able to recover a spectacular sequence of fossil coral reef deposits that will enable us to decipher in unprecedented detail, how sea level, paleoclimate and the reef ecosystem has changed over the past 500,000 years, particularly during periods of rapid global change.”

Detailed and partly seasonal climate records

The expedition is the culmination of many years of planning to carefully select the best locations to obtain records of past changes to inform and test important climate change theories. Prof. Christina Ravelo: “We are also delighted to have recovered many samples of annually banded fossil corals that will be used to obtain for the first time, detailed records of monthly changes in oceanographic conditions from past periods that were different than today. The idea is to use this data to inform predictions of future Pacific-wide climate change.”

Carefully curated drill cores of high scientific interest

“IODP is comparable to the International Space Station - only for geologists. It is a high-caliber, international collaboration that deliberately creates a legacy for future researchers alongside highly interesting science. In the end, carefully curated drill cores of high scientific interest, including all metadata and scientific background information, will be available for future research,” says Hildegard Westphal about the significance of the IOPD expedition.

“These cores provide unique information on how coral reef ecosystems are responding to rapid sea level rise. Although coral reefs are adapted to grow with rising sea levels, they drown during rapid surges in sea level rise. But how this drowning occurs and what really forces the reefs to give up is not yet fully understood. These cores cover a range of glacial and interglacial sea level cycles and provide a detailed record not previously available. This allows us to learn about the significance of modern sea level rise,” says Westphal, head of the Geoecology and Carbonate Sedimentology research group at ZMT.

Reconstructing temperature fluctuations in the North Pacific for the past 500,000 years

“The fossil corals recovered on IODP Expedition 389 off Hawai'i will allow us for the first time to reconstruct temperature fluctuations in the North Pacific for the past up to 500,000 years, especially interannual and seasonal fluctuations. Temperature variations on these socially relevant time scales play an important role in today's climate change and the resulting extremes such as marine heat waves,” says expedition participant Dr. Thomas Felis. At MARUM - Center for Marine Environmental Sciences at the University of Bremen, he heads the Coral Paleoclimatology working group and is coordinator of the priority program "Tropical Climate Variability & Coral Reefs" (SPP 2299) funded by the German Research Foundation (DFG). This Germany-wide joint project is thematically linked to the current IODP expedition - three other researchers from the Priority Program are also part of the international research team. ”The records from the Pacific will also contribute to a better understanding of climate variability in the tropical-subtropical oceans and its impact on the coral reef ecosystem in a warming world, one of the main objectives of SPP 2299, which works particularly in the current and past warm periods.”

Data analysis for a better understanding of the Earth system

The scientific objectives of the expedition aim to address questions on four main topics:

• To measure the extent of sea level change over the past half a million years
• To investigate why sea level and climate changes through time
• To investigate how coral reefs respond to abrupt sea level and climate changes, and
• To improve scientific knowledge of the growth and subsidence of Hawai’i over time.

The Science Team of IODP Expedition 389 includes 31 scientists of different disciplines from Australia, Austria, China, Denmark, France, Germany, Great Britain, India, Japan, the Netherlands, Spain and the USA, ten of whom sailed onboard the multipurpose vessel MMA Valour in September and October 2023 off the coast of Hawai’i, to collect the cores and data using a remotely operated coring system. After the offshore phase, the whole Science Team met at the IODP Bremen Core Repository, at MARUM – Center for Marine Environmental Sciences at the University of Bremen, Germany, in February 2024 to split, analyze and sample the cores and begin to interpret the data collected. The scientists will continue to work on samples and data over the next years in their home laboratories in depth to decipher detailed information from this unique new material and associated data.
The cores will be archived and made accessible for further scientific research by the international scientific community. After the one year-moratorium period following the onshore phase of the expedition material and data will become open access. Resulting findings will be published over the next months and years.

The expedition is conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of the International Ocean Discovery Program (IODP). IODP is a publicly-funded international marine research program supported by 21 countries, which explores Earth's history and dynamics recorded in seafloor sediments and rocks, and monitors sub-seafloor environments. Through multiple platforms – a feature unique to IODP – scientists sample the deep biosphere and sub-seafloor ocean, environmental change, processes and effects, and solid Earth cycles and dynamics.
The ECORD Science Operator has extensive experience working in sensitive ecosystems such as coral reefs, following seagoing expeditions to the Great Barrier Reef (Australia, 2010) and Tahiti (2005).

More Information:
About the expedition – About the research program – About the European part of the program – and Mission-Specific Platform expeditions - Frequently Asked Questions: Offshore Expedition Logbook: