Scientific prospectus
•03 Aug 2023Our understanding of the links and mechanisms that control eustatic sea level and global climate changes has been significantly hampered by a lack of appropriate fossil coral records over the last 500 ky, particularly into and out of the glacial periods.We propose to directly address this problem by drilling a unique succession of drowned coral reefs around Hawaii (USA) now at 134-1155 meters below sea level.Abundant observational and numerical modeling data indicate that the internal stratigraphy and tops of these reefs are highly sensitive to sea level and climate changes, thereby providing a firm template with which to conduct these operations.As a direct result of Hawaii's rapid (2.5-2.6 m/ky) but nearly constant subsidence, a thick (100-200 m) expanded sequence of shallow coral reef dominated facies is preserved within the reefs.These reefs span important periods in the Earth's climate history, and coral reef records are either not available or highly condensed on stable (Great Barrier Reef, Tahiti) and uplifted margins (Papua New Guinea, Barbados) because of a lack of accommodation space and/or unfavorable shelf morphology.Specifically, these data show that the reefs grew (for ~90-100 ky, albeit episodically) into, during, and out of the majority of the last five to six glacial cycles.Therefore, scientific drilling through these reefs will generate a new record of sea level and associated climate variability during several controversial and poorly understood periods over the last 500 ky.