Controls on rainfall variability in the tropical South Pacific for the last 350 years reconstructed from oxygen isotopes in stalagmites from the Cook Islands

Faraji, Mohammadali, Borsato, Andrea, Frisia, Silvia, Mattey, David P., Drysdale, Russell N., Verdon-Kidd, Danielle C., Malcolm, Roger and Marca, Alina (2022) Controls on rainfall variability in the tropical South Pacific for the last 350 years reconstructed from oxygen isotopes in stalagmites from the Cook Islands. Quaternary Science Reviews, 289. ISSN 0277-3791

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Abstract

The hydroclimate of the South Pacific is highly variable on a range of timescales, however, the brevity of instrumental data in the region complicates the detection and attribution of this variability. Annually laminated speleothems may fill this knowledge gap by providing paleo-hydroclimate proxy data extending beyond the instrumental period. In this study, replicated oxygen isotope (δ 18O) time series from two stalagmites from Pouatea (Pu17) and Nurau (Nu16) caves in the southern Cook Islands were used to reconstruct the variability of effective infiltration over the past 350 years (1672–2019 CE) based on observational rainfall data and cave monitoring and calcite farming experiments. The reconstructed infiltration was then compared to available reconstructions of known climate drivers of the South Pacific. Significant dry and wet periods over the last 350 years were identified based on the δ 18O signal of compact/porous calcite fabric and their δ 13C signals. The hydroclimate significance of these proxies was validated through comparison with the instrumental records. We could not reach an annual resolution of reconstructed infiltration, due to a combination of stable isotope sampling limitations and mixing effects within the aquifer. Nevertheless, the combined δ 18O record of Pu17 and Nu16 identifies that the main driver of infiltration and, hence rainfall variability, in the southern Cook Islands is the location of the South Pacific Convergence Zone (SPCZ), which in turn is modulated by the El Niño Southern Oscillation (ENSO). This study demonstrates the hydroclimate significance of speleothem fabrics when combined with O and C stable isotopes, and adds paleoclimate information to a region that has a paucity of data.

Item Type:	Article
Uncontrolled Keywords:	enso,paleoclimate,rainfall,spcz,stalagmites,δ o,geology,ecology, evolution, behavior and systematics,archaeology,archaeology,global and planetary change,sdg 13 - climate action ,/dk/atira/pure/subjectarea/asjc/1900/1907
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Related URLs:	http://www.scopus.com/inward/record.url?...
Depositing User:	LivePure Connector
Date Deposited:	28 Apr 2023 10:30
Last Modified:	28 Apr 2023 10:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/91905
DOI:	10.1016/j.quascirev.2022.107633

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