Unraveling glacial hydroclimate in the Indo‐Pacific Warm Pool: perspectives from water isotopes

Type Article
Date 2020-12
Language English
Author(s) Windler Grace1, Tierney Jessica E.1, Zhu Jiang2, Poulsen Christopher J.2
Affiliation(s) 1 : Department of Geosciences University of Arizona Tucson AZ ,USA
2 : Department of Earth and Environmental Sciences University of Michigan Ann Arbor MI ,USA
Source Paleoceanography and Paleoclimatology (2572-4517) (American Geophysical Union (AGU)), 2020-12 , Vol. 35 , N. 12 , P. e2020PA003985 (17p.)
DOI 10.1029/2020PA003985
Keyword(s) leaf wax, water isotopes, Indo‐Pacific Warm Pool, Pleistocene, proxy‐model comparison
Abstract

The Indo‐Pacific Warm Pool (IPWP) is home to the warmest sea surface temperatures in the world oceans, favoring strong tropospheric convection and heavy rainfall. The mechanisms controlling long‐term change in the region’s hydroclimate are still uncertain. Here, we present a 450,000‐year record of precipitation δD from southern Sumatra that records a consistent pattern of glacial isotopic enrichment and interglacial depletion. We synthesize existing paleo‐indicators of precipitation δD and δ18O in the IPWP and compare results with water isotope‐enabled climate simulations of the Last Glacial Maximum (LGM). The simulations show glacial isotopic enrichment over the eastern Indian Ocean extending into the southern IPWP and isotopic depletion over southeast Asia, the west Pacific, and Australia. The pattern of simulated LGM isotopic change agrees generally well with our proxy synthesis. We conclude that reorganization of regional circulation under glacial conditions controls precipitation isotope variability in the IPWP: low‐level tropospheric convergence dominates the signal in the north/east, whereas divergence controls the response in the south/west. Additional sensitivity simulations suggest that the LGM ice sheets and the associated lowering in sea level, rather than decreased greenhouse gases, are responsible for the distinctive spatial pattern in glacial changes of precipitation isotopes and hydroclimate across the IPWP.

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