The Holocene (0–11.7 ka BP) appears warm and stable in ice core and global temperature reconstructions as well as in transient climate simulations. This seeming quiescence of Earth's climate belies large secular changes in seasonal and zonal mean radiation receipts resulting from variations in orbital precession and obliquity. Here we show that the tropical Pacific, a key mediator of global climate, underwent a profound climatic shift during the Holocene. Hydrogen isotope ratios of the algal lipid dinosterol, isolated from marine lake sediments in Palau, increased by 50‰ between 7.7 and 4.5 ka BP, indicating a reduction in precipitation. This implied drying coincided with increased rainfall to the southwest of Palau in Borneo, weakened northern hemisphere monsoons, strengthened southern hemisphere monsoons, and an equatorward shift of terrestrial photosynthesis. A southward shift of the Intertropical Convergence Zone, forced by insolation, is the most likely cause of these climatic and biospheric changes.
Bibliographical noteFunding Information:
This material is based upon work supported by the U.S. National Science Foundation under grant OCE-1241247 (J.P.S.). Additional funding was provided by the Australian Research Council under grant ARC DP120103202 (S.H. and G.C.). U.S. National Science Foundation grant OCE-1241255 to Michael Dawson and Michael Beman supported Jessica Blois during fieldwork in Palau. Palau fieldwork was conducted with the generous permission of the Koror State Government (permit #13-233) and the Republic of Palau’s Bureau of Marine Resources (permit # RE-13-11). This fieldwork would not have been possible without the Coral Reef Research Foundation, especially Pat and Lori Colin, Emilio Basilius, Matt Mesubed, Leebert Baieie, and Gerda Ucharm. We would like to thank Dan Nelson, Nemiah Ladd, and Michael Dawson for assistance in the field, and Josh Gregersen, Becci Danford, Tess Clinkingbeard, and Ashley Maloney for assistance in the lab. We thank Sang Chen for providing the code to produce Figure 4a. Insightful comments from Alyssa Atwood improved this manuscript. The data reported in this study can be found in Tables 1 and 2 and in the published studies and online resources cited. We are grateful to Associate Editor James Russell and two anonymous reviewers for their comments and insights that improved this manuscript.
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- hydrogen isotopes
- lipid biomarkers
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