Journal
PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
Volume 36, Issue 8, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2020PA004115
Keywords
Clumped isotopes; Expedition 363; international ocean discovery program; Pliocene; Site U1488; western pacific warm pool
Funding
- Trond Mohn Foundation
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [638467]
- RCN project [245907]
- U.S. National Science Foundation [OCE-1736686]
- European Research Council (ERC) [638467] Funding Source: European Research Council (ERC)
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The Indo-Pacific Warm Pool (IPWP) plays a crucial role in influencing climate dynamics. Controversy exists regarding the evolution of surface temperatures in the IPWP since the Pliocene, fueled by contradictory proxy evidence. Temperature reconstructions using different proxies show good agreement when applying minor corrections for seawater chemistry changes.
The Indo-Pacific Warm Pool (IPWP) plays a crucial role in influencing climate dynamics both in the tropics and globally. Yet, there is an ongoing controversy concerning the evolution of surface temperatures in the IPWP since the Pliocene, which is fueled by contradictory proxy evidence. Temperature reconstructions using TEX86 indicate a gradual cooling by similar to 2 degrees C from the Pliocene to today while Mg/Ca-based studies using planktonic foraminifera do not report any long-term trends. A bias in Mg/Ca records due to seawater chemistry changes has been suggested as an explanation for this proxy mismatch. Here, we present data from two independent foraminifera-based temperature proxies, Mg/Ca and clumped isotopes (Delta(47)), measured on the same samples from IODP Site U1488 in the IPWP. We reconstructed mixed layer and subsurface temperatures and find very good agreement among Mg/Ca and Delta(47) when applying a minor correction for changing Mg/Ca ratios of seawater. Diagenetic effects could influence Delta(47) but the evaluation of foraminifera preservation at Site U1488 suggests that this effect is unlikely to have masked a long-term trend in the data. While remaining uncertainties prevent us from fully ruling out particular hypotheses, our study adds evidence that mixed layer temperatures likely did not cool substantially, while subsurface temperatures cooled more strongly since the Pliocene. The substantial Pleistocene cooling previously observed in TEX86 data is consistent with this finding when interpreting it as a combined surface and subsurface signal.
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