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Temperature gradients across the Pacific Ocean during the middle Miocene

Fox, LR; Wade, BS; Holbourn, A; Leng, MJ; Bhatia, R; (2021) Temperature gradients across the Pacific Ocean during the middle Miocene. Paleoceanography and Paleoclimatology , 36 (6) , Article e2020PA003924. 10.1029/2020PA003924. Green open access

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Abstract

Sea surface temperatures (SSTs) of the tropical Pacific Ocean exert powerful controls on regional and global climates. Previous studies have suggested that during warm climate phases, the east-west temperature gradient collapsed. To date, there has been no high-resolution reconstruction of sea surface conditions in both the east and west Pacific Ocean during the Miocene Climate Optimum (MCO) and across the middle Miocene climate transition (MMCT); therefore, our understanding of the mean oceanographic state during this major global climatic shift is limited. Here, we present new SST reconstructions for the eastern Pacific Ocean (15.5–13.3 Ma) which show a clear east-west temperature gradient of ∼4°C during the warmest interval of the Neogene, implying that the oceanographic processes that produce the modern gradient were present and active. There is no shift in the east-west gradient across the MMCT indicating that the gradient was not impacted by global cooling and ice growth. We find a 2°C sea surface cooling in the eastern equatorial Pacific, that lags the benthic foraminiferal δ^{18}O positive shift by 150 kyr, indicating that tropical temperature did not decrease synchronously with the expansion of the Antarctic ice sheet. Reconstructed variations in the δ^{18}O composition of seawater, determined by combining our Mg/Ca and δ^{18}O records, reveal a freshening in the eastern Pacific Ocean after 13.8 Ma, suggesting changes in the hydrological cycle and in tropical fronts in response to the new icehouse regime.

Type: Article
Title: Temperature gradients across the Pacific Ocean during the middle Miocene
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2020PA003924
Publisher version: https://doi.org/10.1029/2020PA003924
Language: English
Additional information: © 2021 The Authors. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
Keywords: middle Miocene, equatorial Pacific Ocean, SST's, planktonic foraminifera, Mg/Ca, stable isotopes
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10129766
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