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Tropical Sea Surface Temperatures Following the Middle Miocene Climate Transition From Laser‐Ablation ICP‐MS Analysis of Glassy Foraminifera
Author(s) -
Nairn Michael G.,
Lear Caroline H.,
Sosdian Sindia M.,
Bailey Trevor R.,
BeavingtonPenney Simon
Publication year - 2021
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2020pa004165
Subject(s) - foraminifera , alkenone , geology , sea surface temperature , cenozoic , paleoclimatology , paleoceanography , proxy (statistics) , oceanography , paleontology , authigenic , neogene , climatology , climate change , sediment , structural basin , machine learning , computer science , benthic zone
The mid‐to‐late Miocene is proposed as a key interval in the transition of the Earth's climate state toward that of the modern‐day. However, it remains a poorly understood interval in the evolution of Cenozoic climate, and the sparse proxy‐based climate reconstructions are associated with large uncertainties. In particular, tropical sea surface temperature (SST) estimates largely rely on the unsaturated alkenone U k 37 proxy, which fails to record temperatures higher than 29˚C, the TEX 86 proxy which has challenges around its calibration, and Mg/Ca ratios of poorly preserved foraminifera. We reconstruct robust, absolute, SSTs between 13.5 Ma and 9.5 Ma from the South West Indian Ocean (paleolatitude ∼5.5˚S) using laser‐ablation inductively coupled‐plasma mass spectrometer microanalysis of glassy planktic foraminiferal Mg/Ca. Employing this microanalytical technique, and stringent screening criteria, permits the reconstruction of paleotemperatures using foraminifera which although glassy, are contaminated by authigenic coatings. Our absolute estimates of 24–31°C suggest that SST in the tropical Indian Ocean was relatively constant between 13.5 and 9.5 Ma, similar to those reconstructed from the tropics using the U k 37 alkenone proxy. This finding suggests an interval of enhanced polar amplification between 10 and 7.5 Ma, immediately prior to the global late Miocene Cooling.