Clumped isotope evidence for Early Jurassic extreme polar warmth and high climate sensitivity

• Published in: Climate of the Past
• Main Authors: Letulle, Thomas, Suan, Guillaume, Daëron, Mathieu, Rogov, Mikhail, Lécuyer, Christophe, Vinçon-Laugier, Arnauld, Reynard, Bruno, Montagnac, Gilles, Lutikov, Oleg, Schlögl, Jan
• Other Authors: Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Paléocéanographie (PALEOCEAN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Geological Institute of the Russian Academy of Sciences, Russian Academy of Sciences Moscow (RAS), Comenius University in Bratislava, ANR-18-CE31-0020,Oxymore,Rapports isotopiques de l'oxygène des océans mésozoïques revisités(2018)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; Arctic
• Online Access: https://hal.science/hal-03607369; https://hal.science/hal-03607369/document; https://hal.science/hal-03607369/file/cp-18-435-2022.pdf; https://doi.org/10.5194/cp-18-435-2022

International audience Periods of high atmospheric CO 2 levels during the Cretaceous-early Paleogene (∼ 140 to 34 Myr ago) were marked by very high polar temperatures and reduced latitudinal gradients relative to the Holocene. These features represent a challenge for most climate models, implying either higher-than-predicted climate sensitivity to atmospheric CO 2 or systematic biases or misinterpretations in proxy data. Here, we present a reconstruction of marine temperatures at polar (> 80 •) and middle (∼ 40 •) paleolatitudes during the Early Jurassic (∼ 180 Myr ago) based on the clumped isotope (47) and oxygen isotope (δ 18 O c) analyses of shallow buried pristine mollusc shells. Reconstructed calcification temperatures range from ∼ 8 to ∼ 18 • C in the Toarcian Arctic and from ∼ 24 to ∼ 28 • C in Pliensbachian midpaleolatitudes. These polar temperatures were ∼ 10-20 • C higher than present along with reduced latitudinal gradients. Reconstructed seawater oxygen isotope values (δ 18 O w) of −1.5 ‰ to 0.5 ‰ VSMOW and of −5 ‰ to −2.5 ‰ VS-MOW at middle and polar paleolatitudes, respectively, point to a significant freshwater contribution in Arctic regions. These data highlight the risk of assuming the same δ 18 O sw value for δ 18 O-derived temperature from different oceanic regions. These findings provide critical new constraints for model simulations of Jurassic temperatures and δ 18 O sw values and suggest that high climate sensitivity has been a hallmark of greenhouse climates for at least 180 Myr.