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- Title
Clumped isotope evidence for Early Jurassic extreme polar warmth and high climate sensitivity.
- Authors
Letulle, Thomas; Suan, Guillaume; Daëron, Mathieu; Rogov, Mikhail; Lécuyer, Christophe; Vinçon-Laugier, Arnauld; Reynard, Bruno; Montagnac, Gilles; Lutikov, Oleg; Schlögl, Jan
- Abstract
Periods of high atmospheric CO2 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 CO2 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 (Δ47) and oxygen isotope (δ18Oc) 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 mid-paleolatitudes. These polar temperatures were ∼ 10–20 ∘C higher than present along with reduced latitudinal gradients. Reconstructed seawater oxygen isotope values (δ18Ow) of - 1.5 ‰ to 0.5 ‰ VSMOW and of - 5 ‰ to - 2.5 ‰ VSMOW at middle and polar paleolatitudes, respectively, point to a significant freshwater contribution in Arctic regions. These data highlight the risk of assuming the same δ18Osw value for δ18 O-derived temperature from different oceanic regions. These findings provide critical new constraints for model simulations of Jurassic temperatures and δ18Osw values and suggest that high climate sensitivity has been a hallmark of greenhouse climates for at least 180 Myr.
- Subjects
ARCTIC regions; CLIMATE sensitivity; ATMOSPHERIC carbon dioxide; OXYGEN isotopes; ISOTOPES; CLIMATE in greenhouses; PALEOGENE
- Publication
Climate of the Past, 2022, Vol 18, Issue 3, p435
- ISSN
1814-9324
- Publication type
Article
- DOI
10.5194/cp-18-435-2022