Jurassic greenhouse ice-sheet fluctuations sensitive to atmospheric CO2 dynamics
In: Nature Geoscience. Nature Publishing Group: London. ISSN 1752-0894; e-ISSN 1752-0908, more
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| Authors | | Top |
- Nordt, L.
- Breecker, D.
- White, J.
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| Abstract |
Sea-level proxy records and palaeoclimate models suggest that globally elevated temperatures during the greenhouse climate of the Jurassic were punctuated by poorly understood, transient icehouse events. Here we investigate atmospheric CO2–ice-sheet dynamics as a case study from the Early Jurassic Pliensbachian–Toarcian transition (182.7–180.6 million years ago). Applying the C3 CO2 plant proxy to previously published fossil wood data reveals that CO2 levels during this transition ranged from 250 to 400 ppm. Previously published belemnite δ18O values suggest that sea-level low stands were equivalent to ice volumes up to two-thirds of Antarctica today. Beginning with the Toarcian ocean anoxic event, these ice sheets largely melted when CO2 reached sustained concentrations of ~500–700 ppm. Compared with the Cenozoic East Antarctic Ice Sheet and ice sheets modelled for the Middle Jurassic, Early Jurassic ice sheets exhibit minimal lags (hysteresis) between warming and cooling limbs, suggesting they were thin and located at lower latitudes and elevations with a higher temperature sensitivity to melting. These sensitivities of ice volume to CO2 provide additional constraints on climate models for application to warming transitions in both the past and future. |
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