April 13, 2021
Evolution of temperature seasonality from the mid-Eocene to the early Oligocene, a model-data journey
Data and paleoclimate reconstructions allow us to describe better and better late Eocene to early Oligocene climate evolution, and the greenhouse-icehouse transition. However, we have learned mainly about the oceanic realms and terrestrial climate evolution remains poorly resolved. Some studies, mainly on paleobotanical remains, describe a stronger winter cooling through this period. This phenomena would have increased the Mean Annual Range of Temperatures (MATR), and thus result in a temperature seasonality strengthening. But, while it is described in large areas of the Northern Hemisphere, the mechanisms associated with seasonality increase have not been studied in depth.
In this study, we use different late Eocene to early Oligocene paleoclimate simulations (Earth System Model, IPSL-CM5A2) to trace the evolution of temperature seasonality patterns at a global scale and identify the respective contribution of three major forcing: pCO2 lowering, Antarctic ice-sheet formation, and the associated sea-level drop.
We show that the different forcing affect the MATR at zonal to regional scales. pCO2 drop produces large areas of MATR increase at high latitudes through sea-ice formation and albedo feedback. The Antarctic ice-sheet decreases seasonality of a large part of the Southern Hemisphere, but the sea level drop it brings creates multiple MATR increase zones by increasing continentality (coastal area expansion and sea retreat). Together these three forcing allow us to reconstruct seasonality change patterns in good agreement with data and the spatial heterogeneity they describe. The spatial distribution of increasing vs decreasing MATR zones appears partly correlated to that of the Eocene-Oligocene Transition biotic crisis, which calls for more in-depth studies of deep-time climate variability.
China University of Geosciences
April 27, 2021 UTC 0900
Florida Museum of Natural History
May 4, 2021
May 11, 2021
Nuria Melisa Morales Garcia
University of Bristol
May 18, 2021
May 25, 2021
National Oceanographic Centre
June 1, 2021
University of Texas Institute for Geophysics
June 8, 2021