On the Sensitivity of the Devonian Climate to Continental Configuration, Vegetation Cover, Orbital Configuration, CO ₂ Concentration, and Insolation

Abstract

During the Devonian (419 to 359 million years ago), life on Earth witnessed decisive evolutionary breakthroughs, most prominently the colonization of land by vascular plants and vertebrates. However, it was also a period of major marine extinctions coinciding with marked changes in climate. The cause of these changes remains unknown, and it is therefore instructive to explore systematically how the Devonian climate responds to changes in boundary conditions. Here we use coupled climate model simulations to investigate separately the influence of changes in continental configuration, vegetation cover, carbon dioxide (CO2) concentrations, the solar constant, and orbital parameters on the Devonian climate. The biogeophysical effect of changes in vegetation cover is small, and the cooling due to continental drift is offset by the increasing solar constant. Variations of orbital parameters affect the Devonian climate, with the warmest climate states at high obliquity and high eccentricity. The prevailing mode of decadal to centennial climate variability relates to temperature fluctuations in high northern latitudes which are mediated by coupled oscillations involving sea ice cover, ocean convection, and a regional overturning circulation. The temperature evolution during the Devonian is dominated by the strong decrease in atmospheric CO2. Albedo changes due to increasing vegetation cover cannot explain the temperature rise found in Late Devonian proxy data. Finally, simulated temperatures are significantly lower than estimates based on oxygen isotope ratios, suggesting a lower δ18O ratio of Devonian seawater.

Investigating Mesozoic Climate Trends and Sensitivities With a Large Ensemble of Climate Model Simulations

“…Furthermore, simulated temperatures are generally too high over present‐day Antarctica, in particular during Southern winter, and too low over the Northern Atlantic during Northern winter. The model has been successfully used in a number of paleoclimate studies (Brugger et al., 2017, 2019; Feulner, 2017; Landwehrs et al., 2020), and compares well with other models in model intercomparison projects (Eby et al., 2013; Zickfeld et al., 2013).…”

Minimum levels of atmospheric oxygen from fossil tree roots imply new plant−oxygen feedback

“…Table S1-S4; Bartholomeus et al, 2008;Bjerrum, 2021). The soil types, used in the soil-root model, are determined based on palaeosol descriptions and the classification scheme from the U.S. Department of Agriculture (Supplementary Information; Brady, 1990;Driese et al, 1997;Mintz et al, 2010;Wösten, 1997;Wösten et al, 2001 S5; Brugger et al, 2019;Montoya et al, 2005).…”

“…The soil types, used in the soil–root model, are determined based on palaeosol descriptions and the classification scheme from the U.S. Department of Agriculture (Supplementary Information; Brady, 1990; Driese et al., 1997; Mintz et al., 2010; Wösten, 1997; Wösten et al., 2001). The temperature of surface air and soil as well as soil moisture content is obtained from published results of a coarse resolution Devonian climate model‐setup building on the intermediate complexity coupled Earth System model CLIMBER‐3α (Table S5; Brugger et al., 2019; Montoya et al., 2005). Paleogeographical locations are based on the PALEOMAP (Figure S4; Scotese, 2016).…”

Paleotemperature record of the Middle Devonian Kačák Episode

“…A recently published Devonian climate simulation suggests a global annual mean surface air temperature of 21 °C and tropical SST of 28 °C for the Middle Devonian 44 . The model 44 suggests colder low latitude mean SSTs compared to SSTs calculated from δ 18 O apatite of Devonian conodonts.…”

“…A recently published Devonian climate simulation suggests a global annual mean surface air temperature of 21 °C and tropical SST of 28 °C for the Middle Devonian 44 . The model 44 suggests colder low latitude mean SSTs compared to SSTs calculated from δ 18 O apatite of Devonian conodonts. Combining the new δ 18 O apatite data from the Prague Synform (28° S) and the Carnic Alps (34° S) with other published data (Supplementary Fig.…”