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

Abstract

The Mesozoic era (∼252 to 66 million years ago) was a key interval in Earth's evolution toward its modern state, witnessing the breakup of the supercontinent Pangaea and significant biotic innovations like the early evolution of mammals. Plate tectonic dynamics drove a fundamental climatic transition from the early Mesozoic supercontinent toward the Late Cretaceous fragmented continental configuration. Here, key aspects of Mesozoic long‐term environmental changes are assessed in a climate model ensemble framework. We analyze so far the most extended ensemble of equilibrium climate states simulated for evolving Mesozoic boundary conditions covering the period from 255 to 60 Ma in 5 Myr timesteps. Global mean temperatures are generally found to be elevated above the present and exhibit a baseline warming trend driven by rising sea levels and increasing solar luminosity. Warm (Triassic and mid‐Cretaceous) and cool (Jurassic and end‐Cretaceous) anomalies result from pCO2 changes indicated by different reconstructions. Seasonal and zonal temperature contrasts as well as continental aridity show an overall decrease from the Late Triassic‐Early Jurassic to the Late Cretaceous. Meridional temperature gradients are reduced at higher global temperatures and less land area in the high latitudes. With systematic sensitivity experiments, the influence of paleogeography, sea level, vegetation patterns, pCO2, solar luminosity, and orbital configuration on these trends is investigated. For example, long‐term seasonality trends are driven by paleogeography, but orbital cycles could have had similar‐scale effects on shorter timescales. Global mean temperatures, continental humidity, and meridional temperature gradients are, however, also strongly affected by pCO2.

Climate Variations in the Past 250 Million Years and Contributing Factors

“…It is noted that this temperature variation is in agreement with the Mesozoic warming trend shown by Landwehrs et al. (2021). The GMSTs in the CO 2 ‐fixed group of simulations are comparable to those in the simulations with 1,120 ppmv CO 2 in Farnsworth, Lunt, O'Brien, et al.…”

“…Second, as pointed out in , the CNDV simulates rather low areal vegetation coverage. Figure S3 in Supporting Information S1 shows that the simulated global mean vegetation fraction is generally no more than 38%, much lower than that prescribed in the simulations by Landwehrs et al (2021) (higher than 70%), which is derived from the climate zonation of Boucot et al (2013). The low vegetation fraction causes cold biases in the simulations .…”

“…However, the precession effect should have small impact here because we just focus on variations of annual mean GMSTs in this study. In previous studies, reconstructed atmospheric CO 2 concentrations are commonly used in paleoclimate simulations (e.g., Landwehrs et al, 2021;Valdes et al, 2021). Here, we take an alternative approach to constrain simulations, using the reconstructed GMSTs by Scotese (2015).…”

Arctic ice and the ecological rise of the dinosaurs

“…S4) (12), demonstrating that dinosaurs were present at these arctic latitudes associated with freezing winter temperatures as background climatic conditions. This is consistent with available climate models that consistently show freezing wintertime temperatures in high-latitude Asia for the Late Triassic and Jurassic (5,6,13,14) and congruous with models for Mesozoic climate until extremely high Pco 2 levels (e.g., 4480 ppm) are reached (15). However, despite these models, warm arctic conditions have been asserted by some on the basis of equivocal proxy data, e.g., an assessment possible in the absence of empirical evidence of arctic freezing, such as these L-IRD.…”

A high-resolution climate simulation dataset for the past 540 million years

“…Landwehrs et al . 11 performed 40 time-slice simulations for the period from 255 million years ago (Ma) to 60 Ma, using the CLIMBER-3α Earth System Model of Intermediate Complexity (EMIC) that has a relatively coarse spatial resolution. The Bristol Research Initiative for the Dynamic Global Environment (BRIDGE) group at University of Bristol has produced large datasets of paleoclimate simulations 12 – 14 .…”