Abstract
Abstract. During past geological times, the Earth experienced several intervals of global warmth, but their driving factors remain equivocal. A careful appraisal of the main processes controlling past warm events is essential to inform future climates and ultimately provide decision makers with a clear understanding of the processes at play in a warmer world. In this context, intervals of greenhouse climates, such as the thermal maximum of the Cenomanian–Turonian (∼94 Ma) during the Cretaceous Period, are of particular interest. Here we use the IPSL-CM5A2 (IPSL: Institut Pierre et Simon Laplace) Earth system model to unravel the forcing parameters of the Cenomanian–Turonian greenhouse climate. We perform six simulations with an incremental change in five major boundary conditions in order to isolate their respective role on climate change between the Cenomanian–Turonian and the preindustrial. Starting with a preindustrial simulation, we implement the following changes in boundary conditions: (1) the absence of polar ice sheets, (2) the increase in atmospheric pCO2 to 1120 ppm, (3) the change in vegetation and soil parameters, (4) the 1 % decrease in the Cenomanian–Turonian value of the solar constant and (5) the Cenomanian–Turonian palaeogeography. Between the preindustrial simulation and the Cretaceous simulation, the model simulates a global warming of more than 11 ∘C. Most of this warming is driven by the increase in atmospheric pCO2 to 1120 ppm. Palaeogeographic changes represent the second major contributor to global warming, whereas the reduction in the solar constant counteracts most of geographically driven warming. We further demonstrate that the implementation of Cenomanian–Turonian boundary conditions flattens meridional temperature gradients compared to the preindustrial simulation. Interestingly, we show that palaeogeography is the major driver of the flattening in the low latitudes to midlatitudes, whereas pCO2 rise and polar ice sheet retreat dominate the high-latitude response.
Highlights
The Cretaceous Period is of particular interest in order to understand drivers of past greenhouse climates because intervals of prolonged global warmth (O’Brien et al, 2017; Huber et al, 2018) and elevated atmospheric CO2 levels (Wang et al, 2014), possibly similar to future levels, have been documented in the proxy record
The simulated changes between the preindustrial and the CT (4X-CRETACEOUS) simulations can be decomposed into five components based on our boundary condition changes: (1) polar ice sheet removal, (2) pCO2 ( CO2), (3) PFT and soil parameters ( PFT-SOIL), (4) solar constant and (5) palaeogeography
Each contribution to the total climate change can be calculated by a linear factorization (Broccoli and Manabe, 1987; Von Deimling et al, 2006), which corresponds to the anomaly between two consecutive simulations
Summary
The Cretaceous Period is of particular interest in order to understand drivers of past greenhouse climates because intervals of prolonged global warmth (O’Brien et al, 2017; Huber et al, 2018) and elevated atmospheric CO2 levels (Wang et al, 2014), possibly similar to future levels, have been documented in the proxy record. The thermal maximum of the Cenomanian–Turonian (CT) interval (94 Ma) represents the acme of Cretaceous warmth, during which one of the most important carbon cycle perturbations of the Phanerozoic occurred, the oceanic anoxic event 2 (OAE2; Jenkyns, 2010; Huber et al, 2018). Valuable understanding of what controls large-scale climate processes can be drawn from investigations of the mechanisms responsible for the CT thermal maximum and carbon cycle perturbation. M. Laugié et al.: Modelling Cenomanian–Turonian climate and temperature gradient
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
