Modelling the mid-Pliocene Warm Period climate with the IPSL coupled model and its atmospheric component LMDZ5A

Abstract

Abstract. This paper describes the experimental design and model results of the climate simulations of the mid-Pliocene Warm Period (mPWP, ca. 3.3-3 Ma) using the Institut Pierre Simon Laplace model (IPSLCM5A), in the framework of the Pliocene Model Intercomparison Project (PlioMIP). We use the IPSL atmosphere ocean general circulation model (AOGCM), and its atmospheric component alone (AGCM), to simulate the climate of the mPWP. Boundary conditions such as sea surface temperatures (SSTs), topography, ice-sheet extent and vegetation are derived from the ones imposed by the Pliocene Model Intercomparison Project (PlioMIP), described in Haywood et al. (2010Haywood et al. ( , 2011. We first describe the IPSL model main features, and then give a full description of the boundary conditions used for atmospheric model and coupled model experiments. The climatic outputs of the mPWP simulations are detailed and compared to the corresponding control simulations. The simulated warming relative to the control simulation is 1.94 • C in the atmospheric and 2.07 • C in the coupled model experiments. In both experiments, warming is larger at high latitudes. Mechanisms governing the simulated precipitation patterns are different in the coupled model than in the atmospheric model alone, because of the reduced gradients in imposed SSTs, which impacts the Hadley and Walker circulations. In addition, a sensitivity test to the change of landsea mask in the atmospheric model, representing a sea-level change from present-day to 25 m higher during the midPliocene, is described. We find that surface temperature differences can be large (several degrees Celsius) but are restricted to the areas that were changed from ocean to land or vice versa. In terms of precipitation, impact on polar regions is minor although the change in land-sea mask is significant in these areas.

Pre-industrial and mid-Pliocene simulations with NorESM-L: AGCM simulations

“…The simulated general patterns of mid-Pliocene warming agree with our earlier coupled simulations , and also simulations from other PlioMIP groups (e.g. Chan et al, 2011;Koenig et al, 2012;Yan et al, 2012;Zhang et al, 2012;Kamae and Ueda, 2012;Contoux et al, 2012). The analysis of mid-Pliocene climate anomalies necessitates a reference experiment.…”

“…Near the Equator, the zonal mean annual SAT increases only by 1 • C. At high latitudes of the Southern Hemisphere, the zonal mean annual SAT increases by 11 • C. Largest warming appears near the North Pole, where the zonal mean annual SAT increases by 13 • C. Such changes, with stronger warming at high latitudes, follow the mid-Pliocene SST anomalies reconstructed by the PRISM , and also agree with PlioMIP simulations of other groups (e.g. Chan et al, 2011;Koenig et al, 2012;Yan et al, 2012;Kamae and Ueda, 2012;Contoux et al, 2012).…”

“…We indeed find a difference between our AGCM and AOGCM simulations , and also in the simulations carried out by Chan et al (2011). The simulations carried out by Kamae and Ueda (2012) and Contoux et al (2012) on the other hand do not show such differences. This issue should be noted and further assessed during the upcoming PlioMIP analysis and synthesis phase.…”

Tropical cyclone genesis potential across palaeoclimates

“…7, 8b). The PlioMIP simulations have a weaker Hadley and Walker circulation, which results in a broadening of the ITCZ (Contoux et al, 2012). Kamae et al (2011) show that equatorial-specific humidity increases in the lower troposphere and decreases in the mid-troposphere, arising from a weakened ascent of the Walker circulation in the PlioMIP simulations.…”

Drivers and mechanisms for enhanced summer monsoon precipitation over East Asia during the mid-Pliocene in the IPSL-CM5A

“…The second (Experiment 2) utilizes fully coupled oceanatmosphere climate models [atmosphere-ocean general circulation models (AOGCMs) or coupled general circulation models (CGCMs)] to perform the mid-Pliocene and PI simulations (Haywood et al 2010(Haywood et al , 2011. All the PlioMIP1 participating models show good performance in reproducing the global SAT warming in the mid-Pliocene (Chan et al 2011;Bragg et al 2012;Contoux et al 2012;Kamae and Ueda 2012;Koenig et al 2012;Stepanek and Lohmann 2012;Yan et al 2012a, b;Chandler et al 2013;Rosenbloom et al 2013;Zheng et al 2013), despite the mechanisms underpinning the trend remaining controversial (Haywood and Valdes 2004;Hill et al 2014).…”