Drier tropical and subtropical Southern Hemisphere in the mid-Pliocene Warm Period

Gabriel Pontes (1, 2) , Ilana Wainer (1) , Andréa Taschetto (2) , Alex Sen Gupta (2) , Ayako Abe-Ouchi (3) , Esther Brady (4) , Wing-Le Chan (3) , Deepak Chandan (5) , Camille Contoux (6, 7) , Ran Feng (4) , Stephen Hunter , Yoichi Kame , Gerrit Lohmann (8) , Bette Otto-Bliesner (4) , W. Richard Peltier (9) , Christian Stepanek , Julia Tindall (10) , Ning Tan (6) , Qiong Zhang (11) , Zhongshi Zhang (12)

1 USP - Universidade de São Paulo = University of São Paulo
2 CCRC - Climate Change Research Centre [Sydney]
3 CCSR - Center for Climate System Research [Kashiwa]
4 NCAR - National Center for Atmospheric Research [Boulder]
5 University of Toronto
6 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
7 CLIM - Modélisation du climat
8 MARUM - Center for Marine Environmental Sciences [Bremen]
9 Department of Physics [Toronto]
10 SEE - School of Earth and Environment [Leeds]
11 BIT - Beijing Institute of Technology
12 Nansen-Zhu International Research Centre

Thermodynamic arguments imply that global mean rainfall increases in a warmer atmosphere; however, dynamical effects may result in more significant diversity of regional precipitation change. Here we investigate rainfall changes in the mid-Pliocene Warm Period (~ 3 Ma), a time when temperatures were 2-3ºC warmer than the pre-industrial era, using output from the Pliocene Model Intercomparison Projects phases 1 and 2 and sensitivity climate model experiments. In the Mid-Pliocene simulations, the higher rates of warming in the northern hemisphere create an interhemispheric temperature gradient that enhances the southward cross-equatorial energy flux by up to 48%. This intensified energy flux reorganizes the atmospheric circulation leading to a northward shift of the Inter-Tropical Convergence Zone and a weakened and poleward displaced Southern Hemisphere Subtropical Convergences Zones. These changes result in drier-than-normal Southern Hemisphere tropics and subtropics. The evaluation of the mid-Pliocene adds a constraint to possible future warmer scenarios associated with differing rates of warming between hemispheres.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Gabriel Pontes, Ilana Wainer, Andréa Taschetto, Alex Sen Gupta, Ayako Abe-Ouchi, et al.. Drier tropical and subtropical Southern Hemisphere in the mid-Pliocene Warm Period. Scientific Reports, 2020, 10 (1), ⟨10.1038/s41598-020-68884-5⟩. ⟨hal-02915943⟩