Global River Discharge and Floods in the Warmer Climate of the Last Interglacial

Paolo Scussolini (1) , Dirk Eilander (1) , Edwin H. Sutanudjaja (2) , Hiroaki Ikeuchi (3) , Jannis M. Hoch (2) , Philip J. Ward (1) , Pepijn Bakker (1) , Bette L. Otto-Bliesner (4) , Chuncheng Guo (5) , Christian Stepanek (6) , Qiong Zhang (7) , Pascale Braconnot (8, 9) , Maria-Vittoria Guarino (10) , Sanne Muis (1) , Dai Yamazaki (3) , Ted I. E. Veldkamp (1) , Jeroen C.J.H. Aerts (1)

1 VU - Vrije Universiteit Amsterdam [Amsterdam]
2 Universiteit Utrecht / Utrecht University [Utrecht]
3 UTokyo - The University of Tokyo
4 NCAR - National Center for Atmospheric Research [Boulder]
5 BCCR - Bjerknes Centre for Climate Research
6 Alfred Wegener Institute [Potsdam]
7 Stockholm University
8 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
9 MERMAID - Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics
10 BAS - British Antarctic Survey

We investigate hydrology during a past climate slightly warmer than the present: the last interglacial (LIG). With daily output of preindustrial and LIG simulations from eight new climate models we force hydrological model PCR-GLOBWB and in turn hydrodynamic model CaMa-Flood. Compared to preindustrial, annual mean LIG runoff, discharge, and 100-yr flood volume are considerably larger in the Northern Hemisphere, by 14%, 25%, and 82%, respectively. Anomalies are negative in the Southern Hemisphere. In some boreal regions, LIG runoff and discharge are lower despite higher precipitation, due to the higher temperatures and evaporation. LIG discharge is much higher for the Niger, Congo, Nile, Ganges, Irrawaddy, and Pearl and lower for the Mississippi, Saint Lawrence, Amazon, Paraná, Orange, Zambesi, Danube, and Ob. Discharge is seasonally postponed in tropical rivers affected by monsoon changes. Results agree with published proxies on the sign of discharge anomaly in 15 of 23 sites where comparison is possible. Plain Language Summary It is still uncertain how the water cycle will respond to a warmer climate in the coming decades. To increase our understanding of the relationships between climate and hydrology, we study the past climate of the last interglacial, which was slightly warmer than the present. We present the results of a modeling approach, showing that while Northern Hemisphere precipitation was higher during the last interglacial, discharge of rivers was even higher, and floods were even larger. On the contrary, in the Southern Hemisphere precipitation, discharge and floods were lower. We show that, for some regions, precipitation, discharge, and floods do not have the same direction of change. The seasonal timing of discharge also changes for some large basins of the Northern Hemisphere. Finally, for 23 sites, we compare our results to geological evidence. These results form a useful term of comparison to both projections of the future and geological studies of past hydrology.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Paolo Scussolini, Dirk Eilander, Edwin H. Sutanudjaja, Hiroaki Ikeuchi, Jannis M. Hoch, et al.. Global River Discharge and Floods in the Warmer Climate of the Last Interglacial. Geophysical Research Letters, 2020, 47 (18), ⟨10.1029/2020GL089375⟩. ⟨hal-02942231⟩