Groundwater Feedbacks on Climate Change in the CNRM Global Climate Model

• Published in: Journal of climate Vol. 36; no. 21; pp. 7599 - 7617
• Main Authors: Colin, Jeanne, Decharme, Bertrand, Cattiaux, Julien, Saint-Martin, David
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.11.2023
• Subjects: Aquifers; Atmosphere; Atmospheric models; Climate change; Climate feedback; Climate models; Climate system; Climatology; Earth Sciences; Environmental impact; Evapotranspiration; General circulation models; Global climate; Global climate models; Groundwater; Groundwater flow; Groundwater recharge; Groundwater resources; Heat waves; Hydrology; Precipitation; Regions; Sciences of the Universe; Simulation; Unconfined aquifers; Vegetation; Water resources; United States > US
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-22-0767.1

Groundwater and climate interact in a two-way manner. Precipitation ultimately controls groundwater recharge and, conversely, groundwater may influence climate through evapotranspiration. Yet very few global climate models or Earth system models actually simulate groundwater flows. And while the expected impacts of climate change on groundwater resources are the subject of a growing concern, global-scale groundwater–climate feedbacks have received very little attention so far. Here we show that the integration of unconfined aquifers in a global climate model can regionally affect the climate change signal on temperatures and precipitation. We assess the impact of groundwater under preindustrial and 4xCO 2 conditions (after climate stabilization). In both cases, we find that groundwater has a cooling and a wetting effect in certain regions of the world. In eastern Europe, both these impacts are stronger in the warmer climate (4xCO 2 forcing) where the presence of groundwater reduces the frequency of summer heatwaves by 40%, compared to a 15% reduction in the preindustrial world. This work constitutes one of the very first global assessments of the potential feedbacks of groundwater on climate change. Our results support the idea that groundwater should be represented in global climate models and Earth system models, as it does indeed play an active role in the climate system.