A regional climate modeling investigation of wetland-related coupled hydrologic–atmospheric processes in central South America

Abstract This study investigates how the Pantanal, one of the world’s largest tropical floodplains, modulates local and regional climate in central South America through coupled land–atmosphere processes. Using the RegIPSL regional climate modeling framework, two simulations covering the 1998–2019 period were conducted: one including an explicit floodplain scheme and one without it. The floodplain-enabled simulation exhibits a substantially improved representation of the hydrological cycle over the Pantanal and Upper Paraguay River Basin, particularly through enhanced evapotranspiration, increased moisture recycling, and more realistic river discharge. Results show that activating the floodplain scheme increases precipitation across most of the Pantanal and surrounding regions, primarily by raising the number of rainy days during the wet season. However, convection is suppressed over the most heavily flooded areas, consistent with wetland-breeze dynamics and stabilized boundary-layer conditions. At regional scales, enhanced evapotranspiration transforms the Pantanal into an atmospheric moisture source, increasing lower-tropospheric humidity, moist static energy, and convective potential downstream. The altered surface fluxes weaken the Chaco Low and modify the South American Low-Level Jet, reducing large scale atmospheric moisture transport over the Pantanal but strengthening it along the eastern Andes, ultimately increasing precipitation in parts of northern Argentina. These findings highlight the crucial role of tropical floodplains in shaping regional climate and underscore the importance of representing wetland processes in global and regional Earth system models. Because the model is too dry over the Pantanal during the wet season, the absolute magnitude of these responses should be interpreted with caution, while the simulated mechanisms and their spatial structure provide robust evidence for a floodplain-atmosphere feedback.