A drier Orinoco basin during the twenty-first century: the role of the Orinoco low-level jet

Abstract

AbstractThis study focuses on the analysis of the simulation of the main climatological features of the Orinoco low-level jet (OLLJ) by a set of models included in the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6) and their projected changes under three Shared Socioeconomic Pathways (SSPs): SSP2-4.5, SSP3-7.0, and SSP5-8.5. We consider the 1979–2014 period to evaluate the historical simulations using the ERA5 reanalysis as the reference dataset. In general, CMIP6 models are able to capture the activation of the OLLJ during December-January–February (DJF) in the Orinoco basin, as well as the main links between this circulation and low-level moisture transport patterns in northern South America. Regarding the analysis of projections, CMIP6 models suggest a weakening and shrinking of the OLLJ, especially in its exit region, by the end of the twenty-first century, which in turn induces changes in atmospheric moisture transport patterns in the region during DJF. The projected changes of the OLLJ are associated with variations in the regional gradients of mean sea level pressure, near-surface air temperature, and surface sensible heat flux in association with drier conditions in the Orinoco basin. These projections are consistent with previous studies suggesting a drier Orinoco river basin throughout the twenty-first century. Assessing the projected changes of this low-level jet in northern South America improves our understanding of the different phenomena that modulate atmospheric moisture transport in the region, which is particularly important given its high vulnerability to climate change.