Changes in the Caribbean Low-Level Jet in the recent climate period and CMIP6 climate change scenarios

Abstract

The Caribbean Low-Level Jet (CLLJ) is a crucial atmospheric feature controlling climate variability and moisture transport in the Caribbean region. This study analyzes historical trends and future projections of the CLLJ using observational data, reanalysis products, and Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models. Historical analysis (1981-2020) reveals CLLJ weakening, supported by three of the four reanalysis products showing wind-speed decreases of –0.02 to –0.05 m s^–1 y^–1 at 925 hPa, consistent with observed pressure-gradient reductions between the North Atlantic Subtropical High (NASH) and Panama Low. Natural multidecadal variability, including the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO), likely contributed to this weakening. CMIP6 models demonstrate limited skill in reproducing historical CLLJ characteristics, with only 18% capturing observed weakening trends and 82% failing to achieve RMSE* < 1, indicating skill inferior to climatology. Future projections (2015-2099) show clear scenario dependence: the low emission scenario (SSP1-2.6) maintains current conditions while high emission scenarios (SSP3-7.0 and SSP5-8.5) drive progressive strengthening through enhanced pressure gradients. Seasonal changes redistribute CLLJ intensity, weakening winter maxima while strengthening autumn minima, potentially eliminating the current bimodal structure under high emissions. These findings have profound implications for regional water resources and renewable energy, requiring adaptive management strategies that account for projection uncertainties.