Abstract:
The Galápagos Archipelago, located on the equator in the eastern Pacific, exhibits pronounced seasonal and interannual climate variability influenced primarily by the Inter-Tropical Convergence Zone and the El Niño-Southern Oscillation (ENSO). Despite its ecological significance and vulnerability to climatic changes, limited observational data has hindered long-term analyses of climate trends in the region. This study leverages the newly developed Galápagos Archipelago Refined Analysis dataset, with a 2 km × 2 km grid spacing, derived from high-resolution dynamical downscaling of ERA5 data, to comprehensively examine climatic trends across the archipelago from 1980 to 2023 using both linear regression and Mann-Kendall trend analysis. Our key finding is a positive trend in layer thickness of lower and upper troposphere driven by rising potential air temperature. While linear regression detects significant trends primarily during dry seasons, the Mann-Kendall test reveals additional monotonic warming trends during wet and transitional seasons obscured by strong interannual variability, indicating more pervasive year-round tropospheric warming than linear analysis alone suggests. This tropospheric warming signal suggests increasing atmospheric stability over the archipelago. In contrast, near-surface variables are dominated by strong interannual variability driven primarily by ENSO, and linear regression does not detect statistically significant long-term trends in air temperature, humidity, or precipitation. However, the Mann-Kendall test identifies a significant monotonic warming trend in near-surface air temperature during January–February–March, indicating a subtle wet-season surface signal that is weaker and less spatially consistent than the tropospheric warming. Notably, strong El Niño events before 2000 exhibited substantially stronger precipitation and temperature anomalies than more recent events, suggesting potential changes in ENSO characteristics affecting the region. The observed decoupling between tropospheric warming trends and boundary-layer conditions underscores the need for further investigation into vertical atmospheric dynamics and the mechanisms linking large-scale climate change to local surface conditions on the archipelago.
