Downscaling CESM2 in CLM5 to Hindcast Preindustrial Equilibrium Line Altitudes for Tropical Mountain Glaciers

Tropical mountain glaciers are an important water resource and highly impacted by recent climate change. Tropical mountain glaciation also occurred in the recent and deep past, which presents opportunities for better validating paleoclimate simulations in continental interiors and mountainous regions but requires bridging global model scales (hundreds of kilometers) with the approximate to 1-10 km scale of glaciers when paleotopography is poorly known. Here, we hindcast tropical mountain glaciation in preindustrial time by using global climate model meteorology to force standalone simulations in its land component that use high-resolution topography to resolve selected tropical mountain glaciers. These simulations underestimate observed equilibrium line altitudes (ELAs) by 249 +/- 330 m, but the simulated ELA and snow lines capture observed intermountain ELA variability. Errors in large-scale model precipitation and ELA reconstruction uncertainty are the main contributors to this bias.

Automated summary

The study uses global climate models to simulate the historical situation of tropical mountain glaciers. It finds that the simulations underestimate the equilibrium line altitudes, with errors in large-scale model precipitation and ELA reconstruction uncertainty being the main contributors to this bias.