The School of Earth and Atmospheric Sciences Presents Dr. Lizz Ultee, Middlebury College

A Global Analysis of Glacial Drought Buffering Through the 21st century

Global climate model projections suggest that 21st century climate change will bring significant drying in the terrestrial midlatitudes. Runoff from glaciers is known to smooth water availability in glaciated basins, but glacier model projections indicate that glacial runoff will generally diminish through the 21st century.  So, to what extent can we expect retreating glaciers to protect downstream areas from drought as the climate continues to change?  Without dynamic glacier ice in global climate models (GCMs), a comprehensive picture of future drought conditions in glaciated regions has been elusive.  

In this talk, I will demonstrate how we have combined CMIP5 climate model output with runoff output from a global glacier model (GloGEM) to produce a modified Standardized Precipitation-Evapotranspiration Index (SPEI) and evaluate glacial buffering of droughts.
We find that accounting for glacial runoff tends to increase multi-GCM ensemble mean SPEI (wetter baseline) and reduce drought frequency and severity, even in basins with glacier cover of less than 2% by area.  We also find that the strength and future trend of glacial drought buffering depends on basin aridity index and glacial cover, and does not depend on other characteristics such as total basin area or latitude.  Glacial drought buffering persists even as glacial runoff is projected to decline through the 21st century.