Analyzing Surface Energy Balance and Hydrologic Changes in the Dry Andes Using CORDEX Data

This investigation uses CORDEX model reanalysis data to evaluate the energy balance and hydrologic cycle of a small region of the Dry Andes centered at 70°W and 31°S, bordering Argentina and Chile. This area has become of interest for the potential that glaciers and rock glaciers might provide a significant water resource for the adjacent lowland areas. Surface energy flux variables from CORDEX for the period 1980 to 2010 show a significant energy imbalance that can only be explained with a larger-than-expected average ground heat flux (17 W m² to 22 W m², depending on assumptions about snowmelt). Some of this may be attributed to long-term changes in soil frozen water content. Analysis of energy balance and climatic variables over the 31-year period reveals a significant increase in temperature, with corresponding significant changes in shortwave and longwave radiation fluxes. This has led to significant decreases in snowcover, snowmelt, and runoff (which is almost entirely derived from snowmelt in this region) over a longer summer period that extends from roughly October through March. Soil frozen water content in the autumn has also decreased. All of these changes seem to be driven by summer temperature and its related radiation fluxes, as precipitation has not shown any significant trends.