Reconstructing Interannual Variability in Regional Climate from Water Isotope Sampling of the Juneau Icefield, Alaska

Temperate glaciers, like those on the Juneau Icefield (JIF), are highly sensitive to small changes in atmospheric temperatures because they already exist near the melting point of H2O. Glaciers in southeast Alaska are major contributors to sea level rise because of high local precipitation and melt rates. Characterizing changes in temperate glacial systems will help us better understand the effects of globally increasing atmospheric temperatures on the atmosphere circulation processes and local hydrological cycle which drive glacier mass balance.

Water isotope ratios from surface snow samples, snow pits, shallow firn cores, and a deeper ice core provide insight into recent past meteorological patterns. These ∂18O and ∂D data allow us to reconstruct both condensation site and evaporation source temperatures through the Simple Water Isotope Model (SWIM). Back trajectory modeling using the Hybrid Single Particle Lagrangian Transport (HYSPLiT) Model and National Center for Environmental Protection (NCEP) reanalysis data allows us to reconstruct storm circulation pathways and identify moisture source areas. We examine interannual variability in icefield-wide winter-time temperatures, moisture source area conditions, and storm trajectories, constraining variability in the regional hydrologic cycle. Future studies will examine the JIF in greater spatial resolution and explore the effects of meltwater in the accumulation zone on water isotope ratios, caused by an increasing amount of melt and precipitation as rain versus snow.