ISOTOPIC SIGNATURES OF RAIN AND SNOW IN THE JUNEAU ICEFIELD SNOWPACK

Climatic shifts in southeast Alaska are likely to result in changing weather patterns across the Juneau Icefield. Glaciers in this region will be threatened by an increase in temperature and frequency of rain events during the accumulation season, undergoing changes that vary based on their elevation and distance from the coast. Rain and snow events affect the glacier snowpack differently, but the possible influence of a changing rain-to-snow ratio has not been investigated on the Juneau Icefield. However, recent mass balance deficits have drawn attention to the importance of changing weather conditions in southeast Alaska. In this study, we will use stable water isotopes (δ18O and δD) to trace the deposition and modification of precipitation during its lifetime in the annual snowpack on the Juneau Icefield. Ice lenses in snow pits dug for mass balance estimates have already been constrained as either resulting from rain events or melt-refreeze cycles, but isotopic analysis of water from these layers provides the high-precision method necessary to determine the relative contribution of each formation process.

In addition to comprehension of physical processes occurring within the snowpack in response to different precipitation events, the data collected during this trans-icefield study will contribute to the understanding of trends in isotopic fractionation of precipitation across geographical gradients.