Using Stable Isotopes and Fallout Radionuclides to Track Winter Precipitation

Abstract

Under changing conditions of precipitation due to climate change and possible shifts in precipitation sourcing, having a baseline of precipitation sourcing for regions across the U.S. will become increasingly important. This baseline will be especially important for winter precipitation in snowfall regions such as the upper Midwest U.S. because snowpack is a crucial water source for rivers, lakes, aquifers and drinking water systems across the country. Using relative concentrations of oxygen’s three stable isotopes (16O, 17O, and 18O) as tracers of precipitation is a method that can be used to track processes of precipitation formation and evaporation. Fallout radionuclides can also be effective tools in tracking precipitation events. Certain short-lived radionuclides, such as Lead-210 and Beryllium-7, have a variety of uses in studying precipitation and atmospheric processes. We collected and analyzed local snow samples for stable isotopes and radionuclides throughout the winter and utilized this data along with pre-existing data from multiple collaborators at the University of Minnesota. This study assists in creating a baseline for isotopic composition in precipitation for the Twin Cities and Upper Midwest and creates a deeper understanding of the source conditions and spatial distribution of precipitation events. Future studies of precipitation tracking, specifically winter precipitation, are needed to set a baseline for the precipitation source conditions across multiple spatial scales.