Chapter 4 - Isotopic Fractionation in Snow Cover

Abstract

Publisher Summary This chapter discusses the modeling of snowmelt contributions to stream flow or groundwater that is complicated by isotopic fraction during snow formation, accumulation, ablation, and phase change during melt. The isotopic content of any snowpack is in large part controlled by variations in the isotopic content of individual precipitation events. However, the formation of snowflakes can involve additional isotopic fractionation. Isotopic fractionation of hydrogen and oxygen isotopes during snow accumulation and melt can create complications for the study of snowmelt contributions to stream flow generation. These complications are not insurmountable and may in fact provide new insights into dynamics of the snow accumulation and melt process. The chapter describes the fundamentals of isotopic fractionations in snow cover during accumulation and snowmelt, and provides an overview of isotopic water balance and evaporation. These complications suggest the need to explore and rethink the use of alternative tracers that can help validate and assure correct interpretations when δD and δ180 are used to study snowmelt processes. Radioactive isotopes always had a special appeal in this respect because the very low activities observed in environmental samples normally require only small or negligible adjustment to account for the same isotopic fractionation effects that can complicate use of stable isotopes.