Firn Density and Stratigraphy Observations collected by the U.S. Geological Survey Glacier Project

This dataset contains observations of snow and firn density and stratigraphy from sites on Wolverine, Gulkana, Kennicott, and Kahiltna Glaciers. These sites span a broad range of climates that support glacier accumulation zones in the Alaska Region. Firn cores were collected regularly starting in 2016. Initially firn cores were only collected at Wolverine Glacier site EC. More recently cores have been collected at additional sites on more glaciers with the goal of understanding how the snow to ice transition varies in different glacier accumulation zone settings. Targeted sites have been selected for low spatial variability of upstream accumulation as assessed with high-frequency radar. Cores are of variable length and include a variable number of years of accumulation, but all of the cores included in this data release contain a minimum of two years of accumulation. Ice lenses were identified by visual inspection. Where it was possible to identify annual layers, they are noted. Annual layer depths were determined by various methods depending on the setting. At lower elevations with well developed melt horizons visible layers of dust/pollen/dirt identify summer minimum surfaces. At higher elevations, with minimally developed melt horizons, summer minimum surfaces are often identified by thick layers of cold dry snow between subsequent summer melt complexes.