Stable water-isotope ratios in the snow and firn, Juneau Icefield, Alaska (2024, 2025)

As warming atmospheric temperatures and more melting occur on the polar ice sheets and alpine glaciers, there is a growing need to understand the limitations of melt-affected ice-core interpretations, including temperature reconstructions from water-isotope ratios, within the cryospheric community. Here, we measured water-isotope ratios from snow and firn samples on the Juneau Icefield, Alaska during summer of 2024 and 2025, with field support from the Juneau Icefield Research Program (JIRP). Our results show spatial, interannual, and inter-seasonal variability. Additionally, we find evidence of meltwater alteration of the water-isotope ratios, including homogenization, as well as fractionation associated with ice lenses.
The dataset includes depth, stable oxygen isotope ratios (d18O), stable hydrogen ratios (dD), deuterium excess (d-excess), and associated measurement accuracy at five sites on the Juneau Icefield. The sites include: a site at the Matthes-Llewellyn Divide (MLD); at the intersection of the Matthes and Gilkey Glaciers (MG3); at the Northwest Branch of the Taku Glacier (NWB1); at a firn-covered site in the current ablation zone of the Taku Glacier (TKG4); and at a site near the divide on the Tulsequah Glacier (TSQG). The d18O and dD measurements were obtained from a Picarro Autosampler and Vaporizer, which is an automated high-precision d18O and dD analyzer of liquid-water samples. The document “Juneau_Icefield_core_and_pit_isotopes_2024_2025.csv” contain these data for all sites.