Seasonal surface melt onset and firn freeze-up across the central Wrangell and St. Elias Mountains
- 1University of Maine (Orono, United States of America)
Abstract
High-elevation alpine firn is increasingly influenced by surface melt and meltwater retention, yet the spatial extent and timing of these processes remain poorly quantified. Here, we use surface melt onset and firn freeze-up dates derived from Sentinel-1 C-band Synthetic Aperture Radar data from 2015–2024 to map dry firn and hydrologic transition zones, where firn is at a transition between dry and wet regimes, across the central Wrangell/St. Elias Mountains. Melt onset and freeze-up are identified from characteristic changes in backscatter associated with the presence of liquid water in snow and firn. Seasonal melt is detected across nearly all elevations in the range (0–5,670 m a.s.l.). Melt onset broadly tracks the seasonal rise of the 0 °C isotherm up to ∼ 3000 m a.s.l., while freeze-up shows pronounced delays relative to subfreezing air temperatures at mid-elevations (2000–3000 m a.s.l.), indicating widespread meltwater retention within the firn. We find that dry firn covers only 3 % of our study domain's glacierized area, while hydrologic transition zones cover 9 % of our study domain's glacierized area. Our results highlight the pervasive influence of meltwater retention on firn hydrologic regimes in the Wrangell/St. Elias Mountains and demonstrate the utility of Sentinel-1 SAR for mapping firn water retention and monitoring changes in regional firn hydrology in data-sparse mountain regions.
Versions
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BibTeX
@article{kindstedt2026seasonal,
title = {{Seasonal surface melt onset and firn freeze-up across the central Wrangell and St. Elias Mountains}},
author = {Ingalise Kindstedt and Andrew Johnson and Kristin M. Schild and Luke Copland and Christine Dow and Alison Criscitiello and Dominic Winski and Karl Kreutz and Seth Campbell},
journal = {The Cryosphere},
year = {2026},
month = oct,
doi = {10.5194/tc-20-5941-2026},
url = {https://tc.copernicus.org/articles/20/5941/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Seasonal surface melt onset and firn freeze-up across the central Wrangell and St. Elias Mountains
AU - Ingalise Kindstedt
AU - Andrew Johnson
AU - Kristin M. Schild
AU - Luke Copland
AU - Christine Dow
AU - Alison Criscitiello
AU - Dominic Winski
AU - Karl Kreutz
AU - Seth Campbell
PY - 2026
DA - 2026/10/15
JO - The Cryosphere
DO - 10.5194/tc-20-5941-2026
UR - https://tc.copernicus.org/articles/20/5941/2026/
AB - High-elevation alpine firn is increasingly influenced by surface melt and meltwater retention, yet the spatial extent and timing of these processes remain poorly quantified. Here, we use surface melt onset and firn freeze-up dates derived from Sentinel-1 C-band Synthetic Aperture Radar data from 2015–2024 to map dry firn and hydrologic transition zones, where firn is at a transition between dry and wet regimes, across the central Wrangell/St. Elias Mountains. Melt onset and freeze-up are identified from characteristic changes in backscatter associated with the presence of liquid water in snow and firn. Seasonal melt is detected across nearly all elevations in the range (0–5,670 m a.s.l.). Melt onset broadly tracks the seasonal rise of the 0 °C isotherm up to ∼ 3000 m a.s.l., while freeze-up shows pronounced delays relative to subfreezing air temperatures at mid-elevations (2000–3000 m a.s.l.), indicating widespread meltwater retention within the firn. We find that dry firn covers only 3 % of our study domain's glacierized area, while hydrologic transition zones cover 9 % of our study domain's glacierized area. Our results highlight the pervasive influence of meltwater retention on firn hydrologic regimes in the Wrangell/St. Elias Mountains and demonstrate the utility of Sentinel-1 SAR for mapping firn water retention and monitoring changes in regional firn hydrology in data-sparse mountain regions.
SN - 1994-0424
ER -