Larger lake outbursts despite glacier thinning at ice-dammed Desolation Lake, Alaska

• Published in: The Cryosphere
• Main Authors: N. Lützow, B. Higman, M. Truffer, B. Bookhagen, F. Knuth, O. Korup, K. E. Hughes, M. Geertsema, J. J. Clague, G. Veh
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2025
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Dammed Lake; Fairweather; glacier; glaciers; The Cryosphere; Alaska
• Online Access: https://doi.org/10.5194/tc-19-1085-2025; https://doaj.org/article/89156575b7e54e66b8865a1a3a7e7e62

Many glaciers dam lakes at their margins that can drain suddenly. Due to the downwasting of these glacier dams, the magnitude of glacier lake outburst floods may change. Judging from repeat satellite observations, most ice-dammed lakes with repeated outbursts have decreased in area, volume, and flood size. Yet, we find that some lakes oppose this trend by releasing progressively larger volumes over time, and elevating downstream hazards. One of these exceptions is Desolation Lake, southeastern Alaska, having drained at least 48 times since 1972 with progressively larger volumes despite the surface lowering of the local ice dam. Here we focus on explaining its unusual record of lake outbursts using estimates of flood volumes, lake levels, and glacier elevation based on a time series of elevation models and satellite images spanning 5 decades. We find that the lake grew by ∼10 km 2 during our study period, which is more than any other ice-dammed lake with reported outbursts in Alaska. The associated flood volumes tripled from 200×10 6 – 300×10 6 m 3 in the 1980s to up to ∼ 700 × 10 6 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="11ee79b0dd23bf3c21a29c8743baab8a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-19-1085-2025-ie00001.svg" width="58pt" height="14pt" src="tc-19-1085-2025-ie00001.png"/></svg:svg> m 3 in the 2010s, which is more than 5 times the regional median of reported flood volumes from ice-dammed lakes. Yet, Lituya Glacier, which dams the lake, had a median surface lowering of ∼50 m between 1977 and 2019, and the annual maximum lake levels dropped by 110 m since 1985 to a level of 202 m above sea level in 2022. We explain the contrasting trend of growing lake volume and glacier surface lowering in terms of the topographic and glacial setting of Desolation Lake. The lake lies in a narrow valley in contact with another valley glacier, Fairweather Glacier, at its far end. During our study ...