Preprints
https://doi.org/10.5194/egusphere-2024-2002
https://doi.org/10.5194/egusphere-2024-2002
20 Aug 2024
 | 20 Aug 2024

Proglacial lake evolution and outburst flood hazard at Fjallsjökull glacier, southeast Iceland

Greta Hoe Wells, Þorsteinn Sæmundsson, Finnur Pálsson, Guðfinna Aðalgeirsdóttir, Eyjólfur Magnússon, Reginald L. Hermanns, and Snævarr Guðmundsson

Abstract. Glacier retreat is projected to increase with future climate warming, elevating the risk of mass movement-triggered glacial lake outburst floods (GLOFs). These events are an emerging yet understudied hazard in Iceland, including at Fjallsjökull, an outlet glacier of the Vatnajökull ice cap in southeast Iceland. A multibeam sonar scanner survey revealed that the proglacial Fjallsárlón lake significantly expanded from 1945 to 2021. If recent glacier terminus retreat rates continue, Fjallsárlón will reach its maximum extent around 2110, more than doubling in surface area and tripling in volume. The lake will occupy two overdeepened basins with a maximum depth of ~210 m, which will likely increase terminus melting and calving rates—and thus glacier retreat—as well as potentially float the glacier tongue. Three zones on the valley walls above Fjallsjökull have high topographic potential of sourcing rock falls or avalanches that could enter Fjallsárlón and generate displacement waves or GLOFs, significantly impacting visitors and infrastructure at this tourism site. This study provides input data for risk assessments and mitigation strategies at Fjallsjökull; a template for investigating this hazard at other proglacial lakes in Iceland; and field data to advance understanding of overdeepenings and lake–terminus interactions in proglacial lakes worldwide.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Greta Hoe Wells, Þorsteinn Sæmundsson, Finnur Pálsson, Guðfinna Aðalgeirsdóttir, Eyjólfur Magnússon, Reginald L. Hermanns, and Snævarr Guðmundsson

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2002', Anonymous Referee #1, 06 Sep 2024
    • AC1: 'Reply on RC1', Greta Wells, 13 Nov 2024
  • RC2: 'Comment on egusphere-2024-2002', Anonymous Referee #2, 07 Sep 2024
    • AC2: 'Reply on RC2', Greta Wells, 13 Nov 2024
  • RC3: 'Comment on egusphere-2024-2002', Wilfried Haeberli, 07 Sep 2024
    • AC3: 'Reply on RC3', Greta Wells, 13 Nov 2024
Greta Hoe Wells, Þorsteinn Sæmundsson, Finnur Pálsson, Guðfinna Aðalgeirsdóttir, Eyjólfur Magnússon, Reginald L. Hermanns, and Snævarr Guðmundsson
Greta Hoe Wells, Þorsteinn Sæmundsson, Finnur Pálsson, Guðfinna Aðalgeirsdóttir, Eyjólfur Magnússon, Reginald L. Hermanns, and Snævarr Guðmundsson

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Short summary
Glacier retreat elevates the risk of landslides released into proglacial lakes, which can trigger glacial lake outburst floods (GLOFs). This study maps proglacial lake evolution and GLOF hazard scenarios at Fjallsjökull glacier, Iceland. Lake volume increased from 1945–2021 and is estimated to triple over the next century. Three slopes are prone to landslides that may trigger GLOFs. Results will mitigate flood hazard at this popular tourism site and advance GLOF research in Iceland and globally.