Reconstructing glacial outburst floods (jökulhlaups) from geomorphology: Challenges, solutions, and an enhanced interpretive framework

Abstract

Glacial outburst floods (jökulhlaups) have been significant drivers of landscape change across Earth throughout the Quaternary and are a contemporary hazard in Arctic and alpine regions worldwide. Geomorphologic evidence is a foundation for reconstructing past and contemporary flood events and using additional analytical methods such as geochronology and paleohydraulics. Yet, accurate interpretation of jökulhlaup landforms and depositional sequences poses a persistent challenge due to complex controls on flood hydraulics and landscape evolution. Researchers have developed numerous strategies to reduce or resolve these challenges, but a comprehensive, globally applicable model to interpret flood evidence outside of sedimentary environments is lacking. This article synthesizes existing case studies to describe jökulhlaup geomorphologic interpretive challenges, discuss strategies to resolve them, and present a conceptual model of flood landform assemblages to illustrate hydraulic and environmental controls on resultant geomorphologic impacts. This enhanced interpretive framework aids researchers in identifying, interpreting, and testing geomorphologic evidence to reconstruct past jökulhlaups and predict future flood impacts as robustly as possible at a global, landscape-wide scale. Understanding jökulhlaup geomorphology yields insight into glacial lake

Geophysical reconstruction of the late Holocene proximal proglacial landsystem at Skeiðarársandur, southeast Iceland

“…8) is attributed to jökulhlaup activity. The presence of jökulhlaup‐related outwash deposits is evidenced by the chaotic nature of radar reflections, in combination with the presence of ice‐block meltout structures, a common diagnostic feature of jökulhlaup activity in the sedimentary and geomorphic record (Russell and Knudsen, 1999; Marren, 2005; Marren and Schuh, 2009; Wells et al ., 2022). However, it remains possible that the chaotic unit of reflections above PR1 are a product of deformation linked to glacial advance (e.g.…”

Timing and maximum flood level of the Early Holocene glacial lake Nedre Glomsjø outburst flood, Norway

“…Wells et al . 2022). In addition to this, the maximum flood level may very well not leave behind evident geomorphological traces, e.g.…”

“…2005; Herget 2005; Benito & Thorndycraft 2020; Wells et al . 2022). How well the mapped PSIs reflect the actual maximum outburst flood levels, however, is a pivotal issue, especially when reconstructing palaeoflood magnitude (Alho et al .…”

“…Finding palaeostage indicators (PSIs) reflecting the maximum outburst flood level is often more challenging, however, as morphological traces from the maximum flood level may be subtle and have a relatively low preservation potential (e.g. Wells et al 2022). In addition to this, the maximum flood level may very well not leave behind evident geomorphological traces, e.g.…”

“…Features commonly used for interpreting maximum outburst flood levels include scarps and trimlines eroded into pre-existing deposits, slackwater and run-up sediments, flood-scoured spillways and a general impression of wash limits (Baker & Nummedal 1978;Baker et al 1979;O'Connor & Baker 1992;O'Connor 1993;Carrivick et al 2004;Alho et al 2005;Herget 2005;Benito & Thorndycraft 2020;Wells et al 2022). How well the mapped PSIs reflect the actual maximum outburst flood levels, however, is a pivotal issue, especially when reconstructing palaeoflood magnitude (Alho et al 2005(Alho et al , 2010Carrivick et al 2013;Larsen & Lamb 2016).…”