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

Glacial outburst floods (jökulhlaups) have occurred across Earth throughout the Quaternary—and during earlier glaciations—and are a significant contemporary hazard in Arctic and alpine regions worldwide (Baker, 2013; Carrivick and Tweed, 2013, 2016; Ghienne et al., 2010; Harrison et al., 2018). These sudden meltwater drainage events are triggered by subglacial volcanic eruptions or dam failure or overtopping at ice-contact lakes (Björnsson, 2002; Evans and Clague, 1994; Tweed and Russell, 1999). Jökulhlaups can modify landscapes far beyond the proglacial source region and leave a legacy that can persist for millennia, eroding bedrock, redistributing sediment, and—in the case of the largest events—influencing ocean circulation and global climate (Baynes et al., 2015b; Carling, 2013; Clarke et al., 2004; Cook et al., 2018; Russell et al., 2005). Since floodwaters recede relatively quickly and are difficult to measure in real-time, geomorphologic and sedimentologic impacts are often the only lines of evidence to reconstruct both past and contemporary floods (Baker, 2008; Carrivick and Rushmer, 2006; Carrivick et al., 2013a; Clague and Evans, 2000). The overall aims of this paper are to assess the interpretive challenges in using geomorphologic data to reconstruct past jökulhlaups, discuss strategies to resolve them, and introduce an enhanced jökulhlaup geomorphologic interpretive framework.