Immediate jokulhlaup (glacier outburst flood) impacts in a recently decoupled proglacial meltwater system, Skeidararjokull, SE Iceland.

In response to climate change many temperate glaciers worldwide, including Skeidararjokull in SE Iceland, are retreating. Associated with this retreat is the appearance and expansion of proglacial lakes. These proglacial lakes lead to the outwash plains (sandar) being disconnected or decoupled from the glacier. Consequently, the sediment that would otherwise be deposited on the sandar is instead trapped within these lakes, leading to sediment deprivation of the distal sandar which in-turn impacts the fluvial and coastal systems. The recent formation of proglacial lakes also provides new challenges jokulhlaup hazard assessment. Despite their importance, there have been no detailed studies of large-scale proglacial sedimentary systems undergoing active decoupling, and the role of this process for sediment flux and landscape development remains unclear. In December 2021 Grimsvotn subglacial lake drain 0.9 km3 of water as a jokulhlaup from Skeidararjokull. This provides a rare opportunity to capture the geomorphological and sedimentary signature of a jokulhlaup within a subaqueous setting and assess the role that proglacial lakes have in altering the response of the downstream fluvial and coastal system.

The overall aim of the project is to improve understanding of the impact of jokulhlaups on landform and sedimentary assemblages within proglacial lakes and assess the impact of these lakes on the glacifluvial and coastal system of Skeidararsandur. SE Iceland. The collection and analysis of data from the 2021 December jokulhlaup will enable accurate prediction and modeling of the impacts of larger future events that will assist our project partners, the Icelandic Meteorological Office, to provide better early warning of floods.