A MULTI-PROXY APPROACH TO ISOLATE THE SEDIMENTARY SIGNAL OF GLACIER LAKE OUTBURST FLOODS IN A MARINE SEDIMENT CORE FROM SIMAFJORDEN IN WESTERN NORWAY – PRELIMINARY RESULTS

Glacier Lake Outburst Floods (GLOF), or Jökulhlaup, represent a major geohazard, and especially under presently witnessed, and further predicted warming climatic conditions, the need to improve our understanding of the processes governing the catastrophic drainage of ice-dammed lakes is prominent. Moreover, the timing of discrete GLOF events can provide insights both to past climates and glacier dynamics.

The main objective of this project is to reconstruct Holocene glacier- and climate fluctuations of the SW valley-outlet glaciers of the Hardangerjøkul ice cap in SW Norway. Here we present a multi-proxy approach to isolate the signal of GLOFs in the fjord’s catchment area. Geomorphological maps have been investigated to identify past and current processes contributing to the sedimentary archive in the fjord. A ~5.5m long core has been obtained from the Simafjord, using a raft-mounted piston corer. Analytical techniques include AMS dating, X-ray fluorescence (XRF), magnetic susceptibility (MS), computed tomography (CT), Loss-on-ignition (LOI) and computer assisted image classification techniques. These techniques yield high-resolution data on sediment properties such as chemical composition, density and minerogenic content. This will facilitate the construction of a history of discrete GLOF events throughout the Holocene from Demmevatnet, a lake dammed by an outlet of the Hardangerjøkul ice cap. In order to separate the signal of catastrophic drainage events from other processes, we identify the parameters that best reflect the historically recorded GLOFs from Demmevatnet. Combined with the AMS dates, a high-resolution chronology of GLOF events can be established, providing key data on climate and glacier dynamics through the Holocene.