SEDIMENT TRAP ANALYSIS IN HIGH-ARCTIC LAKE LINNÉVATNET INDICATES A RECENT SHIFT IN THE ANNUAL HYDROLOGICAL REGIME

The recent warming trend, which has been amplified in Arctic regions, has caused a wide range of environmental impacts in the terrestrial and marine environments in the Svalbard archipelago. North Atlantic water, related air masses, and corresponding storms now commonly extend northward to Svalbard, creating anomalously warm temperatures in the late fall and winter season. The annual hydrological regime in the region has shifted accordingly, from a spring snowmelt-driven mode to one dominated by late “shoulder season” and occasional winter rain events. This regime shift has been demonstrated by monitoring of environmental processes and sedimentation in high-Arctic proglacial lake Linnévatnet since 2003, using sediment trap analysis, meteorological data, and time-lapse imagery. Detailed analyses of grain size and geochemistry of sediment traps provide a reconstruction of distinctive annual and seasonal sedimentation signatures. The major accumulation of sediment in Linnévatnet in 6 of the last 7 years has occurred in late summer and fall, when the active layer is at its greatest thickness and sediment is easily mobilized. Compositional profiles, determined by Itrax xrf and x-ray diffraction analyses, also indicate shifts in sediment provenance during the late season. Increase in particle size and increases in Ca from a carbonate bedrock source indicate that the usually dormant eastern valley-side alluvial fans were activated during the intense late season rainstorms.

Sediment yield in the 2016-2017 hydrological year was the highest on record, dominated by two major late season rainstorm events, in August and October. During the October storm, flooding and sediment transport from the main inlet river was accompanied by a major debris flow from the east valley wall which distributed sediment throughout the lake basin. Like other environmental processes in the high-Arctic Svalbard archipelago, the recent shift in hydrological regime and lacustrine sedimentation in Linnévatnet may indicate a trend towards a “new normal”.