Sedimentation in a proglacial lake: Interpreting intra- and inter-annual sedimentation in Linnévatnet, Spitsbergen, Norway
Abstract
As part of the larger National Science Foundation Research Experience for Undergraduates on Svalbard (NSF-REU) project, this study focuses on lake sediment distribution processes and sediment flux during the 2005-2006 melt year. Using an array of vertically and spatially distributed sediment traps, the collected sediments have been related to local meteorological conditions and melt-water inputs.
Five mooring sites were established both proximal and distal to the primary inflow, Linnéelva, containing 2 to 4 funnel-type sediment traps, distributed between 2m below the surface to 1m above the lake bottom. The collection period for this study was August 2005 to August 2006. Additionally, two summer traps were deployed at Mooring C (the most proximal site) during the observational period (July-mid August, 2006), to characterize summer sedimentation in the basin.
Grain size analyses shows a basin-wide three-unit stratigraphy including a fine basal layer interpreted as winter , a coarse spring layer , and an upper unit of intermediate grain sizes interpreted as summer. The three units suggest annual silt/clay couplet (varve) sedimentation, supporting the 137Cs core chronology. This varve stratigraphy was consistent throughout the lake and further supports two previous sedimentation studies in Linnévatnet (McKay, 2005; Motley, 2006). Sediment flux during the study period showed that sediment flux did not increase with depth while the two previous studies showed a consistent increase of sediment flux with depth. This suggests that different depositional processes occurred during these two years.
Inflow, surface and bottom water temperatures were compared to identify times of under, inter and overflow conditions. These results suggest that in addition to precipitation and temperature, changes in sediment distribution processes can directly influence the thickness and texture of varves, further complicating the interpretation of past climate and environmental change. Given these internal lake dynamics and their impact on sedimentation, the results suggest that the location from which lake cores are taken may likewise be important with regard to interpreting the varve record of glacial-fed lakes.
Description
Keywords
Svalbard, varves, paleoclimate, limnology, climate change