SUSPENDED SEDIMENT TRANSPORT IN HIGH ARCTIC LAKE LINNÉ, SVALBARD, NORWAY

The Svalbard Archipelago, 76ºN - 81ºN latitude, offers a pristine environment to study the modern affects of global climate change in High Arctic environments. Distal, proglacial Lake Linné, one of the largest lakes in Svalbard (4.7 km long, 35 m deep), contains a rich record of rhythmic laminae dating from the late Pleistocene. This lacustrine stratigraphy aids in interpreting depositional histories within the Linné valley. Sedimentary processes were studied in July and August of 2006 to understand the links between climatic controls and suspended sediment entering the lake. Depth, temperature, and transmissivity (turbidity) were recorded in water column profiles by a Seacat SBE 19 profiler over a three-week period. A local automated meteorological station recorded air temperature, wind direction and velocity, precipitation, and solar radiation. In addition, an automated camera recorded images of the lake inlet to document changes in the inflow stream and the occurrence of surface sediment plumes. Vertical water column profiles reveal that overflow density currents dominate only at the lake inlet, terminating abruptly to underflow density currents distal to the Linné inlet. Delta turbidity flows resulting from delta front failures were also detected. Previous studies have named overflow, interflow, and underflow currents as processes attributed solely to grain size and water temperature. In this study, we find that meteorological conditions including (but not limited to) wind speed, wind direction and precipitation, significantly influence the movement of lake density currents more than simply grain size and water temperature. Data from vertical water column profiles suggest that in some cases, stratified density currents may be independent of water temperature. For instance, polar northeasterly winds suppressed overflow sediment plumes and enhanced turbid underflows, while also increasing the chances of homopycnal flows. Southwesterly winds of the Gulf Stream elongated surface sediment plumes.

As a second objective, the thermal regime of Lake Linné was studied. Twenty high-resolution temperature loggers were positioned at various depths throughout the lake. Water temperatures reached 7ºC, surpassing previously speculated temperatures for this High Arctic meltwater lake.