SEASONAL DYNAMICS OF A HIGH ARCTIC LAKE, LAKE LINNÉ, SPITSBERGEN ISLAND, SVALBARD

The purpose of this project is to characterize the physical processes in Lake Linné, Spitsbergen Island, Svalbard, that lead to vertical and lateral water temperature differences during the high arctic summer. The observed seasonal dynamics may include overturning, water temperature stratification, and variable timing of maximum water temperature in the lake. These seasonal changes must be quantified before water temperature data from this lake can be used in studies of global warming effects in high arctic lakes.

We used atmospheric and lake temperature data for the period of July 31 through September 4, 2003. We compared atmospheric temperature, wind speed and direction, solar radiation influx, and barometric pressure to lake temperature data from shallow (i.e., 2m) and deep (i.e., 10 m) mooring sites near the center of the lake (i.e., Site G) and on the southern shelf (i.e., Site F). We found that July 31 through August 19 surface water temperatures increased from 4°C to a three day long plateau of 7°C, and then fell to 5.8°C at the end of the observational period. This trend corresponds to concomitant air temperature changes. The increase lags shortly behind warm southerly weather while the cooling trend follows weak northerly winds. Anomalies in water temperature trends correspond to an unsettled time of wind azimuth as the prevailing winds shift from south to north. Changes in water temperature at ten meters mimic surface water temperature changes. Thermal stratification at Site F is lost during periods of strong southerly wind. These winds also correspond to days when surface water temperature at Site F is colder than at Site G.

Our observations indicate that air temperature is the dominant control on water temperature at sites F and G through ten meters of water depth. However, strong southerly winds can cause vertical and horizontal changes in water temperature through vertical mixing of intermediate and shallow water, and lateral displacement of surface water. Thus, our single-season data indicate that lake water temperatures are proxies of atmospheric temperature although strong winds perturb the system.