Lake Tuborg, Ellesmere Island (80^o 58’ N, 75^o 33.4 W) is large (21 km L_max x 3 km W_max), glacially-fed, and glacially dammed by arms of the Agassiz Ice Cap. The lake has two basins separated by a sill. The southwest basin is deep (~150 m Z_max), and contains trapped saltwater at depths greater than ~55 m. The northeast basin is shallower (~75 m Z_max), and contains only freshwater. This poster describes the temporal and spatial changes of sedimentary processes at the largest nival delta in Lake Tuborg, which drains into the meromictic basin. Results are based on CTD casts, sediment traps, a submerged flow meter and gravity cores obtained during the peak nival melt of 2001 (June to early July).

A grid of CTD profiles was obtained in front of the nival tributary, and values of water transmissivity, temperature, conductivity and transmissivity were obtained. The grid had 16 sampling stations (4x4), and adjacent stations were ~105 m apart. CTD data and basin bathymetry are currently being interpolated and visualized in 3d using the open source software OpenDX (http://www.opendx.org). Isosurfaces, data “clouds”, 2d slabs and statistical visualizations (ex. histograms) have been produced. OpenDX permits multiple datasets to be presented in one image, allowing spatial relationships between variables to be determined. In addition, multiple timesteps can be used to view temporal changes.

Initial examination of the CTD casts reveals that interflows and overflows increased in intensity throughout the study period, and were the dominant sedimentary processes. Underflows may have been deflected by the strong chemocline. The most striking feature is a zone of decreased transmissivity between 55 – 65 m, which was present before the initiation of melt. This most likely represents a zone of precipitation of inorganic material from the dissolved load, perhaps created when anoxic waters of the monimolimnion came in contact with oxic waters of the mixolimnion. Analysis of sediment trap, gravity core and current meter data (that are concurrent with CTD casts) is currently underway.