USING STABLE ISOTOPES AS NATURAL TRACERS TO DELINEATE HYDROLOGICAL DRAINAGE BASINS ON THE GREENLAND ICE-SHEET MARGIN

Stable isotope studies of surface ice and water samples collected in t he ablation zone of the Greenland ice-sheet margin at Paakitsup Akulia rusersua approximately 40 km northeast of Ilulissat/Jakobshavn, West G reenland, show that there is a large systematic spatial variation of t he O-18/O-16 ratio (deltaO-18) over the ablation area. DeltaO-18 can, therefore, be used as a natural tracer to locate the origin of the mel t-water runoff. A simple model is set up for simulating the deltaO-18 variation in the melt-water discharge from the area. Simulations are m ade with a drainage basin obtained by modelling the subglacial drainag e conditions, which requires costly and time-consuming mapping of the subglacial topography. The simulated delta-values agree well with obse rved delta-values of water samples from three pro-glacial lakes which receive the melt-water discharge. This suggests that the stable isotop e method can be used to give an initial estimate of melt-water drainag e-basin boundaries on the Greenland ice-sheet margin.