Hydrometeorology of a high Arctic glacier

Field studies of John Evans Glacier (JEG), Ellesmere Island, (79° 40' N, 74° 30' W) were used to investigate Arctic glacier melt, runoff and mass balance (MB) response to climate change. Seasonal development of glacier drainage is driven by a hydrofracture process: meltwater-filled crevasses propagate from the glacier surface to the bed, forcing a connection between the supra- and subglacial drainage systems. Given the importance of surface meltwater in this process, the melt response of a high wind/high air temperature event (28-30 July, 2000) was examined. Results show that this event produced 30% of total seasonal melt, strongly contributing to negative MB conditions in 2000. The timing and frequency of such events therefore critically impacts both seasonal drainage development and interannual variability in Arctic glacier MB.; Field measurements at JEG highlight problems inherent in current MB models. Models assume constant negative summer air temperature lapse rates (STLR) and positive winter accumulation lapse rates (WALR) over glacier surfaces. Results show that STLR and WALR are highly spatially and temporally variable: STLR is often positive, and WALR is negative due to snow redistribution/sublimation from wind scour events. Models also do not incorporate summer snowfall events, which significantly reduce melt; and summer wind events that, while rare, substantially reduce MB. Results are significant for the high Arctic where annual MB is relatively small, and minor changes in annual ablation/accumulation can significantly impact MB.; Model parameterization sensitivity was determined using parameter values selected from field observations. Degree-day model (DDM) output is most sensitive to values of STLR and summer ALR, and the variable degree-day factor. These input parameters must therefore be verified by field measurements to increase confidence in model predictions.; Perturbation of the DDM with global circulation model predictions of future (2000-2029) air temperature/precipitation show that increased air temperatures will have the greatest impact on net annual MB at JEG, and are hardly mitigated by a concurrent predicted winter precipitation increase. This results in enhanced melt/runoff production and superimposed ice formation, likely causing more extensive seasonal development of the glacier drainage system, and potentially impacting the dynamic response of JEG to climate change.