Spatial and Temporal Variations of the Surface Energy Balance and Ablation on the Belcher Glacier, Devon Island, Nunavut, Canada

In the summer of 2008 (June 2nd – September 19 th) detailed measurements of meteorological conditions and glacier surface properties were conducted in the Belcher Glacier catchment (718 km 2), Devon Island Ice Cap, Nunavut, Canada. These measurements were used to force and validate a distributed surface energy balance and sub-surface snow model capable of calculating surface ablation rates and meltwater runoff. This study represents a contribution to the International Polar Year (IPY) Glaciodyn project, whose overall aim is to examine the role of hydrology and ice dynamics in the response of marine-terminating glaciers in the Arctic to climate change. Spatially-averaged total water equivalent (w.e.) ablation was 677 mm w.e., and total predicted runoff during the 2008 summer was 3.9 x 108 m3. Net radiation (87%) was the main source of energy over the study period, followed by the sensible heat flux (13%). Net longwave radiation and the latent heat flux represented an overall energy loss from the surface. Modelled melt season duration lasted from June 17th – August 15th, and the majority of ablation occurred in two main periods, from June 26th – July 18th, and from July 27th to August 14th. Snowfall and lower air temperatures limited ablation between these dates and after August 15th. Ice exposure at elevations below 1000 m occurred by July 1st. Periods of high ablation rates were associated with positive air temperatures and high net shortwave radiation receipts, and with near surface air temperature gradients that were shallow or inverted (i.e. higher air temperatures at higher elevations). Periods of minimum ablation rates occurred when net shortwave radiation receipts were reduced (e.g. following summer snowfall) and when air temperatures were negative. The largest changes in both the net surface energy balance and ablation rates were linked to changes in surface albedo associated with (i) snowpack removal and ice exposure, and (ii) summer snowfall events. Modelled time series of runoff from individual sub-catchments within the Belcher catchment will be used to force a coupled hydrology and ice flow dynamics model of the Belcher Glacier that will be used to investigate the dynamic response of tidewater-terminating glaciers to surface hydrological forcing.