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In the summer of 2008 (June 2nd September 19th) detailed measurements of meteorological conditions and glacier surface properties were conducted in the Belcher Glacier catchment (718 km2), 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.

The techniques of two-dimensional model seismology were employed to investigate the problem of Rayleigh waves incident upon the boundary between two solid elastic media. The object of the investigation was the determination of the reflection and transmission coefficients. As a preliminary, the special case of a quarter space was examined to test the hypothesis that the reflection coefficient could be successfully approximated by selecting the amplitude of the reflected Rayleigh wave so that the normal and tangential stresses imposed on the free surface are minimized in the least square sense. Analogously for the half space, it was proposed that the reflection and transmission coefficients should be such as to minimize the differences (or residuals) between the respective stresses and displacements on either side of the discontinuity. This is a reasonable assumption since the boundary conditions require continuity in this case. It was found that the agreement between the measured and calculated values of the coefficients was only qualitative and it had to be concluded that the proposed hypotheses were not sufficient to explain the reflection and transmission of Rayleigh waves. For a half space consisting of an aluminium alloy and plexiglass, the reflection and transmission coefficients were measured as a function of the angle with which the plane interface between the two media meets the free surface. The angle was varied in steps of 10° from 0° to 180° and the observed coefficients are presented with no attempt at a theoretical derivation. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

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