ABSTRACT. We conducted seismic refraction surveys in the upper ablation area of Storglaciären, a small valley glacier located in Swedish Lapland. We estimated seismic-wave attenuation using the spectralratio method on the energy travelling in the uppermost ice with an average temperature of approximately -1 • • C. Attenuation values were derived between 100 and 300 Hz using the P-wave quality factor, Q P , the inverse of the internal friction. By assuming constant attenuation along the seismic line we obtained mean Q P = 6 ± 1. We also observed that Q P varies from 8 ± 1 to 5 ± 1 from the near-offset to the far-offset region of the line, respectively. Since the wave propagates deeper at far offsets, this variation is interpreted by considering the temperature profile of the study area; far-offset arrivals sampled warmer and thus more-attenuative ice. Our estimates are considerably lower than those reported for field studies in polar ice (∼500-1700 at -28

[1] The Antarctic Peninsula has warmed faster than the global average rate of warming during the last century. Due to limited availability of long term meteorological records, the geographical extent of this rapid warming is poorly defined. We collected borehole temperature measurements in the upper 300 m of Rutford Ice Stream, West Antarctica, and employed an inverse modeling scheme with a heat diffusion-advection equation to determine the recent surface temperature history of the borehole position. Our results reveal recent warming of 0.17 ± 0.07°C (decade) À1 since 1930. This result suggests that, at least in an attenuated form, the rapid warming observed over the Antarctic Peninsula extends as far south as Rutford Ice Stream. This result agrees with other recent results that show a warming trend across much of the West Antarctic Ice Sheet.

The accuracy of velocity determination from common mid-point (CMP) ground penetrating radar surveys has been assessed in the past and found to be sufficient for migration and depth determination. Increasingly, these velocities are also being used to quantify subsurface physical properties such as water content. This paper demonstrates that small errors in measured velocity can result in large errors in these derived properties. We have evaluated the size of some error sources with specific reference to a given glaciological model and common glaciological survey conditions. At worst, large static errors and 3% errors in measured offset result in interval velocity errors of [Formula: see text]. This error is large enough that derived water content has an error greater than 80% (e.g., [Formula: see text] volumetric % water). Common acquisition and processing practices result in [Formula: see text] interval velocity errors (corresponding to [Formula: see text] error in water content, e.g., [Formula: see text] volumetric %); best practices could result in errors as low as [Formula: see text] in interval velocity (corresponding to [Formula: see text] error in water content, e.g., [Formula: see text] volumetric %), but to achieve this level of precision requires a revision of common practice for CMP acquisition and processing. This revision would need to result in improved assignment of time zero and a consistent definition of reflection event arrival time (to provide travel time errors smaller than 0.5%), and accurate measurement of CMP geometry.

[1] We have investigated the distribution and character of radar scatterers in the glacier Bakaninbreen, Svalbard, using ground-penetrating radar (GPR). The GPR profiles showed scattering regions with an undulating upper boundary in both along-and across-glacier orientations. The simplest interpretation of such scattering regions would be a layer of randomly distributed scatterers with an undulating upper boundary, underlying a layer without scatterers. We propose an alternative model of scatterer distribution, in which the scatterers are confined to obliquely dipping planes. This model is shown to be able to reproduce the shape of the scattering regions observed in the field data and is consistent with previous observations of dipping thrust features in Bakaninbreen from radar data and in outcrop. Multifrequency profiles (50, 100, and 200 MHz) contained scatterers with similar measured power, indicating that the scatterers have decimeter-scale dimensions. Multipolarized antenna configurations were used to detect a preferred polarization direction for scattered radiation, which was approximately across glacier, suggesting that the scatterers are nonspherical and aligned across glacier. The scatterers are thought to be large water bodies confined to dipping planar features and elongated in the strike orientation of the planes.Citation: Barrett, B. E., T. Murray, R. Clark, and K. Matsuoka (2008), Distribution and character of water in a surge-type glacier revealed by multifrequency and multipolarization ground-penetrating radar,