No abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. Glaciology, 2, pp. 85-91, 1981 Field experiments to determine the effect of a debris layer on ablation of glacier ice Nakawo, M.; Young, G. J. ABSTRACT Ablation of glacier ice has been observed with artificial debris layers prepared with Ottawa sand (ASTM C-109) ranging from 0.01 to 0.1 m thick. Data on external variables observed during the experiments and determination of physical constants of the debris layers have a1 lowed the testing of a proposed simple model. Theoretical predictions compare favourably with the observations. Discussion is extended to a proposal for a simple method by which ablation under a debris layer could be estimated even if the thermal conductivity or thermal resistance of the material were unknown. Annals of

No abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. Glaciology, 28, 98, pp. 29-34, 1982 Estimate of glacier ablation under a debris layer from surface temperature and meteorological variables Nakawo, M.; Young, G. J. ABSTRACT. A simple model suggests that the ablation under a debris layer could be estimated from meteorological variables if the surface temperature data of the layer are available. This method was tested by analyzing the data obtained from experiments with artificial debris layers. Fairly good agreement was obtained between the estimated and the experimental data. In order to evaluate glacier ablation under a debris layer, Nakawo and Young (1981) proposed a simple model which was successfully employed in analyzing experimental data. With this model, ablation under a debris layer can be estimated from meteorological variables when the thermal resistance of the layer is known. Since it is difficult to determine directly the thermal resistance of a layer of unknown material in the field, it was suggested that the surface temperature of the debris layer may be used for estimating the thermal resistance and consequently the ablation under the layer. This paper presents the results of testing the validity of the proposed method by comparing estimated data with field measurements. The symbols used are defined in Table I. Journal of

An operational net shortwave radiation model, which may be used to map radiation distributions under clear and cloudy skies, is described. Construction is achieved by modifying existing total spectrum approaches to allow a minimum of observational data to be used in its operation. Application to the Peyto Glacier Basin, Alberta, shows that realistic and diagnostically useful results can be produced from information contained in a topographic map, monitoring of the snowline, and routine weather observations. Net shortwave radiation estimates from the model are found to be a fair approximation of energy equivalents of ablation derived from stake measurements. It is concluded that net shortwave radiation should be a principal component of any realistic meltwater discharge model. Althoughthe results of micrometeorological studies cannot readily be extended throughout a basin, because of differences in surface cover, exposure, and slope, they are useful in isolating important contributors to the melt process. Most studies indicate the importance of net radiation and, to a lesser degree, sensible heat transfer as energy contributors, as well as the relatively small influence of other energy balance components [Patterson, 1969]. Consequently, the net shortwave component of net radiation emerges as the prime contributor to surface melt energy and the principal component in a basin model. The construction of a net shortwave radiation component must begin with a global radiation model which is useful in mapping the distribution of shortwave radiation arriving at sloping surfaces throughout the basin. Subsequently, knowledge of the surface reflectance field must be incorporated to estimate the net shortwave radiation absorbed by snow and ice.

ABSTRACT. A si mple model suggests that the a bl ation under a debris la yer could be estimated from meteorological variables if th e surface temperat ure data of the layer are available. This method was tested by a nal yzing the data o btained from experiments with artificial d e bris layers. Fairly good agreement was o bta ined between th e estim ated and the experimenta l data.

Over 80% of the flow of the Upper Indus River is derived from less than 20% of its area: essentially from zones of heav y snowfall and glacierized basins above 3500 m elevation. The tran s-Himalaya n contrib ution comes largel y from an area of so me 20000 km 2 of glacie rized bas ins, mostly along the axis of th e Greater Karakoram range and especially from 20-30 of the largest glacier basins. Ver y few glaciological in ves tigati ons have so far been undertaken in thi s the major glacierized reg io n of Central Asia. Biafo Glacier, one of th e larges t of th e Karakoram glaciers, drain s south-eastwards from the central Karakoram crest. Its basi n covers a total area of 853 km 2 , 628 km 2 of which are permanent snow and ice, with 68% of the glacier area forming the accumulation zo ne. This paper desc ribes investigations of snow accumulation, ablation , glacier movement, and glacier depth und e rtake n in the period 1985-87 , set against a background of investigations carried out over the last 130 yea rs. Biafo Glacier differs from most of the other Kara ko ra m glaciers in being nourished mainl y by direct snowfall rather th a n by ava lanching; this has the advantage of allowing extensive investigation of accumulation over a broad range of altitude.Snow-accumulatio n studies in the Biafo Glacier basi n have indicated that annual accumulation varies from 0.9 to 1.9 m of water equivalent between 4650 a nd 5450 m a .. s.l. This suggests an annual mois ture input above the equilibrium lin e of approximately 0 .6 km 3 . Mo nopulse rad a r measureme nts indicate the prese nce o f ice thickness as great as 1400 m at the equili br ium line, althou gh these results may not be completely reliable . Mean surface velocity during the summer of 0.8 m d -I has been measured near to the equilibrium line. Calculations of annual ice flux through the vertical cross-profile at the equilibri um line indica te a throughput of 0.7 km 3 a-I Estimates from stake ablation measurements also suggest th a t ice loss on Biafo Glacier is about 0 .7 km 3 a-I. The close ag ree ment between these three sets of measurements is reass uring, indicating that the ablation zone of Biafo Glacier, whose area covers 0.09% of the whole Upper Indus basin, produces approximatel y 0.9% of the total run-off. Howeve r. it should be mentioned that this estimate does not include water originating from seaso nal snow melt, e ither above or below the equilibrium line, or from rainfall . Net annual ice losses due to wastage of the glacier since 1910 are probably of the order of 0.4-{) .5 m a-I; this would represent between 12 and 15 % of annual water yie ld from me lting ice.

Over 80% of the flow of the Upper Indus River is derived from less than 20% of its area: essentially from zones of heavy snowfall and glacierized basins above 3500 m elevation. The trans-Himalayan contribution comes largely from an area of some 20 000 km2 of glacierized basins, mostly along the axis of the Greater Karakoram range and especially from 20-30 of the largest glacier basins. Very few glaciological investigations have so far been undertaken in this the major glacierized region of Central Asia. Biafo Glacier, one of the largest of the Karakoram glaciers, drains south-eastwards from the central Karakoram crest. Its basin covers a total area of 853 km2, 628 km2 of which are permanent snow and ice, with 68% of the glacier area forming the accumulation zone. This paper describes investigations of snow accumulation, ablation, glacier movement, and glacier depth undertaken in the period 1985–87, set against a background of investigations carried out over the last 130 years. Biafo Glacier differs from most of the other Karakoram glaciers in being nourished mainly by direct snowfall rather than by avalanching; this has the advantage of allowing extensive investigation of accumulation over a broad range of altitude. Snow-accumulation studies in the Biafo Glacier basin have indicated that annual accumulation varies from 0.9 to 1.9 m of water equivalent between 4650 and 5450 m a.s.l. This suggests an annual moisture input above the equilibrium line of approximately 0.6 km3. Monopulse radar measurements indicate the presence of ice thickness as great as 1400 m at the equilibrium line, although these results may not be completely reliable. Mean surface velocity during the summer of 0.8 m d−1 has been measured near to the equilibrium line. Calculations of annual ice flux through the vertical cross-profile at the equilibrium line indicate a throughput of 0.7 km3 a−1. Estimates from stake ablation measurements also suggest that ice loss on Biafo Glacier is about 0.7 km3 a−1. The close agreement between these three sets of measurements is reassuring, indicating that the ablation zone of Biafo Glacier, whose area covers 0.09% of the whole Upper Indus basin, produces approximately 0.9% of the total run-off. However, it should be mentioned that this estimate does not include water originating from seasonal snow melt, either above or below the equilibrium line, or from rainfall. Net annual ice losses due to wastage of the glacier since 1910 are probably of the order of 0.4-0.5 m a−1; this would represent between 12 and 15% of annual water yield from melting ice.