Dry calving processes at the ice cliff of Strandline Glacier northern Victoria Land, Antarctica

AbstractThis paper describes seasonal variations on Strandline Glacier, Terra Nova Bay, northern Victoria Land, Antarctica, obtained from measurements during two field campaigns (2000/01 and 2002/03). By applying different methodologies and techniques, it was possible to calculate summer changes in thickness (mean decrease over the whole glacier surface of 0.04 mw.e.) and in volume (decrease of 352 μ3 at the terminus). This serves to identify and quantify the processes responsible for these variations (e.g. melting, evaporation, wind erosion/deposition and calving) and to understand the energy transfers at the glacier–air interface. One particular feature of the glacier is the presence of an ice cliff at the terminus, which causes ablation owing to dry calving. This process brought about a summer retreat rate of 1 mweek–1 in the central part of the front during the study period. Qualitative observations carried out during previous field campaigns and quantitative analysis performed during the last two expeditions have provided an understanding of the mechanism underlying the ablation processes, thus confirming the available literature on this topic

Ice ablation and meteorological conditions on the debris-covered area of Baltoro glacier, Karakoram, Pakistan

AbstractDuring the recent Italian expedition 'K2 2004 – 50 years later' (June–July 2004) on Baltoro glacier, Karakoram, Pakistan, glaciological field experiments were carried out on the debris-covered area of this high-elevation glacier. The aim was to investigate the ice ablation and its relations with debris thermal properties and meteorological conditions. Ablation measurements along the glacier up to about 5000 m and within a dedicated test field were combined with meteorological data from two automatic weather stations located at Urdukas (4022 ma.s.l.) and at K2 Base Camp (5033 m a.s.l.). In addition, temperature measurements of the debris cover at different depth levels along the glacier allowed the calculation of debris surface temperature and of the debris thermal resistance (R). Using the air temperature, the local mean lapse rate (0.0075˚C m−1) and the measured ablation, the degree-day factors (K) at different locations on the glacier were calculated. The ice ablation rates were related to debris thickness and elevation. They are typically on the order of 4 cm d−1 during the observation period. However, it was found that the surface topography (slope, aspect) has an influence on the total ablation similar to that of the debris thickness. Thermal resistance of the debris cover and its distribution over the glacier were estimated. Finally, a best-guess estimate of the total meltwater production was calculated from available climate data

PRELIMINARY MAPPING OF GLACIERS AND GLACIAL LANDFORMS OF MOUNT AĞRI DAĞI (ARARAT), EASTERN ANATOLIA - TURKEY

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Yeast and yeast-like diversity in the southernmost glacier of Europe (Calderone Glacier, Apennines, Italy)

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An ablation model for debris-covered ice: the case study of Venerocolo Glacier (Italian Alps)

We developed a simple model to estimate ice ablation under a debris cover. The ablation process is modelled using energy and mass conservation equations for debris and ice and heat conduction, driven by input of either i) debris surface temperature or ii) radiation fluxes, and solved through a finite difference scheme computing the conductive heat flux within the supra-glacial debris layer. For model calibration, input and validation, we used approximately bi-weekly surveys of ice ablation rate, debris cover temperature, air temperature and solar incoming and upwelling radiation during for Summer 2007. We calibrated the model for debris thermal conductivity using a subset of ablation data and then we validated it using another subset. Comparisons between calculated and measured values showed a good agreement (RMSE = 0.04 m w.e., r = 0.79), thus suggesting a good performance of the model in predicting ice ablation. Thermal conductivity was found to be the most critical parameter in the proposed model, and it was estimated by debris temperature and thickness, with value changing along the investigated ablation season. The proposed model may be used to quantify buried ice ablation given a reasonable assessment of thermal conductivity

Modelling shortwave and longwave downward radiation and air temperature driving ablation at the Forni Glacier (Stelvio National Park, Italy)

We focus here on modelling the meteorological parameters most influencing snow/ice melting over an alpine glacier. Specifically, we consider shortwave and longwave downward radiation, and air temperature. We set up and test a methodology for their accurate distribution at the glacier surface, which can be applied whenever: i) supraglacial meteoro-logical measurements are available or ii) weather data are acquired from a station quite close to the glacier. As a suitable site to test our approach we selected the Forni Glacier, in the Italian Alps, where an Automatic Weather Station (AWS) has been running since autumn 2005 thus giving a robust dataset for developing a field based modeling approach. First, we modelled and distributed the incoming solar radiation by taking into account actual atmospheric conditions, glacier topography and shading. Then, we modelled the incoming longwave radiation considering cloud-cover and air temperature. Third, we investigated a local lapse rate to depict the yearly variability of the vertical air temperature gradient, to assess the actual thermal conditions at different elevations. Finally, we compared the modeled values against data collected on the field. The results display that during the glacier ablation period (i.e.: May-September): i) our approach provides a good depiction of both point incoming solar and infrared radiation fluxes, ii) the spatial distribution of the incoming solar radiation we developed is satisfactory, iii) our tests suggest that the incoming longwave fluxes can be considered constant over the whole glacier ablation area thus neglecting its spatial distribution, and iv) the application of a local lapse rate provides a good distribution of air temperature at the glacier surface

Spatial distribution of debris thickness and melting from remote-sensing and meteorological data, at debris-covered Baltoro glacier, Karakoram, Pakistan

AbstractA distributed surface energy-balance study was performed to determine sub-debris ablation across a large part of Baltoro glacier, a wide debris-covered glacier in the Karakoram range, Pakistan. The study area is ~124km2. The study aimed primarily at analyzing the influence of debris thickness on the melt distribution. The spatial distribution of the physical and thermal characteristics of the debris was calculated from remote-sensing (ASTER image) and field data. Meteorological data from an automatic weather station at Urdukas (4022ma.s.l.), located adjacent to Baltoro glacier on a lateral moraine, were used to calculate the spatial distribution of energy available for melting during the period 1–15 July 2004. The model performance was evaluated by comparisons with field measurements for the same period. The model is reliable in predicting ablation over wide debris-covered areas. It underestimates melt rates over highly crevassed areas and water ponds with a high variability of the debris thickness distribution in the vicinity, and over areas with very low debris thickness (<0.03 m). We also examined the spatial distribution of the energy-balance components (global radiation and surface temperature) over the study area. The results allow us to quantify, for the study period, a meltwater production of 0.058 km3

High-Resolution Monthly Precipitation Fields (1913–2015) over a Complex Mountain Area Centred on the Forni Valley (Central Italian Alps)

Mountain environments are extremely influenced by climate change but are also often affected by the lack of long and high-quality meteorological data, especially in glaciated areas, which limits the ability to investigate the acting processes at local scale. For this reason, we checked a method to reconstruct high-resolution spatial distribution and temporal evolution of precipitation. The study area is centred on the Forni Glacier area (Central Italian Alps), where an automatic weather station is present since 2005. We set up a model based on monthly homogenised precipitation series and we spatialised climatologies and anomalies on a 30-arc-second-resolution DEM, using Local Weighted Linear Regression (LWLR) and Regression Kriging (RK) of precipitation versus elevation, in order to test the most suitable approach for this complex terrain area. The comparison shows that LWLR has a better reconstruction ability for winter while RK slightly prevails during summer. The results of precipitation spatialisation were compared with station observations and with data collected at the weather station on Forni Glacier, which were not used to calibrate the model. A very good agreement between observed and modelled precipitation records was pointed out for most station sites. The agreement is lower, but encouraging, for Forni Glacier station data