Claudia Mihalcea

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

Abstract During 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.

Meteorology and surface energy fluxes in the 2005–2007 ablation seasons at the Miage debris-covered glacier, Mont Blanc Massif, Italian Alps

monitored at 25 points with debris thickness of 0.04–0.55 m, spread over 5 km 2 of the glacier. The radiative fluxes were directly measured, and near‐closure of the surface energy balance is achieved, providing support for the bulk aerodynamic calculation of the turbulent fluxes. Surface‐layer meteorology and energy fluxes are dominated by the pattern of incoming solar radiation which heats the debris, driving strong convection. Mean measured subdebris ice melt rates are 6–33 mm d �1 , and mean debris thermal conductivity is 0.96 W m �1 K �1 , displaying a weak positive relationship with debris thickness. Mean seasonal values of the net shortwave, net longwave, and debris heat fluxes show little variation between years, despite contrasting meteorological conditions, while the turbulent latent (evaporative) heat flux was more than twice as large in the wet summer of 2007 compared with 2005. The increase in energy output from the debris surface in response to increasing surface temperature means that subdebris ice melt rates are fairly insensitive to atmospheric temperature variations in contrast to debris‐free glaciers. Improved knowledge of spatial patterns of debris thickness distribution and 2 m air temperature, and the controls on evaporation of rainwater from the surface, are needed for distributed physically based melt modeling of debris‐covered glaciers.

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

Abstract A 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.

Bacterial community structure on two alpine debris-covered glaciers and biogeography of Polaromonas phylotypes.

High-elevation cold environments are considered ideal places to test hypotheses about mechanisms of bacterial colonization and succession, and about bacterial biogeography. Debris-covered glaciers (glaciers whose ablation area is mainly covered by a continuous layer of rock debris fallen from the surrounding mountains) have never been investigated in this respect so far. We used the Illumina technology to analyse the V5 and V6 hypervariable regions of the bacterial 16S rRNA gene amplified from 38 samples collected in July and September 2009 at different distances from the terminus on two debris-covered glaciers (Miage and Belvedere—Italian Alps). Heterotrophic taxa-dominated communities and bacterial community structure changed according to ice ablation rate, organic carbon content of the debris and distance from the glacier terminus. Bacterial communities therefore change during downwards debris transport, and organic carbon of these recently exposed substrates is probably provided more by allochthonous deposition of organic matter than by primary production by autotrophic organisms. We also investigated whether phylotypes of the genus Polaromonas, which is ubiquitous in cold environments, do present a biogeographical distribution by analysing the sequences retrieved in this study together with others available in the literature. We found that the genetic distance among phylotypes increased with geographic distance; however, more focused analyses using discrete distance classes revealed that both sequences collected at sites <100 km and at sites 9400–13 500 km to each other were more similar than those collected at other distance classes. Evidences of biogeographic distribution of Polaromonas phylotypes were therefore contrasting.

Alpine debris-covered glaciers as a habitat for plant life:

Debris-covered glaciers represent a significant, increasing fraction of glaciers and can host plant life on their surface. The goal of this work was to evaluate the suitability of supraglacial debris as a habitat for plant life and to discuss its ecological and biogeographic role. The research was carried out on the Miage Glacier (Mont Blanc massif, Western Alps, Italy). Vegetation cover was sampled using a regular sampling grid, recording plant species and number of individuals in 71 plots. Detailed glaciological parameters (surface temperature, debris thickness, glacier surface velocity) were recorded or derived from published data. Relationships between vegetation and environmental variables were assessed through Generalized Linear Models, Principal Components Analysis and Canonical Correspondence Analysis. The glacier surface hosted a high biodiversity, with 40 vascular plant species, including trees and shrubs. Plant cover was arranged along an altitude/glacier velocity gradient, whilst debris thickness as low as 10 cm could sustain plant growth on moving ice. Glacier velocity was the main physical factor affecting vegetation cover, probably through its influence on debris stability. The observed species assemblage is comparable with those of subalpine glacier forelands, but with the addition of high-altitude species. Debris-covered glaciers can provide a relatively favourable habitat for plant life wherever the glacier surface is sufficiently stable, acting as a refugium of high-altitude taxa below their altitudinal limits. Glaciers may behave as a dispersal vector for alpine plant species, which could have been important both during glacial periods and during warm stages of the Holocene.

Energy and Mass Balance of Forni Glacier (Stelvio National Park, Italian Alps) from a Four-Year Meteorological Data Record

Abstract Since 26 September 2005 an Automatic Weather Station (AWS1 Forni) has been running on the ablation area of the largest Italian valley glacier, Forni, in the Ortles–Cevedale Group. A 4-year record (from 1 October 2005 to 30 September 2009) of air temperature, relative humidity, wind speed and direction, incoming and outgoing radiative fluxes, air pressure, liquid precipitation, and snow depth is considered. The meteorological data are analyzed to describe glacier surface conditions, to calculate the energy balance, and to evaluate the ice ablation amount. Snow accumulation was measured, thus permitting the estimation of the glacier point mass balance. An annual average amount of melt of −5.4 ± 0.021 m w.e. was calculated and an annual average amount of accumulation of +0.7 ± 0.006 m w.e. was measured at the AWS site. The annual average amount of mass balance was −4.7 ± 0.023 m w.e. Our analyses show that surface conditions during summer and fall seasons are important in regulating glacier albedo and then mass balance. In particular, snow cover presence, due to a longer persistence of spring snow, summer snowfalls and earlier fall solid precipitation, drives the duration of the ice melt period.

Analysis of Glacial Meltwater in Bagrot Valley, Karakoram Based on Short-term Ablation and Debris Cover Observations on Hinarche Glacier

Abstract People in the Karakoram use discharge from glaciers during summer for irrigation and other purposes. While the glacial meltwater supply during hot and dry periods will vary as a result of climate change, Karakoram glaciers so far have not shown a consistent reaction to climatic change, although climate scenarios indicate severe future impacts in the high-elevation regions of the Himalaya and Karakoram. Field measurements on Hinarche Glacier in Bagrot Valley are combined with remote sensing information and climate observations to investigate the meltwater production of the glacier and estimate the meltwater discharge in the valley. Special emphasis was placed on ice melt beneath supraglacial debris, which is the common process on the glacier tongues in the region. The calculated annual meltwater production of about 135 million m3 for Hinarche Glacier shows the order of magnitude for glacier runoff in such environments. Glacial meltwater production is about 300 million m3 per year for the entire valley under balanced conditions. This analysis serves as a basis for further investigations concerning temporal meltwater variability and potential water usage by the local population.

26 Ongoing variations of Himalayan and Karakoram glaciers as witnesses of global changes: recent studies on selected glaciers

Abstract The glaciers located on the highest Asian mountain ranges (Pamir, Karakoram and Himalaya) represent the largest alpine glaciations in the world, outside the polar regions. Runoff from these glaciers feeds rivers (e.g. Indus, Ganges, etc.) that provide much-needed water supply for several hundred million people. In the Himalayan and Karakoram regions debris-covered glaciers (DCG) are the most common glacier type, which seems currently to be spreading in the worlds mountain regions due to the feedback between ice thinning and rock-wall downwasting. To contribute to a better understanding of the complex relations between DCG and climate and to forecast on a decadal scale the glacier response to climate change and its impact on the runoff of high mountain regions, different studies have been carried out on some selected glaciers located in the Karakoram (Baltoro and Liligo in the K2 region) and in the Nepal Himalayas (Changri Nup in the Everest region). To quantify the recent and ongoing fluctuations of the ice masses, historical sources, e.g. maps and photographs, and satellite images have been processed and analysed. In addition, direct field measurements on selected glaciers were performed in order to validate the remotely sensed data and to investigate the variability and magnitude of surface ablation on the DCG tongues.