Claudio Smiraglia

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.

ACCELERATING CLIMATE CHANGE IMPACTS ON ALPINE GLACIER FOREFIELD ECOSYSTEMS IN THE EUROPEAN ALPS

In the European Alps the increase in air temperature was more than twice the increase in global mean temperature over the last 50 years. The abiotic (glacial) and the biotic components (plants and vegetation) of the mountain environment are showing ample evidence of climate change impacts. In the Alps most small glaciers (80% of total glacial coverage and an important contribution to water resources) could disappear in the next decades. Recently climate change was demonstrated to affect higher levels of ecological systems, with vegetation exhibiting surface area changes, indicating that alpine and nival vegetation may be able to respond in a fast and flexible way in response to 1-2 degrees C warming. We analyzed the glacier evolution (terminus fluctuations, mass balances, surface area variations), local climate, and vegetation succession on the forefield of Sforzellina Glacier (Upper Valtellina, central Italian Alps) over the past three decades. We aimed to quantify the impacts of climate change on coupled biotic and abiotic components of high alpine ecosystems, to verify if an acceleration was occurring on them during the last decade (i.e., 1996-2006) and to assess whether new specific strategies were adopted for plant colonization and development. All the glaciological data indicate that a glacial retreat and shrinkage occurred and was much stronger after 2002 than during the last 35 years. Vegetation started to colonize surfaces deglaciated for only one year, with a rate at least four times greater than that reported in the literature for the establishment of scattered individuals and about two times greater for the well-established discontinuous early-successional community. The colonization strategy changed: the first colonizers are early-successional, scree slopes, and perennial clonal species with high phenotypic plasticity rather than pioneer and snowbed species. This impressive acceleration coincided with only slight local summer warming (approximately -0.5 degree C) and a poorly documented local decrease in the snow cover depth and duration. Are we facing accelerated ecological responses to climatic changes and/or did we go beyond a threshold over which major ecosystem changes may occur in response to even minor climatic variations?

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.

Glaciological characteristics of the ablation zone of Baltoro glacier, Karakoram, Pakistan

Abstract Baltoro glacier in the Karakoram, Pakistan, is one of the world’s largest valley glaciers. It drains an area of about 1500 km2 and is >60km long. In 2004 an Italian/German expedition carried out a glaciological field program on the ablation zone of the glacier, focusing on the ablation conditions and the dynamic state of the glacier. As Baltoro glacier is a debris-covered glacier, ice ablation also depends on the debris properties. Stake measurements of ice ablation and debris cover in combination with meteorological data from automatic weather stations close by have been used to determine the local melt conditions. Results from these calculations have been combined with an analysis of different classes of surface cover and information about precipitation, using remote-sensing techniques, in order to calculate mass fluxes for the upper part of Baltoro glacier. The dynamic state of the glacier has been investigated by GPS-based surface velocity measurements along the stake network. A comparison of these short-term measurements during the melt season with surface velocities computed from feature tracking of satellite images shows a high seasonal variability of the ice motion. We have shown that this variability is up to 100% of the annual mean velocity. On the basis of these investigations, the mass fluxes at the Concordia cross-section have been quantified. This approach can now be used together with the ablation calculations to reconstruct the variability of glacier extent and volume in the past using available climate data from the central Karakoram. From the comparison of historical measurements and photographs it is shown that the snout of Baltoro glacier is oscillating back and forth a couple of hundred metres. Otherwise it seems not to react with the same magnitude as other glaciers to the climatic change. Elevation changes at Concordia are a few tens of metres at the most.

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

The present study reports the characterization of psychrophilic yeast and yeast-like diversity in cold habitats (superficial and deep sediments, ice cores and meltwaters) of the Calderone Glacier (Italy), which is the southernmost glacier in Europe. After incubation at 4 and 20 degrees C, sediments contained about 10(2)-10(3) CFU of yeasts g(-1). The number of viable yeast cells in ice and meltwaters was several orders of magnitude lower. The concomitant presence of viable bacteria and filamentous fungi has also been observed. In all, 257 yeast strains were isolated and identified by 26S rRNA gene D1/D2 and internal transcribed spacers (1 and 2) sequencing as belonging to 28 ascomycetous and basidiomycetous species of 11 genera (Candida, Cystofilobasidium, Cryptococcus, Dioszegia, Erythrobasidium, Guehomyces, Mastigobasidium, Mrakia, Mrakiella, Rhodotorula and Sporobolomyces). Among them, the species Cryptococcus gastricus accounted for almost 40% of the total isolates. In addition, 12 strains were identified as belonging to the yeast-like species Aureobasidium pullulans and Exophiala dermatitidis, whereas 15 strains, presumably belonging to new species, yet to be described, were also isolated. Results herein reported indicate that the Calderone Glacier, although currently considered a vanishing ice body due to the ongoing global-warming phenomenon, still harbors viable psychrophilic yeast populations. Differences of yeast and yeast-like diversity between the glacier under study and other worldwide cold habitats are also discussed.

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.

Glacier shrinkage and modeled uplift of the Alps

[1] Present day glacier reduction in the Alps, estimated from glacier inventories and induced viscoelastic response of a stratified Earth’s model, is responsible for sizable uplift rates. Patches of 0.4–0.5 mm/yr, due to ice mass loss of largest ice complexes, overprint a characteristic area of slower uplift of 0.1–0.2 mm/yr, signature of the phenomenon in the whole Alpine chain. Viscous stress relaxation in the lower crust, due to glacier mass loss after the end of the Little Ice Age, is expected to produce uplift rates of 0.32 mm/yr, leading to a total viscoelastic response up to 0.8 mm/yr. Our predictions in the western Alps show that viscoelastic response to present day glacier shrinkage forms a substantial fraction (half) of the observed uplift data. Attempts to constrain the contributions arising from active Alpine tectonics and drainage must account for this uplift signal. Citation: Barletta, V. R., C. Ferrari, G. Diolaiuti, T. Carnielli, R. Sabadini, and C. Smiraglia (2006), Glacier shrinkage and modeled uplift of the Alps, Geophys. Res. Lett., 33, L14307, doi:10.1029/2006GL026490.

The fluctuations of Italian glaciers during the last century : a contribution to knowledge about Alpine glacier changes

Abstract. This paper describes the recent evolution of Italian glaciers through an analysis of all available terminus fluctuation data that the authors have entered in a glaciers database (named GLAD) containing 883 records collected on glaciers from 1908 to 2002. Furthermore, a representative subset of data (249 glaciers located in Lombardy) was analysed regarding surface area changes. For the analysis of terminus fluctuations, the glaciers were sorted by size classes according to length. The data showed that during the 20th century Italian Alpine glaciers underwent a generalized retreat, with one distinct and well documented readvance episode that occurred between the 1970s and mid‐1980s, and a poorly documented one around the early 1920s. The rates of terminus advance and retreat have changed without significant delays for the larger glaciers with respect to the smaller ones. However, the smaller the glacier, the more limited the advance (if any) during the 1970s and early 1980s. The behaviour of glaciers shorter than 1 km appears to have changed in the last decade, and between 1993 and 2002 they retreated at a very high rate. The analysis of the subset of data led to a quanti‐fication of surface reduction of c. 10% from 1992 to 1999 for glaciers in Lombardy. Small glaciers proved to contribute strongly to total area loss: in 1999, 232 glaciers (c. 90% of the total) were smaller than 1 km2, covering 27.2 km2 (less than 30% of the total area), but accounted for 58% of the total loss in area (they had lost 7.4 km2).

Glacier surface-area changes in Sagarmatha national park, Nepal, in the second half of the 20th century, by comparison of historical maps

We investigate variations in the surface area of glaciers in Sagarmatha national park, Nepal, during the second half of the 20th century through comparison of a map applicable to the late 1950s with the official map of Nepal in the early 1990s. The comparison reveals a slight overall decrease in glacier area (by 4.9%, from 403.9 to 384.6 km 2 ), a result which, though potentially subject to errors arising from cartographic interpretation, is in line with the area reductions found by other studies of Asian glaciers. We find that the areas of some individual glaciers, the largest situated at higher altitudes, increased during the study period. This was most apparent for the glaciers oriented to the south, with the increase occurring mainly in the glacier accumulation zones while the fronts tended to recede. Meanwhile, the smaller glaciers, situated lower and on steep basins, experienced a reduction. For the smaller glaciers, the sections most affected by change were the accumulation zones, and these glaciers showed a tendency for the front to advance. In this region there is a lack of climate data for high altitudes. Nevertheless, observations from stations situated around the park suggest that, alongside temperature variations which are often considered the primary factor eliciting glacier response, changes in precipitation play a significant role.

Glacier retreat and climate change: Documenting the last 50 years of Alpine glacier history from area and geometry changes of Dosdè Piazzi glaciers (Lombardy Alps, Italy):

The recent rapid mass loss of mountain glaciers in response to climate warming has been reported for high and low latitudes all over the Earth. The paper analyses and discusses the recent evolution of a representative glacierized group within the Italian Alps, the Piazzi—Dosdè, where small glaciers are experiencing considerable retreat and shrinking. We analysed aerial photos to calculate area and geometry changes in the time window 1954—2003, and glaciological and geomorphological surveys were also performed. The estimated area change during 1954—2003 was —3.97 km2 (—51% of the area coverage in 1954). Area reduction increased more recently: area change during 1991—2003 (12 years) was —1.74 km2, against —0.67 km2 during 1981—1991 (10 years), and —1.57 km 2 during 1954—1981 (27 years). Moreover, analysis of the most recent orthophotos acquired during the summer of 2003 under exceptional conditions (i.e. total absence of snow cover) allowed observation and mapping of changes affecting glacier shape and morphology, including growing rock outcrops, tongue separations, formation of proglacial lakes, increasing supraglacial debris and collapse structures. Such processes cause positive feedbacks that accelerate further glacier disintegration once they appear. From a geodynamical perspective, the Dosdè Piazzi is now experiencing transition from a glacial system to a paraglacial one; areas where in the past the shaping and driving factors were glaciers are now subject to the action of melting water, slope evolution and periglacial processes.