Preliminary results from antarctic albedo from remote sensing observations

The aim of the study is to analyse the surface albedo of the Ant-arctica and investigate eventual signals of variations in space and time between summer 2000/2001 and 2011/2012 by means of the GLASS albedo product. We followed a step-by-step procedure from micro- to macro-scale. At first, we analysed 95 glaciers around the continent, and we found limited temporal variability. Then, looking at spatial varia-tions, we divided Antarctica based on oceanic basins and by continen-tality. We found spatial signals, since mean albedo values range between 0.79 (Pacific and Atlantic basins) and 0.82 (Indian basin) and between 0.76 (along the shore) and 0.81 (inner continent). An increasing vari-ability was found from the inner continent to the shore, and heteroge-neous patterns among the basins, most likely due to meteorological and environmental conditions (mainly: temperature, precipitation, katabatic winds). Finally, the general patterns observed (considering the specific gla-ciers, the three basins and the three continentality sectors) were verified by the analysis of the whole continent and we did not find a significant change of summer averages over time, as they range between 0.79 and 0.80

Distribution of the surface energy budget: Preliminary analysis on the incoming solar radiation. the case study of the Forni Glacier (Italy)

This study represents a contribution to distribution of the surface energy budget of the Forni Glacier (Ortles-Cevedale Group, Upper Valtellina, Italy). The analyses are based on data acquired at S. Caterina Valfurva (a village in the glacier valley at 1768 m ellipsoidal elevation WGS84) by an Automatic Weather Station (AWS) installed and managed by the Lombardy Agency for the Environment ("ARPA Lombardia"). We focus on the two most important meteorological parameters affecting surface energy budget: air temperature (T) and incoming shortwave radiation (SWin). Data collected from the ARPA AWS are used to evaluate these parameters at the glacier surface during the meteorological summer 2009 (from 1st June to 31st August 2009) and then the computations are validated through comparison with data recorded by an AWS installed at the surface of Forni Glacier tongue ("AWS1 Forni", 2669 m ellipsoidal elevation WGS84). The analysis of the distributed air temperature data enabled identification of the lowest value (-11.9 degrees C), found at the Mount S. Matteo peak (3669 m) on 22nd June at 8: 00 pm, and the highest value (+16.1 degrees C), recorded at the glacier terminus (2497 m) on 23 rd July at 2: 00 pm. The seasonal temperature amplitude (Tmax-Tmin) was 28 degrees C. The hottest week was 20th-26th July 2009 and the coldest was 1st-7th June 2009. Regarding daily SWin distribution, the maximum value (406.9 Wm(-2)) was recorded on 13th June and the minimum (28.5 Wm(-2)) on 6th June. From the analysis of hourly SWin values we could distinguish between days with clear sky conditions and days with intense cloud cover. Weekly mean SWin data showed the greatest value (327.1 Wm(-2)) from 20th-26th July 2009 and the lowest (207.8 Wm(-2)) from 22nd-28th June 2009. Furthermore, in analysing SWin it is critical to take into account the problem of shading. Using the Hillshade tool of ArcGIS, which takes into account only the slope and the aspect of each grid cell neglecting the surrounding topography effect, we compiled 66 shadow maps. Finally this study represents a first approach in modelling the distributed incoming solar radiation. In fact the considered driving factors are the elevation, the slope and the aspect of each grid cell. The next step will consist in taking into account the surrounding topography and the actual atmosphere conditions as well

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

AbstractBaltoro 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

Modelling hydrological components of the Rio Maipo of Chile, and their prospective evolution under climate change

We used the Poly-Hydro model to assess the main hydrological components of the snow-ice melt driven Maipo River in Chile, and glaciers' retreat under climate change therein until 2100. We used field data of ice ablation, ice thickness, weather and hydrological data, and precipitation from TRMM. Snow cover and temperature were taken from MODIS. We forced the model using weather projections until 2100 from three GCMs from the IPCC AR5, under three different radiative concentration pathways (RCPs 2.6, 4.5, 8.5). We investigated trends of precipitation, temperature, and hydrology until 2100 in the projection period (PR, 2014-2100) and the whole period (CM 1980-2100, composite), against historical trends in control period (CP, 1980-2013). We found potentially increasing temperature until 2100, except for Spring (OND). In the PR period, yearly flow decreases significantly under RCP85, on average -0.25 m 3 \ub7s -1 \ub7year -1 , and down to -0.48 m 3 \ub7s -1 \ub7year -1 , i.e., -0.4% year -1 against CP yearly average (120 m 3 s -1 ). In the long run (CM) significant flow decrease would, occur under almost all scenarios, confirming persistence of a historical decrease, down to -0.39 m 3 \ub7s -1 \ub7year -1 during CM. Large flow decreases are expected under all scenarios in Summer (JFM) during PR, down to -1.6 m 3 \ub7s -1 \ub7year -1 , or -1% year -1 against CP for RCP8.5, due to increase of evapotranspiration in response to higher temperatures. Fall (AMJ) flows would be mostly unchanged, whileWinter (JAS) flows would be projected to increase significantly, up to 0.7 m 3 \ub7s -1 \ub7year -1 during 2014-2100, i.e., +0.9% year -1 vs. CP under RCP8.5, due to large melting therein. Spring (OND) flows would decrease largely under RCP8.5, down to -0.67 m 3 s -1 \ub7year -1 , or -0.4% year -1 vs. CP, again due to evapotranspiration. Glacier down wasting is projected to speed up, and increasingly so with RCPs. Until 2100 ice loss would range from -13% to -49% (-9%, and -39% at 2050) of the estimated volume at 2012, which changed by -24% to -56% (-21%, and -39% at 2050) vs. ice volume in 1982, thus with rapider depletion in the first half of the century. Policy makers will have to cope with modified hydrological cycle in the Maipo River, and greatly decreasing ice cover in the area

The impact of supraglacial debris on proglacial runoff and water chemistry

Debris is known to influence the ablation, topography and hydrological systems of glaciers. This paper determines for the first time how these influences impact on bulk water routing and the proglacial runoff signal, using analyses of supraglacial and proglacial water chemistry and proglacial discharge at Miage Glacier, Italian Alps. Debris does influence the supraglacial water chemistry, but the inefficient subglacial system beneath the debris-covered zone also plays a role in increasing the ion contribution to the proglacial stream. Daily hydrographs had a lower amplitude and later discharge peak compared to clean glaciers and fewer diurnal hydrographs were found compared to similar analysis for Haut Glacier d’Arolla. We attribute these observations to the attenuating effect of the debris on ablation, smaller input streams on the debris-covered area, a less efficient subglacial system, and possible leakage into a raised sediment bed beneath the glacier. Strongly diurnal hydrographs are constrained to periods with warmer than average conditions. ‘Average’ weather conditions result in a hydrograph with reverse asymmetry. Conductivity and discharge commonly show anti-clockwise hysteresis, suggesting the more dilute, rapidly-routed melt component from the mid-glacier peaks before the discharge peak, with components from higher up-glacier and the debris-covered areas arriving later at the proglacial stream. The results of this study could lead to a greater understanding of the hydrological structure of other debris-covered glaciers, with findings highlighting the need to include the influence of the debris cover within future models of debris-covered glacier runoff

Prediction of future hydrological regimes in poorly gauged high altitude basins: the case study of the upper Indus, Pakistan

In the mountain regions of the Hindu Kush, Karakoram and Himalaya (HKH) the "third polar ice cap" of our planet, glaciers play the role of "water towers" by providing significant amount of melt water, especially in the dry season, essential for agriculture, drinking purposes, and hydropower production. Recently, most glaciers in the HKH have been retreating and losing mass, mainly due to significant regional warming, thus calling for assessment of future water resources availability for populations down slope. However, hydrology of these high altitude catchments is poorly studied and little understood. Most such catchments are poorly gauged, thus posing major issues in flow prediction therein, and representing in fact typical grounds of application of PUB concepts, where simple and portable hydrological modeling based upon scarce data amount is necessary for water budget estimation, and prediction under climate change conditions. In this preliminarily study, future (2060) hydrological flows in a particular watershed (Shigar river at Shigar, ca. 7000 km<sup>2</sup>), nested within the upper Indus basin and fed by seasonal melt from major glaciers, are investigated. <br><br> The study is carried out under the umbrella of the SHARE-Paprika project, aiming at evaluating the impact of climate change upon hydrology of the upper Indus river. We set up a minimal hydrological model, tuned against a short series of observed ground climatic data from a number of stations in the area, in situ measured ice ablation data, and remotely sensed snow cover data. The future, locally adjusted, precipitation and temperature fields for the reference decade 2050–2059 from <i>CCSM3</i> model, available within the IPCC's panel, are then fed to the hydrological model. We adopt four different glaciers' cover scenarios, to test sensitivity to decreased glacierized areas. The projected flow duration curves, and some selected flow descriptors are evaluated. The uncertainty of the results is then addressed, and use of the model for nearby catchments discussed. The proposed approach is valuable as a tool to investigate the hydrology of poorly gauged high altitude areas, and to project forward their hydrological behavior pending climate change

A first attempt to model region-wide glacier surface mass balances in the Karakoram: findings and future challenges

In contrast to the central and eastern part of High Mountain Asia (HMA), no extensive glacier mass loss has been observed in the Karakoram during previous decades. However, the potential meteorological and glaciological causes of the so-called Karakoram Anomaly are diverse and still under debate. This paper introduces and presents a novel glacier Surface Mass Balance Model (glacierSMBM) to test whether the characteristic regional mass balance pattern can be reproduced using recent field, remote-sensing and reanalysis data as input. A major advantage of the model setup is the implementation of the non-linear effect of supra-glacial debris on the sub-surface ice melt. In addition to a first assessment of the annual surface mass balance from 1st August 2010 until 31st July 2011, a sensitivity analysis was performed to investigate the response of Karakoram glaciers to recent climate change. The mean modelled glacier mass balance for the Karakoram during the observation period is -0.92 m water equivalent (w.e.) a-1 and corresponds to an annual melt water contribution of ~12.66 km3. Data inaccuracies and the neglected process of snow redistribution from adjacent slopes are probably responsible for the bias in the model output. Despite the general offset between mass gain and mass loss, the model captures the characteristic features of the anomaly and indicates that positive glacier mass balances are mainly restricted to the central and northeastern part of the mountain range. From the evaluation of the sensitivity analysis, it can be concluded that the complex glacier response in the Karakoram is not the result of a single driver, but related to a variety of regional peculiarities such as the favourable meteorological conditions, the extensive supra-glacial debris and the timing of the main precipitation season

Using daily air temperature thresholds to evaluate snow melting occurrence and amount on Alpine glaciers by T-index models : the case study of the Forni Glacier

Glacier melt conditions (i.e., null surface temperature and positive energy budget) can be assessed by analyzing data acquired by a supraglacial automatic weather station (AWS), such as the station installed on the surface of Forni Glacier (Italian Alps). When an AWS is not present, the assessment of actual melt conditions and the evaluation of the melt amount is more difficult and simple methods based on T-index (or degree days) models are generally applied. These models require the choice of a correct temperature threshold. In fact, melt does not necessarily occur at daily air temperatures higher than 0 \ub0C. In this paper, we applied both energy budget and T-index approaches with the aim of solving this issue. We start by distinguishing between the occurrence of snowmelt and the reduction in snow depth due to actual ablation (from snow depth data recorded by a sonic ranger). Then we find the daily average temperature thresholds (by analyzing temperature data acquired by an AWS on Forni Glacier) which, on the one hand, best capture the occurrence of significant snowmelt conditions and, on the other, make it possible, using the T-index, to quantify the actual snow ablation amount. Finally we investigated the applicability of the mean tropospheric lapse rate to reproduce air temperature conditions at the glacier surface starting from data acquired by weather stations located outside the glacier area. We found that the mean tropospheric lapse rate allows for a good and reliable reconstruction of glacier air temperatures and that the choice of an appropriate temperature threshold in T-index models is a very important issue. From our study, the application of the +0.5 \ub0C temperature threshold allows for a consistent quantification of snow ablation while, instead, for detecting the beginning of the snow melting processes a suitable threshold has proven to be at least 124.6 \ub0C

Hydrology and potential climate changes in the Rio Maipo (Chile)

Glaciers of the central Andes have recently been retreating in response to global warming, with large consequences on the hydrological regime. We assessed here potential climate change impacts until 2100 upon the hydrologic regime of the largely snow-ice melt driven Maipo River basin (closed at El Manzano, ca. 4800 km2), watering 7 M people in the metropolitan region of Santiago de Chile. First, a weather-driven hydrological model including simplified glaciers\u2019 cover dynamics was set up and validated, to depict the hydrological regime of this area. In situ data from recent glaciological expeditions, ice thickness estimates, historical weather and hydrological data, and remote sensing data including precipitation from the Tropical Rainfall Measuring Mission (TRMM), and snow cover and temperature from the Moderate Resolution Imaging Spectroradiometer (MODIS) were used for model set up. We subsequently forced the model with projections of temperatures and precipitations (plus downscaling) until 2100 from the GCM model ECHAM6, according to 3 different radiative concentration pathways (RCPs 2.6, 4.5, 8.5) adopted by the IPCC in its AR5. We investigated yearly and seasonal trends of precipitation, temperature and hydrological fluxes until 2100 under the different scenarios, in projection period (PR, 2014-2100), and we compared them against historically observed trends in control period (CP, 1980-2013). The results show potential significant increasing trends in temperature until 2100, consistently with observed historical trends, unless for Spring (OND). Precipitation varies more uncertainly, with no historically significant changes, and only few scenarios projecting significant variations. In the PR period, yearly flow decreases, significantly under RCP8.5 (-0.31 m3s-1). Flow decrease is expected especially in Summer (JFM) under RCP8.5 (-0.55 m3s-1). Fall (AMJ) flows would decrease slightly, while winter (JAS) flows are projected to increase, and significantly under RCP4.5 (+0.22 m3s-1), as due to sustained melting therein. Spring (OND) flows also would decrease largely under RCP8.5, down to -0.67 m3s-1, due to increased evapotranspiration for high temperatures

Monitoring alpine glaciers from close-range to satellite sensors

In this paper the use of different types of remote-sensing techniques for monitoring topographic changes of Alpine glaciers is presented and discussed. Close range photogrammetry based on Structure-from-Motion approach is adopted to process images recorded from ground-based and drone-based stations in order to output dense point clouds. These are then directly compared to detect local changes by mean of M3C2 algorithm, while digital elevation models are interpolated to find global ice thinning and retreat. Medium-resolution satellite imagery can be exploited to monitor the glacier evolution at lower resolution but including the development and collapse of large crevasses. A case study concerning the Forni Glacier in the Raethian Alps (Italy) is presented to demonstrate the feasibility of the proposed approach by adopting data sets collected from 2016 to 2018