CONTRIBUTION TO THE COMPREHENSION OF CLIMATE CHANGE TOWARDS CRYOSPHERE AND ATMOSPHERIC ANALYSIS: THE CASES STUDY OF CHANGRI NUP GLACIER, NEPAL HIMALAYAS AND OF FORNI GLACIER, ITALIAN ALPS.

In this PhD Thesis are reported the main results from an interdisciplinary research focused on evaluating impacts and effects of black carbon (BC) on glacier snow and ice melting. With this purpose we selected two glaciers: the Changri Nup glacier (Nepal, Himalaya) and the Forni glacier (Italian Alps). The glaciers have been chosen due to their representativity (geographical setting, size, morphology) and the availability of meteorological and energy data collected at the glacier surface through Automatic Weather Stations (AWSs). In fact on both the glaciers AWSs have been installed in the recent years and they have been running without meaningful interruptions thus permitting to analyze glacier micrometeorology and to evaluate glacier surface energy balance and its variability (data are sampled with a hourly frequency all over the year). Moreover we planned and performed field campaigns to collect snow samples for describing chemical and physical features of soot and dust present in the glacier snow. More precisely, since the Autumn 2005 and AWS has been running at the melting surface of the Forni Glacier (Italian Alps). The AWS is property of UNIMI and it attends the international network SHARE (Stations at High Altitude for Research on the Environment) promoted and managed by EVK2CNR Committee. Within the Ev-K2-CNR Project SHARE on February 2010 an AWS has been installed on the debris-free surface of the Changri Nup Glacier (Nepal, Himalayas, Sagarmatha Nationa Park) at 5,700 m asl to acquire meteorological data and energy fluxes (incoming and outgoing) at the glacier surface. The AWS is property of EvK2CNR Committee. The acquired data permit the calculation of glacier energy balance and high resolution analysis of glacier albedo. In the present study more than 85.000 meteorological parameters, related to the time window 2010-2012 and collected by The Changri Nup AWS, have been analyzed, processed and validated. Average daily parameters estimated at glacier surface have been: temperature: -4.61 °C, relative humidity: 78.47%, atmospheric pressure: 505.6 hPa, SWin: 220 W m-2, SWout:136 W m-2, LWin: 240 W m-2, LWout: 280 W m-2, wind speed: 1.48 m s-1, prevalent wind direction: 183°. Yearly albedo, deriving from SWout/SWin was 0.7, with an average of 0.75 for snow and 0.26 for glacier ice. Instead data from Forni AWS were already available thanks to another PhD research presently on line at the University of Milan. Ablation season at the Changri Nup glacier occurred in summer period, in the monsoon season, when the temperature conditions (T>0°C) and radiation and rain precipitation increase the melting process. Results have been compared with the Alpine site of Forni glacier, the largest Italian valley glacier, located in the Stelvio National Park and characterized by a “strategic” location on the Central-Eastern Alpine sector, able to be reached by southern fluxes and close to the northern Alpine Italian boundary. This part of the research was performed within the SHARE STELVIO project aiming at detecting and quantifying climate change evidences and effects on a sensible area located in the Stelvio National Park – Lombardy sector (600 km2 of area). This project will permit to evaluate composition, quality and variability of high elevation atmosphere and effects on the alpine water resource (i.e. snow, glaciers and meltwater rivers). In both sites the main component deterring melting are positive temperature and shortwave radiation, this latter higher in the Himalaya due to the difference of latitude, altitude and incident direction. Melting season in the Alps is longer than in the Himalaya and in both sites the effect of latent and sensible heat fluxes have a minor effect in driving melting processes. Both sites are characterized by a typical katabatic wind regime. At the Changri Nup glacier surface some ablation stakes have been positioned in the debris free part of the glacier and two of these stakes were located nearby the AWS. Glacier ablation was evaluated through field campaigns twice: February-May 2010 and May-November 2012. The field data allowed to compare measured glacier ablation with melting amount derived from energy balance measurements and to evaluate the reliability of our computations. It was found by previous authors that absorbing aerosols and dust play a key role in varying snow and ice albedo and in driving glacier ablation on several high elevation glaciers. In this study, by coupling energy data (from the AWS) with the atmospheric measurement of BC concentration allow the investigation of the relations among atmosphere and cryosphere and to quantify impacts of atmospheric black carbon deposition on glacial ablation rates. In Himalaya atmospheric observations are carried out at the Nepal Climate Observatory-Pyramid (NCO-P) located at 5,079 m asl near the Pyramid Laboratory Observatory, while at Forni glacier a summer campaign has been held in 2012 at Guasti Hut (c. 3200 m asl). Results at Changri Nup glacier were consistent with the typical estimation available in literature of BC deposition and % of albedo reduction in premonsoon season, where the atmospheric concentration are high. Experimental results reports that at Changri Nup the % of albedo reduction has been 4.26% for an estimated BC deposition in snow of 49 µg kg-1 consistent with the concentration range of BCC in snow of 26.0–68.2 μg kg−1 due to snow density variations between 195–512 kg m−3 as reported in literature. The same estimation has been done at Forni Glacier too, but results were different because the summer BC monitoring campaign detected BC concentrations in the atmosphere typical of free troposphere background conditions, thus in the analyzed period, their deposition didn’t have a predominant effect in driving melting process. To compare the estimated BC deposition in snow deriving from atmospheric measurements, snow samples has been done at the Changri Nup glaciers and the chemical analysis allow to determine a typical premonsoon concentration consistent with literature data and with the experimental estimation done at Changri Nup glaciers. Future step will foresee a further analysis of these results, thanks also to the availability of long term dataset, moreover, in order to improve the knowledge of the effect of dust and aerosol deposition on glacier, more samples will be collected and analyzed.