Discovery and Correction of Bias in Precision Landmark Location

Precision Landmark Location (PLL) estimation is an integral part of 3D motion tracking. Circular landmark location estimation is one method of PLL. Current methods of estimation lead to systematic errors with a magnitude of up to .02 pixels. Estimation inaccuracies of this magnitude lead to unacceptable errors in depth measurement, the largest source of error. In the scope of this thesis, inadequacies in circular landmark location are uncovered and techniques to correct these errors are analyzed, tested, and demonstrated. Deviations in simulated images are seen to be reduced by a factor of three and the variances of real-world data were reduced by half. This thesis predicts and observes increased accuracy in the 3D motion tracking technology

Applicazione di tecniche remote sensing per lo studio dell'evoluzione e della dinamica criosferica in aree remote e di alta quota

I ghiacciai sono efficaci indicatori climatici poich\ue8 si modificano in risposta ai cambi del clima (es. temperatura e precipitazioni). L'attenzione sui ghiacciai di montagna sta aumentando tra la comunit\ue0 scientifica per via del loro sempre pi\uf9 evidente arretramento a scala globale negli ultimi cinquant'anni. Ci\uf2 \ue8 conseguenza del riscaldamento globale. Comprendere il comportamento dei ghiacciai in risposta al cambio climatico \ue8 di enorme importanza non solo per arricchire la conoscenza scientifica, ma anche per poter meglio gestire in futuro le situazioni di rischio naturale che possono colpire le popolazioni che vivono nelle zone montuose, sia nel breve termine (es. GLOF), sia nel lungo (es. Siccit\ue0). Questa tesi di dottorato analizza differenti aspetti della criosfera (ghiacciai e neve) per descriverne la variabilit\ue0 recente e le relazioni con la dinamica climatica. Inizialmente ci si \ue8 concentrati sul Karakorum. Questa \ue8 un\u2019area particolare per gli studi criosferici, che non segue i trend globali di regresso; infatti, in questa zona il bilancio di massa netto dei ghiacciai nei primi anni del ventunesimo secolo \ue8 stato leggermente positivo, con anche taluni casi di espansione. Questa eccezionale situazione \ue8 riconosciuta con il nome di Anomalia del Karakorum (Karakoram Anomaly). Pi\uf9 precisamente il presente elaborato si focalizza sulla zona del Central Karakoram National Park (CKNP), un'area protetta nel nord del Pakistan, rappresentativa della glaciazione dell'intera catena del Karakorum. In questa regione, i venti occidentali rappresentano il sistema di venti dominante e sono presenti nella stagione invernale, mentre la confinante regione Himalayana \ue8 sotto l'influenza predominante dei monsoni, che sono venti estivi. Il presente lavoro descrive in maniera completa lo stato dei ghiacciai del CKNP e la loro recente evoluzione. Ci\uf2 \ue8 stato possibile a seguito della compilazione del catasto glaciale del parco per gli anni 2001 e 2010, a sua volta descritto nel dettaglio nel presente elaborato. Inoltre \ue8 discussa l'analisi dei cambiamenti climatici poi messa in relazione con quelli glaciali, per poter comprendere le cause dietro l'Anomalia del Karakorum. Il cambiamento areale dei 711 ghiacciai mappati nell'area di studio \ue8 stato -0.4 \ub1 202.9 km2 (su 4605.9 \ub1 86.1 km2 nel 2001), il che evidenzia una generale situazione di stabilit\ue0. Anche l'analisi climatica supporta tale condizione di stabilit\ue0. Durante il periodo 2001\u20132010 si \ue8 osservato grazie ai dati del sensore MODIS un leggero aumento delle aree coperte da neve a fine estate. Allo stesso tempo, dati meteo dalle stazioni disponibili hanno rivelato un aumento delle nevicate e una diminuzione della temperatura media dell'aria in estate fin dal 1980, il che si tradurrebbe in coperture nivali pi\uf9 persistenti durante la stagione ablativa. Questi risultati vanno a favore della preservazione glaciale nelle zone di ablazione dovuta a una copertura di neve pi\uf9 duratura, e un maggiore accumulo a quote pi\uf9 alte, presupponendo bilanci di massa netti tendenti al segno positivo. L'altro principale obiettivo del presente elaborato di tesi \ue8 quello di fornire un modello di semplice utilizzo per quantificare l'ablazione di ghiaccio alla superficie glaciale. Dal momento che una copertura detritica sopraglaciale \ue8 in grado di alterare la fusione del ghiaccio vicino alla superficie in funzione dello spessore, il modello tiene conto di due diversi casi: una parte stima l'ablazione per le aree di ghiaccio scoperto con un metodo definito enhanced T-index; l'altra stima la fusione per le zone coperte da detrito, utilizzando un modello di flusso di calore conduttivo. Per quanto concerne le parti coperte da detrito, \ue8 stata prodotta una mappa degli spessori detritici che \ue8 poi stata usata come input per il modello, assieme alla radiazione solare entrante distribuita. Per le aree scoperte da detrito, sono state derivate la temperatura dell'aria e la radiazione entrante distribuite attraverso i dati delle stazioni meteo automatiche presenti nell'area, in seguito usate come input. L'altro parametro necessario \ue8 un modello di elevazione del terreno. In particolare, la distribuzione degli input meteorologici \ue8 stata validata con dati di altre due stazioni presenti all'interno del CKNP (le stazioni di Urdukas e Concordia). L'ablazione modellata \ue8 risultata essere fortemente concorde con le misurazioni effettuate sul ghiacciaio del Baltoro nel 2011, ghiacciaio rappresentativo di tutto il CKNP. Due campioni dello stesso set di dati di fusione misurati su terreno sono stati usati ciascuno rispettivamente in sede di calibrazione e validazione. La fusione nivale \ue8 stata ignorata dal momento che mancavano dati di neve sistematici nell'area di studio. Il modello \ue8 stato fatto girare durante il picco della stagione ablativa (23 luglio\u20139 agosto 2011), durante il quale l'acqua di fusione deriva primariamente dalla fusione glaciale, mentre quella nivale ha un ruolo decisamente minore in questa regione. Il modello ha calcolato un totale di acqua da fusione glaciale pari a 1.963 km3 (0.109 km3 al giorno in media). Quella derivante dalle parti coperte da detrito ammonta a 0.223 km3 (0.012 km3 al giorno in media; min\u2013max 0.006\u20130.016 km3 al giorno), mentre per le parti a ghiaccio scoperto \ue8 1.740 km3 (0.097 km3 al giorno in media; min\u2013max 0.041\u20130.139 km3 al giorno). Tale quantit\ue0 \ue8 paragonabile al 14% di tutta l'acqua contenuta in una grande diga strategica lungo il fiume Indo, di cui i ghiacciai del CKNP sono tributari. I test di sensitivit\ue0 del modello suggeriscono che un aumento delle superfici coperte da detrito sui ghiacciai (probabile per via dell'aumento di eventi di macrogelivazione e di frane) avr\ue0 un notevole impatto sulla fusione effettiva in funzione dei nuovi spessori detritici, e l'ablazione aumenter\ue0 sensibilmente se la temperatura dell'aria dovesse alzarsi. Successivamente l'attenzione del presente elaborato di tesi \ue8 concentrata sulle Ande Cilene e sulla variabilit\ue0 della copertura nevosa. Un obiettivo principale parallelo della presente ricerca \ue8 stato infatti quello di individuare una metodologia basata sul telerilevamento per studiare la variazione della copertura nevosa ad una risoluzione spazio-temporale accettabile. Il sensore MODIS si \ue8 rivelato il pi\uf9 idoneo allo scopo ed \ue8 stata implementata una metodologia che permettesse di estrarre mappe di copertura di neve in maniera automatica dalle informazioni raccolte dal sensore stesso. In particolare, sono stati studiati diciotto bacini idrografici di montagna delle Ande centrali in Cile durante il periodo 2008\u20132011. La stessa metodologia \ue8 stata esportata e adottata per l'analisi della neve nel CKNP come detto. L'area di studio \ue8 stata divisa in tre sotto-zone (Settentrionale, Centrale, Meridionale), per alleggerire il carico di calcolo dell'analisi. In generale, l'area coperta da neve \ue8 diminuita nel corso dei quattro anni di riferimento. I valori massimi sono stati ritrovati nella zona centrale, mentre fattori topografici e climatici (i.e. quote basse pi\uf9 a sud e un clima pi\uf9 arido nel nord), hanno limitato la deposizione della neve nelle altre zone. La linea della neve \ue8 pi\uf9 alta nella zona settentrionale a causa della presenza dell'altopiano, e si abbassa via via verso la zona merdionale. Nella zona settentrionale i minimi di copertura nivale vengono raggiunti prima che nelle altre zone e durano pi\uf9 a lungo (da novembre a marzo), probabilmente a causa del clima pi\uf9 arido. Durante l'intero periodo i valori massimi di copertura nevosa si ritrovano verso ovest. Al termine dell'elaborato e pertinente al tema principale delle applicazioni del telerilevamento allo studio della criosfera, sono presentati alcuni esempi di analisi di ghiacciai di diversa tipologia, dimensione e area geografica. Si tratta di sei casi, fra cui sono presenti tre ghiacciai alpini (Miage, Freney, Aletcsh), ghiacciai equatoriali (i ghiaccia del Kilimajaro), l'Harding Icefield in Alaska e un esempio di ghiacciaio antartico (la Drygalsky ice Tongue).Glaciers are sensitive climate indicators because they adjust their size in response to changes in climate (e.g. temperature and precipitation). The attention paid by the scientists to mountain glacier change is increasing as there are robust evidence of a global glacier shrinkage over the past five decades, which in turn is the consequence of global warming. Understanding the glacier response to climate change is of tremendous importance not only for improving scientific knowledge, but also to predict and manage water resources and natural risks for the people living in mountain areas in the short (e.g. glacier lake outburst floods), and long term (e.g. droughts). In this thesis are analysed different cryospheric elements (mainly glaciers and snow coverage) to describe their recent evolution and to look for relations, if any, with climate trends. Firstly, the focus is put on the Karakoram glaciers. Although a general worldwide retreat of mountain glaciers has been acknowledged by the scientific community, the Karakoram region represents an exception in this sense. Indeed, the net mass balance of the glaciers here in the early twenty-first century was slightly positive, and even some are expanding and thickening. This anomalous behaviour is known as Karakoram Anomaly. More precisely the study area is the Central Karakoram National Park (CKNP), a protected national park in Northern Pakistan representative of the glaciation of the whole Karakoram Range. The westerlies represent the dominant wind system and they occur during winter, while the neighbour Himalayan region is mainly influenced by the summer moonson. A comprehensive description of the state of the CKNP glaciers and of their recent evolution is presented. This was made after the compilation of the glacier inventory of the park for the years 2001 and 2010, which is also presented. Moreover, the analysis of the regional climate change in the recent years is also discussed and related to the actual glacier change, in order to understand the causes behind the Karakoram Anomaly. The glacier area change of the 711 glaciers mapped in the study zone during 2001\u20132010 was only -0.4 \ub1 202.9 km2 (over 4605.9 \ub1 86.1 km2 in 2001), evidencing a general stability. The climate analysis supports glacier stability in the area. A slight increase in late summer snow cover area during 2001\u20132010 was observed from MODIS snow data. At the same time, the available weather stations revealed an increase of snowfall events and a decrease of mean summer air temperatures since 1980, which would translate into more persistent snow cover during the melt season. These results support an enhanced glacier preservation in the ablation areas due to a long-lasting snow cover, and stronger accumulation at higher altitudes, pushing towards positive net balances. The other major aim of the present work is to provide a simple model to evaluate ice melt at the glacier surface. As the supraglacial-debris cover can alter ice ablation close to the glacier surface depending on its thickness, the model was made up of two parts: one which computes the ice melt over the bare ice areas using an enhanced T-index formula; and one for the debris-covered areas using a conductive heat flux module. For the debris-covered parts, the debris thickness map is produced and then provided to the model as input for the computation, other than the distributed shortwave incoming radiation. For the bare ice areas, the modeled air temperature and shortwave incoming radiation are derived from the automatic weather stations present in the CKNP and given to the model. The other model requirement is the digital elevation model. In particular, the meteorological input data were distributed starting from data acquired at Askole automatic weather station, located within the CKNP. The meteorological distribution was validated by comparison with data from other two AWS in the same park limits (Urdukas and Concordia). The modeled ablation data were in strong agreement with measurements collected in the field during 2011 on Baltoro glacier, which is representative of CKNP glaciers. Two sets of the same ablation dataset collected in the field in the CNKP area were used separately for calibration and validation. Snow melt was neglected since snow data in the study area was not systematically available. The model was run against the peak ablation season (23 July\u20139 August 2011), when meltwater mainly comes from ice melt, with snow thaw playing a minor role in this region. The total freshwater from the ablation areas of CKNP glaciers estimated by the model was 1.963 km3 (0.109 km3 d\u20131 on average). The meltwater from the debris-covered parts was 0.223 km3 (0.012 km3 d\u20131 on average; min\u2013max 0.006\u20130.016 km3 d\u20131), and 1.740 km3 (0.097 km3 d\u20131 on average; min\u2013max 0.041\u20130.139 km3 d\u20131) from debris-free sectors. The estimated total freshwater corresponds to 14% of the water contained in a large strategic dam along the Indus River, of which all the CKNP glaciers are tributaries. The sensitivity tests suggest that any increase in the extent of debris coverage (which will likely occur due to augmented macrogelivation processes and rockfall events), will affect melt depending on new debris thickness, and melting will increase largely if summer air temperature increases. The second major focus of this research is put on the snow cover variability of the Chilean Andes. A parallel major aim of this research work is to implement a methodology based on remote sensing to study the snow cover variation on an acceptable spatio-temporal resolution. The MODIS sensor was chosen as the most suitable for this purpose and a methodology for deriving snow maps automatically from it is described and applied for analyzing the SCA variation over 18 watersheds of the central Andes in Chile during 2008\u20132011. The same methodology was then adopted for the climate analysis in the CKNP as mentioned. The study area was divided into three sub-zones (Northern, Central, and Southern), for easing the computation of the snow analysis. Overall, SCA decreased during the four considered years. The maximum SCA was found in the Central Zone, while the topographic and climatic features (i.e. lower altitudes in the South, and a drier climate in the North), limited snow deposition elsewhere. The snow line was found higher in the Northern zone due to the presence of the plateau, while it decreases southwards. In the Northern Zone the minimum SCA was reached sooner than elsewhere, and it lasted for a longer period (November to March), probably because of the drier climate. West aspects showed the maximum of SCA in all zones throughout the study period. Finally, some examples of application of remote sensing to glacier related studies is presented for glaciers of various typology, size, and localization. Six case studies are shown, amongst which there are three alpine glaciers (Miage, Freney, Aletcsh), equatorial glaciers (the Kilimanjaro glaciers), the Harding Icefield in Alaska, and an Antarctic glacier (the Drygalsky Ice Tongue)

THE DARK SIDE OF THE ICE: GLACIOLOGICAL AND BIOLOGICAL ASPECTS OF SUPRAGLACIAL DEBRIS

This research deals with a multi-disciplinary analysis of the supraglacial debris. Debris significantly influences the evolution of glacier surface, its energy balance, and the carbon fluxes and storage. In this work through a multi-disciplinary approach, we focused on this dark side of the glaciers from two different points of view: the glaciological and the biological one. In the last decades, the large majority of glaciers, including those on the Italian Alps, showed a great increase of supraglacial debris cover. The analyses performed on aerial and UAVs imagery on a wide glacierized sector of Italy, highlighted that the debris-covered area doubled in the period 2003\u20132012, reaching an increase up to 30.10% of the whole glacier area. However, these changes in surface features, fed by an increased availability of debris, occurred with different patches, according to the physical properties of the bedrocks hosting the glaciers. This suggests that further studies are needed to quantify the occurrence and distribution of supraglacial debris on all the Italian glaciation. The ice albedo and, consequently, the energy balance of glaciers not only are affected by the presence or absence of a thick and continuous debris cover on the glacier surface, but also by the amount and distribution of the fine and sparse debris and dust that discontinuously cover glaciers. Sparse debris is thus important for determining the evolution of ice bodies, but its quantification is arduous, as the availability of high-resolution imagery, both from satellite and UAV, is mandatory. In this work we showed that the processing of an UAV image of the glacier through a segmentation approach allows describing ice features at a small-scale, including the distribution of fine debris. Moreover, we found evidence of darkening phenomena due to an increased amount of fine and sparse debris on the surface of glaciers. The darkening of glaciers is probably favoring organisms living in the supraglacial debris; however, organisms can promote glacier darkening because they produce dark matter (e.g. humic substances) and are themselves part of the dark debris quantified in glaciological analyses. A positive feedback seems therefore to occur on glacier surface, promoting the increase of supraglacial debris. The analyses of the life on supraglacial debris indicates that a glacier cannot be considered as an isolated environment, although it has different characteristics than the surrounding areas. Nematodes and Rotifers, for instance, can diffusely colonize supraglacial debris only in the presence of allochthonous organic matter, which represents the main source of organic carbon for these organisms in supraglacial environments where primary producers are scarce. Moreover, the study of bacterial communities in snow highlighted a possible contribution of organisms transported from the area where the air masses originated, as well as a non-negligible input of local air bacteria, maybe due to the deposition of local particulate during snowfall. This strong relation between glacier and ice-marginal environments is observable also from the bacterial community of the cryoconite holes. Indeed, we showed that ice-marginal environments may act as sources of bacteria for these micro habitats, but differences in environmental conditions limit the number of bacterial strains that may survive in them. At the same time, cryoconite holes host some organisms that were not found in any ice-marginal environment we sampled, thus suggesting that some bacteria may reach cryoconite from distant sources. These bacterial communities of cryoconite holes have a wide temporal evolution throughout an ablation season, with autotrophic Cyanobacteria populations dominating communities after snow melt, and heterotrophic populations increasing in abundance later in the season. The complex bacterial communities that inhabit glacier surface have large impacts on biogeochemical processes, in particular on the carbon cycle. In fact, we provided evidence for the occurrence in these environments of metabolic pathways that differ from those of oxygenic phototrophs and the respiration of heterotrophic organisms beforehand described on glacier surface. Indeed, we observed high abundance of heterotrophic anoxygenic phototrophs, suggesting that light might supplement the energy needed by the organisms permitting them to use some organic molecules as carbon sources. Furthermore, these communities could produce CO2 also by the oxidation of CO, which may be produced by photodegradation of organic matter present in the cryoconite. Finally, we investigated the fate of contaminants on the glaciers surface assessing a key role of the bacteria in the chlorpyrifos degradation. In summary, the results presented in this PhD thesis improved our knowledge of the supraglacial debris, its components and its evolution. The double view on the glacier system, both glaciological and biological, permits a deeper description of the mutual relations between bio and geo components

COUPLING GLACIO-HYDROLOGICAL RESPONSE TO CLIMATE VARIABILITY IN MT EVEREST REGION IN CENTRAL HIMALAYA

Mt. Everest region in the central Himalaya is one of the most heavily glacierized parts of the Himalaya that is characterized by large debris-covered glaciers and many glacial lakes. The glaciers and ice are important sources of fresh water and play vital role in modulating the climate and the hydrological process. Previous studies from different parts of the Himalaya and around the world have revealed climate change at regional and global-scale and in general, shrinking of glaciers and ice caps. Climate change is thus, expected to impact in many ways to Cryosphere, hydrological process, and human livelihood. Temperature is often suggested to be increasing and considered as the main driver of change, however, in the higher elevations where the glaciers exist, climatic data are rarely available and limiting the climate related interpretation. This study is therefore conducted with the aim of linking variation of glaciers, glacial lakes, and river flow to local climatic trends in the higher elevations of Mt. Everest region. The study uses a comprehensive multi-temporal data from different sources: satellite observations, ground hydro-meteorological stations, and regular gridded and reanalysis climate data from the regional and global products (1960s to 2013). First, using the weather data from ground stations, gridded, and reanalysis products, the climatic trends and climate variability are evaluated. From 1979 to 2013, temperature has increased by 0.052 \ub0C a-1, while the precipitation has shown an increasing tendency in 1960s to early 1990s and significantly decreasing afterward. During 1994\u20132013 period, at an elevation of ~ 5000 m, minimum temperature (0.072 \ub1 0.011 \ub0C a-1) has increased more than maximum temperature (0.009 \ub1 0.012 \ub0C a-1), with an average temperature increase of 0.044 \ub1 0.008 \ub0C a-1 in the last two decades. The increases in the temperature are observed during the pre- and post-monsoon months, favouring melting ice close to the glacier terminus. At the same elevation, precipitation has significantly decreased (-9.3 \ub1 1.8 mm a-1) for all months, corresponding to a loss of 47 % during the monsoon. Second, the glacier changes are studied within the Sagarmatha (Mt. Everest) National Park (SNP; glacier area: ~ 400 km2) between 1962 and 2011, using multi-temporal optical satellite imagery, assisted by topographic maps. During the period, glaciers have experienced a surface area loss of 13.0 \ub1 3.1 %, an average terminus retreat of 403 \ub1 9 m, a Snow-Line Altitude (SLA) upward shifting of 182 \ub1 22 m, and an increasing of debris- covered area by 17.6 \ub1 3.1 %. An accelerated rate of glacier shrinkage is observed after the 1990s, which is caused not only due to increased temperature, but also as a result of a significant decreasing precipitation over the last decades. Moreover, selected glaciers have indicated a significant decreasing glacier flow velocities from the 1990s to recent year and a significant loss of glacier thickness (0.73 \ub1 0.63 m a-1) in the last decade. Third, a complete mapping and characterization of a total of 624 glacial lakes with surface area of 7.43 km2 (\ub118 %) are conducted in the SNP, with particular focus on conditions related to the formation of lakes using 2008 satellite imagery. Further, evolutions of glacial lakes are examined using the satellite imagery and topographic maps between 1963 and 2013. Three types of glacial lakes (supra, pro, and unconnected) present in the SNP have their distinctive potential to explain the glaciological and climatic conditions. Results show that the slope of the glacier where lakes are located influence the supraglacial lake formation. Furthermore, the slope to glacier upstream favours the formation of the supraglacial lakes, as a boundary condition. The formation of proglacial lakes is related to the growing and coalescing of the supraglacial lakes. The unconnected lakes are evaluated as a useful indicator of precipitation trend. During the study period (1960s\u20132011), both number and surface area of supraglacial lakes has continuously increased (number +109.7 %; area +13.3 %) with an accelerated rate in the last decade due to increase in the glacier melting. Proglacial lakes are more or less constant in both numbers and size, except Imja Lake that have exceptionally increased, while the surface area of unconnected lakes has increased from 1960s\u20131990s (+4.3 %) and decreased from early 1990s afterward (-10.9 %). The thesis has shown that the accelerated rate of glacier shrinkage and the decreasing of the unconnected lakes in the last decades are associated to decreasing precipitation. Supraglacial lakes behaviour confirms the acceleration of the negative mass balance of glaciers due to the reduced ice velocities caused by decreased precipitation. Finally, the hydrological dynamics of the Dudh Koshi river examined by stochastic frequency analysis, physically-based hydrological models, and multilinear regression using river discharge data and climate data. The analysis suggests that the Dudh Koshi river discharge is mainly dependent on precipitation from 1960s to 2000s, however a non-stationarity in the river discharge is observed since the early 2000s, indicating increased discharge, not justifiable by the observed weakening monsoon. The study concludes by underlining that an accelerated glacier melting as observed through the glacier change analysis affects an increasing of the discharge