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)

Lake storage variation on the endorheic Tibetan Plateau and its attribution to climate change since the new millennium

Citation: Yao, F., Wang, J., Yang, K., Wang, C., Walter, B. A., & Crétaux, J.-F. (2018). Lake storage variation on the endorheic Tibetan Plateau and its attribution to climate change since the new millennium. Environmental Research Letters, 13(6), 064011. https://doi.org/10.1088/1748-9326/aab5d3Alpine lakes in the interior of Tibet, the endorheic Changtang Plateau (CP), serve as ‘sentinels’ of regional climate change. Recent studies indicated that accelerated climate change has driven a widespread area expansion in lakes across the CP, but comprehensive and accurate quantifications of their storage changes are hitherto rare. This study integrated optical imagery and digital elevation models to uncover the fine spatial details of lake water storage (LWS) changes across the CP at an annual timescale after the new millennium (from 2002–2015). Validated by hypsometric information based on long-term altimetry measurements, our estimated LWS variations outperform some existing studies with reduced estimation biases and improved spatiotemporal coverages. The net LWS increased at an average rate of 7.34 ± 0.62 Gt yr−1 (cumulatively 95.42 ± 8.06 Gt), manifested as a dramatic monotonic increase of 9.05 ± 0.65 Gt yr−1 before 2012, a deceleration and pause in 2013–2014, and then an intriguing decline after 2014. Observations from the Gravity Recovery and Climate Experiment satellites reveal that the LWS pattern is in remarkable agreement with that of regional mass changes: a net effect of precipitation minus evapotranspiration (P-ET) in endorheic basins. Despite some regional variations, P-ET explains ∼70% of the net LWS gain from 2002–2012 and the entire LWS loss after 2013. These findings clearly suggest that the water budget from net precipitation (i.e. P-ET) dominates those of glacier melt and permafrost degradation, and thus acts as the primary contributor to recent lake area/volume variations in endorheic Tibet. The produced lake areas and volume change dataset is freely available through PANAGEA (https://doi.pangaea.de/ 10.1594/PANGAEA.888706)

Shoreline change and coastal vulnerability characterization with Landsat imagery : a case study in the Outer Hebrides, Scotland

Peer reviewedPostprin

Earth Observation Science and Applications for Risk Reduction and Enhanced Resilience in Hindu Kush Himalaya Region

This open access book is a consolidation of lessons learnt and experiences gathered from our efforts to utilise Earth observation (EO) science and applications to address environmental challenges in the Hindu Kush Himalayan region. It includes a complete package of knowledge on service life cycles including multi-disciplinary topics and practically tested applications for the HKH. It comprises 19 chapters drawing from a decade’s worth of experience gleaned over the course of our implementation of SERVIR-HKH – a joint initiative of NASA, USAID, and ICIMOD – to build capacity on using EO and geospatial technology for effective decision making in the region. The book highlights SERVIR’s approaches to the design and delivery of information services – in agriculture and food security; land cover and land use change, and ecosystems; water resources and hydro-climatic disasters; and weather and climate services. It also touches upon multidisciplinary topics such as service planning; gender integration; user engagement; capacity building; communication; and monitoring, evaluation, and learning. We hope that this book will be a good reference document for professionals and practitioners working in remote sensing, geographic information systems, regional and spatial sciences, climate change, ecosystems, and environmental analysis. Furthermore, we are hopeful that policymakers, academics, and other informed audiences working in sustainable development and evaluation – beyond the wider SERVIR network and well as within it – will greatly benefit from what we share here on our applications, case studies, and documentation across cross-cutting topics

Wet-Based Glaciation on Mars

Mars is a glacial planet. It hosts water ice in large polar ice caps, and in thousands of ‘viscous flow features’ in its mid latitudes that are thought to be debris-covered water ice glaciers. These ice deposits range between a few million to ~1 billion years in age and formed during Mars’ most recent epoch, the late Amazonian. The late Amazonian was characterised by extremely cold and arid climate conditions that are not conducive to melting of ice. Consequently, late-Amazonian glaciation has been dominated by cold-based glacier thermal regimes. However, the recent discovery of an esker (a ridge of sediment deposited by meltwater flowing through a tunnel within or beneath glacial ice) associated with a viscous flow feature in the Phlegra Montes region of Mars’ northern mid latitudes provided the first indicative evidence that wet-based glaciation occurred in at least one location during the late Amazonian. In this thesis, I present the discovery of a second candidate esker associated with a viscous flow feature, in the NW Tempe Terra region of Mars’ northern mid latitudes. I argue that the remarkably similar geologic settings of the NW Tempe Terra and Phlegra Montes candidate eskers (both within tectonic rift/graben valleys) suggests that geothermal heating, possibly with an additional component of viscous strain heating within the basal ice, was a prerequisite for basal melting under cold climate conditions. I then characterise the 2D and 3D morphometries of these candidate eskers, undertake comparisons with the morphometries of ancient putative eskers on Mars and eskers on Earth, and develop conceptual models for the dynamics of esker formation in NW Tempe Terra. Finally, I present a geomorphic map of Chukhung crater, Mars, which hosts esker-like sinuous ridges associated with viscous flow features and provides a case study of the ongoing challenges for esker identification on Mars

Planet Earth 2011

The failure of the UN climate change summit in Copenhagen in December 2009 to effectively reach a global agreement on emission reduction targets, led many within the developing world to view this as a reversal of the Kyoto Protocol and an attempt by the developed nations to shirk out of their responsibility for climate change. The issue of global warming has been at the top of the political agenda for a number of years and has become even more pressing with the rapid industrialization taking place in China and India. This book looks at the effects of climate change throughout different regions of the world and discusses to what extent cleantech and environmental initiatives such as the destruction of fluorinated greenhouse gases, biofuels, and the role of plant breeding and biotechnology. The book concludes with an insight into the socio-religious impact that global warming has, citing Christianity and Islam