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During the Last Glacial Maximum (LGM, ~ 23,000 to 19,000 years ago), the Patagonian Ice Sheet (PIS) covered the central chain of the Andes between ~ 38° S to 55° S. Existing paleoclimatic evidence – mostly derived from glacial landforms – suggests that maximum ice sheet expansions in the Southern and Northern Hemispheres were not synchronized. However, large uncertainties still exist in the timing of the onset of regional deglaciation as well as its major drivers. Here we present an ensemble of numerical simulations of the PIS during the LGM. Our aim is to assess the ability of paleoclimate model products to reproduce the range of atmospheric conditions needed to enable the ice sheet growth in concordance with geomorphological and geochronological evidence. The resulting ensemble is then used as a guideline for the evaluation of the PMIP3 and PMIP4 model performance across different sectors of the former PIS. Our analysis suggests a strong dependence of the PIS geometry on near-surface air temperature forcing. All the ensemble members driven by PMIP products are not able to reproduce the reconstructed ice cover in the northern part of Patagonia. In contrast, the modelled PIS tends to expand beyond its constrained boundaries in south-eastern Patagonia. We largely attribute these discrepancies between the model-based ice geometries and geological evidence to the low resolution of paleoclimate models. We conclude that among all tested climate forcings, the PMIP4 climate models INM-CM4-8 and MPI-ESM1-2-LR produce the necessary conditions for ice sheet growth across Patagonia. It should be kept in mind that this analysis is based only on the evaluation of the modelled ice sheet extent because geological constraints on the former ice thickness are still lacking. Nevertheless, our analysis suggests that a realistic PIS geometry at the LGM can be reproduced only if the complex topographic features of the Andes are properly resolved by climate models.

Numerical models predict that discharge from the polar ice sheets will become the largest contributor to sea-level rise over the coming centuries. However, the predicted amount of ice discharge and associated thinning depends on how well ice sheet models reproduce glaciological processes, such as ice flow in regions of large topographic relief, where ice flows around bedrock summits (i.e. nunataks) and through outlet glaciers. The ability of ice sheet models to capture long-term ice loss is best tested by comparing model simulations against geological data. A benchmark for such models is ice surface elevation change, which has been constrained empirically at nunataks and along margins of outlet glaciers using cosmogenic exposure dating. However, the usefulness of this approach in quantifying ice sheet thinning relies on how well such records represent changes in regional ice surface elevation. Here we examine how ice surface elevations respond to the presence of strong topographic relief that acts as an obstacle by modelling ice flow around and between idealised nunataks during periods of imposed ice sheet thinning. We find that, for realistic Antarctic conditions, a single nunatak can exert an impact on ice thickness over 20km away from its summit, with its most prominent effect being a local increase (decrease) of the ice surface elevation of hundreds of metres upstream (downstream) of the obstacle. A direct consequence of this differential surface response for cosmogenic exposure dating is a delay in the time of bedrock exposure upstream relative to downstream of a nunatak summit. A nunatak elongated transversely to ice flow is able to increase ice retention and therefore impose steeper ice surface gradients, while efficient ice drainage through outlet glaciers produces gentler gradients. Such differences, however, are not typically captured by continent-wide ice sheet models due to their coarse grid resolutions. Their inability to capture site-specific surface elevation changes appears to be a key reason for the observed mismatches between the timing of ice-free conditions from cosmogenic exposure dating and model simulations. We conclude that a model grid refinement over complex topography and information about sample position relative to ice flow near the nunatak are necessary to improve data-model comparisons of ice surface elevation and therefore the ability of models to simulate ice discharge in regions of large topographic relief.

Funding: This research has been supported by the Swedish Research Council (grant no. 2016-04422), the German Research Foundation (grant no. 1158-365737614), the US National Science Foundation (grant no. PLR-1542930), and the Norwegian Polar Institute/NARE (grant no. 2015/38/7/NK/ihs). Jorge Bernales has been supported by the MAGIC-DML project through DFG SPP 1158 (RO 4262/1-6). The article processing charges for this open-access publication were covered by Stockholm University. Studying the response of the Antarctic ice sheets during periods when climate conditions were similar to the present can provide important insights into current observed changes and help identify natural drivers of ice sheet retreat. In this context, the marine isotope substage 11c (MIS11c) interglacial offers a suitable scenario, given that during its later portion orbital parameters were close to our current interglacial. Ice core data indicate that warmer-than-present temperatures lasted for longer than during other interglacials. However, the response of the Antarctic ice sheets and their contribution to sea level rise remain unclear. We explore the dynamics of the Antarctic ice sheets during this period using a numerical ice sheet model forced by MIS11c climate conditions derived from climate model outputs scaled by three glaciological and one sedimentary proxy records of ice volume. Our results indicate that the East and West Antarctic ice sheets contributed 4.0–8.2 m to the MIS11c sea level rise. In the case of a West Antarctic Ice Sheet collapse, which is the most probable scenario according to far-field sea level reconstructions, the range is reduced to 6.7–8.2 m independently of the choices of external sea level forcing and millennial-scale climate variability. Within this latter range, the main source of uncertainty arises from the sensitivity of the East Antarctic Ice Sheet to a choice of initial ice sheet configuration. We found that the warmer regional climate signal captured by Antarctic ice cores during peak MIS11c is crucial to reproduce the contribution expected from Antarctica during the recorded global sea level highstand. This climate signal translates to a modest threshold of 0.4 °C oceanic warming at intermediate depths, which leads to a collapse of the West Antarctic Ice Sheet if sustained for at least 4000 years. Publisher PDF

Climate change in Siberia is currently receiving a lot of attention because large permafrost-covered areas could provide a strong positive feedback to global warming through the release of carbon that has been sequestered there on glacial–interglacial timescales. Geological evidence and climate model experiments show that the Siberian region also played an exceptional role during glacial periods. The region that is currently known for its harsh cold climate did not experience major glaciations during the last ice age, including its severest stages around the Last Glacial Maximum (LGM). On the contrary, it is thought that glacial summer temperatures were comparable to the present day. However, evidence of glaciation has been found for several older glacial periods. We combine LGM experiments from the second and third phases of the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) with sensitivity experiments using the Community Earth System Model (CESM). Together, these climate model experiments reveal that the intermodel spread in LGM summer temperatures in Siberia is much larger than in any other region of the globe and suggest that temperatures in Siberia are highly susceptible to changes in the imposed glacial boundary conditions, the included feedbacks and processes, and to the model physics of the different components of the climate model. We find that changes in the circumpolar atmospheric stationary wave pattern and associated northward heat transport drive strong local snow and vegetation feedbacks and that this combination explains the susceptibility of LGM summer temperatures in Siberia. This suggests that a small difference between two glacial periods in terms of climate, ice buildup or their respective evolution towards maximum glacial conditions can lead to strongly divergent summer temperatures in Siberia, allowing for the buildup of an ice sheet during some glacial periods, while during others, above-freezing summer temperatures preclude a multi-year snowpack from forming.

The shallow ice approximation (SIA) is commonly used in ice-sheet models to simplify the force balance equations within the ice. However, the SIA cannot adequately reproduce the dynamics of the fast flowing ice streams usually found at the margins of ice sheets. To overcome this limitation, recent studies have introduced heuristic hybrid combinations of the SIA and the shelfy stream approximation. Here, we implement four different hybrid schemes into a model of the Antarctic Ice Sheet in order to compare their performance under present-day conditions. For each scheme, the model is calibrated using an iterative technique to infer the spatial variability in basal sliding parameters. Model results are validated against topographic and velocity data. Our analysis shows that the iterative technique compensates for the differences between the schemes, producing similar ice-sheet configurations through quantitatively different results of the sliding coefficient calibration. Despite this we observe a robust agreement in the reconstructed patterns of basal sliding parameters. We exchange the calibrated sliding parameter distributions between the schemes to demonstrate that the results of the model calibration cannot be straightforwardly transferred to models based on different approximations of ice dynamics. However, easily adaptable calibration techniques for the potential distribution of basal sliding coefficients can be implemented into ice models to overcome such incompatibility, as shown in this study.

Lithospheric plates move over the low‐viscosity asthenosphere balancing several forces, which generate plate motions. We use a global 3‐D lithosphere‐asthenosphere model (SLIM3D) with visco‐elasto‐plastic rheology coupled to a spectral model of mantle flow at 300 km depth to quantify the influence of intra‐plate friction and asthenospheric viscosity on plate velocities. We account for the brittle‐ductile deformation at plate boundaries (yield stress) using a plate boundary friction coefficient to predict the present‐day plate motion and net rotation of the lithospheric plates. Previous modeling studies have suggested that small friction coefficients ( urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0001, yield stress urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0002 MPa) can lead to plate tectonics in models of mantle convection. Here we show that in order to match the observed present‐day plate motion and net rotation, the frictional parameter must be less than 0.05. We obtain a good fit with the magnitude and orientation of the observed plate velocities (NUVEL‐1A) in a no‐net‐rotation (NNR) reference frame with urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0003 and a minimum asthenosphere viscosity of urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0004 Pas to 1020 Pas. Our estimates of net rotation (NR) of the lithosphere suggest that amplitudes urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0005 ( urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0006/Ma), similar to most observation‐based estimates, can be obtained with asthenosphere viscosity cutoff values of urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0007 Pas to urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0008 Pas and friction coefficients urn:x-wiley:15252027:media:ggge21498:ggge21498-math-0009.

This study is aimed at a development of numerical method to model the dynamic geoid and the surface plate velocities induced by global mantle flow with the effect of strong lateral viscosity variations (LVV) in conjunction with the effects of selfgravitationand mantle compressibility. I employ the technique, which comprises the combination of the spherical harmonic method, the direct Godunov method used for solving the Stokes and Poisson equations in spherical harmonics with arbitrary boundary conditions, functions of density and radial viscosity, and the iterative method based on the principles suggested by Zhang and Christensen (1993) used for modeling the effect of LVV.The 3-D mantle viscosity model is based on the global seismic tomography model S20a converted to temperature variations. The maximum lateral viscosity contrast in the lithosphere-asthenosphere zone modeled reaches four orders of magnitude. It is found that the influence of LVV on the dynamic geoid is extremely significant: an alteration of the geoid figure due to LVV exceeds 45% of the maximum geoid undulations. The detailed analysis showed that the geoid is affected by both, strong LVV induced in theupper mantle and large-scale LVV induced in the lower mantle. According to the results of this study the separated effects of the upper- and lower-mantle LVV on the geoid figure are nearly additive with respect to the whole-mantle LVV and partly compensating with respect to each other. The mantle flows are strongly affected by LVV as well, especially by the long-wavelength viscosity variations in the lower mantle: global upwellings tend to intensify due to the effects of LVV, while downwellings become weaker. The alteration of the near-surface velocities reaches 30-40% in amplitude not only due to the LVV induced toroidal flow but also due to change in the spheroidal velocity component. I can conclude that the LVV presented in both, upper and lower mantle, play an important part in global modeling, therefore, an incorporation of 3-D viscosity structure into the next generation global dynamic models is a task of vital significance., Scientific Technical Report STR ; 08/08

After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2–56.9 ka) and 2 (23.2–16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka)., The Cryosphere, 10 (2), ISSN:1994-0416, ISSN:1994-0424

Global oppvarming skaper store endringer i karakteristikken av isbreer i verden og i Norge. Tilbaketrekningen til mange av Norges breer har økt dannelsen av glasiale sjøer. Bredemte sjøer skapes når isbreer eller morener blokkerer muligheten for at vannet kan drenere. Dersom de bredemte sjøene plutselig slipper ut vannet i de glasial sjøene, kalles dette for glacial lake outburst flood (GLOF) eller Jøkuhlaup. GLOFs har potensiale til å bli skape farlige hendelser og skape flom på mennesker, bygninger og infrastruktur nedenfor de bredemte sjøene. Tystigbreen i Stryn kommune, har to bredemte sjøer. Disse bredemte sjøene har blitt plutselig tømt flere ganger de siste tiårene. Hittil har det ikke ført til flom eller skade på bygninger eller infrastruktur. Selv om det ikke har vært flommer som følge av GLOF på Tystigbreen så kan det fremdeles skje i fremtiden. Denne masteroppgaven har som mål å undersøke hvor skadelig en GLOF kan potensielt være på de nedstrøms områdene i Videdalen, Sunndalen og Hjelledalen. Det blir undersøkt hvilke konsekvenser flere GLOF scenarioer kommer til å få. Studien vil diskutere og stille spørsmål ved hvor godt forberedt de nedstrømselvene; Videdøla, Sunndøla og Hjelledøla til å ta imot de vannmengdene som befinner seg i de bredemte sjøene. Metoden som skal brukes til å undersøke de ulike scenarioene er ved bruk HEC-RAS, et verktøy som brukes til å modellere vann i bekke- og elveløp. Resultatene av undersøkelsen viser at det er stor fare for flom dersom de bredemte sjøene utløser en GLOF der de bredemte sjøene tømmes hurtig. Modellene viser at både to timers GLOF hendelser, og GLOF med varighet på åtte timer vil gi signifikant økning i vannmengden i elveløpene. Store flater spesielt i Hjelledalen vil ta stor skade ved det verste scenarioet, som er to timers GLOF. Dette gjelder både fra Lagune 1 som drenerer til Videdøla og Lagune 2 som drenerer til Sunndøla. Modellene viser at infrastruktur, bygninger, jordbruksområder, og potensielt menneskeliv kan gå tapt dersom en stor GLOF finner sted. Fremtidige utsikter er uklare, og det er uvisst om de scenarioene som er modellert i denne oppgaven noen gang vil finne sted. Det er derimot viktig å vite hvordan et potensielt ødeleggende GLOF scenario kan se ut, og hvordan det vil påvirke områdene nedstrøms. Global warming is causing changes in the glacier environments all around the world. As well as in many other mountainous regions, the retreat of glaciers in Norway has promoted the formation of glacial lakes that often become hazardous and cause floods in downstream valleys. This happens in case glacial lakes get dammed by glaciers or moraines and suddenly release water through events that are called glacial lake outburst floods (GLOFs) or jøkullaups. Tystigbreen in the Stryn municipality in western Norway has four glacial lakes. Of these four, two lakes are known to have suddenly drain on multiple occasions in the last decades. Although documented GLOFs in this area have not been on a scale that could have caused floods or harm in the valleys downstream, the behavior and hazardous activity of the two glacial lakes may well change in the future, with the glacier thinning and retreating at an unprecedented rate. This thesis aims to investigate the potential of GLOFs from Tystigbreen to create floods in the downstream valleys, Videdalen, Sunndalen and Hjelledalen. Here I investigate a range of potential scenarios for GLOF speed and geography, estimating the consequences they will have on the downstream valleys and communities. This study discusses whether the downstream rivers can accommodate large future GLOFs without overspilling and flooding settlements and infrastructure. The means to investigate the impacts of GLOFs on valleys is through hydrological simulations with HEC-RAS, a software used to model the flow of water in creeks and rivers. The results of these investigations show that there is a big potential for floods in the valleys connected to the glacial lake drainage paths, if glacial lakes drain rapidly. GLOFs with a duration of eight hours and especially two hours have a potential to significantly increase water levels in rivers and flood large areas in the main valley, Hjelledalen. In addition, rapid drainage of both glacial lakes will cause large floods in the upper valleys - Videdøla and Sunndøla in the worst-case scenarios. My model simulations show that infrastructure, buildings and agricultural land will be heavily damaged as a result of such GLOFs. Future projections for GLOFs are still uncertain due to limitations in our understanding of their mechanisms. It is therefore unknown to which extent the scenarios modeled in this thesis are to occur. However, it is important to understand how future damaging GLOF scenarios might look like and how to prepare valleys downstream for such events.

De siste tiårene har vært preget av en økning i intensitet og hyppighet av kraftig regn og ekstrem smelting av isbreer på grunn av klimaendringene. Det har ført til økt sårbarhet for flom i regioner langs elveløp som kommer fra isbreer. Jostedalsbreen nasjonalpark er en av regionene med høyest årlig nedbør i Norge og er hjem til den største fastlands isbreen i Europa. Jostedalen er på grunn av dalens historie med flommer og mange turist attraksjoner blitt overvåket siden den siste store flommen som førte til store ødeleggelser i dalen den 15 August 1979. Dalen har opplevd mange forandringer og utviklet seg mye gjennom årene i et forsøk på å redusere sårbarheten mot flommer og medfølgende erosjon. Denne studien estimerer flom risiko i fremtiden og mulige påvirkninger på samfunnet sammenlignet med den historiske hendelsen i 1979. Det overordnede målet er å rekonstruere historien og påvirkningene til den ødeleggende flommen i Jostedalen og å vurdere i hvilken grad statlig respons og tiltak etter hendelsen beskytter lokalsamfunn fra fremtidige katastrofer. Dessuten presenterer denne studien modell-baserte projeksjoner av flom utsettelse og sårbarhet i Hjelledalen, en dal på andre siden (nord) av nasjonalparken, for å analysere forskjeller i eksisterende beskyttende tiltak og deres effekter. Regionens sensitivitet til flommer av mindre og større intensitet (median, 10-, 20-, 50-, 100- og 200-års flommer) blir analysert for å kartlegge områder som er i fare under forskjellige flom-scenarioer og for å identifisere høy-risiko soner. Eksperimentene i denne oppgaven er basert på hydrologisk modellering med høy oppløsning i HEC-RAS (Hydrologic Engineering Centers River Analysis System) med topografisk info fra den Norske Digitale Høydemodellen og avrennings data fra målestasjoner og den Regionale Flom Frekvens Analysen (RFFA). Simulasjonene viser at de fleste områdene langs Jostedøla er i fare for oversvømmelser allerede under mindre flommer (median, 10- og 20-års flom), riktignok med lav samfunnspåvirkning. Med økende flom intensitet øker flomskadene drastisk og viser høy vannstand i de fleste bebodde områdene i dalen. Analysen av effekten av tilpasnings tiltak mot flom under forskjellige scenarioer viser at tiltakene som har blitt gjort i Myklemyr er veldig effektive under alle scenarioer mens betraktelig oppdatering og vedlikehold er nødvendig i Hesjevoll, Sperle, Fossen, Alsmo og Gaupne for å motstå fremtidige flom hendelser. Flere områder i Hjelledalen, spesielt Folven og Hjelle, står i stor fare for oversvømmelser fra høy-intensitets flommer. Imidlertid demonstrerer studien at ytterligere beskyttende installasjoner i utsatte områder langs elva vil øke resistensen mot flom hendelser. The last few decades have been marked by increasing intensity and frequency of heavy rainfall and extreme glacier melt events due to climate change. Through this development, regions dependent on glacier-fed river systems have become more vulnerable to repeated floods. The Jostedalsbreen National Park is in the region with highest annual precipitation in Norway and is home to the largest mainland glacier in Europe. Due to its history of major floods and a key tourism attraction, the Jostedalen valley has been monitored closely since the largest flood in the documented history of the region on August 15, 1979. The valley has experienced many modifications and developments over the years in attempt to reduce its vulnerability to floods and flood-related erosion. Based on the evidence of the flood impacts on local communities, this study has been designed to estimate future flood risks and their possible impacts on the valley compared to the historical event of 1979. The overarching objective of this study is to reconstruct the history and impacts of the tragic past flood in Jostedalen and assess to which extent the governmental response to the past hazard protects local people from upcoming future disasters. Furthermore, the study presents model-based projections of flood exposure and vulnerability in the less documented Hjelledalen valley on the northern side of the national park to emphasize differences in the existing protective measures and their impacts. As part of this analysis, the region’s sensitivity to minor versus high-intensity floods (median, 10-, 20-, 50-, 100- and 200-year floods) were tested to map and identify areas at risk under different flood. The experiments presented in this thesis are based on the high-resolution hydrological modelling using HEC-RAS (Hydrologic Engineering Centre River Analysis System) with topographic and runoff forcings from the detailed Digital Terrain Model and water flux data from gauging stations and the Regional Flood Frequency Analysis (RFFA). The simulations show that most areas along the Jostedøla river are at risk of flooding even during minor floods (median, 10- and 20-year floods), albeit with low societal impacts. As the magnitudes of floods grow, the extents of flood damage increase drastically, showing high water levels throughout most of the populated sections of the valley. When assessing the effect of flood mitigation measures under future flood scenarios, this study has found that mitigation measures at Myklemyr are very effective even under high-magnitude floods, while the existing installations at Hesjevoll, Sperle, Fossen, Alsmo and low-lying parts of Gaupne need extensive upgrades and maintenance. The Hjelledalen valley appears to be at a very high risk of flooding from high magnitude floods, especially in the highly touristic areas at Folva and Hjelle. However, the study demonstrates that introduction of additional protective installations along vulnerable parts of the river will significantly increase the resistive capacity of the valley.

Isbreer og deres miljø er veldig sårbare til effekene av klimaendringene. Etter en kort periode på 1990-tallet hvor isbreene vokste har breene på Vestlandet i Norge trukket seg tilbake i en alarmerende hastighet. Smeltingen av isbreer har påvirker samfunn miljøet i dalene nedenfor da det har en effekt på vanntilførsel, elveløp, frekvensen og mengden natur katastrofer. Dessuten påvirker det de som er avhengige av smeltevann for vannkraft, jordbruk og friluftsliv. I tillegg til næringslivet har tibaketrekkingen av isbreer … konsekvenser for lokal identitet og kultur. At klimaendringene vil fortsette å påvirke det samfunnet og naturen er anerkjent i størrste annlennhet. Derfor er det essensielt å identifisere variablene som former samfunnets og naturens klimasårbarhet. Basert på tidligere arbeider om sårbarhet ble et Lokalisert Sosialt Sårbarhets Rammeverk (LSVF engelsk) utviklet og anvendt i denne oppgaven. Rammeverket ble brukt for å identifisere sårbarheten og tilpasnings kapasiteten til lokale aktører i seks kommuner i Vestland Fylke som blir påvirket av bresmeltingen. Hensikten med LSVF er å undersøke de fire faktorene som driver sårbarhet: miljøpåvirkningen av bresmeltingen, sosiale oppfatninger, økonomi og levebrød, og muligheter og barrierer for tilpasnings kapasiteten. Denne studien har identifisert flere faktorer som driver klimasårbarheten, inkludert politisk uvilje, mangel på informasjon og kunnskap og limiterte ressurser. Likevel var det også klare eksempler på lokale aktører som brukte tilpasnings strategier for å øke motstandsdykigheten mot klimaendrigene. Den foreliggende studien tar for seg steds rollen ved å adressere klimasårbaheten for å bygge opp motstandsdyktighet. Mens bresmeltingen er en trussel for identiteten og levebrøded i de rammede kommunene, kan den også bidra til å mobilisere aktører til å beskytte samfunner fra effektene av klimaendringene. Dette understreker viktigheten og kompleksiteten av sted når det kommer til sårbarheten til kommunale samfunn som opplever tap av naturmiljøet. Glacier environments are highly susceptible to the effects of climate change. After glacial advancement during the 1990s, glaciers in Western Norway have retreated at an alarming rate. Glacier loss has an impact on downstream communities and the environment due to changes in water supply, flow regime, and the frequency and magnitude of natural hazards. Subsequently, it also affects those who rely on melt water for hydropower, agriculture, and recreation. In addition to impacting business operations, glacier retreat has profound implications on local identity and culture. As it is widely acknowledged that climate change will continue to have an influence on social and natural systems, it is critical to identify the variables that shape vulnerability. Building from previous works on vulnerability, this thesis creates and applies the Localized Social Vulnerability Framework (LSVF) to identify vulnerabilities and adaptive capacities of local actors experiencing glacial change in six municipalities within Western Norway. The purpose of the LSVF is to examine the four factors driving vulnerability: the environmental impact of glacier change, perceptions, economies and livelihoods, and bridges and barriers to adaptive capacities. This study identifies several factors driving climate vulnerability, including political unwillingness, information and knowledge gaps, and resource limitations. However, there are also clear examples of local actors using adaptive capacities to enhance resilience. This study emphasizes the role of place in addressing vulnerability to build climate resilience. Specifically, while glacier melt threatens identity and livelihood, it also has the capacity to mobilize actors to protect their communities from climate impacts. This suggests the importance and complexity of place when investigating the vulnerability of communities experiencing environmental loss.

Den observerte tilbaketrekningen av isbreer i global skala fremmer dannelsen og veksten av bresjøer i nylig isfrie områder. På Fastlands-Norge fører denne prosessen til økningen i Glacial Lake Outburst Floods (GLOFs), som utgjør en betydelig trussel mot mennesker og infrastruktur nedstrøms. Videre blir mange bresjøer brukt som reservoarer for vannkraftproduksjon og representerer dermed en viktig energikilde. Dette understreker behovet for kontinuerlig overvåking av livssyklusene til bresjøene. Fjernmåling er for tiden den mest effektive teknikken for å spore endringer i bresjøer, forstå hvordan de påvirkes av klimaendringer og observere innsjøer som er utsatt for GLOF. Nylige fremskritt innen maskinlæringsteknikker har gitt nye muligheter for å automatisere kartlegging av bresjøer over store områder. Denne studien presenterer for første gang over hele Norge rekonstruksjon av endringer i bresjøer gjennom de siste tre tiårene ved hjelp av maskinlæringsalgoritmer og langsiktige satellittobservasjoner. Den sammenligner ytelsen til to klassifiseringsmetoder – maksimal sannsynlighetsklassifisering (MLC) og støttevektormaskin (SVM) - for å skissere bresjøer og studere deres utvikling ved hjelp av Landsat-serien og Sentinel-2-bilder. Denne studien tydeliggjør fordelene og ulempene ved hver klassifiseringsmetode og satellittprodukt gjennom prismen til bresjøprosesser som foregår over forskjellige tidsmessige og romlige skalaer - fra dannelse av innsjø, vekst og dissosiasjon fra de proksimale breene til ettervirkningen av raske GLOF-hendelser. Basert på denne analysen konkluderer jeg med at deteksjonsferdighetene til overvåkede klassifiseringsmetoder i stor grad avhenger av kvaliteten på satellittbilder og nøye utvalg av treningsprøver. Noen av faktorene som påvirker klassifiseringsresultatene negativt og kan føre til feilklassifisering er ugunstige værforhold som sky, snø og isdekke, bildeforstyrrelser gjennom atmosfæriske korreksjoner og skygger i skråninger. Uavhengig av høyere romlig og tidsmessig oppløsning har Sentinel-bilder ikke avdekket betydelige fordeler i forhold til Landsat, men har vist et potensial for deres komplementære bruk i videre observasjoner av bresjøer i fremtiden. SVM har helt klart bedre ytelse enn MLC, men SVM er vanskelig å bruke over store romlige skalaer, i det minste i den formen det for øyeblikket er implementert på i ENVI. The observed retreat of mountain glaciers on a global scale promotes the formation and growth of glacial lakes across newly exposed ice-free areas. In mainland Norway, this process drives the rise in glacial lake outburst floods (GLOFs), posing a considerable threat to people and infrastructure downstream. Moreover, many glacial lakes are used as reservoirs for hydropower production and thus represent an important energy source, emphasizing the need for continuous monitoring of glacial lake life cycles. Remote sensing is currently the most efficient technique for tracking changes in glacial lakes, understanding their responses to climate change and observing lakes prone to GLOFs. Recent advances in machine learning techniques have presented new opportunities to automatize glacial lake mapping over large areas. For the first time, this study presents a Norway-wide reconstruction of glacial lake changes through the last three decades using machine learning algorithms and long-term satellite observations. It contrasts the performance of two classification methods - maximum likelihood classification (MLC) and support vector machine (SVM) - to outline glacial lakes and study their evolution using the Landsat series and Sentinel-2 images. This study zooms into the pros and cons of each classification method and satellite product through the prism of glacial lake processes occurring over disparate temporal and spatial scales - from lake formation, growth and dissociation from the proximal glaciers to the aftermath of rapid GLOF events. Based on this analysis, I conclude that the recognition skills of supervised classification methods largely depend on the quality of satellite images and careful selection of training samples. Some of the factors that adversely affect the classification results are unfavourable weather conditions such as cloud, snow and ice cover, image disturbances through atmospheric corrections and shadows on slopes that lead to misclassifications. Regardless of higher spatial and temporal resolution, Sentinel imagery has not revealed significant advantages over Landsat but has shown a potential for their complementary use to continue glacial lake observations in the future. The performance of SVM is clearly superior to MLC, but it is difficult to use over large spatial scales, at least in the form it is currently implemented in ENVI.