Glaciers respond to local climate changes making them important indicators of regional climate change. The North Cascades region of Washington is the most glaciated region in the lower-48 states with approximately 25% of all glaciers and 40% of the total ice-covered area. While there are many on-going investigations of specific glaciers, little research has addressed the entire glacier cover of the region. A reference inventory of glaciers was derived from a comparison of two different inventories dating to about 1958. The different inventories agree within 93% of total number of glaciers and 94% of total ice-covered area. To quantify glacier change over the past century aerial photographs, topographic maps, and geologic maps were used. In ~1900 total area was about 533.89 ± 22.77 km2 and by 2009 the area was reduced by -56% ± 3% to 236.20 ± 12.60 km2. Most of that change occurred in the first half of the 20th century, between 1900 and 1958, -245.59 ± 25.97 km2 (-46% ± 5%) was lost, followed by a period of stability/growth in mid-century (-1% ± 3% from 1958-1990) then decline since the 1990s (-9% ± 3% from 1990-2009). The century-scale loss is associated with increasing regional temperatures warming in winter and summer; precipitation shows no trend. On a decadal time scale winter precipitation and winter and summer temperatures are important factors correlated with area loss. Topographically, smaller glaciers at lower elevations with steeper slopes and higher mean insolation exhibited greater loss than higher, gentler more shaded glaciers.

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La venue des satellites a permis l’apport de données cruciales sur l’évolution récente de la dynamique des calottes glaciaires modernes. Cependant, les données satellitaires ne fournissent pas une vue d’ensemble (échelle centenaire à millénaire) qui reflète l’évolution à long terme du climat. Des données sur l’évolution à long terme des calottes glaciaires peuvent toutefois être obtenues en analysant la géomorphologie de systèmes déglacés tels que les fjords et les auges glaciaires. Les fjords et les auges glaciaires sont des systèmes géomorphologiques communs des côtes et des plateaux continentaux des hautes latitudes. Ces systèmes incarnent l’expression la plus évidente de la puissance érosive des glaciers modernes et anciens. L’étude des systèmes de fjords et d’auges glaciaires a le potentiel de fournir des connaissances sur la dynamique de retrait d’une calotte glaciaire passant de marges marines à terrestres lors d’un réchauffement climatique; un contexte semblable aux calottes glaciaires modernes de l’Antarctique et du Groenland. Ici, des données de bathymétrie à haute résolution et de réflexion sismostratigraphique, ainsi que des cartes géomorphologiques, sont utilisées pour reconstituer l’histoire paléoglaciaire des fjords et des auges du nord-est de l’Ile de Baffin afin de fournir un analogue paléoglaciologique aux systèmes glaciaires modernes. Les données géophysiques compilées dans ce secteur montrent que durant le Stade isotopique marin 2 (MIS-2; 29 – 14 ka BP), l’Inlandsis laurentidien s’étendait jusqu’à la limite du plateau continental, au large des limites glaciaires précédemment proposées. La marge d’Inlandsis laurentidien s’est ensuite retirée de manière épisodique vers l’ouest pendant la déglaciation du Foxe tardif et de l’Holocène. L’analyse géomorphologique du plateau continental du nord-est de l’Ile de Baffin a aussi permis d’identifier un changement de direction dans l’écoulement du courant de glace de Sam Ford qui se serait produit durant la période Pliocène-Pléistocène. Ce changement de direction serait dû à l’érosion de l’Auge glaciaire marginale d’Hecla & Griper. Les données démontrent que les conditions d’écoulement rapide dans le courant de glace de Scott ont migré vers l’amont du courant, suivant l’auge glaciaire marginale jusqu’à capturer le bassin de drainage du courant de glace voisin (courant de Sam Ford), provoquant ainsi l’arrêt des conditions d’écoulement rapide dans l’Auge de Sam Ford. Une approche de géosystème glaciaire a ensuite été utilisée pour analyser le retrait des marges de l’Inlandsis laurentidien dans les fjords lors de la déglaciation. La géomorphologie et les assemblages de formes de terrain préservés sur le fond marin depuis la déglaciation révèlent que : 1) des écoulements rapides de la glace, par le biais des courants de glace, ont probablement été actifs jusqu’au stade tardif de la déglaciation; 2) les hauts bathymétriques ont agi comme des points d’ancrage et donc comme des obstacles à l’écoulement rapide des courants de glace; 3) le substrat rocheux cristallin n’a pas agi comme point d’adhésivité contrairement à ce qui a été suggéré pour d’autres paléocourants de glace en Amérique du Nord; 4) les facteurs favorisant la stabilité de la marge glaciaire comprennent la bathymétrie en forme d’entonnoir, les courbes dans le tracé des fjords et les facteurs climatiques; 5) les glaciers émissaires de l’Inlandsis laurentidien ont été capables de stabiliser leurs marges sur des pentes rétrogrades et dans des bassins profonds (>800 m); et 6) durant la déglaciation, la sédimentation dans les fjords a été dominée par des écoulements gravitaires sur le fond (hyperpycnaux). Enfin, la cartographie des différentes entités géomorphologiques a permis de produire une série de 50 cartes des formes glaciaires présentes sur le fond marin des fjords et des auges du plateau continental nord-est de l’Ile de Baffin, où 24 types de formes de terrain liés aux environnements sous-glaciaires, en marge de la glace (juxtaglaciaires) et paraglaciaires ont été systématiquement cartographiées (>55 000 entités). / Fjords and troughs are common geomorphological systems on high-latitude coasts and continental shelves where they embody the most obvious expression of the erosional power of past and present-day glaciers. While recent satellite data have brought crucial insights on how ice sheet and glacier dynamics have evolved on a decadal timescale, they do not provide a long-term overview (centennial to millennial scale) that is consequent with long-term evolution of climate. Centennial-to-millennial data on long-term evolution of ice sheets can, however, be obtained by investigating the geomorphology of deglaciated systems such as fjords and crossshelf troughs. Fjords and cross-shelf troughs of deglaciated high-latitude coasts and continental shelves have the potential to provide knowledge on deglacial dynamics from a complete marine-terminating ice sheet to a full terrestrial-based ice sheet. Here, swath bathymetry and seismic reflection data, together with geomorphological maps, are used to investigate palaeo-glacial history of the northeastern Baffin Island fjords and continental shelf. We present marine geophysical evidence that during the marine isotope stage 2 (MIS-2; 29 – 14 ka BP), the Laurentide Ice Sheet (LIS) extended to the edge of the continental shelf, seaward of the previously proposed glacial limits. The LIS subsequently retreated episodically westward during the Late-Foxe and Holocene deglaciation. A glacial landsystem approach has then been used to investigate ice-sheet retreat through the northeastern Baffin Island fjords. The geomorphology and landforms-assemblages preserved since deglaciation on the seafloor reveal that: 1) ice streaming was probably active until the late stage of deglaciation; 2) bathymetric highs acted as sticky spots and therefore as obstacles to fast ice-flow; 3) crystalline bedrock did not act as sticky spot as suggested for other palaeo-ice streams in North America; 4) factors favoring ice-margin stability include funnel-shaped bathymetry, bends and climate forcing; 5) tidewater-glaciers can achieve icemargin stability on retrograde slopes and in deep (>800 m) basins; and 6) during deglaciation, sedimentation in fjords has been dominated by gravity-driven flows. The geomorphological analysis also enabled the identification of the flow-switch of an ice stream that occurred during the Pliocene-Pleistocene on the shelf, through glacial erosion and overdeepening of marginal troughs, i.e., deep parallel-to-coast bedrock moats located upice of cross-shelf troughs. Shelf geomorphology imaged by high-resolution swath bathymetry and seismostratigraphic data in the troughs provides evidence for the extension of ice streams from Scott and Hecla & Griper troughs towards the interior of the Laurentide Ice Sheet. This up-ice extension of the Scott ice stream along a marginal trough and into the Sam Ford icedrainage basin led to the capture the Sam Ford ice stream, causing a flow-switch and a shutdown of ice streaming in Sam Ford Trough. Finally, geomorphological mapping led to the production of a series of 50 maps of submarine glacial landforms in the fjords and cross-shelf troughs of northeastern Baffin Island, in which 24 types of landform associated with subglacial, ice-marginal or paraglacial environments were systematically mapped (>55 000 individual landforms).

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Alors que depuis un peu plus de 2000 ans, le niveau moyen de la mer a peu varié, ce niveau s'est élevé d'environ 2 mm/an au cours du 20ème siècle. Cette hausse soudaine est attribuée au réchauffement climatique d'origine anthropique enregistré depuis plusieurs décennies. Depuis une douzaine d'années, on mesure de façon globale et précise les variations du niveau de la mer grâce aux satellites altimétriques Topex/Poseidon et Jason-1. Ces observations indiquent une hausse moyenne globale d'environ 3 mm/an depuis 1993, valeur sensiblement plus grande que celle des dernières décennies. <br />Diverses observations disponibles depuis peu nous ont permis de quantifier les contributions des divers facteurs climatiques à la hausse observée du niveau de la mer : expansion thermique de la mer due au réchauffement des océans, fonte des glaciers de montagne et des calottes polaires, apport d'eau des réservoirs continentaux. Le bilan de ces nouvelles observations nous permet d'expliquer en partie la hausse observée du niveau de la mer. En particulier, nous montrons que l'expansion thermique des océans n'explique que 25% de la hausse séculaire du niveau de la mer enregistrée par les marégraphes depuis 50 ans, tandis qu'elle contribue à la hauteur de 50% à la montée du niveau marin au cours de la dernière décennie. Parallèlement, des études récentes estiment que la fonte des glaciers de montagne et des calottes polaires pourraient contribuer pour environ 1 mm/an à l'élévation du niveau de la mer au cours de la dernière décennie. <br />De plus, la forte variabilité régionale des vitesses d'évolution du niveau de la mer révélée par les observations altimétriques de Topex/Poseidon résulte en grande partie de l'expansion thermique. Nous mettons également en lumière l'importante variabilité spatio-temporelle décennale de l'expansion thermique des océans au cours des 50 dernières années, qui semble dominée par les fluctuations naturelles du climat. De plus nous posons pour la première fois la question du lien qui existe entre les fluctuations décennales de l'expansion thermique des océans et la contribution climatique des eaux continentales au niveau de la mer. Enfin, une analyse préliminaire des observations gravimétriques de la mission spatiale GRACE sur les océans nous permet d'évaluer les variations saisonnières du niveau moyen de la mer liées aux variations du bilan de masse d'eau des océans.

Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. / Graduation date: 2013

La transition entre le dernier épisode glaciaire et l'actuel interglaciaire (de 20 000 à 10 000 ans avant le présent) est caractérisée par de courtes et abruptes réorganisations du climat à différentes échelles. Sur l'Altiplano bolivien des paléolacs géants se développent et disparaissent en moins de 2000 ans. La dynamique des glaciers étant contrôlée par le climat, les dépôts laissés par les anciens glaciers constituent une des rares archives climatiques disponibles sur ce haut plateau aride. La méthode des âges d'exposition permet de reconstituer l'histoire des anciens glaciers. Cette thèse apporte de nouveaux outils méthodologiques pour le calcul de ces âges. Elle présente également de nouveaux âges couplés à des reconstructions climatiques. Ces résultats indiquent que la formation des paléolacs est concomitante de refroidissements moyens compris entre 2.5 et 4.5 C par rapport au présent et d'un apport accru d'humidité depuis l'Est, franchissant la Cordillère Orientale bolivienne / The transition between the last glacial maximum and the actual interstadial (from 20 to 12 ka before present) is characterized by short and abrupt climate reorganizations at different scales. Over the Bolivian Altiplano, giant palaeo-lakes wax and wane within 2000 years. The glaciers dynamics is controlled by the climate, making the deposits from the former glaciers one of the few climatic archives available on this arid plateau. The exposure age method enables to reconstruct the history of former glaciers. This thesis brings new tools for the calculation of these ages. It also presents new ages coupled with palaeo-climate reconstructions. These results indicates that the palaeo-lake formations are concomitant with mean coolings of 2.5 to 4.2°C compared to present and with an enhanced moist transport from the East, crossing the Bolivian Oriental Cordillera

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-11-07T16:12:29Z No. of bitstreams: 1 Tese - Contribuição das queimadas na América do Sul para o derretimento das geleiras Andinas.pdf: 12013598 bytes, checksum: b9ec5b579fb35328075809a39c2dbffb (MD5) / Made available in DSpace on 2017-11-07T16:12:29Z (GMT). No. of bitstreams: 1 Tese - Contribuição das queimadas na América do Sul para o derretimento das geleiras Andinas.pdf: 12013598 bytes, checksum: b9ec5b579fb35328075809a39c2dbffb (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / O período de maior ocorrência das queimadas na América do Sul, de agosto à outubro, coincide com mudanças sazonais na circulação atmosférica que tornam favoráveis o transporte e a deposição de black carbon sobre as geleiras Andinas. Com o intuito de avaliar o potencial impacto do black carbon emitido pelas queimadas na bacia Amazônica sobre a massa de gelo dessas geleiras, foram modeladas a emissão de BC, o seu transporte e deposição sobre a geleira Zongo, as mudanças no albedo e a perda de massa de gelo/neve em 2 anos críticos, 2007 e 2010. Os valores de emissão para estes anos na bacia Amazônica foram de 34 e 26 Gg para os picos em setembro, e 51 e 76 Gg anuais. Estes valores foram utilizados para a modelagem da emissão, transporte, deposição e perda de massa de gelo devido ao black carbon. A redução no albedo devido as queimadas foi de 2,5-5%, o que resultou em uma perda de massa de gelo/neve de 3,0-6,5 kg/m² ao ano, equivalente a um incremento de 2-4,5% na perda de massa de gelo/neve anual. Esta perda de massa de gelo devido as queimadas pode ser observada na descarga da geleira nos meses de agosto e setembro. O recuo da frente da geleira apresentou uma relação direta com o desmatamento e o número de queimadas na América do sul. Períodos com maiores taxas de recuo coincidiram com os anos de maiores eventos de queimada e desmatamento. / The period of greatest occurrence of fires in South America, from August to October, coincides with seasonal changes in atmospheric circulation that favor the transportation and deposition of black carbon on the Andean glaciers. In order to evaluate the potential impact of the black carbon emitted by the fires in the Amazon over these glaciers, we modeled the emission of BC, its transport and deposition on the Zongo glacier, the change in glacier albedo and the resulting Ice / snow mass loss, during 2 critical years, 2007 and 2010. The emission values for these years in the Amazon basin were 34 and 26 Gg for the peaks in September, and 51 and 76 Gg annual. These values were used for modeling the emission, transport, deposition and loss of ice/snow due to black carbon. The estimated albedo reduction were 2.5-5%, which resulted in a loss of ice / snow mass of 3.0-6.5 kg / m² per year, equivalent to an increase of 2-4,5% annual ice / snow mass loss. The estimated ice/snow loss due to Amazon fire emission can be observed in the Zongo's discharge during august and september. The retreat of the front of the glacier presented a direct relation with the deforestation and the number of fires events in South America. Periods with the highest retreat rates coincided with the years of major events of burning and deforestation.