Feasibility Study for the Application of Synthetic Aperture Radar for Coastal Erosion Rate Quantification Across the Arctic

The applicability of optical satellite data to quantify coastal erosion across the Arctic is limited due to frequent cloud cover. Synthetic Aperture Radar (SAR) may provide an alternative. The interpretation of SAR data for coastal erosion monitoring in Arctic regions is, however, challenging due to issues of viewing geometry, ambiguities in scattering behavior and inconsistencies in acquisition strategies. In order to assess SAR applicability, we have investigated data acquired at three different wavelengths (X-, C-, L-band; TerraSAR-X, Sentinel-1, ALOS PALSAR 1/2). In a first step we developed a pre-processing workflow which considers viewing geometry issues (shoreline orientation, incidence angle relationships with respect to different landcover types). We distinguish between areas with foreshortening along cliffs facing the sensor, radar shadow along cliffs facing away and traditional land-water boundary discrimination. Results are compared to retrievals from Landsat trends. Four regions which feature high erosion rates have been selected. All three wavelengths have been investigated for Kay Point (Canadian Beaufort Sea Coast). C- and L-band have been studied at all sites, including also Herschel Island (Canadian Beaufort Sea Coast), Varandai (Barents Sea Coast, Russia), and Bykovsky Peninsula (Laptev Sea coast, Russia). Erosion rates have been derived for a 1-year period (2017–2018) and in case of L-band also over 11 years (2007–2018). Results indicate applicability of all wavelengths, but acquisitions need to be selected with care to deal with potential ambiguities in scattering behavior. Furthermore, incidence angle dependencies need to be considered for discrimination of the land-water boundary in case of L- and C-band. However, L-band has the lowest sensitivity to wave action and relevant future missions are expected to be of value for coastal erosion monitoring. The utilization of trends derived from Landsat is also promising for efficient long-term trend retrieval. The high spatial resolution of TerraSAR-X staring spot light mode (<1 m) also allows the use of radar shadow for cliff-top monitoring in all seasons. Derived retreat rates agree with rates available from other data sources, but the applicability for automatic retrieval is partially limited. The derived rates suggest an increase of erosion at all four sites in recent years, but uncertainties are also high

Degrading permafrost river catchments and their impact on Arctic Ocean nearshore processes

Arctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments. These changes may affect coastal processes, food web dynamics and marine resources on which many traditional ways of life rely. Here, we examine how future projected increases in runoff and permafrost thaw from two permafrost-dominated Siberian watersheds - the Kolyma and Lena, may alter carbon turnover rates and OC distributions through river networks. We demonstrate that the unique composition of terrestrial permafrost-derived OC can cause significant increases to aquatic carbon degradation rates (20 to 60% faster rates with 1% permafrost OC). We compile results on aquatic OC degradation and examine how strengthening Arctic hydrological cycles may increase the connectivity between terrestrial landscapes and receiving nearshore ecosystems, with potential ramifications for coastal carbon budgets and ecosystem structure. To address the future challenges Arctic coastal communities will face, we argue that it will become essential to consider how nearshore ecosystems will respond to changing coastal inputs and identify how these may affect the resiliency and availability of essential food resources

Rapid Fluvio-Thermal Erosion of a Yedoma Permafrost Cliff in the Lena River Delta

The degradation of ice-rich permafrost deposits has the potential to release large amounts of previously freeze-locked carbon (C) and nitrogen (N) with local implications, such as affecting riverine and near-shore ecosystems, but also global impacts such as the release of greenhouse gases into the atmosphere. Here, we study the rapid erosion of the up to 27.7 m high and 1,660 m long Sobo-Sise yedoma cliff in the Lena River Delta using a remote sensing-based time-series analysis covering 53 years and calculate the mean annual sediment as well as C and N release into the Lena River. We find that the Sobo-Sise yedoma cliff, which exposes ice-rich late Pleistocene to Holocene deposits, had a mean long-term (1965–2018) erosion rate of 9.1 m yr–1 with locally and temporally varying rates of up to 22.3 m yr–1. These rates are among the highest measured erosion rates for permafrost coastal and river shoreline stretches. The fluvio-thermal erosion led to the release of substantial amounts of C (soil organic carbon and dissolved organic carbon) and N to the river system. On average, currently at least 5.2 × 106 kg organic C and 0.4 × 106 kg N were eroded annually (2015–2018) into the Lena River. The observed sediment and organic matter erosion was persistent over the observation period also due to the specific configuration of river flow direction and cliff shore orientation. Our observations highlight the importance to further study rapid fluvio-thermal erosion processes in the permafrost region, also because our study shows increasing erosion rates at Sobo-Sise Cliff in the most recent investigated time periods. The organic C and N transport from land to river and eventually to the Arctic Ocean from this and similar settings may have severe implications on the biogeochemistry and ecology of the near-shore zone of the Laptev Sea as well as for turnover and rapid release of old C and N to the atmosphere

Particulate organic matter in the Lena River and its Delta: From the permafrost catchment to the Arctic Ocean

Rapid Arctic warming accelerates permafrost thaw, causing an additional release of terrestrial organic matter (OM) into rivers, and ultimately, after transport via deltas and estuaries, to the Arctic Ocean nearshore. The majority of our understanding of nearshore OM dynamics and fate has been developed from freshwater rivers, despite the likely impact of highly dynamic estuarine and deltaic environments on transformation, storage, and age of OM delivered to coastal waters. Here, we studied OM dynamics within the Lena River main stem and Lena Delta along an approximately ∼1600 km long transect from Yakutsk, downstream to the delta disembogue into the Laptev Sea. We measured particulate organic carbon (POC), total suspended matter (TSM), and carbon isotopes (δ13C and ∆14C) in POC to compare riverine and deltaic OM composition and changes in OM source and fate during transport offshore. We found that TSM and POC concentrations decreased by 55 and 70 %, respectively, during transit from the main stem to the delta and Arctic Ocean. We found deltaic POC to be strongly depleted in 13C relative to fluvial POC, indicating a significant phytoplankton contribution to deltaic POC (∼68 ±6 %). Dual-carbon (∆14C and δ13C) isotope mixing model analyses suggested an additional input of permafrost-derived OM into deltaic waters (∼18 ±4 % of deltaic POC originates from Pleistocene deposits vs ∼ 5 ±4 % in the river main stem). Despite the lower concentration of POC in the delta than in the main stem (0.41 ±0.10 vs. 0.79 ±0.30 mg L-1, respectively ), the amount of POC derived from Pleistocene deposits in deltaic waters was almost twice as large as POC of Yedoma origin in the main stem (0.07 ±0.02 and 0.04 ±0.02 mg L-1, respectively). We assert that estuarine and deltaic processes require consideration in order to correctly understand OM dynamics throughout Arctic nearshore coastal zones and how these processes may evolve under future climate-driven change

Spatial variability of aircraft-measured surface energy fluxes in permafrost landscapes

Arctic ecosystems are undergoing a very rapid change due to global warming and their response to climate change has important implications for the global energy budget. Therefore, it is crucial to understand how energy fluxes in the Arctic will respond to any changes in climate related parameters. However, attribution of these responses is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. Here, we present the potential of environmental response functions for quantitatively linking energy flux observations over high latitude permafrost wetlands to environmental drivers in the flux footprints. We used the research aircraft POLAR 5 equipped with a turbulence probe and fast temperature and humidity sensors to measure turbulent energy fluxes along flight tracks across the Alaskan North Slope with the aim to extrapolate the airborne eddy covariance flux measurements from their specific footprint to the entire North Slope. After thorough data pre-processing, wavelet transforms are used to improve spatial discretization of flux observations in order to relate them to biophysically relevant surface properties in the flux footprint. Boosted regression trees are then employed to extract and quantify the functional relationships between the energy fluxes and environmental drivers. Finally, the resulting environmental response functions are used to extrapolate the sensible heat and water vapor exchange over spatio-temporally explicit grids of the Alaskan North Slope. Additionally, simulations from the Weather Research and Forecasting (WRF) model were used to explore the dynamics of the atmospheric boundary layer and to examine results of our extrapolation

Remote sensing of erosion and shallow water bathymetry to aid river navigation on the Colville River, Nuiqsut AK

Thesis (M.S.) University of Alaska Fairbanks, 2018The Colville is the longest river (~600 km) in Arctic Alaska. Nuiqsut is an established Alaska Native community of ~400 people on the Colville River. Its residents rely heavily on the Colville for subsistence needs, however, changing river dynamics caused by accelerated bank erosion, river siltation, low water, and shifting and drying channels are causing concern and making boat travel increasingly difficult and dangerous. Recently, local residents have reported increased erosion at bluff sites along the Colville, which threatens existing infrastructure. Also reported are unexpected shallow water sections along the main channel of the Colville, limiting their access to subsistence food sources. Residents have expressed a need for monitoring erosional rates on the Colville as well as a map product that could aid in river navigation. These concerns shaped the main goals of this Thesis: 1) To use remote sensing techniques to map and quantify erosion rates and the volume of land loss at selected bluff sites along the main channel of the Colville, and to assess the suitability of automated methods of regional erosion monitoring. 2) To use optical satellite images for mapping river bathymetry and generate GIS map products that show potential shallow water sections (<2m) and poor channel connections, and to assess the feasibility of future monitoring based off our methods that rely on extracting relative water depth values from publicly available optical remote sensing images. For our erosional study we used orthomosaics from high resolution aerial photos acquired in 1955 and 1979/1982, as well as high resolution WorldView-2 images from 2015 to quantify long-term erosion rates and the cubic volume of erosion. We found that, at the selected sites, erosion rates averaged 1 to 3.5 m per year. The erosion rate remained the same at one site and increased from 1955 to 2015 at two of the four sites. We estimated the volume of land loss to be in the magnitude of 166,000 m³ to 2.5 million m³ at our largest site. We also found that estimates of erosion were comparable for manual hand-digitized and automated methods, suggesting our automated method was effective and can be extended to monitor erosion at other sites along river systems that are bordered by bluffs. For our bathymetry study we used summer 2017 scenes from three optical sensors (PlanetScope 3m, Sentinel 2 10m, and Landsat 30m) along with field measurements on the river to map shallow water bathymetry along a 45 km stretch of the Colville. We found a strong correlation (R²=0.89) between field-measured water depths and image-derived reflectance quantity (natural log ratio of green over red bands). We analyzed the two essential criteria for suitable bathymetry mapping from optical images: clear weather and clear water conditions. We expect several days (≈16) of suitable conditions during the ice-free season to facilitate reliable bathymetry mapping and remote monitoring of shallow water sites. We also discuss a relative depth mapping technique which is useful for boat navigation in the absence of ground truth measurements. We deliberately employed simple and robust empirical techniques that could serve as a basis for a fully developed river monitoring project in the near future led by local community residents. An implementation of our methods by the community, in order to develop a river depth monitoring program, would be an important step forward for the advancement of community-based science and the co-production of knowledge. Our technique may help address emerging environmental and societal issues in other regions where sufficient river navigation fosters local livelihoods.Alaska EPSCoR Award #OIA-1208927, Alaska Space Grant, UAF Center for Global Change Gran

From Pleistocene Permafrost to Lena River Water – Organic Matter Characteristics using Biomarker Analysis and Isotope Hydrochemistry

Organic matter stored in permafrost represents one of the largest global carbon pools that are especially vulnerable due to its susceptibility to thaw and mobilisation caused by climate warming across the Arctic. However, the amount and quality of the stored carbon (C) and nitrogen (N) as well as its composition during river transit is largely unknown. The purpose of this master’s thesis is to characterize and define the source and fate of riverine C and N from the delta interior to the nearshore zone and its possible effect on primary productivity in Arctic coastal waters using a multi-proxy approach. Organic matter quality and degradation state of a rapidly degrading yedoma cliff in the central Lena Delta (Sobo Sise Island) was analyzed using lipid biomarker analysis. To grasp the winter thaw impact, a transect of water samples from the cliff going seawards were primarily investigated for N species and stable isotope composition using a hydrochemical approach. Laboratory analyses showed an overall high organic matter quality and a low degradation state in yedoma deposits which suggests freeze-locking immediately after deposition. While the dominant winter water source was attributed mainly to subsurface permafrost flow, it was found that dissolved organic nitrogen (DON) rather than nitrate is the main N species to be released into the riverine environment and was susceptible to alteration by remineralization and denitrification. Describing organic matter associated with thawing permafrost at the terrestrial-marine interface in a season-explicit study leads to a better understanding of C and N dynamics and thus the effects of a warming climate in Arctic environments

Purification of CO2 for AMS 14C analysis: Method development and application to permafrost deposits

The Arctic is most sensitive to climate change and global warming. Just recently (winter 2017/2018), this region experienced its warmest winter on record. The rising temperatures have dramatic effects on the normally frozen ground – permafrost – which underlies twenty-four percent of the land area in the northern hemisphere. The permafrost thaws much deeper and rapid erosion of deep, ice-rich permafrost will increase. The Pleistocene deep permafrost (Yedoma) deposits are particularly prone to rapid degradation due to the loss of their high ice-contents upon thaw. Through this degradation, large amounts of previously stored frozen organic carbon will be exposed to microbial decomposition, resulting in the release of the greenhouse gases carbon dioxide (CO2) and methane (CH4) to the atmosphere. This emission in turn acts as a positive feedback to the climate system. So far, it is difficult to predict the rates of greenhouse gas emission because information on the decomposability of the organic matter is limited. As the organic matter is stored for millennia in the deep permafrost deposits, the radiocarbon (14C) analysis on CO2 can be used to trace the decomposition of ancient (permafrost derived) vs. recent organic matter sources. The collection and processing of the respired CO2 for accelerator mass spectrometry (AMS) 14C analysis, however, is challenging and prone to contamination. Thus, during the progress of this thesis, we constructed a robust stainless-steel sampling device and refined a method for the collection of even small amounts (50 µg C) of CO2. This method is based on a CO2 sampling technique using a molecular sieve, which acts as an adsorbent. It has the advantage over other approaches (such as sampling in glass flasks) that CO2 can be concentrated from large air volumes. The reliability of the 14CO2 results obtained with this molecular sieve cartridge (MSC) was evaluated in detailed tests of different procedures to clean the molecular sieve (zeolite type 13X) and for the adsorption and desorption of CO2 from the zeolite using a vacuum rig. Under laboratory conditions, the contamination of exogenous carbon was determined to be less than 2.0 µg C from fossil and around 3.0 µg C from modern sources. In addition, we evaluated the direct CO2 transfer from the MSC into the automatic graphitization equipment, AGE, with the subsequent 14C AMS analysis as graphite. This semi-automatic approach is promising as it resulted in a lower modern carbon contamination of only 1.5 µg C. In addition, this analyzing procedure can be performed autonomously. To collect CO2 released from soils or sediments, additional sampling equipment, such as respiration chambers or depth samples, connected to the MSC is needed. Including the sampling equipment, a modern contamination of 3.0–4.5 µg C was obtained. Overall, these results show that the contamination becomes insignificant for large sample sizes (>500 µg C) and should be considered for smaller amounts. With this successfully tested MSC, it became possible to investigate the decomposition of the organic matter in thawing Pleistocene Yedoma deposits. On a Yedoma outcrop in the Lena River Delta, Northeast Siberia, we measured CO2 fluxes and their 14C signature to assess whether ancient (Yedoma derived) or younger C sources are preferentially respired. The CO2 released from the different sites is generally younger (2600–6500 yrs BP) than the bulk sediment (4000–31,000 yrs BP). Using isotopic mass balance calculations, we determined that up to 70% of the respired CO2 originates from ancient OM. These data show that thawing Yedoma organic matter can be rapidly decomposed, which introduces the ancient carbon into the active carbon cycle and thus increases the permafrost carbon feedback

Remote Sensing Analysis of Recent Coastal Change and Controlling Factors in Tuktoyaktuk Peninsula (Beaufort Sea Coast, Canada)

The average rate of coastal change in the Arctic Ocean is -0.5 m/yr, despite significant local and regional variations, with large areas well above -3 m/yr. Recent data suggest an acceleration of coastal retreat in specific areas due to an increasingly shorter sea ice season, higher storminess, warmer ocean waters and sea-level rise. Moreover, climate warming is inducing the subaerial degradation of permafrost and increasing land to sea sediment transportation. This work consists of the characterization and analysis of the main controlling factors influencing recent coastline change in the Tuktoyaktuk Peninsula, Northwest Territories, Canada. The specific objectives are: I. mapping Tuktoyaktuk Peninsula’s coastline at different time-steps using remote sensing imagery, II. quantifying the recent coastal change rates, III., characterizing the coastal morphology, IV. identifying the main controlling factors of the coastal change rates. A very high-resolution Pleiades survey from 2020, aerial photos from 1985 and the ArcticDEM were used. Results have shown an average coastline change rate of -1.06 m/yr between 1985 and 2020. While this number is higher than the Arctic average rate, it neglects to show the significance of extreme cases occurring in specific areas. Tundra cliffs are the main coastal setting, occupying c. 56% of the Tuktoyaktuk Peninsula coast and foreshore beaches represent 51%. The results display an influence of coastal geomorphology on change rates. The coastal retreat had higher values in backshore tundra flats (-1.74 m/yr), whereas aggradation concentrates in barrier beaches and sandspits (-0.81 m/yr). The presence of ice-wedge polygons contributes to increasing cliff retreat. Foreshore assessment may be crucial, as beaches present a hindering impact on coastal retreat (-0.76 m/yr), whereas foreshore tundra flats promote it (-1.74 m/yr). There are 48 areas with retreat rates higher than -4 m/yr, most being submersion cases. This dissertation identifies the interconnection between coastal geomorphology and change rates, raising attention to the distinct impacts of erosion and submersion processes.O permafrost tem sido um reservatório natural de carbono durante milhares de anos. Contudo, nas últimas décadas o permafrost está a degradar-se e a ser erodido a um ritmo acelerado nas costas do Oceano Ártico. Os fluxos de carbono do permafrost para a atmosfera ou para os oceanos é ainda pouco conhecido (Couture et al., 2018; Olefeldt et al., 2016). Como o carbono é um importante componente no sistema climático global, o estudo das dinâmicas costeiras em áreas de permafrost é de grande relevância, potenciando uma melhoria dos modelos e projeções climáticas. A taxa média de mudança das linhas de costa do Oceano Ártico é de -0,5 m/a, embora existam significativas variações locais e regionais, com áreas que apresentam valores acima de -3 m/a (Lantuit et al., 2012). A análise de dados mais recentes indica para uma aceleração das taxas de recuo da linha de costa devido a fatores como a subida do nível médio das águas do mar, o recuo anual das massas de gelo marinho, a maior agitação marítima e o aumento da temperatura do Oceano Ártico (O’Rourke, 2017). Além disso, as alterações climáticas estão a provocar a crescente degradação do permafrost e a aumentar o transporte de sedimentos da terra para o mar. A costa do Mar de Beaufort é considerada como uma das áreas de maior vulnerabilidade costeira à subida do nível médio das águas do mar no Ártico e no Canada (Manson et al., 2019; O’Rourke, 2017) Esta dissertação visa analisar e caracterizar os principais fatores que controlam e influenciam as dinâmicas costeiras na Península de Tuktoyaktuk (Mar de Beaufort, Territórios do Noroeste, Canada). Focando-se no uso de técnicas e imagens de deteção remota, contribui para o mapeamento da linha de costa em 1985 e 2020. Também pretende caracterizar a morfologia costeira, calcular as taxas de mudança costeira entre 1985 em 2020 e identificar os principais fatores que as controlam. Para vetorizar manualmente a linha de costa de 2020, foi utilizada uma série de 7 imagens de muito alta resolução (0,5 m) do satélite CNES/Pléiades. A linha de costa de 1985 foi obtida a partir de fotografias aéreas monocromáticas da Biblioteca Nacional de Fotografias Aéreas do Natural Resources Canada. Estas imagens foram ortorectificadas e georreferenciadas utilizando o software ENVI. Ambas as linhas de costa foram utilizadas para calcular as taxas de mudança costeira entre 1985 e 2020. As taxas foram calculadas utilizando o Digital Shoreline Analysis System v.5.0 para o ArcGIS Desktop e classificadas por End Point Rate (EPR), indicando as taxas de mudança costeira em metros por ano (Himmelstoss et al., 2018). A classificação da morfologia costeira baseou-se nos critérios de Pelletier & Medioli (2014), Couture et. al. (2015) e Irrgang et. al. (2018), adaptados às condições da Península de Tuktoyaktuk. Esta classificação foi realizada através da fotointerpretação das imagens Pléiades e da utilização do modelo de digital superfície ArcticDEM com resolução de 2 m (United States National Geospatial-Intelligence Agency e National Science Foundation). Esta classificação foi realizada separadamente para a praia-alta (backshore) e praia-baixa (foreshore), com o objetivo de melhor analisar as suas diferentes influências (Couture et al., 2015). A primeira foi definida como uma superfície emersa atingida pelas ondas em episódios de extremo hidrodinamismo, localizada entre o limite interno do sistema (ex: arriba ou vegetação de tundra) e a praia baixa. A praia baixa é a área situada entre o ponto mais elevado atingido pela corrente de afluxo em maré alta e o ponto mais baixo do refluxo em maré baixa (Trindade, 2010). A praia-alta foi dividida em três classes: arribas na tundra, áreas rasas de tundra e praias-barreira. Para uma análise mais pormenorizada, as arribas foram ainda classificadas em função da sua altura e da existência de redes densas de polígonos de cunhas de gelo. Por outro lado, as áreas rasas de tundra foram diferenciadas de acordo com a presença de áreas húmidas na faixa entremarés e considerando o grau de complexidade da linha de costa. A praia-baixa foi dividida em praias, áreas rasas de tundra e arribas vivas. As imagens Pléiades foram também utilizadas para mapear áreas de deposição de troncos de madeira, que indicam a extensão de eventos passados de storm surge. As taxas de mudança costeira foram avaliadas de acordo com a morfologia costeira, de modo a avaliar o controlo da segunda sobre a primeira. Esta análise foi realizada considerando também as áreas afetadas por storm surge. A Península de Tuktoyaktuk é dominada pela presença de arribas não consolidadas, habitualmente com praias (as arribas de tundra representam 56% do backshore e as praias existem em 51% do foreshore). Sendo esta uma caracterização generalizada, é necessário também expressar a influência que as áreas rasas de tundra e praias-barreira exercem na dinâmica costeira. A Península de Tuktoyaktuk tem uma taxa média de mudança costeira de -1,06 m/a entre 1985 e 2020, situando-se entre os valores de -0.75 m/a estimados por Solomon (2005) para a Península de Tuktoyaktuk (faixa costeira da Baía de Kugmalit) e os valores avaliados de -1.12 por Lantuit et. al. (2012) para a costa canadiana do Mar de Beaufort. A Península de Tuktoyaktuk tem uma maior área costeira perdida por ano (48 ha) do que o território vizinho de Yukon (10 ha) (Irrgang et al., 2018). As taxas de recuo variaram entre -30,9 m/a e 11,2 m/a no período estudado. Estes valores devem-se a sectores específicos que apresentam alterações costeiras extremas, tendo sido identificadas 48 áreas com taxas de recuo superiores a 4 m/a. Catorze destes casos deveram-se a processos erosivos, três foram casos de rutura de lagos termocársticos, sendo que os restantes se deveram à submersão costeira (65%), ocorrendo maioritariamente em áreas rasas de tundra. Os casos de acumulação concentram-se na unidade de Praias-Barreira e em áreas protegidas da ondulação predominante de noroeste. Quando morfologia é analisada em função das taxas de mudança costeira, as áreas rasas de tundra representam os valores mais elevados de recuo costeiro, uma vez que não protegem contra a subida do mar e contra as tempestades. No extremo oposto, a existência de praias nas áreas de foreshore revelaram um efeito atenuante no recuo costeiro (-0,76 m/a). A análise da presença de redes densas de cunhas de gelo em áreas de arribas demostrou que estas contribuem para o aumento das taxas de recuo costeiro. A avaliação da geomorfologia costeira permitiu dividir a Península de Tuktoyaktuk em quatro grandes unidades: Porto de Tuktoyaktuk – Baía de Hutchinson; Baía de Hutchinson – Ponta de Atkinson; Baía de McKinley; Baía de Seal a Cabo Dalhousie (de sudoeste para nordeste). As duas unidades mais ocidentais apresentam um maior recuo costeiro, enquanto a baía de McKinley é o setor mais estável (valores). Os resultados confirmam a influência da geomorfologia na mudança costeira e evidenciam a necessidade de esta ser incluída para uma melhor avaliação dos impactos da mudança costeira. Fatores locais como as características do permafrost e a existência de gelo no solo, precisam de ser estudados in situ e em áreas detalhadas para clarificar os seus efeitos. Outra abordagem relevante é o estudo dos fatores externos (tempestades marítimas, subida das águas do mar) na dinâmica da mudança costeira. O trabalho demonstrou que na Península de Tuktoyaktuk, muitas áreas são mais suscetíveis à submersão do que à erosão. Assim, quando se analisa a dinâmica costeira, em particular através de metodologias de classificação automática de imagens de satélite, é necessário ter cuidado para distinguir de forma clara os dois fenómenos. É especialmente relevante o diferente impacto que a submersão ou a erosão vão ter para os cálculos de balanço sedimentar e, consequentemente, na avaliação dos fluxos de carbono do permafrost para o oceano. Considerando a difícil acessibilidade das regiões costeiras do Ártico, a utilização de dados e técnicas de deteção remota é um método relevante para o estudo destas regiões. Especificamente, a resolução espacial das imagens CNES-Pléiades foi uma componente decisiva na precisão desta dissertação, indicando uma inequívoca pertinência da utilização de imagens de deteção remota de muito alta resolução. Esta dissertação permitiu abordar os controlos entre a morfologia costeira e as taxas de mudança costeira. Tal como outros estudos contemporâneos da dinâmica costeira do permafrost, teve de escolher os seus critérios de linha de costa e ter em conta todas as diferentes áreas complexas dentro da Península de Tuktoyaktuk. À medida que os dados de alta resolução espácio-temporal como os orto mosaicos obtidos por veículos aéreos não tripulados e novas constelações de satélites se tornam mais acessíveis, a capacidade de interligar a morfologia costeira e as taxas de mudança costeira no Ártico será melhorada