Remote sensing analysis of recent coastal change and its controlling factors in Darnley Bay (Amundsen Gulf, Canada)

As the Arctic warms, permafrost coasts are experiencing higher rates of erosion, threatening coastal communities and infrastructure, and altering sediment and nutrient budgets. However, some areas are still neglected by research. The mouth of the Gulf of Amundsen is home to Darnley Bay, while the coast of the ecologically important Cape Parry to Paulatuk area included in the Anguniaqvia Niqiqyuam Marine Protected Area has been still little studied. This area is home to Arctic char, cod, beluga whales, ringed and bearded seals, polar bears and sea birds. It is also an important area for the Inuvialuit who have an intrinsic attachment to their land ensuring the survival of their culture and food source. Settled in Paulatuk, Inuvialuit are witnessing the warming of their territory and the degradation of the permafrost. This study aims to establish the geomorphological characterization of the Paulatuk coast and peninsula and to quantify coastal changes over 55 years, using a new very high resolution survey based on CNES Pleiades imagery from August 2020, as well as historical aerial imagery from 1965. Key areas, such as Paulatuk, were also surveyed using unmanned aerial vehicles in 2019. The results indicate a small average erosion rate of -0.1 m/year of the surveyed coastlines from 1965 to 2020. At a regional scale, there is a disparity in erosion rates depending on the type of substrate. Erosion rates are significantly different in function of the type of coastal material. Unconsolidated areas show erosion rates of up to -3 m/year while consolidated express stability. These values are relatively low compared to other sites on the Beaufort Sea Coast (e.g. Qikiqtaryuk/Herschel Island, Yukon coast, Mackenzie delta), which are more susceptible to erosion due to soil composition, ground ice content, cliff height and exposure to swells. The very high resolution geomorphological mapping provide important spatial information to the coastal community. Paulatuk is showing signs of degrading permafrost landscape with subsidence zones and potential thaw ponds drainage. A preliminary assessment suggest that infrastructure construction influences permafrost degradation and that future soil thawing process could become a threat for the community. This study, based on unprecedented very high resolution data contributes to the general characterization and identification of erosion rates of the Arctic coasts.Com o progressivo aquecimento do Ártico, as costas com permafrost estão progressivamente a sofrer taxas de erosão mais elevadas, ameaçando as comunidades e infraestruturas costeiras, alterando os balanços de sedimentos e nutrientes, e influenciando o ciclo do carbono. No entanto, amplas regiões ainda têm uma dinâmica ainda pouco conhecida. Este é o caso do Golfo de Amundsen, onde se integra Darnley Bay, bem como a costa da importante área ecológica entre o Cabo Parry e Paulatuk, incluída na Área Protegida Marinha Anguniaqvia Niqiqyuam. Esta área é um importante habitat do Arctic char, bacalhau, belugas, focas aneladas e de barbas, ursos polares e de várias aves marinhas. É também uma área importante para os Inuvialuit que mantêm uma ligação intrínseca à sua terra, garantindo a sobrevivência da sua cultura e fonte alimentar natural. Estabelecidos em Paulatuk, os Inuvialuit são testemunhas do aquecimento do seu território e da degradação do permafrost. Este estudo visa estabelecer a caracterização geomorfológica da costa entre o Cabo Parry e Paulatuk e quantificar as principais modificações da linha de costa num período de 55 anos. Utiliza-se, para isso, um novo levantamento de muito alta resolução baseado nas imagens do satélite CNES Pleiades de Agosto de 2020, bem como fotos aéreas de 1965. Áreas-chave, como Paulatuk, foram levantadas utilizando veículos aéreos não tripulados em 2019. Os resultados indicam uma taxa média de erosão da linha de costa de -0,1 m/ano entre 1965 e 2020. À escala regional, esta taxa é variável, dependendo principalmente do tipo de substrato costeiro. As áreas não consolidadas apresentam taxas de erosão de até -3 m/ano, enquanto que valores muito próximos de 0 m/ano, caracterizam as costas talhadas em substrato consolidado. Estes valores são relativamente baixos em comparação com outros setores da costa do Mar de Beaufort (por ex.: Qikiqtaryuk/Herschel Island, Yukon, delta do Rio Mackenzie), que são mais susceptíveis à erosão devido à composição do solo, teor de gelo no solo, altura das arribas e exposição à ondulação. A cartografia geomorfológica de muito alta resolução realizada forneceu informações espaciais importantes para a comunidade costeira de Paulatuk. A Peninínsula de Paulatuk mostra sinais de degradação do permafrost, com zonas de subsidência e aumento da extensão dos lagos termocársicos. Uma avaliação preliminar sugere que a construção de infra-estruturas está a influenciar a degradação do permafrost e que o futuro processo de descongelamento do solo poderá tornar-se uma ameaça para a comunidade. Este estudo, apoiado em dados de deteção remota com muita alta resolução, é um contributo paraconsolidar a caracterização da costa de Darnley Bay e para a identificação das taxas de erosão costeira no Árctico.This work is part of the Nunataryuk funded under the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 773421, and with co-funding by the Climate Change Preparedness in the North (CCPN) program

Retrogressive thaw slumps and active layer detachment slides in the Brooks Range and foothills of northern Alaska: terrain and timing

Thesis (Ph.D.) University of Alaska Fairbanks, 2015Permafrost degradation is widespread throughout the circumpolar north, occurring by multiple modes and mechanisms on many types of landscapes. The pan-Arctic rate of permafrost degradation is reportedly increasing, and permafrost carbon and nitrogen release are likely to be major contributors to global atmospheric greenhouse gas concentrations in coming decades. Locally, liberation of previously frozen substrates, organic materials, and nutrients alters the ecology of receiving streams, causes ecological and hydrobiogeochemical impacts in lake ecosystems, and impacts vegetation through disturbance, nutrient release, and succession on altered surfaces. Understanding the diverse modes of permafrost landscape response to climate, within time and space, is critical to questions of future impacts and feedbacks to climate change. Active layer detachment sliding and retrogressive thaw slumping are important modes of upland permafrost degradation and disturbance throughout the low arctic, and have been linked with climate warming trends, ecosystem impacts, and permafrost carbon release. In the Brooks Range and foothills study region of northwest Alaska, active layer detachment slides and retrogressive thaw slumps are widespread and prominant modes of permafrost degradation. Their distribution has been partially correlated with landscape properties, especially upper permafrost characteristics. However, drivers of active layer detachment slide and retrogressive thaw slump distribution and initiation triggering mechanisms, are poorly understood in this region, and detailed spatial distribution of permafrost characteristics is particularly lacking for the entire area. To better understand retrogressive thaw slump initiation triggers, this research used archived ERS-1 synthetic aperture RADAR data (1997-2010) to determine the year of first detection for 21 active retrogressive thaw slumps in the Noatak Basin, and examined weather records from remote and regional weather stations (1992-2011), along with satellite image-derived seasonal snowpack distribution (2000-2012) for correlations among weather, snowpack duration, and the timing of retrogressive thaw slump initiation. Most slumps first appeared within a 13 month span beginning June of 2004. Early summer 2004 was distinct in the weather records for anomalously warm early thaw-season temperatures, intense rainfall events in May, and unusually early dissipation of the annual snowpack. Results suggest that, regionally, retrogressive thaw slump initiation may be clustered in time, in response to seasonal shifts or anomalous weather events, and that future landscape response to climate change may depend on the nature and timing of climate change as much as overall magnitude. SS_para>The project examined inter-related and co-varying terrain properties at specific sites to identify relationships among terrain properties and permafrost characteristics. Consistent relationships among vegetation, surficial geology and permafrost characteristics were found using multiple factor analysis ordination of empirical data from diverse field sites throughout the region. Ordination results suggest relevant relationships among these factors to support regional-scale spatial analysis of terrain and permafrost properties. Field sites were also found to form consistent groupings from hierarchical clustering of ordination results, suggesting that relationships among these factors remain relevant across diverse gradients of landscape conditions in the region. Several thousand observed feature locations of active layer detachment slides and retrogressive thaw slumps were then used to examine region-wide terrain suitability based on terrain properties including: surficial geology, topography, geomorphology, vegetation and hydrology. Structural equation modeling and integrated terrain unit analyses confirmed and identified the nature and relative strength of relationships among terrain factors explaining observed feature distribution. These results may partially correspond with permafrost ground ice conditions as well, which is further supported by our ordination results. Analysis results drove mapped estimates of terrain suitability for active layer detachment slides and retrogressive thaw slumps across the region, enabling better estimates of permafrost carbon vulnerable to release, and ecosystems potentially impacted by these modes of permafrost degradation. Up to 57% of the study region may contain 'suitable' terrain for one or both of these features. Results support a 'state factor' approach as a useful organizing framework for assessing and describing terrain suitability, and for examining drivers of permafrost characteristics

Pathways for Ecological Change in Canadian High Arctic Wetlands Under Rapid Twentieth Century Warming

We use paleoecological techniques to investigate how Canadian High Arctic wetlands responded to a midtwentieth century increase in growing degree days. We observe an increase in wetness, moss diversity, and carbon accumulation in a polygon mire trough, likely related to ice wedge thaw. Contrastingly, the raised center of the polygon mire showed no clear response. Wet and dry indicator testate amoebae increased concomitantly in a valley fen, possibly relating to greater inundation from snowmelt followed by increasing evapotranspiration. This occurred alongside the appearance of generalist hummock mosses. A coastal fen underwent a shift from sedge to shrub dominance. The valley and coastal fens transitioned from minerogenic to organic‐rich wetlands prior to the growing degree days increase. A subsequent shift to moss dominance in the coastal fen may relate to intensive grazing from Arctic geese. Our findings highlight the complex response of Arctic wetlands to warming and have implications for understanding their future carbon sink potential

Remote Sensing of Environmental Changes in Cold Regions

This Special Issue gathers papers reporting recent advances in the remote sensing of cold regions. It includes contributions presenting improvements in modeling microwave emissions from snow, assessment of satellite-based sea ice concentration products, satellite monitoring of ice jam and glacier lake outburst floods, satellite mapping of snow depth and soil freeze/thaw states, near-nadir interferometric imaging of surface water bodies, and remote sensing-based assessment of high arctic lake environment and vegetation recovery from wildfire disturbances in Alaska. A comprehensive review is presented to summarize the achievements, challenges, and opportunities of cold land remote sensing