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Erosion of permafrost coasts has received increasing scientific attention since 1990s because of rapid land loss and the mobilisation potential of old organic carbon. The majority of permafrost coastal erosion studies are limited to time periods from a few years to decades. Most of these studies emphasize the spatial variability of coastal erosion, but the intensity of inter-annual variations, including intermediate coastal aggradation, remains poorly documented. We used repeat airborne Light Detection And Ranging (LiDAR) elevation data from 2012 and 2013 with 1 m horizontal resolution to study coastal erosion and accompanying mass-wasting processes in the hinterland. Study sites were selected to include different morphologies along the coast of the Yukon Coastal Plain and on Herschel Island. We studied elevation and volume changes and coastline movement and compared the results between geomorphic units. Results showed simple uniform coastal erosion from low coasts (up to 10 m height) and a highly diverse erosion pattern along coasts with higher backshore elevation. This variability was particularly pronounced in the case of active retrogressive thaw slumps, which can decrease coastal erosion or even cause temporary progradation by sediment release. Most of the extremes were recorded in study sites with active slumping (e.g. 22 m of coastline retreat and 42 m of coastline progradation). Coastline progradation also resulted from the accumulation of slope collapse material. These occasional events can significantly affect the coastline position on a specific date and can affect coastal retreat rates as estimated in long term by coastline digitalisation from air photos and satellite imagery. These deficiencies can be overcome by short-term airborne LiDAR measurements, which provide detailed and high-resolution information about quickly changing elevations in coastal areas.

Permafrost landscapes experience different disturbances and store large amounts of organic matter, which may become a source of greenhouse gases upon permafrost degradation. We analysed the influence of terrain and geomorphic disturbances (e.g. soil creep, active‐layer detachment, gullying, thaw slumping, accumulation of fluvial deposits) on soil organic carbon (SOC) and total nitrogen (TN) storage using 11 permafrost cores from Herschel Island, western Canadian Arctic. Our results indicate a strong correlation between SOC storage and the topographic wetness index. Undisturbed sites stored the majority of SOC and TN in the upper 70 cm of soil. Sites characterised by mass wasting showed significant SOC depletion and soil compaction, whereas sites characterised by the accumulation of peat and fluvial deposits store SOC and TN along the whole core. We upscaled SOC and TN to estimate total stocks using the ecological units determined from vegetation composition, slope angle and the geomorphic disturbance regime. The ecological units were delineated with a supervised classification based on RapidEye multispectral satellite imagery and slope angle. Mean SOC and TN storage for the uppermost 1 m of soil on Herschel Island are 34.8 kg C m‐2 and 3.4 kg N m‐2, respectively. Copyright © 2015 John Wiley & Sons, Ltd.

Abstract. Monitoring the thermal state of permafrost (TSP) is important in many environmental science and engineering applications. However, such data are generally unavailable, mainly due to the lack of ground observations and the uncertainty of traditional physical models. This study produces novel permafrost datasets for the Northern Hemisphere (NH), including predictions of the mean annual ground temperature (MAGT) at the depth of zero annual amplitude (DZAA) (approximately 3 to 25 m) and active layer thickness (ALT) with 1 km resolution for the period of 2000–2016, as well as estimates of the probability of permafrost occurrence and permafrost zonation based on hydrothermal conditions. These datasets integrate unprecedentedly large amounts of field data (1002 boreholes for MAGT and 452 sites for ALT) and multisource geospatial data, especially remote sensing data, using statistical learning modeling with an ensemble strategy. Thus, the resulting data are more accurate than those of previous circumpolar maps (bias = 0.02±0.16 ∘C and RMSE = 1.32±0.13 ∘C for MAGT; bias = 2.71±16.46 cm and RMSE = 86.93±19.61 cm for ALT). The datasets suggest that the areal extent of permafrost (MAGT ≤0 ∘C) in the NH, excluding glaciers and lakes, is approximately 14.77 (13.60–18.97) × 106 km2 and that the areal extent of permafrost regions (permafrost probability >0) is approximately 19.82×106 km2. The areal fractions of humid, semiarid/subhumid, and arid permafrost regions are 51.56 %, 45.07 %, and 3.37 %, respectively. The areal fractions of cold (≤-3.0 ∘C), cool (−3.0 ∘C to −1.5 ∘C), and warm (>-1.5 ∘C) permafrost regions are 37.80 %, 14.30 %, and 47.90 %, respectively. These new datasets based on the most comprehensive field data to date contribute to an updated understanding of the thermal state and zonation of permafrost in the NH. The datasets are potentially useful for various fields, such as climatology, hydrology, ecology, agriculture, public health, and engineering planning. All of the datasets are published through the National Tibetan Plateau Data Center (TPDC), and the link is https://doi.org/10.11888/Geocry.tpdc.271190 (Ran et al., 2021a).

Ice-rich permafrost coasts often undergo rapid erosion, which results in land loss and release of considerable amounts of sediment, organic carbon and nutrients, impacting the near-shore ecosystems. Because of the lack of volumetric erosion data, Arctic coastal erosion studies typically report on planimetric erosion. Our aim is to explore the relationship between planimetric and volumetric coastal erosion measurements and to update the coastal erosion rates on Herschel Island in the Canadian Arctic. We used high-resolution digital elevation models to compute sediment release and compare volumetric data to planimetric estimations of coastline movements digitized from satellite imagery. Our results show that volumetric erosion is locally less variable and likely corresponds better with environmental forcing than planimetric erosion. Average sediment release volumes are in the same range as sediment release volumes calculated from coastline movements combined with cliff height. However, the differences between these estimates are significant for small coastal sections. We attribute the differences between planimetric and volumetric coastal erosion measurements to mass wasting, which is abundant along the coasts of Herschel Island. The average recorded coastline retreat on Herschel Island was 0.68 m a(1 for the period 2000Á2011. Erosion rates increased by more than 50% in comparison with the period 1970Á2000, which is in accordance with a recently observed increase along the Alaskan Beaufort Sea. The estimated annual sediment release was 28. Arctic coastal erosion rates are among the highest measured in the world despite the fact that the erosional processes are limited to the short ice-free season, which lasts three to four months (Aré 1988;Overduin et al. 2014). Local coastal erosion rates in sites with exposed ice-rich permafrost can exceed 20 m a (1 (Jones et al. 2009;Gü nther et al. 2013;Gü nther et al. 2015). reported an average erosion rate of 0.5 m a (1 for the entire Arctic; 3% of the Arctic coastline is retreating faster than 3 m a (page number not for citation purpose) sea-surface temperatures and a longer open water season that will likely increase erosion rates (Overeem et al. 2011;Stocker et al. 2013;Gü nther et al. 2015).Erosion of permafrost coasts can cause rapid land loss, which can lead to a loss of habitat, natural resources and archaeological sites, and can endanger modern infrastructure and communities (Johnson et al. 2004;Mars & Houseknecht 2007). Jones et al. (2008) used aerial photography to identify cultural and historical sites on the Alaskan Beaufort Sea coast that were threatened or had already been eroded by coastal erosion. According to Mars & Houseknecht (2007), the threat of land loss can be reasonably well resolved based on coastline retreat rate data derived from satellite imagery.Soils and unconsolidated deposits in the northern circumpolar region store large quantities of soil organic carbon (Hugelius et al. 2014). Considerable proportions of this carbon are released to...

Coastal ecosystems in the Arctic are affected by climate change. As summer rainfall frequency and intensity are projected to increase in the future, more organic matter, nutrients and sediment could be mobilized and transported into the coastal nearshore zones. However, knowledge of current processes and future changes is limited. We investigated streamflow dynamics and the impacts of summer rainfall on lateral fluxes in a small coastal catchment on Herschel Island in the western Canadian Arctic. For the summer monitoring periods of 2014-2016, mean dissolved organic matter flux over 17 days amounted to 82.7 ± 30.7 kg km −2 and mean total dissolved solids flux to 5252 ± 1224 kg km −2 . Flux of suspended sediment was 7245 kg km −2 in 2015, and 369 kg km −2 in 2016. We found that 2.0% of suspended sediment was composed of particulate organic carbon. Data and hysteresis analysis suggest a limited supply of sediments; their interannual variability is most likely caused by short-lived localized disturbances. In contrast, our results imply that dissolved organic carbon is widely available throughout the catchment and exhibits positive linear relationship with runoff. We hypothesize that increased projected rainfall in the future will result in a similar increase of dissolved organic carbon fluxes.Key words: permafrost, hydrology, lateral fluxes, hysteresis, climate change.Résumé : Les écosystèmes côtiers dans l'Arctique sont touchés par le changement climatique. Comme la fréquence et l'intensité des pluies d'été sont censées augmenter à l'avenir, plus de matière organique, de substances nutritives et de sédiments pourraient être mobilisés et transportés dans les zones proches des côtes. Par contre, la connaissance quant aux processus actuels et quant aux changements futurs est limitée. Nous avons examiné la dynamique de débit d'eau et les impacts des pluies d'été sur les flux latéraux dans un petit

a b s t r a c tIce-wedge polygon (IWP) peatlands in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from an IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, d 13 C), stable water isotopes (d 18 O, dD), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUs) correspond to the main stages of deposition (1) in a thermokarst lake (SU1: 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions of the IWP field that developed after drainage (SU3: 3120 cal yrs BP to 2012 CE). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatom species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic diatom species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene.

Permafrost is defined as ground (soil or rock and any ice and organic material inclusions) that remains at or below 0°C for two consecutive years or longer (Van Everdingen, 2005). The role of permafrost in affecting the global carbon cycle, natural hazards, and infrastructure is being increasingly acknowledged (Pörtner et al., 2019). This has resulted in an increase in the number of publications reporting or building upon how much of the Earth's surface is underlain by permafrost (Table S1).Permafrost presence can vary at a scale of tens of meters due to heterogeneous snow cover, vegetation, terrain, hydrology, and soil properties (Brown, Roger, et al., 1973;Gisnås et al., 2014;Gubler et al., 2011;Smith, 1975). Permafrost distribution has therefore been traditionally conceptualized in terms of permafrost zones that describe the fraction of ground underlain by permafrost. In permafrost zones, where the proportion of ground underlain by permafrost is small (sporadic permafrost or isolated patches), are areas where permafrost is present only in the most favorable conditions, for example where snow cover is thin or in peatlands.Although the range of areas underlain by permafrost for each zone varies between the studies (Heginbottom et al., 2012), they are most frequently defined as continuous (90%-100%), discontinuous (50%-90%), sporadic (10%-50%), and isolated patches (10% or less) (Brown et al., 1997) (Figure 1). As such, permafrost zones are useful for cartographic displays because they aggregate fine-scale binary data to coarse scales. Early permafrost mapping attempts at local and national scales have already followed this zonation concept (Ferrians, 1965), which has also been adopted by recent permafrost modeling efforts (Gruber, 2012;.