Description: The Action Group called ‘Standardized methods across Permafrost Landscapes: from Arctic Soils to Hydrosystems’ (SPLASH) is a community-driven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils, sediments, and water across permafrost landscapes. This unified approach will allow data from different landscape interfaces, field locations and seasons to be shared and compared, thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds.

Description: Arctic coastlines are increasingly vulnerable to erosion due to warmer temperatures destabilizing frozen cliffs, reduced protection of sea ice cover and bigger waves, especially as freeze-up becomes delayed further into the fall storm season. We have coupled a bathystrophic storm surge model to a simple numerical model of erosion of a partially frozen cliff and beach. This is a first step towards parameterization of Arctic shoreline erosion for larger-scale models that are not able to resolve the fine spatial scale (0 - 40m) needed to capture shoreline erosion rates from years to decades.

Description: Increasing warming causes severe environmental changes in the Arctic coastal zone such as longer open water periods and rising sea levels. These processes intensify the erosion of permafrost coasts and lateral transport of sediment and organic matter (OM). Lagoons play a particularly important role in the transfer process of terrestrial OM but have been rarely investigated in the Arctic. Here, we studied a lagoon system along the Arctic Yukon coast to better understand the lateral pathways of OM from land to sea and its deposition dynamics over time. We sampled terrestrial, lagoon and marine sediment to track OM along a land-lagoon-ocean transect and took short cores to assess OM deposition dynamics. Samples were analysed for total organic carbon and nitrogen (TOC, TN), stable carbon and nitrogen isotopes (δ13C, δ15N), as well as grain size and surface area. We further analysed the shoreline change rates of the lagoon from 1950s to 2018 and coupled it to sedimentation rates derived from 210Pb/137Cs dating. Turbidity was estimated in the lagoon surface water using Landsat imagery for the main wind directions. Our results show that OC concentrations significantly decrease along the land-lagoon-ocean transect. Currents potentially removed large portions of eroded OM, especially under easterly winds, which is indicated by elevated SPM concentrations. In contrast, OM can get buried quickly, which is indicated by high OM contents in deeper lagoon sediments. Coastal erosion rates in the lagoon increased drastically since the 1970s and correspond with increasing sedimentation rates, suggesting a direct relation of environmental forcing and OM deposition dynamics in the lagoon. We conclude that lagoons are a crucial transfer zone between land and ocean, which can substantially influence OM pathways. Under current environmental change scenarios in the Arctic, the role of lagoons may get more important as gateways of OM from land to sea.

Description: Warming in the Arctic causes strong environmental changes with permafrost degradation being among the most striking effects. Active layer deepening and permafrost erosion can result in the mobilization and lateral transport of organic carbon (OC), which potentially alters carbon cycles in the Arctic substantially. Although the understanding of ground ice contents and permafrost OC release is improving, still little is known of permafrost OC release rates, lateral transport pathways and its driving mechanisms on a landscape scale. In this study we investigate ground ice characteristics and OC composition of the most dominant landscape units of the Yukon coastal plain. In total, 12 permafrost cores were taken from moraine, lacustrine, fluvial and glaciofluvial deposits with a SIPRE corer. Ground ice and sediment contents were analysed using computed tomography and k-means classification. Active layer and upper permafrost were subsampled to analyse OC contents and isotopes of bulk material and a leaching-incubation experiment was conducted with active layer and permafrost sediments to assess potential dissolved OC export and degradation rates. Preliminary results show that ground ice contents vary significantly between landscape units. Ground ice contents in permafrost average 72.4 vol.-% with highest contents in moraines (78.3 vol.-%) and lowest contents in fluvial deposits (53.2 vol.-%). We expect highest dissolved OC leaching and loss rates from permafrost in contrast to active layer and from fluvial and lacustrine deposits, as they simply contain more OC. Yet, lateral OC transport is more likely for landscapes with a topographic gradient such as ground ice-rich moraines. We conclude that due to the high ground ice contents on the Yukon coastal plain, substantial changes of the permafrost landscape will occur under current warming trends. This will include subsidence, abrupt erosion, changes in hydrology and OC degradation processes, which will differ between landscape units.

Description: Wind and wave conditions are a primary concern for many people living along the coastline, but when considering the partially frozen coastline in the Arctic, this concern is highlighted by the cascading detrimental thawing effects on indigenous cultural sites and subsistence practices. Media coverage has extensively shown cemeteries being washed away into the sea, ice cellars being inundated with floodwaters, and entire villages planning to relocate without having the funds to do so. If we take a look further offshore, sea state directly impacts the safety of subsistence hunters travelling by boat, leading to the fact that a lengthening open water season does not necessarily mean the same increase in the number of safely boat-able days. Beyond the scope of native communities, but still well within the lens of the media, professional sailors are constantly looking for products that improve their knowledge and forecasts of sea state to better inform which routes and actions they will take during months-long competitions. This talk will contain a broad overview of the specific uses of wave and wind information, citing specific examples from the authors’ own experience on coastal erosion model development and interaction with Arctic native coastal communities. A main goal of this talk is also to illuminate the incentives for the scientific community to be actively engaged in improving operational sea state products, from Arctic indigenous coastal communities to professional sailors, particularly in light of the increasing media attention to the general public.

Description: Permafrost coasts make up roughly one third of all coasts worldwide. Their erosion leads to the release of previously locked organic carbon, changes in ecosystems and the destruction of cultural heritage, infrastructure and whole communities. Since rapid environmental changes lead to an intensification of Arctic coastal dynamics, it is of great importance to adequately quantify current and future coastal changes. However, the remoteness of the Arctic and scarcity of data limit our understanding of coastal dynamics at a pan-Arctic scale and prohibit us from getting a complete picture of the diversity of impacts on the human and natural environment. In a joint effort of the EU project NUNATARYUK and the NSF project PerCS-Net, we seek to close this knowledge gap by collecting and analyzing all accessible high-resolution shoreline position data for the Arctic coastline. These datasets include geographical coordinates combined with coastal positions derived from archived data, surveying data, air and space born remote sensing products, or LiDAR products. The compilation of this unique dataset will enable us to reach unprecedented data coverage and will allow us a first insight into the magnitude and trends of shoreline changes on a pan-Arctic scale with locally highly resolved temporal and spatial changes in shoreline dynamics. By comparing consistently derived shoreline change data from all over the Arctic we expect that the trajectory of coastal change in the Arctic becomes evident. A synthesis of some initial results will be presented in the 2020 Arctic Report Card on Arctic Coastal Dynamics. This initiative is an ongoing effort – new data contributions are welcome!

Description: This data set contains a first‐order estimate of distribution, thickness and ice-content of submarine permafrost on the Arctic shelf based on a numerical heat transfer model. Our model uses dynamic upper boundary conditions that synthesize Earth System Model air temperature, ice mass distribution and thickness, and global sea level reconstruction and applies globally distributed geothermal heat flux as a lower boundary condition. Sea level reconstruction accounts for differences between marine and terrestrial sedimentation history. Sediment composition and pore water salinity are integrated in the model. Model runs for 450 ka for cross‐shelf transects were used to initialize the model for circumarctic modeling for the past 50 ka.This data set consists of current sea levels, and permafrost depth [m below sea floor(m bsf)], total ice-content [m^2 / m^3] and enthalpy [MJ / m^2] at times 50ka, 25ka and 0a before industrialization for 15892 locations on the Arctic shelf. Additionally zonations for permafrost depth and ice-content are given as layer files. Based on the undertaken sensitivity studies zones with 〈100m permafrost are uncertain, zones with 100-300m are probable, and zones with 〉300m are confident.

Description: In the last century the number of retrogressive thaw slumps has doubled in some arctic regions, e.g. Herschel Island, Yukon Territory, Canada [Lantuit and Pollard, 2008]. Retrogressive thaw slumps are a common thermocarst landform along the coast of Herschel Island [Lantuit and Pollard, 2005]. However mechanical conditions leading to the evolution of those retrogressive thaw slumps are poorly understood. For a better understanding of internal thermal processes in these retrogressive thaw slumps we implemented different electrical resistivity profiles (ERT). They cross the focused thaw slump longitudinally and transversally. We compared about 2 km of new ERT-data from 2019 with the same transects from 2011 to gain information about the temperature distribution and the temperature changes in the slump ground. The aim for our study is to gain a profound understanding of the strong and deep thermal disturbances generated by retrogressive thaw slumps and how they change over time, leading to a possible polycyclicality of these slumps.

Description: Changing environmental conditions in the Arctic have profound impacts on permafrost coasts, which erode at great pace. Although numbers exist on annual carbon and sediment fluxes from coastal erosion, little is known on how terrestrial organic matter (OM) is transformed by thermokarst and –erosional processes on transit from land to sea. Here, we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island in the western Canadian Arctic. The RTS was classified into an undisturbed, disturbed and nearshore zone and systematically sampled along transects. Collected sediments were analyzed for organic carbon (OC), nitrogen (N), stable carbon isotopes (δ13C-OC) and ammonium. C/N-ratios, δ13C-signatures and ammonium concentrations were used as general indicator for OM degradation. Permafrost sediments from the RTS headwall and mud lobe sediments from the thaw stream outlet were incubated to further assess OM degradation and potential greenhouse gas formation during slumping and upon release into the nearshore zone. Our results show that OM concentrations significantly decrease upon slumping in the disturbed zone with OC and N decreasing by 〉70% and 〉50%, respectively. Whereas δ13C-signatures remain fairly stable, C/N-ratios decrease significantly and ammonium concentrations increase slightly in fresh slumping material. Nearshore sediments have low OM contents and a terrestrial signature comparable to disturbed sites on land. The incubations show that carbon dioxide (CO2) forms quickly from thawing permafrost deposits and mud debris with ~2-3 mg CO2 per gram dry weight being cumulatively produced within two months. We suggest that the initial strong decrease in OM concentration after slumping is caused by a combination of OC degradation, dilution with melted massive ice and immediate offshore transport via the thaw stream. After stabilization in the slump floor, recolonizing vegetation takes up N from the disturbed sediment. Upon release into the nearshore zone, larger portions of OM are directly deposited in marine sediments, where they further degrade or being buried. The incubations indicate that CO2 is rapidly produced upon slumping and potentially continues to form within the nearshore zone that receives eroded material. We conclude that coastal RTS systems profoundly change the characteristic of modern and ancient permafrost terrestrial OM during transit from land to sea - a process which is likely linked to the production of greenhouse gases. Our study provides valuable information on the potential fate of terrestrial OM along eroding permafrost coasts under the trajectory of a warming Arctic.

Description: Thermal erosion of permafrost coasts delivers large quantities of organic carbon (OC) to arctic coastal waters. While deposition of permafrost OC in nearshore sediments potentially attenuates the ‘permafrost carbon feedback’, continued resuspension of sediments by waves, storms and currents potentially enhances greenhouse gas production in the nearshore zone. Recent studies, focusing on bulk sediments, suggest that permafrost OC derived from coastal erosion is predominantly deposited in the nearshore zone. However, hydrodynamic gradients in the coastal zone allow sorting processes to strongly influence the OC distribution and fate, which cannot be assessed by using bulk sediment approaches. Here, we study soils and sediments fractionated by density (1.8 g/cm-3 cutoff), separating the organic from the mineral-associated fraction, and size (63 µm), separating sand-associated from silt and clay-associated OC. We sampled sediments along a transect from an active retrogressive thaw slump at the coast of Herschel Island - Qikiqtaruk (Yukon, Canada), to the nearshore zone, towards an offshore sedimentary basin. Each sediment fraction was analysed for its elemental content (TOC, TN), carbon isotope signature (δ13C, Δ14C), molecular biomarkers (n-alkanes, n-alkanoic acids, lignin phenols, cutin acids), and mineral surface area. Preliminary data show that the OC partitioning between the sediment fractions changes considerably over the transect, suggesting that hydrodynamic sorting processes take place. Additionally, the OC characteristics of the fractions are significantly different from each other. For example, the low-density organic fraction shows a slightly less degraded signal than the high-density silt- and clay-associated OC fraction in several molecular biomarker proxies, and has a higher average TOC/TN ratio (24 ±3 versus 12 ±2). We aim to disentangle sorting processes and degradation mechanisms of permafrost OC along this transect of fractionated soils and sediments in the nearshore zone, and give new insights into pathway of this material upon erosion.