Description: Arctic permafrost coasts, especially when they are unconsolidated and ground ice rich, are extremely vulnerable to climate change. Rising temperatures of air and seawater, lengthening of the open-water season and increase in storm events are likely to prompt higher rates of coastal erosion and consequently increase the rate of land loss and material transport to the near-shore zone. Many studies have addressed this issue by compiling rates of shoreline erosion over the past fifty to sixty years to find trends, yet few investigations have attempted to look at it in three dimensions and at annual time scales, although erosion of Arctic coasts is known to be very complex and nonlinear. This study focuses on high resolution short-term (one year) erosion rates and geomorphic change. It is based on DEMs that were obtained from LIDAR surveys of the Yukon Coast and Herschel Island during the AIRMETH campaigns in 2012 and 2013. The DEMs were processed to obtain a horizontal resolution of 1 meter and serve as an elevation source from which the comparison was made. The elevations from the 2012 DEM were then deducted from elevations in 2013 to obtain erosion and accumulation values for each pixel. Preliminary results show that coastal retreat encompasses a range of processes acting at different temporal and spatial scales. They can be divided into denudation and abrasion processes. Denudation is the various types of mass wasting, such as translational slides, active layer detachments or retrogressive thaw slumps. The material delivered from these abrupt events is made available for abrasion, which is transferring the material to the shoreface at longer time scales. The accumulated material temporarily protects cliffs from incident wave energy and abrasion is reactivated when the material is removed. The erosion from gullies and thermo-erosional valleys is another form of material delivery to coast. Shoreline retreats from 2 to 5 meters were recorded on the most exposed parts of the coast, while vertical changes of cliffs account locally for more than 10 meters and extend up to 20 meters laterally. Locations where these high numbers are observed are often characterised by the adjacent accumulation of material on the beach. This study shows that the pathways for the transfer of material from the coast to the sea are very diverse and are often limited by the ability of abrasion to remove material delivered by the mass wasting of coastal bluffs.

Description: Arctic permafrost coasts make up ~34% of the world’s coastline (ca. 400,000 km) and are often made of ice-rich unconsolidated sediments. This makes them highly susceptible to coastal erosion, and it is likely that large quantities of carbon are released, because permafrost soils are considered to hold approximately 50% of the global soil organic carbon pool. Current estimates of the carbon released by coastal erosion focus solely on particulate organic carbon (POC). Dissolved organic carbon (DOC) is generally not included in these calculations, because estimations of DOC contents in ground ice, which is overwhelmingly present along Arctic coasts, do not exist. In some cases, ground ice occupies as much as 90% of coastal bluffs with 40 m in height, where the coastline erodes at rates approaching 20 m/yr at its maximum. Here, we report DOC contents within permafrost from different ground ice types throughout the Arctic (Canada, Alaska, Siberia). We put them into context of Arctic organic carbon pools and fluxes, and evaluate their contribution to the Arctic carbon budget against the background of increasing permafrost degradation and enhancing coastal erosion in the future. For example, DOC concentrations in massive ground ice bodies including ice wedges range between 〈1.0 and 28.6 mg/L, while ice wedges have the greatest potential as DOC pool due to their wide spatial distribution in late Pleistocene and Holocene polygonal ground. Siberian Ice Complex deposits (Yedoma) are thought to consist of up to 50% of ice wedges by volume and are therefore a substantial pool of DOC. Intrasedimental ice (non-massive) like ice lenses and pore ice are another important part of unconsolidated permafrost deposits. DOC concentrations within intrasedimental ice differ in orders of magnitude compared to massive ice and rise up to 1200 mg/L. Although these numbers might be still small compared to the POC stocks in peat and mineral soils, DOC is chemically labile and may directly enter local food webs of the near-shore zone. Moreover, due to its lability, DOC is quickly mineralized and returned to the atmosphere when released due to permafrost degradation. Robust estimations of how much organic carbon is potentially released from permafrost are crucial for predicting the strength and timing of carbon-cycle feedback mechanisms in the Arctic. This approach shall lead to an improved understanding of how important permafrost thaw in general and the erosion of permafrost coasts in particular are for the climate development this century and beyond. This is especially important in the Arctic before the background of expected rising air and sea surface temperatures, prolongation of the open-water season, increasing storm frequency and accelerating eustatic sea level rise.

Description: A thermokarst lake sediment core from the centre of Herschel Island was analysed in order to reconstruct post-glacial palaeoenvironmental changes and landscape dynamics in this part of the Western Canadian Arctic. The ice-rich island in the Southern Beaufort Sea is of outstanding scientific interest since it archives the northernmost terrestrial lake record of the Yukon Territory. Besides previously published sedimentological and biogeochemical analyses, we applied micropaleontology and hydrochemistry on pore waters. The formation of the lake occurred during the Holocene Thermal Maximum, around 11.5 to 10.0 cal ka BP. Here, brackish shallow water ostracods (Heterocyprideis sorbyana) and foraminifers (Cribroelphidium excavatum) prevailed and electrical conductivity of pore waters of approximately 13,000 µS/cm demonstrates a marine influence. Reworking from older sediments, however, cannot be ruled out completely. The lake development until about 7.0 cal ka BP was associated with a period of intense thermokarst activity and the pollen-based temperature reconstruction shows that TJuly was greater than 8°C during the early Holocene at the initial stage of Lake Herschel. The freshwater ostracod Cytherissa lacustris was the dominant species. Pollen concentrations and influx were low prior to 6.0 cal ka BP and subsequently increased, especially in the past thousand years. The ostracod association became more diverse in the Mid-Holocene; Fabaeformiscandona levanderi is the dominant species besides C. lacustris. The reconstructed TJuly were lower from 7.0 to 5.5 cal ka BP and relatively high but variable until 1.8 cal ka BP. Pollen of Cyperaceae and Poaceae were generally the most abundant taxa. However, Poaceae pollen increased in sediments younger than 3.0 cal ka BP and Cyperaceae pollen decreased after 1.8 cal ka BP. Pollen from several shrubs were found in relatively high quantities, including Alnus, Juniperus and Betula; only the latter is found in the recent tundra environment. The ostracod associations show a persistent lake with high input of allochthonous material and possibly elevated salinity. A change in the sedimentation rate between 1.8 to 0.9 cal ka BP is explained either by a hiatus due to modified drainage conditions or slumping. Bioproductivity increased, as shown by a richer fauna (Chironomidae). Foraminifers are abundant and occur together with fresh and brackish water ostracods reflecting elevated salinity. The change of facies is also recorded in pore waters chemistry characterized by lower pH values, slightly higher electrical conductivity and increased Ca, Mg, Mn, Sr and SO4 ion content. The final late-Holocene phase, beginning by 0.9 cal ka BP, was characterized by an elevated and variable NO3 ion content in pore waters, a poorer ostracod fauna and disappearance of foraminifers, as well as pollen-based TJuly below 7°C.

Description: Permafrost is a direct indicator of climate change and permafrost temperature and active-layer thickness have been identified as Essential Climate Variables (ECV) by the global observing community. The existing data, however, were far from being homogeneous and were not yet optimized for databases, without framework for data reporting or archival and the data documentation was incomplete. Within the EU FP7 project PAGE 21, Arctic Portal has developed a central Data Management System (DMS) for permafrost monitoring parameters of the Global Terrestrial Network for Permafrost (GTN-P) and others. Each component of the DMS, including parameters, data levels and metadata formats were developed in cooperation with the GTN-P, the International Permafrost Association (IPA) and Arctic Portal. The researcher can now edit, visualize and download standardized datasets, metadata, charts and statistics of all relevant parameters for a specific site in all partner countries. The GTN-P DMS is based on an object oriented model (OOM) following the framework Model/View/Controller (MVC) of Cakephp. It is implemented with open source technologies with the PostGIS database and Geoserver. To ensure interoperability and enable potential inter-database search, the system follows the evolution of the Semantic Web (Linking Geospatial Data); the database structure and content are mapped towards xml, xslt, rdf, and owl. Moreover, metadata comply with the ISO 19115/2 and ISO TC/211 standards for geospatial information. Datasets are then normalized based on a control vocabulary registry. Tools are further developed to provide data processing, analysis capability and quality control. The end of the distribution chain deliver highly structured datasets towards modelers in NetCDF files, format developed by UNIDATA. The elaboration of this project highlights the absence of standardized data model for scientific relational databases as well as a lack of ontology definition and mapping within and between scientific communities.

Description: Arctic permafrost coasts are eroding at rates similar or greater than temperate coasts and release large quantities of organic carbon and nitrogen previously stored in permafrost. Estimates of organic carbon fluxes from ice-rich permafrost coasts of the Laptev Sea, where data is scarce, differ widely with estimates varying by two orders or magnitude. Here, we used high resolution datasets on coastal erosion, cryostratigraphy, organic carbon and geomorphology from the Bykovsky Peninsula, in the southern Laptev Sea, to compute below ground organic carbon and nitrogen pools and fluxes of organic carbon from the coast for the current period and the next hundred years. Frozen deposits of the peninsula contain 141.6 Tg of organic carbon, a number 27% lower than what it would contain if the surface had not been affected by permafrost thaw in the past. An additional 44.0 Tg of organic carbon is contained under the peninsula below current sea level. The current fluxes of organic carbon from the peninsula are estimated at 0.058 Tg C a-1 and future fluxes at 0.067 Tg C a-1, or even at 0.085 Tg C a-1 if below sea level organic carbon stocks are included in the calculation. Extrapolation of these measurements to the entire Yedoma coast of the Laptev Sea gives an maximum annual flux of organic carbon from coastal erosion of 6.95 Tg C a-1, which ranges between the previously published minimum and maximum estimations for the same area.s

Description: Arctic permafrost coasts make up about one third of the global coastline and are likely to witness some of the most dramatic changes linked to changing environmental conditions in the 21st century. Increasing sea level, warming sea temperatures, longer open water season and increasing open-water area all bear the potential to increase the impact on sediment and nutrient pathways in the nearshore zone. In this study, we focus on a well studied location, the Bykovsky Peninsula, southern Laptev Sea, Russia to provide high resolution estimations of organic carbon release from its coastline. We build on recently published datasets from studies related to coastal geomorphology, paleogeography and oceanography, all available at large scale, to map and determine the fluxes of carbon coming from the coast throughout the second half of the twentieth century and to provide prospective numbers on the release of organic carbon in the years to come.

Description: Retrogressive thaw slump are among the most important carbon emitters along the Arctic coastline. Significant increases in their activity in the last 50 years has been demonstrated at multiple locations including Herschel Island. While distribution, size of retrogressive thaw slump and their respective change over time are assessed in a number of projects and publications at the moment, mechanics, spatial and temporal dynamics of retrogressive thaw slumps are still poorly understood. We have performed direct current (2D/3D) and capacitively coupled (2D) resistivity tomography, refraction seismics (2D) and ground penetrating radar (2D). Longitudinal, transverse and 3D measurements were systematically arranged on a series of mega (several hundred meters length) retrogressive thaw slumps. Using the ergodic principle, we compared thaw slumps in an initial, accelerating, climax and decelerating stage and compared them with sites with proven historical activity at 300 years B.P. and with undisturbed sites. We can rely on multiple validation measurements including exposed ice wedge profiling, chemical composition of ice, permafrost augering, ice wedge and tundra C14 dating and a 50 year sequence of air photography. The tomographies display remarkable spatial and temporal thaw slump dynamics in all development stages. Already in the initial stage, the tomographies show a large impact of the shoreline an associated warming at the toe of the slumps often extending several tens of meters inland. This could initiate a destabilisation dynamic starting from the toe rather than headwall of a slump, which contrasts previous hypothesis. In the climax stage, bimodal flows act to transport massive amounts of sediments to the shoreline. We can show that both, the accumulation of deep mud pools and the incision of the gully network has a decadal impact on permafrost distribution and mechanics of the thaw slumps. After the climax stage, deep reaching thermal patterns conditioned by bimodal flows and shoreline activity act to persist over hundreds of years and can be clearly distinct from undisturbed tundra slopes. The results are evaluated using the field evidence of ice wedge profiling, chemical ice data, permafrost augering, dating and air photography. Here we show how the 20-30 m deep reaching geophysical data and associated field surveys, profiles and laboratory data can help to create a better understanding of the temporal and spatial patterns of mega retrogressive thaw slumps and their response to atmospheric and marine forcing.

Description: The northern permafrost region contains approximately 50% of the estimated global below-ground organic carbon pool and more than twice as much as is contained in the current atmos-pheric carbon pool. The sheer size of this carbon pool, together with the large amplitude of predicted arctic climate change im-plies that there is a high potential for global-scale feedbacks from arctic climate change if these carbon reservoirs are desta-bilized. Nonetheless, significant gaps exist in our current state of knowledge that prevent us from producing accurate assess-ments of the vulnerability of the arctic permafrost to climate change, or of the implications of future climate change for global greenhouse gas (GHG) emissions. Specifically: • Our understanding of the physical and biogeochemical processes at play in permafrost areas is still insuffi-cient in some key aspects • Size estimates for the high latitude continental carbon and nitrogen stocks vary widely between regions and research groups. • The representation of permafrost-related processes in global climate models still tends to be rudimentary, and is one reason for the frequently poor perform-ances of climate models at high latitudes. The key objectives of PAGE21 are: • to improve our understanding of the processes affect-ing the size of the arctic permafrost carbon and nitro-gen pools through detailed field studies and monitor-ing, in order to quantify their size and their vulnerability to climate change, • to produce, assemble and assess high-quality datasets in order to develop and evaluate representations of permafrost and related processes in global models, • to improve these models accordingly, • to use these models to reduce the uncertainties in feed-backs from arctic permafrost to global change, thereby providing the means to assess the feasibility of stabili-zation scenarios, and • to ensure widespread dissemination of our results in order to provide direct input into the ongoing debate on climate-change mitigation. The concept of PAGE21 is to directly address these questions through a close interaction between monitor- ing activities, proc-ess studies and modeling on the pertinent temporal and spatial scales. Field sites have been selected to cover a wide range of environmental conditions for the validation of large scale mod-els, the devel- opment of permafrost monitoring capabilities, the study of permafrost processes, and for overlap with existing monitoring programs. PAGE21 will contribute to upgrading the project sites with the objective of providing a measurement baseline, both for process studies and for modeling programs. PAGE21 is determined to break down the traditional barriers in permafrost sciences between observational and model-supported site studies and large-scale climate modeling. Our concept for the interaction between site-scale studies and large-scale modeling is to establish and maintain a direct link be-tween these two areas for developing and evaluating, on all spatial scales, the land-surface modules of leading European global climate models taking part in the Coupled Model Inter-comparison Project Phase 5 (CMIP5), designed to inform the IPCC process. The timing of this project is such that the main scientific results from PAGE21, and in particular the model-based assessments will build entirely on new outputs and results from the CMIP5 Climate Model Intercomparison Project designed to inform the IPCC Fifth Assessment Report. However, PAGE21 is designed to leave a legacy that will en-dure beyond the lifetime of the projections that it produces. This legacy will comprise • an improved understanding of the key processes and parameters that determine the vulnerability of arctic permafrost to climate change, • the production of a suite of major European coupled climate models including detailed and validated repre- sentations of permafrost-related processes, that will reduce uncertainties in future climate projections pro-duced well beyond the lifetime of PAGE21, and • the training of a new generation of permafrost scien-tists who will bridge the long-standing gap between permafrost field science and global climate modeling, for the long-term benefit of science and society.