Description: Based on the analysis of seafloor topography together with historical, geological and palaeogeographical data obtained from published and archived sources, the position of former Ice Complex (IC) islands has been reconstructed. Within the Laptev Sea shelf and in the western part of the East Siberian Sea shelf, most of these islands have been destroyed by coastal thermal erosion and thermal abrasion during the last thousand years or so. The IC islands were the remnants of the ice-rich syncryogenic freshwater terrestrial deposits (so called IC), which covered most of the arctic coastal plains and the emerged arctic shelf during the Late Pleistocene. At the present time, sandbanks exist at the places of former IC islands. These sandbanks are the subject of intense seafloor thermal abrasion. The approximate rates of seafloor thermal abrasion and the time of complete disappearance of these islands during the last thousand years have been estimated. The rate is different for different islands and for different time intervals. The most common values are between 0.02 and 0.3 m/year. Schematic maps of the former IC islands within the Laptev Sea and western part of the East Siberian Sea shelves have been compiled.

Description: Results of a five-year investigation of permafrost and gas-hydrate stability zone evolution on the Laptev and East Siberia Seas shelf are presented. For investigation of permafrost and gas hydrate stability zone (GHSZ) evolution during the Middle Pleistocene– Holocene (last 400 ka), a palaeo-geographic scenario and numerical model were developed. The model takes into consideration the duration of permafrost agradation and degradation, existence of permafrost temperature zonality, different geological composition and geothermal heat flux in different geological structures etc. Based on the modelling the following conclusions can be made. Both offshore permafrost and GHSZ recently exist from the shoreline till to the upper part of continental slope. Delay of the maximal permafrost thickness relative to the climatic extremes and different evolution of offshore permafrost thickness and GHSZ at different seawater depths is shown.

Description: Thermokarst is the process whereby the thawing of ice-rich permafrost ground causes land subsidence, resulting in development of distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment of the distribution of thermokarst landscapes, defined as landscapes comprised of current thermokarst landforms and areas susceptible to future thermokarst development. At 3.6 × 106 km2, thermokarst landscapes are estimated to cover ∼20% of the northern permafrost region, with approximately equal contributions from three landscape types where characteristic wetland, lake and hillslope thermokarst landforms occur. We estimate that approximately half of the below-ground organic carbon within the study region is stored in thermokarst landscapes. Our results highlight the importance of explicitly considering thermokarst when assessing impacts of climate change, including future landscape greenhouse gas emissions, and provide a means for assessing such impacts at the circumpolar scale.

Description: Thermokarst lakes are abundant and highly dynamic landscape features of permafrost lowland regions in western Alaska and provide important ecosystem services as habitats, hydrological feature, biogeochemical hotspots, and for surface energy budgets. Permafrost in this ca. 300,000 km2 region follows approximately a North to South gradient of spatial continuity from continuous to sporadic permafrost zones, which also affects lakes and their dynamics on various temporal and spatial scales. Climate change in western Alaska has resulted in a significant warming of air and ground temperatures over the last decades and is projected to continue on that trajectory. To characterize the vulnerability of lakes as well as permafrost to climate change in this region, we assessed historic lake changes in major lake districts of western Alaska for the period ca. 1950 to ca. 2015 using various remote sensing approaches within a set of several independently funded studies. In particular, we were interested in the dynamics of lake growth and drainage in relation to permafrost degradation. Our method focused on the analysis of image time series built from the 30-60m resolution Landsat record for the 1970-2015 period. The observation period was further extended by unaltered historic USGS topographic maps that contain hydrology features and are based on aerial photography from ca. 1950. Our remote sensing studies were complemented by permafrost and lake hydrology field studies as well as aerial flights to validate remotely sensed lake drainage events. Additional validation of lake change was conducted locally with high resolution imagery from Spot-5, aerial photographs, and the DigitalGlobe constellation of satellites. Here, we synthesize the core results from these studies. The data was processed in three main categories. First we extracted water bodies from recent (2013-2015) Landsat-8 Observing Land Imager (OLI) images of the entire region using simple pixel threshold methods in ENVITM and compared these with waterbodies digitally extracted with ArcGISTM tools from unaltered historic (ca. 1950) USGS topographic map data to identify hotspots of lake change for the entire 65 year period. Second, we processed Landsat data covering major lake districts in the region from three time periods using an object-based segmentation and classification method specifically designed for lake extraction in eCognitionTM. Third, we applied a robust trend analysis developed with open source software and established image pre-processing algorithms to the entire Landsat-record for several large subregions to derive Tasseled Cap, NDVI, and NDWI land cover indices which are useful for studying annual trends in lake changes. Our findings suggest that a significant portion of lakes in this region has drained over the last decades and that in particular large lakes are vulnerable to disappearance. Initial analyses of relationships of lake drainages with permafrost distribution in the region suggest positive correlations between lake loss and permafrost degradation in much of the region. Our findings highlight that permafrost and lake-rich landscapes in Alaska are already changing rapidly and permanently in a warming world. This set of studies was supported by funding from NASA Carbon Cycle Sciences, NSF Arctic System Sciences, an European Research Council Starting Grant, and the Western Alaska Landscape Conservation Cooperative. Our study of lake dynamics in a thaw vulnerable permafrost landscape affected by climate change highlights the need for continuation of the Landsat mission as well as the increase of observation density with the new ESA Sentinel-2 mission.

Description: The permafrost component of the cryosphere is changing dramatically, but the permafrost region is not well monitored and the consequences of change are not well understood. Changing permafrost interacts with ecosystems and climate on various spatial and temporal scales. The feedbacks resulting from these interactions range from local impacts on topography, hydrology, and biology to complex influences on global scale biogeochemical cycling. This review contributes to this focus issue by synthesizing its 28 multidisciplinary studies which provide field evidence, remote sensing observations, and modeling results on various scales.Wesynthesize study results from a diverse range of permafrost landscapes and ecosystems by reporting key observations and modeling outcomes for permafrost thaw dynamics, identifying feedbacks between permafrost and ecosystem processes, and highlighting biogeochemical feedbacks from permafrost thaw.Wecomplete our synthesis by discussing the progress made, stressing remaining challenges and knowledge gaps, and providing an outlook on future needs and research opportunities in the study of permafrost–ecosystem–climate interactions.

Description: In 1999, the International Permafrost Association (IPA) established the Global Terrestrial Network for Permafrost (GTN-P, gtnp.org). The goal of the network is systematic and long-term documentation of the distribution, variability, and trends of permafrost (an Essential Climate Variable, ECV) based on a global network of field measurements. The two current cryospheric indicators are permafrost temperature and active layer thickness, throughout the Earth’s permafrost regions. The network has been mainly operated by scientist and research institutions and programs. GTN-P developed a Data Management System (gtnpdatabase.org) for the collection, processing (including standardisation), and dissemination of permafrost data and metadata. Recent ground temperature and active layer thickness data are being compiled to provide an update to the current permafrost state. GTN-P is part of the Global Climate Observing System (GCOS) Global Terrestrial Observing System (GTOS). GCOS is a joint undertaking of the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational Scientific and Cultural Organization (UNESCO), the United Nations Environment Programme (UNEP) and the International Council for Science (ICSU). Permafrost temperature measurements, commonly performed with permanently installed multi-thermistor cables in boreholes, enable a good accuracy of 0.1°C. The logger resolution and measurement frequency, however, varies with the type and the depth of the individual borehole. Due to high geomorphological surface and subground dynamics, the relative vertical position of testing probes can change and bias the depth indications of old boreholes in sensitive areas. Most important quality concerns are measurement accuracy, zero annual amplitude depth, data gaps, incomplete time series, and spatial clustering of boreholes. We developed a methodological approach to filter the data by defined quality rules in order to calculate global to regional weighted averages of permafrost temperature anomalies. In this presentation we aim to give an overview on the systematical data pathway from borehole principal investigators over National Correspondents in GTN-P, followed by data processing algorithms in the GTN-P DMS towards quality checked time series data.