Description: This data set describes the soil core and sample characteristics from the Ikpikpuk and Fish Creek river delta on the Arctic Coastal Plain in northern Alaska. The collection of the permafrost soil cores and the analysis of the samples are described in Fuchs et al. (2018). Sedimentary and geochemical characteristics of two small permafrost-dominated Arctic river deltas in northern Alaska. This data compilation consists of two data set. The first data set describes the properties of the collected permafrost soil cores from the Ikpikpuk river (IKP) and Fish Creek river (FCR) delta. This includes the coordinates of the nine coring locations, the field measurements of the active- and organic layer thickness at the coring locations, and the length of the collected permafrost core. In addition, soil organic carbon and soil nitrogen stocks and densities derived from the laboratory analyses for the reference depths 0-30 cm, 0-100 cm, 0-150 cm and 0-200 cm are presented in kg C m-2 and in kg C m-3. The second data set provides the raw laboratory data for all the samples of the nine collected permafrost cores in the Ikpikpuk and Fish Creek River Delta. All laboratory analyzes were carried out at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam. The third data set presents the results from the radiocarbon dating of chosen samples from five different permafrost cores. This includes the AMS radiocarbon date and the calibrated age of a sample. In addition, the sediment and organic carbon accumulation rates for the dated samples are included. This data set allows to calculate the total carbon and nitrogen storage in two small Arctic river deltas (IKP and FCR) for the first two meter of soil and enlarges the available permafrost cores for Arctic river delta deposits.

Description: This data set includes the data for the publication Fuchs et al. (2019), Organic carbon and nitrogen stocks along a thermokarst lake sequence in Arctic Alaska, doi:10.1029/2018JG004591. Impacts of successive thermokarst lake stages on soil organic carbon and nitrogen storage, Arctic Alaska. This study combines terrestrial and lacustrine cores to a depth of two meters for a carbon and nitrogen stock estimation in a heavily thermokarst affected study region as well as describes the landscape chronology of the study area which is characterized by multiple drained thermokarst lake basins of different generations. The first data set (doi:10.1594/PANGAEA.895163) includes the raw laboratory data (TOC, TC, TN, C/N) from the permafrost cores collected at the Teshekpuk Lake Area. The data for the lacustrine cores are published on Pangaea and accessible with the link: https://doi.org/10.1594/PANGAEA.864814 (Lenz et al., 2016). All laboratory analyses on the terrestrial cores were carried out at the Alfred Wegener Institute Potsdam. The second data set (doi:10.1594/PANGAEA.895165) presents the carbon (in kg C m-2) and nitrogen (in kg N m-2) stocks for all the collected cores for the reference depths 0-30 cm, 0-100 cm, 0-150 cm, 0-200 cm. This includes terrestrial as well as lacustrine cores. The third data set (doi:10.1594/PANGAEA.895166) includes 19 radiocarbon dates from five different permafrost cores. The samples were analyzed at the Radiocarbon Laboratory in Poznan, Poland with the accelerated mass spectrometry (AMS) dating method (Goslar et al., 2004). In addition to the AMS dates, the radiocarbon dates were calibrated with the Calib 7.1 software into calibrated years before present and organic carbon accumulation rates were calculated for each of the cores (Stuiver & Reimer, 1993; Stuiver et al., 2017). In addition, a shapefile (Landforms_Teshekpuk_Area) is available including drained thermokarst lake basins of different lake stages, thermokarst lakes (〉1 ha), primary surfaces and drainage channels. This landform classification was used in the original study to characterize the chronology of the landscape as well as to calculate landscape carbon and nitrogen stocks.

Description: Here we quantify the abundance and distribution of three primary permafrost region disturbances (PRD; lakes and their dynamics, wildfires, retrogressive thaw slumps) using trend analysis of 30-m resolution Landsat imagery from 1999-2014 and auxiliary datasets. The dataset spans four continental-scale transects in North America (Alaska, Eastern Canada) and Eurasia (Western Siberia, Eastern Siberia), covering 2.3M km² or ~10% of the permafrost region. This data publication contains geospatial vector files (polygons) of the perimeters of PRD. The data are subdivided by PRD type (lakes, wildfire, retrogressive thaw slumps) and further subdivided by study region (T1_WS, T2_ES, T3_AK, T4_EC). T1_WS: Western SIberia T2_ES: Eastern Siberia T3_AK: Alaska T4_EC: Eastern Canada The datasets are documented in detail in the linked document (Nitze_etal_2018: Data Documentation v1.0).

Description: Permafrost-related processes drive regional landscape dynamics in the Arctic terrestrial system. A better understanding of past periods indicative of permafrost degradation and aggradation is important for predicting the future response of Arctic landscapes to climate change. Here, we used a multi-proxy approach to analyze a ~4 m long sediment core from a drained thermokarst lake basin on the northern Seward Peninsula in western Arctic Alaska (USA). Sedimentological, biogeochemistical, geochronological, micropaleontological (ostracoda, testate amoeba) and tephra analyses were used to determine the long-term environmental Early-Wisconsin to Holocene history preserved in our core for Central Beringia. Yedoma accumulation dominated throughout the Early to Late-Wisconsin but was interrupted by wetland formation from 44.5 to 41.5 ka BP. The latter was terminated by deposition of 1 m of volcanic tephra, most likely originating from the South Killeak Maar eruption at about 42 ka BP. Yedoma deposition continued until 22.5 ka BP and was followed by a depositional hiatus in the sediment core between 22.5 and 0.23 ka BP. We interpret this hiatus as due to intense thermokarst activity in the areas surrounding the site, which served as a sediment source during the Late-Wisconsin to Holocene climate transition. The lake forming the modern basin on the upland initiated around 0.23 ka BP, which drained catastrophically in spring 2005. The present study emphasizes that Arctic lake systems and periglacial landscapes are highly dynamic and permafrost formation as well as degradation in Central Beringia was controlled by regional to global climate patterns and as well as by local disturbances.

Description: Permafrost degradation influences the morphology, biogeochemical cycling and hydrology of Arctic landscapes over a range of time scales. To reconstruct temporal patterns of early to late Holocene permafrost and thermokarst dynamics, site-specific palaeo-records are needed. Here we present a multi-proxy study of a 350-cm-long permafrost core from a drained lake basin on the northern Seward Peninsula, Alaska, revealing Lateglacial to Holocene thermokarst lake dynamics in a central location of Beringia. Use of radiocarbon dating, micropalaeontology (ostracods and testaceans), sedimentology (grain-size analyses, magnetic susceptibility, tephra analyses), geochemistry (total nitrogen and carbon, total organic carbon, d13Corg) and stable water isotopes (d18O, dD, d excess) of ground ice allowed the reconstruction of several distinct thermokarst lake phases. These include a pre-lacustrine environment at the base of the core characterized by the Devil Mountain Maar tephra (22 800±280 cal. a BP, Unit A), which has vertically subsided in places due to subsequent development of a deep thermokarst lake that initiated around 11 800 cal. a BP (Unit B). At about 9000 cal. a BP this lake transitioned from a stable depositional environment to a very dynamic lake system (Unit C) characterized by fluctuating lake levels, potentially intermediate wetland development, and expansion and erosion of shore deposits. Complete drainage of this lake occurred at 1060 cal. a BP, including post-drainage sediment freezing from the top down to 154 cm and gradual accumulation of terrestrial peat (Unit D), as well as uniform upward talik refreezing. This core-based reconstruction of multiple thermokarst lake generations since 11 800 cal. a BP improves our understanding of the temporal scales of thermokarst lake development from initiation to drainage, demonstrates complex landscape evolution in the ice-rich permafrost regions of Central Beringia during the Lateglacial and Holocene, and enhances our understanding of biogeochemical cycles in thermokarst-affected regions of the Arctic.

Description: Climatic changes are most pronounced in northern high latitude regions. Yet, there is a paucity of observational data, both spatially and temporally, such that regional-scale dynamics are not fully captured, limiting our ability to make reliable projections. In this study, a group of dynamical downscaling products were created for the period 1950 to 2100 to better understand climate change and its impacts on hydrology, permafrost, and ecosystems at a resolution suitable for northern Alaska. An ERA-interim reanalysis dataset and the Community Earth System Model (CESM) served as the forcing mechanisms in this dynamical downscaling framework, and the Weather Research & Forecast (WRF) model, embedded with an optimization for the Arctic (Polar WRF), served as the Regional Climate Model (RCM). This downscaled output consists of multiple climatic variables (precipitation, temperature, wind speed, dew point temperature, and surface air pressure) for a 10 km grid spacing at three-hour intervals. The modeling products were evaluated and calibrated using a bias-correction approach. The ERA-interim forced WRF (ERA-WRF) produced reasonable climatic variables as a result, yielding a more closely correlated temperature field than precipitation field when long-term monthly climatology was compared with its forcing and observational data. A linear scaling method then further corrected the bias, based on ERA-interim monthly climatology, and bias-corrected ERA-WRF fields were applied as a reference for calibration of both the historical and the projected CESM forced WRF (CESM-WRF) products. Biases, such as, a cold temperature bias during summer and a warm temperature bias during winter as well as a wet bias for annual precipitation that CESM holds over northern Alaska persisted in CESM-WRF runs. The linear scaling of CESM-WRF eventually produced high-resolution downscaling products for the Alaskan North Slope for hydrological and ecological research, together with the calibrated ERA-WRF run, and its capability extends far beyond that. Other climatic research has been proposed, including exploration of historical and projected climatic extreme events and their possible connections to low-frequency sea-atmospheric oscillations, as well as near-surface permafrost degradation and ice regime shifts of lakes. These dynamically downscaled, bias corrected climatic datasets provide improved spatial and temporal resolution data necessary for ongoing modeling efforts in northern Alaska focused on reconstructing and projecting hydrologic changes, ecosystem processes and responses, and permafrost thermal regimes. The dynamical downscaling methods presented in this study can also be used to create more suitable model input datasets for other sub-regions of the Arctic.

Description: Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological and geochemical proxies. Radiocarbon and Pb/Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~ 1,400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the "alder high" that occurred in the region ~ 4.0 cal ka BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were therefore archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.

Description: Lakes are a ubiquitous landscape feature in northern permafrost regions. They have a strong impact on carbon, energy and water fluxes and can be quite responsive to climate change. The monitoring of lake change in northern high latitudes, at a sufficiently accurate spatial and temporal resolution, is crucial for understanding the underlying processes driving lake change. To date, lake change studies in permafrost regions were based on a variety of different sources, image acquisition periods and single snapshots, and localized analysis, which hinders the comparison of different regions. Here we present, a methodology based on machine-learning based classification of robust trends of multi-spectral indices of Landsat data (TM,ETM+, OLI) and object-based lake detection, to analyze and compare the individual, local and regional lake dynamics of four different study sites (Alaska North Slope, Western Alaska, Central Yakutia, Kolyma Lowland) in the northern permafrost zone from 1999 to 2014. Regional patterns of lake area change on the Alaska North Slope (-0.69%), Western Alaska (-2.82%), and Kolyma Lowland (-0.51%) largely include increases due to thermokarst lake expansion, but more dominant lake area losses due to catastrophic lake drainage events. In contrast, Central Yakutia showed a remarkable increase in lake area of 48.48%, likely resulting from warmer and wetter climate conditions over the latter half of the study period. Within all study regions, variability in lake dynamics was associated with differences in permafrost characteristics, landscape position (i.e. upland vs. lowland), and surface geology. With the global availability of Landsat data and a consistent methodology for processing the input data derived from robust trends of multi-spectral indices, we demonstrate a transferability, scalability and consistency of lake change analysis within the northern permafrost region.