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.

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: 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: 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.