ALBERT

Description: A large amount of organic carbon stored in permafrost soils across the high latitudes is vulnerable to thaw, decomposition and release to the atmosphere as a result of climate warming. This process is anticipated to be a significant positive feedback on future radiative forcing from terrestrial ecosystems to the Earth’s climate system. Here, we describe the development of a geospatial framework designed to characterize permafrost carbon vulnerability in the northern hemisphere. The broadly-defined regional classification is based on a Pan-Arctic spatial representation of the major environmental controls on a) the rate and extent of permafrost degradation and thaw, b) the quantity and quality of soil organic matter stocks, and c) the form of permafrost carbon emissions as CO2 and CH4. The framework was developed by integrating existing spatial data layers describing permafrost and ground ice conditions, bioclimatic zones, and topographic and geographic attributes. The resulting Permafrost Regionalization Map (PeRM) can be used for synthesis studies on permafrost carbon vulnerability, including data representativeness and gap analysis, model-data integration and model benchmarking. The utility of the PeRM framework is demonstrated here through areal density analysis and spatial summaries of existing data collections describing the fundamental components of permafrost carbon vulnerability. We use this framework to describe the spatial representativeness and variability in measurements within and across PeRM regions using observational data sets describing active layer thickness, soil pedons and carbon storage, longterm incubations for carbon turnover rates, and site-level monitoring of CO2 and CH4 fluxes from arctic tundra and boreal forest ecosystems. We then use these regional summaries of the observational data to benchmark the results of a process-based biogeochemical model for its skill in representing the magnitudes and spatial variability in these key indicators. Finally, we are using this framework as a basis for higher-resolution mapping of key regions of particular vulnerability to both press (active layer thickening) and pulse (thermokarst development) disturbances, which is guiding on-going research toward characterizing permafrost degradation and associated vegetation changes through multi-scale remote sensing. Overall, this work provides a critical bridge between the abundant but disordered observational and experimental data collections and the development of higher-complexity process representation of the permafrost carbon feedback in geospatial modeling frameworks.

Description: Yedoma is vulnerable to thawing and degradation under climate warming, which can result in lowering of surface elevations due to thaw subsidence. Quantitative knowledge about elevation changes can help us better understand the freeze-thaw processes of the active layer and yedoma deposits. In this study, we utilize C-band Sentinel-1 InSAR measurements, characterized by frequent sampling, to study the elevation changes over ice-rich yedoma uplands on Sobo-Sise Island, Lena Delta. We observe significant seasonal thaw subsidence during summer months and inter-annual elevation changes from 2016 to 2017. Here, we demonstrate the capability of Sentinel-1 to estimate elevation changes over yedoma uplands. We observe interesting patterns of stronger seasonal thaw subsidence on elevated flat yedoma uplands when compared to surrounding yedoma slopes. Inter-annual analyses from 2016 to 2017 revealed mostly positive surface elevation changes that might be caused by delayed thaw seasonal progression associated with mean annual air temperature fluctuations.

Description: Thermokarst lakes are a characteristic element of arctic permafrost regions and an indicator for their rapid landscape changes. Assessing their dynamics contributes to the understanding of driving processes of change, to the evaluation of impacts on landscape characteristics as well as to the estimation of the impact on the permafrost-related carbon budget. Monitoring thermokarst lake dynamics on the Bykovsky Peninsula, consisting of ice-rich Yedoma deposits, using high resolution remote sensing imagery from 1951 to 2016, revealed a long-term tendency towards lake drainage. Approximately 17% of the 1951 lake area was lost due to coastal erosion or the development of drainage networks. In parallel, coastal erosion driven land loss amounts to 2.3% of the peninsula. We find process interconnections between coastal erosion and lake change, as well as lake change dependency on land elevation in a developed alas-yedoma thermokarst relief.

Description: Thermokarst lakes are typical components of the yedoma-alas dominated relief in the coastal lowlands of North- Eastern Yakutia and formed as a result of thawing Late Pleistocene ice-rich Yedoma Ice Complex (IC) deposits. The aim of our study is to estimate thermokarst lake area changes from the early Holocene onwards based on RS data. The decrease of thermokarst lake area from the early Holocene, taking into account total alas depression areas, is as much as 81-83 %. Modern climate warming has led to a general trend of thermokarst lake area decrease. Lake drainage occurs mostly on elevated sites with high Yedoma IC fraction while lake area increase is typical for low-lying areas with a small Yedoma IC fraction. The area increase of thermokarst ponds on flat, boggy yedoma surfaces indicates ice wedge degradation in response to rising summer air temperatures and precipitation.

Description: The distinguishing feature of permafrost in the Arctic is the presence of a large amount of ice below the earth surface. Thermal degradation and subsequent destabilization of ground ice rich terrain cause thaw subsidence. Because these phenomena are hard to detect, they have received not much attention, despite their potentially global significance through the permafrost carbon feedback and implications for active layer thickness monitoring. Clearly, however, detailed local inventories are required to calibrate regional targeted long and short-term assessments for measuring surface deformation due to permafrost thaw. We analyze time series of repeat terrestrial laser scanning (rLiDAR) for quantification of land surface lowering on a tundra upland in the Teshekpuk Lake Special Area on Alaska´s North Slope. Here, considerable negative surface elevation changes have been detected over two years from 2015 to 2017. Spatial patterns of land elevation changes indicate that ice wedge polygon troughs are particularly prone to subsidence. This highlights the vulnerability of arctic tundra lowlands with ice-rich permafrost close to the surface.

Description: Permafrost soils were characterized first in the field by numerous investigators according to standard soil descriptions and were sampled by depth increment within soil horizon boundaries. Measures of bulk density, C, N, and pH were used to further characterize C and N storage for soil horizons and profiles. Field attributes for organic (Oi, Oe, Oa or L, F, H) horizons, mineral (A, E, B, C) horizons, cryoturbated (jj subscripts with mixtures of organic and mineral matrices), and gleying (subscript g with reduced colors), ice-rich layers (e.g., Wf/Cgfjj, Wf/Oafjj) were examined for differences in C, N, and bulk density. Using the Community Climate System Model (CCSM4) we calculated cumulative distributions of active layer thickness (ALT) under current and future climates. We then superposed physical state over soil horizons to explore how chemical attributes are exposed by progressive thaw. Thawing will likely expose 147 Pg of C with 10 Pg of N by 2050 (representative concentration pathway RCP scenario 4.5) and as much as 436 PgC with 29 PgN by 2100 (RCP 8.5). This represents about 30% and 80% of circumarctic permafrost carbon for yr 2050 (RCP 4.5) and yr 2100 (RCP 8.5) scenarios, respectively. Organic horizons will likely contribute the earliest pulse of CO2 via combustion and decomposition. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems.