Description: Permafrost acts as an impermeable subsurface in Arctic lowland landscapes. This hydrological barrier results in carbon-rich, water-saturated soils as well as many ponds and lakes. The rapidly warming Arctic climate very likely will affect the surface inundation in Arctic lowlands due to changes in precipitation, evapotranspiration, and permafrost degradation. Drying and wetting of the surface may occur in different regions and potentially alter the exchange of energy and carbon between the surface and the atmosphere. With increased permafrost thaw, for example, water may drain to deeper soil layers or drainage maybe enhanced due to newly forming drainage networks. Melting ground ice and subsequent inundation, on the other hand, may enhance formation of new ponds and wet areas. The current distribution of ponds and lakes in the Arctic is the result of complex interactions between climate, ground ice volume, topography, age and sediment characteristics. Because lake formation and growth processes occur at spatial scales orders of magnitude below those of the resolution for global or pan-arctic models land surface models, statistical representations of lake size distributions and other properties to inform such processes in future models are needed that can be related to macroscopic landcape properties. This study proposes basic observationally-constrained relationships to enhance the modeling of future Arctic surface inundation. We mapped ponds and lakes in 21 circum-arctic sites representing different permafrost-soil landscapes, i.e., physiographic regions with similar surface geology, regional climate, and biomes. We used high-resolution optical and radar satellite imagery with spatial resolutions of 4 m or better to create detailed water body maps and derive representative probability density functions (PDF). PDFs of ponds and lakes vary little within the same ecoregion. Significant differences, however, do occur between landscapes. We used regional permafrost-soil landscape maps of Alaska, Canada, and Siberia to upscale the water body distributions to the circum-arctic. We here present regional distribution parameters, i.e. pond and lake fractions as well as PDF moments (mean surface area, standard deviation, and skewness) and their uncertainties. Younger landscapes, that developed in the early Holocene exhibit very skewed water body distributions. These landscapes are dominated by many ponds and feature only very few large lakes. Older landscapes, on the other hand, show more larger lakes but also a higher variability in pond and lake size. For lakes smaller than 5*10⁵ m², PDFs change in a regular fashion across all sites: Relationships between mean surface area and standard deviation show a linear behaviour whereas the correlation between mean and skewness log-normal. We hypothesize that these relationships are an expression of pond and lake growth and/or lake formation in the landscapes and discuss the potential of the observed patterns to improve predictions of future distributions of Arctic ponds and lakes.

Description: Ice-rich permafrost that formed in glacial periods of the Quaternary is highly vulnerable to thaw under ongoing climate change and anthropogenic disturbance. Permafrost degradation processes such as thermokarst, thermo-denudation and thermo-erosion are actively shaping modern periglacial landscapes. Retrogressive thaw slumps – also referred to as thermo-cirques – represent a highly dynamic geomorphologic feature in ice-rich permafrost regions. These rapidly forming landforms consist of a steep headwall surrounding a gently inclined slump floor where sediment erosion and accumulation takes place simulatenously and develop as a result of rapid permafrost thaw over several decades. Thaw slumps are commonly found in permafrost areas with near-surface, thick ground-ice layers that are susceptible to thermo-denudation and subsequent mass displacement through cryogenic landslides (Leibman et al., 2008). Thaw slumps are particularly frequent along riverbanks and coastlines in the Northwest American and West Siberian Arctic, where they are typically initiated by lateral erosion of the bluff toe. In these regions, buried glacier ice (massive ground ice) bodies or ice-rich glacial till have been mapped. Given their exceptional size of up to 40 ha in area and 25 m high headwalls, so-called mega slumps in northwestern Canada represent primary terrain destabilization features with different environmental settings than surrounding areas (Lantuit et al., 2012), but are a significant source for sediment and solute delivery to adjacent lakes and streams (Kokelj et al., 2013). However, in East Siberia, retrogressive thaw slumps have been described in the syngenetic Late Pleistocene Ice Complex (Yedoma) permafrost deposits, where massive ice wedges and segregated intrasedimentary ice results in total volumetric ice contents of up to 80-90%. Such retrogressive thaw slumps in syngenetic permafrost were investigated for example on the coastal area of the Dmitry Laptev Strait (Are et al., 2005). However, Yedoma deposits are also found on slopes of the Verkhoyan Mountain Range (Slagoda, 1991) and in valleys of surrounding foothills (Grosse et al., 2007) beyond the Yedoma main distributional range in the coastal lowlands of the Laptev and East Siberian seas. The Batagay mega slump is at least two times larger than any previously described thaw slump, has been discovered near the village of Batagay, and has been the subject of some recent cryostratigraphical analysis (Kunitsky et al 2013). It exposes a profile of Yedoma deposits, reaching a thickness of 7 to 22 m in that area (Slagoda, 1991) and underlying ice-rich periglacial alluvial sand deposits of around 60 m thickness (Kunitsky et al., 2013). The observed rapid development of thermo-denudation at rates of up to 15 m per year, poses the question of whether the larger portions of the entire region between the Verkhoyan and Cherskiy mountain ranges may be more vulnerable to deep and rapid thaw following disturbances such as forest fires or forest clearance. Using a set of historical remote sensing data, Kunitsky et al. (2013) suggest that depression-like structures on the Kirgillyakh-Khatyngnakhskoy Mountain saddle begin in the early 1970s. The initial disturbance causing rapid thermo-denudational development of the Batagay mega thaw slump started at the end of the 1980s. Here we present data from a remote sensing investigation of the mega slump (. in order to assess the planimetric dimensions and its recent expansion rates. We acquired very high resolution satellite imagery from QuickBird, IKONOS, KOMPSAT-2, WorldView-1 and WorldView-2, spanning a timeframe from 2006 to 2014. Aerotriangulation of the entire dataset was performed to ensure consistent co-registration between images. In addition, for terrain correction through ortho-rectification and for volumetric analyses of the entire mega slump, we derived an accurate digital elevation model (DEM) with 2m ground resolution from along and across track WorldView stereo imagery. The height difference between the headwall and the outflow of the slump into the Batagay river is 145 m along a distance of 2300m, while the slump maximum width is 800 m. Our analysis doesn’t show any signs of erosion slowdown along a headwall that is up to 86 m high. Comparison of the DEM with a reconstructed paleo-surface revealed that the slump has carved into the rolling topography to a depth of up to 73 m. The current size of the Batagay mega slump is 〉81 ha, while it had thawed 〉24.2 × 106 m³ of ice-rich permafrost through 2014. This huge amount of sediment released from the slump episodically dams up the Batagay river, forming a large temporary lake which then may discharge catastrophically. Geological on-site investigations and further geomorphometric analyses of this locality in conjunction with inter-annual and seasonal change detection observations will allow relating headwall retreat rates to local and regional controls on mega slump development and will help to identify potential areas susceptible to megaslump formation in non-glaciated regions. References Are, F.E., M.N. Grigoriev, H.-W. Hubberten, & V. Rachold (2005), Using thermoterrace dimensions to calculate the coastal erosion rate, Geo-Marine Letters, 25, 121-126. Grosse, G., L. Schirrmeister, C. Siegert, V.V. Kunitsky, E.A. Slagoda, A.A. Andreev & A.Y. Dereviagyn (2007), Geological and geomorphological evolution of a sedimentary periglacial landscape in Northeast Siberia during the Late Quaternary, Geomorphology, 89(1-2), 25-51. Kokelj, S.V., D. Lacelle, T.C. Lantz, J. Tunnicliffe, L. Malone, I.D. Clark & K.S. Chin (2013), Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales, Journal of Geophysical Research: Earth Surface, 118, 681-692. Kunitsky, V.V., I.I. Syromyatnikov, L. Schirrmeister, Yu.B. Skachkov, G. Grosse, S. Wetterich, & M.N. Grigoriev (2013), Ice-rich permafrost and thermal denudation in the Batagay area - Yana Upland, East Siberia, Kriosfera Zemli (Earth' Cryosphere), 17(1), 56-68. Lantuit, H., W.H. Pollard, N. Couture, M. Fritz, L. Schirrmeister, H. Meyer & H.-W. Hubberten (2012), Modern and Late Holocene Retrogressive Thaw Slump Activity on the Yukon Coastal Plain and Herschel Island, Yukon Territory, Canada, Permafrost and Periglacial Processes, 23(1), 39-51. Leibman, M., A. Gubarkov, A. Khomutov, A. Kizyakov & B. Vanshtein (2008), Coastal processes at the tabular-ground-ice-bearing area, Yugorsky Peninsula, Russia, in: Kane, D.L. and Hinkel, K.M. (eds), Proceedings of the Ninth International Conference on Permafrost, University of Alaska Fairbanks, June 29-July 3 2008, 1037-1042. Slagoda, E. A. (1991), Microstructure of permafrost slope deposits of the Kisilyakh Range, in: Melnikov, P.I. and Popov, A.I. (eds), Denudation in the cryolithozone, 19-29, Nauka, Moscow.