Fuchs, Matthias; Sachs, Torsten; Jongejans, Loeka Laura; Strauss, Jens; Hugelius, Gustaf; Frost, Gerald V; Jones, Benjamin; Kokelj, Steve V; Kutzbach, Lars; Nitze, Ingmar; Overduin, Pier Paul; Palmtag, Juri; Ping, Chien-Lu; Pokrovsky, Oleg S; Rivkina, Elizaveta; Runge, Alexandra; Schirrmeister, Lutz; Schwamborn, Georg; Siewert, Matthias Benjamin; Treat, Claire C; Veremeeva, Alexandra; Zubrzycki, Sebastian; Grosse, Guido: Characteristics of Arctic river deltas [dataset]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.968904 (dataset in review),

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In: Fuchs, M et al.: Arctic river delta soil and geospatial data set [dataset bundled publication]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.967651 (dataset in review)

The data set summarizes the input and output data for the study Large stocks of permafrost soil organic carbon and nitrogen in Arctic river deltas (Fuchs et al. in prep.). The data set includes information for 211 Arctic river deltas including the size, water area, permafrost distribution, deposit thickness, sediment volume, soil carbon and soil nitrogen stocks; and was compiled in an analysis based on archived and newly acquired data. The area for each delta (in km2) is based on the geospatial layer (doi:10.1594/PANGAEA.968908), that was created by digitizing the spatial extent of each delta based on available Google Earth images. The area (km2) of the resulting polygon shapefile was calculated using ArcMap 10.6. This simple mapping provided a first-order estimation of the total area covered by Arctic deltas. In our approach, we used a definition of 'Arctic delta' that includes typical prograding deltas but also estuaries and alluvial fans ending in the Arctic Ocean as well as inland deltas. This includes deltas of size >10 km2 and a representative subset of micro deltas (< 10 km2). We set the beginning of a delta as the point where the river channels start to spread and lead independently to the sea and develop a distinct fan. Digitized Arctic deltas therefore include not only deltaic, fluvial deposits in a strict sedimentological definition, but are based on a geographic definition of deltas. The percentage of water bodies for each delta were calculated based on a global surface water layer (Pekel et al. 2016) and include areas, which are covered by water for more than 90% of the time of the ice-free season. The permafrost distribution (in % of area) within each delta was calculated based on the most recent permafrost map (Obu et al. 2019) by intersecting the permafrost distribution layer with the mapped delta land areas. For the estimation of the thickness (m) of delta deposits, we used a correlation between the size of the delta and the deposit thickness that was available from five Arctic deltas. Based on this (linear) correlation we estimated the thickness for all the remaining deltas. This is based on the assumption that larger deltas have a higher sediment load and therefore also a greater thickness of deposits. For the sediment volume (km3), we multiplied the area with the deposit thickness and included the information about water area and permafrost distribution in order to estimate the amount of frozen and non-frozen deposits for each delta. For further information on the deposit thickness estimation, please see Fuchs et al. (in prep.). In combination with the synthesis data set (doi:10.1594/PANGAEA.968906), all the above-mentioned parameters served as input for estimating the total carbon and total nitrogen stocks (Pg) for each of the deltas. Hereby the carbon and nitrogen data were included by bootstrapping. Bootstrapping is a tool to estimate the population statistics by repeatedly (in our case 10,000 repetitions) taking small samples (n=50) with replacement from the population and calculating the median. This allowed us to calculate the total carbon and total nitrogen stocks for permafrost and non-permafrost deposits. For more details on the upscaling of carbon and nitrogen stocks in Arctic deltas, see Fuchs et al. (in prep.).