ALBERT

Description: River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays and important role in the Arctic carbon cycle and its export from land to sea is expected to increase with accelerated permafrost thaw with ongoing climate change. However, transport ways and transformation of DOC is mostly unknown. The absorption coefficient by colored dissolved organic matter (aCDOM) which can be used to estimate DOC concentration. In this study, we compiled DOC and aCDOM samples from 11 expeditions covering river, coastal and offshore waters. Water samples for DOC analysis were filtered through 0.7µm GF/F filter and acidified with 25 µL HCl suprapur (10 M) right after sampling. Samples were stored cool and dark for transport. DOC concentrations were measured using high temperature catalytic oxidation (TOC-VCPH, Shimadzu). Three measurements of each sample were averaged and after each 10 samples, a blank and a standard (Battle-02, Mauri-09 or Super-05 certified reference material from National Laboratory for Environmental Testing, Canada) were measured to sustain a quality control. Samples for aCDOM(λ) analysis were filtered through 0.22 µm Millipore GSWP filters (Gonçalves-Araujo et al., 2015, Lena 2016, Bykovksy 2017) or 0.7 µm Whatman GF/F (LD10, YS11, VB13, VB14, Lena 2014, Lena 2015) right after sampling. 100 ml filtrate was stored cool and dark in amber glass bottles until further analysis. aCDOM(λ) was measured with spectrophotometer (SPECORD 200, Analytik Jena) by measuring the absorbance (Aλ) in 1 nm intervals between 200 and 750 nm. The resulting absorbance measurements were then applied to a standard equation aCDOM (λ)=(2.303*A_λ)/L, where L is the path length (length of cuvette), to calculate the aCDOM(λ). Fresh Milli-Q water was used as reference. The cuvette length varied depending on the expected absorption in the sampled water (1 or 5 cm for river or coastal waters, 5 or 10 cm for offshore shelf waters). Resulting aCDOM spectra were corrected for baseline offsets by subtracting the absorption at 700 nm, assuming zero absorption at 700 nm.

Description: We present a comprehensive inventory of retrogressive thaw slumps (RTS) for six study sites in the Russian High Arctic covering an area of more than 600 km². The sites are located on the Novaya Zemlya Archipelago, Kolguev Island, Bol'shoy Lyakhovsky Island, and Taymyr Peninsula in ice-rich permafrost characterized by either buried glacial ice or syngenetically formed Yedoma permafrost deposits. This data publication contains geospatial polygon vector files of the individual mapped slumps across multiple time slices. The mapping was performed on multispectral imagery of very high-resolution satellite sensors, including PlanetScope (3m ground resolution), RapidEye (5m), Pléiades (0.5m), and SPOT (1.5m). Cloud free images were acquired between 2011 and 2020 and exist for annual or close-to-annual time steps depending on their availability. Additional data sets such as the ArcticDEM, the Esri Satellite base map, and Tasseled Cap Landsat Trends were used to support the mapping process. The identification and digitization of thaw slumps as polygons (in UTM coordinate reference system) was performed in QGIS 10.3. A total number of 3466 individual RTS were mapped between 2011 or 2013 and 2020. In addition, for the coastal slumps, change distances from headwalls and bluff bases were calculated in ArcMap 10.5 using the Digital Shoreline Analysis System (DSAS) tool version 5 over the study period (2011/2013-2020). Very high-resolution imagery for this study was kindly provided by ESA through Third Party Mission proposal TPM4-ID-54054. We recieved access to the RapidEye imagery via the RapidEye Science Archive (RESA) initiative in the scope of our project 'Thaw Dynamics of Retrogressive Thaw Slumps from High Resolution Images in Siberia (RTStrendr )'. The PlanetScope imagery was recieved in the scope of our project ' Artificial Intelligence for Cold Regions (AI-CORE)'.