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Short sediment cores were taken at six stations in Wismar Bay, southern Baltic Sea (Germany) in May 2019 using a Rumohr-Lot device. Our aim in this study was to investigate the role of diagenetic element fluxes and different fresh water sources, including submarine groundwater discharge, on the water column in the bay. Porewaters were extracted from the sediment cores by applying the rhizon technique at a resolution between 2 and 5 cm. The porewaters were analyzed for major and trace metals and selected nutrients using a ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific), total sulphide by a Specord 40 spectrophotometer (Analytik Jena), dissolved inorganic carbon (DIC) and δ13CDIC using an isotope gas mass spectrometre (MAT 253) coupled to a Gasbench II, and δ18OH2O, and δ2HH2O using a CRDS system (laser cavity-ring-down-spectroscopy, Picarro L2140- I). Sediment cores were further sliced at 2 to 4 cm resolution and each freeze-dried solid subsample was analyzed for contents of total carbon, nitrogen, and sulphur using an Elemental Analyzer (Euro Vector EuroEA 3, 052), inorganic carbon using an Elemental Analyzer multi EA (Analytik Jena), total mercury by a DMA-80 analyzer, and HCl-extractable Pb, Mn and Fe using an ICP-OES (iCAP, 7400, Duo Thermo Fischer Scientific).

Permafrost thaw and ice wedge degradation lead to drastic landscape changes in the permafrost region. With this data set we investigated the cliff retreat of the Sobo-Sise Cliff (SSC), a high ice-bearing yedoma cliff in the Lena River Delta. The 1,660 m long cliff SSC extends from 72°32'34 N / 128°15'59 E to 72°32'06 N / 128°18'21 E and is located on the Sardakhskaya channel, which is one of the main Lena river branches in the Lena River Delta. Erosion rates for the SSC were determined based on satellite images from different sensors (Corona, Hexagon, Landsat, Planet cube-sat) for the period 1965-2018. Cliff front lines were manually digitized and erosion rates were calculated with the Digital Shoreline Analysis System (DSAS) tool (Himmelstoos et al. 2018). The study Fuchs et al. (2020) (doi:10.3389/feart.2020.00336) shows that the up to 27.7 m high SSC erodes in average 15.7 m yr-1 (2015-2018). During the entire observed time period from 1965-2018, the SSC retreated in average 484 m (ranging from 322 - 680 m). This data set compilation consist of three GIS shapefiles with a corresponding metadata file and a table of the mean annual erosion rates of the yedoma SSC for the time periods 1965-1975, 1975-2000, 2000-2005, 2005-2010, 2010-2015, and 2015-2018, as well as the absolute cliff retreat rates over the entire period 1965-2018, which are derived from remote sensing imagery analyzed with the DSAS tool. In addition, the cliff front lines for each investigated time step are provided as well as the separation between yedoma and alas deposits for each time step. Related trend data for this region, based on Landsat trend analysis are available at: doi:10.1594/PANGAEA.884136 (Nitze, 2018).

In July 2017, we collected apparent resistivity data (ohm-m) in a sub-aquatic permafrost environment on the southern coastline of the Bykovsky Peninsula in northeast Siberia. The project goal was to determine the depth to the top of frozen sediment for multiple submerged landscapes. The submerged landscapes included ice-rich Yedoma permafrost, permafrost that had undergone prior thermokarst (Alases), and a former lagoon (i.e. offshore at the lagoon's coastline positions in earlier years). The data was collected with an IRIS Syscal Pro Deep Marine resistivity system that was equipped with a GPS and an echo-sounder to record water depths. The geoelectric cable had an electrode separation of 10 m and the electrodes were arranged in a reciprocal Wenner Schlumberger array. The offset between the first electrode and the boat was approximately 10 m.

During the RV Polarstern expedition PS94, we gathered sediment samples in the Barents Sea and the central Arctic Ocean by deploying both a multiple corer (MUC) and a giant boxcorer (GKG). After retrieval of the MUC or GKG, replicate sediment cores with a visibly intact sediment surface were chosen for further laboratory analysis. The selected cores were brought to the laboratory on board RV Polarstern for further analysis. While data on chlorophyll pigments, total organic carbon, microbial cell numbers and diffusive oxygen uptake rates were taken from the same cores, total oxygen uptake rates were measured in three additional cores.

Concentrations of dissolved methane were determined in the Lena River, a permafrost lake and in Tiksi Bay, from 2016-2018, in summer and under ice. In addition in winter 2017, also the concentration in the ice cores was determined (Magen et al. 2014). For the winter 2017 samples, also the methane oxidation rate was determined with a radiotracer method (Bussmann et al. 2015).

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.

The occurrence of mesoscale eddies that develop suboxic environments at shallow depth (about 40–100 m) has recently been reported for the eastern tropical North Atlantic (ETNA). Their hydrographic structure suggests that the water mass inside the eddy is well isolated from ambient waters supporting the development of severe near-surface oxygen deficits. So far, hydrographic and biogeochemical characterization of these eddies was limited to a few autonomous surveys, with the use of moorings, underwater gliders and profiling floats. In this study we present results from the first dedicated biogeochemical survey of one of these eddies conducted in March 2014 near the Cape Verde Ocean Observatory (CVOO). During the survey the eddy core showed oxygen concentrations as low as 5 µmol kg−1 with a pH of around 7.6 at approximately 100 m depth. Correspondingly, the aragonite saturation level dropped to 1 at the same depth, thereby creating unfavorable conditions for calcifying organisms. To our knowledge, such enhanced acidity within near-surface waters has never been reported before for the open Atlantic Ocean. Vertical distributions of particulate organic matter and dissolved organic matter (POM and DOM), generally showed elevated concentrations in the surface mixed layer (0–70 m), with DOM also accumulating beneath the oxygen minimum. With the use of reference data from the upwelling region where these eddies are formed, the oxygen utilization rate was calculated by determining oxygen consumption through the remineralization of organic matter. Inside the core, we found these rates were almost 1 order of magnitude higher (apparent oxygen utilization rate (aOUR); 0.26 µmol kg−1 day−1) than typical values for the open North Atlantic. Computed downward fluxes for particulate organic carbon (POC), were around 0.19 to 0.23 g C m−2 day−1 at 100 m depth, clearly exceeding fluxes typical for an oligotrophic open-ocean setting. The observations support the view that the oxygen-depleted eddies can be viewed as isolated, westwards propagating upwelling systems of their own, thereby represent re-occurring alien biogeochemical environments in the ETNA.

The ice cover of the Arctic Ocean has been changing dramatically in the last decades and the consequences for the sea-ice associated ecosystem remain difficult to assess. Algal aggregates underneath sea ice have been described sporadically but the frequency and distribution of their occurrence is not well quantified. We used upward looking images obtained by a remotely operated vehicle (ROV) to derive estimates of ice algal aggregate biomass and to investigate their spatial distribution. During the IceArc expedition (ARK-XXVII/3) of RV Polarstern in late summer 2012, different types of algal aggregates were observed floating underneath various ice types in the Central Arctic basins. Our results show that the floe scale distribution of algal aggregates in late summer is very patchy and determined by the topography of the ice underside, with aggregates collecting in dome shaped structures and at the edges of pressure ridges. The buoyancy of the aggregates was also evident from analysis of the aggregate size distribution. Different approaches used to estimate aggregate biomass yield a wide range of results. This highlights that special care must be taken when upscaling observations and comparing results from surveys conducted using different methods or on different spatial scales.

This dataset of ice-penetrating radar IRHs (internal reflecting horizons) which were traced across the ice-penetrating radar surveys conducted in 2018-19 at Little Dome C inthe Dome C region of the East Antarctic Plateau. The data set is associated to publication: Chung, A., et al. (in review). The data was collected during a radar survey conducted in the Antarctic field seasons of 2019-20 using the Little Dome C - Very High Frequency (LDC-VHF) multichannel coherent radar depth sounder developed through a collaboration of The University of Alabama (UA), the University of Copenhagen (CPH) and the Alfred Wegener Institute (AWI). The survey covered Patches A and B of Little Dome C, in order to select the exact drill site for the Beyond EPICA Oldest Ice drilling project. The datasets consists of 12 transects systematically covering Patches A and B with parallel lines, over an area of approximately 5×8 km^2. The dataset contains 19 IRHs, the basal unit horizon and the ice-bedrock interface which were manually traced by Ailsa Chung, using the seismic environment of the Echos software from Paradigm Geophysical. A single file for each IRH is provided in a text file, tab separated format with both depth and two-way travel time. The conversion to depth done using c = 0.1685 m/μs and firn correction of 10 m. The IRHs are provided at approximately 3.5 m resolution. The 19 upper IRHs were linked from LDC to the EDC ice core site using the direct radar transect (profile number 20201012). Ages for IRHs were then calculated by linearly interpolating the EDC age-depth timescale from AICC2012 (Bazin et al., 2013) where the IRHs pass closest to the ice core site. IRH ages (in ka BP - before 1950) and uncertainties are provided in a text file, tab separated format file.

This study aimed at isolating microorganisms associated with the mesopelagic jellyfish Periphylla periphylla collected in Irminger Sea at a depth of 325 m in July 2020. Three different solid cultivation media; Hastings, Marine agar and Wickerham media were used for the isolation of the associated microorganisms. A total of 43 bacteria were isolated from the inner and outer surfaces of the umbrella of P. periphylla, but unfortunately, no fungal strain was isolated. Isolates were further identified by Sanger sequencing of the 16S rRNA gene, and based on phylogenetic distinctiveness (differences in closest relative species according to the nucleotide BLAST), 16 bacteria belonging to 8 different genera were selected and subjected to an OSMAC cultivation regime approach using liquid and solid marine broth and glucose– yeast–malt media. After 7 days of cultivation, cultures were extracted with ethyl acetate and assessed for antimicrobial activity against fish and human pathogens. Based on antimicrobial activity assessment, four most bioactive strains; Polaribacter sp. SU124, Shewanella sp. SU126, Psychrobacter sp. SU143 and Psychrobacter sp. SU137, were prioritized for a comparative and untargeted metabolomics analysis using feature-based molecular networking. These findings highlight the biotechnological potential of P. periphylla-associated microbiota.