ALBERT

Description: Exposed stones in sandy sublittoral environments are hotspots for marine biodiversity, especially for benthic communities. The detection of single stones is principally possible using sidescan-sonar (SSS) backscatter data. The data resolution has to be high to visualize the acoustic shadows of the stones. Otherwise, stony substrates will not be differentiable from other high backscatter substrates (e.g., gravel). Acquiring adequate sonar data and identifying stones in backscatter images is time consuming because it usually requires visual-manual procedures. To develop a more efficient identification and demarcation procedure of stone fields, sidescan sonar and parametric echo sound data were recorded within the marine protected area of “Sylt Outer Reef” (German Bight, North Sea). The investigated area (~5.900 km2) is characterized by dispersed heterogeneous moraine and marine deposits. Data from parametric sediment echo sounder indicate hyperbolas at the sediment surface in stony areas, which can easily be exported. By combining simultaneous recorded low backscatter data and parametric single beam data, stony grounds were demarcated faster, less complex and reproducible from gravelly substrates indicating similar high backscatter in the SSS data.

Description: Backscatter mosaics based on a multi-frequency multibeam echosounder survey in the continental shelf setting of the North Sea were compared. The uncalibrated backscatter data were recorded with frequencies of 200, 400 and 600 kHz. The results showed that the seafloor appears mostly featureless in acoustic backscatter mosaics derived from 600 kHz data. The same area surveyed with 200 kHz reveals numerous backscatter anomalies with diameters of 10–70 m deviating between −2 dB and +4 dB from the background sediment. Backscatter anomalies were further subdivided based on their frequency-specific texture and were attributed to bioturbation within the sediment and the presence of polychaetes on the seafloor. While low frequencies show the highest overall contrast between different seafloor types, a consideration of all frequencies permits an improved interpretation of subtle seafloor features.

Description: The study presented here is focused on the assessment of surface elevations derived from CryoSat-2 SARIn level 1b data over the Austfonna ice cap, Svalbard, in 2016. The processing chain that must be applied to the CryoSat-2 waveforms to derive heights is non-trivial, and consists of multiple steps, all requiring subjective choices of methods such as the choice of retracker, geo-relocation, and outlier rejection. Here, we compare six CryoSat-2 level-2 type data sets of surface elevations derived using different SARIn processing chains. These data sets are validated against surface elevation data collected from an airborne laser scanner, during a dedicated CryoSat validation experiment field campaign carried out in April 2016. The flight pattern of the airborne campaign was designed so that elevations were measured in a grid pattern rather than along single lines, as has previously been the standard procedure. The flight grid pattern was chosen to optimize the comparison with the CryoSat-2 SARIn elevation data, the location of which can deviate from nadir by several kilometers due to topography within the satellite footprint. The processing chains behind the six data sets include different outlier/error rejection approaches, and do not produce the same number of data points in our region of interest. To make a consistent analysis, we provide statistics from the validation of both the full data sets from each processing chain, and on only those data that all the six data sets provide a geo-located elevation estimate for. We find that the CryoSat-2 data sets that agree best with the validation data are those derived from dedicated land ice processing schemes. This study may serve as a benchmark for future CryoSat-2 retracker developments, and the evaluation software and data set are made publicly available.

Description: The timing of snowmelt is an important turning point in the seasonal cycle of small Arctic catchments. The TerraSAR-X (TSX) satellite mission is a synthetic aperture radar system (SAR) with high potential to measure the high spatiotemporal variability of snow cover extent (SCE) and fractional snow cover (FSC) on the small catchment scale. We investigate the performance of multi-polarized and multi-pass TSX X-Band SAR data in monitoring SCE and FSC in small Arctic tundra catchments of Qikiqtaruk (Herschel Island) off the Yukon Coast in the Western Canadian Arctic. We applied a threshold based segmentation on ratio images between TSX images with wet snow and a dry snow reference, and tested the performance of two different thresholds. We quantitatively compared TSX- and Landsat 8-derived SCE maps using confusion matrices and analyzed the spatiotemporal dynamics of snowmelt from 2015 to 2017 using TSX, Landsat 8 and in situ time lapse data. Our data showed that the quality of SCE maps from TSX X-Band data is strongly influenced by polarization and to a lesser degree by incidence angle. VH polarized TSX data performed best in deriving SCE when compared to Landsat 8. TSX derived SCE maps from VH polarization detected late lying snow patches that were not detected by Landsat 8. Results of a local assessment of TSX FSC against the in situ data showed that TSX FSC accurately captured the temporal dynamics of different snow melt regimes that were related to topographic characteristics of the studied catchments. Both in situ and TSX FSC showed a longer snowmelt period in a catchment with higher contributions of steep valleys and a shorter snowmelt period in a catchment with higher contributions of upland terrain. Landsat 8 had fundamental data gaps during the snowmelt period in all 3 years due to cloud cover. The results also revealed that by choosing a positive threshold of 1 dB, detection of ice layers due to diurnal temperature variations resulted in a more accurate estimation of snow cover than a negative threshold that detects wet snow alone. We find that TSX X-Band data in VH polarization performs at a comparable quality to Landsat 8 in deriving SCE maps when a positive threshold is used. We conclude that TSX data polarization can be used to accurately monitor snowmelt events at high temporal and spatial resolution, overcoming limitations of Landsat 8, which due to cloud related data gaps generally only indicated the onset and end of snowmelt.

Description: Yedoma—extremely ice-rich permafrost with massive ice wedges formed during the Late Pleistocene—is vulnerable to thawing and degradation under climate warming. Thawing of ice-rich Yedoma results in lowering of surface elevations. Quantitative knowledge about surface elevation changes helps us to understand the freeze-thaw processes of the active layer and the potential degradation of Yedoma deposits. In this study, we use C-band Sentinel-1 InSAR measurements to map the elevation changes over ice-rich Yedoma uplands on Sobo-Sise Island, Lena Delta with frequent revisit observations (as short as six or 12 days). We observe significant seasonal thaw subsidence during summer months and heterogeneous inter-annual elevation changes from 2016–17. We also observe interesting patterns of stronger seasonal thaw subsidence on elevated flat Yedoma uplands by comparing to the surrounding Yedoma slopes. Inter-annual analyses from 2016–17 suggest that our observed positive surface elevation changes are likely caused by the delayed progression of the thaw season in 2017, associated with mean annual air temperature fluctuations.

Description: In this study, we analyze interactions in lake and lake catchment systems of a continuous permafrost area. We assessed colored dissolved organic matter (CDOM) absorption at 440 nm (a(440)CDOM) and absorption slope (S300–500) in lakes using field sampling and optical remote sensing data for an area of 350 km2 in Central Yamal, Siberia. Applying a CDOM algorithm (ratio of green and red band reflectance) for two high spatial resolution multispectral GeoEye-1 and Worldview-2 satellite images, we were able to extrapolate the a(λ)CDOM data from 18 lakes sampled in the field to 356 lakes in the study area (model R2 = 0.79). Values of a(440)CDOM in 356 lakes varied from 0.48 to 8.35 m−1 with a median of 1.43 m−1. This a(λ)CDOM dataset was used to relate lake CDOM to 17 lake and lake catchment parameters derived from optical and radar remote sensing data and from digital elevation model analysis in order to establish the parameters controlling CDOM in lakes on the Yamal Peninsula. Regression tree model and boosted regression tree analysis showed that the activity of cryogenic processes (thermocirques) in the lake shores and lake water level were the two most important controls, explaining 48.4% and 28.4% of lake CDOM, respectively (R2 = 0.61). Activation of thermocirques led to a large input of terrestrial organic matter and sediments from catchments and thawed permafrost to lakes (n = 15, mean a(440)CDOM = 5.3 m−1). Large lakes on the floodplain with a connection to Mordy-Yakha River received more CDOM (n = 7, mean a(440)CDOM = 3.8 m−1) compared to lakes located on higher terraces.

Description: We studied two issues to be considered in the calculation of parameters characterizing sea ice deformation: the effect of uncertainties in an automatically retrieved sea ice drift field, and the influence of the type of drift vector grid. Sea ice deformation changes the local ice mass balance and the interaction between atmosphere, ice, and ocean, and constitutes a hazard to marine traffic and operations. Due to numerical effects, the results of deformation retrievals may predict, e.g., openings and closings of the ice cover that do not exist in reality. We focus specifically on fields of ice drift obtained from synthetic aperture radar (SAR) imagery and analyze the Propagated Drift Retrieval Error (PDRE) and the Boundary Definition Error (BDE). From the theory of error propagation, the PDRE for the calculated deformation parameters can be estimated. To quantify the BDE, we devise five different grid types and compare theoretical expectation and numerical results for different deformation parameters assuming three scenarios: pure divergence, pure shear, and a mixture of both. Our findings for both sources of error help to set up optimal deformation retrieval schemes and are also useful for other applications working with vector fields and scalar parameters derived therefrom.

Description: The relationships between trachytes and peralkaline rhyolites (i.e. pantellerites and comendites), which occur in many continental rift systems, oceanic islands and continental intraplate settings, is unclear. To fill this gap, we have performed phase equilibrium experiments on two representative metaluminous trachytes from Pantelleria to determine both their pre-eruptive equilibration conditions (pressure, temperature, H2O content and redox state) and liquid lines of descent. Experiments were performed in the temperature range 750–950 C, pressure 0 5–1 5 kbar and fluid saturation conditions with XH2O [¼H2O/(H2OþCO2)] ranging between zero and unity. Redox conditions were fixed below the nickel–nickel oxide buffer (NNO). The results show that at 950 C and melt water contents (H2Omelt) close to saturation, trachytes are at liquidus conditions at all pressures. Clinopyroxene is the liquidus phase, being followed by iron-rich olivine and alkali feldspar. Comparison of experimental and natural phases (abundances and compositions) yields the following pre-eruptive conditions: P¼160 5 kbar, T¼925625 C, H2Omelt¼261wt %, and fO2 between NNO– 0 5 and NNO– 2. A decrease in temperature from 950 C to 750 C, as well as of H2Omelt, promotes a massive crystallization of alkali feldspar to over 80 wt %. Iron-bearing minerals show gradual iron enrichment when T and fO2 decrease, trending towards the compositions of the phenocrysts of natural pantellerites. Despite the metaluminous character of the bulk-rock compositions, residual glasses obtained after 80 wt % crystallization evolve toward comenditic compositions, owing to profuse alkali feldspar crystallization, which decreases the Al2O3 of the melt, leading to a consequent increase in the peralkalinity index [PI¼molar (Na2OþK2O)/Al2O3]. This is the first experimental demonstration that peralkaline felsic derivatives can be produced by low-pressure fractional crystallization of metaluminous mafic magmas. Our results show that the pantelleritic magmas of basalt–trachyte–rhyolite igneous suites require at least 95 wt % of parental basalt crystallization, consistent with trace element evidence. Redox conditions, through their effect on Fe–Ti oxide stabilities, control the final iron content of the evolving melt.

Description: Published

Description: 559- 588

Description: 2V. Struttura e sistema di alimentazione dei vulcani

Description: JCR Journal

Description: In permafrost areas, seasonal freeze-thaw cycles result in upward and downward movements of the ground. For some permafrost areas, long-term downward movements were reported during the last decade. We measured seasonal and multi-year ground movements in a yedoma region of the Lena River Delta, Siberia, in 2013–2017, using reference rods installed deep in the permafrost. The seasonal subsidence was 1.7 +- 1.5 cm in the cold summer of 2013 and 4.8 +- 2 cm in the warm summer of 2014. Furthermore, we measured a pronounced multi-year net subsidence of 9.3 +- 5.7 cm from spring 2013 to the end of summer 2017. Importantly, we observed a high spatial variability of subsidence of up to 6 cm across a sub-meter horizontal scale. In summer 2013, we accompanied our field measurements with Differential Synthetic Aperture Radar Interferometry (DInSAR) on repeat-pass TerraSAR-X (TSX) data from the summer of 2013 to detect summer thaw subsidence over the same study area. Interferometry was strongly affected by a fast phase coherence loss, atmospheric artifacts, and possibly the choice of reference point. A cumulative ground movement map, built from a continuous interferogram stack, did not reveal a subsidence on the upland but showed a distinct subsidence of up to 2 cm in most of the thermokarst basins. There, the spatial pattern of DInSAR-measured subsidence corresponded well with relative surface wetness identified with the near infra-red band of a high-resolution optical image. Our study suggests that (i) although X-band SAR has serious limitations for ground movement monitoring in permafrost landscapes, it can provide valuable information for specific environments like thermokarst basins, and (ii) due to the high sub-pixel spatial variability of ground movements, a validation scheme needs to be developed and implemented for future DInSAR studies in permafrost environments.

Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Conservation Physiology 6 (2018): coy049, doi:10.1093/conphys/coy049.

Description: Male baleen whales have long been suspected to have annual cycles in testosterone, but due to difficulty in collecting endocrine samples, little direct evidence exists to confirm this hypothesis. Potential influences of stress or adrenal stress hormones (cortisol, corticosterone) on male reproduction have also been difficult to study. Baleen has recently been shown to accumulate steroid hormones during growth, such that a single baleen plate contains a continuous, multi-year retrospective record of the whale’s endocrine history. As a preliminary investigation into potential testosterone cyclicity in male whales and influences of stress, we determined patterns in immunoreactive testosterone, two glucocorticoids (cortisol and corticosterone), and stable-isotope (SI) ratios, across the full length of baleen plates from a bowhead whale (Balaena mysticetus), a North Atlantic right whale (Eubalaena glacialis) and a blue whale (Balaenoptera musculus), all adult males. Baleen was subsampled at 2 cm (bowhead, right) or 1 cm (blue) intervals and hormones were extracted from baleen powder with methanol, followed by quantification of all three hormones using enzyme immunoassays validated for baleen extract of these species. Baleen of all three males contained regularly spaced peaks in testosterone content, with number and spacing of testosterone peaks corresponding well to SI data and to species-specific estimates of annual baleen growth rate. Cortisol and corticosterone exhibited some peaks that co-occurred with testosterone peaks, while other glucocorticoid peaks occurred independent of testosterone peaks. The right whale had unusually high glucocorticoids during a period with a known entanglement in fishing gear and a possible disease episode; in the subsequent year, testosterone was unusually low. Further study of baleen testosterone patterns in male whales could help clarify conservation- and management-related questions such as age of sexual maturity, location and season of breeding, and the potential effect of anthropogenic and natural stressors on male testosterone cycles.

Description: This work was supported by (1) the Arizona Board of Regents Technology Research Initiative Fund; (2) the Center for Bioengineering Innovation at Northern Arizona University; (3) the Greenland Institute of Natural Resources; (4) the Woods Hole Oceanographic Institution Ocean Life Institute and (5) Fisheries and Ocean Canada’s (DFO) Priorities and Partnership Strategic Initiatives Fund and Oceans Protection Plan.

Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Epigenetics 4 (2018): dvy005, doi:10.1093/eep/dvy005.

Description: There is growing evidence that environmental toxicants can affect various physiological processes by altering DNA methylation patterns. However, very little is known about the impact of toxicant-induced DNA methylation changes on gene expression patterns. The objective of this study was to determine the genome-wide changes in DNA methylation concomitant with altered gene expression patterns in response to 3, 3’, 4, 4’, 5-pentachlorobiphenyl (PCB126) exposure. We used PCB126 as a model environmental chemical because the mechanism of action is well-characterized, involving activation of aryl hydrocarbon receptor, a ligand-activated transcription factor. Adult zebrafish were exposed to 10 nM PCB126 for 24 h (water-borne exposure) and brain and liver tissues were sampled at 7 days post-exposure in order to capture both primary and secondary changes in DNA methylation and gene expression. We used enhanced Reduced Representation Bisulfite Sequencing and RNAseq to quantify DNA methylation and gene expression, respectively. Enhanced reduced representation bisulfite sequencing analysis revealed 573 and 481 differentially methylated regions in the liver and brain, respectively. Most of the differentially methylated regions are located more than 10 kilobases upstream of transcriptional start sites of the nearest neighboring genes. Gene Ontology analysis of these genes showed that they belong to diverse physiological pathways including development, metabolic processes and regeneration. RNAseq results revealed differential expression of genes related to xenobiotic metabolism, oxidative stress and energy metabolism in response to polychlorinated biphenyl exposure. There was very little correlation between differentially methylated regions and differentially expressed genes suggesting that the relationship between methylation and gene expression is dynamic and complex, involving multiple layers of regulation.

Description: This work was supported by the National Institute of Health Outstanding New Environmental Scientist Award to NA (NIH R01ES024915) and Woods Hole Center for Oceans and Human Health [National Institutes of Health (NIH) grant P01ES021923 and National Science Foundation Grant OCE-1314642 to M. Hahn, J. Stegeman, NA and SK].

Description: Author Posting. © The Authors, 2018. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 215 (2018): 1072–1087, doi:10.1093/gji/ggy203.

Description: An earthquake rupture process can be kinematically described by rupture velocity, duration and spatial extent. These key kinematic source parameters provide important constraints on earthquake physics and rupture dynamics. In particular, core questions in earthquake science can be addressed once these properties of small earthquakes are well resolved. However, these parameters of small earthquakes are poorly understood, often limited by available data sets and methodologies. The Incorporated Research Institutions for Seismology Community Wavefield Experiment in Oklahoma deployed ∼350 three-component nodal stations within 40 km2 for a month, offering an unprecedented opportunity to test new methodologies for resolving small earthquake finite source properties in high resolution. In this study, we demonstrate the power of the nodal data set to resolve the variations in the seismic wavefield over the focal sphere due to the finite source attributes of an M2 earthquake within the array. The dense coverage allows us to tightly constrain rupture area using the second moment method even for such a small earthquake. The M2 earthquake was a strike-slip event and unilaterally propagated towards the surface at 90 per cent local S-wave speed (2.93 km s−1). The earthquake lasted ∼0.019 s and ruptured Lc ∼70 m and Wc ∼45 m. With the resolved rupture area, the stress-drop of the earthquake is estimated as 7.3 MPa for Mw 2.3. We demonstrate that the maximum and minimum bounds on rupture area are within a factor of two, much lower than typical stress-drop uncertainty, despite a suboptimal station distribution. The rupture properties suggest that there is little difference between the M2 Oklahoma earthquake and typical large earthquakes. The new three-component nodal systems have great potential for improving the resolution of studies of earthquake source properties.

Description: WF is currently supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship. JM was partially supported by SCEC grant #17177 at Woods Hole Oceanographic Institution. This research was supported by the Southern California Earthquake Center (Contribution No. 8014). SCEC is funded by NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12AC20038.

Description: Author Posting. © The Authors, 2018. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 215 (2018): 942–958, doi:10.1093/gji/ggy316.

Description: Surface waves recorded by global arrays have proven useful for locating tectonic earthquakes and in detecting slip events depleted in high frequency, such as glacial quakes. We develop a novel method using an aggregation of small- to continental-scale arrays to detect and locate seismic sources with Rayleigh waves at 20–50 s period. The proposed method is a hybrid approach including first dividing a large aperture aggregate array into Delaunay triangular subarrays for beamforming, and then using the resolved surface wave propagation directions and arrival times from the subarrays as data to formulate an inverse problem to locate the seismic sources and their origin times. The approach harnesses surface wave coherence and maximizes resolution of detections by combining measurements from stations spanning the whole U.S. continent. We tested the method with earthquakes, glacial quakes and landslides. The results show that the method can effectively resolve earthquakes as small as ∼M3 and exotic slip events in Greenland. We find that the resolution of the locations is non-uniform with respect to azimuth, and decays with increasing distance between the source and the array when no calibration events are available. The approach has a few advantages: the method is insensitive to seismic event type, it does not require a velocity model to locate seismic sources, and it is computationally efficient. The method can be adapted to real-time applications and can help in identifying new classes of seismic sources.

Description: WF is currently supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship. This work was supported by National Science Foundation grant EAR-1358520 at Scripps Institution of Oceanography, UC San Diego.

Description: Author Posting. © The Author(s), 2018. This article is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 214 (2018): 2224–2235, doi:10.1093/gji/ggy201.

Description: The key kinematic earthquake source parameters: rupture velocity, duration and area, shed light on earthquake dynamics, provide direct constraints on stress drop, and have implications for seismic hazard. However, for moderate and small earthquakes, these parameters are usually poorly constrained due to limitations of the standard analysis methods. Numerical experiments by Kaneko and Shearer demonstrated that standard spectral fitting techniques can lead to roughly one order of magnitude variation in stress-drop estimates that do not reflect the actual rupture properties even for simple crack models. We utilize these models to explore an alternative approach where we estimate the rupture area directly. For the suite of models, the area averaged static stress drop is nearly constant for models with the same underlying friction law, yet corner-frequency-based stress-drop estimates vary by a factor of 5–10 even for noise-free data. Alternatively, we simulated inversions for the rupture area as parametrized by the second moments of the slip distribution. A natural estimate for the rupture area derived from the second moments is A = πLcWc, where Lc and Wc are the characteristic rupture length and width. This definition yields estimates of stress drop that vary by only 10 per cent between the models but are slightly larger than the true area averaged values. We simulate inversions for the second moments for the various models and find that the area can be estimated well when there are at least 15 available measurements of apparent duration at a variety of take-off angles. The improvement compared to azimuthally averaged corner-frequency-based approaches results from the second moments accounting for directivity and removing the assumption of a circular rupture area, both of which bias the standard approach. We also develop a new method that determines the minimum and maximum values of rupture area that are consistent with a particular data set at the 95 per cent confidence level. For the Kaneko and Shearer models with 20+ randomly distributed observations and ∼10 per cent noise levels, we find that the maximum and minimum bounds on rupture area typically vary by a factor of two and that the minimum stress drop is often more tightly constrained than the maximum.

Description: This work was supported by USGS NEHRP Award G17AP00029. The research was supported by the Southern California Earthquake Center (SCEC; Contribution No. 8013). SCEC is funded by NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12AC20038. YK was supported by both public funding from the Government of New Zealand and the Royal Society of New Zealand’s Rutherford Discovery Fellowship.

Description: Author Posting. © The Authors, 2018. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 215 (2018): 713–735, doi:10.1093/gji/ggy313.

Description: Gas flux in volcanic conduits is often associated with long-period oscillations known as seismic tremor (Lesage et al.; Nadeau et al.). In this study, we revisit and extend the ‘magma wagging’and ‘whirling’models for seismic tremor, in order to explore the effects of gas flux on the motion of a magma column surrounded by a permeable vesicular annulus (Jellinek & Bercovici; Bercovici et al.; Liao et al.). We find that gas flux flowing through the annulus leads to a Bernoulli effect, which causes waves on the magma column to become unstable and grow. Specifically, the Bernoulli effects are associated with torques and forces acting on the magma column, increasing its angular momentum and energy. As the displacement of the magma column becomes large due to the Bernoulli effect, frictional drag on the conduit wall decelerates the motions of the column, restoring them to small amplitude. Together, the Bernoulli effect and the damping effect contribute to a self-sustained wagging-and-whirling mechanism that help explain the longevity of long-period seismic tremor.

Description: This work was supported by National Science Foundation grants EAR-1344538 and EAR-1645057

Description: Author Posting. © The Authors, 2018. This article is posted here by permission of The Royal Astronomical Society for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 215 (2018): 460–473, doi:10.1093/gji/ggy152.

Description: In this work, we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine-learning techniques. Non-negative matrix factorization is used to determine grain-size end-members from sediment surface samples. Four end-members were found, which well represent the variety of sediments in the study area. A radial basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

Description: This work was funded through DFG Research Center/Cluster of Excellence ‘The Ocean in the Earth System’ and was part of MARUM Research Area SD

Description: Author Posting. © Author(s), 2017. This article is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 212 (2018): 1429–1449, doi:10.1093/gji/ggx488.

Description: We conducted detailed analyses of a global array of trenches, revealing systematic intra- and intertrench variations in plate bending characteristics. The intratrench variations of the Manila and Mariana Trenches were analysed in detail as end-member cases of the relatively young (16–36 Ma) and old (140–160 Ma) subducting plates, respectively. Meanwhile, the intertrench variability was investigated for a global array of additional trenches including the Philippine, Kuril, Japan, Izu-Bonin, Aleutian, Tonga-Kermadec, Middle America, Peru, Chile, Sumatra and Java Trenches. Results of the analysis show that the trench relief (W0) and width (X0) of all systems are controlled primarily by the faulting-reduced elastic thickness near the trench axis (Tme) and affected only slightly by the initial unfaulted thickness (TMe) of the incoming plate. The reduction in Te has caused significant deepening and narrowing of trench valleys. For the cases of relatively young or old plates, the plate age could be a dominant factor in controlling the trench bending shape, regardless the variations in axial loadings. Our calculations also show that the axial loading and stresses of old subducting plates can vary significantly along the trench axis. In contrast, the young subducting plates show much smaller values and variations in axial loading and stresses.

Description: This work was supported by Chinese Academy of Sciences Grants (Y4SL021001, QYZDY-SSW-DQC005, YZ201325 and YZ201534), National Natural Science Foundation of China Grants (91628301, U1606401, 41376063 and 41706056) and HKSAR Research Grant Council Grants (24601515, 14313816).

Description: Past sea ice conditions and open water phytoplankton production were reconstructed from a sediment core taken in Disko Bugt, West Greenland, using the sea ice biomarker IP~25~ and other specific phytoplankton biomarker (i.e., brassicasterol, dinosterol, HBI III) records. Our biomarker record indicates that Disko Bugt experienced a gradual expansion of seasonal sea ice during the last 2.2 kyr. Maximum sea ice extent was reached during the Little Ice Age around 0.2 kyr BP. Superimposed on this longer term trend, we find short-term oscillations in open water primary production and terrigenous input, which may be related to the Atlantic Multidecadal Oscillation and solar activity changes as potential climatic trigger mechanisms. A direct sample-to-sample multiproxy comparison of our new biomarker record with microfossil (i.e., benthic foraminifera, dinocysts, and diatoms) and other geochemical records (i.e., alkenone biomarkers) indicates that different proxies are influenced by the complex environmental system with pronounced seasonal changes and strong oceanographic gradients, e.g., freshwater inflow from the Greenland Ice Sheet. Differences in sea ice reconstructions may indicate that the IP~25~ record reflects only the relatively short sea ice season (spring), whereas other microfossil reconstructions may reflect a longer (spring–autumn) interval.

Description: Using a microprofiler and electrochemical oxygen sensors after Revsbech (1989) in situ oxygen profiles measurements were conducted with a spatial resolution if 100 µm and a temporal resolution of 30 seconds at three stations in Potter Cove in austral summer 2015.

Description: This is a dataset from an in situ experiment at station S2 from the LTER monitoring site HAUSGARTEN, performed in June-July 2013 during Maria S Merian expedition MSM29. The in situ responses of Arctic deep-sea benthos to input of phytodetritus of a diatom (Thalassiosira sp.) as opposed to a coccolithophorid (Emiliania huxleyi) were investigated in incubation chambers of benthic landers. Using 13C and 15N labelled phytodetritus harvested from cultures of these species, we traced the fate of the respective phytodetritus into different parts of the food web (respiration, assimilation by bacteria and infauna 〉250 µm), in a short (4d) and long (14d) term experiment. The benthic landers were lowered to the sea floor, where they enclosed ~ 20cm of sediment and ~10 cm of overlying water. During respectively 4d and 14d, the temperature and concentrations of O2, DIC, 13C-DIC, NHx, NOx, 15N-NH4, 15N-NOx were measured. Upon recovery of the landers, the sediment was retrieved and subsampled in vertical horizons to measure pigment, TOC and TN, 13C-POC and 15N-PN concentrations, pore water concentrations of DIC, 13C-DIC, NHx, NOx, 15N-NH4 and 15N-NOx and the assimilation of 13C in bacterial fatty acids (iC15:0 and aiC15:0) and in fauna 〉 250 µm

Description: We present the first field application of a N2O-based approach to correct for vertical mixing in the estimation of net community production (NCP) from mixed layer O2 measurements. Using new ship-based observations of N2O and biological oxygen saturation anomalies (DeltaO2/Ar) from the Subarctic Northeast Pacific, we provide refined mixed layer NCP estimates across contrasting hydrographic regimes and a comprehensive assessment of the methodological considerations and limitations of the approach. Increased vertical mixing coefficients at the base of the mixed layer, derived using N2O measurements, corresponded with periods of heightened wind speed and coastal upwelling. Corrections were most significant in coastal regions where the vertical supply of low-O2 water can otherwise falsely imply net heterotrophy from negative DeltaO2/Ar measurements. After correcting for the mixing flux, all coastal stations showed autotrophic signatures, with maximum NCP exceeding 100 mmol O2 m-2 day-1 in the spring and summer. Vertical fluxes were lower in off-shelf waters, but often contributed more than 50 % to corrected NCP. At some oceanic stations, however, the co-occurrence of N2O minima and O2 maxima resulted in biased (over-estimated) N2O corrections. Evaluating vertical fluxes in these regions remains a challenge for ship-based studies. Nonetheless, our refined NCP estimates show better coherence with surface chlorophyll, temperature, and mixed layer depth than uncorrected values. Potential mixed layer N2O production introduces some uncertainty in the approach, but errors are likely to be small. Ultimately, this work provides rationale for the adoption of the N2O correction to refine NCP estimates, particularly in coastal waters. Data in this submission include the ancillary components required to replicate all calculations, and conclusions made in the main manuscript.

Description: Arctic treelines are facing a strong temperature increase as a result of recent global warming, causing possible changes in forest extent, which will alter vegetation-climate feedbacks. However, the mode and strength of the response is rather unclear, as potential changes are happening in areas that are very remote and difficult to access, and empirical data are still largely lacking. Here, we assessed the current population structure and genetic differentiation of Larix Mill. tree stands within the northernmost latitudinal treeline reaching ~72° N in the southern lowlands of the Taymyr Peninsula (~100° E). We sampled 743 individuals belonging to different height classes (seedlings, saplings, trees) at eleven locations along a gradient from 'single tree' tundra over 'forest line' to 'dense forest' stands and conducted investigations applying eight highly polymorphic nuclear microsatellites. Results suggest a high diversity within subpopulations (HE=0.826-0.893), coupled, however, with heterozygote deficits in all subpopulations, but pronounced in 'forest line' stands. Overall, genetic differentiation of subpopulations is low (FST=0.005), indicating a region-wide high gene flow, although 'forest line' stands harbour few rare and private alleles, likely indicating greater local reproduction. 'Single tree' stands, located beyond the northern forest line, are currently not involved in treeline expansion, but show signs of a long-term refuge, namely asexual reproduction and change of growth-form from erect to creeping growth, possibly having persisted for thousands of years. The lack of differentiation between the subpopulations points to a sufficiently high dispersal potential, and thus a rapid northward migration of the Siberian arctic treeline under recent global warming seems potentially unconstrained, but observations show it to be unexpectedly slow.

Description: Ground-based spectroscopy measurements acquired systematically within the Toolik Vegetation Grid in the 2015 and 2016 growing seasons and within the Imnavait Vegetation Grid in the 2016 growing season. Data were collected in 68 distinct 1 x 1 m long-term monitoring plots representing five distinct vegetation communities. Spectral measurements were acquired two times throughout the season in 2015 representing peak and late season and three times in 2016 representing early, peak and late season. Data were acquired using a GER 1500 field spectrometer (350-1050 nm; 512 bands, spectral resolution 3 nm, spectral sampling 1.5 nm, and 8! field of view). Spectra were collected under clear weather conditions at the highest solar zenith angle between 10:00 and 14:00 local time. Data were collected at nadir approximately 1 m off the ground resulting in a Ground Instantaneous Field of View (GIFOV) of approximately 15 cm in diameter. Nine point measurements of upwelling radiance (Lup) were collected in 1 x 1 m plots representative of the five vegetation communities and averaged to characterize the spectral variability and to reduce noise. Downwelling radiance (Ldown) was measured as the reflectance from a white Spectralon© plate. Surface reflectance (R) was processed as Lup/Ldown x 100 (0-100%). Reflectance spectra were preprocessed with a Savitzky-Golay smoothing filter (n = 11) and subset to 400-985 nm to remove sensor noise at the edges of the radiometer detector.

Description: Our data, as part of the OISO (Ocean Indien Service d'Observation) campaign, contributes to a better understanding of the physical and biological factors controlling N2 fixation in the Southern Indian Ocean and the French Southern and Antarctic lands during Austral summer January and February 2017. We measured N2 and C fixation as well as NH4+ and NO3- assimilation in 3-6 replicates per station. Additionally, we measured diagnostic pigment concentrations to evaluate phtosynthetic community composition. For pigment analysis 4L water was filtered through 25mm Whatman GF/F filters (pressure drop 〈10kPa). Samples were stored at -80°C until analysis. Pigments were analysed using High Performance Liquid Chromatography (HPLC). Pigment concentration were calculated according to Kilias et al (2013, doi:10.1111/jpy.12109). N2 fixation experiments were carried out in three to six replicates for each station. Incubations were done in pre-acid washed polycarbonate bottles on deck with ambient light conditions. All polycarbonate incubation bottles were rinsed with deionized water, and seawater prior to incubation. We used the combination of the bubble approach (Montoya et al., 1996) and the dissolution method (Mohr et al., 2010, doi:10.1371/journal.pone.0012583) proposed by Klawonn et al. (2015, doi:10.3389/fmicb.2015.00769). Bottles were filled up to capacity to avoid air contamination. Incubations were initialized by adding a 10 ml 15-15N gas bubble. Bottles were gently rocked for 15 minutes. Finally, the remaining bubble was removed to avoid equilibration between gas and aqueous phase. after 24 hours a water subsample was taken to a 12 ml exetainer and preserved with 100 µl HgCl2 solution for later determination of exact 15N-15N concentration. Natural 15N2 was determined using Membrane Inlet Mass Spectrometry (MIMS; GAM200, IPI) for each station. Analysis of 15N2 incorporated was carried out by the Isotopic Laboratory at the UC Davis, California campus. We used stable isotope tracers (15N) to measure dissolved inorganic nitrogen (DIN) assimilation rates. Experiments were initiated by adding a known concentration of 0.05 of K15NO3 and 15NH4Cl for oligotrophic waters of the IO and 0.625 µmol L-1 for HNLC regions in the ACC and PF (Knap et al., 1994, Waite et al., 2007, doi:10.1016/j.dsr2.2006.12.010) to one litre polycarbonate bottles. For C assimilation experiments, we added 20 µmol L-1 of NaH13CO3 to one of each of N2 fixation, NH4+ and NO3- assimilation experiment bottles. For incubation, we followed the same procedure as for N2 fixation experiments. Findings reveal that N2 fixation occurs throughout the whole sampling area up to 55°S latitude. In addition, variations of N2 fiaxation rates between replicates were relatively high indicating a great heterogeneity of the French Southern and Antarctic waters. References: Montoya 1996: Montoya, Joseph P., et al. "A Simple, High-Precision, High-Sensitivity Tracer Assay for N (inf2) Fixation." Applied and environmental microbiology 62.3 (1996): 986-993. Knap et al 1994: Knap, A., Michaels, A., Close, A., Ducklow, H. & Dickson, A. 1994. Protocols for the Joint Global Ocean Flux Study (JGOFS) Core Measurements, JGOFS, Reprint of the IOC Manuals and Guides No. 29. UNESCO, 19, 1.

Description: Lithogenic material such as Saharan dust can be incorporated into organic aggregates and act as ballast, potentially enhancing the marine carbon export via increased sinking velocities of aggregates. We studied the ballasting effects of Saharan dust on the aggregate dynamics in the upwelling region off Cape Blanc (Mauritania). Aggregate formation from a natural plankton community exposed to Saharan dust deposition resulted in higher abundance of aggregates with higher sinking velocities compared to aggregate formation with low dust. This higher aggregate abundance and sinking velocities potentially increased the carbon export 10-fold when the aggregates were ballasted by Saharan dust. After aggregate formation in the surface waters, subsequent sinking through suspended Saharan dust minerals had no influence on aggregate sizes, abundance, and sinking velocities. We found that aggregates formed in the surface ocean off Mauritania were already heavily ballasted with lithogenic material and could therefore not scavenge any additional minerals during their descent. This suggests that carbon export to the deep ocean in regions with high dust deposition is strongly controlled by dust input to the surface ocean while suspended dust particles in deeper water layers do not significantly interact with sinking aggregates.

Description: Ground-based spectroscopy measurements acquired systematically within the Toolik Vegetation Grid in the 2016 growing season. All data were collected in a subset of 1 x 1 m long-term monitoring plots representing three distinct vegetation communities three times representing early, peak and late season. Spectral data were acquired using a GER 1500 field spectrometer (350-1050 nm; 512 bands, spectral resolution 3 nm, spectral sampling 1.5 nm, and 8! field of view). Spectra were collected under clear weather conditions at the highest solar zenith angle between 10:00 and 14:00 local time. Data were collected at nadir approximately 1 m off the ground resulting in a Ground Instantaneous Field of View (GIFOV) of approximately 15 cm in diameter. Nine point measurements of upwelling radiance (Lup) were collected in each plot and averaged to characterize the spectral variability and to reduce noise. Downwelling radiance (Ldown) was measured as the reflectance from a white Spectralon© plate. Surface reflectance (R) was processed as Lup/Ldown x 100 (0-100%). Reflectance spectra were preprocessed with a Savitzky-Golay smoothing filter (n = 11) and subset to 400-985 nm to remove sensor noise at the edges of the radiometer detector. Digital camera data were acquired using a consumer-grade camera (Panasonic DM3 LMX, Japan) approximately 1 m off the ground with a white frame for registration of off nadir images. For detailed definitions of the RGB indices see metadata.docx. Leaves and stems of the dominant vascular species in a subset of the sampled plots were collected at early, peak, and late season for chlorophyll and carotenoid analysis.Samples were placed in porous tea bags and preserved in a silica gel desiccant in an opaque container for up to 3 months until pigment extraction (Esteban et al. 2009, doi:10.1007/s11120-009-9468-5). Each sample was homogenized by grinding with a mortar and pestle. Approximately 1.00 mg (+/- 0.05 mg) of homogenized sample was placed into a vial with 2 ml of dimethylformamide (DMF). Vials were then wrapped in aluminum foil to eliminate any degradation of pigments due to UV light and stored in a fridge (4C) for 24 hrs. Samples were measured into a cuvette prior to spectrophotometric analysis. Bulk pigments concentrations were then estimated using a spectrophotometer measuring absorption at 646.8, 663.8 and 480 nm (Porra et al. 1989, doi:10.1016/S0005-2728(89)80347-0) . Absorbance (A) values at specific wavelengths were transformed into µg/mg concentrations of chlorophyll a, Chla, chlorophyll b, Chlb, total chlorophyll, Chl, carotenoids, Car (for equations see metadata.docx). Pigment concentration was calculated as the average concentration of the dominant species in each plot. mean_"pigment" represents the mean of all biomass from each vegetation community and sd_"pigment" represents the standard deviation of each vegetation community.

Description: Seasonal variations in fluxes of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) and the estimated temperatures based on TEX86 are examined in sinking particles collected using moored sediment traps in the eastern Atlantic upwelling regions. In the equatorial Guinea Basin, GDGT fluxes show a correlation with opal fluxes, implying that GDGTs are mainly transported via aggregation with diatoms. The flux-weighted TEXH86 temperatures derived from particles collected both at 853 m and 3,921 m depth correspond to the water temperature (24.1 °C) of ca. 50 m depth, where nitrate concentration starts to increase, potentially as a consequence of nitrification by Thaumarchaeota. This suggests that nutrient concentrations may affect the depth habitat of Thaumarchaeota, and it determines at which water depth the TEXH86 temperature is recorded. In the coastal upwelling off Namibia, TEXH86 temperatures are similar to satellite-derived sea surface temperature (SST) during the warm season, but the record derived from the trap is delayed relative to the SST by approximately 26 days. Warm biases, however, occur during the cold season, similar to what has previously been observed in the filamentous upwelling region off Cape Blanc. In both coastal upwelling regions, oxygen minimum zones (OMZs) are a common feature, and higher TEX86 values have been found within the OMZs in the water column off Cape Blanc and elsewhere. Thus, contributions from GDGTs produced in OMZs might explain the warmer temperature estimates during the cold season in both regions. We thus conclude that in the eastern Atlantic upwelling system, TEXH86 temperature estimates are influenced by non-thermal factors such as nutrient depth distributions and GDGTs produced in the OMZ. In paleoenvironmental records of TEX86, non-thermal signals have to be considered on regional scales.

Description: Recently, Ponto-Caspian species (i.e. area of Azov, Black and Caspian Seas) have invaded brackish and freshwater habitats of the North and Baltic Seas and the Laurentian Great Lakes in much higher numbers than expected based on shipping frequency and environmental conditions among these regions. Therefore, it has been hypothesized that Ponto-Caspian species may have inherent advantages over other species in colonizing new habitats, or that they are of freshwater origin. To test these hypotheses, we conducted artificial selection experiment on Ponto-Caspian amphipod Pontogammarus maeoticus collected from 10 PSU to evaluate adaptation capacity of this species to different salinities. Our results indicated that selection to lower salinity than that of population's ambient salinity is possible. Though, generation time in lower salinity conditions took slightly longer. On the contrary, selection to higher salinity was unsuccessful. Taking into account the results from this and previous studies and the geological history of the Ponto-Caspian region, we suggest that majority of the Ponto-Caspian relict fauna might be of freshwater origin and lack necessary genetic background for adaptation to fully marine conditions. Further selection studies using more species and populations, as well as molecular techniques, should be conducted to confirm this hypothesis on a broader scale. Consequently, if Ponto-Caspian relict species are of freshwater origin, the perception that they are better colonizers than species from other regions might be inclined by the fact that areas with biggest introduction frequency of nonindigenous species (i.e., shipping ports) are environmentally variable habitats which often include freshwater conditions.

Description: The Kara Sea is an important area for paleo-climatic research since sea ice and brine formation take place on its shelf-two processes inducing supra-regional climatic implications and thereby connecting regional environmental variability with global climatic conditions. To gain information about past sea ice coverage and variations, three sediment cores distributed in the southern and central parts of the marginal Sea were investigated. By applying the sea ice biomarker IP25 and the PIP25 index [phytoplankton biomarker (dinosterol)-IP25 index] post-glacial sea ice variability could be detected in the central Kara Sea (Core BP00-36/4), with most intense sea ice cover between 12.4 and 11.8 ka coinciding with the Younger Dryas (12.9-11.6 ka), and reduced sea ice cover between 10 and 8 ka during the Holocene Thermal Maximum. During the last ~7 ka, increasing sea ice indicators might indicate a Holocene cooling trend, probably induced by declining summer insolation. Furthermore, temporal changes in the fast ice?polynya distribution in the southern Kara Sea were detected: expanding fast ice during the late Holocene and a cyclic short-term Holocene climate variability documented by abrupt changes in the sea ice coverage at the BP00-07/7 core site. Core BP99-04/7 from the Yenisei estuary recorded consistently seasonal sea ice cover since ~9.3 ka, apart from five short phases of fast ice expansion to the core site. The strong influence of river run-off as well as estuary processes might prevent the detection of (short-term) climatic signals at this study site.

Description: Ocean acidification causes an accumulation of CO2 in marine organisms and leads to shifts in acid-base parameters. Acid-base regulation in gill breathers involves a net increase of internal bicarbonate levels through transmembrane ion exchange with the surrounding water. Successful maintenance of body fluid pH depends on the functional capacity of ion-exchange mechanisms and associated energy budget. For a detailed understanding of the dependence of acid-base regulation on water parameters, we investigated the physiological responses of the shore crab Carcinus maenas to 4 weeks of ocean acidification [OA, P(CO2)w = 1800 µatm], at variable water bicarbonate levels, paralleled by changes in water pH. Cardiovascular performance was determined together with extra-(pHe) and intracellular pH (pHi), oxygen consumption, haemolymph CO2 parameters, and ion composition. High water P(CO2) caused haemolymph P(CO2) to rise, but pHe and pHi remained constant due to increased haemolymph and cellular [HCO3-]. This process was effective even under reduced seawater pH and bicarbonate concentrations. While extracellular cation concentrations increased throughout, anion levels remained constant or decreased. Despite similar levels of haemolymph pH and ion concentrations under OA, metabolic rates, and haemolymph flow were significantly depressed by 40 and 30%, respectively, when OA was combined with reduced seawater [HCO3-] and pH. Our findings suggest an influence of water bicarbonate levels on metabolic rates as well as on correlations between blood flow and pHe. This previously unknown phenomenon should direct attention to pathways of acid-base regulation and their potential feedback on whole-animal energy demand, in relation with changing seawater carbonate parameters.

Description: Anthropogenic nutrient enrichment is changing the structure and the function of coastal ecosystems. These coastal zones are transitions between freshwater and marine systems where multiple biogeochemical processes remove, produce and transform organic matter. The extent to which the coastal zone is merely a conduit for terrestrial (allochthonous) organic matter, versus a distinct source of autochthonous organic matter fueled by eutrophication, is unclear. To address this issue, we characterized the freshwater and marine dissolved organic matter (DOM) pools in an eutrophic estuary with a long water residence time (Roskilde Fjord, Denmark) over an annual cycle. We combined elemental, optical (absorbance and fluorescence) and isotopic analyses to obtain insight about the bulk properties of the DOM pool during this period. We also used sediment traps to analyze the changes related to the exchange of organic matter between the particulate (POM) and dissolved (DOM) fractions. The results showed that labile autochthonous DOM from in situ primary production was rapidly transformed to more recalcitrant DOM that accumulated in the estuary despite continuous exchange with the open sea. Also, parts of the POM pool were degraded rapidly (within 24h) and transformed into the DOM pool. Accumulated DOM was characterized by relatively low molecular size and stable carbon isotopic value, and by high protein-like fluorescence. These results indicate that autotrophic material can be a major source of specific recalcitrant DOM in eutrophic coastal waters, contributing significantly to the flux of organic carbon to the ocean.

Description: The high-relief catchment of the Tavignanu River (Corsica Island, France) with an elevation range from sea level to 2622 m above sea level was investigated from January 2016 to April 2017 for its on-site parameters (T, pH, EC, TA), riverine carbon budget (TCO2) and stable carbon isotopes (d13C). Partial pressure of CO2 (pCO2) and annual carbon flux across the air-water boundary (FCO2) were calculated from analytical results. This data set contains the supplementary analytical data of the related publication.

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2016P18 drifting on Antarctic sea ice. The buoy was deployed on multi year ice without drogue during POLARSTERN cruise ANT-XXXI/2 (PS96). The time series describes the position and additional parameters of the buoy between 18 Jan 2016 and 22 Aug 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2015P12 drifting on Arctic sea ice. The buoy was deployed on first year ice without drogue during POLARSTERN cruise ARK-XXIX/3 (PS94). The time series describes the position and additional parameters of the buoy between 02 Sep 2015 and 12 Sep 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2017P24 drifting on Arctic sea ice. The buoy was deployed on first year ice without drogue during POLARSTERN cruise ARK-XXXI/1 (PS106). The time series describes the position and additional parameters of the buoy between 07 Jun 2017 and 21 Jun 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).

Description: Sea ice drift, surface temperature, and barometric pressure were measured by Surface Velocity Profiler 2016P20 drifting on Antarctic sea ice. The buoy was deployed on multi year ice without drogue during POLARSTERN cruise ANT-XXXI/2 (PS96). The time series describes the position and additional parameters of the buoy between 18 Jan 2016 and 09 Jul 2017 in sample intervals of 1 hour. The data set has been processed, including the removal of obvious inconsistencies (missing values).