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  • 301
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    Biogeography of Deep-Sea Benthic Bacteria at Regional Scale (LTER HAUSGARTEN, Fram Strait, Arctic) (2013)
    PUBLIC LIBRARY SCIENCE
    In:  EPIC3PLoS ONE, PUBLIC LIBRARY SCIENCE, 8(9), pp. e72779, ISSN: 1932-6203
    Details
    Publication Date: 2014-10-07
    Description: Knowledge on spatial scales of the distribution of deep-sea life is still sparse, but highly relevant to the understanding of dispersal, habitat ranges and ecological processes. We examined regional spatial distribution patterns of the benthic bacterial community and covarying environmental parameters such as water depth, biomass and energy availability at the Arctic Long-Term Ecological Research (LTER) site HAUSGARTEN (Eastern Fram Strait). Samples from 13 stations were retrieved from a bathymetric (1,284–3,535 m water depth, 54 km in length) and a latitudinal transect (~ 2,500 m water depth; 123 km in length). 454 massively parallel tag sequencing (MPTS) and automated ribosomal intergenic spacer analysis (ARISA) were combined to describe both abundant and rare types shaping the bacterial community. This spatial sampling scheme allowed detection of up to 99% of the estimated richness on phylum and class levels. At the resolution of operational taxonomic units (97% sequence identity; OTU3%) only 36% of the Chao1 estimated richness was recovered, indicating a high diversity, mostly due to rare types (62% of all OTU3%). Accordingly, a high turnover of the bacterial community was also observed between any two sampling stations (average replacement of 79% of OTU3%), yet no direct correlation with spatial distance was observed within the region. Bacterial community composition and structure differed significantly with increasing water depth along the bathymetric transect. The relative sequence abundance of Verrucomicrobia and Planctomycetes decreased significantly with water depth, and that of Deferribacteres increased. Energy availability, estimated from phytodetrital pigment concentrations in the sediments, partly explained the variation in community structure. Overall, this study indicates a high proportion of unique bacterial types on relatively small spatial scales (tens of kilometers), and supports the sampling design of the LTER site HAUSGARTEN to study bacterial community shifts in this rapidly changing area of the world’s oceans.
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  • 302
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    Baseline characteristics of climate, permafrost and land cover from a new permafrost observatory in the Lena River Delta, Siberia (1998-2011) (2013)
    In:  EPIC3Biogeosciences, 10(3), pp. 2105-2128, ISSN: 1726-4189
    Details
    Publication Date: 2021-07-19
    Description: Samoylov Island is centrally located within the Lena River Delta at 72° N, 126° E and lies within the Siberian zone of continuous permafrost. The landscape on Samoylov Island consists mainly of late Holocene river terraces with polygonal tundra, ponds and lakes, and an active floodplain. The island has been the focus of numerous multidisciplinary studies since 1993, which have focused on climate, land cover, ecology, hydrology, permafrost and limnology. This paper aims to provide a framework for future studies by describing the characteristics of the island's meteorological parameters (temperature, radiation and snow cover), soil temperature, and soil moisture. The land surface characteristics have been described using high resolution aerial images in combination with data from ground-based observations. Of note is that deeper permafrost temperatures have increased between 0.3 to 1.3 °C over the last five years. However, no clear warming of air and active layer temperatures is detected since 1998, though winter air temperatures during recent years have not been as cold as in earlier years. Data related to this article are archived under: http://doi. pangaea.de/10.1594/PANGAEA.806233.
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  • 303
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    Quality and Distribution of Frozen Organic Matter (Old, Deep, Fossil Carbon) in Siberian Permafrost (2013)
    Geophysical Research Abstracts
    In:  EPIC3EGU General Assembly 2013, Vienna, 2013-04-07-2013-04-12Vol. 15, EGU2013-12417-2, 2013, Geophysical Research Abstracts
    Details
    Publication Date: 2019-07-17
    Description: Permafrost deposits constitute a large organic carbon (OC) pool vulnerable to degradation and potential carbon release due to global warming. Permafrost sections along coastal and river bank exposures and subsea cores in northeastern Siberia were studied for organic matter (OM) characteristics and ice content. OM stored in Quaternary permafrost grew, accumulated, froze, partly decomposed, and refroze under different periglacial environments, reflected in specific biogeochemical and cryolithological features. For the studied individual strata (Saalian ice-rich deposits, Pre-Eemian floodplain, Eemian lake deposits, Early to MiddleWeichselian fluvial deposits, Middle Weichselian Yedoma, Late Weichselian Yedoma , Taberites, Holocene cover, Holocene thermokarst, Holocene thermoerosional valley and submerged lagoon and fluvial deposits) OM accumulation, preservation, and distribution are strongly linked to a broad variety of paleoenvironmental factors and specific surface and subsurface conditions before inclusion of OM into the permafrost. OM in permafrost includes twigs, leaves, peat, grass roots, plant detritus, and particulate and dissolved OM. The vertical distribution of total OC (TOC) in exposures varies from 0.1 wt % of the dry sediment in fluvial deposits to 45 wt % in Holocene peats. High TOC, high C/N, and low d13C reflect less decomposed OM accumulated under wet, anaerobic soil conditions characteristic of interglacial and interstadial periods. Glacial and stadial periods are characterized by less variable, low TOC, low C/N, and high d13C values indicating stable environments with reduced bioproductivity and stronger OM decomposition under dryer, aerobic soil conditions. Based on TOC data and updated information on bulk densities, we estimate average OC inventories for different stratigraphic units in northeastern Siberia, ranging from 7 kg C/m3 for Early Weichselian fluvial deposits, to 33 kg C/m3 for Middle Weichselian Yedoma deposits, to 75 kg C/m3 for Holocene peaty deposits. Thus, we present one of the first in-depth studies of the complexity of OM distribution for the upper permafrost (to 100 m depth) in the northeastern Siberian Arctic, indicating that considerable variability of OM distribution between different stratigraphical units, between the same stratigraphical unit at different study sites, and even within stratigraphic units at the same site, are important factors that need to be taken into account in future inventories. Based on our own data and scarce published data on stratigraphical differences and the spatial variation of OC sequestered in late Quaternary permafrost deposits, we believe that knowledge about the quantities and qualities of this potentially significant OM pool is still too limited for extrapolating to larger spatial scales. However, combining TOC and ice content measurements with new bulk density estimates suggests that current carbon inventory values are too high.
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  • 304
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    Organic carbon release from coastal erosion of the Bykovsky Peninsula, Laptev Sea, Russia (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, Austria, 2013-04-08-2013-04-12
    Details
    Publication Date: 2019-07-17
    Description: Arctic permafrost coasts make up about one third of the global coastline and are likely to witness some of the most dramatic changes linked to changing environmental conditions in the 21st century. Increasing sea level, warming sea temperatures, longer open water season and increasing open-water area all bear the potential to increase the impact on sediment and nutrient pathways in the nearshore zone. In this study, we focus on a well studied location, the Bykovsky Peninsula, southern Laptev Sea, Russia to provide high resolution estimations of organic carbon release from its coastline. We build on recently published datasets from studies related to coastal geomorphology, paleogeography and oceanography, all available at large scale, to map and determine the fluxes of carbon coming from the coast throughout the second half of the twentieth century and to provide prospective numbers on the release of organic carbon in the years to come.
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  • 305
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    Temporal and spatial dynamics of mega retrogressive thaw slumps revealed by 2D/3D geophysics and mechanical implications for the pace of coastal thermokarst on Herschel Island, western Canadian Arctic (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, Austria, 2013-04-08-2013-04-12
    Details
    Publication Date: 2019-07-17
    Description: Retrogressive thaw slump are among the most important carbon emitters along the Arctic coastline. Significant increases in their activity in the last 50 years has been demonstrated at multiple locations including Herschel Island. While distribution, size of retrogressive thaw slump and their respective change over time are assessed in a number of projects and publications at the moment, mechanics, spatial and temporal dynamics of retrogressive thaw slumps are still poorly understood. We have performed direct current (2D/3D) and capacitively coupled (2D) resistivity tomography, refraction seismics (2D) and ground penetrating radar (2D). Longitudinal, transverse and 3D measurements were systematically arranged on a series of mega (several hundred meters length) retrogressive thaw slumps. Using the ergodic principle, we compared thaw slumps in an initial, accelerating, climax and decelerating stage and compared them with sites with proven historical activity at 300 years B.P. and with undisturbed sites. We can rely on multiple validation measurements including exposed ice wedge profiling, chemical composition of ice, permafrost augering, ice wedge and tundra C14 dating and a 50 year sequence of air photography. The tomographies display remarkable spatial and temporal thaw slump dynamics in all development stages. Already in the initial stage, the tomographies show a large impact of the shoreline an associated warming at the toe of the slumps often extending several tens of meters inland. This could initiate a destabilisation dynamic starting from the toe rather than headwall of a slump, which contrasts previous hypothesis. In the climax stage, bimodal flows act to transport massive amounts of sediments to the shoreline. We can show that both, the accumulation of deep mud pools and the incision of the gully network has a decadal impact on permafrost distribution and mechanics of the thaw slumps. After the climax stage, deep reaching thermal patterns conditioned by bimodal flows and shoreline activity act to persist over hundreds of years and can be clearly distinct from undisturbed tundra slopes. The results are evaluated using the field evidence of ice wedge profiling, chemical ice data, permafrost augering, dating and air photography. Here we show how the 20-30 m deep reaching geophysical data and associated field surveys, profiles and laboratory data can help to create a better understanding of the temporal and spatial patterns of mega retrogressive thaw slumps and their response to atmospheric and marine forcing.
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  • 306
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    Climatology and Time Series of Surface Meteorology in Nylesund, Svalbard (2013)
    Copernicus Publications
    In:  EPIC3Earth System Science Data, Copernicus Publications, 5, pp. 155-163, ISSN: 1866-3508
    Details
    Publication Date: 2015-03-20
    Description: A consistent meteorological dataset of the Arctic site Ny-Ålesund (11.9°E, 78.9°N) spanning the 18-year-period 1 August 1993 to 31 July 2011 is presented. Instrumentation and data handling of temperature, humidity, wind and pressure measurements are described in detail. Monthly mean values are shown for all years to illustrate the interannual variability of the different parameter. Climatological mean values are given for temperature, humidity and pressure. From the climatological dataset, we also present the time series of annual mean temperature and humidity, revealing a temperature increase of +1.35 K per decade and an increase in water vapor mixing ratio of +0.22 g/kg per decade for the given time period, respectively. With the continuation of the presented measurements, the Ny-Ålesund high resolution time series will provide a reliable source to monitor Arctic change and retrieve trends in the future. The relevant data are provided in high temporal resolution as averages over 5 [1] minutes before [after] 14 July 1998, respectively, placed on the PANGAEA repository (doi:10.1594/PANGAEA.793046). While 6-hourly synoptic observations in Ny-Ålesund by the Norwegian Meteorological Institute reach back to 1974 (Førland et al., 2011), the meteorological data presented here cover a shorter time period, but their high temporal resolution will be of value for atmospheric process studies on shorter time scales.
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  • 307
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    Changing Permafrost in the Arctic and its Global Effects in the 21st Century (PAGE21): A very large international and integrated project to measure the impact of permafrost degradation on the climate system (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, Austria, 2013-05-08-2013-04-12
    Details
    Publication Date: 2019-07-16
    Description: The northern permafrost region contains approximately 50% of the estimated global below-ground organic carbon pool and more than twice as much as is contained in the current atmos-pheric carbon pool. The sheer size of this carbon pool, together with the large amplitude of predicted arctic climate change im-plies that there is a high potential for global-scale feedbacks from arctic climate change if these carbon reservoirs are desta-bilized. Nonetheless, significant gaps exist in our current state of knowledge that prevent us from producing accurate assess-ments of the vulnerability of the arctic permafrost to climate change, or of the implications of future climate change for global greenhouse gas (GHG) emissions. Specifically: • Our understanding of the physical and biogeochemical processes at play in permafrost areas is still insuffi-cient in some key aspects • Size estimates for the high latitude continental carbon and nitrogen stocks vary widely between regions and research groups. • The representation of permafrost-related processes in global climate models still tends to be rudimentary, and is one reason for the frequently poor perform-ances of climate models at high latitudes. The key objectives of PAGE21 are: • to improve our understanding of the processes affect-ing the size of the arctic permafrost carbon and nitro-gen pools through detailed field studies and monitor-ing, in order to quantify their size and their vulnerability to climate change, • to produce, assemble and assess high-quality datasets in order to develop and evaluate representations of permafrost and related processes in global models, • to improve these models accordingly, • to use these models to reduce the uncertainties in feed-backs from arctic permafrost to global change, thereby providing the means to assess the feasibility of stabili-zation scenarios, and • to ensure widespread dissemination of our results in order to provide direct input into the ongoing debate on climate-change mitigation. The concept of PAGE21 is to directly address these questions through a close interaction between monitor- ing activities, proc-ess studies and modeling on the pertinent temporal and spatial scales. Field sites have been selected to cover a wide range of environmental conditions for the validation of large scale mod-els, the devel- opment of permafrost monitoring capabilities, the study of permafrost processes, and for overlap with existing monitoring programs. PAGE21 will contribute to upgrading the project sites with the objective of providing a measurement baseline, both for process studies and for modeling programs. PAGE21 is determined to break down the traditional barriers in permafrost sciences between observational and model-supported site studies and large-scale climate modeling. Our concept for the interaction between site-scale studies and large-scale modeling is to establish and maintain a direct link be-tween these two areas for developing and evaluating, on all spatial scales, the land-surface modules of leading European global climate models taking part in the Coupled Model Inter-comparison Project Phase 5 (CMIP5), designed to inform the IPCC process. The timing of this project is such that the main scientific results from PAGE21, and in particular the model-based assessments will build entirely on new outputs and results from the CMIP5 Climate Model Intercomparison Project designed to inform the IPCC Fifth Assessment Report. However, PAGE21 is designed to leave a legacy that will en-dure beyond the lifetime of the projections that it produces. This legacy will comprise • an improved understanding of the key processes and parameters that determine the vulnerability of arctic permafrost to climate change, • the production of a suite of major European coupled climate models including detailed and validated repre- sentations of permafrost-related processes, that will reduce uncertainties in future climate projections pro-duced well beyond the lifetime of PAGE21, and • the training of a new generation of permafrost scien-tists who will bridge the long-standing gap between permafrost field science and global climate modeling, for the long-term benefit of science and society.
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  • 308
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    Incorporation of uranium in benthic foraminiferal calcite reflects seawater carbonate ion concentration (2013)
    In:  EPIC3Geochemistry, Geophysics, Geosystems, 14(1), pp. 102-111, ISSN: 15252027
    Details
    Publication Date: 2019-07-17
    Description: [1] The chemical and isotopic composition of foraminiferal shells (so-called proxies) reflects the physicochemical properties of the seawater. In current day paleoclimate research, the reconstruction of past seawater carbonate system to infer atmospheric CO2 concentrations is one of the most pressing challenges, and a variety of proxies have been investigated, such as foraminiferal U/Ca. Since in natural seawater and traditional CO2 perturbation experiments the carbonate system parameters covary, it is not possible to determine the parameter of the carbonate system causing, e.g., changes in U/Ca, complicating the use of the latter as a carbonate system proxy. We overcome this problem by culturing the benthic foraminifer Ammonia sp. at a range of carbonate chemistry manipulation treatments. Shell U/Ca values were determined to test sensitivity of U incorporation to various parameters of the carbonate system. We argue that inline image is the parameter affecting the U/Ca ratio and consequently, the partitioning coefficient for U in Ammonia sp., DU. We can confirm the strong potential of foraminiferal U/Ca as a inline image proxy.
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  • 309
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    In situ measurements of snow properties and surface albedo at Kohnen Station, East Antarctic Plateau to improve prognostic snow models (2013)
    In:  EPIC3Snow Grain Size Workshop, Grenoble, France, 2013-04-02-2013-04-05
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    Publication Date: 2019-07-16
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  • 310
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    Was interessiert uns das Wetter bei den Pinguinen? (2013)
    In:  EPIC3Jahresfeier der Naturwissenschaftlich-Technischen Fakultät Siegen, Apollo Theater Siegen, 2013-04-12-2013-04-12
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    Publication Date: 2019-12-03
    Description: Ein Reisebericht aus der Antarktis für Wissenschaftler, Techniker und Menschen mit Fernweh
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  • 311
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    Combined transmission and reflection optical microscopy of ice core sections (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, 2013-04-07-2013-04-12
    Details
    Publication Date: 2019-07-17
    Description: Microstructure analysis of ice cores is vital to understand the processes controlling the flow of ice on the microscale. To quantify the microstructural variability (and thus occurring processes) on centimeter, meter and kilometer scale along deep polar ice cores, a large number of sections has to be analyzed. In the last decade, two different methods have been applied: On the one hand, transmission optical microscopy of thin sections between crossed polarizers yields information on the distribution of crystal c-axes. On the other hand, reflection optical microscopy of polished and controlled sublimated section surfaces allows to characterize the high resolution properties of a single grain boundary, e.g. its length, shape or curvature. Based on a polar and an alpine ice core we applied both methods to the same set of sections. This enables us to combine all information on crystal orientation and (sub-)grain boundaries. In this contribution we introduce the method of combined transmission-polarization and reflection microscopy as well as an image processing framework for processing and matching both image types [T. Binder et al., 2013, Journal of Microscopy, in press]. The information content of both analysis methods is limited and influenced by different types of artifacts. It is exemplary shown how the combination allows to compensate for deficiencies of one method. The gray values in images of the grain boundaries on polished ice core sections are influenced by the duration of surface sublimation and the energy/misorientation of the grain boundaries in the section. By combining these gray values with the misorientation obtained from the corresponding thin section imaged between crossed polarizers we try to validate the information content of gray values on the basis of large data sets. This approach is compared to X-ray Laue diffraction measurements (yielding full crystallographic orientation) which validated the sensitivity of the surface sublimation method [I. Weikusat et al., 2011, Journal of Glaciology, 57, 111-120]. As microscopy in transmission mode acquires volume information and microscopy in reflection mode gains information on the surface, an “optimal” matching of both images contains displacements of grain boundary sites. We try to quantify this inaccuracy which can also be interpreted as orientation of the grain boundary surface in 3D.
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  • 312
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    Shallow Shear Wave Reflection Surveying on Alpine Glaciers – Comparison of Results from Gepatschferner and Colle Gnifetti (2013)
    EAGE
    In:  EPIC3Near Surface Geoscience 2013 – 19th European Meeting of Environmental and Engineering Geophysics, Bochum, Germany, 2013-09-09-2013-09-11Bochum, Germany, EAGE
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    Publication Date: 2019-07-17
    Description: In the summer season 2010, a shallow reflection seismic experiment using the small vibrator source ELVIS was carried out on the overburden firn and ice cover of the Colle Gnifetti, Monte Rosa group, Swiss/Italian Alps. This site is widely used for method testing, since the physical properties of ice are similar to those of polar regions. The unique experiment approved for the first time the shallow high-resolution vibroseis method using P- and S-waves for seismic targets on firn and ice masses at least to nearly 60 m depth. As a consequence of this successful experiment, the method was subsequently applied in April 2012 on the Gepatschferner, a glacier in the Austrian Alps, using S-waves only. In contrast to the commonly planted receivers at Colle Gnifetti, a land streamer modified for snow application was used as receiver system. The source was slightly modified by a ski to support operation on soft snow. The recorded data at Gepatschferner achieved clear reflections from the ice base boundary in nearly 150 m depth and from the glacier bed below.
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  • 313
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    Reexamination of atmospheric drag coefficients used in climate models for Arctic summer conditions (2013)
    In:  EPIC3EGU General Assembly, Vienna, Austria, 2013-04-07-2013-04-12
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    Publication Date: 2019-07-16
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  • 314
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    The mean function provides robustness to linear inverse modelling flow estimation in food webs: A comparison of functions derived from statistics and ecological theories (2013)
    ELSEVIER SCIENCE BV
    In:  EPIC3Ecological Modelling, ELSEVIER SCIENCE BV, 258, pp. 53-64, ISSN: 0304-3800
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    Publication Date: 2019-07-16
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  • 315
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    Mezoscale modelling of cold-air outbreaks over the marginal sea ice zone in the Arctic (2013)
    In:  EPIC3EGU General Assembly, 2013-04-07-2013-04-12
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    Publication Date: 2019-07-16
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  • 316
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    Data table to: Brachiopods in Early Carboniferous (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 317
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    Regional variability in eukaryotic protist communities in the Amundsen Sea (2013)
    CAMBRIDGE UNIV PRESS
    In:  EPIC3Antarctic Science, CAMBRIDGE UNIV PRESS, 25(6), pp. 741-751, ISSN: 0954-1020
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    Publication Date: 2019-07-16
    Description: We determined the composition and structure of late summer eukaryotic protist assemblages along a west–east transect in the Amundsen Sea. We used state-of-the-art molecular approaches, such as automated ribosomal intergenic spacer analysis (ARISA) and 454-pyrosequencing, combined with pigment measurements via high performance liquid chromatography (HPLC) to study the protist assemblage. We found characteristic offshore and inshore communities. In general, total chlorophyll a and microeukaryotic contribution were higher in inshore samples. Diatoms were the dominant group across the entire area, of which Eucampia sp. and Pseudo-nitzschia sp. were dominant inshore and Chaetoceros sp. was dominant offshore. At the most eastern station, the assemblage was dominated by Phaeocystis sp. Under the ice, ciliates showed their highest and haptophytes their lowest abundance. This study delivers a taxon detailed overview of the eukaryotic protist composition in the Amundsen Sea during the summer 2010.
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  • 318
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    Assimilation of dynamic topography in a global model (2013)
    In:  EPIC3EGU General Assembly, April 8 - 12, 2013, Vienna, Austria (Geophysical Research Abstracts, Vol. 15, EGU2013-10271)
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    Publication Date: 2019-07-16
    Description: Absolute dynamic topography, i.e. the difference between time dependent multi-mission altimetric sea surface height and one of the most recent GOCE and GRACE based geoids, is assimilated in a global ocean general circulation model. To this end we apply an ensemble based Kalman technique, the "Error Subspace Transform Kalman Filter" (ESTKF). Here we present an update of our work. First of all the geoid is improved over previous versions. The ocean model now includes better dynamics and full sea-ice ocean interactions and more realistic surface forcing. Finally the assimilation method is augmented by a fixed lag smoother technique. This smoother allows to significantly improve the model performance, most strikingly in the first adjustment phase.
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  • 319
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    On the impact of nonlinearity on ensemble smoothing (2013)
    In:  EPIC3EGU General Assembly, April 8 - 12, 2013, Vienna, Austria (Geophysical Research Abstracts, Vol. 15, EGU2013-1981)
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    Publication Date: 2019-07-17
    Description: Ensemble smoothing can be used as a cost-efficient addition to ensemble square root Kalman filters to improve a reanalysis in data assimilation. To correct a past state estimate, the smoother utilizes the cross-covariances between the filtered state ensemble at the present time and a past ensemble at the time where the smoothing is performed. Using the cross-covariances relies on the assumption that the dynamics of the system under consideration are linear. For nonlinear models, it can be expected that the smoothing is suboptimal.We discuss the influence of nonlinearity on the performance of ensemble smoothing based on numerical experiments with the Lorenz-96 model and a realistic ocean circulation model. The experiments show that there exists an optimal smoothing time interval (lag), which depends on the strength of the nonlinearity. For very long lags, the smoothing can result in a deterioration of the state estimate compared to the filtered result. In the case of multivariate assimilation, different fields show distinct optimal smoother lags. In practice, one will have to choose either a compromise for all fields, or one needs to smooth over different lags specific for each field.
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  • 320
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    From mid to high latitudes: marine litter research at the Alfred Wegener Institute (AWI) (2013)
    In:  EPIC3International Conference on Prevention and Management of marine Litter in European Seas, Berlin, 2013-04-10-2013-04-12
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    Publication Date: 2014-10-07
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  • 321
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    Physical properties of meteoric and marine ice in Larsen C Ice Shelf, Antarctic Peninsula, from Q and AVA analyses of reflection seismic data (2013)
    In:  EPIC3EGU General Assembly 2013
    Details
    Publication Date: 2019-07-17
    Description: We present initial estimates of the physical properties of meteoric and marine ice in Larsen C ice shelf, Antarctic Peninsula, as derived from quality factor (Q) and amplitude-versus-angle (AVA) analysis of reflection-seismic datasets. The data were acquired during the 2008-09 austral summer in the south-eastern sector of the ice shelf, using explosive sources deployed in shallow shot holes, and 48 vertical-component 100 Hz geophones. 24 of these phones were installed horizontally and transverse to the acquisition line, such that compressional (P), verticallypolarised shear (SV) and horizontally-polarised shear (SH) could be recorded. The recorded data are rich in reflection events, with different phases identifiable as primary and multiple P-waves, SV- and SH-waves, and also P to SV mode conversions. The AVA character of these reflections is applied in a joint inversion, with a Bayesian statistical analysis used to obtain best-fit densities and wavelet velocities for the meteoric and marine ice, which allows estimates of the ices’ Young’s moduli and Poisson’s ratios. We further use prestack Q inversion (PSQI) to determine P- and S-wave quality factors for the two ice types, and consider these in terms of ice temperature and permeability. Our estimates of the physical properties of the meteoric and marine ices will ultimately be used to inform predictive models of the flow and fracture mechanics of Larsen C Ice Shelf.
    Repository Name: EPIC Alfred Wegener Institut
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    Quantification of ikaite in Antarctic sea ice (2013)
    In:  EPIC3Antarctic Science, 25(3), pp. 421-432, ISSN: 0954-1020
    Details
    Publication Date: 2019-07-17
    Description: Calcium carbonate precipitation in sea ice is thought to potentially drive significant CO2 uptake by the ocean. However, little is known about the quantitative spatial and temporal distribution of CaCO3 within sea ice, although it is hypothesized that high quantities of dissolved organic matter and/or phosphate (common in sea ice) may inhibit its formation. In this quantitative study of hydrous calcium carbonate as ikaite, sea ice cores and brine samples were collected from pack and land fast sea ice between September and December 2007 during two expeditions, one in the East Antarctic sector and the other off Terre Ade´lie. Samples were analysed for CaCO3, salinity, dissolved organic carbon/nitrogen, inorganic phosphate, and total alkalinity. No relationship between these parameters and CaCO3 precipitation was evident. Ikaite was found mostly in the uppermost layers of sea ice with maximum concentrations of up to 126 mg ikaite per litre melted sea ice being measured, although both the temporal and horizontal spatial distributions of ikaite were highly heterogeneous. The precipitate was also found in the snow on top of the sea ice at some of the sampling locations.
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    Sea ice motion and open water area at the Ronne Polynia, Antarctica: Synthetic aperture radar observations versus model results (2013)
    AMER GEOPHYSICAL UNION
    In:  EPIC3Journal of Geophysical Research-Oceans, AMER GEOPHYSICAL UNION, 118, ISSN: 0148-0227
    Details
    Publication Date: 2017-01-20
    Description: This study deals with observations and simulations of the evolution of coastal polynias focusing on the Ronne Polynia. We compare differences in polynia extent and ice drift patterns derived from satellite radar images and from simulations with the Finite Element Sea Ice Ocean Model, employing three atmospheric forcing data sets that differ in spatial and temporal resolution. Two polynia events are analyzed, one from austral summer and one from late fall 2008. The open water area in the polynia is of similar size in the satellite images and in the model simulations, but its temporal evolution differs depending on katabatic winds being resolved in the atmospheric forcing data sets. Modeled ice drift is slower than the observed and reveals greater turning angles relative to the wind direction in many cases. For the summer event, model results obtained with high-resolution forcing are closer to the drift field derived from radar imagery than those from coarse resolution forcing. For the late fall event, none of the forcing data yields outstanding results. Our study demonstrates that a dense (1–3 km) model grid and atmospheric forcing provided at high spatial resolution ( 〈 50 km) are critical to correctly simulate coastal polynias with a coupled sea-ice ocean model.
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    Interannual to decadal variability in a FESOM model setup, model data comparison of LSW layer thicknesses (2013)
    In:  EPIC3European Geosciences Union General Assembly 2013, Vienna, Austria, 2013-04-08-2013-04-12
    Details
    Publication Date: 2019-07-17
    Description: The climate in the Atlantic region is essentially influenced by the Atlantic meridional overturning circulation (AMOC) which carries warm waters into northern latitudes and returns cold deep water southward across the equator. In the Labrador Sea basin a major component of the cold limb of the Atlantic meridional overturning circulation (AMOC) is formed. The intermediate water mass that is part of this deep convection process is the Labrador Sea Water (LSW) which can be separated into two different classes: the deep LSW (dLSW) and the less dense upper LSW (uLSW). Both LSW modes are formed by convection, accompanied by a strong surface cooling during winter conditions, which leads to an increase in the near-surface density and to an unstable stratification and a homogenization of the water column. In this study we simulated the deep-water formation in the Labrador Sea using the Finite-Element Sea-Ice Ocean Model (FESOM) in a global model setup with regional focus on the Labrador Sea and Greenland Sea. We evaluated the capability of the model setup to reproduce a realistic deep water formation in the Labrador Sea by analyzing the modeled Labrador Sea hydrography and we compared the modeled and observational derived dLSW and uLSW layer thicknesses for the time interval 1958-2007. It is shown that the model is able to reproduce different phases in the temporal evolution of the potential density, temperature and salinity, which are known in observational data. Based on composite maps of the thermal and haline contributions to the surface density flux we can prove that the central Labrador Sea in the model is dominated by the thermal contributions of the surface density flux, while the haline contributions are limited to the branch of the Labrador Sea Boundary Current system, where they are dominated from the haline contributions of sea ice melting and formation. Our model results feature a shielding of the central Labrador Sea from the haline contributions by the Labrador Sea Boundary Current system. Furthermore we investigated modes of interannual to decadal variability for the period 1958-2004 and attributed the general variability in the model to the atmospheric forcing and to internal modes of the ocean system. Based on a North Atlantic Deep Water (NADW) index defined for a normal and random forced FESOM run, where the interannual to decadal atmospheric variability in the random forced run is replaced by white noise, we identify modes of interannual to quasi-decadal variability of 7yr and 14yr, respectively. The origin of the 14yr variability is attributed to the atmospheric forcing, while the 7yr variability is linked to internal modes of the ocean. To further isolate the horizontal, but also the vertical variability in the model, we apply a principal oscillation pattern analysis in a three dimensional context. Two exceptional stable interannual modes are captured by the POP analysis and their variability is attributed to a propagating Rossby wave structure.
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    Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands (2013)
    MDPI
    In:  EPIC3Remote Sensing. 2013; 5(4):-., MDPI, 5(4), pp. 1498-1523
    Details
    Publication Date: 2019-07-16
    Description: Water bodies are ubiquitous features in Arctic wetlands. Ponds, i.e., waters with a surface area smaller than 104 m2, have been recognized as hotspots of biological activity and greenhouse gas emissions but are not well inventoried. This study aimed to identify common characteristics of three Arctic wetlands including water body size and abundance for different spatial resolutions, and the potential of Landsat-5 TM satellite data to show the subpixel fraction of water cover (SWC) via the surface albedo. Water bodies were mapped using optical and radar satellite data with resolutions of 4mor better, Landsat-5 TM at 30mand the MODIS water mask (MOD44W) at 250m resolution. Study sites showed similar properties regarding water body distributions and scaling issues. Abundance-size distributions showed a curved pattern on a log-log scale with a flattened lower tail and an upper tail that appeared Paretian. Ponds represented 95% of the total water body number. Total number of water bodies decreased with coarser spatial resolutions. However, clusters of small water bodies were merged into single larger water bodies leading to local overestimation of water surface area. To assess the uncertainty of coarse-scale products, both surface water fraction and the water body size distribution should therefore be considered. Using Landsat surface albedo to estimate SWC across different terrain types including polygonal terrain and drained thermokarst basins proved to be a robust approach. However, the albedo–SWC relationship is site specific and needs to be tested in other Arctic regions. These findings present a baseline to better represent small water bodies of Arctic wet tundra environments in regional as well as global ecosystem and climate models.
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    ‘Adaptive cycles’ and climate fluctuations: a case study from Linear Pottery Culture in western Central Europe (2013)
    Elsevier
    In:  EPIC3Journal of Archaeological Science, Elsevier
    Details
    Publication Date: 2017-06-14
    Description: Linear Pottery Culture (LBK) are investigated. These are interpreted as resulting from a combination of internal socio-economic processes as well as external environmental parameters. Resilience theory is helpful in understanding periods of increased vulnerability and inherent trends to social complexity. Cycles and threshold levels also help to understand why societies experience periods of increasing fragility and subsequent decline. Results are based on the correlation of a typology and dendrochronology-based archaeological chronology for western LBK and various palaeoclimatic proxy-data. The 14C-production curve is taken as an indicator for solar activity fluctuations, and an age model for laminated sediments as an indicator for rainfall fluctuations. We currently consider this correlation as agreeably robust; however future finedating may result in slight shifts within the archaeological chronology. According to the applied age model, the simple farming societies of the LBK (5600e4900 cal BC) in west-central Europe were not immediately and devastatingly affected by most climate fluctuations. Yet, they might have been one destabilising component within broader processes. However, periods of decreased or irregularly spaced rainfall are contemporaneous to periods of population decline, while periods of increased rainfall may have favoured population growth. Towards the end of the 6th millennium cal BC, the final years of LBK in western Central Europe are contemporaneous to a general trend to less rainfall punctuated by short-term increases in precipitation. During this climatically highly volatile period LBK reaches its highest population rates and at the same time experiences a period of warfare. Thereafter population rates decline and LBK gradually vanishes from the archaeological record, being replaced by Middle Neolithic societies.
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    SOCAT Vx - description (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2017-08-31
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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    Updating benchtop sequencing performance comparison (2013)
    In:  EPIC3Nature Biotechnology, 31, pp. 294-296
    Details
    Publication Date: 2019-07-16
    Description: In April 2012, your journal published a study by Loman et al.1 that systematically compared desktop next-generation sequencers (NGS) from three instrument providers. Using the custom scripts supplied by the authors, the same software and the same draft genome (with 153 remaining gaps within several scaffolds) as the reference, we reproduced their results with their data of the enterohemorrhagic Escherichia coli (EHEC) strain found in the 2011 outbreak in Germany. However, we wish to bring readers’ attention to some shortcomings in the report from Loman et al.1, focusing particularly on its discussion of read-level error analysis. NGS is a rapidly changing market, which clearly complicates the comparisons such as that made by Loman et al. Since the original study1, Illumina (San Diego) has launched the MiSeq sequencer officially and has released Nextera library construction kits and 2 × 250–base-pair (250-bp) paired-end (PE) sequencing chemistry. Furthermore, Life Technologies (Carlsbad, California), has made 200-bp and 300-bp kits available for the Ion Torrent Personal Genome Machine (PGM). Roche (Basel, Switzerland) has updated the Sequencing System software for its 454 GS Junior (GSJ) from version 2.6 to 2.7. In this report, we provide an up-to-date snapshot of how benchtop platforms have evolved since the previous study1.
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    Evolution of Codon Usage In The Smallest Photosynthetic Eukaryotes And Their Giant Viruses (2013)
    OXFORD UNIV PRESS
    In:  EPIC3Genome Biology and Evolution, OXFORD UNIV PRESS, 5(5), pp. 848-859, ISSN: 1759-6653
    Details
    Publication Date: 2019-07-16
    Description: Prasinoviruses are among the largest viruses (〉200 kbp) and encode several hundreds of protein coding genes, including most genes of the DNA replication machinery and several genes involved in transcription and translation, as well as tRNAs. They can infect and lyse small eukaryotic planktonic marine green algae, thereby affecting global algal population dynamics. Here we investigate the causes of codon usage bias in one prasinovirus, OtV5, and its host Ostreococcus tauri, during a viral infection using microarray expression data. We show that (i) codon usage bias in the host and in the viral genes increases with expression levels and (ii) optimal codons use those tRNAs encoded by the most abundant host tRNA genes, supporting the notion of translational optimization by natural selection. We find evidence that viral tRNA genes complement the host tRNA pool for those viral amino acids whose host tRNAs are in short supply. We further discuss the coevolution of Codon usage bias in hosts and prasinoviruses by comparing optimal codons in 3 evolutionary Diverged host--‐virus specific pairs whose complete genome sequences are known.
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    Arctic spring awakening – a pan-Arctic view on processes controlling bottom ice algae blooms (2013)
    In:  EPIC3Arctic Frontiers Conference, Tromsø, Norwaz, 2013-01
    Details
    Publication Date: 2019-07-17
    Description: Extreme seasonal changes in light conditions are among the key characteristics of high Arctic ecosystems with far-reaching implications for their potential to generate biomass via photosynthetic primary production. As a result, Arctic ecosystems are usually characterized by a very short productive period during spring/summer that provides the entire annual biomass production available for higher trophic levels. Of particular ecological importance is the bottom ice algae bloom, which provides a pulse of primary production when no other significant food source exists in the marine ecosystem. Solar angle, sea ice cover and snow thickness are the main factors that determine timing and progression of the bottom ice algae bloom, while nutrient availability often affects the peak magnitude (and nutritional quality) of algal blooms. In this work, we summarize a pan-Arctic dataset of bottom ice algae biomass time series to describe latitudinal gradients in bloom development and the processes that control these gradients. We conclude with a discussion of potential implications for ecosystem structure and trophic fate of the produced biomass. The ongoing changes due to climate warming lead to alterations of environmental conditions, and their consequences for Arctic productivity are still heavily debated. By comparing pan-Arctic data on the seasonal development of vernal bloom processes and different bloom scenarios, we try to identify the most important factors determining the phenology of bottom ice algae during this important transitional phase in the Arctic.
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    Cenozoic boron isotope variations in benthic foraminifers (2013)
    In:  EPIC3Geology, 41(5), pp. 591-594, ISSN: 0091-7613
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    Publication Date: 2019-07-17
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    Phylogeny and morphology of a Chattonella (Raphidophyceae) species from the Mediterranean Sea: what is C. subsalsa? (2013)
    TAYLOR & FRANCIS LTD
    In:  EPIC3European Journal of Phycology, TAYLOR & FRANCIS LTD, 48(1), pp. 79-92, ISSN: 0967-0262
    Details
    Publication Date: 2019-07-16
    Description: We analysed the molecular and morphological features of strains of Chattonella subsalsa isolated from the western Adriatic coast (Mediterranean Sea), with the aim of confirming their classification and elucidating their phylogenetic positions within the Raphidophyceae. We sequenced parts of the ribosomal operon, including the small subunit (SSU), the internal transcribed spacer region (ITS) and the large subunit (LSU) of the rDNA. Additionally, we analysed sequences of the chloroplast-encoded subunit psaA of Photosystem I (PSI) and rbcL, encoding the large subunit of the Rubisco gene. For three phylogenetic markers (LSU, ITS, rbcL), the sequences of the strains from the Adriatic Sea were identical and for two markers (SSU, psaA) only minor differences occurred. All strains were sister to, but well separated from, sequences from isolates in culture collections and from GenBank, thus far classified as belonging to C. subsalsa. Light and electron microscopy provided evidence for morphological differences between a strain of C. subsalsa (CCMP217) from the Gulf of Mexico and the isolates from the Adriatic Sea. Differences concerned the shape and arrangement of chloroplasts and the presence of mucocysts and other surface microstructures, which were only observed in isolates from the Adriatic Sea. This is the first evidence for two different taxa classified as C. subsalsa, which are clearly separated on the basis of several genetic markers and also show morphological differences. As compared with strains assigned to C. subsalsa from the NCMA (formerly CCMP) culture collection, the Adriatic strains more closely match the original species description. This would imply that strain CCMP217 and other genetically similar strains should be described under a new species name. Nevertheless, given the high morphological plasticity of Chattonella species, the definition of the true C. subsalsa must be decided based on detailed morphological and molecular analysis of more strains from other geographical areas.
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    Data files: Phenotypic evolution in a venerid bivalve species lineage from the late Middle Miocene Central Paratethys Sea: a multi-approach morphometric analysis (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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    Dendrogram of Cluster-analysis of overall comparison (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Arctic permafrost coasts in a changing climate (2013)
    In:  EPIC3Deutsche Bundesstiftung Umwelt: Abschlussveranstaltung des DBU-Promotionsstipendienprogramms - Absolventen des Jahrgangs 2012, Osnabrück, Germany, 2013-04-19-2013-04-20
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Distribution and abundance of Antarctic krill (Euphausia superba) along the Antarctic Peninsula (2013)
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, ISSN: 09670637
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    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
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    Sampling marine sediment (2013)
    In:  EPIC3PAGES News, 21(1), pp. 8-9
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Dating and synchronizing paleoclimate records over the last interglacial (2013)
    In:  EPIC3PAGES News, 21(1), pp. 26-27
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Reconstruction of past sea ice extent (2013)
    In:  EPIC3PAGES news, 21(1), pp. 30-31
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    1st Sea Ice Proxy (SIP) Working Group workshop, Montreal, Canada 7-9 March 2012 (2013)
    In:  EPIC3PAGES news, 21(1), pp. 43-43
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    Publication Date: 2019-07-17
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    Coral reef degradation and metabolic performance of the scleractinian coral Porites lutea under anthropogenic impact along the NE coast of Hainan Island, South China Sea (2013)
    In:  EPIC3Continental Shelf Research, 57, pp. 123-131, ISSN: 02784343
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    Publication Date: 2019-07-17
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    Documentation of datasets of the JGOFS Australia Project (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
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    Permafrost warming and surface energy balance processes at two contrasting sites: Samoylov, Lena Delta (Siberia), Bayelva (Spitsbergen) (2013)
    In:  EPIC3CryoFIM Back work shop Svalbard, Longyearbyen, Svalbard, 2013-04-15-2013-04-19
    Details
    Publication Date: 2019-07-16
    Description: Predicting the vulnerability of permafrost carbon (C) to climate change requires simulation of the permafrost’s annual dynamics coupled with the C cycle, as well as the soil water status which determines aerobic or anaerobic decomposition of organic matter. Quantitative long-term water and energy balance studies are particularly scarce circumpolar and almost absent from Siberia, but are of great importance for the validation of climate and permafrost surface schemes within climate models. Furthermore, due to the complex nature and non linearity of processes, quantitative predictions vary largely. Within the research group SPARC (Sensitivity of the permafrost system’s water and energy balance under changing climate: A multiscale perspective) the carbon, water, and heat flux cycles in the complex Arctic landscapes at scales that range from metres to kilometres are investigated. Two field sites, located in the continuous permafrost environment are studied in detail since 1998: Bayelva (close to Ny-Alesund, Spitsbergen) and Samoylov (Lena Delta, Siberia). We combine field measurements of permafrost processes, pools, and fluxes, with remote sensing data and numerical climate models at local and regional scales. A quantitative process understanding is developed by identifying key processes of the seasonal and annual energy, water and carbon balance and the factors that affect these processes. This includes: representation of sub-grid cell variability in the landcover (especially with regard to water bodies), the quantification of the annual surface energy balance, the importance of snow cover formation and ablation for the permafrost thermal regime and the relationships between thermal and hydrologic processes and carbon cycle. The data collection as well as process understanding is also used within the large collaborative EU 7th framework project PAGE21 (Changing Permafrost in the Arctic and its Global Effects in the 21st Century (PAGE21). This project aims to understand and quantify the vulnerability of permafrost environments to a changing global climate, and to investigate the feedback mechanisms associated with increasing greenhouse gas emissions from permafrost zones.
    Repository Name: EPIC Alfred Wegener Institut
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    Biological production in the Bellingshausen Sea from oxygen-to-argon ratios and oxygen triple isotopes (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Biogeosciences, COPERNICUS GESELLSCHAFT MBH, 10, pp. 2273-2291, ISSN: 1726-4170
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Controls of Caribbean surface hydrology during the mid- to late Holocene: insights from monthly resolved coral records (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Climate of the Past, COPERNICUS GESELLSCHAFT MBH, 9, pp. 841-858, ISSN: 1814-9324
    Details
    Publication Date: 2019-07-17
    Description: Several proxy-based and modeling studies have investigated long-term changes in Caribbean climate during the Holocene, however, very little is known on its variability on short timescales. Here we reconstruct seasonality and interannual to multidecadal variability of sea surface hydrology of the southern Caribbean Sea by applying paired coral Sr/Ca and δ18O measurements on fossil annually banded Diploria strigosa corals from Bonaire. This allows for better understanding of seasonal to multidecadal variability of the Caribbean hydrological cycle during the mid- to late Holocene. The monthly resolved coral Δδ18O records are used as a proxy for the oxygen isotopic composition of seawater (δ18Osw) of the southern Caribbean Sea. Consistent with modern day conditions, annual δ18Osw cycles reconstructed from three modern corals reveal that freshwater budget at the study site is influenced by both net precipitation and advection of tropical freshwater brought by wind-driven surface currents. In contrast, the annual δ18Osw cycle reconstructed from a mid-Holocene coral indicates a sharp peak towards more negative values in summer, suggesting intense summer precipitation at 6 ka BP (before present). In line with this, our model simulations indicate that increased seasonality of the hydrological cycle at 6 ka BP results from enhanced precipitation in summertime. On interannual to multidecadal timescales, the systematic positive correlation observed between reconstructed sea surface temperature and salinity suggests that freshwater discharged from the Orinoco and Amazon rivers and transported into the Caribbean by wind-driven surface currents is a critical component influencing sea surface hydrology on these timescales.
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    Strukturentwurf einer Regattayacht mit Hilfe eines Topologieoptimierungsverfahrens nach der SIMP – Methode (2013)
    In:  EPIC3
    Details
    Publication Date: 2016-08-22
    Description: Within the framework of the YEAH-Project „Yacht Engineering based on the ELiSE method for the application in the high-end regatta environment“ new ways for the design of radically improved light weight structures are found by using a new bionic lightweight construction and optimization method. Mass and maximum deformation of the entire system are key values for evaluating the grade of the structural design of a regatta yacht. The target is to minimize the weight of the structural elements, such that unbound mass can be positioned within the ship for the benefit of stability. Meanwhile minimizing the structural weight should not lead to a decrease of stiffness of the entire system followed by an increase of global deformation. An earlier conducted design study shows, that the idea of meeting both above mentioned demands while using a traditional structural design is not very promising such that the need for a new approach in structural design became obvious. Within this thesis and as an major element of the YEAH-Project, an innovative Space-Frame- Concept is introduced by using topology optimization as a design tool, based on an already existing sailing yacht design. It is shown, that the new concept outreaches initial expectations and leads to a remarkable decrease of mass and deformation. The topology optimization is conducted in two steps using load case information from the reference yacht. In the first phase, general information about the position of structural members in space is generated and planes for structural elements are derived. In a second step the best topology within those predefined planes is found and the Space-Frame-Concept is introduced. A structural analysis is used for dimensioning the structural elements, followed by comparing the grade of the new concept with the traditional frame system. For conclusion the applied method is discussed critically and recommendations for future work packages are given, focusing on the practical application of the innovative and promising Space- Frame-Concept.
    Repository Name: EPIC Alfred Wegener Institut
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    Internal structure of the ice sheet between Kohnen station and Dome Fuji, Antarctica, revealed by airborne radio-echo sounding (2013)
    INT GLACIOL SOC
    In:  EPIC3Annals of Glaciology, INT GLACIOL SOC, 54(64), pp. 163-167, ISSN: 0260-3055
    Details
    Publication Date: 2017-10-17
    Description: This study aims to demonstrate that deep ice cores can be synchronized using internal horizons in the ice between the drill sites revealed by airborne radio-echo sounding (RES) over a distance of 〉1000 km, despite significant variations in glaciological parameters, such as accumulation rate between the sites. In 2002/03 a profile between the Kohnen station and Dome Fuji deep ice-core drill sites, Antarctica, was completed using airborne RES. The survey reveals several continuous internal horizons in the RES section over a length of 1217 km. The layers allow direct comparison of the deep ice cores drilled at the two stations. In particular, the counterpart of a visible layer observed in the Kohnen station (EDML) ice core at 1054 m depth has been identified in the Dome Fuji ice core at 575 m depth using internal RES horizons. Thus the two ice cores can be synchronized, i.e. the ice at 1560 m depth (at the bottom of the 2003 EDML drilling) is $49 ka old according to the Dome Fuji age/depth scale, using the traced internal layers presented in this study.
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    Erratum to ‘Control of sulphate and methane distributions in marine sediments by organic matter reactivity’ [Geochimica et Cosmochimica 104 (2013) 183–193] (2013)
    In:  EPIC3Geochimica et Cosmochimica Acta, 113, pp. 225-226, ISSN: 00167037
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    Publication Date: 2018-02-12
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    Bio-Mooring Arrays and Long-Term Sediment Traps: Key Tools to Detect Change in the Biogeochemical and Ecological Functioning of Arctic Marine Ecosystems (2013)
    In:  EPIC3Arctic Observing Summit 2013, Vancouver, Canada, 2013-04-30-2013-05-02
    Details
    Publication Date: 2019-08-02
    Description: Through the transfer of carbon from the surface to the deep ocean via the passive sinking and active transport of organic material, the biological pump is a key global process for the regulation of atmospheric CO2. Over the last decades, studies relying on sediment traps and other bio-devices moored over an annual cycle in the Arctic Ocean helped to resolve how the Arctic biological pump is operating and how it is responding to global change. Here, we provide a short review of the pioneer work done in the 1980-90’s and we present key knowledge gained on Arctic ecosystem functioning with a series of case-studies conducted in the 2000’s on the basis of bio-moorings: (1) carbon export in response to warm anomalies in the main Arctic gateway, the Fram Strait; (2) ecosystem-level analyses in Beaufort Sea from a vertical flux perspective; (3) the importance of lateral processes for sinking flux events in the Central Basin; and (4) the impact of zooplankton life-cycle strategies on the biological pump in fjord-like systems. We also identify regional challenges and potential future research avenues in terms of new sampling tools and coordination for the development of an Arctic biogeochemical observatory network aligned with global initiatives. As such, this paper represents a call to sustain and further develop observing activities that rely on bio-mooring arrays in the Arctic Ocean over the next decade. By capturing the full seasonality of ice-covered environments, we argue that bio-moorings are one of the most powerful approaches to distinguish natural variability from actual shifts that might affect the structure and function of Arctic marine ecosystems in response to human-induced changes.
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    SO225 ParaSound journal (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2020-06-12
    Repository Name: EPIC Alfred Wegener Institut
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    Ecogenomic perspectives on domains of unknown function: correlation-based exploration of marine metagenomes (2013)
    Public Library of Science
    In:  EPIC3PLoS One, Public Library of Science, 8(3)
    Details
    Publication Date: 2020-02-12
    Description: Background The proportion of conserved DNA sequences with no clear function is steadily growing in bioinformatics databases. Studies of sequence and structural homology have indicated that many uncharacterized protein domain sequences are variants of functionally described domains. If these variants promote an organism's ecological fitness, they are likely to be conserved in the genome of its progeny and the population at large. The genetic composition of microbial communities in their native ecosystems is accessible through metagenomics. We hypothesize the co-variation of protein domain sequences across metagenomes from similar ecosystems will provide insights into their potential roles and aid further investigation. Methodology/Principal findings We calculated the correlation of Pfam protein domain sequences across the Global Ocean Sampling metagenome collection, employing conservative detection and correlation thresholds to limit results to well-supported hits and associations. We then examined intercorrelations between domains of unknown function (DUFs) and domains involved in known metabolic pathways using network visualization and cluster-detection tools. We used a cautious “guilty-by-association” approach, referencing knowledge-level resources to identify and discuss associations that offer insight into DUF function. We observed numerous DUFs associated to photobiologically active domains and prevalent in the Cyanobacteria. Other clusters included DUFs associated with DNA maintenance and repair, inorganic nutrient metabolism, and sodium-translocating transport domains. We also observed a number of clusters reflecting known metabolic associations and cases that predicted functional reclassification of DUFs. Conclusion/Significance Critically examining domain covariation across metagenomic datasets can grant new perspectives on the roles and associations of DUFs in an ecological setting. Targeted attempts at DUF characterization in the laboratory or in silico may draw from these insights and opportunities to discover new associations and corroborate existing ones will arise as more large-scale metagenomic datasets emerge.
    Repository Name: EPIC Alfred Wegener Institut
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    Comparison of Eemian and Holocene sea surface temperatures in the Bering Sea including terminations II and I (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2020-11-27
    Repository Name: EPIC Alfred Wegener Institut
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    Subglacial roughness of the former Barents Sea ice sheet (2013)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Earth Surface, Wiley, 118(4), pp. 2546-2556, ISSN: 0148-0227
    Details
    Publication Date: 2016-11-15
    Description: The roughness of a glacier bed has high importance for the estimation of the sliding velocity and can also provide valuable insights into the dynamics and history of ice sheets, depending on scale. Measurement of basal properties in present-day ice sheets is restricted to ground-penetrating radar and seismics, with surveys retrieving relatively coarse data sets. Deglaciated areas, like the Barents Sea, can be surveyed by shipborne 2-D and 3-D seismics and multibeam sonar and provide the possibility of studying the basal roughness of former ice sheets and ice streams with high resolution. Here, for the first time, we quantify the subglacial roughness of the former Barents Sea ice sheet by estimating the spectral roughness of the basal topography. We also make deductions about the past flow directions by investigating how the roughness varies along a 2-D line as the orientation of the line changes. Lastly, we investigate how the estimated basal roughness is affected by the resolution of the basal topography data set by comparing the spectral roughness along a cross section using various sampling intervals. We find that the roughness typically varies on a similar scale as for other previously marine-inundated areas in West Antarctica, with subglacial troughs having very low roughness, consistent with fast ice flow and high rates of basal erosion. The resolution of the data set seems to be of minor importance when comparing roughness indices calculated with a fixed profile length. A strong dependence on track orientation is shown for all wavelengths, with profiles having higher roughness across former flow directions than along them.
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    Integrated benthic exchange dynamics and biogeochemical processes under varying environmental conditions (2013)
    In:  EPIC3
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    Publication Date: 2016-12-05
    Repository Name: EPIC Alfred Wegener Institut
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    Cold-water coral carbonate mounds as unique palaeo-archives: The Plio-Pleistocene Challenger Mound record (NE Atlantic) (2013)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Quaternary Science Reviews, PERGAMON-ELSEVIER SCIENCE LTD, 73, pp. 14-30, ISSN: 0277-3791
    Details
    Publication Date: 2017-01-13
    Description: Through the interplay of a stabilising cold-water coral framework and a dynamic sedimentary environment, cold-water coral carbonate mounds create distinctive centres of bio-geological accumulation in often complex (continental margin) settings. The IODP Expedition 307 drilling of the Challenger Mound (eastern Porcupine Seabight; NE Atlantic) not only retrieved the first complete developmental history of a coral carbonate mound, it also exposed a unique, Early-Pleistocene sedimentary sequence of exceptional resolution along the mid-latitudinal NE Atlantic margin. In this study, a comprehensive assessment of the Challenger Mound as an archive of Quaternary palaeo-environmental change and long-term coral carbonate mound development is presented. New and existing environmental proxy records, including clay mineralogy, planktonic foraminifer and calcareous nannofossil biostratigraphy and assemblage counts, planktonic foraminifer oxygen isotopes and siliciclastic particle-size, are thereby discussed within a refined chronostratigraphic and climatic context. Overall, the development of the ChallengerMound shows a strong affinity to the Plio-Pleistocene evolution of the Northern Hemisphere climate system, albeit not being completely in phase with it. The two major oceanographic and climatic transitions of the Plio-Pleistocene e the Late Pliocene/Early Pleistocene intensification of continental ice-sheet development and the mid-Pleistocene transition to the more extremely variable and more extensively glaciated late Quaternary e mark twomajor thresholds in Challenger Mound development: its Late Pliocene (〉2.74 Ma) origin and itsMiddleeLate Pleistocene to recent decline. Distinct surface-water perturbations (i.e. water-mass/polar front migrations, productivity changes, melt-water pulses) are identified throughout the sequence, which can be linked to the intensity and extent of ice development on the nearby BritisheIrish Isles since the earliest Pleistocene. Glaciation-induced shifts in surfacewater primary productivity are thereby proposed to fundamentally control cold-water coral growth, which in turn influences on-mound sediment accumulation and, hence, coral carbonate mound development throughout the Pleistocene. As local factors, such as proximal ice-sheet dynamics and on-mound changes in cold-water coral density, significantly affected the development of the Challenger Mound, they can potentially explain the nature of its palaeo-record and its offsets with the periodicities of global climate variability. On the other hand, owing to this unique setting, a regionally exceptional, high-resolution palaeo-record of Early Pleistocene (ca 2.6 to 2.1 Ma) environmental change (including early BritisheIrish ice-sheet development), broadly in phase with the 41 ka-paced global climate system, is preserved in the lower Challenger Mound. All in all, the Challenger Mound record highlights the wider relevance of coral carbonate mound archives and their potential to capture unique records from dynamic (continental margin) environments.
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    Die Suche nach Fingerabdrücken im Meer (2013)
    In:  EPIC3Open Ship Maria S. Merian, Bremen, 2013-09-21-2013-09-22Open Ship Maria S. Merian
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    Publication Date: 2017-01-09
    Repository Name: EPIC Alfred Wegener Institut
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    A role for haemolymph oxygen capacity in heat tolerance of eurythermal crabs (2013)
    In:  EPIC3Frontiers in Physiology, 4, ISSN: 1664-042X
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    Publication Date: 2017-01-17
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    Growth production of two notothenioid fish species from different geographical regions of the Antarctica (2013)
    In:  EPIC3
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    Publication Date: 2017-01-10
    Description: To date, the ecology and in particular mechanisms influencing the growth and the distribution of Antarctic fish are still poorly understood. This study provides data about the age and growth of two dominant notothenioid fish species: the pelagic keystone species Pleuragramma antarcticum and the benthopelagic species Trematomus eulepidotus. Fish were sampled from different geographical regions of the Antarctic waters during expeditions with the research vessel POLARSTERN in 2003/2004, 2011, and 2012. Age was determined by sagittal otolith increment analysis. By applying the von Bertalanffy growth formula, growth curves for both species from the different study sites of the Antarctica were generated in order to assess their growth performance. Analysis revealed a maximum age of 13 years for P. antarcticum and 19 years for T. eulepidotous. Both species had relatively slow growth with growth coefficients (k) of 0.16 – 0.25 for P. antarcticum and 0.11 – 0.23 for T. eulepidotus and neither grew especially large. Nevertheless, T. eulepidotus achieved larger maximum lengths than P. antarcticum overall. Both species had significantly higher growth rates and a better nutritional condition at lower latitudes of the South Shetland Islands compared to the more southern areas of the eastern Weddell Sea. In this study, growth performances of the two species from different geographical areas are presented and compared both intra- and interspecifically. After Ccomparing these data, it is evident that both species grow faster at higher annual mean temperatures. Furthermore, fast growth coefficients were associated with lower maximum ages and therefore, seem to reduce the longevity of fish.
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    Antarctic benthic communities under the influence of different ice regimes (2013)
    In:  EPIC354 p.
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    Publication Date: 2017-01-26
    Description: Ice in its different forms affects benthic communities in polar regions directly and indirectly. In order to recognize effects of ice on benthic communities this thesis analyses benthos on the high Antarctic shelf of the southeastern Weddell Sea, a typical high Antarctic habitat, influenced by seasonal sea ice coverage, benthic communities in the Larsen A/B embayments, being covered for hundreds of years by thick ice shelves, which in 1995 and 2002 disintegrated, thus providing large areas to be colonized newly by benthos, and benthos communities form the shelf at the tip of the Antarctic Peninsula, an habitat that can be considered as being unaffected by ice. The benthos in these three subregions revealed distinct differences in densities, biomasses, production, with lowest values in Larsen (680 Ind m-2,78 g wet weight m-2, and 1.7 g C m-2y-1, respectively).Organism densities at the tip of the Peninsula were slightly higher as compared to the southeastern Weddell Sea Shelf (2767 Ind m-2 vs. 2534 Ind m-2), whereas biomass and production were higher on the southeastern Weddell Sea Shelf than at the tip of the Peninsula due to the dominance of large growing suspension feeders. The normalized biomass size spectra (NBSS) of the benthic communities in the three subregions thus exhibited significant differences in their size structure which could be associated with the different ice regimes and input of organic carbon. The slopes of the NBSS ranged from -0.22 on the southeastern Weddell Sea Shelf to -0.34 in Larsen and -0.50 at the tip of the Peninsula, indicating that macrobenthic communities in the SEWSS are dominated by large-bodied organisms such as suspension feeders (i.e. sponges, tunicates and bryozoans). Contrasting the benthic communities in Larsen and the tip of the Peninsula were dominated by small-bodied organisms such deposit feeders. This study clearly shows pronounced differences in structures, composition and densities/biomasses in the benthic communities in the three subregions which can be associated directly or indirectly to the prevailing different ice regimes in the three regions.
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    Environmental change and the physiological performance of crabs (2013)
    In:  EPIC3Bodega Marine Laboratory Research Seminar, Bodega Bay, CA, USA
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    Publication Date: 2017-01-26
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    Predicting the Response of Molluscs to the Impact of Ocean Acidification (2013)
    In:  EPIC3Biology, 2(2), pp. 651-692, ISSN: 2079-7737
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    Publication Date: 2017-01-26
    Description: Elevations in atmospheric carbon dioxide (CO2) are anticipated to acidify oceans because of fundamental changes in ocean chemistry created by CO2 absorption from the atmosphere. Over the next century, these elevated concentrations of atmospheric CO2 are expected to result in a reduction of the surface ocean waters from 8.1 to 7.7 units as well as a reduction in carbonate ion (CO32−) concentration. The potential impact that this change in ocean chemistry will have on marine and estuarine organisms and ecosystems is a growing concern for scientists worldwide. While species-specific responses to ocean acidification are widespread across a number of marine taxa, molluscs are one animal phylum with many species which are particularly vulnerable across a number of life-history stages. Molluscs make up the second largest animal phylum on earth with 30,000 species and are a major producer of CaCO3. Molluscs also provide essential ecosystem services including habitat structure and food for benthic organisms (i.e., mussel and oyster beds), purification of water through filtration and are economically valuable. Even sub lethal impacts on molluscs due to climate changed oceans will have serious consequences for global protein sources and marine ecosystems.
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    New cystochromanes and oxidized meroditerpenes from the brown alga Cystoseira baccata – Indication for a general revision of the bicyclo[4.3.0]nonane system? (2013)
    In:  EPIC314th International Symposium on Marine Natural Products/8th European Conference on Marine Natural Products, La Toja Island, Spain, 2013-09-15-2013-09-20
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    Publication Date: 2017-02-01
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    Systematic Investigation on the MS-Fragmentation of the Marine Alkaloids Haliclamines: Synthesis of an Intermediate in the Fragmentation Pathway (2013)
    In:  EPIC3GDCh-Wissenschaftsforum Chemie 2013, Darmstadt, 2013-09-01-2013-09-04
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    Publication Date: 2017-02-01
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    Isolation and characterization of novel natural products from marine organisms: examples from three sponges, an alga, and a scleractinian coral (2013)
    In:  EPIC3
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    Publication Date: 2017-02-01
    Repository Name: EPIC Alfred Wegener Institut
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    Vertical distribution of methane oxidation and methanotrophic response to elevated methane concentrations in startified waters of the Arctic fjord storfjorden (Svalbard, Norway) (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Biogeosciences, COPERNICUS GESELLSCHAFT MBH, pp. 6267-6278, ISSN: 1726-4170
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    Publication Date: 2017-01-31
    Description: Abstract. The bacterially mediated aerobic methane oxidation (MOx) is a key mechanism in controlling methane (CH4) emissions from the world’s oceans to the atmosphere. In this study, we investigated MOx in the Arctic fjord Storfjorden (Svalbard) by applying a combination of radio-tracerbased incubation assays (3H-CH4 and 14C-CH4), stable CCH4 isotope measurements, and molecular tools (16S rRNA gene Denaturing Gradient Gel Electrophoresis (DGGE) fingerprinting, pmoA- and mxaF gene analyses). Storfjorden is stratified in the summertime with melt water (MW) in the upper 60m of the water column, Arctic water (ArW) between 60 and 100 m, and brine-enriched shelf water (BSW) down to 140 m. CH4 concentrations were supersaturated with respect to the atmospheric equilibrium (about 3–4 nM) throughout the water column, increasing from �20nM at the surface to a maximum of 72nM at 60m and decreasing below. MOx rate measurements at near in situ CH4 concentrations (here measured with 3H-CH4 raising the ambient CH4 pool by 〈2 nM) showed a similar trend: low rates at the sea surface, increasing to a maximum of �2.3nMday−1 at 60 m, followed by a decrease in the deeper ArW/BSW. In contrast, rate measurements with 14C-CH4 (incubations were spiked with �450nM of 14C-CH4, providing an estimate of the CH4 oxidation at elevated concentration) showed comparably low turnover rates (〈1nMday−1) at 60 m, and peak rates were found in ArW/BSW at �100m water depth, concomitant with increasing 13C values in the residual CH4 pool. Our results indicate that the MOx community in the surface MW is adapted to relatively low CH4 concentrations. In contrast, the activity of the deep-water MOx community is relatively low at the ambient, summertime CH4 concentrations but has the potential to increase rapidly in response to CH4 availability. A similar distinction between surface and deepwater MOx is also suggested by our molecular analyses. The DGGE banding patterns of 16S rRNA gene fragments of the surface MW and deep water were clearly different. A DGGE band related to the known type I MOx bacterium Methylosphaera was observed in deep BWS, but absent in surface MW. Furthermore, the Polymerase Chain Reaction (PCR) amplicons of the deep water with the two functional primers sets pmoA and mxaF showed, in contrast to those of the surface MW, additional products besides the expected one of 530 base pairs (bp). Apparently, different MOx communities have developed in the stratified water masses in Storfjorden, which is possibly related to the spatiotemporal variability in CH4 supply to the distinct water masses.
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    DIELECTRIC PROFILING OF ALPINE ICE CORES AS ASSISTANCE FOR GROUND PENETRATING RADAR (2013)
    In:  EPIC3
    Details
    Publication Date: 2017-01-25
    Description: The present thesis aimed to, for the first, deploy dielectric profiling (DEP) to an entire Alpine ice core drilled to bedrock. DEP allows for a non-destructive measurement of an ice core’s complex relative dielectric permittivity at kHz frequencies. Based on the thus obtained dielectric profile of the core, it was the task to derive a synthetic radargramm by forward modelling and to compare the later with radar traces from ground penetrating radar (GPR). Forward modelling by convolution of the reflectance profile, derived from DEP data, with a synthetic radar wavelet in the time domain yields a synthetic radargramm, which in principle should reproduce the coherent features of a GPR trace recorded adjacent to the borehole. Thereby a physical connection between ice core properties and radar reflectors is established. The method was applied in full extent to the CDM core from Col du Dôme (CDD), Mont Blanc, and partially to the KCC core from Colle Gnifetti (CG), Monte Rosa, which supplemented the thesis in it’s final stage. The DEP data of the CDM core was afflicted with a comparatively large amount of defects and with artefacts due to a dysfunction of the DEP setup. An adequate approach of data treatment was rigorously developed and applied. The corrections could be assessed with the complementary data of the KCC core. Analysis of the DEP profiles e.g probably allowed the identification of a known regime change in Alpine snow chemistry in the 1950s. Forward modelling reproduced in the firn part several reflectors from GPR traces adjacent to the borehole predominately caused by permittivity changes. As by product the analysis of radargramms from CDD revealed below the firn-ice transition a reflector-free zone (RFZ), as it is known from CG, and offered some indications regarding its origin.
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    Benthosuntersuchungen im Rahmen des Beweissicherungsverfahrens für den Ausbau des Hafenbecken IV in Büsum (2013)
    In:  EPIC3Erster Zwischenbericht im Auftrag des Landesbetriebs für Küstenschutz, Nationalpark und Meeresschutz Schleswig-Holstein, Husum. 33 pp.
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    Publication Date: 2017-03-06
    Repository Name: EPIC Alfred Wegener Institut
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    Benthouseuntersuchungen im Rahmen des Beweisverfahrens für den Ausbau des Hafenbecken IV Büsum (2013)
    In:  EPIC3Zweiter Zwischenbericht im Auftrag des Landesbetrieb für Küstenschutz, Nationalpark und Meeresschutz Schleswig-Holstein, Husum. 37 pp.
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    Publication Date: 2017-03-06
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    Monitoring und Bewertung des Benthos, der Lebensraumtypen/Biotope und der Gebietsfremden Arten, 3. Synthetischer Jahresbericht, BfN, 66 pp (2013)
    In:  EPIC3Monitoring und Bewertung des Benthos, der Lebensraumtypen/Biotope und der Gebietsfremden Arten, 3. Synthetischer Jahresbericht, BfN, 66 pp
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    Publication Date: 2017-03-06
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    Cruise Report RV Heincke HE408 (2013)
    In:  EPIC3
    Details
    Publication Date: 2016-09-20
    Description: This cruise was a part of the “Verbundprojekt BIOACID” (Biological Impacts of Ocean ACIDification) Phase II (consortium 4 of 5), funded by the German Ministry for Education and Research (BMBF). It was also connected to the Norwegian programme on ecophysiology and ecotoxicology of Polar cod (Boreogadus saida) under global change, “POLARISATION”. Together, the team investigates how the combined effects of ocean acidification and warming (OAW) affect different life stages of the interacting fish species Atlantic cod (G. morhua) and Polar cod (B. saida) and their prey. The main objectives of this cruise were to elucidate whether OAW affects interacting species differently due to divergent physiological optima and ranges, expressed in thermal tolerance windows and associated performance capacities and phenologies of specific life stages. Further, we intended to obtain specimens of both Polar cod (B. saida) and Atlantic cod (G. morhua) as well as planktonic organisms in the Atlantic and polar waters around Svalbard, which were used in experiments on board and back at the Alfred Wegener Institute and the University of Tromsø/Havbruksstasjonen i Tromsø. We left Bremerhaven on the morning of August 16th, and arrived in Tromsø on Aug 21st, where we met with our Norwegian colleagues and took some samples and the fish-lift (Holst&McDonald, 2000) on board. We left for Northern Svalbard the same afternoon and sampled the Northern range of sites before calling at Ny-Ålesund on August 30th, where samples and material from the 2013 summer campaign was taken on board. On August 31st, we called at Longyearbyen to exchange personnel and leave the fish-lift for our Norwegian colleagues. Over the next four days, we sampled the southern stations before leaving Svalbard for the last sampling site at Bear Island on Sept 4th. After this last sampling site, we left for Tromsø where we unloaded samples and live fish (B. saida) for the Havbruksstasjon in Kårvik on September 7th and 9th. In the late morning hours of Sept 9th, we left Tromsø towards Bremerhaven.
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    Millennial-scale ice rafting events and Hudson Strait Heinrich(-like) Events during the late Pliocene and Pleistocene: a review (2013)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 80, pp. 1-28, ISSN: 02773791
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    Publication Date: 2016-11-06
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    Zooplankton-phytoplankton interactions in a changing world: combining long-term series with experimental research (2013)
    In:  EPIC3Colloq., Umeå University, Sweden, 2013
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    Publication Date: 2016-12-02
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  • 373
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    Microbial community ecology of marine methane seeps (2013)
    In:  EPIC3
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    Publication Date: 2016-12-05
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  • 374
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    Meridional overturning circulation observations in the North Atlantic Ocean (2013)
    In:  EPIC3Bull. Amer. Meteor. Soc., 95(7), pp. 67-69
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    Publication Date: 2016-12-08
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  • 375
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    Simulating feedback cycles induced by basal water in western Dronning Maud Land, Antarctica (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2013-12-09-2013-12-13
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    Publication Date: 2016-12-13
    Description: The occurrence of liquid water at the base of an ice sheet is believed to be a crucial component in its dynamic evolution. If temperatures at the base locally reach the pressure melting point, basal melt water lubricates the base and thus supports basal sliding. Faster basal sliding in turn reduces internal deformation and thus the internal heat production due to strain heating. If this loss of strain heating is not counterbalanced by frictional heat due to sliding or the advection of warm ice, the base of the ice will freeze to the bedrock again. Thus the presence of liquid water can lead to a cooling and a subsequent stagnation of fast ice flow, posing a negative feedback cycle. In addition, strain heating within a temperate ice layer generates a liquid water fraction in the ice, leading to a softer material and enhanced deformation. If the horizontal or vertical advection of cold ice to the base is weak, this will lead to a positive feedback. These feedback cycles are studied along numerical simulations of the present day ice flow in the area of the western Dronning Maud Land, Antarctica, including the adjacent Brunt and Riiser- Larsen ice shelves. To investigate the influence of basal water on basal sliding and ice rheology we use the three-dimensional thermo-coupled full-Stokes model TIM-FD3 on a 2.5 km horizontal grid. We use the enthalpy gradient method to compute the thermal evolution, including the microscopic water content, in temperate ice areas. Three different flux routing algorithms for the subglacial melt water and a modified Weertman-type sliding relation are implemented in the model to account for higher sliding velocities under wet basal conditions. We present our analysis of the involved feedback mechanisms between sliding, ice deformation, temperature and rheology, which are related to the occurrence of basal water.
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    The effect of sedimentation in a subglacial lake on the dynamics of an artificial ice stream (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2013-12-09-2013-12-13
    Details
    Publication Date: 2016-12-13
    Description: As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocity and a subsequent lowering of the ice surface in the vicinity of the upstream lake edge. Conversely, at the downstream end of the lake a small hump is observed as the ice velocity decreases near the point of contact with land. There are two contributions arising from the ice/lake interaction: (1) changes in the thermal regime that propagate downwards with the advection of ice and (2) the increase in flow speeds caused by basal sliding over the lake surface. Sediment transport from upstream areas into subglacial lakes changes their size, thus reducing the area of the ice/lake interface. Here, we aim to study the effect that this reduction in size has on the flow dynamics and the surface elevation of an artificial ice stream and the temporal evolution of this effect. To this end, we use a full-Stokes, polythermal ice flow model, implemented into the commercial finite element software COMSOL Multiphysics. An enthalpy gradient method is used in order to account for the evolution of temperature and water content within the ice. This conceptual model uses prescribed boundary velocity and temperature profiles and a Weertman-type sliding law with a fixed parameter combination. In order to separate the effect of the slow thermal contribution from the fast mechanical one, we will present sensitivity tests that additionally involve a thermally-constant flow.
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  • 377
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    Pine Island Glacier - local flow mechanisms and basal sliding (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2013-12-09-2013-12-13
    Details
    Publication Date: 2016-12-13
    Description: Pine Island Glacier is a fast moving outlet glacier in the West Antarctic Ice Sheet. Several tributaries feeding the central ice stream characterise the flow field structure of this glacier. In the past decades the glacier has shown acceleration, thinning and a significant grounding line retreat. These ongoing processes are coinciding with a concentrated mass loss in the area around Pine Island Glacier, the Amundsen Sea Embayment. The area is of additional interest due to its retrograde bed slope. The postulated instability of the setting turns the glacier into an even more suitable object for modelling studies. One major challenge encountered when modelling the flow field of Pine Island Glacier is to reproduce the locally varying flow pattern, with its many tributaries. Commonly this difficulty is overcome by inversion for parameters controlling basal sliding. Our study is aimed at connecting basal sliding again to physical parameters. To achieve this we conduct experiments of Pine Island Glacier with the diagnostic 3D full-Stokes model COMice. The model is thermo-mechanically coupled and implemented with the commercial finite-element package COMSOL Multiphysics©. We use remotely sensed surface velocity data to validate our results. In a first step, the model is used to identify dominant local mechanisms that drive the flow of the different tributaries. We identify connections between the basal topography, the basal temperature, the driving stress and the basal roughness distribution. The thus gained information is used to confine basal sliding. Areas with similar qualitative characteristics are identified, and constant-sliding assumptions made for those. Additionally, the basal roughness distribution is matched onto a basal sliding parameter. This way the sliding law is again brought closer to its original meaning. Our results are important for prognostic model experiments, as we connect basal sliding to locally varying basal properties, which might lead to different responses of the tributaries to altered external forcing.
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  • 378
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    Ice Shelf-Ocean Interactions Near Ice Rises and Ice Rumples (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2013-12-09-2013-12-13
    Details
    Publication Date: 2016-12-15
    Description: The stability of ice shelves depends on the existence of embayments and is largely influenced by ice rises and ice rumples, which act as “pinning-points” for ice shelf movement. Of additional critical importance are interactions between ice shelves and the water masses underlying them in ice shelf cavities, particularly melting and refreezing processes. The present study aims to elucidate the role of ice rises and ice rumples in the context of climate change impacts on Antarctic ice shelves. However, due to their smaller spatial extent, ice rumples react more sensitively to climate change than ice rises. Different forcings are at work and need to be considered separately as well as synergistically. In order to address these issues, we have decided to deal with the following three issues explicitly: oceanographic-, cryospheric and general topics. In so doing, we paid particular attention to possible interrelationships and feedbacks in a coupled ice-shelf-ocean system. With regard to oceanographic issues, we have applied the ocean circulation model ROMBAX to ocean water masses adjacent to and underneath a number of idealized ice shelf configurations: wide and narrow as well as laterally restrained and unrestrained ice shelves. Simulations were performed with and without small ice rises located close to the calving front. For larger configurations, the impact of the ice rises on melt rates at the ice shelf base is negligible, while for smaller configurations net melting rates at the ice-shelf base differ by a factor of up to eight depending on whether ice rises are considered or not. We employed the thermo-coupled ice flow model TIM-FD3 to simulate the effects of several ice rises and one ice rumple on the dynamics of ice shelf flow. We considered the complete un-grounding of the ice shelf in order to investigate the effect of pinning points of different characteristics (interior or near calving front, small and medium sized) on the resulting flow and stress fields, focusing on the floating ice parts of the Brunt and Riiser-Larsen ice shelves. The major response of the ice is observed instantaneously and is caused by the time independent nature of the Stokes equations and the used Glen-type rheology. The influence of ice temperatures and therefore the time-dependent effect on the flow-rate are small, given a 100 year time frame and applying a fixed-geometry setting.. A particularly important result of the current project lies in the fact that we have numerically simulated the three-dimensional stress fields in an ice shelf. Common numerical models that utilize a vertically integrated Shallow Shelf Approximation (SSA-models), do not provide that information. Due to the detailed horizontal resolution of 1km in our models, we were able to also model the observed heavily fractured areas in the vicinity of McDonald Ice Rise, a region that is characterized by simulated tensile stresses reaching maximum vertical extension in the ice column.
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    Expert assessment of vulnerability of permafrost carbon to climate change (2013)
    In:  EPIC3Climatic Change, 119(2), pp. 359-374, ISSN: 0165-0009
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    Publication Date: 2016-12-13
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  • 380
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    Decline, recovery, and site persistence of intertidal seagrass beds in the Northern Wadden Sea (SE North Sea) since the 1930s (2013)
    In:  EPIC3European Geosciences Union - General Assembly 2013, Vienna, Austria, 2013-04-07-2013-04-12
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    Publication Date: 2017-01-04
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  • 381
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    Die Entwicklung intertidaler Seegrasbestände im nördlichen Wattenmeer in den letzten 80 Jahren (2013)
    In:  EPIC331. Jahrestagung des Arbeitskreises „Geographie der Meere und Küsten“, Cologne, Germany, 2013-04-18-2013-04-21
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    Publication Date: 2017-01-04
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  • 382
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    Schleswig-Holstein Wadden Sea Assessment of Phytobenthos (SHWAP) – die ersten 6 Jahre (2013)
    In:  EPIC3Symposium des Landesamts für Landwirtschaft, Umwelt und ländliche Räume, Flintbek, Germany, 2013-03-19
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    Publication Date: 2017-01-04
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  • 383
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    Die Beständigkeit eulitoraler Seegraswiesen im nördlichen Wattenmeer seit den 1930er Jahren (2013)
    In:  EPIC3Einladung zum Dialog: Küstenforschung, Küstennutzung und Küstenschutz, Hamburg, Germany, 2013-03-04-2013-03-06
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    Publication Date: 2017-01-04
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  • 384
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    Tolerance of Hyas araneus zoea I larvae to elevated seawater PCO2 despite elevated metabolic costs (2013)
    Springer
    In:  EPIC3Marine Biology, Springer, 160(8), pp. 1943-1953
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    Publication Date: 2017-01-16
    Description: Early life stages of marine crustaceans respond sensitively to elevated seawater PCO2. However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated seawater PCO2 on oxygen consumption, dry weight, elemental composition, median developmental time (MDT) and mortality in zoea I larvae of the spider crab Hyas araneus (Svalbard 79°N/11°E; collection, May 2009; hatch, December 2009). At the time of moulting, oxygen consumption rate had reached a steady state level under control conditions. In contrast, elevated seawater PCO2 caused the metabolic rate to rise continuously leading to a maximum 1.5-fold increase beyond control level a few days before moulting into the second stage (zoea II), followed by a pronounced decrease. Dry weight of larvae reared under high CO2 conditions was lower than in control larvae at the beginning of the moult cycle, yet this difference had disappeared at the time of moulting. MDT of zoea I varied between 45 ± 1 days under control conditions and 42 ± 2 days under the highest seawater CO2 concentration. The present study indicates that larval development under elevated seawater PCO2 levels results in higher metabolic costs during premoulting events in zoea I. However, H. araneus zoea I larvae seem to be able to compensate for higher metabolic costs as larval MDT and survival was not affected by elevated PCO2 levels.
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  • 385
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    Physiological response and mitochondrial adaptations to changing abiotic factors in Antarctic fish and cephalopods (2013)
    Staats- und Universitätsbibliothek Bremen
    In:  EPIC3Staats- und Universitätsbibliothek Bremen
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    Publication Date: 2017-01-10
    Description: Antarctic species possess very low metabolic rates and poor capacities to change their physiological state, thus making them extremely vulnerable to changing environmental conditions. Mitochondria are a key element in shaping whole organism energy turnover and functional capacity. In my study, the effects of rising temperature and increased seawater PCO2 on the energy metabolism were compared between various nototheniids from sub-Antarctic and cold-temperate and Antarctic waters, and between cephalopods from the Antarctic and temperate latitudes. I determined extra- and intracellular blood carbonate parameters, enzymatic capacities and oxygen consumption at whole animal and mitochondrial level and mitochondrial lipid composition and proton leak as a measure for routine metabolic rate, in order to compare their abilities for metabolic compensation towards climate change. My results showed limited aerobic capacities of high-Antarctic fish mitochondria towards the warmth and higher CO2-levels. The mitochondrial responses of cephalopods to an acute temperature rise suggest that they possess similar mitochondrial flexibilities and capacities towards the warmth as fish. Nevertheless, generally more effective capacities for acid-base regulation and larger energy reserves (lipids) in fish compared to cephalopods will putatively make them win the competition for resources over longer time-scales, when seawater temperatures and PCO2 continue to rise.
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  • 386
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    Evolution of cephalopod haemocyanin in a biogeographic context (2013)
    In:  EPIC3
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    Publication Date: 2017-01-10
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  • 387
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    Das Alfred Wegener Institut und die Helmholtz Nachwuchsgruppe PLANKTOSENS (2013)
    In:  EPIC3Kleine Exkursion WS 2012/203, Universität Osnabrück, Prof. Altendorf
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    Publication Date: 2017-01-09
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  • 388
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    Das Alfred Wegener Institut und die Helmholtz Nachwuchsgruppe PLANKTOSENS (2013)
    In:  EPIC3Kleine Exkursion SS 2013, Universität Osnabrück, Prof. Altendorf
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    Publication Date: 2017-01-09
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  • 389
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    Das Alfred Wegener Institut und die Helmholtz Nachwuchsgruppe PLANKTOSENS (2013)
    In:  EPIC3Kleine Exkursion WS 2013/2014, Universität Osnabrück, Prof. Altendorf
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    Publication Date: 2017-01-09
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  • 390
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    Plankton Ecology at AWI Polar Biological Oceanography - Arctic Ocean (2013)
    In:  EPIC3Kleine Exkursion WS 2013/2014, Universität Osnabrück, Prof. Altendorf
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    Publication Date: 2017-01-26
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  • 391
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    Moytirra: Discovery of the first known deep-sea hydrothermal vent field on the slow-spreading Mid-Atlantic Ridge north of the Azores (2013)
    In:  EPIC3Geochemistry, Geophysics, Geosystems, 14(10), pp. 4170-4184
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    Publication Date: 2017-01-16
    Description: Geological, biological, morphological and hydrochemical data are presented for the newly discovered Moytirra vent field at 45oN. This is the only high temperature hydrothermal vent known between the Azores and Iceland, in the North Atlantic and is located on a slow to ultraslow-spreading mid-ocean ridge uniquely situated on the 300 m high fault scarp of the eastern axial wall, 3.5 km from the axial volcanic ridge crest. Furthermore, the Moytirra vent field is, unusually for tectonically controlled hydrothermal vents systems, basalt hosted and perched mid-way up on the median valley wall and presumably heated by an off-axis magma chamber. The Moytirra vent field consists of an alignment of four sites of venting, three active emitting “black smoke", producing a complex of chimneys and beehive diffusers. The largest chimney is 18 m tall and vigorously venting. The vent fauna described here are the only documented for the North Atlantic (Azores to Reykjanes Ridge) and significantly expands our knowledge of North Atlantic biodiversity. The surfaces of the vent chimneys are occupied by aggregations of gastropods (Peltospira sp.) and populations of alvinocaridid shrimp (Mirocaris sp. with Rimicaris sp. also present). Other fauna present include bythograeid crabs (Segonzacia sp.) and zoarcid fish (Pachycara sp.), but bathymodiolin mussels and actinostolid anemones were not observed in the vent field. The discovery of the Moytirra vent field therefore expands the known latitudinal distributions of several vent-endemic genera in the north Atlantic, and reveals faunal affinities with vents south of the Azores rather than north of Iceland.
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    Online monitoring of temperature-dependent cell metabolism of primary hepatocytes from Antarctic fish species (2013)
    In:  EPIC3XI SCAR Biology Symposium, Barcelona, Spain, 2013-07-14-2013-07-19
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    Publication Date: 2017-01-17
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  • 393
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    Isolation von fraßinduzierenden Botenstoffen der Braunalge Fucus vesiculosus mittels Diaon HP20 (2013)
    In:  EPIC345 p.
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    Publication Date: 2017-01-20
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  • 394
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    Role of scavenging on growth, behaviour, and reproduction of the common periwinkle (Littorina littorea) (2013)
    In:  EPIC349 p.
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    Publication Date: 2017-01-20
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  • 395
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    Eastern Pacific background state and tropical South American climate history during the last 3 million years (2013)
    http://www.suub.uni-bremen.de
    In:  EPIC3http://www.suub.uni-bremen.de, 219 p.
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    Publication Date: 2016-12-22
    Repository Name: EPIC Alfred Wegener Institut
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  • 396
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    Plankton Ecology at AWI Polar Biological Oceanography - Arctic Ocean (2013)
    In:  EPIC3Kleine Exkursion SS 2013, Universität Osnabrück, Prof. Altendorf
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    Publication Date: 2017-01-26
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  • 397
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    Bearbeitung von Vibroseis-Messungen zur Erkundung des Firns an der Kohnen Station, Antarktis (2013)
    In:  EPIC3
    Details
    Publication Date: 2017-01-25
    Description: Um Aussagen �uber das Klima der Vergangenheit tre�en zu k�onnen oder �Anderungen im Meeresspiegel vorhersagen zu k�onnen, ist es wichtig die Dynamik und den inneren Aufbau von Gletschern und Eisschilden zu verstehen. Deshalb verwendet die LIMPICS Forschungsgruppe geophysikalische Methoden um physikalische Eigenschaften im Eis zu bestimmen. Mit Hilfe von seismischen Re exionsverfahren werden Re exionen im Eis untersucht, die durch �Anderungen in den physikalischen Eigenschaften verursacht werden. Daf�ur werden Messungen in den Alpen und in der Antarktis durchgef�uhrt. Die Expedition zur Kohnen Station fand 2011/12 statt und hatte das Ziel mit Hilfe der seismischen Messungen physikalische Eigenschaften des Eises, wie z.B. die Dichte, die Temperatur oder die Orientierung der anisotropen Eiskristalle zu untersuchen, um diese Ergebnisse mit denen eines nahegelegenen Eiskerns zu vergleichen. Zus�atzlich sollten die Eigenschaften des Felsbettes unter dem Eis bestimmt werden. Zur Untersuchung des Firnbereiches wurden Messungen mit dem Mikrovibrator ELVIS III durchgef�uhrt. Mit ELVIS III wurden zwei senkrecht zueinander liegende seismische Pro�le, jeweils f�ur die P- und S-Welle, gemessen. In dieser Arbeit wurden die Vertiakalkomponenten der P-Wellen-Pro�le ausgewertet. Mit der Auswertung der Daten, sollte herausgefunden ob interne Re exionen in den Daten zu sehen sind und bis in welche Tiefe diese Re exionen erkennbar sind. Insbesondere sollte damit auch herausgefunden werden bis in welche Tiefe die mit dem Mikrovibrator ELVIS III eingebrachte Energie reicht, um Re exionen au �osen zu k�onnen. Die Energie des Mikrovibrators reicht aus um Re exionen bis in eine Tiefe von 500 m sichtbar zu machen. Allerdings konnten nur in einem der beiden P-Wellen-Pro�le Re exionen erkannt werden. Diese Re exionen konnten im Firnpaket bis 100 m und im Eis von 100-500 m festgestellt werden. Re exionen im Firnbereich werden durch Dichtespr �unge im Firn verursacht. Im Eis, unter dem Firn, treten keine signi�kanten Dichteunterschiede mehr auf, deshalb k�onnen im Eis keine Dichte�anderungen Re- exionen verursachen. M�ogliche Eigenschaften die Re exionen im Eis verursachen werden in Kapitel 5 diskutiert. Zum besseren Verst�andnis von seismischen Messungen im Eis werden in Kapitel 2 die Grundlagen �uber die Entstehung von Eis, die Grundlagen seismischer Wellen und deren Geschwindigkeiten, sowie die Grundlagen der Vibrationsseismik erl�autert. Die Messgeometrie sowie die Funktion der Messger�ate in Kapitel3 sind ein wichtiger Faktor daf�ur, ob das Signal-Rausch-Verh�altnis ausreichend gut verbessert werden kann. Ebenfalls k�onnen gute Ergebnisse durch die richtige Bearbeitung seismischer Daten erzielt werden. Die Theorie dazu, sowie die Auswertung der Messungen sind in Kapitel 4 beschrieben. Kapitel 5 enth�alt die Ergebnisse der Auswertung und die Beschreibung der m�oglichen Gr�unde f�ur das Ergebnis.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
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  • 398
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    Der Einfluss von Spurenstoffen auf die Verdichtung von grönländischem Firn (2013)
    In:  EPIC3
    Details
    Publication Date: 2019-07-17
    Description: Firn cores from different locations in North Greenland are investigated to analyse the influence of the accumulation rate and the impurities on the densification. The drilling regions have similar mean annual temperatures, but significantly different rates of ac-cumulation. In this study the density profiles of three firn cores are measured with the new established method of X-ray radioscopy. These and six other density profiles from previous studies are used to find some general pattern of densification in North Green-land. The influence of impurities on densification are analysed by considering the calci-um and dust concentrations for one firn core measured in the framework of an ongoing PhD-work and by measuring also the sodium, nitrate and ammonium concentrations for particular sections of the three firn cores with the means of continuous flow analysis. The classic densification model by Herron and Langway [1980] and the model by Freitag et al [2013], which is extended with the effect of impurities, are used to simulate the density and the density variability. It is shown that in North Greenland the densification of firn is different for high and low accumulation rates. The accumulation rate affects the depth profile of the density variability leading to profiles with a minimum and a second maximum at high and to uniform plateau-like profiles at low accumulation rates. This implies that for regions with high accumulation rate a strong phase relationship between the density and the dust concentration at the snow surface exists, which is inversed. Consequently, the density at the snow surface has a seasonal signal. In contrast, regions with lower accumulation rate have no strong phase relationship, so that the density of the snow surface has no seasonal behavior. With increasing depth the density follows the seasonal depth profile of the impurities. Both, the model by Herron and Langway [1980] and the model by Freitag et al. [2013] simulate the mean density profile, whereas the density variability was only reproduced by the extended model of Freitag et al. [2013].
    Repository Name: EPIC Alfred Wegener Institut
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  • 399
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    The environment ontology: contextualising biological and biomedical entities (2013)
    In:  EPIC3Journal of Biomedical Semantics, 4(1), pp. 43, ISSN: 2041-1480
    Details
    Publication Date: 2017-01-30
    Description: As biological and biomedical research increasingly reference the environmental context of the biological entities under study, the need for formalisation and standardisation of environment descriptors is growing. The Environment Ontology (ENVO; http://www.environmentontology.org) is a community-led, open project which seeks to provide an ontology for specifying a wide range of environments relevant to multiple life science disciplines and, through an open participation model, to accommodate the terminological requirements of all those needing to annotate data using ontology classes. This paper summarises ENVO’s motivation, content, structure, adoption, and governance approach. The ontology is available from http://purl.obolibrary.org/obo/envo.owl - an OBO format version is also available by switching the file suffix to “obo”.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev , info:eu-repo/semantics/article
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    Molecular composition of dissolved organic matter from a wetland plant (Juncus effusus) after photochemical and microbial decomposition (1.25 yr): Common features with deep sea dissolved organic matter (2013)
    In:  EPIC3Organic Geochemistry
    Details
    Publication Date: 2017-01-31
    Description: We hypothesized that microbial and photochemical processing of dissolved organic matter (DOM) determines its molecular formula composition in aquatic systems to a greater degree than does the original source of the DOM. To test this hypothesis, we exposed DOM from a leachate of a wetland plant (Juncus effusus) to solar radiation or incubated it in the dark for 1.25 yr. Analysis of the extracted DOM of the leachates via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) identified 2800 molecular formulae. Of the formulae in the initial DOM, 11% were lost during microbial decomposition in the dark and 54% under solar radiation. Solar radiation also produced a large number of formulae containing N, that were preferentially degraded by microorganisms (47% loss). We compared the “recalcitrant formulae”, i.e. those not degraded in the experiment, with those of DOM from the deep North Pacific Ocean. Of the deep sea DOM formulae, 18% were present in the recalcitrant fraction of the initial DOM. An additional 18% of the formulae in marine DOM were photoproduced and recalcitrant, and 8% were produced by microbes in the experiment. Consequently, 44% of the deep sea DOM shares identical molecular formulae with the recalcitrant DOM from the experiment, most of which were produced by the combined action of sunlight and microbes. This indicates that processes in the water column may be more important than the original source in determining the composition of bulk DOM.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev , info:eu-repo/semantics/article
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