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  • 201
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    Floating ice-algal aggregates below melting Arctic sea ice (2013)
    In:  EPIC3Plos One, 8(10), pp. e76599
    Details
    Publication Date: 2014-09-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 202
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    Pliocene warmth, polar amplification and stepped Pleistocene cooling recorded in NE Arctic Russia (2013)
    In:  EPIC3Science, 340, pp. 1421-1427
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 203
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    A MIS 3 charcoal and pollen record and quantitative precipitation inferences from the Jingerwa section of the Nihewan Basin, north-central China. (2013)
    SPRINGER
    In:  EPIC3Journal of Paleolimnology, SPRINGER, ISSN: 0921-2728
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    Publication Date: 2019-07-17
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  • 204
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    Analysis of effects of climate-dependent factors on the formation of zooplankton communities that inhabit Arctic lakes in the Anabar River Basin. (2013)
    SPRINGER
    In:  EPIC3Contemporary Problems of Ecology, SPRINGER, 6, pp. 1-11, ISSN: 1995-4255
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    Publication Date: 2019-07-17
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  • 205
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    Core-scale radioscopic imaging: a new method reveals density-calcium link in Antarctic firn (2013)
    In:  EPIC3J. Glaciol., 59(218), pp. 1009-1014
    Details
    Publication Date: 2017-02-08
    Description: ABSTRACT. A new radioscopic imaging technique has been developed to measure firn density in unprecedented resolution and accuracy even when the porosity is low or the geometry of a core or piece of core is not perfect. The technique is based on an X-ray microfocus computer tomograph (ICE-CT) designed especially for ice-core applications. Applied on an archive piece of the Antarctic firn core B32 drilled in Dronning Maud Land in 1998, the obtained density profile shows a strong correlation with the calcium ion concentration as found previously in Greenland. Given the impurity–density relationship found previously in Greenland, our result suggests both improved accuracy of the new density measurements and an impurity–density relationship with a similar magnitude in Greenland to that on the Antarctic plateau. Our measurements provide first evidence that the impurity–density relationship is a universal feature of polar firn and that the calcium ion concentration can serve as a proxy to describe quantitatively the effect of the impurities on densification.
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  • 206
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    Stable water isotopes in the coupled atmosphere-land surface model ECHAM5-JSBACH (2013)
    In:  EPIC3Geoscientific Model Development, 6, pp. 1463-1480
    Details
    Publication Date: 2019-07-17
    Description: In this study we present first results of a new model development, ECHAM5-JSBACH-wiso, where we have incorporated the stable water isotopes H218O and HDO as tracers in the hydrological cycle of the coupled atmosphere–land surface model ECHAM5-JSBACH. The ECHAM5-JSBACH-wiso model was run under present-day climate conditions at two different resolutions (T31L19, T63L31). A comparison between ECHAM5-JSBACH-wiso and ECHAM5-wiso shows that the coupling has a strong impact on the simulated temperature and soil wetness. Caused by these changes of temperature and the hydrological cycle, the δ18O in precipitation also shows variations from −4‰ up to 4‰. One of the strongest anomalies is shown over northeast Asia where, due to an increase of temperature, the δ18O in precipitation increases as well. In order to analyze the sensitivity of the fractionation processes over land, we compare a set of simulations with various implementations of these processes over the land surface. The simulations allow us to distinguish between no fractionation, fractionation included in the evaporation flux (from bare soil) and also fractionation included in both evaporation and transpiration (from water transport through plants) fluxes. While the isotopic composition of the soil water may change for δ18O by up to +8‰:, the simulated δ18O in precipitation shows only slight differences on the order of ±1‰. The simulated isotopic composition of precipitation fits well with the available observations from the GNIP (Global Network of Isotopes in Precipitation) database.
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  • 207
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    Mid-Pliocene East Asian monsoon climate simulated in the PlioMIP (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Climate of the Past, COPERNICUS GESELLSCHAFT MBH, 9, pp. 2085-2099, ISSN: 1814-9324
    Details
    Publication Date: 2017-06-14
    Description: Based on simulations with 15 climate models in the Pliocene Model Intercomparison Project (PlioMIP), the regional climate of East Asia (focusing on China) during the mid-Pliocene is investigated in this study. Compared to the pre-industrial, the multi-model ensemble mean (MMM) of all models shows the East Asian summer winds (EASWs) largely strengthen in monsoon China, and the East Asian winter winds (EAWWs) strengthen in south monsoon China but slightly weaken in north monsoon China in the mid-Pliocene. The MMM of all models also illustrates a warmer and wetter mid-Pliocene climate in China. The simulated weakened mid-Pliocene EAWWs in north monsoon China and intensified EASWs in monsoon China agree well with geological reconstructions. However, there is a large model–model discrepancy in simulating mid-Pliocene EAWW, which should be further addressed in the future work of PlioMIP.
    Repository Name: EPIC Alfred Wegener Institut
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  • 208
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    Weekly report for R.V. Polarstern expedition ANT-XXIX/7, report no. 1, german version (2013)
    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Alfred-Wegener-Institute for Polar- and Marine Research, Bremerhaven, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research
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    Publication Date: 2014-11-28
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  • 209
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    LOCAL TO BASIN SCALE ARRAYS FOR PASSIVE ACOUSTIC MONITORING IN THE ATLANTIC SECTOR OF THE SOUTHERN OCEAN (2013)
    In:  EPIC3International Conference and Exhibition on Underwater Acoustics, Corfu Island, Greece, 2013-06-23-2013-06-28Corfu Island, Greece
    Details
    Publication Date: 2019-07-17
    Description: Passive acoustic data provide a prime source of information on marine mammal distribution and behaviour. Particularly in the Southern Ocean, where ship-based data collection can be severely hampered by weather and ice conditions, passive acoustic monitoring (PAM) of marine mammals forms an important source of year-round information on acoustic presence. Array data can be used to obtain directional information on the species present in the recordings to derive movement patterns. Acoustic arrays furthermore allow spatial comparisons of marine mammal distribution patterns and habitat affinities when the acoustic presence information is linked to local environmental parameters. Here we present two passive acoustic monitoring arrays that have been implemented by the Alfred Wegener Institute’s Ocean Acoustic Lab and serve the investigation of marine mammals on different spatial scales. During the austral summer season 2012/2013 a local scale array of sea ice-based time-synchronized passive acoustic recorders was deployed in Atka Bay, Antarctica. The PASATA (PASsive Acoustic Tracking of Antarctic marine mammals) project investigates coastal local habitat usage and communication ranges of marine mammals by integrating positional information from triangulation of calling animals and information from environmental parameters. For studies on marine mammals over larger spatial scales, 23 passive acoustic recorders were deployed in oceanographic moorings in the Southern Ocean, reaching from the Greenwich meridian throughout the Weddell Sea to the Western Antarctic Peninsula. The inter-disciplinary nature of this mooring array allows combining in-situ oceanographic measurements with passive acoustic data on marine mammal occurrence. It furthermore forms the first basin-wide, long term array, at least in the Southern Ocean. Here, we describe both arrays, the recorder types used, and technical and logistic requirements for PAM in a polar environment.
    Repository Name: EPIC Alfred Wegener Institut
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  • 210
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    Thermo-erosional landforms in Siberian ice-rich permafrost (2013)
    In:  EPIC38th International Conference (IAG) on Geomorphology, Paris, France, 2013-08-27-2013-08-31
    Details
    Publication Date: 2019-07-17
    Description: Of major concern in periglacial research is the question of how arctic permafrost landscapes react to climate change. Warming and thawing of ice-rich permafrost may result in substantial hydrological, geomorphological, ecological, and biogeochemical feedbacks which may have local to global impacts. While numerous studies have investigated thermokarst as one main process of permafrost degradation, data is sparse on thermal erosion, another widespread process of permafrost degradation. Siberian coastal lowlands underlain by ice-rich permafrost often feature streams, valleys, and valley networks that have formed under the influence of thermal erosion, but systematic regional studies have been lacking. We present an inventory of streams and valleys in three ice-rich lowland areas adjacent to the Laptev Sea using GIS-based analysis of remote sensing data, elevation models, and field investigations. The calculated total stream length is 4,153 km in the Cape Mamontov Klyk area, 1,541 km in the Lena River Delta area, and 2,047 km in the Buor Khaya Peninsula area; valley densities are 1.8, 0.9, and 1.0 km/km², respectively. Strong variations in the morphology and spatial distribution of streams and valleys are observed and can be attributed to differences in the size and relief characteristics of the study areas as well as to their predominant cryolithological properties, which are also influenced by previous degradation of the study areas by thermokarst. Based on the results, the evolution of different valley types in continuous ice-rich permafrost landscapes is discussed. The current valley pattern is largely the result of the late Holocene evolution of the hydrological system that is strongly connected to the degradation of ice-rich permafrost by thermal erosion.
    Repository Name: EPIC Alfred Wegener Institut
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  • 211
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    LOCAL TO BASIN SCALE ARRAYS FOR PASSIVE ACOUSTIC MONITORING IN THE ATLANTIC SECTOR OF THE SOUTHERN OCEAN (2013)
    In:  EPIC3Corfu Island, Greece, 1686 p., ISBN: 978-618-80725-0-3
    Details
    Publication Date: 2014-04-15
    Description: Passive acoustic data provide a prime source of information on marine mammal distribution and behaviour. Particularly in the Southern Ocean, where ship-based data collection can be severely hampered by weather and ice conditions, passive acoustic monitoring (PAM) of marine mammals forms an important source of year-round information on acoustic presence. Array data can be used to obtain directional information on the species present in the recordings to derive movement patterns. Acoustic arrays furthermore allow spatial comparisons of marine mammal distribution patterns and habitat affinities when the acoustic presence information is linked to local environmental parameters. Here we present two passive acoustic monitoring arrays that have been implemented by the Alfred Wegener Institute’s Ocean Acoustic Lab and serve the investigation of marine mammals on different spatial scales. During the austral summer season 2012/2013 a local scale array of sea ice-based time-synchronized passive acoustic recorders was deployed in Atka Bay, Antarctica. The PASATA (PASsive Acoustic Tracking of Antarctic marine mammals) project investigates coastal local habitat usage and communication ranges of marine mammals by integrating positional information from triangulation of calling animals and information from environmental parameters. For studies on marine mammals over larger spatial scales, 23 passive acoustic recorders were deployed in oceanographic moorings in the Southern Ocean, reaching from the Greenwich meridian throughout the Weddell Sea to the Western Antarctic Peninsula. The inter-disciplinary nature of this mooring array allows combining in-situ oceanographic measurements with passive acoustic data on marine mammal occurrence. It furthermore forms the first basin-wide, long term array, at least in the Southern Ocean. Here, we describe both arrays, the recorder types used, and technical and logistic requirements for PAM in a polar environment.
    Repository Name: EPIC Alfred Wegener Institut
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  • 212
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    How is chlorine activation affected by the composition of Polar Stratospheric Clouds and background aerosol particles? (2013)
    In:  EPIC3SSiRC Workshop, Atlanta, Georgia, United States, 2013-10-28-2013-10-30
    Details
    Publication Date: 2019-07-16
    Description: We investigate how important details of the microphysics of Polar Stratospheric Clouds (PSCs) and background aerosol particles are for the representation of polar ozone loss in chemistry transport models. For this purpose, the Lagrangian Chemistry and Transport Model ATLAS was applied to simulate the stratospheric chemistry in the Arctic winter 2009/2010. After a validation of the model results against measurements by the satelliteborne Microwave Limb Sounder (MLS), a number of sensitivity runs were performed. Thus, the efficiency of chlorine activation on different types of liquid aerosols versus activation on nitric acid trihydrate (NAT) clouds was explored. Moreover, the effects of particle composition and denitrification on ozone loss were analysed. It is shown that even large changes in the underlying assumptions regarding detailed activation surfaces have only a small impact on the modelled ozone loss. Differences in column ozone between the various sensitivity runs remain below 10% at the end of the winter. Chlorine activation on liquid aerosols alone is able to explain the observed magnitude and morphology of the mixing ratios of active chlorine, reservoir gases and ozone. This is even true for cold binary aerosols (no uptake of HNO3 from the gas-phase allowed in the model). This demonstrates that the heterogeneous chlorine activation in the polar stratosphere is dominated by the temperature dependence of the heterogeneous reaction rate constants rather than by the composition of the solid or liquid aerosol particles.
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  • 213
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    SST and salinity patterns in the northern North Atlantic and the Arctic during interglacial MIS 11c: Implications for oceanic circulation reconstruction (2013)
    In:  EPIC3AGU Fall Metting, San Francisco, 2013-12-09-2013-12-13
    Details
    Publication Date: 2019-07-16
    Description: Sea surface temperature (SST) patterns in the northern North Atlantic, the Nordic seas, and the western Arctic Ocean (AO) were reconstructed across MIS 11c, a potential future climate analogue, using planktic foraminiferal abundances, alkenone-based Uk’37 and glycerol dialkyl glycerol tetraether (GDGT)-based TEX86 analyses, where possible. SSTforam reconstructions were supported by foraminiferal counts of small-sized fractions and rare foraminiferal species, stable oxygen isotope measurements on benthic and planktic foraminiferal species, and ice rafted debris (IRD) records. Additionally, the hydrogen isotopic (δD) compositions of long chain alkenones were determined to assess variations in paleo sea surface salinity in the North Atlantic. The preliminary alkenone δD data show that during MIS 11c salinity values in the North Atlantic were similar to Holocene values. In the North Atlantic our newly produced TEX86 –based SSTs range between 14 and 19 °C in agreement with summer SSTforam (13 and 18 °C) and alkenone SSTs (13 and 16 °C). However, the former showed higher fluctuations than SSTs based on foraminiferal abundances. In concordance with δ18O records TEX86 SSTs demonstrate notable variability in the middle of MIS 11c, between 400 and 410 ka, which we tentatively correlate with an intra-MIS 11c cold event occurring in the Arctic as we previously detected. This implies that MIC 11c climate was probably not as stable as it was believed before. SSTforam records imply that during MIS 11c parts of the AO experienced unusually warm, ice free conditions, whereas the Nordic seas remained rather cold, especially during the early phase of this period, as it is inferred from foraminiferal and alkenone SSTs. At the same time all our SST records show that the North Atlantic was 1-2°C warmer than present during MIS 11c. This pattern suggests that during MIS 11c the North Atlantic Current was deflected to the west, which intensified the subpolar gyre and that, therefore, less warm water was transported to the Nordic seas. Consequently, warm water transport from the Nordic seas to the Arctic was also reduced relative to the modern situation and proportionally more water entered the Arctic from the Pacific Ocean.
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  • 214
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    Impact of climate change on the distribution of sponges and cold water corals in the Antarctic and Subantarctic (2013)
    In:  EPIC3154 p.
    Details
    Publication Date: 2019-07-17
    Description: Climate change and ocean acidification, fuelled by the release of anthropogenic carbon dioxide in the atmosphere, impact the physico-chemical dynamics of the ocean. Current changes are undeniable and their rate is believed to be much faster than anywhere else in the geological records. Modifications of the seawater temperature and pH, amongst other parameters, impact marine organisms across all levels of biological organisation and extinctions or shifts in the distributional range of several species are expected. Unable to escape the alteration of their environment, sedentary benthic organisms are particularly exposed. The fate of corals and sponges, the main habitat-forming species in the benthos, is considered critical because of their aragonite skeleton (corals) and slow growth (sponges). In this thesis, I intended to estimate the impact of climate change and ocean acidification on the distribution of sponges and cold water corals in the Antarctic and the Subantarctic. For this purpose I focused on two main case studies: -Case study I: Climate-induced changes in megabenthic communities along the Antarctic Peninsula and their consequences on the distribution of glass sponges. -Case study II: Sensitivity of the cold water coral Desmophyllum dianthus to ocean acidification inferred from its distribution along a pH gradient in a Chilean fjord. In both cases, I chose to work mainly with non-destructive sampling devices, namely Remotely Operated Vehicles (ROVs) acquiring underwater videos for quantification of the benthos and simultaneously recording several physico-chemical parameters. For monitoring purposes a standardized method was needed to obtain comparable abundance data from videos recorded by different vehicles. Case study I (=〉 Manuscript I and Manuscript II) On the Antarctic continental shelf, glass sponges (Porifera, Hexactinellida) are a dominant component of rich megabenthic communities sustained by the seasonal melting of sea-ice and the resulting phytoplankton blooms. Under permanent ice shelves, however, a depauperate deep-sea like fauna survives in oligotrophic waters, relying on the advection of allochtonous food. The catastrophic collapse of ice shelves attributed to rapid regional warming along the Antarctic Peninsula is creating new conditions in the formerly permanently ice-covered water column. In the south of the Larsen A embayment, a ROV transect conducted in 2007 was repeated in 2011 to monitor the evolution of the benthic life after the collapse of the overlaying ice shelf in 1995. A slow response of the Antarctic benthos was expected but, in only four years, a rapid successional pattern was observed with pioneer ascidians quickly colonizing the area, becoming dominant and then collapsing completely to the advantage of a new population of glass sponges. The ophiuroids at the site shifted simultaneously from a population of abundant filter-feeders to a dominance of deposit-feeders. Sustained by a low predation pressure, the reduced competition for space and food and the new but irregular supply of pelagic organic material, hexactinellid sponges nearly doubled their biomass and abundance in Larsen A between both surveys. These unexpected results, together with findings from other studies, imply a paradigm shift in the consideration of Antarctic benthic dynamics, where glass sponges may undergo boom and bust cycles, allowing them to quickly colonize new habitats. If the current rate of ice shelf retreat continues, hexactinellids may spread along the Antarctic Peninsula and thus find themselves on the winners’ side of climate change. Case study II (=〉 Manuscript III) Cold water corals (CWC) occur primarily in the deep-sea, where they provide habitat for a rich reef-associated benthic fauna. In spite of gaps in our knowledge of their ecology and physiology, these invertebrates are considered extremely sensitive to ocean acidification. Due to the remoteness of their natural environment investigations into their response to natural variations of the seawater carbonate chemistry or to artificially elevated pH in experimental setups are rare. In Comau Fjord, in Chilean Patagonia, an exceptionally shallow population of the CWC Desmophyllum dianthus is known to dwell across a wide pH gradient. We deployed a ROV at seven sites across this fjord, in order to quantitatively assess the vertical and horizontal distribution of D. dianthus and determine the physico-chemical parameters driving its occurrence. None of the recorded parameters seems to be a major controller of the abundance, distribution or size of this coral. D. dianthus is ubiquitous in the fjord, occurring in high abundances down to 280 m depth at a pH 〈 7.8. Below this depth, this coral is still present in smaller and less dense patches in a suboxic water mass with low pH. Our findings show that D. dianthus can survive and even prosper in aragonite undersaturated waters. However, its sensitivity to other alterations linked to climate change remains unknown. Methodology (=〉 Manuscript IV) For the quantitative analyses of video transects, a major difficulty exists in the determination of the area surveyed. Depending on the substrate topography, camera orientation and the availability of reference scales, several methods can be employed for the scaling of underwater images. The task is particularly difficult when comparing data originating from several vehicles. Despite a decidedly time-consuming procedure, 3-D modelling of the seafloor based on video data and a reference scale emerged as a powerful tool for standardized analysis of images obtained by three different ROVs. To date, it also is the only scaling method offering the possibility of integrating small scale topography to the measurements.
    Repository Name: EPIC Alfred Wegener Institut
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  • 215
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    Weekly report for R.V. Polarstern expedition ANT-XXIX/7, report no. 2, german version (2013)
    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Alfred-Wegener-Institute for Polar- and Marine Research, Bremerhaven, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research
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    Publication Date: 2014-11-28
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  • 216
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    Weekly report for R.V. Polarstern expedition ANT-XXIX/7, report no. 3, german version (2013)
    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Alfred-Wegener-Institute for Polar- and Marine Research, Bremerhaven, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research
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    Publication Date: 2014-11-28
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  • 217
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    Deglaciation of the West Antarctic continental shelf in the Amundsen Sea sector since the Last Glacial Maximum (2013)
    Deutsche Gesellschaft für Polarforschung
    In:  EPIC3Changing Polar Regions - 25th International Congress on Polar Research, Hamburg, 2013-03-17-2013-03-22Bremerhaven, Deutsche Gesellschaft für Polarforschung
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    Publication Date: 2018-08-10
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  • 218
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    Decadal- to millennial-scale ice-sheet oscillations in southerstern Weddell Sea during the Last Glacial Maximum (2013)
    Deutsche Gesellschaft für Polarforschung
    In:  EPIC3Changing Polar Regions - 25th International Congress on Polar Research, Hamburg, 2013-03-17-2013-03-22Bremerhaven, Deutsche Gesellschaft für Polarforschung
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    Publication Date: 2018-08-10
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  • 219
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    CryoSat‐2 estimates of Arctic sea ice thickness and volume (2013)
    AMER GEOPHYSICAL UNION
    In:  EPIC3Geophysical Research Letters, AMER GEOPHYSICAL UNION, 40(4), pp. 732-737, ISSN: 0094-8276
    Details
    Publication Date: 2017-10-17
    Description: Satellite records show a decline in ice extent over more than three decades, with a record minimum in September 2012. Results from the Pan-Arctic Ice-Ocean Modelling and Assimilation system (PIOMAS) suggest that the decline in extent has been accompanied by a decline in volume, but this has not been confirmed by data. Using new data from the European Space Agency CryoSat-2 (CS-2) mission, validated with in situ data, we generate estimates of ice volume for the winters of 2010/11 and 2011/12. We compare these data with current estimates from PIOMAS and earlier (2003–8) estimates from the National Aeronautics and Space Administration ICESat mission. Between the ICESat and CryoSat-2 periods, the autumn volume declined by 4291 km3 and the winter volume by 1479 km3. This exceeds the decline in ice volume in the central Arctic from the PIOMAS model of 2644 km3 in the autumn, but is less than the 2091 km3 in winter, between the two time periods.
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  • 220
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    Index description in "Mid-Holocene multiproxy compilation for eastern South America" (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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  • 221
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    Rates of apical septal extension of Desmophyllum dianthus: effect of association with endolithic photo-autotrophs (2013)
    SPRINGER
    In:  EPIC3Marine Biology, SPRINGER, ISSN: 0025-3162
    Details
    Publication Date: 2019-07-17
    Description: It has been hypothesized that endolithic photo- autotrophs inside the skeleton of cold-water corals may have a mutualistic relationship with the coral host posi- tively affecting coral calcification. This study investigated the effect of endolithic photo-autotrophs on the apical septal extension of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile (42.41°–42.15°S, 72.5°W). The fluorescent staining agent calcein was used to document the linear apical extension of septae for a period of one and a half years between 2006 and 2007. The results showed a severe reduction in extension rates asso- ciated with the presence of endolithic photo-autotrophs. Infested individuals grew about half as fast as non-infested polyps with a median value of 1.18 lm day-1 compared to 2.76 lm day-1. Contrary to the initial hypothesis, these results point toward a parasitic relationship between D. dianthus and its endolithic photo-autotrophs potentially impairing coral fitness. However, further data on physio- logical parameters and other aspects of the calcification process are necessary to confirm these findings.
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  • 222
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    EFFECTS OF OCEAN ACIDIFICATION ON THE ECO-PHYSIOLOGY OF CALCAREOUS AND TOXIC DINOFLAGELLATES (2013)
    In:  EPIC3Third International Symposium in the Ocean in a High-CO2 world, Monterey Bay, 2012-09
    Details
    Publication Date: 2019-07-16
    Description: The consequences of ocean acidification (OA) on marine phytoplankton have been intensively studied ranging from cellular to ecosystem level. These investigations, however, almost exclusively focused on coccolithophores and diatoms. Dinoflagellates also represent an important group of phytoplankton, featuring the photosynthetic key enzyme type II RubisCO, with very low affinities for its substrate CO2. Hence, we expect this group to be particularly sensitive to changes in CO2 concentrations. In this study, we therefore investigated the impact of OA on the eco-physiology of two dinoflagellate species, the calcareous Scrippsiella trochoidea and the toxic Alexandrium tamarense, by using dilute batch incubations over a range of CO2 levels. Our results show that with rising pCO2, growth rates and chlorophyll a contents remained relatively unaltered, but also species-specific differences were observed. For instance, Scrippsiella displayed a strong decrease in organic carbon production, and Alexandrium showed a shift in its toxin profile towards less toxic variants under elevated CO2. To understand these eco-physiological responses, several aspects of inorganic carbon (Ci) acquisition were investigated by means of membrane-inlet mass spectrometry. Both species featured efficient carbon concentrating mechanisms (CCMs), which in Scrippsiella was further facilitated by a high carbonic anhydrase activity. In Scrippsiella, maximum photosynthetic rates increased while Ci affinities decreased. Interestingly, in Alexandrium the opposite response pattern was observed. Our results show that dinoflagellate species have different strategies to adjust their Ci acquisition, which may enable them to keep their growth rates unaffected over a range of CO2 levels.
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    Potential of dual-pol TerraSAR-X data for Land Cover Classification in Arctic Tundra Landscapes (2013)
    ESA
    In:  EPIC3ESA Living Planet Symposium, Edinburgh, UK, 2013-09-09-2013-09-13Edinburgh, UK, ESA
    Details
    Publication Date: 2015-07-13
    Description: Arctic land covers play a critical role in linking the land, atmosphere, and oceans of the Arctic System as a whole, and in determining the role terrestrial ecosystems play in feedbacks to climatic change. Point measurements of ground and soil temperatures, as well as energy fluxes or associated surface parameters like land cover, however, cannot adequately represent the spatial heterogeneity and complexity of Arctic environments. Remote sensing on the other hand, provides a means of obtaining continuous and regional information of high Arctic environments where existing data networks are sparse. This study focuses on Arctic river deltas, namely the Lena Delta in northern Siberia and the Mackenzie Delta in Canada. Both areas are underlain by continuous permafrost. The surface is characterized by polygonal structures, thermo-erosion valleys, shallow lakes, and river channels. The vegetation cover is mainly composed of mosses, herbs, sedges, and shrubs. The surface is generally moist or wet, as the permafrost table acts as boundary for water drainage and evapotranspiration is low. Both deltas can be subdivided into unique geomorphologic units, which show differences in the soil texture, surface wetness and vegetation composition. In the Mackenzie Delta, recent tundra fires have also impacted the vegetation cover. Extensive ground truth data are available for both sites from field campaigns, automatic weather stations, and optical imagery. SAR intensity images alone are often insufficient for accurate classification of these environments, thus it is advantageous to include additional phase-related information. A high spatial resolution is essential to clearly distinguish land and water surfaces. The German X-band radar satellite TerraSAR-X can acquire dual polarized images, which enables the derivation of polarimetric features, including correlation coefficients, phase differences, polarization ratios, Kennaugh and dual-pol entropy / alpha decompositions and others. The goal of this study is to identify suitable SAR features for the characterization of Arctic tundra land covers. Images were acquired during summer in stripmap mode, and after georeferencing and multilooking a pixel size of 12 meters was achieved. Backscattering intensities as well as scattering mechanism information were taken into account. The best feature combinations from the decompositions were then used as input for the land cover classification. Different processing methods and classification algorithms, both supervised and unsupervised, were tested with respect to the best classification results. The Transformed Divergence was also calculated to investigate class separability. First analyses showed for example, that double-bounce is the dominant scattering mechanism in wetlands, whereas odd-bounce is characteristic for unvegetated sandbanks. Thus these landscape covers can be distinguished, despite having similar backscattering intensities. Unsupervised classification methods have shown little potential to distinguish between the landscape units, whereas the supervised Maximum Likelihood classification has achieved acceptable accuracies. The application of morphological filters on the classification results have also been shown to reduce the number of miss-classifications.
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    Climate change and the oceans - What does the future hold? (2013)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Marine Pollution Bulletin, PERGAMON-ELSEVIER SCIENCE LTD, 74, pp. 495-505, ISSN: 0025-326X
    Details
    Publication Date: 2019-07-16
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    Bremerhaven Declaration on the Future of Fish Nutrition and Aquaculture Technology – Part I: Preamble and Recommendations (2013)
    BIS
    In:  EPIC3Bremerhaven Declaration, BIS, 4 p.
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Correction to “Changes in Arctic sea ice result in increasing light transmittance and absorption” (2013)
    AMER GEOPHYSICAL UNION
    In:  EPIC3Geophysical Research Letters, AMER GEOPHYSICAL UNION, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-17
    Description: In the paper “Changes in Arctic sea ice result in increasing light transmittance and absorption” by Nicolaus et al. (Geophysical Research Letters, 39(24), L24501, doi:10.1029/2012GL053738, 2012), the presented data on solar surface irradiance are erroneous. In order to generate monthly means of the solar heat input into the Arctic Ocean, among others, the ERA interim (European Centre for Medium-Range Weather Forecasts) data set of solar surface irradiance was used. The original data set consists of eight time slices with integrated fluxes over 3 h each. But in the presented results, only the mean (not sum) of two slices (from 00:00 to 03:00 and from 12:00 to 15:00) was considered, resulting in too low fluxes, approx. by a factor of eight. As a consequence, two text passages (in paragraph 3.1 and 3.3) and three figures (Figure 4 of the main article and Figures S3 and S6 of the auxiliary material) contain too low fluxes. However, the main conclusions of the manuscript remain completely valid and unchanged, since those are only based on relative fluxes, which are not affected by this mistake.
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    Review of the «Global and Russian energy outlook up to 2040 (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Dielectric properties of snow and ice in the MHz-range (2013)
    In:  EPIC3ISEMA International conference on electromagnetic wave interaction with water and moist substances, Bauhaus University, Weimar, 2013-09-25-2013-09-27
    Details
    Publication Date: 2019-07-17
    Description: We present an overview of current state-of-the art measurements and knowledge of dielectric properties of ice and snow. They are the fundamental property for electromagnetic applications in cryospheric sciences, like ground-penetrating radar (GPR) and satellite remote sensing. Relevance ranges from improved determination of snow-cover properties for improved avalanche risk estimation to reconstruction of past climate signals from ice cores to improved understanding of dynamics of ice masses like Greenland and Antarctica. Our results are based on several techniques: (i) laboratory observations with a coaxial cell (CC) set-up, employed to measure dielectric properties on artificial and natural snow and ice samples in the range from 1 MHz to 1.5 GHz; (ii) dielectric profiling (DEP) of firn and ice cores in the range of 100 kHz; and (iii) usage of GPR to indirectly deduce the dielectric properties of the bulk medium via variations in wave speed and reflection coefficients. In contrast to many other substances, H2O as the underlying molecule, exists close to its melting point under ordinary conditions, involving snow and ice on Earth. This is of large interest for environmental applications as the so-called snow-water equivalent (i.e. the total mass) can greatly vary depending on density and liquid-water saturation of a snow cover, without showing considerable changes in snow height. In contrast, it poses a major problem for determining dielectric properties close to the melting point, especially in the laboratory, as the medium of interest partly undergoes a phase transition while varying temperature. In addition, especially for applications on glaciers and ice sheets, the anisotropic nature of ice has to be taken into account, as ice viscosity - and thus flow behavior - varies over four orders of magnitude depending on the crystal orientation fabric.
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    Comparative genomics: Linking population structure, transcriptomic responsiveness and species vulnerability to abiotic factors: concepts, state of project and first results (BIOACID subproject 4.3.) (2013)
    In:  EPIC3BIOACID Phase II, annual meeting, Leibniz-Institut für Ostseeforschung Warnemünde (IOW), 2013-10-01-2013-10-02
    Details
    Publication Date: 2014-06-11
    Description: Within consortium 4 of BIOACID II, we examine effects of ocean warming and acidification (OWA) on different cod species: Polar cod, Boreogadus saida, and Atlantic cod, Gadus morhua. Species distribution as well as population structure of both are reported to be already changing, mainly driven by warming of water masses in their natural habitats. Shifts of G. morhua into higher latitudes will increasingly interact/interfere with populations of B. saida in Arctic waters. However, it is unclear, by which dynamics and how fast the intersecting area of both species will alter during the next decades, which could even lead to extinction of the cold-adapted native species. Within this work package stock distribution patterns are monitored by means of population genetic analyses of hundreds of samples collected from the beginning in the early nineties of the last century until today to assess the current situation and to project future species occurrences. Complementary to these studies is the physiological characterization of each species by means of incubation experiments. These are used to qualify their robustness/vulnerability to future conditions in the northern oceans on multiple levels of organization, i.e. at whole animal down to the molecular level, studying energy budgets and metabolic regulation as well as effects of OWA on different life stages (work packages 4.1 – 4.7). At first, specimens of B. saida have been under study to evaluate critical levels of OWA. Animals caught this January in the Barents Sea north of Norway were brought to Bremerhaven and incubated for 3 months under different CO2 and temperature combinations. During the incubation period, growth data (WP 4.1) and behavioural patterns (WP 4.6) were collected. Furthermore, samples were taken to monitor the total energy budget (EB) (WP 4.1), cellular and mitochondrial energy budget (WP 4.2) as well as for molecular studies of marker metabolites (WP 4.6) and transcriptomic analyses (this work package, 4.3). In parallel, we set up the basis for comparative protein and DNA sequence analyses for both species by constructing normalized cDNA libraries, which were sequenced with Illumina MiSeq (paired end). In total, sequencing output consists of 3.8 and 2.5 Gbp for B. saida and G. morhua, respectively. Transcripts were assembled using Trinity providing approx. 16k protein sequences for each species with an intersecting sequence amount of 14,843 orthologs. The latter will be analyzed for differences in amino acid usage and codon usage by large-scale comparison. Our working hypothesis is that the different habitat conditions have left adaptational signatures in codon and amino acid usage, which reflect different plasticities for acclimation in both species at the molecular level. Moreover, we would expect the regulation of functional genes in the transcriptomes to be differing, due to different critical thresholds of environmental factors and due to the different evolutionary pressures on metabolic genes. Consensus sequences of both library assemblies are used to build a compact Gadus spec. microarray matching sequence identities of both species to equal amounts. This array will be used to monitor long-term effects of different treatments on the transcriptome of B. saida and will provide an application that will also be used for samples of the planned incubation of specimens of G. morhua in 2014. Together with the collected physiological parameters, population genetics and transcriptomic data will provide an integrated picture of species fitness, critical thresholds of environmental conditions as well as consequences of synergistic effects caused by elevated temperature and high CO2 concentrations.
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    The complete mitochondrial genome of the stonefly Dinocras cephalotes (Plecoptera, Perlidae) (2013)
    INFORMA HEALTHCARE
    In:  EPIC3Mitochondrial DNA, INFORMA HEALTHCARE, pp. 1-2, ISSN: 1940-1736
    Details
    Publication Date: 2019-07-16
    Description: The complete mitochondrial genome of the perlid stonefly Dinocras cephalotes (Curtis, 1827) was sequenced using a combined 454 and Sanger sequencing approach using the known sequence of Pteronarcys princeps Banks, 1907 (Pteronarcyidae), to identify homologous 454 reads. The genome is 15,666 bp in length and includes 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and a control region. Gene order resembles that of basal arthropods. The base composition of the genome is A (33.5%), T (29.0%), C (24.4%) and G (13.1%). This is the second published mitogenome for the order Plecoptera and will be useful in future phylogenetic analysis.
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    Marine ice sheets of Pleistocene age on the East Siberian Continental Margin (2013)
    American Geophysical Union
    In:  EPIC3AGU Fall Meeting, 2013-12-08-2013-12-13American Geophysical Union
    Details
    Publication Date: 2016-02-02
    Description: Based on swath bathymetry, sediment echosounding, seismic profiling and sediment coring we present results of the RV „Polarstern“ cruise ARK-XIII/3 (2008) and RV "Araon" cruise ARA02B (2012), which investigated an area between the Chukchi Borderland and the East Siberian Sea between 165°W and 170°E. At the southern end of the Mendeleev Ridge, close to the Chukchi and East Siberian shelves, evidence is found for the existence of Pleistocene ice sheets/ice shelves, which have grounded several times in up to 1200 m present water depth. We found mega-scale glacial lineations associated with deposition of glaciogenic wedges and debris-flow deposits indicative of sub-glacial erosion and deposition close to the former grounding lines. Glacially lineated areas are associated with large-scale erosion, accentuated by a conspicuous truncation of pre-glacial strata typically capped with mostly thin layers of diamicton draped by pelagic sediments. Our tentative age model suggests that the youngest and shallowest grounding event of an ice sheet should be within Marine Isotope Stage (MIS) 3. The oldest and deepest event predates MIS 6. According to our results, ice sheets of more than one km in thickness continued onto, and likely centered over, the East Siberian Shelf. They were possibly linked to previously suggested ice sheets on the Chukchi Borderland and the New Siberian Islands. We propose that the ice sheets extended northward as thick ice shelves, which grounded on the Mendeleev Ridge to an area up to 78°N within MIS 5 and/or earlier. These results have important implication for the former distribution of thick ice masses in the Arctic Ocean during the Pleistocene. They are relevant for global sea-level variations, albedo, ocean-atmosphere heat exchange, freshwater export from the Arctic Ocean at glacial terminations and the formation of submarine permafrost. The existence of km-thick Pleistocene ice sheets in the western Arctic Ocean during glacial times predating that of the Last Glacial Maximum (LGM) also implies significantly different atmospheric circulation patterns, in particular availability and distribution of moisture during pre-LGM glaciations.
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    Steps to the parametrization of the transfer coefficients over sea ice for the MiKlip model system (DS2) (2013)
    In:  EPIC3MiKlip Module B meeting, Bonn, Collegium Leoninum, 2013-09-17-2013-09-18
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    Publication Date: 2017-10-20
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    Dynamics of seagrasses in a heterogeneous tropical reef ecosystem (2013)
    In:  EPIC3158 p.
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Fluid-induzierte seismische Dämpfung in marinen Sedimenten vom Ultraschall bis zum seismischen Frequenzbereich - Beispiele aus der marinen Sedimentphysik, Sedimentechographie und Reflexionsseismik (2013)
    In:  EPIC3Oral Presentation, Federal Institute for Geosciences and Resources (BGR), Hannover, Germany, 2013-10-02-2013-10-02Federal Institute for Geosciences and Resources (BGR), Hannover, Germany
    Details
    Publication Date: 2019-07-17
    Description: not available
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    Sedimentary sequences in the Amundsen Sea, Southern Pacific: Hinterland glaciation already during the Early Miocene? (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, USA, 2013-12-09-2013-12-13
    Details
    Publication Date: 2019-07-16
    Description: The distribution and internal architecture of seismostratigraphic sequences observed on the Antarctic continental slope and rise are results of sediment transport and deposition by bottom currents and ice sheets. Analysis of seismic reflection data allows to reconstruct sediment input and transport patterns and to infer past changes in climate and oceanography. We observe four seismostratigraphic units which show distinct differences in location and shape of their depocentres. We used an age-depth model based on DSDP Leg 35 Site 324 for the Plio/Pleistocene and a correlation with seismic reflection characteristics from the Ross and Bellingshausen Seas, which unfortunately has large uncertainties. For the period before 21 Ma, we interpret low energy input of detritus via a river estuary originating in an area of the Amundsen Sea shelf, where a palaeo-ice stream trough (Pine Island Trough East PITE) is located today, and deposition of this material on the continental rise under sea ice coverage. For 21-14.1 Ma we postulate intense glacial erosion for the hinterland of this part of West Antarctica, which resulted in a larger depocentre and an increase in mass transport deposits. Warming during the Mid Miocene Climatic Optimum led to a wet-based ice sheet and a higher sediment supply along a broad front but with a focus via two palaeo-ice stream troughs. Most of the glaciogenic debris was transported onto the eastern Amundsen Sea rise where it was shaped into levee-drifts by a re-circulating bottom current. A reduced sediment accumulation in the deep-sea subsequent to the onset of climatic cooling after 14 Ma indicates a reduced sediment supply probably in response to a colder and drier ice sheet. A dynamic ice sheet since 4 Ma delivered material offshore mainly via AT and Pine Island Trough West. Interaction of this glaciogenic detritus with a west-setting bottom current resulted in the continued formation of levee-drifts in the eastern and central Amundsen Sea.
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    Batiacasphaera micropapillata: Palaeobiogeographic distribution and palaeoecological implications of a critical Neogene species complex. (2013)
    The Geological Society
    In:  EPIC3Biological and Geological Perspectives of Dinoflagellates., The Micropaleontological Society, Special Publications No. 5, London, The Geological Society, pp. 293-306, ISBN: 978-1-86239-368-4
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    Publication Date: 2014-04-15
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    Von der Flözwellenseismik zum marinen Umweltschutz - Beispiele zur Modellierung der elastischen Wellenausbreitung und Analyse der seismischen Dämpfung aus interdisziplinären Forschungsarbeiten 1984 - 2013 (2013)
    In:  EPIC3Oral Presentation, Federal Institute for Geosciences and Resources (BGR), Hannover, Germany, 2013-09-30-2013-09-30Federal Institute for Geosciences and Resources (BGR), Hannover, Germany
    Details
    Publication Date: 2019-07-17
    Description: not available
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    Genetic and Morphological Divergences in the Cosmopolitan Deep-Sea Amphipod Eurythenes gryllus Reveal a Diverse Abyss and a Bipolar Species (2013)
    In:  EPIC3PLoS ONE, 8(9), pp. e74218, ISSN: 1932-6203
    Details
    Publication Date: 2019-07-17
    Description: Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species’ origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the ‘true’ E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism.
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    Comparison of two new species of Mastogloia (Bacillariophyceae) with other small members of section Ellipticae (2013)
    In:  EPIC3Phytotaxa, 126(1), pp. 1, ISSN: 1179-3155
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    Publication Date: 2019-07-17
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    Global and regional sea surface temperature trends during Marine Isotope Stage 11 (2013)
    In:  EPIC3Climate of the Past, 9(5), pp. 2231-2252, ISSN: 1814-9332
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    Publication Date: 2019-07-17
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    The penetrative mixing in the Laptev Sea coastal polynya pycnocline layer (2013)
    In:  EPIC3Continental Shelf Research, 63, pp. 34-42
    Details
    Publication Date: 2019-07-17
    Description: The large recurrent areas of open water and/or thin ice (polynyas) producing cold brine-enriched waters off the fast-ice edge are evident in the Laptev Sea in winter time. A number of abrupt positively correlated transitions in temperature and salinity were recorded in the bottom and intermediate layers at a mooring station in the West New Siberian (WNS) polynya in February-March 2008. Being in the range of ~0.5. °C and ~1.6. psu these changes are induced by horizontal motions across the polynya and correspond to temperature and salinity horizontal gradients in the range of 0.3-1.0. °C/10. km and 1.4-3.5. psu/10. km, respectively. The events of distinct freshening and temperature decrease coincide with a northward current off the fast-ice edge, while southward currents brought saltier and warmer waters at intermediate depths. We suggest that the observed transitions are connected to altering pycnocline depths across the polynya. The source of relatively fresher waters at the intermediate depths in polynya is supposed to originate from penetrative mixing of surface low salinity waters to intermediate water depth. Several forcing processes that could be responsible for a penetrative mixing through the density interface in polynya are discussed. These are penetrative convection and shear-driven mixing that originates from two-layer water dynamics and/or baroclinic tidal motions. The heavily ridged seaward fast-ice edge could produce an additional source of turbulent mixing even through a shear-free density interface due to the increased roughness at the ice-water interface.
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    Correlation of river water and local sea-ice melting on the Laptev Sea shelf (Siberian Arctic) (2013)
    In:  EPIC3Journal of Geophysical Research C: Oceans, 118(1), pp. 550-561
    Details
    Publication Date: 2019-07-17
    Description: Hydrographic and stable isotope (δ18 O) data from four summer surveys in the Laptev Sea are used to derive fractions of sea-ice meltwater and river water. Sea-ice meltwater fractions are found to be correlated to river water fractions. While initial heat of river discharge is too small to melt the observed 0-158 km3 of sea-ice meltwater, arctic rivers contain suspended particles and colored dissolved organic material that preferentially absorb solar radiation. Accordingly, heat content in surface waters is correlated to river water fractions. But in years when river water is largely absent within the surface layer, absolute heat content values increase to considerably higher values with extended exposure time to solar radiation and sensible heat. Nevertheless, no net sea-ice melting is observed on the shelf in years when river water is largely absent within the surface layer. The total freshwater volume of the central-eastern Laptev Sea (72-76°N, 122-140°E) varies between ∼1000 and 1500 km3 (34.92 reference salinity). It is dominated by varying river water volumes (∼1300-1800 km3) reduced by an about constant freshwater deficit (∼350-400 km3) related to sea-ice formation. Net sea-ice melt (∼109-158 km3) is only present in years with high river water budgets. Intermediate to bottom layer (〉25 salinities) contain ∼60% and 30% of the river budget in years with low and high river budgets, respectively. The average mean residence time of shelf waters was ∼2-3 years during 2007-2009. © 2013. American Geophysical Union. All Rights Reserved.
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    Optimierung eines neuartigen in situ Massenspektrometers zur Analyse von Spurengasen wie Methan in aquatischen Systemen. (2013)
    In:  EPIC3142 p.
    Details
    Publication Date: 2019-07-17
    Description: Die vorliegende Arbeit wurde am Alfred Wegener Institut für Meeres- und Polarforschung in Bremerhaven durchgeführt. Ende 2005 hat das Alfred Wegener Institut Sektion Geochemie ein in situ Massenspektrometer (Inspectr200-200) der Firma AML erworben. Dieses ist in der Lage viele in der Meeresforschung relevanten Spurengase in kürzester Zeit simultan, kontinuierlich und direkt im Probenmedium zu detektieren. Es zählt zu der Baugruppe der „harsh environment“-Analysengeräte. Aufgrund der möglichen Simultanmessung vieler Spurengase bietet das Gerät einen Erhalt hoher Datenmengen in sehr kurzer Zeit. Damit könnte eine intensivere Beprobung der zu untersuchenden Gebiete im Vergleich zur heutigen Analysentechnik ermöglicht werden. Der analytische Teil dieser Arbeit bestand in der Messoptimierung des Inspectr200-200 sowie der Kalibration ausgewählter Spurengase. Nach Inbetriebnahme des in situ Massenspektrometers wurde dieses mit den gegebenen Möglichkeiten auf Methan eingestellt. Anschließend wurde die Fragestellung der Kalibrierung der einzelnen Gase bearbeitet. Es war nicht möglich fertige Standardlösungen zu kaufen. Daher wurden diese selbst hergestellt. Es wurden die im Wasser real gelösten Gasmengen mit anderen Messmethoden bestimmt und als Standard für Kalibrationen eingesetzt. Ein weiterer Teil der Arbeit umfasst die Etablierung eines Sicherheitssystems. Das Probeneinlasssystem stellt bei diesem Gerät eine gasdurchlässige Membran aus PDMS dar. Sollte diese ausfallen bzw. reißen, würde das gesamte System, bedingt durch den vorherrschenden Druckunterschied, bei laufendem Betrieb mit Seewasser gefüllt werden. Dies hätte den Ausfall sämtlicher Gerätebauteile und Korrosionserscheinungen zur Folge. Auf Expeditionen würde das Gerät aufgrund der aufwendigen Reinigung mehrere Tage ausfallen und teure Messzeit könnte nicht genutzt werden. Um dieses zu verhindern, gab es mehrere Lösungsvorschläge, bei dem zwei intensiver betrachtet wurden. Hierbei handelt es sich um den Vorbau einer weiteren Membran, sowie den Einbau einer Kühlfalle zur Absicherung der Analyseneinheit. Nach erfolgreicher Lösung der Fragestellungen der Kalibration wurden erste Feldmessungen durchgeführt. In der Ostsee wurde das Gerät für 2 Tiefenprofilmessungen sowie eine Transektmessung eingesetzt. Methan konnte bei dieser Ausfahrt nicht detektiert werden. Es konnten bei den Messungen jedoch signifikante Veränderungen der Sauerstoff- und Kohlendioxid-Signale festgestellt werden. Aus diesem Grunde wurde in dieser Diplomarbeit versucht, neben Methan auch diese Gase zu kalibrieren. Nach Einbau einer bereits optimierten Kühlfalle wurden Feldmessungen im Bodensee durchgeführt. Bei den Messungen konnte Methan detektiert und quantifiziert werden. Anhand der ermittelten Daten kann davon ausgegangen werden, dass Methan aus dem Bodensee in die Atmosphäre abgegeben wird.
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    Study of Local Seismic Events in Lithuania and Adjacent Areas Using Data from the PASSEQ Experiment (2013)
    SP Birkhäuser Verlag Basel
    In:  EPIC3Pure and Applied Geophysics, SP Birkhäuser Verlag Basel, 170(5), pp. 797-814, ISSN: 1420-9136
    Details
    Publication Date: 2019-07-17
    Description: The territory of Lithuania and adjacent areas of the East European Craton have always been considered a region of low seismicity. Two recent earthquakes with magnitudes of more than 5 in the Kaliningrad District (Russian Federation) on 21 September 2004 motivated re-evaluation of the seismic hazard in Lithuania and adjacent territories. A new opportunity to study seismicity in the region is provided by the PASSEQ (Pasive Seismic Experiment) project that aimed to study the lithosphere–asthenosphere structure around the Trans-European Suture Zone. Twenty-six seismic stations of the PASSEQ temporary seismic array were installed in the territory of Lithuania. The stations recorded a number of local and regional seismic events originating from Lithuania and adjacent areas. This data can be used to answer the question of whether there exist seismically active tectonic zones in Lithuania that could be potentially hazardous for critical industrial facilities. Therefore, the aim of this paper is to find any natural tectonic seismic events in Lithuania and to obtain more general view of seismicity in the region. In order to do this, we make a manual review of the continuous data recorded by the PASSEQ seismic stations in Lithuania. From the good quality data, we select and relocate 45 local seismic events using the well-known LocSAT and VELEST location algortithms. In order to discriminate between possible natural events, underwater explosions and on-shore blasts, we analyse spatial distribution of epicenters and temporal distribution of origin times and perform both visual analysis of waveforms and spectral analysis of recordings. We show that the relocated seismic events can be grouped into five clusters (groups) according to their epicenter coordinates and origin and that several seismic events might be of tectonic origin. We also show that several events from the off-shore region in the Baltic Sea (at the coasts of the Kaliningrad District of the Russian Federation) are non-volcanic tremors, although the origin of these tremor-type events is not clear.
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    Reconstructing past sea ice (2013)
    In:  EPIC3EOS Transactions, American Geophysical Union, 94(42), pp. 376
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    Publication Date: 2019-07-17
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    FT-IR analysis for monitoring marine microplastics (2013)
    In:  EPIC3YOUMARES 4, Oldenburg, 2013-09-11-2013-09-13
    Details
    Publication Date: 2019-07-16
    Description: Persistent plastics are hardly degraded and accumulate in the marine environment. Their fragmentation leads to an increasing amount of small plastic particles, so-called microplastics. Due to their size, these have the potential of entering marine food webs. For a reliable evaluation and an assessment of food web effects, a detailed quantitative and qualitative monitoring of microplastics in the marine environment is highly required and thus stipulated within the framework of the Marine Strategy Framework Directive (MSFD). Due to the sampling procedures and the sample analyses currently used, the scarce data on microplastics concentrations are mostly biased towards larger particles. Therefore, reliable data on concentrations of the total size spectrum of microplastics in marine systems and especially in German coastal waters are still lacking. Furthermore, the polymer origin of potential microplastic particles needs to be verified during analysis. Fourier Transform infrared (FT-IR) spectroscopy offers the possibility of proper identification of plastic particles in environmental samples. However, standard FT-IR spectroscopy still requires time- and labour-consuming pre-sorting of particles by hand. Hence, small or less abundant microplastics are potentially overlooked. A highly promising FT-IR extension (FT-IR Imaging) allows for detailed and unbiased high throughput analysis of total microplastics in a given sample without prior pre-sorting by hand. Thus the project MICROPLAST aims on (1) the development/optimisation of appropriate methods for the extraction of microplastic particles from complex matrices (e.g. sediment, plankton, tissue), (2) the evaluation of FT-IR imaging for the analysis of microplastics and the development of procedures for its routine application, (3) the first-time production of valid data on the pollution of the pelagic and benthic zone with microplastic particles in German coastal waters.
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    Thick-shelled, grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current (2013)
    NATL ACAD SCIENCES
    In:  EPIC3Proceedings of the National Academy of Sciences of the United States of America, NATL ACAD SCIENCES, ISSN: 0027-8424
    Details
    Publication Date: 2017-10-04
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    Deep fossil carbon - spatial and temporal variability of organic matter pools in permafrost (2013)
    In:  EPIC3International Conference "Earth Cryology: XXI Century", Pushchino, Russia, 2013-09-29-2013-10-03
    Details
    Publication Date: 2019-07-17
    Description: The estimation of the carbon pool stored in arctic permafrost and its biogeochemical characteristics are essential topics in today’s permafrost research. While the uppermost cryosoil horizons are well-studied and already recorded in the Northern Circumpolar Soil Carbon Database (NCSCD) there are still large uncertainties concerning the quality and distribution of deep (i.e. up to decameters) organic carbon stocks. Well-exposed permafrost sections along the arctic sea coast and river banks in northern Yakutia are excellent objects to study permafrost organic carbon characteristics in connection with cryolithogy, cryostratigraphy and past periglacial landscape dynamics. Organic carbon occurs in permafrost as large tree trunks, peat inclusions, twigs and root fragments, other solid plant remains, and finely distributed plant detritus, but also as fossil mammal remains, insects, aquatic zooplankton and -benthos, and soil microorganisms, and finally its decomposition and metabolic products in terms of particulate and dissolved organic matter. These different kinds of fossil organic matter were formed, deposited, frozen, thawed and partly degraded, and sometimes refrozen, under different paleoclimatic and paleogeographical conditions of the Quaternary past. Therefore, the deep permafrost organic carbon pool is far from homogeneous and strongly linked to depositional and permafrost dynamics as well as the ecological and climatic history. The archive of specific biogeochemical and cryolithological features of frozen ground is recorded in permafrost sequences of about the last 200.000 years in northern Yakutia. We present the variabilites of the spatial distribution of organic carbon and organic matter qualities between different stratigraphical units, between correlated stratigraphical units of several sites, and even within stratigraphic units at the same site. Especially the coverage and composition of the widely distributed late Pleistocene Yedoma horizons and its thermokarst-affected derivatives in alas depressions are of interest to climate modeling, microbiology or biochemistry. There are significant differences to former estimates of the area, thickness of the relevant frozen deposits, ground ice content and finally in organic carbon content that lead to a reassessment of the deep permafrost carbon pools of the northern high latitude Yedoma region.
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    Monitoring und Bewertung des Benthos, der Lebensraumtypen / Biotope und der Gebietsfremden Arten (2013)
    In:  EPIC3BfN
    Details
    Publication Date: 2014-05-19
    Repository Name: EPIC Alfred Wegener Institut
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    Structure and function of microorganisms in the methanic zone of the Helgoland mud area, North Sea (2013)
    In:  EPIC3Konferenz der Vereinigung für Allgemeine und Angewandte Mikrobiologie (VAAM), Bremen, 2013-03-10-2013-03-13
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    Publication Date: 2014-05-16
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    Ice growth in the presence of an antifreeze protein (2013)
    In:  EPIC3Annual Meeting of the Society for Cryobiology, Bethesda, Maryland (USA), 2013-07-28-2013-07-31
    Details
    Publication Date: 2014-08-04
    Description: Antifreeze proteins (AFPs) have evolved in cold-adapted organisms to control ice crystal growth when exposed to sub-zero temperature conditions. It has been suggested that the effect of the proteins results in small ice crystal size, thus avoiding in frozen tissues and cells the damage mechanically caused by large ice grains. Also the polar diatom Fragilariopsis cylindrus, a dominant species within sea-ice assemblages, produces AFPs. We expressed in E. coli a recombinant form of this protein and isolated it by affinity chromatography. We studied its effect on ice grain size after shock-freezing and subsequent annealing, and under slow freezing conditions. Shock-freezing (−40°C) produced small sized crystals, and during annealing at −4°C AFPs successfully inhibited recrystallization already at low concentrations (1.2 μM), as observed at light microscopy and using the Otago optical recrystallometer. However, slow ice growth at −5°C, more likely to resemble natural freezing conditions, surprisingly resulted in the formation of larger crystals in the presence of AFPs than in the negative controls. Further characteristic microstructural features, like among others gradual c-axis transition within individual grains and sublimation etching patterns, were observed under crossed polarizers and at light microscopy. These features are possibly due to the incorporation of proteins into the ice lattice during growth, causing local defects. Our observations remain to be clarified, but should be taken into account when considering the biological role of AFPs as well as potential industrial applications of the proteins.
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    Modellierung des Ensembleverhaltens von sedimentierenden Hydrometeoren mittels Momentenverfahren (2013)
    Staats- und Universitätsbibliothek Bremen
    In:  EPIC3Staats- und Universitätsbibliothek Bremen, 169 p.
    Details
    Publication Date: 2015-07-07
    Description: For the treament of clouds and precipitation in weatherforecast or climate models, a direct spectral representation of the microphysical processes is computationally infeasible. Therefore, their effects have to be considered in an approximative, parameterised way. It is then possible that the model results are not sensible in a cloud microphysics context. In order to avoid this, in this dissertation a new parameterisation of sedimentation (two moment method) is developed and tested in a 1D model. The parameterisation is based on a hydrometeor distribution with bounded domain and is implemented in two ways: 1) truncated Gamma-distribution: compared to already existing parameterisations, the model results are considerably improved (for drops as well as for ice crystals). Investigations include the computation time, the sensitivity of the results on the upper hydrometeor size limit and an optimisation concerning this limit. The development of a rain cloud is simulated by adding drop collisions to the test case. 2) Beta-distribution: It contains an additional free parameter. Its diagnostic relationship has a strong impact on the results.
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    Influence of anisotropy on seismic data, Colle Gnifetti, Switzerland (2013)
    Geophysical Research Abstracts Vol. 15, EGU2013-309
    In:  EPIC3EGU General Assembly, Vienna, 2013-04-07-2013-04-12Geophysical Research Abstracts Vol. 15, EGU2013-309
    Details
    Publication Date: 2019-07-17
    Description: A possibility to detect anisotropy in ice sheets and glaciers is by analyzing seismic data. Two effects are impotant: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and thus also traveltimes. In 2010 a seismic survey using a micro-vibrator source (ElViS) was carried out in compression (P)- and shear (SH)-wave mode at Colle Gniefetti, Switzerland. In both cases reflections could be observed in the firn and ice column. We use eigenvalue COF data from a nearby ice-core to derive elasticity tensors and thus have the possibility to model traveltimes and reflection coefficients of seismic P- and SH-wave data. By comparison of the modeled with the measured data we are able to connect some of the observed reflections to changes in crystal orientation fabric. Further a discrepancy occurred for the depth of the bed reflection between the P-, SH-wave and ice-core data. While the depth of the SH-wave bed reflection fitted quite well to the ice-core depth, the P-wave bed reflection was to shallow after depth conversion.We are able to explain these differences with the conceptual errors introduced by assuming isotropic media and thus using velocities traditionally derived from stacking (normal moveout (NMO)- velocity), with an offset-to-depth ratio of one, for the depth conversion. The NMO-velocity includes the lateral velocity variations and can differ from the vertical root-mean-square (RMS) velocity for P-waves by up to 20%, for SH-waves only by up to 7% in case of single maximum fabric. Modeling velocities at Colle Gnifetti based on the ice-core COF can quite well explain the largest part of the introduced depth difference for the P-wave, while it also shows that the existing anisotropies only introduce a difference between NMO- and vertical RMS-velocity of 1% for the SH-wave. Our data show that it is highly important to include anisotropy into the depth conversion of seismic data on glaciers and ice sheets, especially the error in depth conversion of the P-waves becomes considerable otherwise. This implies that we are able to derive information about anisotropies from the depth difference of seismic P-wave data when the correct depth is known from other data sources like boreholes or radar data.
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    Late Quaternary Paleoclimate Information from Stable Water Isotopes in Ice Wedges at the Dmitry Laptev Strait, Northeast Siberian Arctic (2013)
    In:  EPIC325th International Symposium on Polar Research, Hamburg, Germany, 2013-03-17-2013-03-22
    Details
    Publication Date: 2019-07-17
    Description: Ice wedges are the most abundant type of ground ice in the ice-rich permafrost deposits of the Northeast Siberian Arctic. They are formed by the periodic repetition of frost cracking and subsequent crack filling in spring, mostly by melt water of winter snow. Ices wedges can be studied by means of stable-water isotopes. Their isotopic composition is directly linked to atmospheric precipitation (i.e. winter snow) and, therefore, indicative of past winter climate conditions even though also genetic aspects, i.e. sublimation, melting and refreezing in the snowpack and the frost crack, have to be taken into account. Here we present stable-water isotope data of ice wedges at the Oyogos Yar coast of the Dmitry Laptev Strait (72.7°N, 143.5°E). The ice wedges from different stratigraphic units comprising pre-Eemian sediments, Middle Weichselian Ice Complex (Yedoma) sediments and Holocene themokarst (Alas) sediments were studied and sampled in 2002 and 2007. Stable-water isotopes were measured in the stable-isotope lab of the Alfred Wegener Institute in Potsdam, Germany. Ice wedge stable-water isotope data indicate substantial variations in Northeast Siberian Arctic winter climate conditions (δ18O) as well as shifts in the moisture generation and transport patterns (d excess) during the Late Quaternary, in particular between Glacial and Interglacial but also during the last centuries. Ice wedges of the pre-Eemian Kuchchugui and Bychchaguy Suites exhibit mean δ18O values of about -30‰ and -34‰, respectively, indicating cold to extreme cold winter temperatures. The latter represents the coldest conditions found in ice wedges at the Oyogos Yar coast. Mean d-excess values are about 3‰ and 6‰, respectively. Small ice wedges in Eemian sediments show distinctly warmer mean δ18O values of about -24‰ and mean d-excess values of about 4‰. However, probably they represent younger epigenetically grown ice wedges with an isotopic composition that might be influenced by sediment-ice interaction. Huge syngenetic ice wedges of the Weichselian Yedoma Suite are characterized by mean δ18O values of -29‰ to -33‰ and mean d-excess values around 6‰ in different altitude levels, reflecting cold to extreme cold winter temperatures. On top of the Ice Complex as well as in a thermokarst depression, formed during the Late Glacial, Holocene ice wedges could be found. They have been grown predominantly in the Middle and Late Holocene and exhibit mean δ18O values of about -25‰ and mean d-excess values of 8‰, mirroring distinctly warmer winter temperatures in the Holocene. Recent ice wedges grown in the last decades are characterized by mean δ18O values of about -22‰ and mean-d excess values of 8‰, testifying the recent winter warming in the Arctic.
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    Wellen, Vermischung und die ozeanische Zirkulation (2013)
    In:  EPIC3Festkolloquium zu Ehren von Wolfgang Fennel, IOW Warnemünde, 2013-03-27
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    Publication Date: 2019-07-16
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    TCCON http://www.tccon.caltech.edu test data file (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Estimating the hydrogen isotopic composition of past precipitation using leaf-waxes from western Africa (2013)
    Elsevier
    In:  EPIC3Quaternary Science Reviews, Elsevier, 65, pp. 88-101, ISSN: 02773791
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    Publication Date: 2019-07-17
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    Frequency power analyses of seismic sources on firn (2013)
    Geophysical Research Abstracts Vol. 15, EGU2013-8035-1
    In:  EPIC3EGU General Assembly, Vienna, 2013-04-07-2013-04-12Geophysical Research Abstracts Vol. 15, EGU2013-8035-1
    Details
    Publication Date: 2019-07-17
    Description: A great obstacle for seismic surveys on firn-covered ice masses is the ability of firn to strongly attenuate seismic energy and divert downward ray paths away from the vertical because of the velocity gradient. The standard way to overcome these limitations is the drilling of shotholes about 10-30 m deep. However, drilling of shotholes is a time and energy consuming task. Another possibility is to use vibroseismic sources at the surface and increase the signal-to-noise ratio by repeated stacking. However, compared to explosive charges, vibroseismic signals are bandlimited per se. As a third variant, we investigate the usage of ordered patterns of surface charges consisting of detonation cord. Previous applications of detonation cord only explored their general comparison to bulk explosives when deployed in a linear fashion, i.e. a single line. Our approach extends these results to other geometries, like fan- or comb-shaped patterns. These have two advantages: first, over the pattern area a locally plane wave is generated, limiting the spherical and velocity-gradient induced spreading of energy during propagation; second, the ratio between seismic wave speed of the firn and the detonation cord of typically about 1:5 causes the wave to propagate in an angle downward. When using large offsets like a snow streamer, it is possible to direct the refected energy towards the streamer, depending on offset range and reflector depth. We compare the different source types for several surveys conducted in Antarctica in terms of frequency spectra. Our results show that ordered patterns of detonation cord serve as suitable seismic surface charges, avoiding the need to drill shotholes. Moreover, an example of a short profile with patterned surface charges is presented. The technique can be of advantage for surveys in remote areas, which can only be accessed by aircrafts.
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    R script (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Manihiki Plateau, southwestern Pacific: Archive of multi-phase magmatism, anoxic environment and modifications in ocean circulation and climate (2013)
    In:  EPIC3IODP Cretaceous Climate workshop, London, UK, 2013-04-15-2013-04-17
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    Publication Date: 2019-07-16
    Description: The Cretaceous was characterised by a dramatic increase in ocean crust production and abnormal intraplate volcanism. Many Large Igneous Provinces (LIPs) were formed during this period. The south western Pacific is dominated by three LIPs: the Ontong-Java Plateau (〉 1.5 106 km2), the Manihiki Plateau (~0.8 106 km2), and the Hikurangi Plateau (0.35 106 km2). The formation of LIPs in the equatorial western Pacific is still a matter of debate. For example, are they the product of a single “mega (Greater Ontong Java)” or of multiple, smaller volcanic events? Another important question is the time interval over which this volcanism took place: within a few million years or over tens of millions of years? This has implications for our understanding of mantle processes and climate variability. During the eruption of such huge amounts of magma large quantities of CO2 are emitted into the ocean-atmosphere system. LIPs are thus considered to have been responsible for global environmental modifications and ecosystem adaptations. We propose to drill on Manihiki Plateau to recover a complete sedimentary and the upper (1-2 km) basement volcanic rock sequences. The sediments preserved on this plateau record an 120 My-long history of extreme climates , global anoxia, perturbation of geochemical cycles and major changes in marine biota. The overall goal is a quantitative characterisation and understanding of biogeochemical cycles and marine ecosystem reactions to environmental and climate changes at the onset, during and after major greenhouse episodes. We want to determine the spatial and temporal variability of the lysocline carbonate compensation depth (CCD), oxygen minimum zone (OMZ), and primary productivity during the .Cretaceous. The proximity of Manihiki to Ontong Java Plateau and the Galapagos hotspots offers the opportunity to investigate reactions of the ocean/atmosphere system, as well as geochemical fluxes in an area close to emplacement of LIPs.
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    Modeling year-round marine mammal habitat preferences in the Southern Ocean based on passive acoustic observations (2013)
    In:  EPIC325. Internationale Polartagung "Polargebiete im Wandel", Hamburg, 2013-03-17-2013-03-22
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    Publication Date: 2019-07-17
    Description: An understanding of marine mammal distribution patterns forms the basis of the design and implementation of effective management measures. Habitat modeling offers a valuable approach to combine information on species presence (or absence) with local environmental parameters to explore species-specific habitat affinities. Most habitat modeling approaches require marine mammal presence-absence data which can only be obtained during dedicated visual surveys. However, in the Southern Ocean, the collection of visual data is complicated by the region’s remoteness, limited seasonal accessibility and the dependency on favorable light and weather conditions to conduct visual observations. Passive acoustic monitoring, by contrast, is highly suitable for long-term monitoring of marine mammals as they use sound in many behavioural contexts and species can be readily identified by their acoustic signatures. Passive acoustic data provide accurate information on temporal patterns in acoustic presence and time spent in the vicinity of the recorders. Furthermore, knowledge on the behavioral context in which specific sound types are produced can be used to derive information on habitat usage. Here we describe an approach for combining multi-year, year-round marine mammal presence data from passive acoustic recorders with a selected set of relevant environmental parameters to develop species-specific habitat models. Our project comprises multi-year passive acoustic data collected in Antarctic coastal as well as offshore areas throughout the Weddell Sea. Some of the species recorded are sighted only rarely during visual surveys, but are acoustically abundant in our recordings, such as the Antarctic blue whale (Balaenoptera musculus intermedia), humpback whale (Megaptera novaeangliae), fin whale (B. physalus), leopard seal (Hydrurga leptonyx), crabeater seal (Lobodon carcinophaga) and Ross seal (Ommatophoca rossii). The model will incorporate both static environmental variables, such as depth or slope, and dynamic variables, such as sea surface temperature, sea surface height, sea ice concentration and their derivatives. The project aims at furthering our current understanding of marine mammal habitat affinities in the Southern Ocean by constructing species-specific habitat models at yet unprecedented spatial and temporal time scales.
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    Einfluss von Küstenschutzbauwerken auf Crustacea und bodenassoziierte Fischarten vor Helgoland (2013)
    In:  EPIC3Einladung zum Dialog: Küstenforschung, Küstennutzung und Küstenschutz, Handelskammer Hamburg, 2013-03-04-2013-03-06
    Details
    Publication Date: 2019-07-17
    Description: Küstenschutzbauwerke werden aufgrund des vorhergesagten Klimawandels eine immer wichtigere Rolle im Küstenschutz einnehmen. Die ökologischen Auswirkungen solcher Strukturen auf die natürliche Umgebung sind jedoch insbesondere im Sublitoral bisher wenig erforscht. Seit 2010 untersucht die Arbeitsgruppe „In situ Ecology and Scientific Diving“ der Biologischen Anstalt Helgoland des Alfred-Wegener-Instituts für Polar- und Meeresforschung den Einfluss von experimentell eingebrachten Tetrapodenfeldern auf die Crustacea- und bodenassoziierte Fischgemeinschaft 400 m nördlich vor Helgoland. Anhand festgelegter Zählstationen entlang von Unterwassertransekten wird die raum-zeitliche Dynamik der Fische und Krebse im Umfeld der künstlichen Bauwerke erfasst. Die dreidimensionalen Strukturen bieten potentiell einen attraktiven Lebensraum durch Versteckmöglichkeiten in Form von Mirkohabitaten und durch ein zusätzliches Futterangebot in Form von Aufwuchsorganismen. Die Ergebnisse zeigen, dass Fische aus der natürlichen Umgebung abwandern und sich in direkter Nähe der Tetrapodenfelder in signifikant höheren Abundanzen konzentrieren. Weiterhin wurde im zeitlichen Verlauf eine Zunahme an Jungfischen beobachtet. Dem gegenüber steht eine signifikante Abnahme der mittleren Fischabundanzen im natürlichen Umfeld der künstlichen Bauwerke, dessen Einfluss auf das Gesamtsystem bisher weitgehend unbekannt ist. Die Untersuchungen zeigen, dass weiterführende Feldstudien an Küstenschutzbauwerken entlang der Europäischen Küsten unerlässlich sind, um mittel- und langfristige ökologische Konsequenzen abschätzen zu können.
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    Wave Propagation Theories and Applications (2013)
    INTECH
    In:  EPIC3Wave Propagation Theories and Applications, Tsunami Wave Propagation, Croatia, INTECH, 380 p., pp. 43-72, ISBN: 978-953-51-0979-2
    Details
    Publication Date: 2014-04-15
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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    High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Biogeosciences, COPERNICUS GESELLSCHAFT MBH, 10, pp. 1583-1624, ISSN: 1726-4170
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Soundscapes of the Southern Ocean: Passive Acoustic Monitoring in the Weddell Sea (2013)
    In:  EPIC3Deutsche Gesellschaft für Polarforschung (DGP) 25. Internationale Polartagung „Polargebiete im Wandel“, 2013-02-18-2013-02-22
    Details
    Publication Date: 2019-07-17
    Description: The Southern Ocean provides an important habitat for marine mammals, both residential and migratory, yet long term studies of their habitat usage are hampered by the region’s seasonal inaccessibility. To overcome this problem, two autonomous underwater passive acoustic recorders were deployed in the Weddell Sea in 2008 to collect multiyear passive acoustic data. The recorders were retrieved in 2010 and the acoustic recordings were analyzed in terms of broad- and narrow-band noise. Noise in this context is defined as the acoustic energy not assignable to a specific singular source. It comprises both biotic as well as abiotic components. Noise levels were determined by selecting the quietest 10 s of each 5 min recording to exclude energetic contributions from nearby singular acoustic sources. The respective sound pressure levels (SPL) and spectra were correlated with time series of environmental covariates. The ambient noise levels of both recorders were found to be highly variable in time, ranging from 102 to 115 dB re 1 μPa (broadband SPL 5th and 95th percentile), and were correlated with the sea ice cover and wind speed. The annual variation of the ice cover caused a bimodal distribution of broadband SPL. In winter the SPL mode was 106 dB re 1 μPa. By contrast, storms over the open ocean in summer resulted in an SPL mode of 111 dB dB re 1 μPa. Variation in the ambient noise spectra could be correlated to wind speed and ice coverage. The acoustic presence of several mysticete (Antarctic blue whale, Balaenoptera musculus intermedia, fin whale, Balaenoptera physalus) and pinniped (leopard seal, Hydrurga leptonyx, crabeater seal, Lobodon carcinophaga) species created distinct bands in the spectra that contributed considerably to ambient noise levels. Comparison of the timing of these noise bands between the two acoustic data sets revealed offsets in the occurrence of acoustic activity between both recorders, suggestive of marine mammal latitudinal migration. At 66°S (the northern recorder position) fin whales were acoustically present earlier and longer in summer than at 69°S. Similarly, the blue whale chorus was more intense at 66°S than at 69°S. This might be related to the response of these species to the seasonal variation in the extension and density of sea ice. Seasonal cycles were also detected in the noise band attributed to crabeater seal vocalisations. They were annually present in September and November, followed by the leopard seals noise band, which is discernible between December and January. Results from this latitudinal recorder pair give a first impression on possible marine mammal migration patterns as well as the spatial and temporal distribution of marine mammal acoustic presence in the Southern Ocean. Additional recorders deployed in the basin wide HAFOS array will expand the spatial and temporal resolution of the acoustic dataset and allow conducting detailed multiyear studies of marine mammal acoustic presence and behavior throughout the Weddell Sea.
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  • 266
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    Fossil Organic Matter in Arctic Permafrost (2013)
    Alfred-Wegener-Institut Helmholtz-Zentrum für Polarund Meeresforschung
    In:  EPIC325th International Congress on Polar Research, Changing Polar Regions, 2013-03-17-2013-03-22Bremerhaven, Alfred-Wegener-Institut Helmholtz-Zentrum für Polarund Meeresforschung
    Details
    Publication Date: 2019-07-17
    Description: Permafrost deposits constitute a large organic carbon 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 characteristics and ice content. Organic matter stored in 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 middle Weichselian fluvial sands, middle and late Weichselian Yedoma , Taberites, Holocene cover, Holocene thermokarst and thermoerosional sediments, submerged lagoon and fluvial deposits) organic matter accumulation, preservation, and distribution are strongly linked to a broad variety of paleoenvironmental factors and specific surface and subsurface conditions. Permafrost deposits include twigs, leaves, peat lenses, grass roots, fine-distributed plant detritus, and particulate and dissolved organic matter. The vertical distribution of total organic carbon (TOC) in exposures varies from 0.1 wt % in fluvial deposits up to 45 wt % in Holocene peats. High TOC, high C/N, and low 13C values reflect less decomposed organic matter accumulated under wet, anaerobic conditions characteristic of relative temperate interglacial and interstadial periods. Glacial and stadial periods are characterized by less variable, low TOC, low C/N, and high 13C values indicating stable periglacial environments with reduced bioproductivity but stronger decomposition of organic matter under dryer, aerobic conditions. We present an in‐depth studies of organic matter distribution for the arctic permafrost zone, indicating the variability of organic matter distribution between different stratigraphical units, between the same stratigraphical unit at different study sites, and even within stratigraphic units at the same site that need to be taken into account in future inventories.
    Repository Name: EPIC Alfred Wegener Institut
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    DataFiles for: Mount Nyiragongo: An assessment and update of the current eruptive activity (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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  • 268
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    Surface Ocean CO2 Atlas (SOCAT) gridded data products (2013)
    Copernicus Publications
    In:  EPIC3Earth System Science Data, Copernicus Publications, 5(1), pp. 145-153, ISSN: 1866-3516
    Details
    Publication Date: 2015-03-19
    Description: As a response to public demand for a well documented, quality controlled, publically available, global surface ocean carbon dioxide (CO2) data set, the international marine carbon science community developed the Surface Ocean CO2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO2 data from the global oceans and coastal seas, spanning four decades (1968–2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO2 fugacity (fCO2) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions).
    Repository Name: EPIC Alfred Wegener Institut
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  • 269
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    A multi-model assessment of last interglacial temperatures (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Climate of the Past, COPERNICUS GESELLSCHAFT MBH, 9, pp. 699-717, ISSN: 1814-9324
    Details
    Publication Date: 2017-01-27
    Description: The last interglaciation (~130 to 116 ka) is a time period with a strong astronomically induced seasonal forcing of insolation compared to the present. Proxy records indicate a significantly different climate to that of the modern, in particular Arctic summer warming and higher eustatic sea level. Because the forcings are relatively well constrained, it provides an opportunity to test numerical models which are used for future climate prediction. In this paper we compile a set of climate model simulations of the early last interglaciation (130 to 125 ka), encompassing a range of model complexities. We compare the simulations to each other and to a recently published compilation of last interglacial temperature estimates. We show that the annual mean response of the models is rather small, with no clear signal in many regions. However, the seasonal response is more robust, and there is significant agreement amongst models as to the regions of warming vs cooling. However, the quantitative agreement of the model simulations with data is poor, with the models in general underestimating the magnitude of response seen in the proxies. Taking possible seasonal biases in the proxies into account improves the agreement, but only marginally. However, a lack of uncertainty estimates in the data does not allow us to draw firm conclusions. Instead, this paper points to several ways in which both modelling and data could be improved, to allow a more robust model–data comparison.
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    The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 – A new bathymetric compilation covering circum-Antarctic waters (2013)
    AMER GEOPHYSICAL UNION
    In:  EPIC3Geophysical Research Letters, AMER GEOPHYSICAL UNION, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-17
    Description: The International Bathymetric Chart of the Southern Ocean (IBCSO) Version 1.0 is a new digital bathymetric model (DBM) portraying the seafloor of the circum-Antarctic waters south of 60° S. IBCSO is a regional mapping project of the General Bathymetric Chart of the Oceans (GEBCO). IBCSO Version 1.0 DBM has been compiled from all available bathymetric data collectively gathered by more than 30 institutions from 15 countries. These data include multibeam and single beam echo soundings, digitized depths from nautical charts, regional bathymetric gridded compilations, and predicted bathymetry. Specific gridding techniques were applied to compile the DBM from the bathymetric data of different origin, spatial distribution, resolution, and quality. The IBCSO Version 1.0 DBM has a resolution of 500 x 500 m, based on a polar stereographic projection, and is publicly available together with a digital chart for printing from the project website (www.ibcso.org) and at http://dx.doi.org/10.1594/PANGAEA.805736
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    Glacier bed and ice thickness of Hallstätter Gletscher calculated from GPR measurements 2009 (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Pan genome of the phytoplankton Emiliania underpins its global distribution (2013)
    Nature Publishing Group
    In:  EPIC3Nature, Nature Publishing Group, ISSN: 0028-0836
    Details
    Publication Date: 2019-03-08
    Description: Coccolithophores have influenced the global climate for over 200 million years1. These marine phytoplankton can account for 20 per cent of total carbon fixation in some systems2. They form blooms that can occupy hundreds of thousands of square kilometres and are distinguished by their elegantly sculpted calcium carbonate exoskeletons (coccoliths), rendering themvisible fromspace3.Although coccolithophores export carbon in the form of organic matter and calcite to the sea floor, they also release CO2 in the calcification process. Hence, they have a complex influence on the carbon cycle, driving either CO2 production or uptake, sequestration and export to the deep ocean4. Here we report the first haptophyte reference genome, from the coccolithophore Emiliania huxleyi strain CCMP1516, and sequences from 13 additional isolates. Our analyses reveal a pan genome (core genes plus genes distributed variably between strains) probably supported by an atypical complement of repetitive sequence in the genome. Comparisons across strains demonstrate thatE. huxleyi, which has long been considered a single species, harbours extensive genome variability reflected in different metabolic repertoires. Genome variability within this species complex seems to underpin its capacity both to thrive in habitats ranging from the equator to the subarctic and to form large-scale episodic blooms under a wide variety of environmental conditions.
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    Summer sea ice concentration changes in the Weddell Sea and their causes (2013)
    Springer
    In:  EPIC3Earth System Science: Bridging the Gaps between Disciplines Perspectives from a Multi-disciplinary Helmholtz Research School, SpringerBriefs in Earth System Science, Heidelberg, Springer, 138 p., pp. 42-45, ISBN: ISBN 978-3-642-32234
    Details
    Publication Date: 2019-08-16
    Repository Name: EPIC Alfred Wegener Institut
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    The temporal dynamics in the deep-sea nematodes community along a bathymetric gradient (Fram Strait): impact of climate changes (2013)
    In:  EPIC3Arctic Science Summit Week, Krakow, Poland, 2013-04-17-2013-04-19
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    Publication Date: 2014-10-07
    Repository Name: EPIC Alfred Wegener Institut
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    Overview of the digital bathymetric model (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Expeditionsprogramm Polarstern Nr. 91 ANT-XXIX/4, ANT-XXIX/5, ANT-XXIX/6, ANT-XXIX/7 (2013)
    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Expeditionsprogramm, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 95 p.
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Pitfalls in invertebrate proteasome assays (2013)
    COMPANY OF BIOLOGISTS LTD
    In:  EPIC3Journal of Experimental Biology, COMPANY OF BIOLOGISTS LTD, 216, pp. 1351-1354, ISSN: 0022-0949
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
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  • 278
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    Measuring enzyme activity using the Thermo Scientific NanoDrop 3300 fluorospectrometer (2013)
    Thermo Fisher Scientific Inc.
    In:  EPIC3Thermo Fisher Scientific Application Note, Thermo Fisher Scientific Inc., T133, 2 p.
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
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    Talking about grain size (in different languages) (2013)
    In:  EPIC3IACS Snow Grain Size Workshop - Measurements ans Applications, Grenoble, 2013-04-02-2013-04-05
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    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    Evaluation of simulated Arctic cloud cover and PBL heights with satellite observations (2013)
    In:  EPIC3Special Seminar at NASA Goddard Space Flight Center, Greenbelt, MD 20771, US, 2013-01-14-2013-01-19
    Details
    Publication Date: 2019-07-16
    Description: Arctic clouds are one of the largest uncertainties in climate modeling. Based on the atmospheric regional climate model HIRHAM5, a single-column model version was developed and applied to investigate the performance of a relative humidity (RH-Scheme) and a prognostic statistical (PS-Scheme) cloud scheme in the central Arctic. The simulated total cloud cover was evaluated with satellite-based MODIS observations. The more sophisticated PS-Scheme, with the beta distribution as probability density function, was identified to perform more realistically and match the observations better than the RH-Scheme. Nevertheless, a systematic overestimation of monthly averaged total cloud cover was found. Thus, sensitivity studies were conducted to assess the effect of changing model “tuning” parameters. Lower values of the cloud ice threshold g_thr, which controls the Bergeron-Findeisen process, show here the most significant reduction of simulated Arctic cloudiness. Furthermore, the combined effect of lower g_thr and a modified PS-Scheme (permitting negatively skewed beta distributions) can be used to minimize biases relative to MODIS. The height of the planetary boundary layer (PBL) is related to various subgrid-scale processes in the PBL and can be used to describe e.g. cloud characteristics, like cloud-top entrainment rate or the evolution of stratocumulus clouds, and connections between the surface and free troposphere. This study evaluates simulated Arctic PBL heights with ERA-Interim reanalysis and GPS-RO as well as CALIOP satellite data. HIRHAM5, ERA-Interim, and CALIOP spatial patterns agree fairly well associated with the same annual cycle, but GPS-RO seems to be biased in the JJA and SON seasons. While the low bias of ERA-Interim PBL heights was reconfirmed, relative differences between HIRHAM5 and the satellite datasets show in part contrary spatial patterns due to significant differences between GPS-RO and CALIOP.
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    Introduction to Site Survey Requirements (2013)
    In:  EPIC3IODP Cretaceous Climate workshop, London, UK, 2013-04-15-2013-04-17
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    Publication Date: 2019-07-16
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    The Cenozoic evolution of ocean circulation and water mass mixing in the SW Indian Ocean over the past 20 Million years? (2013)
    In:  EPIC311th International Congress on Palaeoceanography, Barcelona, Sitges, Spain, 2013-09-01-2013-09-06
    Details
    Publication Date: 2019-07-16
    Description: Seismic reflection data from the southern Mozambique Ridge, Southwestern Indian Ocean, show indications for a substantial modification in the oceanic circulation system during the Neogene. Major reorganisations in the Indian Ocean circulation system accompanying the closure of the Indonesian Gateway led to the onset of current controlled sedimentation in the vicinity of the Mozambique Ridge at ~14 million years ago. The modifications in water mass properties and pathways are documented in changes in reflection characteristics in the Mozambique Ridge area. The evidence from the seismic reflection data is compared to deep water Pb, Nd and Hf isotope time series of the past 20 million years obtained from three hydrogenetic ferromanganese crusts and one manganese nodule from the Mozambique Ridge in the SW Indian Ocean. The isotope systems enable tracing of the source provenances of deep water masses. The ferromanganese precipitates were recovered from 1850 m, 2780 m and 3790 m water depth and were dated by cosmogenic 10Be/9Be profiles. These precipitates serve as unique archives of the long term evolution of the mixing of ambient Indian Ocean water masses ultimately originating from the North Atlantic and the Southern Ocean at the respective depths over time. The evolution of the admixture of North Atlantic Deep Water at water depths greater than 2000 m is clearly mirrored by Nd and Hf isotopic compositions systematically about one ε unit lower than those of the overlying Antarctic Intermediate Water. This stratification has only existed since 9 million years ago suggesting that the general present day large scale circulation in the intermediate and deep southern Indian Ocean has only prevailed since then.
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    Longterm experiments on life span, reproductive activity and timing of reproduction in the Arctic copepod Calanus hyperboreus (2013)
    SPRINGER
    In:  EPIC3Marine Biology, SPRINGER, ISSN: 0025-3162
    Details
    Publication Date: 2019-07-17
    Description: Several experiments were conducted with starved and fed females of the arctic copepod Calanus hyperboreus to investigate 1) their life span, reproductive period, egg production and egg viability ; 2) to study the effect of origin, ie Atlantic and Arctic waters in the Greenland Sea, on the timing of reproduction; and 3) to study the effect of time of collection on the onset of reproductive activity as a first approach to study control mechanisms of the reproductive cycle. Females collected in October produced up to 1000 eggs and had a maximum life span of 164 days without feeding, whereas fed females produced up to ca. 6000 eggs and survived up to 806 days. These observations support earlier assumptions that females were multiannual-iteroparous, ie capable to spawn in successive years, which would be unique for calanoid copepods. In starved females clutch size decreased significantly with each spawning event. Viable eggs were produced during most of the life time. There was no difference in the timing of reproductive activitiy between females from the Westspitsbergen Current and the Greenland Sea Gyre. Fed and starved females collected in May and June began to spawn circa two and four months after collection, respectively, whereas females collected in August and October started spawning at the same time, in the middle of October. This indicates initiation of reproductive activity in the field in August, coincident with the descent into deep waters. Potential cues for the untimely spawning of females collected in spring, and "unnatural" feeding in fall experiments are discussed. Their large size, robustness and combination of different types of diapause in their life cycle makes C. hyperboreus a good model organism to study diapause control mechanisms.
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    Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean (2013)
    In:  EPIC3Nature, 495(8), pp. 495-499
    Details
    Publication Date: 2019-07-17
    Description: Growing evidence suggests that the low atmospheric CO2 concentration of the ice ages resulted from enhanced storage of CO2 in the ocean interior, largely as a result of changes in the Southern Ocean. Early in the most recent deglaciation, a reduction in North Atlantic overturning circulation seems to have driven CO2 release from the Southern Ocean2–5, but the mechanism connecting the North Atlantic and the Southern Ocean remains unclear. Biogenic opal export in the low-latitude ocean relies on silicate from the underlying thermocline, the concentration of which is affected by the circulation of the ocean interior. Here we report a record of biogenic opal export from a coastal upwelling system off the coast of northwest Africa that shows pronounced opal maxima during each glacial termination over the past 550,000 years. These opal peaks are consistent with a strong deglacial reduction in the formation of silicate-poor glacial North Atlantic intermediate water (GNAIW). The loss of GNAIW allowed mixing with underlying silicate-rich deep water to increase the silicate supply to the surface ocean. An increase in westerly-wind-driven upwelling in the Southern Ocean in response to the North Atlantic change has been proposed to drive the deglacial rise in atmospheric CO2 (refs 3, 4). However, such a circulation change would have accelerated the formation of Antarctic intermediate water and sub-Antarctic mode water, which today have as little silicate as North Atlantic Deep Water and would have thus maintained low silicate concentrations in the Atlantic thermocline. The deglacial opal maxima reported here suggest an alternative mechanism for the deglacial CO2 release5,6. Just as the reduction in GNAIW led to upward silicate transport, it should also have allowed the downward mixing of warm, low-density surface water into the deep ocean. The resulting decrease in the density of the deep Atlantic relative to the Southern Ocean surface promoted Antarctic overturning, which released CO2 to the atmosphere.
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    Deep crustal structure of the Walvis Ridge at the junction with the Namibian coast (2013)
    In:  EPIC3EGU, Wien, 2013-04-07-2013-04-12
    Details
    Publication Date: 2019-07-16
    Description: The Walvis Ridge perpendicular to the African coast offshore Namibia is believed to be caused by a long-lived hotspot, which started to erupt with the opening of the South Atlantic in mid Cretaceous. The ridge in combination with the large igneous provinces (Etendeka and Parana) in South America and Namibia is today considered to be a classical model for hotspot driven continental break-up. To unravel details on how the crust and mantle were modified by such a major thermal event, a large-scale geophysical on- and offshore experiment was conducted in 2011. We present p-wave velocity models of two active seismic profiles along and across Walvis Ridge. The profile along the ridge continues onshore, has a total length of ∼730 km and consists of 28 ocean bottom stations, 50 land stations and 8 dynamite shots. This section reveals a complex structure with multiple buried seamounts, strong lateral velocity gradients and indication of a high velocity body at the crust-mantle boundary beneath the shelf area. Lower crustal velocities range from 6.5 km/s in the west to 7.0 km/s in the east while the crustal thickness is approximately 28 km at the coast thinning westwards. The second profile perpendicular to the ridge is located about 140 km west of the first profile, has a length of ∼480 km and consists of 27 ocean bottom stations. The crustal thickness is well constrained by multiple Moho reflections showing a thickness of 20km under the crest of the ridge and gradually thinning to 8km towards north and south. A seamount marks the northern termination of the ridge leading to an abrupt thickening of the crust to 14km before reaching the Angola Basin. While crustal velocities of 5.5 km/s and 6.5 km/s in the upper and lower crust are similar to the first profile, lower crustal velocities north of the crest are approximately 6% higher.
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  • 286
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    Der Beitrag der Erwärmung des Tiefen- und Bodenwassers im Weddellmeer zum globalen Klimawandel (2013)
    In:  EPIC325. Internationale Polartagung, Hamburg, Germany, 2013-03-17-2013-03-22
    Details
    Publication Date: 2019-07-16
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  • 287
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    Microstructure through an Ice Sheet (2013)
    Trans Tech Publications
    In:  EPIC3Recrystallization and Grain Growth V, Materials Science Forum, Zurich, Switzerland, Trans Tech Publications, 753, 590 p., pp. 481-484, ISBN: 978-3-03785-688-8, ISSN: 1662-9752
    Details
    Publication Date: 2014-04-15
    Description: Ice cores through an ice sheet can be regarded as a sample of a unique natural deformation experiment lasting up to a million years. Compared to other geological materials forming the earth‘s crust, the microstructure is directly accessible over the full depth. Controlled sublimation etching of polished ice sections reveals pores, air bubbles, grain boundaries and sub-grain boundaries at the surface. The microstructural features emanating at the surface are scanned. A dedicated method of digital image processing has been developed to extract and characterize the grain boundary networks. First preliminary results obtained from an ice core drilled through the Greenland ice sheet are presented. We discuss the role of small grains in grain size analysis and derive from the shape of grain boundaries the acting driving forces for grain boundary migration.
    Repository Name: EPIC Alfred Wegener Institut
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  • 288
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    Accumulation and stable-isotope studies at Kohnen station, Dronning Maud Land, Antarctica, from 1999 through 2011 (2013)
    In:  EPIC325. Internationale Polartagung der Deutschen Gesellschaft für Polarforschung "Polargebiete im Wandel", Universität Hamburg, 2013-03-17-2013-03-22Hamburg
    Details
    Publication Date: 2019-07-17
    Description: The area of the later Kohnen station (75°00’06”S, 0°04’04”E) in Dronning Maud Land, Antarctica, was visited the first time during the EPICA-pre site survey in the austral summer 1997/98. In 1999/2000 the construction of the base started. At the same time a glaciological programme was initiated to study snow accumulation and stable isotopes in the surroundings of the base and the site of the EDML ice core, respectively. The data of 20 snow pits cover the period 1986-2010. The pits had been sampled with a depth resolution between 1.5cm and 5cm. Linear fits through the time series do not show a significant trend neither for accumulation nor δ18O content. However, for the year 2008 an outstanding high accumulation rate was found in all 6 snow pits which were digged in January 2011. The average δ18O content and mean accumulation rate for the period 1259-1816 from 4 nearby firn cores (B32, B34, B37 and EDML) is -45.01 ‰-SMOW and 62.3 kg m-2 a-1, respectively. Both the mean annual isotope content and the mean annual accumulation rate during the past 25 years are above the long term average. They display values of -44.00 ±1.07 ‰-SMOW and 72.5 ±11.2 kg m-2 a-1 respectively. Thus, the results of the snow pit studies fit into the general pattern of increasing accumulation rates and increasing stable-isotope contents of snow during the 20th century.
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    Life cycle of the pseudocolonial dinoflagellate Polykrikos kofoidii (Gymnodiniales, Dinoflagellata) (2013)
    WILEY-BLACKWELL PUBLISHING
    In:  EPIC3Journal of Phycology, WILEY-BLACKWELL PUBLISHING, 49, pp. 298-317, ISSN: 0022-3646
    Details
    Publication Date: 2019-07-17
    Description: The athecate, pseudocolonial polykrikoid dinoflagellates show a greater morphological complexity than many other dinoflagellate cells and contain not only elaborate extrusomes but sulci, cinguli, flagellar pairs, and nuclei in multiple copies. Among polykrikoids, Polykrikos kofoidii is a common species that plays an important role as a grazer of toxic planktonic algae but whose life cycle is poorly known. In this study, the main life cycle stages of P. kofoidii were examined and documented for the first time. The formation of gametes, 2-zooid-1-nucleus stages very different from vegetative cells, was observed and the process of gamete fusion, isogamy, was recorded. Karyogamy followed shortly after completed plasmogamy. A complex reorganization of furrows (cinguli and sulci) and flagella followed zygote formation, resulting in a 4-zooid zygote with one nucleus. The fate of zygotes under different nutritional conditions was also investigated; well-fed zygotes were able to reenter the vegetative cycle via meiotic divisions as indicated by nuclear cyclosis. However, nuclear cyclosis was preceded by a presumably mitotic division of the primary zygote nucleus which by definition would imply that P. kofoidii has a diplohaplontic life cycle. Nuclear cyclosis in germlings hatched from spiny resting cysts indicate that these cysts are of zygote origin (hypnozygotes). Hypnozygote formation, cyst hatching, the morphology of the germling (a 1-zooid cell), and its development into a normal pseudocolony are documented here for the first time. There is evidence that P. kofoidii has a system of complex heterothallism.
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    Mesozooplankton community development at elevated CO2 concentrations: results from a mesocosm experiment in an Arctic fjord (2013)
    Copernicus Publications
    In:  EPIC3Biogeosc, Copernicus Publications, 10, pp. 1391-1406
    Details
    Publication Date: 2019-07-17
    Description: The increasing CO2 concentration in the atmosphere caused by burning fossil fuels leads to increasing pCO2 and decreasing pH in the world ocean. These changes may have severe consequences for marine biota, especially in cold-water ecosystems due to higher solubility of CO2. However, studies on the response of mesozooplankton communities to elevated CO2 are still lacking. In order to test whether abundance and taxonomic composition change with pCO2, we have sampled nine mesocosms, which were deployed in Kongsfjorden, an Arctic fjord at Svalbard, and were adjusted to eight CO2 concentrations, initially ranging from 185 μatm to 1420 μatm. Vertical net hauls were taken weekly over about one month with an Apstein net (55 μm mesh size) in all mesocosms and the surrounding fjord. In addition, sediment trap samples, taken every second day in the mesocosms, were analysed to account for losses due to vertical migration and mortality. The taxonomic analysis revealed that meroplanktonic larvae (Cirripedia, Polychaeta, Bivalvia, Gastropoda and Decapoda) dominated in the mesocosms while copepods (Calanus spp., Oithona similis, Acartia longiremis and Microsetella norvegica) were found in lower abundances. In the fjord copepods prevailed for most of our study. With time, abundance and taxonomic composition developed similarly in all mesocosms and the pCO2 had no significant effect on the overall community structure. Also, we did not find significant relationships between the pCO2 level and the abundance of single taxa. Changes in heterogeneous communities are, however, difficult to detect, and the exposure to elevated pCO2 was relatively short. We therefore suggest that future mesocosm experiments should be run for longer periods.
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    Ice-rich Permafrost and thermal denudation in the Batagay area (Yana Upland, East Siberia) (2013)
    Academic Publishing House GEO
    In:  EPIC3Earth Cryosphere (Kriosfera Zemli), Academic Publishing House GEO, 17(1), pp. 56-58, ISSN: 1560-7496
    Details
    Publication Date: 2019-07-17
    Description: Ice-rich permafrost in the Yana Upland has been investigated. The composition and structure of the permafrost has been determined. Their role in thermal denudation processes has been examined. The response of the ice-rich permafrost to recent climate change has been assessed.
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  • 292
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    Ice matters. Arctic and Antarctic under-ice communities linking sea ice with the pelagic food web (2013)
    In:  EPIC325. Internationale Polartagung, University of Hamburg, 2013-03-17-2013-03-22
    Details
    Publication Date: 2019-07-17
    Description: In both Polar Regions, sea ice environments are undergoing rapid environmental change. Because sea ice constitutes an important habitat for numerous species, as well as an important carbon source during critical periods of the year, these changes impact significantly on ecosystem functioning, biodiversity, species distribution and population sizes, including commercially exploited fish stocks. Species dwelling at the ice-water interface (e.g. Antarctic krill and Arctic cod) play a key role in this context as trophic carbon transmitters from the sea ice into pelagic food webs, and ultimately to the deep sea benthos. Quantifying under-ice communities was hampered in the past by the inaccessibility of the ice underside to conventional sampling gear. Using a new under-ice trawl, it could be shown that Antarctic krill concentrates under sea ice almost year-round, and that krill dwelling under ice are significantly under-estimated by pelagic nets and sonars. An Arctic expedition in 2012 using the same sampling gear brought evidence of a vivid under-ice community even in the biologically poor-considered central Arctic Ocean. Using a bio-environmental sensor array during under-ice fishing enabled fine-scale characterization of sea ice habitat properties as a basis for statistical modeling of under-ice species distribution. During the talk, past results from under-ice fishing in the Southern Ocean will be summarized, and complemented by preliminary results from the Arctic Ocean to elucidate similarities and differences of polar under-ice communities in both hemispheres.
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    Long-term eddy-covariance measurements from FINO2 platform above the Baltic Sea (2013)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
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    From the chlorophyll-a in the surface layer to its vertical profile: a Greenland Sea relationship for satellite applications. (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Ocean Science, COPERNICUS GESELLSCHAFT MBH, 9(2), pp. 431-445, ISSN: 1812-0784
    Details
    Publication Date: 2019-12-03
    Description: Current estimates of global marine primary production range over a factor of two. Improving these estimates requires an accurate knowledge of the chlorophyll vertical profiles, since they are the basis for most primary production models. At high latitudes, the uncertainty in primary production estimates is larger than globally, because here phytoplankton absorption shows specific characteristics due to the low-light adaptation, and in situ data and ocean colour observations are scarce. To date, studies describing the typical chlorophyll profile based on the chlorophyll in the surface layer have not included the Arctic region, or, if it was included, the dependence of the profile shape on surface concentration was neglected. The goal of our study was to derive and describe the typical Greenland Sea chlorophyll profiles, categorized according to the chlorophyll concentration in the surface layer and further monthly resolved profiles. The Greenland Sea was chosen because it is known to be one of the most productive regions of the Arctic and is among the regions in the Arctic where most chlorophyll field data are available. Our database contained 1199 chlorophyll profiles from R/Vs Polarstern and Maria S. Merian cruises combined with data from the ARCSS-PP database (Arctic primary production in situ database) for the years 1957–2010. The profiles were categorized according to their mean concentration in the surface layer, and then monthly median profiles within each category were calculated. The category with the surface layer chlorophyll (CHL) exceeding 0.7 mg C m−3 showed values gradually decreasing from April to August. A similar seasonal pattern was observed when monthly profiles were averaged over all the surface CHL concentrations. The maxima of all chlorophyll profiles moved from the greater depths to the surface from spring to late summer respectively. The profiles with the smallest surface values always showed a subsurface chlorophyll maximum with its median magnitude reaching up to three times the surface concentration. While the variability of the Greenland Sea season in April, May and June followed the global non-monthly resolved relationship of the chlorophyll profile to surface chlorophyll concentrations described by the model of Morel and Berthon (1989), it deviated significantly from the model in the other months (July–September), when the maxima of the chlorophyll are at quite different depths. The Greenland Sea dimensionless monthly median profiles intersected roughly at one common depth within each category. By applying a Gaussian fit with 0.1 mg C m−3 surface chlorophyll steps to the median monthly resolved chlorophyll profiles of the defined categories, mathematical approximations were determined. They generally reproduce the magnitude and position of the CHL maximum, resulting in an average 4% underestimation in Ctot (and 2% in rough primary production estimates) when compared to in situ estimates. These mathematical approximations can be used as the input to the satellite-based primary production models that estimate primary production in the Arctic regions.
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    Polargebiete und Klima (2013)
    In:  EPIC3Polarforscher gehen in die Schule, 25. Internatonale Polartagung der Deutschen Ges. f. Polarforschung, Gymnasium Harksheide, Norderstedt, 2013-03-22-2013-03-22Norderstedt
    Details
    Publication Date: 2019-07-17
    Description: Herr Oerter berichtet von Tiefbohrungen durch das Inlandseis der Antarktis und darüber, was man aus den gewonnenen Eiskernen für das Klima der letzten Phase der Eiszeit, unsere gegenwärtige Warmzeit, und den Einfluss der Menschen in den letzten Jahrhunderten ableiten kann.
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    Ocean color products from hyperspectral satellite data (2013)
    In:  EPIC33rd EOS Topial Meeting on Blue Photonics – Optics in the Sea (Blue Photonics 3), Royal Netherlands Institute for Sea Research (NIOZ), Texel (NL), 2013-03-18-2013-03-20
    Details
    Publication Date: 2019-07-17
    Description: Quantitative distributions of major functional PFTs of the world ocean improve the understanding of the role of marine phytoplankton in the global marine ecosystem and biogeochemical cycles. Chl-a fluorescence gives insight on the health of phytoplankton and is related to phytoplankton biomass. In this study, global ocean color satellite products of different dominant phytoplankton functional types' (PFTs') biomass and chlorophyll fluorescence retrieved from hyperspectral satellite data using Differential Optical Absorption Spectroscopy applied to phytoplankton (PhytoDOAS) are presented (see also Bracher et al. 2009, Sadeghi et al. 2012a). Data are compared to ocean color products from multispectral sensors and application of the hyperspectral data set in studying phytoplankton dynamics are presented (Sadeghi et al. 2012b, Ying et al. 2012). Although current hyperspectral sensors have poor spatial resolution (〉30kmx30km), they are useful for the verification and improvement of the high spatially resolved multi-spectral ocean color products. Future applications of PhytoDOAS retrieval to other hyperspectral sensors and its synergistic use with information gained from multispectral ocean color sensors are proposed.
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    Extraction and parametrization of grain boundary networks in glacier ice, using a dedicated method of automatic image analysis (2013)
    In:  EPIC3Journal of Microscopy, 250(2), pp. 130-141, ISSN: 00222720
    Details
    Publication Date: 2019-07-17
    Description: Microstructure analysis of polar ice cores is vital to understand the processes controlling the flow of polar ice on the microscale. This paper presents an automatic image processing framework for extraction and parametrization of grain boundary networks from images of the NEEM deep ice core. As cross-section images are acquired using controlled surface sublimation, grain boundaries and air inclusions appear dark, whereas the inside of grains appears grey. The initial segmentation step of the software is to separate possible boundaries of grains and air inclusions from background. A Machine learning approach is utilized to gain automatic, reliable classification, which is required for processing large data sets along deep ice cores. The second step is to compose the perimeter of section profiles of grains by planar sections of the grain surface between triple points. Ultimately, grain areas, grain boundaries and triple junctions of the later are diversely parametrized. High resolution is achieved, so that small grain sizes and local curvatures of grain boundaries can systematically be investigated.
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    Carbon and nitrogen stable isotope signatures of deep-sea meiofauna follow oceanographical gradients across the Southern Ocean (2013)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Progress In Oceanography, PERGAMON-ELSEVIER SCIENCE LTD, 110, pp. 69-79, ISSN: 0079-6611
    Details
    Publication Date: 2019-07-17
    Description: Carbon (d13C) and nitrogen (d15N) stable isotope values of deep-sea benthic copepods, nematodes, and sediments were determined along a latitudinal transect covering bathyal and abyssal depths in the Southern Ocean and the Weddell Sea (49�S–70�S). This is the first time geographical patterns in stable isotope composition including d15N are reported for deep-sea meiofauna. In agreement with previous findings on isotopic patterns of sea-surface organic matter, the deep-sea meiofauna d13C values gradually declined with latitude. In the nematodes, d15N values were depleting southwards and followed the known gradients of increasing nitrate concentrations with decreasing d15N values available to primary producers in the surface waters. Differences in productivity, water depth, and degradation state of the organic matter at the seafloor along the transect did not influence the southwards declining trend observed in the stable isotope values of the deep-sea meiofauna. The most depleted 13C values were detected in the communities of Maud Rise. The southernmost Lazarev Sea station was an expected exception to this trend: its long-lasting sea-ice cover and a primary production dominated by 13C-enriched ice algae may have lead to the heavier isotopic signatures that were encountered in the organisms and sediments at 70�S. It is suggested that the bulk of benthic meiofauna mainly feeds on degraded organic matter, a food source that is continuously available throughout the year, because only small differences of sediment d13C and the values for meiofauna were detected. The isotopic composition of consumers such as copepods and nematodes are a combination of geographical conditions and the organisms’ position in the food web. Hence, the comparison of stable isotope values of deep-sea meiofauna over a wide geographical range yields basic information for detailed follow-up studies on Antarctic meiofauna foodwebs
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    Properties of grain boundary networks in the NEEM ice core (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, 2013-04-07-2013-04-12
    Details
    Publication Date: 2019-07-17
    Description: The microstructure along the entire NEEM ice core (North-West Greenland, 2537 m length) drilled in 2008-2011 has been analyzed based on a large data set of sublimation groove images. The sublimated surface of vertical section series (six consecutive 6 x 9 cm2 sections in steps of 20 m – in total about 800 images) have been scanned by a Large Area Scanning Macroscope. In these cross-section images 10-15 micron wide grain boundary grooves and air bubbles appear dark, whereas the inside of grains appears gray (further developed by [S. Kipfstuhl et al., 2006, Journal of Glaciology, 52, 398-406]). A dedicated method of automatic image analysis has recently been developed to extract and parameterize the grain boundary networks of this set [T. Binder et al., 2013, Journal of Microscopy, in press]. In contrast to the microstructure obtained from thin sections between crossed polarizers in transmitted light, sublimation groove images in reflected light allow to include small grains (equivalent radius of 65 micron) in the size distribution. It has become possible to extract continuous curvature values of grain boundaries, an estimate of the lower bound of the stored strain energy and the dislocation density. In this contribution we give an overview on profiles of different calculated parameters related to deformation and recrystallization mechanisms. In older glaciological studies the value of the lower cut-off for grain sizes considered for calculation of a mean grain size has been arbitrary. We suggest to compare different definitions of the lower cut-off in the size. With respect to the important question which processes are dominating the grain size evolution in the late- to middle-Holocene, high sensitivity to the definition of this cut-off has been found [T. Binder et al., 2013, Materials Science Forum, 753, 481-484]. Between 250 m and 1000 m depth the curvature of grain boundaries steadily increases and grains become more irregularly shaped which correlates with increasing pressure of air bubbles. In the NEEM ice core the depth of the transition from air bubbles to clathrate hydrates clearly can be separated from the depth where the transition from Holocene to the last glacial takes place. In this way, we found that the shape of grains is highly influenced by air bubbles, whereas the size of the grains is more sensitive to climatic transitions.
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    Content and Vulnerability of Fossil Organic Matter in Ice-Rich Siberian Permafrost – a Case Study (2013)
    In:  EPIC3EGU General Assembly 2013, Vienna, Austria, 2013-04-07-2013-04-12Geophysical Research Abstracts
    Details
    Publication Date: 2019-07-17
    Description: During the late Pleistocene, a large pool of organic matter (OM) accumulated in ice-rich deposits of the arctic permafrost zone. Because of the potential re-introduction of this stored carbon into the global cycle from degrading permafrost (i.e. decomposed OM) as climate-relevant gases, the OM inventory of ice-rich permafrost deposits is important to current concerns about global warming. The objective of this presentation is to deduce the quality of OM stored in the studied permafrost sediments. The approach to estimate the OM quality is to use degradation parameters (e.g. C/N, �13C) based on the assumption that low degraded OM is more labile and has higher vulnerability for decomposition. Standard sedimentological and a molecular marker (biomarker) approach are applied. The study site is located on the west coast of the Buor Khaya Peninsula (N 71.6�, E 132.2�), Laptev Sea (Russia). Stratigraphically, two sediment units are distinguished. The first unit is composed of late Pleistocene ice-rich permafrost (Yedoma). The second unit consists of Holocene thermokarst (Alas) deposits. The mean bulk density of sediments from both units is ca. 1 g/cm3. The average total organic carbon (TOC) content is 2.4 wt% for Yedoma, 2.8 wt% for thermokarst deposits. The volumetric organic carbon contents of the Yedoma and thermokarst deposits are 13+-11 kg/m3 and 22+-11 kg/m3, respectively. The degree of OM degradation from both units is low (mean C/N 10, mean �13C -26.5 h because the deposits accumulated at relatively fast rates and the OM underwent only a short time of decomposition before it was incorporated into permafrost. Originating from microorganisms, archaeal lipids like archaeol can be used as a marker for methanogenic microbial communities or as a proxy for past microorganism activity. The archaeol concentrations reveal higher microbial activity in thermokarst deposits than in Yedoma deposits. The n-alkane and n-fatty acid parameters (carbon preference index and average chain length) show source signal from vascular land plants and prove a minor degradation state of the OM. OM parameters such as the total amount of organic carbon and the C/N ratio and acetate concentrations indicate labile OM.
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