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  • 1
    Publication Date: 2024-05-16
    Description: The anthropogenic emissions of CO2 and other climate-active gases lead to a steep increase of global temperatures. Global climate change is particularly amplified in the Arctic (e.g., Serreze et al., 2009; Serreze and Barry, 2011). Increasing temperatures and the rapid sea ice decline have shown profound effects on life in the Arctic ecosystem (Wassmann et al., 2011). Climate model predictions suggest a seasonally sea ice-free Arctic well before the first half of this century (Overland and Wang, 2013; Docquier and Koenigk, 2021). The composition, structure and function of the Arctic microbiome will be altered with distinct effects on the marine system, on primary productivity, carbon fluxes and food web structures. Changes in the composition and structure of primary producers were already observed in Fram Strait (Nöthig et al., 2015), the boundary and highly dynamic zone between the Atlantic and the Arctic Ocean. These changes were reflected in the export flux of particulate organic matter (Lalande et al., 2013), also observable in the benthic communities (Jacob, 2014). Thus, understanding how the microbial communities changed over time under different environmental conditions is a scientific task needed to assess future changes in the Arctic ecosystem. This thesis aimed to understand the composition, distribution and function of bacteria, archaea and eukaryotic communities in Fram Strait across different spatial and temporal scales and their relationship with environmental variables. The overall objective was to identify signature groups and key factors of change, to provide a baseline to the effects of climate change and sea ice retreat. It provides a comprehensive overview of the Arctic microbiome by the incorporation of seawater, sinking particles and sea ice samples to identify key microbial indicators of change and environmental drivers in these communities. Samples were obtained in the frame work of the Long-Term Ecological Research (LTER) site HAUSGARTEN and the FRontiers in Marine Monitoring (FRAM) program. The results of Chapter I and Chapter II highlight the usage of methods free of compositional- bias and meta’omics approaches necessary to understand the role of microbial communities. The observations in Chapter I revealed that different water masses characterized by different physicochemical conditions harboured different active microbial communities. A late phytoplankton bloom dominated by diatoms in the surface waters of the eastern Fram Strait was identified, where members of the Bacteroidetes, Alteromonadales, Oceanospirillales and Rhodobacterales were significantly active. Abundant transcripts of transporters and fundamental cellular functions supported the degradation of organic matter. The deeper waters of Atlantic origin were marked by strong chemolithotrophic activities by members of Thaumarchaeota. In Chapter II I analysed bacterial and archaeal groups in deep-sea waters that benefitted from a phytoplankton bloom at the surface. Chapter III studied the development of microbial composition of sinking particles using a 12-year time-series study. The presence of sea ice and the passing warm anomaly were the drivers of change in these communities. In Chapter IV, microcosm experiments revealed bacterial taxa that responded to eukaryotes and substrates sourced from the sea ice during sea ice melt in seawater. Altogether, the results of this thesis provide baseline knowledge to better assess the effects of climate change on the Arctic microbiome and the consequences for ecosystem functioning and carbon cycling.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
    Format: application/pdf
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  • 2
    Publication Date: 2024-05-15
    Description: We create a deep neural network based approach for the geospatial predicition of total organic carbon percentages in marine sediments. The code in the repository includes jupyter notebooks and python files to pre-process the data, train the models and post-process the outputs.
    Type: Software , NonPeerReviewed
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  • 3
    Publication Date: 2024-05-15
    Description: The macrofauna in soft sediments of the deep seafloor is generally diverse and represents a comparatively well-studied faunal group of deep-sea ecosystems. In the abyss of the Clarion Clipperton Fracture Zone (CCFZ) in the NE Pacific, macrofauna are major contributors to benthic biodiversity. Their distribution, composition, and diversity have been frequently investigated to assess the potential impacts of future mining activities on the resident fauna. In this study, patterns of densities and community structure of CCFZ macrobenthic infauna and their relationships with a range of environmental and climatic variables were examined, with a special focus on communities from the eastern German contract area (referred to as BGR CA). However, comparisons were also made with other contractor areas (e.g., IFREMER, IOM, GSR) and one Area of Particular Environmental Interest (APEI3). Material for this study was obtained by means of a box corer during six expeditions to the CCFZ between 2013 and 2018 resulting in 148 samples. Our study uncovered notable spatial and temporal variations in both faunal densities and community composition. While areas within the BGR CA exhibited a similar community composition, slight differences were observed between the various CAs and APEI3. Surprisingly, we found an unexpected negative correlation between food availability and both macrofaunal density and community structure that may be attributed to differences in sampling methodologies and pronounced temporal variation. Furthermore, we explored the impact of climatic fluctuations associated with the El Niño/Southern Oscillation (ENSO) on macrofaunal densities, observing an increase during warm (El Niño) events. Our findings underscore the challenges of accurately assessing spatial and temporal variations in the absence of standardised sampling protocols. Hence, we emphasize the importance of adopting standardised protocols to enhance data comparability, thereby fostering a deeper understanding of the underlying factors influencing spatial and temporal changes in macrofauna community structure within the CCFZ.
    Type: Article , PeerReviewed
    Format: text
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  • 4
    Publication Date: 2024-05-15
    Description: In this paper we describe the implementation of the carbon isotopes 13C and 14C (radiocarbon) into the marine biogeochemistry model REcoM3. The implementation is tested in long-term equilibrium simulations where REcoM3 is coupled with the ocean general circulation model FESOM2.1, applying a low-resolution configuration and idealized climate forcing. Focusing on the carbon-isotopic composition of dissolved inorganic carbon (δ13CDIC and Δ14CDIC), our model results are largely consistent with reconstructions for the pre-anthropogenic period. Our simulations also exhibit discrepancies, e.g. in upwelling regions and the interior of the North Pacific. Some of these differences are due to the limitations of our ocean circulation model setup, which results in a rather shallow meridional overturning circulation. We additionally study the accuracy of two simplified modelling approaches for dissolved inorganic 14C, which are faster (15 % and about a factor of five, respectively) than the complete consideration of the marine radiocarbon cycle. The accuracy of both simplified approaches is better than 5 %, which should be sufficient for most studies of Δ14CDIC.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Publication Date: 2024-05-15
    Description: Oceanic detachment faulting, a major mode of seafloor accretion at slow and ultraslow spreading ridges, is thought to occur during magma‐poor phases and be abandoned when magmatism increases. In this framework, detachment faulting is the result of temporal variations in magma flux, which is inconsistent with recent geophysical observations at the Longqi segment on the Southwest Indian Ridge (49°42′E). In this paper, we focus on this sequentially active detachment faulting system that includes an old, inactive detachment fault and a younger, active detachment fault. We investigate the mechanisms controlling the temporal evolution of this tectonomagmatic system by using 2D mid‐ocean ridge spreading models that simulate faulting and magma intrusion into a visco‐elasto‐plastic continuum. Our models show that temporal variations in magma flux alone are insufficient to match the inferred temporal evolution of the sequentially active detachment system. Rather we find that sequentially active detachment faulting spontaneously occurs at the Longqi segment as a function of lithospheric thickness. This finding is in agreement with an analytical model, which shows that a thicker axial lithosphere results in a smaller fault heave and that a flatter angle in lithosphere thickening away from the accretion axis stabilizes the active fault. A thicker axial lithosphere and its flatter off‐axis angle combined have the potential to modulate sequentially active detachment faulting at the Longqi segment. Our results thus suggest that temporal changes of magmatism are not necessary for the development and abandonment of detachment faults at ultraslow spreading ridges.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: video
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  • 6
    Publication Date: 2024-05-15
    Description: Abstract
    Description: The goal of the UPFLOW project is to develop new high-resolution seismic imaging approaches along with new data collection, and to use them to constrain upward flow in unprecedented detail. We conducted a large off-shore experiment in the Azores-Madeira-Canary Islands region, which is a unique natural laboratory with multiple upwellings that are poorly understood in general. UPFLOW deployed and recovered 49 ocean bottom seismometers (OBSs) in a ~1,000×2,000 km2 area in the Azores-Madeira-Canary Islands region starting in July 2021 for ~13 months, with an average spacing of ~150-200 km. The seismic deployment and recovery involved institutions from five different countries: Portugal (IPMA, IDL, Univ. of Lisbon, ISEL), Ireland (DIAS), UK (UCL), Spain (ROA) and Germany (Potsdam University, GFZ, Geomar, AWI). 32 OBSs were be rented from the DEPAS international pool of instruments maintained by the Alfred Wegener Institute (Bremerhaven), Germany, while other institutions borrowed additional instruments (7 from DIAS, 4 from IDL, 3 from ROA, 4 from GEOMAR). Most of the instruments have three-component wideband seismic sensors, but three different designs of OBS frames were used. Waveform data is available from the GEOFON data centre, under network code 8J, and is embargoed until May 2028. We want to acknowledge the exceptional support of the whole team of able seaman, steward, cooks, engineers, mechanicians, electricians and motorman assistants of the vessel RRV Mário Ruivo. With special Thanks to José Ângelo Gomes (Captain), Luís Ramos (Superintendent), Mafalda Carapuço Vessel’s manager (IPMA), Henrique Ferreira Land logistics (IPMA), Celine Ahmed and Jen Amery (Administrative support at UCL)
    Keywords: GEOMAR ; iMarl-DIAS ; IDL ; ROA ; Pressure ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 EARTHQUAKES ; EARTH SCIENCE 〉 SOLID EARTH 〉 TECTONICS 〉 VOLCANIC ACTIVITY ; In Situ/Laboratory Instruments 〉 Magnetic/Motion Sensors 〉 Seismometers ; In Situ Land-based Platforms 〉 GEOPHYSICAL STATIONS/NETWORKS ; In Situ Land-based Platforms 〉 GEOPHYSICAL STATIONS/NETWORKS 〉 SEISMOLOGICAL STATIONS ; OBS ; Passive seismic ; Velocity ; MiniSEED ; DEPAS ; Amphibious ; Mantle plume ; Regional network ; Displacement ; Three-component[g] ; Natural
    Type: Dataset , Seismic Network
    Format: 2.7T
    Format: .mseed
    Format: XML
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  • 7
    Publication Date: 2024-05-15
    Description: Abstract
    Description: Version History:15 June 2020:Initial release of the data. Note that the initial version number is 0002 in order to reflect the consistent data processing of this data set and Version 0002 of the data set Sasgen et al. (2019, http://doi.org/10.5880/GFZ.GRAVIS_06_L3_ICE).---------------------------------------------------------------------------------------------GRACE/GRACE-FO Level-3 products based on COST-G RL01 Level-2B products (Dahle & Murböck, 2020) representing ice-mass changes for the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). The ice-mass changes are provided both as basin average product and as gridded product.Basin-average ice-mass changes are obtained using the inversion procedure based on a forward modelling approach as described in Sasgen et al. (2013) for the AIS and Sasgen et al. (2012) for the GIS.Gridded ice-mass changes are provided at polar-stereographic grids with a grid spacing of 50 x 50 km^2. The applied algorithm is based on tailored sensitivity kernels (Groh & Horwath, 2016), and has also been used to generate gravimetric mass balance products within the ESA Climate Change Initiative (CCI) projects for the AIS and the GIS.These Level-3 products are visualized at GFZ's web portal GravIS (http://gravis.gfz-potsdam.de).Link to data products: ftp://isdcftp.gfz-potsdam.de/grace/GravIS/COST-G/Level-3/ICE
    Keywords: Gravity Recovery And Climate Experiment (GRACE) ; GRACE Follow-on (GRACE-FO) ; Level-3 ; Mass ; Mass Transport ; Ice-mass Change ; Time Variable Gravity ; Antarctic Mass Balance ; Greenland Mass Balance ; Sea-level Change ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD ; Earth Observation Satellites 〉 NASA Earth System Science Pathfinder 〉 GRACE
    Language: English
    Type: Dataset , Dataset
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  • 8
    Publication Date: 2024-05-15
    Description: Abstract
    Description: Version History:09 June 2020:Release of Version 0002. This is an update of Version 0001 of the same data set. All changes and updates are documented in the changelog available via the data download section. Previously released versions of this data set are available at ftp://isdcftp.gfz-potsdam.de/grace/GravIS/GFZ/Level-3/ICE/old_versions---------------------------------------------------------------------------------------------GRACE/GRACE-FO Level-3 products representing ice-mass changes for the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). The ice-mass changes are provided both as basin average product and as gridded product.Basin-average ice-mass changes are obtained using the inversion procedure based on a forward modelling approach as described in Sasgen et al. (2013) for the AIS and Sasgen et al. (2012) for the GIS.Gridded ice-mass changes are provided at polar-stereographic grids with a grid spacing of 50 x 50 km^2. The applied algorithm is based on tailored sensitivity kernels (Groh & Horwath, 2016), and has also been used to generate gravimetric mass balance products within the ESA Climate Change Initiative (CCI) projects for the AIS and the GIS.These Level-3 products are visualized at GFZ's web portal GravIS (http://gravis.gfz-potsdam.de).Link to data products: ftp://isdcftp.gfz-potsdam.de/grace/GravIS/GFZ/Level-3/ICE
    Keywords: Gravity Recovery And Climate Experiment (GRACE) ; GRACE Follow-on (GRACE-FO) ; Level-3 ; Mass ; Mass Transport ; Ice-mass Change ; Time Variable Gravity ; Antarctic Mass Balance ; Greenland Mass Balance ; Sea-level Change ; EARTH SCIENCE 〉 SOLID EARTH 〉 GRAVITY/GRAVITATIONAL FIELD ; Earth Observation Satellites 〉 NASA Earth System Science Pathfinder 〉 GRACE
    Language: English
    Type: Dataset , Dataset
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  • 9
    Call number: S 91.0021 ; S 91.0021 (48) ; S 91.0021 (47) ; S 91.0021 (50) ; S 91.0021 (49) ; S 91.0021 (51)
    Type of Medium: Series available for loan
    ISSN: 0340-4404
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
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  • 10
    Series available for loan
    Series available for loan
    Mainz : Ges.
    Call number: S 94.0081 ; S 94.0081 (56) ; S 94.0081 (57) ; S 94.0081 (59) ; S 94.0081 (58) ; S 94.0081 (60)
    Type of Medium: Series available for loan
    ISSN: 0542-1535
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Location: Lower compact magazine
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
    Branch Library: GFZ Library
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