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  • 2020-2024  (2)
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  • 1
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    Cambridge University Press (CUP)
    In:  EPIC3Journal of Glaciology, Cambridge University Press (CUP), 69(277), pp. 1138-1148, ISSN: 0022-1430
    Publication Date: 2023-11-16
    Description: Antarctica's ice shelves stabilize the ice sheet and, therefore, understanding processes affecting the mass budgets of ice shelves is important for estimating grounded ice loss. To study the ice shelf dynamics, we analyzed seismological and GNSS data from the Ekström Ice Shelf in Dronning Maud Land. We extracted probabilistic power spectral densities (PPSD) in the frequency band 3.4-6.8 Hz, typical of icequakes, from seismological data and observed pronounced signals in the PPSD with near 3 and 4 cycles per day (cpd) corresponding to tidal overharmonics, in addition to the main tidal constituents near 1 and 2 cpd. GNSS data reveal the same components in ice flow speed but not in vertical displacements. Generally, tide-induced grounding line migration modulates the flow velocity of an entire ice shelf. We find that this velocity modulation causes the increased icequake activity in the tidal overharmonics with 3 and 4 cpd in an ice shear zone where the flow velocity drops to nearly zero.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Publication Date: 2023-12-16
    Description: Microbial composition and diversity in marine sediments are shaped by environmental, biological, and anthropogenic processes operating at different scales. However, our understanding of benthic microbial biogeography remains limited. Here, we used 16S rDNA amplicon sequencing to characterize benthic microbiota in the North Sea from the top centimeter of 339 sediment samples. We utilized spatially explicit statistical models, to disentangle the effects of the different predictors, including bottom trawling intensity, a prevalent industrial fishing practice which heavily impacts benthic ecosystems. Fitted models demonstrate how the geographic interplay of different environmental and anthropogenic drivers shapes the diversity, structure and potential metabolism of benthic microbial communities. Sediment properties were the primary determinants, with diversity increasing with sediment permeability but also with mud content, highlighting different underlying processes. Additionally, diversity and structure varied with total organic matter content, temperature, bottom shear stress and bottom trawling. Changes in diversity associated with bottom trawling intensity were accompanied by shifts in predicted energy metabolism. Specifically, with increasing trawling intensity, we observed a transition toward more aerobic heterotrophic and less denitrifying predicted metabolism. Our findings provide first insights into benthic microbial biogeographic patterns on a large spatial scale and illustrate how anthropogenic activity such as bottom trawling may influence the distribution and abundances of microbes and potential metabolism at macroecological scales.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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