Alfred Wegener Institute for Polar and Marine Research
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Autonomous Rover Enables Radar Profiling of Ice-Fabric Properties in Antarctica
No full textA ground-penetrating radar is an extensively used
geophysical tool in cryosphere sciences (ice sheets and glaciers)
with sounding depths of several kilometers due to the small
radio-wave attenuation in ice sheets. The detection of the ice
thickness and internal ice stratigraphy with commercial radars
has become standard. However, there is still an observational gap
in determining dielectric and mechanical ice-fabric anisotropy
and basal properties using these systems. Recently, a groundbased
phase-coherent radar showed its potential to fill this
gap. However, this requires that the corresponding groundbased
radars cover profiles several tens of kilometers in length.
We address this challenge by modifying an autonomous rover to
collect phase-coherent, quad-polarimetric radar data geolocated
with real-time kinematic (RTK) positioning. In a proof-ofconcept
study in Antarctica, we demonstrate that this allows
the collection of quad-polarimetric data along a 23-km profile,
mapping anisotropic ice-fabric properties at <100-m intervals
across the transition of grounded to floating ice. This study
shows the possibility of collecting data that will refine ice-flow
models by providing missing rheological parameters. This work
also demonstrates the versatility of the autonomous ground
vehicle with its ability to tow more than 200-kg payload, with a
battery run time of over 6 h, and with a modular design that
enables future integration of different radars or other geophysical
sensors
Recent advances in recirculating aquaculture systems and role of microalgae to close system loop
Get PDFIn recirculating aquaculture systems (RAS), waste management of nutrient-rich byproducts accounts for 30–50% of the whole production costs. Integrating microalgae into RAS offers complementary solutions for transforming waste streams into valuable co-products. This review aims to provide an overview of recent advances in microalgae application to enhance RAS performance and derive value from all waste streams by using RAS effluents as microalgal nutrient sources. Aquaculture solid waste can be converted by hydrothermal liquefaction (HTL), then the resultant aqueous phase of HTL can be used for microalgae cultivation. In addition, microalgae generate the required oxygen while sequestering carbon dioxide. The review suggests a novel integrated system focusing on oxygenation and carbon dioxide capture along with recent technological developments concerning efficient microalgae cultivation and nutrient recovery techniques. In such system, microalgae-based biorefineries provide environmentally-conscious and economically-viable pathways for enhanced RAS performance and conversion of effluents into high-value products
Brief communication: Testing a portable Bullard-type temperature lance confirms highly spatially heterogeneous sediment temperatures under shallow bodies of water in the Arctic
Get PDFThe thermal regime in the sediment column below shallow bodies of water in Arctic permafrost controls benthic habitats and permafrost stability. We present a robust, portable device that measures detailed temperature–depth profiles of the near-surface sediments in less than 1 h. Test campaigns in the Canadian Arctic and on Svalbard have demonstrated its utility in a range of environments during winter and summer. Measured temperatures were spatially heterogeneous, even within single bodies of water. We observed the broadest temperature range in water less than 1 m deep, a zone that is not captured by single measurements in deeper water
Anaerobic hexadecane degradation by a thermophilic Hadarchaeon from Guaymas Basin
Get PDFHadarchaeota inhabit subsurface and hydrothermally heated environments, but previous to this study, they had not been cultured. Based on metagenome-assembled genomes, most Hadarchaeota are heterotrophs that grow on sugars and amino acids, or oxidize carbon monoxide or reduce nitrite to ammonium. A few other metagenome-assembled genomes encode alkyl-coenzyme M reductases (Acrs), β-oxidation, and Wood-Ljungdahl pathways, pointing toward multicarbon alkane metabolism. To identify the organisms involved in thermophilic oil degradation, we established anaerobic sulfate-reducing hexadecane-degrading cultures from hydrothermally heated sediments of the Guaymas Basin. Cultures at 70?C were enriched in one Hadarchaeon that we propose as Candidatus Cerberiarchaeum oleivorans. Genomic and chemical analyses indicate that Ca. C. oleivorans uses an Acr to activate hexadecane to hexadecyl-coenzyme M. A β-oxidation pathway and a tetrahydromethanopterin methyl branch Wood-Ljungdahl (mWL) pathway allow the complete oxidation of hexadecane to CO2. Our results suggest a syntrophic lifestyle with sulfate reducers, as Ca. C. oleivorans lacks a sulfate respiration pathway. Comparative genomics show that Acr, mWL, and β-oxidation are restricted to one family of Hadarchaeota, which we propose as Ca. Cerberiarchaeaceae. Phylogenetic analyses further indicate that the mWL pathway is basal to all Hadarchaeota. By contrast, the carbon monoxide dehydrogenase/acetyl-coenzyme A synthase complex in Ca. Cerberiarchaeaceae was horizontally acquired from Bathyarchaeia. The Acr and β-oxidation genes of Ca. Cerberiarchaeaceae are highly similar to those of other alkane-oxidizing archaea such as Ca. Methanoliparia and Ca. Helarchaeales. Our results support the use of Acrs in the degradation of petroleum alkanes and suggest a role of Hadarchaeota in oil-rich environments
CAPICE - Combined Analysis and Publication of Ice Sheet data
Get PDFComplex simulations, such as ice sheet modeling, do not just require computations on a HPC infrastructure to solve the ice sheet model itself. Rather, an ice sheet model relies on forcing data, which is often the output of other models, such as atmospheric data from climate models. This project aims to develop a workflow across different HPC infrastructures that allows for efficient data ingestion, a user-friendly framework, and the possibility of data publication. While the current focus is on ice sheet modeling, the developed workflow will be designed to be applicable to other model setups
New avenues for potentially seeking microbial responses to climate change beneath Antarctic ice shelves
Get PDFThe signs of climate change are undeniable, and the impact of these changes on ecosystem function heavily depends on the response of microbes that underpin the food web. Antarctic ice shelf is a massive mass of floating ice that extends from the continent into the ocean, exerting a profound influence on global carbon cycles. Beneath Antarctic ice shelves, marine ice stores valuable genetic information, where marine microbial communities before the industrial revolution are archived. Here, in this proof-of-concept, by employing a combination of single-cell technologiesand metagenomics, we have been able to sequence frozen microbial DNA (≈300 years old) stored in the marine ice core B15 collected from the Filchnner-Ronne Ice Shelf. Metagenomic data indicated that Proteobacteria and Thaumarchaeota (e.g., Nitrosopumilus spp.), followed by Actinobacteria (e.g., Actinomarinales), were abundant. Remarkably, our data allow us to “travel to the past” and calibrate genomic and genetic evolutionary changes for ecologically relevant microbes and functions, such as Nitrosopumilus spp., preserved in the marine ice (≈300 years old) with those collected recently in seawater under an ice shelf (year 2017). The evolutionary divergence for the ammonia monooxygenase gene amoA involved in chemolithoautotrophy was about 0.88 amino acid and 2.8 nucleotide substitution rate per 100 sites in a century, while the accumulated rate of genomic SNPs was 2,467 per 1 Mb of genome and 100 years. Whether these evolutionary changes remained constant over the last 300 years or accelerated during post-industrial periods remains an open question that will be further elucidated. IMPORTANCE Several efforts have been undertaken to predict the response of microbes under climate change, mainly based on short-term microcosm experiments under forced conditions. A common concern is that manipulative experiments cannot properly simulate the response of microbes to climate change, which is a long-term evolutionary process. In this proof-of-concept study with a limited sample size, we demonstrate a novel approach yet to be fully explored in science for accessing genetic information from putative past marine microbes preserved under Antarctic ice shelves before the industrial revolution. This potentially allows us estimating evolutionary changes as exemplified in our study. We advocate for gathering a more comprehensive Antarctic marine ice core data sets across various periods and sites. Such a data set would enable the establishment of a robust baseline, facilitating a better assessment of the potential effects of climate change on key genetic signatures of microbes
Formation Mechanisms of Large‐Scale Folding in Greenland's Ice Sheet
Get PDFRadio‐echo sounding (RES) shows large‐scale englacial stratigraphic folds are ubiquitous in Greenland's ice sheet. However, there is no consensus yet on how these folds form. Here, we use the full‐Stokescode Underworld2 to simulate ice movements in three‐dimensional convergent flow, mainly considering iceanisotropy due to a crystallographic preferred orientation, vertical viscosity and density gradients in ice layers,and bedrock topography. Our simulated folds show complex patterns and are classified into: large‐scale folds(>100 m amplitude), small‐scale folds (<<100 m) and basal‐shear folds. The amplitudes of large‐scale foldstend to be at their maximum in the middle of the ice column or just below, in accordance with observations inRES data. We conclude that ice anisotropy amplifies the perturbations in ice layers (mainly due to bedrock topography) into large‐scale folds during flow. Density differences between the warm deep ice and cold iceabove may enhance fold amplification
The Arctic summer microbiome across Fram Strait: Depth, longitude, and substrate concentrations structure microbial diversity in the euphotic zone
Get PDFThe long-term dynamics of microbial communities across geographic, hydrographic, and biogeochemical gradients in the Arctic Ocean are largely unknown. To address this, we annually sampled polar, mixed, and Atlantic water masses of the Fram Strait (2015–2019; 5–100 m depth) to assess microbiome composition, substrate concentrations, and oceanographic parameters. Longitude and water depth were the major determinants (~30%) of microbial community variability. Bacterial alpha diversity was highest in lower-photic polar waters. Community composition shifted from west to east, with the prevalence of, for example, Dadabacteriales and Thiotrichales in Arctic- and Atlantic-influenced waters, respectively. Concentrations of dissolved organic carbon peaked in the western, compared to carbohydrates in the chlorophyll-maximum of eastern Fram Strait. Interannual differences due to the time of sampling, which varied between early (June 2016/2018) and late (September 2019) phytoplankton bloom stages, illustrated that phytoplankton composition and resulting availability of labile substrates influence bacterial dynamics. We identified 10 species clusters with stable environmental correlations, representing signature populations of distinct ecosystem states. In context with published metagenomic evidence, our microbial-biogeochemical inventory of a key Arctic region establishes a benchmark to assess ecosystem dynamics and the imprint of climate change
Eddy activity in the Arctic Ocean projected to surge in a warming world
Get PDFOcean eddies play a critical role in climate and marine life. In the rapidly warming Arctic, little is known about how ocean eddy activity will change because existing climate models cannot resolve Arctic Ocean mesoscale eddies. Here, by employing a next-generation global sea ice–ocean model with kilometre-scale horizontal resolution in the Arctic, we find a surge of eddy kinetic energy in the upper Arctic Ocean, tripling on average in a four-degree-warmer world. The driving mechanism behind this surge is an increase in eddy generation due to enhanced baroclinic instability. Despite the decline of sea ice, eddy killing (a process in which eddies are dampened by sea ice and winds) will not weaken in its annual mean effect in the considered warming scenario. Our study suggests the importance of adequately representing Arctic eddy activity in climate models for understanding the impacts of its increase on climate and ecosystems
Policy documents considering biodiversity, land use, and climate in the European Arctic reveal visible, hidden, and imagined nexus approaches
Get PDFThe Arctic is experiencing rapid and interlinked socio-environmental changes. Therefore, governance approaches that take the complex interactions between climate change, biodiversity loss, increasing land use pressures, and local livelihoods into account are needed: nexus approaches. However, an overview of whether and to what extent Arctic policies address these nexus elements in concert has been missing. Here we analyzed a large sample of publicly available assessment reports and policy documents from the terrestrial European Arctic. Our results show that, although nexus approaches are widely adopted in Arctic policy reporting, the emphasis varies among the governance levels, and documents underestimate certain interactions: local communities and traditional livelihoods are seldom seen as actors with agency and impact. Practical implementations were identified as potential advancements in Arctic governance: ecosystem-specific, technological, and authoritative solutions; co-production of knowledge; and adaptive co-management. Implementation of nexus approaches can promote more holistic environmental governance and guide cross-sectoral policies