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  • Articles  (48,425)
  • Springer Nature  (45,961)
  • American Geophysical Union (AGU)
  • Annual Reviews
  • 2020-2024  (430)
  • 1965-1969  (30,044)
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  • 1
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    Orbital- and millennial-scale Antarctic Circumpolar Current variability in Drake Passage over the past 140,000 years (2021)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 12(1), pp. 1-9, ISSN: 2041-1723
    Details
    Publication Date: 2023-06-21
    Description: The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological timescales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage in vicinity of the modern Polar Front over a complete glacial-interglacial cycle (i.e., the past 140,000 years), based on sediment grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with weakened current strength during glacials and a stronger circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennialscale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We infer that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations modulated Pacific-Atlantic water exchange via the “cold water route” and potentially affected the Atlantic Meridional Overturning Circulation and marine carbon storage.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    On the Damping Time Scale of EVP Sea Ice Dynamics (2021)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), 13(10), ISSN: 1942-2466
    Details
    Publication Date: 2023-06-21
    Description: We propose to make the damping time scale, which governs the decay of pseudo-elastic waves in the Elastic Viscous Plastic (EVP) sea-ice solvers, independent of the external time step and large enough to warrant numerical stability for a moderate number of internal time steps. A necessary condition is that the forcing on sea ice varies slowly on the damping time scale, in which case an EVP solution may still approach a Viscous Plastic one, but on a time scale longer than a single external time step. In this case, the EVP method becomes very close to the recently proposed modified EVP (mEVP) method in terms of stability and simulated behavior. In a simple test case dealing with sea ice breaking under the forcing of a moving cyclone, the EVP method with an enlarged damping time scale can simulate linear kinematic features which are very similar to those from the traditional EVP implementation, although a much smaller number of internal time steps is used. There is more difference in sea-ice thickness and linear kinematic features simulated in a realistic Arctic configuration between using the traditional and our suggested choices of EVP damping time scales, but it is minor considering model uncertainties associated with choices of many other parameters in sea-ice models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 3
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    The Role of Zooplankton Grazing and Nutrient Recycling for Global Ocean Biogeochemistry and Phytoplankton Phenology (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research Biogeosciences, American Geophysical Union (AGU), 127(10), ISSN: 2169-8953
    Details
    Publication Date: 2023-06-21
    Description: Zooplankton plays a notable role in ocean biogeochemical cycles. However, it is often simulated as one generic group and top closure term in ocean biogeochemical models. This study presents the description of three zooplankton functional types (zPFTs, micro-, meso- and macrozooplankton) in the ocean biogeochemical model FESOM-REcoM. In the presented model, microzooplankton is a fast-growing herbivore group, mesozooplankton is another major consumer of phytoplankton, and macrozooplankton is a slow-growing group with a low temperature optimum. Meso- and macrozooplankton produce fast-sinking fecal pellets. With three zPFTs, the annual mean zooplankton biomass increases threefold to 210 Tg C. The new food web structure leads to a 25% increase in net primary production and a 10% decrease in export production globally. Consequently, the export ratio decreases from 17% to 12% in the model. The description of three zPFTs reduces model mismatches with observed dissolved inorganic nitrogen and chlorophyll concentrations in the South Pacific and the Arctic Ocean, respectively. Representation of three zPFTs also strongly affects phytoplankton phenology: Fast nutrient recycling by zooplankton sustains higher chlorophyll concentrations in summer and autumn. Additional zooplankton grazing delays the start of the phytoplankton bloom by 3 weeks and controls the magnitude of the bloom peak in the Southern Ocean. As a result, the system switches from a light-controlled Sverdrup system to a dilution-controlled Behrenfeld system. Overall, the results suggest that representation of multiple zPFTs is important to capture underlying processes that may shape the response of ecosystems and ecosystem services to on-going and future environmental change in model projections.
    Repository Name: EPIC Alfred Wegener Institut
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  • 4
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    A Kinematic Kinetic Energy Backscatter Parametrization: From Implementation to Global Ocean Simulations (2020)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), 12(12), ISSN: 1942-2466
    Details
    Publication Date: 2023-06-21
    Description: Ocean models at eddy-permitting resolution are generally overdissipative, damping the intensity of the mesoscale eddy field. To reduce overdissipation, we propose a simplified, kinematic energy backscatter parametrization built into the viscosity operator in conjunction with a new flow-dependent coefficient of viscosity based on nearest neighbor velocity differences. The new scheme mitigates excessive dissipation of energy and improves global ocean simulations at eddy-permitting resolution. We find that kinematic backscatter substantially raises simulated eddy kinetic energy, similar to an alternative, previously proposed dynamic backscatter parametrization. While dynamic backscatter is scale aware and energetically more consistent, its implementation is more complex. Furthermore, it turns out to be computationally more expensive, as it applies, among other things, an additional prognostic subgrid energy equation. The kinematic backscatter proposed here, by contrast, comes at no additional computational cost, following the principle of simplicity. Our primary focus is the discretization on triangular unstructured meshes with cell placement of velocities (an analog of B-grids), as employed by the Finite-volumE Sea ice-Ocean Model (FESOM2). The kinematic backscatter scheme with the new viscosity coefficient is implemented in FESOM2 and tested in the simplified geometry of a zonally reentrant channel as well as in a global ocean simulation on a 1/4° mesh. This first version of the new kinematic backscatter needs to be tuned to the specific resolution regime of the simulation. However, the tuning relies on a single parameter, emphasizing the overall practicality of the approach.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
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    The 2020 European Seismic Hazard Model: Milestones and Lessons Learned (2023)
    Springer Nature
    Details
    Publication Date: 2023-01-18
    Description: The 2020 update of the European Seismic Hazard Model (ESHM20) is the most recent seismic hazard model of the Euro-Mediterranean region. It was built upon unified and homogenized datasets including earthquake catalogues, active faults, ground motion recordings and state-of-the-art modelling components, i.e. earthquake rates forecast and regionally variable ground motion characteristic models. ESHM20 replaces the 2013 European Seismic Hazard Model (ESHM13), and it is the first regional model to provide two informative hazard maps for the next update of the European Seismic Design Code (CEN EC8). ESHM20 is also one of the key components of the first publicly available seismic risk model for Europe. This chapter provides a short summary of ESHM20 by highlighting its main features and describing some lessons learned during the model’s development.
    Description: Published
    Description: 3-25
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: 4IT. Banche dati
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 6
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    Future Arctic Climate Change in CMIP6 Strikingly Intensified by NEMO‐Family Climate Models (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(4), ISSN: 0094-8276
    Details
    Publication Date: 2023-06-23
    Description: Climate change in the Arctic has substantial impacts on human life and ecosystems both within and beyond the Arctic. Our analysis of CMIP6 simulations shows that some climate models project much larger Arctic climate change than other models, including changes in sea ice, ocean mixed layer, air-sea heat flux, and surface air temperature in wintertime. In particular, dramatic enhancement of Arctic Ocean convection down to a few hundred meters is projected in these models but not in others. Interestingly, these models employ the same ocean model family (NEMO) while the choice of models for the atmosphere and sea ice varies. The magnitude of Arctic climate change is proportional to the strength of the increase in poleward ocean heat transport, which is considerably higher in this group of models. Establishing the plausibility of this group of models with high Arctic climate sensitivity to anthropogenic forcing is imperative given the implied ramifications.
    Repository Name: EPIC Alfred Wegener Institut
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  • 7
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    Sea‐Ice Forecasts With an Upgraded AWI Coupled Prediction System (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), 14(12), ISSN: 1942-2466
    Details
    Publication Date: 2023-06-23
    Description: A new version of the AWI Coupled Prediction System is developed based on the Alfred Wegener Institute Climate Model v3.0. Both the ocean and the atmosphere models are upgraded or replaced, reducing the computation time by a factor of 5 at a given resolution. This allowed us to increase the ensemble size from 12 to 30, maintaining a similar resolution in both model components. The online coupled data assimilation scheme now additionally utilizes sea-surface salinity and sea-level anomaly as well as temperature and salinity profile observations. Results from the data assimilation demonstrate that the sea-ice and ocean states are reasonably constrained. In particular, the temperature and salinity profile assimilation has mitigated systematic errors in the deeper ocean, although issues remain over polar regions where strong atmosphere-ocean-ice interaction occurs. One-year-long sea-ice forecasts initialized on 1 January, 1 April, 1 July and 1 October from 2003 to 2019 are described. To correct systematic forecast errors, sea-ice concentration from 2011 to 2019 is calibrated by trend-adjusted quantile mapping using the preceding forecasts from 2003 to 2010. The sea-ice edge raw forecast skill is within the range of operational global subseasonal-to-seasonal forecast systems, outperforming a climatological benchmark for about 2 weeks in the Arctic and about 3 weeks in the Antarctic. The calibration is much more effective in the Arctic: Calibrated sea-ice edge forecasts outperform climatology for about 45 days in the Arctic but only 27 days in the Antarctic. Both the raw and the calibrated forecast skill exhibit strong seasonal variations.
    Repository Name: EPIC Alfred Wegener Institut
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  • 8
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    Turbulent heat exchange over polar leads revisited: A large eddy simulation study (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), ISSN: 2169-897X
    Details
    Publication Date: 2023-06-23
    Description: Sea ice leads play an important role in energy exchange between the ocean and atmosphere in polar regions, and therefore must be considered in weather and climate models. As sea ice leads are not explicitly resolved in such models, lead-averaged surface heat flux is of considerable interest for the parameterization of energy exchange. Measurements and numerical studies have established that the lead-averaged surface heat flux depends not only on meteorological parameters, but also on lead width. Nonetheless, few studies to date have investigated the dependency of surface heat flux on lead width. Most findings on that dependency are based on observations with lead widths smaller than a few hundred meters, but leads can have widths from a few meters to several kilometers. In this parameter study, we present the results of three series of large-eddy simulations of turbulent exchange processes above leads. We varied the lead width and air temperature, as well as the roughness length. As this study focused on conditions without background wind, ice-breeze circulation occurred, and was the main driver of the adjustment of surface heat flux. A previous large-eddy simulation study with uncommonly large roughness length found that lead-averaged surface heat flux exhibited a distinct maximum at lead widths of about 3 km, while our results show the largest heat fluxes for the smallest leads simulated (lead width of 50 m). At more realistic roughness lengths, we observed monotonously increasing heat fluxes with increasing lead width. Further, new scaling laws for the ice-breeze circulation are proposed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 9
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    Impact of Cyclonic Wind Anomalies Caused by Massive Winter Sea Ice Retreat in the Barents Sea on Atlantic Water Transport Toward the Arctic: A Model Study (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research - Oceans, American Geophysical Union (AGU), 128(3), ISSN: 2169-9275
    Details
    Publication Date: 2023-06-23
    Description: The Arctic is warming much faster than the global average. This is known as Arctic Amplification and is caused by feedbacks in the local climate system. In this study, we explore a previously proposed hypothesis that an associated wind feedback in the Barents Sea could play an important role by increasing the warm water inflow into the Barents Sea. We find that the strong recent decrease in Barents Sea winter sea ice cover causes enhanced ocean-atmosphere heat flux and a local air temperature increase, thus a reduction in sea level pressure and a local cyclonic wind anomaly with eastward winds in the Barents Sea Opening. By investigating various reanalysis products and performing high-resolution perturbation experiments with the ocean and sea ice model FESOM2.1, we studied the impact of cyclonic atmospheric circulation changes on the warm Atlantic Water import into the Arctic via the Barents Sea and Fram Strait. We found that the observed wind changes do not significantly affect the warm water transport into the Barents Sea, which rejects the wind-feedback hypothesis. At the same time, the cyclonic wind anomalies in the Barents Sea increase the amount of Atlantic Water recirculating westwards in Fram Strait by a downslope shift of the West Spitsbergen Current, and thus reduce Atlantic Water reaching the Arctic basin via Fram Strait. The resulting warm-water anomaly in the Greenland Sea Gyre drives a local anticyclonic circulation anomaly.
    Repository Name: EPIC Alfred Wegener Institut
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  • 10
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    Evaluation of Surface Layer Stability Functions and Their Extension to First Order Turbulent Closures for Weakly and Strongly Stratified Stable Boundary Layer (2023)
    Springer Nature
    In:  EPIC3Boundary-Layer Meteorology, Springer Nature, ISSN: 0006-8314
    Details
    Publication Date: 2023-04-25
    Description: In this study, we utilize a generalization of Monin–Obukhov similarity theory to construct first order turbulent closures for single-column models of the atmospheric boundary layer (ABL). A set of widely used universal functions for dimensionless gradients is evaluated. Two test cases based on Large-Eddy Simulations (LES) experimental setups are considered – weakly stable ABL (GABLS1; Beare et al. in Bound Layer Meteorol 118(2):247–272,2006), and very strongly stratified ABL (van der Linden et al. in Bound Layer Meteorol 173(2):165–192, 2019). The comparison shows that approximations obtained using a linear dimensionless velocity gradient tend to match the LES data more closely. In particular, the EFB (Energy- and Flux- Budget) closure proposed by Zilitinkevich et al. (Bound Layer Meteorol 146(3):341–373, 2013) has the best performance for the tests considered here. We also test surface layer “bulk formulas” based on these universal functions. The same LES data are utilized for comparison. The setup showcases the behavior of surface scheme, when one assumes that the velocity and temperature profiles in ABL are represented correctly. The advantages and disadvantages of different surface schemes are revealed.
    Repository Name: EPIC Alfred Wegener Institut
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  • 11
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    Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), pp. 2653-2653, ISSN: 2041-1723
    Details
    Publication Date: 2023-10-19
    Description: The dynamic mass loss of ice sheets constitutes one of the biggest uncertainties in projections of ice-sheet evolution. One central, understudied aspect of ice flow is how the bulk orientation of the crystal orientation fabric translates to the mechanical anisotropy of ice. Here we show the spatial distribution of the depth-averaged horizontal anisotropy and corresponding directional flow-enhancement factors covering a large area of the Northeast Greenland Ice Stream onset. Our results are based on airborne and ground-based radar surveys, ice-core observations, and numerical ice-flow modelling. They show a strong spatial variability of the horizontal anisotropy and a rapid crystal reorganisation on the order of hundreds of years coinciding with the ice-stream geometry. Compared to isotropic ice, parts of the ice stream are found to be more than one order of magnitude harder for along-flow extension/compression while the shear margins are potentially softened by a factor of two for horizontal-shear deformation.
    Repository Name: EPIC Alfred Wegener Institut
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  • 12
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    Mining questions of ‘what’ and ‘who’: deepening discussions of the seabed for future policy and governance (2022)
    Springer Nature
    In:  EPIC3Maritime Studies, Springer Nature, 21(3), pp. 327-338, ISSN: 1872-7859
    Details
    Publication Date: 2023-10-30
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉In spite of a proliferation of academic and policy-oriented interest in deep sea mining (DSM), this paper argues that two underlying questions remain underexplored. The first relates to 〈jats:italic〉what〈/jats:italic〉 exactly the seabed 〈jats:italic〉is〈/jats:italic〉; the second to 〈jats:italic〉who〈/jats:italic〉 the stakeholders 〈jats:italic〉are〈/jats:italic〉. It is argued that a greater interrogation of how the seabed is defined and understood, and a deeper consideration of how stakeholders are identified and the politics of their inclusion, is crucial to the enactment of policy and planning techniques. Through the analysis of current regulations to govern DSM in both national and international jurisdictions, this paper critically examines these seemingly banal but vital questions in different contexts. It is contended that most regulations are ‘fuzzy’ when it comes to addressing these questions, with the result that different understandings of the seabed and the implications of mining are ignored and that who stakeholders are and how they are defined causes many relevant voices to be unheard. It is argued, therefore, that it is imperative to address these often-overlooked questions directly in order to inform future seabed policy and governance.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 13
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    Principles for transformative ocean governance (2023)
    Springer Nature
    In:  EPIC3Nature Sustainability, Springer Nature, pp. 1-13, ISSN: 2398-9629
    Details
    Publication Date: 2023-10-30
    Description: With a focus on oceans, we collaborated across ecological, social and legal disciplines to respond to the United Nations call for transformation in the ‘2030 Agenda for Sustainable Development’. We developed a set of 13 principles that strategically and critically connect transformative ocean research to transformative ocean governance (complementing the UN Decade for Ocean Science). We used a rigorous, iterative and transparent consensus-building approach to define the principles, which can interact in supporting, neutral or sometimes conflicting ways. We recommend that the principles could be applied as a comprehensive set and discuss how to learn from their interactions, particularly those that reveal hidden tensions. The principles can bring and keep together partnerships for innovative ocean action. This action must respond to the many calls to reform current ocean-use practices which are based on economic growth models that have perpetuated inequities and fuelled conflict and environmental decline.
    Repository Name: EPIC Alfred Wegener Institut
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  • 14
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    The impact of salps (Salpa thompsoni) on the Antarctic krill population (Euphausia superba): an individual-based modelling study (2023)
    Springer Nature
    In:  EPIC3Ecological Processes, Springer Nature, 12(1), pp. 50-50, ISSN: 2192-1709
    Details
    Publication Date: 2023-11-23
    Description: Krill (Euphausia superba) and salps (Salpa thompsoni) are key macrozooplankton grazers in the Southern Ocean ecosystem. However, due to differing habitat requirements, both species previously exhibited little spatial overlap. With ongoing climate change-induced seawater temperature increase and regional sea ice loss, salps can now extend their spatial distribution into historically krill-dominated areas and increase rapidly due to asexual reproduction when environmental conditions are favorable. Understanding the potential effects on krill is crucial, since krill is a species of exceptional trophic significance in the Southern Ocean food web. Negative impacts on krill could trigger cascading effects on its predators and prey. To address this question, we combined two individual-based models on salps and krill, which describe the whole life cycle of salp individuals and the dynamic energy budget of individual krill. The resulting new model PEKRIS (PErformance of KRIll vs. Salps) simulates a krill population for 100 years under varying chlorophyll-a concentrations in the presence or absence of salps. All of the investigated krill population properties (abundance, mean length, and yearly egg production) were significantly impacted by the presence of salps. On the other hand, salp density was not impacted if krill were present. The medians of krill population properties deviated during variable maximum chlorophyll-a density per year when salps were introduced by − 99.9% (− 234 individuals per 1000 m3) for krill density, − 100% (− 22,062 eggs per 1000 m3) for krill eggs and − 0.9% (− 0.3 mm) for mean length of krill. If both species compete for the same food resource in a closed space, salps seem to inhibit krill populations. Further simulation studies should investigate whether this effect prevails if different phytoplankton sizes and consumption preferences of krill are implemented. Furthermore, direct predation of the two species or consumption of krill fecal pellets by salps could change the impact size of the food competition.
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
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    The Impacts of Optimizing Model‐Dependent Parameters on the Antarctic Sea Ice Data Assimilation (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(22), ISSN: 0094-8276
    Details
    Publication Date: 2023-11-25
    Description: Given the role played by the historical and extensive coverage of sea ice concentration (SIC) observations in reconstructing the long‐term variability of Antarctic sea ice, and the limited attention given to model‐dependent parameters in current sea ice data assimilation studies, this study focuses on enhancing the performance of the Data Assimilation System for the Southern Ocean in assimilating SIC through optimizing the localization and observation error estimate, and two assimilation experiments were conducted from 1979 to 2018. By comparing the results with the sea ice extent of the Southern Ocean and the sea ice thickness in the Weddell Sea, it becomes evident that the experiment with optimizations outperforms that without optimizations due to achieving more reasonable error estimates. Investigating uncertainties of the sea ice volume anomaly modeling reveals the importance of the sea ice‐ocean interaction in the SIC assimilation, implying the necessity of assimilating more oceanic and sea‐ice observations.
    Repository Name: EPIC Alfred Wegener Institut
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  • 16
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    Metagenome-assembled genomes reveal greatly expanded taxonomic and functional diversification of the abundant marine Roseobacter RCA cluster (2023)
    Springer Nature
    In:  EPIC3Microbiome, Springer Nature, ISSN: 2049-2618
    Details
    Publication Date: 2023-11-25
    Description: Background The RCA (Roseobacter clade affiliated) cluster belongs to the family Roseobacteracea and represents a major Roseobacter lineage in temperate to polar oceans. Despite its prevalence and abundance, only a few genomes and one described species, Planktomarina temperata, exist. To gain more insights into our limited understanding of this cluster and its taxonomic and functional diversity and biogeography, we screened metagenomic datasets from the global oceans and reconstructed metagenome-assembled genomes (MAG) affiliated to this cluster. Results The total of 82 MAGs, plus five genomes of isolates, reveal an unexpected diversity and novel insights into the genomic features, the functional diversity, and greatly refined biogeographic patterns of the RCA cluster. This cluster is subdivided into three genera: Planktomarina, Pseudoplanktomarina, and the most deeply branching Candidatus Paraplanktomarina. Six of the eight Planktomarina species have larger genome sizes (2.44–3.12 Mbp) and higher G + C contents (46.36–53.70%) than the four Pseudoplanktomarina species (2.26–2.72 Mbp, 42.22–43.72 G + C%). Cand. Paraplanktomarina is represented only by one species with a genome size of 2.40 Mbp and a G + C content of 45.85%. Three novel species of the genera Planktomarina and Pseudoplanktomarina are validly described according to the SeqCode nomenclature for prokaryotic genomes. Aerobic anoxygenic photosynthesis (AAP) is encoded in three Planktomarina species. Unexpectedly, proteorhodopsin (PR) is encoded in the other Planktomarina and all Pseudoplanktomarina species, suggesting that this light-driven proton pump is the most important mode of acquiring complementary energy of the RCA cluster. The Pseudoplanktomarina species exhibit differences in functional traits compared to Planktomarina species and adaptations to more resource-limited conditions. An assessment of the global biogeography of the different species greatly expands the range of occurrence and shows that the different species exhibit distinct biogeographic patterns. They partially reflect the genomic features of the species. Conclusions Our detailed MAG-based analyses shed new light on the diversification, environmental adaptation, and global biogeography of a major lineage of pelagic bacteria. The taxonomic delineation and validation by the SeqCode nomenclature of prominent genera and species of the RCA cluster may be a promising way for a refined taxonomic identification of major prokaryotic lineages and sublineages in marine and other prokaryotic communities assessed by metagenomics approaches.
    Repository Name: EPIC Alfred Wegener Institut
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  • 17
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    Snow‐Atmosphere Humidity Exchange at the Ice Sheet Surface Alters Annual Mean Climate Signals in Ice Core Records (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(20), ISSN: 0094-8276
    Details
    Publication Date: 2023-11-20
    Description: Surface processes alter the water stable isotope signal of the surface snow after deposition. However, it remains an open question to which extent surface post-depositional processes should be considered when inferring past climate information from ice core records. Here, we present simulations for the Greenland Ice Sheet, combining outputs from two climate models with an isotope-enabled snowpack model. We show that surface vapor exchange and associated fractionation imprint a climate signal into the firn, resulting in an increase in the annual mean value of δ18O by +2.3‰ and a reduction in d-excess by −6.3‰. Further, implementing isotopic fractionation during surface vapor exchange improves the representation of the observed seasonal amplitude in δ18O from 65.0% to 100.2%. Our results stress that surface vapor exchange is important in the climate proxy signal formation and needs consideration when interpreting ice core climate records.
    Repository Name: EPIC Alfred Wegener Institut
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  • 18
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    Preconditioning of Summer Melt Ponds From Winter Sea Ice Surface Temperature (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(4), ISSN: 0094-8276
    Details
    Publication Date: 2023-02-23
    Description: Comparing helicopter-borne surface temperature maps in winter and optical orthomosaics in summer from the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition, we find a strong geometric correlation between warm anomalies in winter and melt pond location the following summer. Warm anomalies are associated with thinner snow and ice, that is, surface depression and refrozen leads, that allow for water accumulation during melt. Warm surface temperature anomalies in January were 0.3–2.5 K warmer on sea ice that later formed melt ponds. A one-dimensional steady-state thermodynamic model shows that the observed surface temperature differences are in line with the observed ice thickness and snow depth. We demonstrate the potential of seasonal prediction of summer melt pond location and coverage from winter surface temperature observations. A threshold-based classification achieves a correct classification for 41% of the melt ponds.
    Repository Name: EPIC Alfred Wegener Institut
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    Magma reservoir growth and ground deformation preceding the 79 CE Plinian eruption of Vesuvius (2023)
    Springer Nature
    Details
    Publication Date: 2023-07-03
    Description: The 79 CE eruption of Vesuvius is the first documented Plinian eruption, also famous for the archaeological ruins of Pompeii and Herculaneum. Although much is known regarding the eruption dynamics and magma reservoir, little is known about the reservoir shape and growth, and related ground deformation. Numerical modelling by Finite Element Method was carried out, aimed at simulating the reservoir growth and ground deformation with respect to the reservoir shape (prolate, spherical, oblate) and magma overpressure. The modelling was tuned with volcanological, petrological and paleoenvironmental ground deformation con straints. Results indicate that the highest magma overpressure is achieved considering a prolate reservoir, making it as the most likely shape that led to eruption. Similar deformations but lower overpressures are obtained considering spherical and oblate reservoirs. These results demonstrate that ground deformation may not be indicative of eruption probability, style/size, and this has direct implications on surveillance at active explosive volcanoes
    Description: Published
    Description: 211
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: Pompeii eruption ; ground deformation ; surveillance ; magma reservoir
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Omnipresent authigenic calcite distorts Arctic radiocarbon chronology (2023)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 4(1), pp. 136-136, ISSN: 2662-4435
    Details
    Publication Date: 2023-09-06
    Description: As calcareous foraminifera precipitate their shells from the surrounding water mass, they are the basis of most marine radiocarbon chronologies and paleo-proxies. Nevertheless, post-mortem alteration of shells, especially addition of authigenic calcite, impact proxy records. In the Arctic Ocean, authigenic calcite overgrowth on foraminifera has been attributed to hydrocarbon release, with a single report on 13C-enriched authigenic calcite, indicating a different carbon source. Here, we use comparative radiocarbon, carbon and oxygen isotope measurements to show that this 13C-enriched authigenic calcite impacts a large proportion of Holocene and the majority of last glacial planktonic foraminifera in the Arctic Basin. This authigenic precipitated calcite is 14C-depleted, so overgrowth results in invariably older 14C-ages. We show that, in comparison with published data, the true chronology of Arctic basin sediments can deviate by more than 10,000 years in critical parts of the last deglaciation and that stable oxygen and carbon isotopes, as likely all calcite-based proxy-records are affected with potential implications for paleoclimate models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 21
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    Atmospheric CO2 concentration based on boron isotopes versus simulations of the global carbon cycle during the Plio‐Pleistocene (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union (AGU), 38, 22 p., pp. e2022PA004439-e2022PA004439, ISSN: 2572-4517
    Details
    Publication Date: 2023-08-30
    Description: Atmospheric carbon dioxide concentrations (pCO2) beyond ice core records have been reconstructed from δ11B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio-Pleistocene to evaluate the assumptions leading to these numbers. During glacials times, simulated atmospheric pCO2 was unequilibrated with pCO2 in the equatorial surface ocean by up to 35 ppm while the δ11B-based approaches assume unchanged (quasi)equilibrium between both. In the Pliocene, δ11B-based estimates of surface ocean pH are lower in the Pacific than in the Atlantic resulting in higher calculated pCO2. This offset in pH between ocean basins is not supported by models. To calculate pCO2 in surface waters out of the δ11B-based pH some assumptions on either total alkalinity or dissolved inorganic carbon are necessary. However, the assumed values of these under-constrained variables were according to my results partly inconsistent with chemically possible combinations within the marine carbonate system. The model results show glacial/interglacial variability in total alkalinity of the order of 100 μmol/kg, which is rarely applied to proxy reconstructions. Simulated atmospheric pCO2 is tightly (r2 〉 0.9) related to equatorial surface-ocean pH, which can be used for consistency checks. Long-term trends in volcanic CO2 outgassing and the strength of the continental weathering fluxes are still unconstrained, allowing for a wide range of possible atmospheric pCO2 across the Plio-Pleistocene. Nevertheless, this carbon cycle analysis suggests that reported atmospheric pCO2 above 500 ppm in the Pliocene might, for various reasons, need to be revised to smaller numbers.
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  • 22
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    Stable Carbon Isotope Signature of Methane Released From Phytoplankton (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(12), ISSN: 0094-8276
    Details
    Publication Date: 2023-09-01
    Description: Aquatic ecosystems play an important role in global methane cycling and many field studies have reported methane supersaturation in the oxic surface mixed layer (SML) of the ocean and in the epilimnion of lakes. The origin of methane formed under oxic condition is hotly debated and several pathways have recently been offered to explain the “methane paradox.” In this context, stable isotope measurements have been applied to constrain methane sources in supersaturated oxygenated waters. Here we present stable carbon isotope signatures for six widespread marine phytoplankton species, three haptophyte algae and three cyanobacteria, incubated under laboratory conditions. The observed isotopic patterns implicate that methane formed by phytoplankton might be clearly distinguished from methane produced by methanogenic archaea. Comparing results from phytoplankton experiments with isotopic data from field measurements, suggests that algal and cyanobacterial populations may contribute substantially to methane formation observed in the SML of oceans and lakes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 23
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    Teardrop and Parabolic Lens Yield Curves for Viscous‐Plastic Sea Ice Models: New Constitutive Equations and Failure Angles (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Advances in Modeling Earth Systems, American Geophysical Union (AGU), 15(9), ISSN: 1942-2466
    Details
    Publication Date: 2023-09-04
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Most viscous‐plastic sea ice models use the elliptical yield curve. This yield curve has a fundamental flaw: it excludes acute angles between deformation features at high resolution. Conceptually, the teardrop (TD) and parabolic lens (PL) yield curves offer an attractive alternative. These yield curves feature a non‐symmetrical shape, a Coulombic behavior for the low‐medium compressive stress, and a continuous transition to the ridging‐dominant mode, but their published formulation leads to negative or zero bulk and shear viscosities and, consequently, poor numerical convergence with stress states at times outside the yield curve. These issues are a consequence of the original assumption that the constitutive equations of the commonly used elliptical yield curve are also applicable to non‐symmetrical yield curves and yield curves with tensile strength. We derive a corrected formulation for the constitutive relations of the TD and PL yield curves. Results from simple uni‐axial loading experiments show that with the new formulation the numerical convergence of the solver improves and much smaller nonlinear residuals after a smaller number of total solver iterations can be reached, resulting in significant improvements in numerical efficiency and representation of the stress and deformation fields. The TD and PL yield curves lead to smaller angles of failure that better agree with observations. They are promising candidates to replace the elliptical yield curve in high‐resolution pan‐Arctic sea ice simulations.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 24
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    Trends and variability in the ocean carbon sink (2023)
    Springer Nature
    In:  EPIC3Nature Reviews Earth & Environment, Springer Nature, 4(2), pp. 119-134, ISSN: 2662-138X
    Details
    Publication Date: 2023-09-04
    Description: The ocean has absorbed 25 ± 2% of the total anthropogenic CO2 emissions from the early 1960s to the late 2010s, with rates more than tripling over this period and with a mean uptake of –2.7 ± 0.3 Pg C year–1 for the period 1990 through 2019. This growth of the ocean sink matches expectations based on the increase in atmospheric CO2, but research has shown that the sink is more variable than long assumed. In this Review, we discuss trends and variations in the ocean carbon sink. The sink stagnated during the 1990s with rates hovering around –2 Pg C year–1, but strengthened again after approximately 2000, taking up around –3 Pg C year–1 for 2010–2019. The most conspicuous changes in uptake occurred in the high latitudes, especially the Southern Ocean. These variations are caused by changes in weather and climate, but a volcanic eruption-induced reduction in the atmospheric CO2 growth rate and the associated global cooling contributed as well. Understanding the variability of the ocean carbon sink is crucial for policy making and projecting its future evolution, especially in the context of the UN Framework Convention on Climate Change stocktaking activities and the deployment of CO2 removal methods. This goal will require a global-level effort to sustain and expand the current observational networks and to better integrate these observations with models.
    Repository Name: EPIC Alfred Wegener Institut
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  • 25
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    Antarctic Sedimentary Basins and Their Influence on Ice‐Sheet Dynamics (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Reviews of Geophysics, American Geophysical Union (AGU), 61(3), ISSN: 8755-1209
    Details
    Publication Date: 2023-10-09
    Description: Knowledge of Antarctica's sedimentary basins builds our understanding of the coupled evolution of tectonics, ice, ocean, and climate. Sedimentary basins have properties distinct from basement-dominated regions that impact ice-sheet dynamics, potentially influencing future ice-sheet change. Despite their importance, our knowledge of Antarctic sedimentary basins is restricted. Remoteness, the harsh environment, the overlying ice sheet, ice shelves, and sea ice all make fieldwork challenging. Nonetheless, in the past decade the geophysics community has made great progress in internationally coordinated data collection and compilation with parallel advances in data processing and analysis supporting a new insight into Antarctica's subglacial environment. Here, we summarize recent progress in understanding Antarctica's sedimentary basins. We review advances in the technical capability of radar, potential fields, seismic, and electromagnetic techniques to detect and characterize basins beneath ice and advances in integrated multi-data interpretation including machine-learning approaches. These new capabilities permit a continent-wide mapping of Antarctica's sedimentary basins and their characteristics, aiding definition of the tectonic development of the continent. Crucially, Antarctica's sedimentary basins interact with the overlying ice sheet through dynamic feedbacks that have the potential to contribute to rapid ice-sheet change. Looking ahead, future research directions include techniques to increase data coverage within logistical constraints, and resolving major knowledge gaps, including insufficient sampling of the ice-sheet bed and poor definition of subglacial basin structure and stratigraphy. Translating the knowledge of sedimentary basin processes into ice-sheet modeling studies is critical to underpin better capacity to predict future change.
    Repository Name: EPIC Alfred Wegener Institut
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  • 26
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    The contribution of Geomatics to increase safety and security in ports (2021)
    Springer Nature
    Details
    Publication Date: 2023-10-03
    Description: In this paper, the advantages achievable from the use of two prototype systems that are being developed to increase safety and security in ports are shown. Both systems start by monitoring environmental parameters in harbors, and then process data acquired. The first system has been conceived to be helpful to port communities (port authorities, pilots) to optimize harbor waterside management (ship’s navigation and cargo, dock performances, boat moorings, refloating of stranded ships, water quality control). By monitoring and processing sea level and atmospheric pressure in port areas, it can help port communities, e.g., to choose the best time when a ship with a certain draft can enter or leave a harbor, or to plan the best route inside the basin for that vessel (port safety). The second system, instead, has been designed for port protection purposes: by monitoring and processing the Earth’s magnetic field below the sea surface in harbors (where the natural field is disturbed by a high artificial component), it is able to detect the possible presence of intruders (e.g., divers) swimming underwater in prohibited areas (port security). Here, the results of monitoring and processing activities of the two systems performed in Livorno and La Spezia harbors are shown (Italy). The processing procedures and the graphical interfaces of the systems are based on applications under development by the research team the author belongs to, by using C# and C++ languages; Matlab environment has been employed for simulations.
    Description: Published
    Description: 647–658
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 3A. Geofisica marina e osservazioni multiparametriche a fondo mare
    Description: 4A. Oceanografia e clima
    Description: 7SR AMBIENTE – Servizi e ricerca per la società
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    On their way to the north: larval performance of Hemigrapsus sanguineus invasive to the European coast—a comparison with the native European population of Carcinus maenas (2023)
    Springer Nature
    In:  EPIC3Biological Invasions, Springer Nature, pp. 1-18, ISSN: 1387-3547
    Details
    Publication Date: 2023-08-09
    Description: The Asian shore crab Hemigrapsus sanguineus has become invasive in North Europe and it co-occurs and competes with the native European shore crab Carcinus maenas. Both species develop through a feeding and dispersive larval phase characterised by several zoeal and a settling megalopa stage. Larvae of marine crabs are vulnerable to food limitation and warming has the potential to exacerbate the negative effects of food limitation on survival and growth. We quantified the combined effects of temperature and food limitation on larval performance (survival and growth) of H. sanguineus and we compared our results with those reported on performance of C. maenas larvae, under the same experimental design and methodology. Larvae from four females of H. sanguineus collected on Helgoland (North Sea) were experimentally reared from hatching to megalopa, at four temperatures (range 15–24 °C) and two food conditions (permanent vs. daily limited access to food). Larval survival of H. sanguineus was low at 15 °C and increased with temperature, in contrast to the high survival reported for C. maenas larvae in the range 15–24 °C. Food limitation reduced survival and body mass of H. sanguineus larvae at all temperatures, but without evidence of the exacerbating effect caused by high temperatures and reported for C. maenas. By contrast, high temperature (24 °C) mitigated the negative effect of food limitation on body mass on H. sanguineus larvae. Advantages of H. sanguineus over C. maenas appear especially under the increased temperatures expected from climate change.
    Repository Name: EPIC Alfred Wegener Institut
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    Publisher Correction: Carbon dioxide sink in the Arctic Ocean from cross-shelf transport of dense Barents Sea water (2023)
    Springer Nature
    In:  EPIC3Nature Geoscience, Springer Nature, 16(2), pp. 189-189, ISSN: 1752-0894
    Details
    Publication Date: 2023-08-01
    Description: In the version of this article initially published, author Cora Hörstmann was wrongly listed with a second affiliation with the Department of Ecoscience–Applied Marine Ecology and Modelling, Aarhus University rather than the Mediterranean Institute of Oceanography (MIO), Marseille, France. Furthermore, references 83–97, now found in the Supplementary Tables caption, were wrongly cited in the Data Availability section. The errors have been corrected in the HTML and PDF versions of the article.
    Repository Name: EPIC Alfred Wegener Institut
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  • 29
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    Carbon dioxide sink in the Arctic Ocean from cross-shelf transport of dense Barents Sea water (2023)
    Springer Nature
    In:  EPIC3Nature Geoscience, Springer Nature, 16(1), pp. 82-88, ISSN: 1752-0894
    Details
    Publication Date: 2023-08-01
    Description: Large amounts of atmospheric carbon can be exported and retained in the deep sea on millennial time scales, buffering global warming. However, while the Barents Sea is one of the most biologically productive areas of the Arctic Ocean, carbon retention times were thought to be short. Here we present observations, complemented by numerical model simulations, that revealed a deep and widespread lateral injection of approximately 2.33 kt C d−1 from the Barents Sea shelf to some 1,200 m of the Nansen Basin, driven by Barents Sea Bottom Water transport. With increasing distance from the outflow region, the plume expanded and penetrated into even deeper waters and the sediment. The seasonally fluctuating but continuous injection increases the carbon sequestration of the Barents Sea by 1/3 and feeds the deep sea community of the Nansen Basin. Our findings combined with those from other outflow regions of carbon-rich polar dense waters highlight the importance of lateral injection as a global carbon sink. Resolving uncertainties around negative feedbacks of global warming due to sea ice decline will necessitate observation of changes in bottom water formation and biological productivity at a resolution high enough to quantify future deep carbon injection.
    Repository Name: EPIC Alfred Wegener Institut
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  • 30
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    Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation (2023)
    Springer Nature
    In:  EPIC3Scientific Reports, Springer Nature, 13(1), pp. 10281-, ISSN: 2045-2322
    Details
    Publication Date: 2023-08-03
    Description: Dissimilatory iron reduction (DIR) is suggested to be one of the earliest forms of microbial respiration. It plays an important role in the biogeochemical cycling of iron in modern and ancient sediments. Since microbial iron cycling is typically accompanied by iron isotope fractionation, stable iron isotopes are used as tracer for biological activity. Here we present iron isotope data for dissolved and sequentially extracted sedimentary iron pools from deep and hot subseafloor sediments retrieved in the Nankai Trough off Japan. Dissolved iron (Fe(II)aq) is isotopically light throughout the ferruginous sediment interval but some samples have exceptionally light isotope values. Such light values have never been reported in natural marine environments and cannot be solely attributed to DIR. We show that the light isotope values are best explained by a Rayleigh distillation model where Fe(II)aq is continuously removed from the pore water by adsorption onto iron (oxyhydr)oxide surfaces. While the microbially mediated Fe(II)aq release has ceased due to an increase in temperature beyond the threshold of mesophilic microorganisms, the abiotic adsorptive Fe(II)aq removal continued, leading to uniquely light isotope values. These findings have important implications for the interpretation of dissolved iron isotope data especially in deep subseafloor sediments.
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    Publisher Correction: Biodiversity, environmental drivers, and sustainability of the global deep-sea sponge microbiome (2022)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 13(1), pp. 6546-6546, ISSN: 2041-1723
    Details
    Publication Date: 2023-07-25
    Description: The original version of the Description of Additional Supplementary Files associated with this Article contained errors in the legends of Supplementary Data 5–8 and omitted legends for the Source Data. The HTML has been updated to include a corrected version of the Description of Additional Supplementary Files; the original incorrect version of this file can be found as Supplementary Information associated with this Correction.
    Repository Name: EPIC Alfred Wegener Institut
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  • 32
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    Satellite-observed strong subtropical ocean warming as an early signature of global warming (2023)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 4(1), 10 p., pp. 1-10, ISSN: 2662-4435
    Details
    Publication Date: 2023-06-02
    Description: Satellite observations covering the last four decades reveal an ocean warming pattern resembling the negative phase of the Pacific Decadal Oscillation. This pattern has therefore been widely interpreted as a manifestation of natural climate variability. Here, we re-examine the observed warming pattern and find that the predominant warming over the subtropical oceans, while mild warming or even cooling over the subpolar ocean, is dynamically consistent with the convergence and divergence of surface water. By comparison of observations, paleo-reconstructions, and model simulations, we propose that the observed warming pattern is likely a short-term transient response to the increased CO2 forcing, which only emerges during the early stage of anthropogenic warming. On centennial to millennial timescales, the subpolar ocean warming is expected to exceed the temporally dominant warming of the subtropical ocean. This delayed but amplified subpolar ocean warming has the potential to reshape the ocean-atmosphere circulation and threaten the stability of marine-terminating ice sheets.
    Repository Name: EPIC Alfred Wegener Institut
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  • 33
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    Reply to: No evidence of worsening Arctic springtime ozone losses over the 21st century (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), 4 p., pp. 1-4, ISSN: 2041-1723
    Details
    Publication Date: 2023-04-12
    Repository Name: EPIC Alfred Wegener Institut
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  • 34
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    Stable Barium Isotope Fractionation in Pore Waters of Estuarine Sediments (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geochemistry, Geophysics, Geosystems, American Geophysical Union (AGU), 24(6), ISSN: 1525-2027
    Details
    Publication Date: 2023-06-01
    Repository Name: EPIC Alfred Wegener Institut
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  • 35
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    TRACE ELEMENTS IN HIGH INCIDENCE AREAS OF MULTIPLE SCLEROSIS: A ROLE OF VOLCANOGENIC ASHES? (2023)
    Springer Nature
    Details
    Publication Date: 2023-02-07
    Description: Objective: To study the blood levels of selected trace elements (TE) in Multiple Sclerosis (MS) patients living in high-incidence cluster areas in the Etna volcano region. Methods: MS patients living in the province of Catania have been retrospectively enrolled among those followed by the Neurologic Clinic of the AOU Policlinico “G. Rodolico-San Marco” who had the disease onset between 2005 and 2020.Aserumsample was used for the determination of TE levels (As,Cd, Cr, Cu, Fe, Mg, Mn, Ni, Se, Zn). All the analyses have been conducted with an ICPMS with the standard addition technique, previous digestion of the samples with nitric acid. MS patients living the high incidence clusters were frequency matched with MS patients living outside the clusters. Comparisons of TE across the groups were conducted using the Mann-Whitney test. Results: A total of 86 (48 women; 55.8%) MS patients was recruited, with a mean age of 41.6±13.1 years, a mean disease duration of 2.0±2.6 years and a mean Expanded Disability Status Scale of 2.3±1.7. Of these patients, 40 belonged to high incidence clusters and 46 were outside the clusters. No differences were found in demographic characteristics between the groups. Concerning TE, we found a significant higher concentration of Mn in incluster patients (6.7±16.6 μg/L vs 2.5±5.9 μg/L). Discussion: Several environmental factors may modulate the pathogenesis of the disease, and among them TE play an important role. Our findings suggest that Manganese, which has several toxic effects, might contribute to the higher incidence of MS previously observed in a cluster of communalities in the south-eastern flank of the Etna volcano, where volcanic ashes rich in TE usually fall due to the prevailing winds. Conclusions: Exposition to high levels of Mn could be a cofactor in the pathogenesis of MS.
    Description: Published
    Description: Milano
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Keywords: Multiple Sclerosis ; Mt. Etna ; 05. General
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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    Daily transcriptomes of the copepod Calanus finmarchicus during the summer solstice at high Arctic latitudes (2020)
    Springer Nature
    In:  EPIC3Scientific Data, Springer Nature
    Details
    Publication Date: 2023-06-21
    Description: The zooplankter Calanus finmarchicus is a member of the so-called “Calanus Complex”, a group of copepods that constitutes a key element of the Arctic polar marine ecosystem, providing a crucial link between primary production and higher trophic levels. Climate change induces the shift of C. finmarchicus to higher latitudes with currently unknown impacts on its endogenous timing. Here we generated a daily transcriptome of C. finmarchicus at two high Arctic stations, during the more extreme time of Midnight Sun, the summer solstice. While the southern station (74.5 °N) was sea ice-free, the northern one (82.5 °N) was sea ice-covered. The mRNAs of the 42 samples have been sequenced with an average of 126 ± 5 million reads (mean ± SE) per sample, and aligned to the reference transcriptome. We detail the quality assessment of the datasets and the complete annotation procedure, providing the possibility to investigate daily gene expression of this ecologically important species at high Arctic latitudes, and to compare gene expression according to latitude and sea ice-coverage.
    Repository Name: EPIC Alfred Wegener Institut
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    Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula (2021)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 12, pp. 7168
    Details
    Publication Date: 2023-06-21
    Description: Krill and salps are important for carbon flux in the Southern Ocean, but the extent of their contribution and the consequences of shifts in dominance from krill to salps remain unclear. We present a direct comparison of the contribution of krill and salp faecal pellets (FP) to vertical carbon flux at the Antarctic Peninsula using a combination of sediment traps, FP production, carbon content, microbial degradation, and krill and salp abundances. Salps produce 4-fold more FP carbon than krill, but the FP from both species contribute equally to the carbon flux at 300 m, accounting for 75% of total carbon. Krill FP are exported to 72% to 300 m, while 80% of salp FP are retained in the mixed layer due to fragmentation. Thus, declining krill abundances could lead to decreased carbon flux, indicating that the Antarctic Peninsula could become a less efficient carbon sink for anthropogenic CO2 in future.
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    New Insights Into Cyclone Impacts on Sea Ice in the Atlantic Sector of the Arctic Ocean in Winter (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 49(22), ISSN: 0094-8276
    Details
    Publication Date: 2023-06-21
    Description: Based on the ERA5 reanalysis, we report on statistically significant impacts of transient cyclones on sea ice concentration (SIC) in the Atlantic sector of the Arctic Ocean in winter under “New Arctic” conditions (2000–2020). This includes a pattern of reduced SIC prior to and during cyclones for the whole study domain, while a regional difference between increased SIC in the Barents Sea and reduced SIC in the Greenland Sea is found as the net effect from 3 days prior to 5 days after the cyclone passage. Generally, locally low to medium SIC conditions combined with intense cyclones drive highest SIC changes. There are indications that both thermodynamic and dynamic effects contribute to the SIC changes, but a detailed quantification is required in future research. We provide evidence that cyclone impacts on SIC have amplified compared to the “Old Arctic” (1979–1999), particularly in the Barents Sea.
    Repository Name: EPIC Alfred Wegener Institut
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  • 39
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    MOSAiC-ACA and AFLUX - Arctic airborne campaigns characterizing the exit area of MOSAiC (2022)
    Springer Nature
    In:  EPIC3Scientific data, Springer Nature, 9, pp. 1-19, ISSN: 2052-4463
    Details
    Publication Date: 2023-01-25
    Description: Two airborne field campaigns focusing on observations of Arctic mixed-phase clouds and boundary layer processes and their role with respect to Arctic amplification have been carried out in spring 2019 and late summer 2020 over the Fram Strait northwest of Svalbard. The latter campaign was closely connected to the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Comprehensive datasets of the cloudy Arctic atmosphere have been collected by operating remote sensing instruments, in-situ probes, instruments for the measurement of turbulent fluxes of energy and momentum, and dropsondes on board the AWI research aircraft Polar 5. In total, 24 flights with 111 flight hours have been performed over open ocean, the marginal sea ice zone, and sea ice. The datasets follow documented methods and quality assurance and are suited for studies on Arctic mixedphase clouds and their transformation processes, for studies with a focus on Arctic boundary layer processes, and for satellite validation applications. All datasets are freely available via the world data center PANGAEA.
    Repository Name: EPIC Alfred Wegener Institut
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  • 40
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    The Arctic Ocean’s Beaufort Gyre (2023)
    Annual Reviews
    Details
    Publication Date: 2023-02-28
    Description: © The Author(s), 2023. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Timmermans, M.-L., & Toole, J. The Arctic Ocean’s Beaufort Gyre. Annual Review of Marine Science, 15(1), (2023): 223-248, https://doi.org/10.1146/annurev-marine-032122-012034.
    Description: The Arctic Ocean's Beaufort Gyre is a dominant feature of the Arctic system, a prominent indicator of climate change, and possibly a control factor for high-latitude climate. The state of knowledge of the wind-driven Beaufort Gyre is reviewed here, including its forcing, relationship to sea-ice cover, source waters, circulation, and energetics. Recent decades have seen pronounced change in all elements of the Beaufort Gyre system. Sea-ice losses have accompanied an intensification of the gyre circulation and increasing heat and freshwater content. Present understanding of these changes is evaluated, and time series of heat and freshwater content are updated to include the most recent observations.
    Description: Support was provided by the National Science Foundation Office of Polar Programs and the Office of Naval Research.
    Keywords: Arctic Ocean ; Beaufort Gyre ; Circulation ; Sea ice ; Freshwater ; Ocean heat content
    Repository Name: Woods Hole Open Access Server
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  • 41
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    The Impact of Different Atmospheric CO2 Concentrations on Large Scale Miocene Temperature Signatures (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Paleoceanography and Paleoclimatology, American Geophysical Union (AGU), ISSN: 2572-4517
    Details
    Publication Date: 2023-02-03
    Repository Name: EPIC Alfred Wegener Institut
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  • 42
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    European tree-ring isotopes indicate unusual recent hydroclimate (2023)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 4(1), pp. 26-26, ISSN: 2662-4435
    Details
    Publication Date: 2023-02-20
    Description: In recent decades, Europe has experienced more frequent flood and drought events. However, little is known about the long-term, spatiotemporal hydroclimatic changes across Europe. Here we present a climate field reconstruction spanning the entire European continent based on tree-ring stable isotopes. A pronounced seasonal consistency in climate response across Europe leads to a unique, well-verified spatial field reconstruction of European summer hydroclimate back to AD 1600. We find three distinct phases of European hydroclimate variability as possible fingerprints of solar activity (coinciding with the Maunder Minimum and the end of the Little Ice Age) and pronounced decadal variability superimposed by a long-term drying trend from the mid-20th century. We show that the recent European summer drought (2015–2018) is highly unusual in a multi-century context and unprecedented for large parts of central and western Europe. The reconstruction provides further evidence of European summer droughts potentially being influenced by anthropogenic warming and draws attention to regional differences.
    Repository Name: EPIC Alfred Wegener Institut
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  • 43
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    Life cycle of the cold-water coral Caryophyllia huinayensis (2023)
    Springer Nature
    In:  EPIC3Scientific Reports, Springer Nature, 13(1), pp. 2593-2593, ISSN: 2045-2322
    Details
    Publication Date: 2023-03-07
    Description: Little is known about the biology of cold‑water corals (CWCs), let alone the reproduction and early life stages of these important deep‑sea foundation species. Through a three‑year aquarium experiment, we described the reproductive mode, larval release periodicity, planktonic stage, larval histology, metamorphosis and post‑larval development of the solitary scleractinian CWC Caryophyllia (Caryophyllia) huinayensis collected in Comau Fjord, Chilean Patagonia. We found that C. huinayensis is a brooder releasing 78.4 ± 65.9 (mean ± standard deviation [SD]) planula larvae throughout the year, a possible adaptation to low seasonality. Planulae had a length of 905 ± 114 μm and showed a well‑ developed gastrovascular system. After 8 ± 9.3 days (d), the larvae settled, underwent metamorphosis and developed the first set of tentacles after 2 ± 1.5 d. Skeletogenesis, zooplankton feeding and initiation of the fourth set of tentacles started 5 ± 2.1 d later, 21 ± 12.9 d, and 895 ± 45.9 d after settlement, respectively. Our study shows that the ontogenetic timing of C. huinayensis is comparable to that of some tropical corals, despite lacking zooxanthellae.
    Repository Name: EPIC Alfred Wegener Institut
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  • 44
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    A baseline study of spatial variability of bacteria (total coliform, E. coli, and Enterococcus spp.) as biomarkers of pollution in ten tropical Atlantic beaches: concern for environmental and public health (2021)
    Springer Nature
    In:  EPIC3Environmental Science and Pollution Research, Springer Nature, 28(36), pp. 50941-50965, ISSN: 0944-1344
    Details
    Publication Date: 2023-03-07
    Description: Coastal water quality in urban cities is increasingly impacted by human activities such as agricultural runoff, sewage discharges, and poor sanitation. However, environmental factors controlling bacteria abundance remain poorly understood. The study employed multiple indicators to assess ten beach water qualities in Ghana during minor wet seasons. Environmental parameters (e.g. temperature, electrical conductivity, total dissolved solids) were measured in situ using the Horiba multiple parameter probe. Surface water samples were collected to measure total suspended solids, nutrients, and chlorophyll-a via standard methods and bacteria determination through membrane filtration. Environmental parameters measured showed no significant variation for the sample period. However, bacteria loads differ significantly (p = 0.024) among the beaches and influenced significantly by nitrate (55.3%, p = 0.02) and total dissolved solids (17.1%, p = 0.017). The baseline study detected an increased amount of total coliforms and faecal indicator bacteria (Escherichia coli and Enterococcus spp.) in beach waters along the coast of Ghana, suggesting faecal contamination, which can pose health risks. The mean ± standard deviations of bacteria loads in beach water are total coliforms (4.06 × 103 ± 4.16 × 103 CFU/100 mL), E. coli (7.06 × 102 ± 1.72 × 103 CFU/100 mL), and Enterococcus spp. (6.15 × 102 ± 1.75 × 103 CFU/100 mL). Evidence of pollution calls for public awareness to prevent ecological and health-related risks and policy reforms to control coastal water pollution. Future research should focus on identifying the sources of contamination in the tropical Atlantic region.
    Repository Name: EPIC Alfred Wegener Institut
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  • 45
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    Atmospheric concentrations of black carbon are substantially higher in spring than summer in the Arctic (2023)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 4(1), pp. 91-91, ISSN: 2662-4435
    Details
    Publication Date: 2024-02-07
    Description: A key driving factor behind rapid Arctic climate change is black carbon, the atmospheric aerosol that most efficiently absorbs sunlight. Our knowledge about black carbon in the Arctic is scarce, mainly limited to long-term measurements of a few ground stations and snap-shots by aircraft observations. Here, we combine observations from aircraft campaigns performed over nine years, and present vertically resolved average black carbon properties. A factor of four higher black carbon mass concentration (21.6 ng m−3 average, 14.3 ng m−3 median) was found in spring, compared to summer (4.7 ng m−3 average, 3.9 ng m−3 median). In spring, much higher inter-annual and geographic variability prevailed compared to the stable situation in summer. The shape of the black carbon size distributions remained constant between seasons with an average mass mean diameter of 202 nm in spring and 210 nm in summer. Comparison between observations and concentrations simulated by a global model shows notable discrepancies, highlighting the need for further model developments and intensified measurements.
    Repository Name: EPIC Alfred Wegener Institut
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  • 46
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    Blue economy discourses and practices: reconfiguring ocean spaces in the Philippines (2020)
    Springer Nature
    In:  EPIC3Maritime Studies, Springer Nature, 19(2), pp. 207-221, ISSN: 1872-7859
    Details
    Publication Date: 2024-02-07
    Description: Blue economy initiatives have emerged along marine and coastal areas, seeking to bring the green economy into a ‘blue world’. Often defined as a global policy agenda, blue economy discourses and practices aim to generate ‘blue growth’ by linking poverty reduction, social equality, and marine conservation. While global and national policies have spent decades addressing coastal resource management, broader blue economy discourses and practices seem, on the surface, to promote economic growth strategies for marine conservation. Increasingly, new market-oriented programs and projects aim to tap the financial value of the ocean’s ‘blue capital’, ostensibly fostering income generation and sustainable solutions for conservation finance. Drawing on critical discourse analysis and key-informant interviews across scales, we examine the meanings and practices of the blue economy in Southeast Asia and in the Philippines. As an archipelagic nation, millions of coastal dwellers in the Philippines depend on oceans as a major source of livelihood, food security, and well-being. We examine how multilateral institutions, bilateral organisations, state agencies, civil society organisations, and other key actors represent and enact the blue economy discursively and in practice. We find that oceans are being imagined as an open frontier that must be managed and utilised for both conservation and economic purposes. New territorialisation processes are creating new borders and management structures that often bypass social and environmental safeguards, posing a major threat to coastal dwellers. We conclude that by foregrounding economic development and coastal management, more socially just and environmentally sustainable governance approaches are neglected.
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  • 47
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    Permafrost Carbon: Progress on Understanding Stocks and Fluxes Across Northern Terrestrial Ecosystems (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research: Biogeosciences, American Geophysical Union (AGU), 129(3), ISSN: 2169-8953
    Details
    Publication Date: 2024-02-27
    Description: Significant progress in permafrost carbon science made over the past decades include the identification of vast permafrost carbon stocks, the development of new pan‐Arctic permafrost maps, an increase in terrestrial measurement sites for CO〈jats:sub〉2〈/jats:sub〉 and methane fluxes, and important factors affecting carbon cycling, including vegetation changes, periods of soil freezing and thawing, wildfire, and other disturbance events. Process‐based modeling studies now include key elements of permafrost carbon cycling and advances in statistical modeling and inverse modeling enhance understanding of permafrost region C budgets. By combining existing data syntheses and model outputs, the permafrost region is likely a wetland methane source and small terrestrial ecosystem CO〈jats:sub〉2〈/jats:sub〉 sink with lower net CO〈jats:sub〉2〈/jats:sub〉 uptake toward higher latitudes, excluding wildfire emissions. For 2002–2014, the strongest CO〈jats:sub〉2〈/jats:sub〉 sink was located in western Canada (median: −52 g C m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉) and smallest sinks in Alaska, Canadian tundra, and Siberian tundra (medians: −5 to −9 g C m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉). Eurasian regions had the largest median wetland methane fluxes (16–18 g CH〈jats:sub〉4〈/jats:sub〉 m〈jats:sup〉−2〈/jats:sup〉 y〈jats:sup〉−1〈/jats:sup〉). Quantifying the regional scale carbon balance remains challenging because of high spatial and temporal variability and relatively low density of observations. More accurate permafrost region carbon fluxes require: (a) the development of better maps characterizing wetlands and dynamics of vegetation and disturbances, including abrupt permafrost thaw; (b) the establishment of new year‐round CO〈jats:sub〉2〈/jats:sub〉 and methane flux sites in underrepresented areas; and (c) improved models that better represent important permafrost carbon cycle dynamics, including non‐growing season emissions and disturbance effects.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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    Late Holocene Dust Deposition Fluxes Over the Entire South Atlantic Ocean (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Geochemistry Geophysics Geosystems, American Geophysical Union (AGU), 25(1), ISSN: 1525-2027
    Details
    Publication Date: 2024-03-04
    Description: Mineral dust accumulated on the ocean floor is an important archive for reconstructing past atmospheric circulation changes and climatological conditions in the source areas. Dust emitted from Southern Hemisphere dust sources is widely deposited over the oceans. However, there are few records of dust deposition over the open ocean, and a large need for extended geographical coverage exists. We present a large data set (134 surface sediment samples) of Late Holocene dust deposition from seafloor surface sediments covering the entire South Atlantic Ocean. Polymodal grain-size distributions of the lithogenic fraction indicate that the sediments are composed of multiple sediment components. By using end-member modeling, we attempt to disentangle the dust signal from non-aeolian sediments. Combined with 230Th-normalized lithogenic fluxes, we quantified the specific deposition fluxes for mineral dust, crrent-sorted sediments and ice-rafted debris (IRD). Although the method could not completely separate the different components in every region, it shows that dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—amounts up to approximately 0.7 g cm−2 Kyr−1 and decreases downwind. Bottom-current-sorted sediments and IRD are mostly concentrated around the continental margins. The ratio of the coarse to fine dust end members reveals input from north African dust sources to the South Atlantic. The majority of the observations are in good agreement with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic could be used to calibrate and validate further model simulations.
    Repository Name: EPIC Alfred Wegener Institut
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  • 49
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    Generation of macro- and microplastic databases by high-throughput FTIR analysis with microplate readers (2024)
    Springer Nature
    In:  EPIC3Analytical and Bioanalytical Chemistry, Springer Nature, 416(6), pp. 1311-1320, ISSN: 1618-2642
    Details
    Publication Date: 2024-03-04
    Description: FTIR spectral identification is today’s gold standard analytical procedure for plastic pollution material characterization. High-throughput FTIR techniques have been advanced for small microplastics (10–500 µm) but less so for large microplastics (500–5 mm) and macroplastics (〉 5 mm). These larger plastics are typically analyzed using ATR, which is highly manual and can sometimes destroy particles of interest. Furthermore, spectral libraries are often inadequate due to the limited variety of reference materials and spectral collection modes, resulting from expensive spectral data collection. We advance a new high-throughput technique to remedy these problems using FTIR microplate readers for measuring large particles (〉 500 µm). We created a new reference database of over 6000 spectra for transmission, ATR, and reflection spectral collection modes with over 600 plastic, organic, and mineral reference materials relevant to plastic pollution research. We also streamline future analysis in microplate readers by creating a new particle holder for transmission measurements using off-the-shelf parts and fabricating a nonplastic 96-well microplate for storing particles. We determined that particles should be presented to microplate readers as thin as possible due to thick particles causing poor-quality spectra and identifications. We validated the new database using Open Specy and demonstrated that additional transmission and reflection spectra reference data were needed in spectral libraries.
    Repository Name: EPIC Alfred Wegener Institut
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  • 50
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    Phaeocystis: A Global Enigma (2024)
    Annual Reviews
    In:  EPIC3Annual Review of Marine Science, Annual Reviews, 16(1), pp. 417-441, ISSN: 1941-1405
    Details
    Publication Date: 2024-03-01
    Description: The genus Phaeocystis is globally distributed, with blooms commonly occurring on continental shelves. This unusual phytoplankter has two major morphologies: solitary cells and cells embedded in a gelatinous matrix. Only colonies form blooms. Their large size (commonly 2 mm but up to 3 cm) and mucilaginous envelope allow the colonies to escape predation, but data are inconsistent as to whether colonies are grazed. Cultured Phaeocystis can also inhibit the growth of co-occurring phytoplankton or the feeding of potential grazers. Colonies and solitary cells use nitrate as a nitrogen source, although solitary cells can also grow on ammonium. Phaeocystis colonies might be a major contributor to carbon flux to depth, but in most cases, colonies are rapidly remineralized in the upper 300 m. The occurrence of large Phaeocystis blooms is often associated with environments with low and highly variable light and high nitrate levels, with Phaeocystis antarctica blooms being linked additionally to high iron availability. Emerging results indicate that different clones of Phaeocystis have substantial genetic plasticity, which may explain its appearance in a variety of environments. Given the evidence of Phaeocystis appearing in new systems, this trend will likely continue in the near future.
    Repository Name: EPIC Alfred Wegener Institut
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  • 51
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    Revised historical Northern Hemisphere black carbon emissions based on inverse modeling of ice core records (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), pp. 271-271, ISSN: 2041-1723
    Details
    Publication Date: 2024-03-01
    Description: Black carbon emitted by incomplete combustion of fossil fuels and biomass has a net warming effect in the atmosphere and reduces the albedo when deposited on ice and snow; accurate knowledge of past emissions is essential to quantify and model associated global climate forcing. Although bottom-up inventories provide historical Black Carbon emission estimates that are widely used in Earth System Models, they are poorly constrained by observations prior to the late 20th century. Here we use an objective inversion technique based on detailed atmospheric transport and deposition modeling to reconstruct 1850 to 2000 emissions from thirteen Northern Hemisphere ice-core records. We find substantial discrepancies between reconstructed Black Carbon emissions and existing bottom-up inventories which do not fully capture the complex spatial-temporal emission patterns. Our findings imply changes to existing historical Black Carbon radiative forcing estimates are necessary, with potential implications for observation-constrained climate sensitivity.
    Repository Name: EPIC Alfred Wegener Institut
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    The Role of Coastal Yedoma Deposits and Continental Shelf Sediments in the Arctic Ocean Silicon Cycle (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 38(1), ISSN: 0886-6236
    Details
    Publication Date: 2024-02-13
    Description: The availability of silicon (Si) in the ocean plays an important role in regulating biogeochemical and ecological processes. The Si budget of the Arctic Ocean appears balanced, with inputs equivalent to outputs, though it is unclear how a changing climate might aggravate this balance. In this study, we focus on Si cycling in Arctic coastal areas and continental shelf sediments to better constrain the Arctic Ocean Si budget. We provide the first estimate of amorphous Si (ASi) loading from erosion of coastal Yedoma deposits (30–90 Gmol yr−1), demonstrating comparable rates to particulate Si loading from rivers (10–90 Gmol yr−1). We found a positive relationship between surface sediment ASi and organic matter content on continental shelves. Combining these values with published Arctic shelf sediment properties and burial rates we estimate 70 Gmol Si yr−1 is buried on Arctic continental shelves, equivalent to 4.5% of all Si inputs to the Arctic Ocean. Sediment dissolved Si fluxes increased with distance from river mouths along cruise transects of shelf regions influenced by major rivers in the Laptev and East Siberian seas. On an annual basis, we estimate that Arctic shelf sediments recycle approximately up to twice as much DSi (680 Gmol Si) as is loaded from rivers (340–500 Gmol Si).
    Repository Name: EPIC Alfred Wegener Institut
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  • 53
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    A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 38(1), ISSN: 0886-6236
    Details
    Publication Date: 2024-02-13
    Description: The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ∼60% larger in models (−0.72 vs. −0.44 PgC year−1, 1998–2018, coastal ocean extending to 300 km offshore or 1,000 m isobath with area of 77 million km2). We attribute most of this model-product difference to the seasonality in sea surface CO2 partial pressure at mid- and high-latitudes, where models simulate stronger winter CO2 uptake. The coastal ocean CO2 sink has increased in the past decades but the available time-resolving observation-based products and models show large discrepancies in the magnitude of this increase. The global coastal ocean is a major source of N2O (+0.70 PgCO2-e year−1 in observational product and +0.54 PgCO2-e year−1 in model median) and CH4 (+0.21 PgCO2-e year−1 in observational product), which offsets a substantial proportion of the coastal CO2 uptake in the net radiative balance (30%–60% in CO2-equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.
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  • 54
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    Quantifying Sub\xe2\x80\x90Seasonal Growth Rate Changes in Fossil Giant Clams Using Wavelet Transformation of Daily Mg/Ca Cycles (2023)
    American Geophysical Union (AGU)
    In:  Geochemistry, Geophysics, Geosystems vol. 24 no. 10
    Details
    Publication Date: 2024-02-08
    Description: Shells of the giant clam Tridacna can provide decade-long records of past environmental conditions via their geochemical composition and structurally through growth banding. Counting the daily bands can give an accurate internal age model with high temporal resolution, but daily banding is not always visually retrievable, especially in fossil specimens. We show that daily geochemical cycles (e.g., Mg/Ca) are resolvable via highly spatially resolved laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS; 3 \xc3\x97 33 \xce\xbcm laser slit) in our Miocene (\xe2\x88\xbc10 Ma) specimen, even in areas where daily banding is not visually discernible. By applying wavelet transformation on the measured daily geochemical cycles, we quantify varying daily growth rates throughout the shell. These growth rates are thus used to build an internal age model independent of optical daily band countability. Such an age model can be used to convert the measured elemental ratios from a function of distance to a function of time, which helps evaluate paleoenvironmental proxy data, for example, regarding the timing of sub-seasonal events. Furthermore, the quantification of daily growth rates across the shell facilitates the evaluation of (co)dependencies between growth rates and corresponding elemental compositions.
    Keywords: Tridacna
    Repository Name: National Museum of Natural History, Netherlands
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  • 55
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    Selective Sorting and Degradation of Permafrost Organic Matter in the Nearshore Zone of Herschel Island (Yukon, Canada) (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research Biogeosciences, American Geophysical Union (AGU), 129(1), ISSN: 2169-8953
    Details
    Publication Date: 2024-01-26
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Erosion of permafrost coasts due to climate warming releases large quantities of organic carbon (OC) into the Arctic Ocean. While burial of permafrost OC in marine sediments potentially limits degradation, resuspension of sediments in the nearshore zone potentially enhances degradation and greenhouse gas production, adding to the “permafrost carbon feedback.” Recent studies, focusing on bulk sediments, suggest that permafrost OC derived from coastal erosion is predominantly deposited close to shore. However, bulk approaches disregard sorting processes in the coastal zone, which strongly influence the OC distribution and fate. We studied soils and sediments along a transect from the fast‐eroding shoreline of Herschel Island—〈jats:italic〉Qikiqtaruk〈/jats:italic〉 (Yukon, Canada) to a depositional basin offshore. Sample material was fractionated by density (1.8 g cm〈jats:sup〉−3〈/jats:sup〉) and size (63 μm), separating loose OC from mineral‐associated OC. Each fraction was analyzed for element content (TOC, TN), carbon isotopes (δ〈jats:sup〉13〈/jats:sup〉C, Δ〈jats:sup〉14〈/jats:sup〉C), molecular biomarkers (〈jats:italic〉n〈/jats:italic〉‐alkanes, 〈jats:italic〉n〈/jats:italic〉‐alkanoic acids, lignin phenols, cutin acids), and mineral surface area. The OC partitioning between fractions changes considerably along the transect, highlighting the importance of hydrodynamic sorting in the nearshore zone. Additionally, OC and biomarker loadings decrease along the land‐ocean transect, indicating significant loss of OC during transport. However, molecular proxies for degradation show contrasting trends, suggesting that OC losses are not always well reflected in its degradation state. This study, using fraction partitioning that crosses land‐ocean boundaries in a way not done before, aids to disentangle sorting processes from degradation patterns, and provides quantitative insight into losses of thawed and eroded permafrost OC.〈/jats:p〉
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    Postdepositional Behavior of Molybdenum in Deep Sediments and Implications for Paleoredox Reconstruction (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(21), ISSN: 0094-8276
    Details
    Publication Date: 2023-11-01
    Description: Molybdenum (Mo) is a trace element sensitive to oceanic redox conditions. The fidelity of sedimentary Mo as a paleoredox proxy of coeval seawater depends on the extent of Mo remobilization during postdepositional processes. Here we present the Mo content and isotope profiles for deep sediments from the Nankai Trough, Japan. The Mo signature suggests that these sediments have experienced extensive early diagenesis and hydrothermal alteration at depth. Iron (Fe)‐manganese (Mn) (oxyhydr)oxide alteration combined with Mo thiolation leads to a more than twenty‐fold enrichment of Mo within the sulfate reduction zone. Hydrothermal fluids and Mo adsorption onto Fe‐Mn (oxyhydr)oxides cause extremely negative Mo‐isotope values at the underthrust zone. These postdepositional Mo signals might be misinterpreted as expanded anoxia in the water column. Our findings highlight the importance of constraining postdepositional effects on Mo‐based proxies during paleoredox reconstruction.
    Repository Name: EPIC Alfred Wegener Institut
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  • 57
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    Ecological mechanisms and current systems shape the modular structure of the global oceans’ prokaryotic seascape (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), 15 p., pp. 6141-6141, ISSN: 2041-1723
    Details
    Publication Date: 2023-11-08
    Description: Major biogeographic features of the microbial seascape in the oceans have been established and their underlying ecological mechanisms in the (sub)tropical oceans and the Pacific Ocean identified. However, we still lack a unifying understanding of how prokaryotic communities and biogeographic patterns are affected by large-scale current systems in distinct ocean basins and how they are globally shaped in line with ecological mechanisms. Here we show that prokaryotic communities in the epipelagic Pacific and Atlantic Ocean, in the southern Indian Ocean, and the Mediterranean Sea are composed of modules of co-occurring taxa with similar environmental preferences. The relative partitioning of these modules varies along latitudinal and longitudinal gradients and are related to different hydrographic and biotic conditions. Homogeneous selection and dispersal limitation were identified as the major ecological mechanisms shaping these communities and their free-living (FL) and particle-associated (PA) fractions. Large-scale current systems govern the dispersal of prokaryotic modules leading to the highest diversity near subtropical fronts.
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  • 58
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    Availability of vitamin B12 and its lower ligand intermediate α-ribazole impact prokaryotic and protist communities in oceanic systems (2022)
    Springer Nature
    In:  EPIC3The ISME Journal: Multidisciplinary Journal of Microbial Ecology, Springer Nature, 16(8), pp. 2002-2014, ISSN: 1751-7362
    Details
    Publication Date: 2023-11-14
    Description: Genome analyses predict that the cofactor cobalamin (vitamin B12, called B12 herein) is produced by only one-third of all prokaryotes but almost all encode at least one B12-dependent enzyme, in most cases methionine synthase. This implies that the majority of prokaryotes relies on exogenous B12 supply and interacts with producers. B12 consists of a corrin ring centred around a cobalt ion and the lower ligand 5’6-dimethylbenzimidazole (DMB). It has never been tested whether availability of this pivotal cofactor, DMB or its intermediate α-ribazole affect growth and composition of prokaryotic microbial communities. Here we show that in the subtropical, equatorial and polar frontal Pacific Ocean supply of B12 and α-ribazole enhances heterotrophic prokaryotic production and alters the composition of prokaryotic and heterotrophic protist communities. In the polar frontal Pacific, the SAR11 clade and Oceanospirillales increased their relative abundances upon B12 supply. In the subtropical Pacific, Oceanospirillales increased their relative abundance upon B12 supply as well but also downregulated the transcription of the btuB gene, encoding the outer membrane permease for B12. Surprisingly, Prochlorococcus, known to produce pseudo-B12 and not B12, exhibited significant upregulation of genes encoding key proteins of photosystem I + II, carbon fixation and nitrate reduction upon B12 supply in the subtropical Pacific. These findings show that availability of B12 and α-ribazole affect growth and composition of prokaryotic and protist communities in oceanic systems thus revealing far-reaching consequences of methionine biosynthesis and other B12-dependent enzymatic reactions on a community level.
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  • 59
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    Vitamin B12 is not shared by all marine prototrophic bacteria with their environment (2023)
    Springer Nature
    In:  EPIC3The ISME Journal: Multidisciplinary Journal of Microbial Ecology, Springer Nature, 17(6), pp. 836-845, ISSN: 1751-7362
    Details
    Publication Date: 2023-11-14
    Description: Vitamin B12 (cobalamin, herein B12) is an essential cofactor involved in amino acid synthesis and carbon resupply to the TCA cycle for most prokaryotes, eukaryotic microorganisms, and animals. Despite being required by most, B12 is produced by only a minor fraction of prokaryotes and therefore leads to complex interaction between prototrophs and auxotrophs. However, it is unknown how B12 is provided by prototrophs to auxotrophs. In this study, 33 B12 prototrophic alphaproteobacterial strains were grown in co-culture with Thalassiosira pseudonana, a B12 auxotrophic diatom, to determine the bacterial ability to support the growth of the diatom by sharing B12. Among these strains, 18 were identified to share B12 with the diatom, while nine were identified to retain B12 and not support growth of the diatom. The other bacteria either shared B12 with the diatom only with the addition of substrate or inhibited the growth of the diatom. Extracellular B12 measurements of B12-provider and B12-retainer strains confirmed that the cofactor could only be detected in the environment of the tested B12-provider strains. Intracellular B12 was measured by LC-MS and showed that the concentrations of the different B12-provider as well as B12-retainer strains differed substantially. Although B12 is essential for the vast majority of microorganisms, mechanisms that export this essential cofactor are still unknown. Our results suggest that a large proportion of bacteria that can synthesise B12de novo cannot share the cofactor with their environment.
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  • 60
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    The overlooked role of a biotin precursor for marine bacteria - desthiobiotin as an escape route for biotin auxotrophy (2022)
    Springer Nature
    In:  EPIC3The ISME Journal: Multidisciplinary Journal of Microbial Ecology, Springer Nature, 16(11), pp. 2599-2609, ISSN: 1751-7362
    Details
    Publication Date: 2023-11-14
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Biotin (vitamin B〈jats:sub〉7〈/jats:sub〉) is involved in a wide range of essential biochemical reactions and a crucial micronutrient that is vital for many pro- and eukaryotic organisms. The few biotin measurements in the world’s oceans show that availability is subject to strong fluctuations. Numerous marine microorganisms exhibit biotin auxotrophy and therefore rely on supply by other organisms. Desthiobiotin is the primary precursor of biotin and has recently been detected at concentrations similar to biotin in seawater. The last enzymatic reaction in the biotin biosynthetic pathway converts desthiobiotin to biotin via the biotin synthase (BioB). The role of desthiobiotin as a precursor of biotin synthesis in microbial systems, however, is largely unknown. Here we demonstrate experimentally that bacteria can overcome biotin auxotrophy if they retain the 〈jats:italic〉bioB〈/jats:italic〉 gene and desthiobiotin is available. A genomic search of 1068 bacteria predicts that the biotin biosynthetic potential varies greatly among different phylogenetic groups and that 20% encode solely 〈jats:italic〉bioB〈/jats:italic〉 and thus can potentially overcome biotin auxotrophy. Many 〈jats:italic〉Actino〈/jats:italic〉- and 〈jats:italic〉Alphaproteobacteria〈/jats:italic〉 cannot synthesize biotin de novo, but some possess solely 〈jats:italic〉bioB〈/jats:italic〉, whereas the vast majority of 〈jats:italic〉Gammaproteobacteria〈/jats:italic〉 and 〈jats:italic〉Flavobacteriia〈/jats:italic〉 exhibit the last four crucial biotin synthesis genes. We detected high intra- and extracellular concentrations of the precursor relative to biotin in the prototrophic bacterium, 〈jats:italic〉Vibrio campbellii〈/jats:italic〉, with extracellular desthiobiotin reaching up to 1.09 ± 0.15*10〈jats:sup〉6〈/jats:sup〉 molecules per cell during exponential growth. Our results provide evidence for the ecological role of desthiobiotin as an escape route to overcome biotin auxotrophy for bacteria in the ocean and presumably in other ecosystems.〈/jats:p〉
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  • 61
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    Selection, drift and community interactions shape microbial biogeographic patterns in the Pacific Ocean (2022)
    Springer Nature
    In:  EPIC3The ISME Journal: Multidisciplinary Journal of Microbial Ecology, Springer Nature, 16(12), pp. 2653-2665, ISSN: 1751-7362
    Details
    Publication Date: 2023-11-14
    Description: Despite accumulating data on microbial biogeographic patterns in terrestrial and aquatic environments, we still lack a comprehensive understanding of how these patterns establish, in particular in ocean basins. Here we show the relative significance of the ecological mechanisms selection, dispersal and drift for shaping the composition of microbial communities in the Pacific Ocean over a transect of 12,400 km between subantarctic and subarctic regions. In the epipelagic, homogeneous selection contributes 50–60% and drift least to the three mechanism for the assembly of prokaryotic communities whereas in the upper mesopelagic, drift is relatively most important for the particle-associated subcommunities. Temperature is important for the relative significance of homogeneous selection and dispersal limitation for community assembly. The relative significance of both mechanisms was inverted with increasing temperature difference along the transect. For eukaryotes 〉8 µm, homogeneous selection is also the most important mechanisms at two epipelagic depths whereas at all other depths drift is predominant. As species interactions are essential for structuring microbial communities we further analyzed co-occurrence-based community metrics to assess biogeographic patterns over the transect. These interaction-adjusted indices explained much better variations in microbial community composition as a function of abiotic and biotic variables than compositional or phylogenetic distance measures like Bray–Curtis or UniFrac. Our analyses are important to better understand assembly processes of microbial communities in the upper layers of the largest ocean and how they adapt to effectively perform in global biogeochemical processes. Similar principles presumably act upon microbial community assembly in other ocean basins.
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  • 62
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    Availability of vitamin B12 and its lower ligand intermediate α-ribazole impact prokaryotic and protist communities in oceanic systems (2022)
    Springer Nature
    In:  EPIC3The ISME Journal: Multidisciplinary Journal of Microbial Ecology, Springer Nature, 16(8), pp. 2002-2014, ISSN: 1751-7362
    Details
    Publication Date: 2023-11-14
    Description: Genome analyses predict that the cofactor cobalamin (vitamin B12, called B12 herein) is produced by only one-third of all prokaryotes but almost all encode at least one B12-dependent enzyme, in most cases methionine synthase. This implies that the majority of prokaryotes relies on exogenous B12 supply and interacts with producers. B12 consists of a corrin ring centred around a cobalt ion and the lower ligand 5’6-dimethylbenzimidazole (DMB). It has never been tested whether availability of this pivotal cofactor, DMB or its intermediate α-ribazole affect growth and composition of prokaryotic microbial communities. Here we show that in the subtropical, equatorial and polar frontal Pacific Ocean supply of B12 and α-ribazole enhances heterotrophic prokaryotic production and alters the composition of prokaryotic and heterotrophic protist communities. In the polar frontal Pacific, the SAR11 clade and Oceanospirillales increased their relative abundances upon B12 supply. In the subtropical Pacific, Oceanospirillales increased their relative abundance upon B12 supply as well but also downregulated the transcription of the btuB gene, encoding the outer membrane permease for B12. Surprisingly, Prochlorococcus, known to produce pseudo-B12 and not B12, exhibited significant upregulation of genes encoding key proteins of photosystem I + II, carbon fixation and nitrate reduction upon B12 supply in the subtropical Pacific. These findings show that availability of B12 and α-ribazole affect growth and composition of prokaryotic and protist communities in oceanic systems thus revealing far-reaching consequences of methionine biosynthesis and other B12-dependent enzymatic reactions on a community level.
    Repository Name: EPIC Alfred Wegener Institut
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    Significance of gene variants for the functional biogeography of the near-surface Atlantic Ocean microbiome (2022)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 13(1), pp. 456-456, ISSN: 2041-1723
    Details
    Publication Date: 2023-11-14
    Description: Microbial communities are major drivers of global elemental cycles in the oceans due to their high abundance and enormous taxonomic and functional diversity. Recent studies assessed microbial taxonomic and functional biogeography in global oceans but microbial functional biogeography remains poorly studied. Here we show that in the near-surface Atlantic and Southern Ocean between 62°S and 47°N microbial communities exhibit distinct taxonomic and functional adaptations to regional environmental conditions. Richness and diversity showed maxima around 40° latitude and intermediate temperatures, especially in functional genes (KEGG-orthologues, KOs) and gene profiles. A cluster analysis yielded three clusters of KOs but five clusters of genes differing in the abundance of genes involved in nutrient and energy acquisition. Gene profiles showed much higher distance-decay rates than KO and taxonomic profiles. Biotic factors were identified as highly influential in explaining the observed patterns in the functional profiles, whereas temperature and biogeographic province mainly explained the observed taxonomic patterns. Our results thus indicate fine-tuned genetic adaptions of microbial communities to regional biotic and environmental conditions in the Atlantic and Southern Ocean.
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  • 64
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    Regional but not global temperature variability underestimated by climate models at supradecadal timescales (2023)
    Springer Nature
    In:  EPIC3Nature Geoscience, Springer Nature, 16(11), pp. 958-966, ISSN: 1752-0894
    Details
    Publication Date: 2023-11-16
    Repository Name: EPIC Alfred Wegener Institut
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  • 65
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    Temporal change in phytoplankton diversity and functional group composition (2023)
    Springer Nature
    In:  EPIC3Marine Biodiversity, Springer Nature, 53(6), pp. 72-72, ISSN: 1867-1616
    Details
    Publication Date: 2023-12-06
    Description: One of the key challenges in managing eutrophication in coastal marine ecosystems is the harmonized cross-border assessment of phytoplankton. Some general understanding of the consequences of shifting nutrient regimes can be derived from the detailed investigation of the phytoplankton community and its biodiversity. Here, we combined long-term monitoring datasets of German and Dutch coastal stations and amended these with additional information on species biomass. Across the integrated and harmonized dataset, we used multiple biodiversity descriptors to analyse temporal trends in the Wadden Sea phytoplankton. Biodiversity, measured as the number of species (S) and the effective number of species (ENS), has decreased in the Dutch stations over the last 20 years, while biomass has increased, indicating that fewer species are becoming more dominant in the system. However, biodiversity and biomass did not show substantial changes in the German stations. Although there were some differences in trends between countries, shifts in community composition and relative abundance were consistent across stations and time. We emphasise the importance of continuous and harmonized monitoring programmes and multi-metric approaches that can detect changes in the communities that are indicative of changes in the environment.
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  • 66
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    Reply to: Empirical pressure-response relations can benefit assessment of safe operating spaces (2021)
    Springer Nature
    In:  EPIC3Nature Ecology & Evolution, Springer Nature, 5(8), pp. 1080-1081, ISSN: 2397-334X
    Details
    Publication Date: 2023-09-22
    Repository Name: EPIC Alfred Wegener Institut
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  • 67
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    Thresholds and tipping points are tempting but not necessarily suitable concepts to address anthropogenic biodiversity change—an intervention (2023)
    Springer Nature
    In:  EPIC3Marine Biodiversity, Springer Nature, 53(3), pp. 43-43, ISSN: 1867-1616
    Details
    Publication Date: 2023-09-22
    Description: Thresholds and tipping points are frequently used concepts to address the risks of global change pressures and their mitigation. It is tempting to also consider them to understand biodiversity change and design measures to ensure biotic integrity. Here, we argue that thresholds and tipping points do not work well in the context of biodiversity change for conceptual, ethical, and empirical reasons. Defining a threshold for biodiversity change (a maximum tolerable degree of turnover or loss) neglects that ecosystem multifunctionality often relies on the complete entangled web of species interactions and invokes the ethical issue of declaring some biodiversity dispensable. Alternatively defining a threshold for pressures on biodiversity might seem more straightforward as it addresses the causes of biodiversity change. However, most biodiversity change appears to be gradual and accumulating over time rather than reflecting a disproportionate change when transgressing a pressure threshold. Moreover, biodiversity change is not in synchrony with environmental change, but massively delayed through inertia inflicted by population dynamics and demography. In consequence, formulating environmental management targets as preventing the transgression of thresholds is less useful in the context of biodiversity change, as such thresholds neither capture how biodiversity responds to anthropogenic pressures nor how it links to ecosystem functioning. Instead, addressing biodiversity change requires reflecting the spatiotemporal complexity of altered local community dynamics and temporal turnover in composition leading to shifts in distributional ranges and species interactions.
    Repository Name: EPIC Alfred Wegener Institut
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  • 68
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    Plankton response to global warming is characterized by non-uniform shifts in assemblage composition since the last ice age (2022)
    Springer Nature
    In:  EPIC3Nature Ecology & Evolution, Springer Nature, 6(12), pp. 1871-1880, ISSN: 2397-334X
    Details
    Publication Date: 2023-09-22
    Description: Biodiversity is expected to change in response to future global warming. However, it is difficult to predict how species will track the ongoing climate change. Here we use the fossil record of planktonic foraminifera to assess how biodiversity responded to climate change with a magnitude comparable to future anthropogenic warming. We compiled time series of planktonic foraminifera assemblages, covering the time from the last ice age across the deglaciation to the current warm period. Planktonic foraminifera assemblages shifted immediately when temperature began to rise at the end of the last ice age and continued to change until approximately 5,000 years ago, even though global temperature remained relatively stable during the last 11,000 years. The biotic response was largest in the mid latitudes and dominated by range expansion, which resulted in the emergence of new assemblages without analogues in the glacial ocean. Our results indicate that the plankton response to global warming was spatially heterogeneous and did not track temperature change uniformly over the past 24,000 years. Climate change led to the establishment of new assemblages and possibly new ecological interactions, which suggests that current anthropogenic warming may lead to new, different plankton community composition.
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  • 69
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    Biodiversity time series are biased towards increasing species richness in changing environments (2023)
    Springer Nature
    In:  EPIC3Nature Ecology & Evolution, Springer Nature, 7(7), pp. 994-1001, ISSN: 2397-334X
    Details
    Publication Date: 2023-09-21
    Description: The discrepancy between global loss and local constant species richness has led to debates over data quality, systematic biases in monitoring programmes and the adequacy of species richness to capture changes in biodiversity. We show that, more fundamentally, null expectations of stable richness can be wrong, despite independent yet equal colonization and extinction. We analysed fish and bird time series and found an overall richness increase. This increase reflects a systematic bias towards an earlier detection of colonizations than extinctions. To understand how much this bias influences richness trends, we simulated time series using a neutral model controlling for equilibrium richness and temporal autocorrelation (that is, no trend expected). These simulated time series showed significant changes in richness, highlighting the effect of temporal autocorrelation on the expected baseline for species richness changes. The finite nature of time series, the long persistence of declining populations and the potential strong dispersal limitation probably lead to richness changes when changing conditions promote compositional turnover. Temporal analyses of richness should incorporate this bias by considering appropriate neutral baselines for richness changes. Absence of richness trends over time, as previously reported, can actually reflect a negative deviation from the positive biodiversity trend expected by default.
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    A Modeling Perspective on the Lingering Glacial Sea Surface Temperature Conundrum (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 49(23), ISSN: 0094-8276
    Details
    Publication Date: 2023-09-19
    Description: The strong cooling during the Last Glacial Maximum (LGM, 21 ka BP) provides a rigorous test of climate models' ability to simulate past and future climate changes. We force an atmospheric general circulation model with two recent global LGM sea surface temperature (SST) reconstructions, one suggesting a weak and the other a more pronounced cooling, and compare the simulated land surface temperatures (LSTs) to reconstructed data. Our results do not confirm either SST reconstruction. The cold SST data set leads to good agreement between simulated and observed LSTs at low latitudes, but is systematically too cold at mid-latitudes. The opposite is true for the warm SST data set. Differences between the simulated LSTs are caused by varying land surface albedos, which is lower for the warmer SST reconstruction. The inconsistency between reconstructed and simulated climate points to a potentially significant bias in the proxy reconstructions and/or the climate sensitivity of current climate models.
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    Cyclone Impacts on Sea Ice Concentration in the Atlantic Arctic Ocean: Annual Cycle and Recent Changes (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 50(17), ISSN: 0094-8276
    Details
    Publication Date: 2023-09-08
    Description: We quantify sea ice concentration (SIC) changes related to synoptic cyclones separately for each month of the year in the Greenland, Barents and Kara Seas for 1979–2018. We find that these SIC changes can be statistically significant throughout the year. However, their strength varies from region to region and month to month, and their sign strongly depends on the considered time scale (before/during vs. after cyclone passages). Our results show that the annual cycle of cyclone impacts on SIC is related to varying cyclone intensity and traversed sea ice conditions. We further show that significant changes in these cyclone impacts have manifested in the last 40 years, with the strongest changes occurring in October and November. For these months, SIC decreases before/during cyclones have more than doubled in magnitude in the Barents and Kara Seas, while SIC increases following cyclones have weakened (intensified) in the Barents Sea (Kara Sea).
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    An Assessment of CO2 Uptake in the Arctic Ocean From 1985 to 2018 (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 37(11), ISSN: 0886-6236
    Details
    Publication Date: 2023-12-19
    Description: As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of Arctic Ocean sea-air CO2 fluxes and their uncertainties from surface ocean pCO2-observation products, ocean biogeochemical hindcast and data assimilation models, and atmospheric inversions. For the period of 1985–2018, the Arctic Ocean was a net sink of CO2 of 116 ± 4 TgC yr−1 in the pCO2 products, 92 ± 30 TgC yr−1 in the models, and 91 ± 21 TgC yr−1 in the atmospheric inversions. The CO2 uptake peaks in late summer and early autumn, and is low in winter when sea ice inhibits sea-air fluxes. The long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon (70% ± 15%), and enhanced by the atmospheric CO2 increase (19% ± 5%) and climate change (11% ± 18%). The annual mean CO2 uptake increased from 1985 to 2018 at a rate of 31 ± 13 TgC yr−1 dec−1 in the pCO2 products, 10 ± 4 TgC yr−1 dec−1 in the models, and 32 ± 16 TgC yr−1 dec−1 in the atmospheric inversions. Moreover, 77% ± 38% of the trend in the net CO2 uptake over time is caused by climate change, primarily due to rapid sea ice loss in recent years. Furthermore, true uncertainties may be larger than the given ensemble standard deviations due to common structural biases across all individual estimates.
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  • 73
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    Investigating financial statements in hospitality: a quantitative approach (2021)
    Springer Nature
    Details
    Publication Date: 2023-12-28
    Description: The aim of this paper is to investigate, through fnancial-statement analyzes, the economic fnancial performance of Italian hotels, after the international economic crisis, also con sidering the possible macro-regional diferences. The study focuses the fnancial state ments of 5473 hotels from 2009 to 2018. National data are also disaggregated in the three macro-areas that characterize Italy for diferent social and economic aspects. Anova test and Tukey–Kramer test are used. Results show that the crisis afected proftability. Ital ian hotels have a low capitalization, unable to cope with the large structural investments that require signifcant debts. The proftability indicators record similar trends in the three macro-areas, while the fnancial independence index and the coverage index show signif cant diferent values in the three observed areas. Therefore, in the digital era, Italian hotel industry has all the potential to restructure itself. Here fve ratios are considered to observe medium sized hotels. Future research with other variables will be useful, even on smaller hotels, and the analysis of their trends by cohorts of companies is necessary, as well as the integration of quantitative data with qualitative evidence. This paper encourages the cul ture of temporal sector comparison, re-evaluating the potential of accounting information systems, in order to promote data-based growth and development strategies. Furthermore, it contains indications for government ofcials, as well as for countries in the process of developing the hospitality sector following the example of the Italian experience.
    Description: Published
    Description: 383–407
    Description: OSA5: Energia e georisorse
    Description: JCR Journal
    Keywords: Italian hotels ; Tourism in Italy ; Economic-fnancial performance ; Crisis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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    Seasonal Variability of the Surface Ocean Carbon Cycle: A Synthesis (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 37(9), ISSN: 0886-6236
    Details
    Publication Date: 2024-01-06
    Description: The seasonal cycle is the dominant mode of variability in the air-sea CO2 flux in most regions of the global ocean, yet discrepancies between different seasonality estimates are rather large. As part of the Regional Carbon Cycle Assessment and Processes Phase 2 project (RECCAP2), we synthesize surface ocean pCO2 and air-sea CO2 flux seasonality from models and observation-based estimates, focusing on both a present-day climatology and decadal changes between the 1980s and 2010s. Four main findings emerge: First, global ocean biogeochemistry models (GOBMs) and observation-based estimates (pCO2 products) of surface pCO2 seasonality disagree in amplitude and phase, primarily due to discrepancies in the seasonal variability in surface DIC. Second, the seasonal cycle in pCO2 has increased in amplitude over the last three decades in both pCO2 products and GOBMs. Third, decadal increases in pCO2 seasonal cycle amplitudes in subtropical biomes for both pCO2 products and GOBMs are driven by increasing DIC concentrations stemming from the uptake of anthropogenic CO2 (Cant). In subpolar and Southern Ocean biomes, however, the seasonality change for GOBMs is dominated by Cant invasion, whereas for pCO2 products an indeterminate combination of Cant invasion and climate change modulates the changes. Fourth, biome-aggregated decadal changes in the amplitude of pCO2 seasonal variability are largely detectable against both mapping uncertainty (reducible) and natural variability uncertainty (irreducible), but not at the gridpoint scale over much of the northern subpolar oceans and over the Southern Ocean, underscoring the importance of sustained high-quality seasonally resolved measurements over these regions.
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    Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018 (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 37(10), ISSN: 0886-6236
    Details
    Publication Date: 2024-01-06
    Description: This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.
    Repository Name: EPIC Alfred Wegener Institut
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    Reversals in Temperature‐Precipitation Correlations in the Northern Hemisphere Extratropics During the Holocene (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 49(22), ISSN: 0094-8276
    Details
    Publication Date: 2024-04-23
    Description: Future precipitation levels remain uncertain because climate models have struggled to reproduce observed variations in temperature-precipitation correlations. Our analyses of Holocene proxy-based temperature-precipitation correlations and hydrological sensitivities from 2,237 Northern Hemisphere extratropical pollen records reveal a significant latitudinal dependence and temporal variations among the early, middle, and late Holocene. These proxy-based variations are largely consistent with patterns obtained from transient climate simulations (TraCE21k). While high latitudes and subtropical monsoon areas show mainly stable positive correlations throughout the Holocene, the mid-latitude pattern is temporally and spatially more variable. In particular, we identified a reversal from positive to negative temperature-precipitation correlations in the eastern North American and European mid-latitudes from the early to mid-Holocene that mainly related to slowed down westerlies and a switch to moisture-limited convection under a warm climate. Our palaeoevidence of past temperature-precipitation correlation shifts identifies those regions where simulating past and future precipitation levels might be particularly challenging.
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  • 77
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    Taxonomic and functional analyses of intact microbial communities thriving in extreme, astrobiology-relevant, anoxic sites (2021)
    Springer Nature
    In:  EPIC3Microbiome, Springer Nature, 9(1)
    Details
    Publication Date: 2024-04-23
    Description: Background: Extreme terrestrial, analogue environments are widely used models to study the limits of life and to infer habitability of extraterrestrial settings. In contrast to Earth’s ecosystems, potential extraterrestrial biotopes are usually characterized by a lack of oxygen. Methods: In the MASE project (Mars Analogues for Space Exploration), we selected representative anoxic analogue environments (permafrost, salt-mine, acidic lake and river, sulfur springs) for the comprehensive analysis of their microbial communities. We assessed the microbiome profile of intact cells by propidium monoazide-based amplicon and shotgun metagenome sequencing, supplemented with an extensive cultivation effort. Results: The information retrieved from microbiome analyses on the intact microbial community thriving in the MASE sites, together with the isolation of 31 model microorganisms and successful binning of 15 high-quality genomes allowed us to observe principle pathways, which pinpoint specific microbial functions in the MASE sites compared to moderate environments. The microorganisms were characterized by an impressive machinery to withstand physical and chemical pressures. All levels of our analyses revealed the strong and omnipresent dependency of the microbial communities on complex organic matter. Moreover, we identified an extremotolerant cosmopolitan group of 34 poly-extremophiles thriving in all sites. Conclusions: Our results reveal the presence of a core microbiome and microbial taxonomic similarities between saline and acidic anoxic environments. Our work further emphasizes the importance of the environmental, terrestrial parameters for the functionality of a microbial community, but also reveals a high proportion of living microorganisms in extreme environments with a high adaptation potential within habitability borders.
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  • 78
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    Rectifying misinformation on the climate intervention potential of ocean afforestation (2024)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 15(1), pp. 3012-3012, ISSN: 2041-1723
    Details
    Publication Date: 2024-04-19
    Repository Name: EPIC Alfred Wegener Institut
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  • 79
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    Recent European drying and its link to prevailing large-scale atmospheric patterns (2023)
    Springer Nature
    In:  EPIC3Scientific Reports, Springer Nature, 13(1), pp. 21921-21921, ISSN: 2045-2322
    Details
    Publication Date: 2024-04-22
    Description: The extreme 2018 and 2022 droughts pose as recent examples of a series of drought events that have hit Europe over the last decades with wide ranging social, environmental and economic impacts. Although the link between atmospheric circulation and meteorological drought is clear and often highlighted during major drought events, there is a lack of in-depth studies linking historical changes in meteorological drought indices and prevailing large-scale atmospheric patterns in Europe. To meet this shortfall, we investigated the relation between changes in large-scale atmospheric patterns and meteorological drought, as indicated by the geopotential height at 500mb (Z500) and the Standardised Precipitation-Evapotranspiration Index (SPEI), respectively. Calculations were done separately for four climate regions (North, West, Central-East and Mediterranean) over the growing season (March–September). Coherent patterns of significant changes towards higher pressure (increasing Z500) and drier conditions (decreasing SPEI) over 1979–2021 are found over West in spring and Central-East in summer. Z500 and SPEI are strongly linked, reflected by both significant (1979–2021) correlations and high co-occurrences (69-96%) between meteorological drought and high-pressure anomaly occurrences since 1900. North shows the most heterogeneous trend patterns and weakest links, but constitutes a hotspot of significantly increasing Z500 in September. Finally, we performed an ensemble-based, European wide analysis of future Z500, based on CMIP6 low-end (SSP126) and high-end (SSP585) 21st century emission scenarios. According to the projected changes, anomalously high-pressure systems will be the new normal regardless of scenario, and well exceeding the 2018 and 2022 levels in the case of the high-end emission scenario. However, due to the limitations of the model ensemble to represent the spatial heterogeneity in historical Z500 variability and trends (1979–2014), projected changes in large-scale circulation, and associated meteorological droughts, are highly uncertain. This paper provides new insight into significant trends in atmospheric circulation over Europe, their strong links to the observed drying trends, and the inability of a CMIP6 ensemble to reproduce the spatial heterogeneity of the circulation changes.
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  • 80
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    A ~700 years perspective on the 21st century drying in the eastern part of Europe based on δ18O in tree ring cellulose (2022)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 3(1), pp. 277-277, ISSN: 2662-4435
    Details
    Publication Date: 2024-04-22
    Description: Numerical simulations indicate that extreme climate events (e.g., droughts, floods, heat waves) will increase in a warming world, putting enormous pressure on society and political decision-makers. To provide a long-term perspective on the variability of these extreme events, here we use a ~700 years tree-ring oxygen isotope chronology from Eastern Europe, in combination with paleo-reanalysis data, to show that the summer drying over Eastern Europe observed over the last ~150 years is to the best of our knowledge unprecedented over the last 700 years. This drying is driven by a change in the pressure patterns over Europe, characterized by a shift from zonal to a wavier flow around 1850CE, leading to extreme summer droughts and aridification. To our knowledge, this is the first and longest reconstruction of drought variability, based on stable oxygen isotopes in the tree-ring cellulose, for Eastern Europe, helping to fill a gap in the spatial coverage of paleoclimate reconstructions.
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    Interdecadal Pacific Oscillation in Northern Greenland Dust Concentration Variability During the Last 400 Years (2022)
    American Geophysical Union (AGU)
    In:  EPIC3Geophysical Research Letters, American Geophysical Union (AGU), 49(24), ISSN: 0094-8276
    Details
    Publication Date: 2024-04-22
    Description: Statistical analysis of reanalysis and observed data reveals that high dust surface mass concentration in northern Greenland is associated with a Pacific Decadal Oscillation like pattern in its negative phase in the North Pacific as well as with La Niña conditions in the tropical Pacific region. The sea surface temperature anomalies in the Pacific realm resemble the Interdecadal Pacific Oscillation (IPO). The associated atmospheric circulation pattern, in the form of a wave-train from the North Pacific to the Eurasian continent, favors enhanced dust uptake and transport toward the northern Greenland. Similar patterns are associated with a low-resolution stacked record of five Ca2+ ice cores, that is, ngt03C93.2 (B16), ngt14C93.2 (B18), ngt27C94.2 (B21), GISP2−B, and NEEM-2011-S1, from northern Greenland, a proxy for regional dust concentration, during the last 400 years. We argue that northern Greenland ice core dust records could be used as proxies for the IPO and related teleconnections.
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  • 82
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    Diversity and structure of feather mite communities on seabirds from the north–east Atlantic and Mediterranean Sea (2023)
    Springer Nature
    In:  EPIC3Scientific Reports, Springer Nature, 13(1), pp. 4793-4793, ISSN: 2045-2322
    Details
    Publication Date: 2024-04-22
    Description: The richness and structure of symbiont assemblages are shaped by many factors acting at different spatial and temporal scales. Among them, host phylogeny and geographic distance play essential roles. To explore drivers of richness and structure of symbiont assemblages, feather mites and seabirds are an attractive model due to their peculiar traits. Feather mites are permanent ectosymbionts and considered highly host-specific with limited dispersal abilities. Seabirds harbour species-rich feather mite communities and their colonial breeding provides opportunities for symbionts to exploit several host species. To unravel the richness and test the influence of host phylogeny and geographic distance on mite communities, we collected feather mites from 11 seabird species breeding across the Atlantic Ocean and Mediterranean Sea. Using morphological criteria, we identified 33 mite species, of which 17 were new or recently described species. Based on community similarity analyses, mite communities were clearly structured by host genera, while the effect of geography within host genera or species was weak and sometimes negligible. We found a weak but significant effect of geographic distance on similarity patterns in mite communities for Cory’s shearwaters Calonectris borealis. Feather mite specificity mainly occurred at the host-genus rather than at host-species level, suggesting that previously inferred host species-specificity may have resulted from poorly sampling closely related host species. Overall, our results show that host phylogeny plays a greater role than geography in determining the composition and structure of mite assemblages and pinpoints the importance of sampling mites from closely-related host species before describing mite specificity patterns.
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    Subsea permafrost organic carbon stocks are large and of dominantly low reactivity (2023)
    Springer Nature
    In:  EPIC3Scientific Reports, Springer Nature, 13(1), pp. 9425-, ISSN: 2045-2322
    Details
    Publication Date: 2024-05-07
    Description: Subsea permafrost carbon pools below the Arctic shelf seas are a major unknown in the global carbon cycle. We combine a numerical model of sedimentation and permafrost evolution with simplified carbon turnover to estimate accumulation and microbial decomposition of organic matter on the pan-Arctic shelf over the past four glacial cycles. We find that Arctic shelf permafrost is a globally important long-term carbon sink storing 2822 (1518–4982) Pg OC, double the amount stored in lowland permafrost. Although currently thawing, prior microbial decomposition and organic matter aging limit decomposition rates to less than 48 Tg OC/yr (25–85) constraining emissions due to thaw and suggesting that the large permafrost shelf carbon pool is largely insensitive to thaw. We identify an urgent need to reduce uncertainty in rates of microbial decomposition of organic matter in cold and saline subaquatic environments. Large emissions of methane more likely derive from older and deeper sources than from organic matter in thawing permafrost.
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    Alkalinity responses to climate warming destabilise the Earth’s thermostat (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), pp. 1648-1648, ISSN: 2041-1723
    Details
    Publication Date: 2024-05-07
    Description: Alkalinity generation from rock weathering modulates Earth’s climate at geological time scales. Although lithology is thought to dominantly control alkalinity generation globally, the role of other first-order controls appears elusive. Particularly challenging remains the discrimination of climatic and erosional influences. Based on global observations, here we uncover the role of erosion rate in governing riverine alkalinity, accompanied by areal proportion of carbonate, mean annual temperature, catchment area, and soil regolith thickness. We show that the weathering flux to the ocean will be significantly altered by climate warming as early as 2100, by up to 68% depending on the environmental conditions, constituting a sudden feedback of ocean CO2 sequestration to climate. Interestingly, warming under a low-emissions scenario will reduce terrestrial alkalinity flux from mid-latitudes (–1.6 t(bicarbonate) a−1 km−2) until the end of the century, resulting in a reduction in CO2 sequestration, but an increase (+0.5 t(bicarbonate) a−1 km−2) from mid-latitudes is likely under a high-emissions scenario, yielding an additional CO2 sink.
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    Helicopter-borne RGB orthomosaics and photogrammetric digital elevation models from the MOSAiC Expedition (2023)
    Springer Nature
    In:  EPIC3Scientific Data, Springer Nature, 10(1), pp. 426-426, ISSN: 2052-4463
    Details
    Publication Date: 2024-05-06
    Description: The Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition took place between October 2019 and September 2020 giving the rare opportunity to monitor sea-ice properties over a full annual cycle. Here we present 24 high-resolution orthomosaics and 14 photogrammetric digital elevation models of the sea-ice surface around the icebreaker RV Polarstern between March and September 2020. The dataset is based on 〉34.000 images acquired by a helicopter-borne optical camera system with survey flights covering areas between 1.8 and 96.5 km2 around the vessel. Depending on the flight pattern and altitude of the helicopter, ground resolutions of the orthomosaics range between 0.03 and 0.5 m. By combining the photogrammetric products with contemporaneously acquired airborne laser scanner reflectance measurements selected orthomosaics could be corrected for cloud shadows which facilitates their usage for sea-ice and melt pond classification algorithms. The presented dataset is a valuable data source for the interdisciplinary MOSAiC community building a temporal and spatially resolved baseline to accompany various remote sensing and in situ research projects.
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  • 86
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    Rapid Laurentide Ice Sheet growth preceding the Last Glacial Maximum due to summer snowfall (2024)
    Springer Nature
    In:  EPIC3Nature Geoscience, Springer Nature, pp. 1-10, ISSN: 1752-0894
    Details
    Publication Date: 2024-05-06
    Description: There has been extensive research into the nonlinear responses of the Earth system to astronomical forcing during the last glacial cycle. However, the speed and spatial geometry of ice sheet expansion to its largest extent at the Last Glacial Maximum 21 thousand years ago remains uncertain. Here we use an Earth system model with interactive ice sheets to show that distinct initial North American (Laurentide) ice sheets at 38 thousand years ago converge towards a configuration consistent with the Last Glacial Maximum due to feedbacks between atmospheric circulation and ice sheet geometry. Notably, ice advance speed and spatial pattern in our model are controlled by the amount of summer snowfall, which is dependent on moisture transport pathways from the North Atlantic warm pool linked to ice sheet geometry. The consequence of increased summer snowfall on the surface mass balance of the ice sheet is not only the direct increase in accumulation but the indirect reduction in melt through the snow/ice–albedo feedback. These feedbacks provide an effective mechanism for ice growth for a range of initial ice sheet states and may explain the rapid North American ice volume increase during the last ice age and potentially driving growth during previous glacial periods.
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  • 87
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    Incorporating mesopelagic fish into the evaluation of conservation areas for marine living resources under climate change scenarios (2023)
    Springer Nature
    In:  EPIC3Marine Life Science & Technology, Springer Nature, pp. 1-16, ISSN: 2096-6490
    Details
    Publication Date: 2024-04-24
    Description: Mesopelagic fish (meso-fish) are central species within the Southern Ocean (SO). However, their ecosystem role and adaptive capacity to climate change are rarely integrated into marine protected area (MPAs) assessments. This is a pity given their importance as crucial prey and predators in food webs, coupled with the impacts of climate change. Here, we estimate the habitat distribution of nine meso-fish using an ensemble model approach (MAXENT, random forest, and boosted regression tree). Four climate model simulations were used to project their distribution under two representative concentration pathways (RCP4.5 and RCP8.5) for short-term (2006–2055) and long-term (2050–2099) periods. In addition, we assess the ecological representativeness of established and proposed MPAs under climate change scenarios using meso-fish as indicator species. Our models show that all species shift poleward in the future. Lanternfishes (family Myctophidae) are predicted to migrate poleward more than other families (Paralepididae, Nototheniidae, Bathylagidae, and Gonostomatidae). In comparison, lanternfishes were projected to increase habitat area in the eastern SO but lose area in the western SO; the opposite was projected for species in other families. Important areas (IAs) of meso-fish are mainly distributed near the Antarctic Peninsula and East Antarctica. Proposed MPAs cover 23% of IAs at present and 38% of IAs in the future (RCP8.5, long-term future). Many IAs of meso-fish still need to be included in MPA proposals, such as the Prydz Bay and the seas around the Antarctic Peninsula. Our results provide a framework for designing new MPAs incorporating climate change adaptation strategies for MPA management.
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    Tectono‐Stratigraphic Evolution of the Kerguelen Large Igneous Province: The Conjugate William’s Ridge‐Broken Ridge Rifted Margins (2024)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), 129(3), ISSN: 2169-9313
    Details
    Publication Date: 2024-04-24
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Extensive investigation of continental rift systems has been fundamental for advancing the understanding of extensional tectonics and modes of formation of new ocean basins. However, current rift classification schemes do not account for conjugate end members formed by Large Igneous Province crust, referring to thick mafic crust, sometimes including continental fragments. Here, we investigate the rifting of William's Ridge (Kerguelen Plateau) and Broken Ridge, components of the Kerguelen Large Igneous Province now situated in the Southeast Indian Ocean, and incorporate these end members into the deformation migration concept for rifted margins. We use multichannel seismic reflection profiles and data from scientific drill cores acquired on both conjugate margins to propose, for the first time, a combined tectono‐stratigraphic framework. We interpret seismic patterns, tectonic features, and magnetic anomaly picks to determine an across‐strike structural domain classification. This interpretation considers the rift system overall to be “magma‐poor” despite being located proximal to the Kerguelen plume but suggests that syn‐rift interaction between the Kerguelen mantle plume and the lithospheric structure of William's Ridge and Broken Ridge has controlled the along‐strike segmentation of both conjugates. We integrate seismic reflection and bathymetric data to test the hypothesis of predominantly transform motion, between the Australian and Antarctic plates, in Late Cretaceous and Paleogene time.〈/jats:p〉
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    Structure and Seasonal Variability of the Arctic Boundary Current North of Severnaya Zemlya (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research - Oceans, American Geophysical Union (AGU), 128(1), ISSN: 2169-9275
    Details
    Publication Date: 2024-05-08
    Description: We assessed the spatial and temporal variability of the Arctic Boundary Current (ABC) using seven oceanographic moorings, deployed across the continental slope north of Severnaya Zemlya in 2015–2018. Transports and individual water masses were quantified based on temperature and salinity recorders and current profilers. Our results were compared with observations from the northeast Svalbard and the central Laptev Sea continental slopes to evaluate the hydrographic transformation along the ABC pathway. The highest velocities (〉0.30 m s−1) of the ABC occurred at the upper continental slope and decreased offshore to below 0.03 m s−1 in the deep basin. The ABC showed seasonal variability with velocities two times higher in winter than in summer. Compared to upstream conditions in Svalbard, water mass distribution changed significantly within 20 km of the shelf edge due to mixing with- and intrusion of shelf waters. The ABC transported 4.15 ± 0.3 Sv in the depth range 50–1,000 m, where 0.88 ± 0.1, 1.5 ± 0.2, 0.61 ± 0.1 and 1.0 ± 0.15 Sv corresponded to Atlantic Water (AW), Dense Atlantic Water (DAW), Barents Sea Branch Water (BSBW) and Transformed Atlantic Water (TAW). 62–70% of transport was constrained to within 30–40 km of the shelf edge, and beyond 84 km, transport increases were estimated to be 0.54 Sv. Seasonality of TAW derived from local shelf-processes and advection of seasonal-variable Fram Strait waters, while BSBW transport variability was dominated by temperature changes with maximum transport coinciding with minimum temperatures. Further Barents Sea warming will likely reduce TAW and BSBW transport leading to warmer conditions along the ABC pathway.
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    Moisture Sources and Pathways Determine Stable Isotope Signature of Himalayan Waters in Nepal (2023)
    American Geophysical Union (AGU)
    In:  EPIC3AGU Advances, American Geophysical Union (AGU), 4(1), ISSN: 2576-604X
    Details
    Publication Date: 2024-05-08
    Description: The Himalayan mountain range produces one of the steepest and largest rainfall gradients on Earth, with 〉3 m/yr rainfall difference over a ∼100 km distance. The Indian Summer Monsoon (ISM) contributes more than 80% to the annual precipitation budget of the central Himalayas. The remaining 20% falls mainly during pre-ISM season. Understanding the seasonal cycle and the transfer pathways of moisture from precipitation to the rivers is crucial for constraining water availability in a warming climate. However, the partitioning of moisture into the different storage systems such as snow, glacier, and groundwater and their relative contribution to river discharge throughout the year remains under-constrained. Here, we present novel field data from the Kali Gandaki, a trans-Himalayan river, and use 4-year time series of river and rain water stable isotope composition (δ18O and δ2H values) as well as river discharge, satellite Global Precipitation Measurement amounts, and moisture source trajectories to constrain hydrological variability. We find that rainfall before the onset of the ISM is isotopically distinct and that ISM rain and groundwater have similar isotopic values. Our study lays the groundwork for using isotopic measurements to track changes in precipitation sources during the pre-ISM to ISM transition in this key region of orographic precipitation. Specifically, we highlight the role of pre-ISM precipitation, derived from the Gangetic plain, to define the seasonal river isotopic variability across the central Himalayas. Lastly, isotopic values across the catchment document the importance of a large well-mixed groundwater reservoir supplying river discharge, especially during the non-ISM season.
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    Author Correction: Annual cycle observations of aerosols capable of ice formation in central Arctic clouds (2022)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 13(1), pp. 6010-6010, ISSN: 2041-1723
    Details
    Publication Date: 2024-05-08
    Description: The original version of this Article contained an error in Fig. 4, in which the y-axis should read “INPs (L−1 of air)” instead of “INPs x 10−3 (L−1 of air)”. This has been corrected in both the PDF and HTML versions of the Article.
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  • 92
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    Tidal dissipation from free drift sea ice in the Barents Sea assessed using GNSS beacon observations (2022)
    Springer Nature
    In:  EPIC3Ocean Dynamics, Springer Nature, 72(8), pp. 577-597, ISSN: 1616-7341
    Details
    Publication Date: 2024-05-08
    Description: One of the major challenges facing global hydrodynamic tidal models is the modelling of the interaction between sea ice and tides in high-latitude waters. Recent studies have shown strong seasonal correlation between sea ice and tides. Hence, it is important to accurately model the effect of sea ice in a tidal model. Presence of sea ice leads to a frictional dissipation of tides. Most models either completely ignore sea ice or partly include it by assuming a fixed sea ice cover (landfast ice). However, sea ice can also be drifting and the nature of dissipation between drifting sea ice and tides is partly unknown. We assess the dissipation of tides due to free drift sea ice. In the absence of wind, this is negligible in the deeper and open ocean. For the shallow water regions, however, this dissipation is unknown. Here, we evaluate this dissipation for the Spitzbergen Shelf region using a beacon dataset showing strong free drift subdaily sea ice oscillations and a physics based point ice model. Two analyses were done which compared the model and observed motion. The analyses showed that for winds speeds below 8m/s and with low subdaily signals, the subdaily free drift sea ice motion is strongly connected to the tides and that the frictional dissipation is low. In the context of global tide and storm surge models, the dissipation from free drift sea ice on tides should be evaluated based on the region (deep ocean or shallow water) and existing wind conditions. In the presence of strong winds the dissipation between free drift sea ice and air can be significant on a subdaily scale even if there are no subdaily signals in the wind itself.
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    Transiting consolidated ice strongly influenced polynya area during a shrink event in Terra Nova Bay in 2013 (2023)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 4(1), pp. 54-54, ISSN: 2662-4435
    Details
    Publication Date: 2024-05-08
    Description: Coastal polynyas in Antarctica are a window of air-sea energy exchange and an important source of Antarctic Bottom Water production. However, the relationship between the polynya area variation and the surrounding marine environment is yet to be fully understood. Here we quantify the influence of the volume of transiting consolidated ice on the Terra Nova Bay Polynya area with ice thickness data. Changes in transiting consolidated ice volume are shown to dominate the evolution and variation of the polynya during a typical polynya shrinking event that occurred between 19 June to 03 July, 2013, rather than katabatic winds or air temperature, which are commonly assumed to be the main drivers. Over the cold seasons from 2013 to 2020, the Terra Nova Bay Polynya area is highly correlated to the transiting consolidated ice volume. We demonstrate that thick transiting ice limits the polynya area by blocking the newly-formed sea ice from leaving.
    Repository Name: EPIC Alfred Wegener Institut
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  • 94
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    The Marginal Ice Zone as a dominant source region of atmospheric mercury during central Arctic summertime (2023)
    Springer Nature
    In:  EPIC3Nature Communications, Springer Nature, 14(1), pp. 4887-4887, ISSN: 2041-1723
    Details
    Publication Date: 2024-05-08
    Description: Atmospheric gaseous elemental mercury (GEM) concentrations in the Arctic exhibit a clear summertime maximum, while the origin of this peak is still a matter of debate in the community. Based on summertime observations during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition and a modeling approach, we further investigate the sources of atmospheric Hg in the central Arctic. Simulations with a generalized additive model (GAM) show that long-range transport of anthropogenic and terrestrial Hg from lower latitudes is a minor contribution (~2%), and more than 50% of the explained GEM variability is caused by oceanic evasion. A potential source contribution function (PSCF) analysis further shows that oceanic evasion is not significant throughout the ice-covered central Arctic Ocean but mainly occurs in the Marginal Ice Zone (MIZ) due to the specific environmental conditions in that region. Our results suggest that this regional process could be the leading contributor to the observed summertime GEM maximum. In the context of rapid Arctic warming and the observed increase in width of the MIZ, oceanic Hg evasion may become more significant and strengthen the role of the central Arctic Ocean as a summertime source of atmospheric Hg.
    Repository Name: EPIC Alfred Wegener Institut
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  • 95
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    The Southern Ocean Carbon Cycle 1985–2018: Mean, Seasonal Cycle, Trends, and Storage (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Global Biogeochemical Cycles, American Geophysical Union (AGU), 37(11), ISSN: 0886-6236
    Details
    Publication Date: 2023-12-20
    Description: We assess the Southern Ocean CO2 uptake (1985–2018) using data sets gathered in the REgional Carbon Cycle Assessment and Processes Project Phase 2. The Southern Ocean acted as a sink for CO2 with close agreement between simulation results from global ocean biogeochemistry models (GOBMs, 0.75 ± 0.28 PgC yr−1) and pCO2-observation-based products (0.73 ± 0.07 PgC yr−1). This sink is only half that reported by RECCAP1 for the same region and timeframe. The present-day net uptake is to first order a response to rising atmospheric CO2, driving large amounts of anthropogenic CO2 (Cant) into the ocean, thereby overcompensating the loss of natural CO2 to the atmosphere. An apparent knowledge gap is the increase of the sink since 2000, with pCO2-products suggesting a growth that is more than twice as strong and uncertain as that of GOBMs (0.26 ± 0.06 and 0.11 ± 0.03 Pg C yr−1 decade−1, respectively). This is despite nearly identical pCO2 trends in GOBMs and pCO2-products when both products are compared only at the locations where pCO2 was measured. Seasonal analyses revealed agreement in driving processes in winter with uncertainty in the magnitude of outgassing, whereas discrepancies are more fundamental in summer, when GOBMs exhibit difficulties in simulating the effects of the non-thermal processes of biology and mixing/circulation. Ocean interior accumulation of Cant points to an underestimate of Cant uptake and storage in GOBMs. Future work needs to link surface fluxes and interior ocean transport, build long overdue systematic observation networks and push toward better process understanding of drivers of the carbon cycle.
    Repository Name: EPIC Alfred Wegener Institut
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  • 96
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    Harnessing the microbiome to prevent global biodiversity loss (2022)
    Springer Nature
    In:  EPIC3Nature Microbiology, Springer Nature, 7(11), pp. 1726-1735, ISSN: 2058-5276
    Details
    Publication Date: 2024-01-02
    Description: Global biodiversity loss and mass extinction of species are two of the most critical environmental issues the world is currently facing, resulting in the disruption of various ecosystems central to environmental functions and human health. Microbiome-targeted interventions, such as probiotics and microbiome transplants, are emerging as potential options to reverse deterioration of biodiversity and increase the resilience of wildlife and ecosystems. However, the implementation of these interventions is urgently needed. We summarize the current concepts, bottlenecks and ethical aspects encompassing the careful and responsible management of ecosystem resources using the microbiome (termed microbiome stewardship) to rehabilitate organisms and ecosystem functions. We propose a real-world application framework to guide environmental and wildlife probiotic applications. This framework details steps that must be taken in the upscaling process while weighing risks against the high toll of inaction. In doing so, we draw parallels with other aspects of contemporary science moving swiftly in the face of urgent global challenges.
    Repository Name: EPIC Alfred Wegener Institut
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  • 97
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    Subsurface warming in the Antarctica’s Weddell Sea can be avoided by reaching the 2∘C warming target (2024)
    Springer Nature
    In:  EPIC3Communications Earth & Environment, Springer Nature, 5(1), pp. 93-93, ISSN: 2662-4435
    Details
    Publication Date: 2024-04-03
    Description: Recently, seasonal pulses of modified Warm Deep Water have been observed near the Filchner Ice Shelf front in the Weddell Sea, Antarctica. Here, we investigate the temperature evolution of subsurface waters in the Filchner Trough under four future scenarios of carbon dioxide emissions using the climate model AWI-CM. Our model simulates these warm intrusions, suggests more frequent pulses in a warmer climate, and supports the potential for a regime shift from cold to warm Filchner Trough in two high-emission scenarios. The regime shift is governed in particular by decreasing local sea ice formation and a shoaling thermocline. Cavity circulation is not critical in triggering the change. Consequences would include increased ice shelf basal melting, reduced buttressing of fast-flowing ice streams, loss of grounded ice and an acceleration of global sea level rise. According to our simulations, the regime shift can be avoided and the Filchner Trough warming can be restricted to 0.5 ∘C by reaching the 2 ∘C climate goal.
    Repository Name: EPIC Alfred Wegener Institut
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  • 98
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    Metabolic independence drives gut microbial colonization and resilience in health and disease (2023)
    Springer Nature
    In:  EPIC3Genome Biology, Springer Nature, 24(1), pp. 78-78, ISSN: 1474-760X
    Details
    Publication Date: 2024-04-03
    Description: Background: Changes in microbial community composition as a function of human health and disease states have sparked remarkable interest in the human gut microbiome. However, establishing reproducible insights into the determinants of microbial succession in disease has been a formidable challenge. Results: Here we use fecal microbiota transplantation (FMT) as an in natura experimental model to investigate the association between metabolic independence and resilience in stressed gut environments. Our genome-resolved metagenomics survey suggests that FMT serves as an environmental filter that favors populations with higher metabolic independence, the genomes of which encode complete metabolic modules to synthesize critical metabolites, including amino acids, nucleotides, and vitamins. Interestingly, we observe higher completion of the same biosynthetic pathways in microbes enriched in IBD patients. Conclusions: These observations suggest a general mechanism that underlies changes in diversity in perturbed gut environments and reveal taxon-independent markers of “dysbiosis” that may explain why widespread yet typically low-abundance members of healthy gut microbiomes can dominate under inflammatory conditions without any causal association with disease.
    Repository Name: EPIC Alfred Wegener Institut
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  • 99
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    Microbial metabolites in the marine carbon cycle (2022)
    Springer Nature
    In:  EPIC3Nature Microbiology, Springer Nature, 7(4), pp. 508-523, ISSN: 2058-5276
    Details
    Publication Date: 2024-04-03
    Description: One-quarter of photosynthesis-derived carbon on Earth rapidly cycles through a set of short-lived seawater metabolites that are generated from the activities of marine phytoplankton, bacteria, grazers and viruses. Here we discuss the sources of microbial metabolites in the surface ocean, their roles in ecology and biogeochemistry, and approaches that can be used to analyse them from chemistry, biology, modelling and data science. Although microbial-derived metabolites account for only a minor fraction of the total reservoir of marine dissolved organic carbon, their flux and fate underpins the central role of the ocean in sustaining life on Earth.
    Repository Name: EPIC Alfred Wegener Institut
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    Diverse plasmid systems and their ecology across human gut metagenomes revealed by PlasX and MobMess (2024)
    Springer Nature
    In:  EPIC3Nature Microbiology, Springer Nature, 9(3), pp. 830-847, ISSN: 2058-5276
    Details
    Publication Date: 2024-04-03
    Description: Plasmids alter microbial evolution and lifestyles by mobilizing genes that often confer fitness in changing environments across clades. Yet our ecological and evolutionary understanding of naturally occurring plasmids is far from complete. Here we developed a machine-learning model, PlasX, which identified 68,350 non-redundant plasmids across human gut metagenomes and organized them into 1,169 evolutionarily cohesive ‘plasmid systems’ using our sequence containment-aware network-partitioning algorithm, MobMess. Individual plasmids were often country specific, yet most plasmid systems spanned across geographically distinct human populations. Cargo genes in plasmid systems included well-known determinants of fitness, such as antibiotic resistance, but also many others including enzymes involved in the biosynthesis of essential nutrients and modification of transfer RNAs, revealing a wide repertoire of likely fitness determinants in complex environments. Our study introduces computational tools to recognize and organize plasmids, and uncovers the ecological and evolutionary patterns of diverse plasmids in naturally occurring habitats through plasmid systems.
    Repository Name: EPIC Alfred Wegener Institut
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