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  • 1
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    Multiple Angle Observations Would Benefit Visible Band Remote Sensing Using Night Lights (2022)
    Details
    Publication Date: 2022-10-05
    Description: The spatial and angular emission patterns of artificial and natural light emitted, scattered, and reflected from the Earth at night are far more complex than those for scattered and reflected solar radiation during daytime. In this commentary, we use examples to show that there is additional information contained in the angular distribution of emitted light. We argue that this information could be used to improve existing remote sensing retrievals based on night lights, and in some cases could make entirely new remote sensing analyses possible. This work will be challenging, so we hope this article will encourage researchers and funding agencies to pursue further study of how multi‐angle views can be analyzed or acquired.
    Description: Plain Language Summary: When satellites take images of Earth, they usually do so from directly above (or as close to it as is reasonably possible). In this comment, we show that for studies that use imagery of Earth at night, it may be beneficial to take several images of the same area at different angles within a short period of time. For example, different types of lights shine in different directions (street lights usually shine down, while video advertisements shine sideways), and tall buildings can block the view of a street from some viewing angles. Additionally, since views from different directions pass through different amounts of air, imagery at multiple angles could be used to obtain information about Earth's atmosphere, and measure artificial and natural night sky brightness. The main point of the paper is to encourage researchers, funding agencies, and space agencies to think about what new possibilities could be achieved in the future with views of night lights at different angles.
    Description: Key Points: Remote sensing using the visible band at night is more complex than during the daytime, especially due to the variety of artificial lights. Views of night lights intentionally taken from multiple angles provide several advantages over near‐nadir or circumstantial view geometries. Night lights remote sensing would benefit from greater consideration of the role viewing geometry plays in the observed radiance.
    Description: EC H2020 H2020 Societal Challenges http://dx.doi.org/10.13039/100010676
    Description: Helmholtz Association http://dx.doi.org/10.13039/501100009318
    Description: Slovak Research and Development Agency
    Description: Xunta de Galicia (Regional Government of Galicia) http://dx.doi.org/10.13039/501100010801
    Description: National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104
    Description: University of Hong Kong http://dx.doi.org/10.13039/501100003803
    Description: Fonds de recherche du Québec
    Description: EC Emprego, Assuntos Sociais e Inclusão European Social Fund http://dx.doi.org/10.13039/501100004895
    Description: Natural Environment Research Council http://dx.doi.org/10.13039/501100000270
    Description: City of Cologne, Germany
    Keywords: ddc:551.5
    Language: English
    Type: doc-type:article
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  • 2
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    Co-limitation towards lower latitudes shapes global forest diversity gradients (2022)
    In:  Nature Ecology & Evolution
    Details
    Publication Date: 2022-11-18
    Description: The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.
    Type: info:eu-repo/semantics/article
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  • 3
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    Robust approaches for model‐free small‐angle scattering data analysis (2022)
    Bender, Philipp ; Honecker, Dirk ; Bersweiler, Mathias ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-10-04
    Description: The small‐angle neutron scattering data of nanostructured magnetic samples contain information regarding their chemical and magnetic properties. Often, the first step to access characteristic magnetic and structural length scales is a model‐free investigation. However, due to measurement uncertainties and a restricted q range, a direct Fourier transform usually fails and results in ambiguous distributions. To circumvent these problems, different methods have been introduced to derive regularized, more stable correlation functions, with the indirect Fourier transform being the most prominent approach. Here, the indirect Fourier transform is compared with the singular value decomposition and an iterative algorithm. These approaches are used to determine the correlation function from magnetic small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles; it is shown that with all three methods, in principle, the same correlation function can be derived. Each method has certain advantages and disadvantages, and thus the recommendation is to combine these three approaches to obtain robust results.
    Description: Three different approaches are compared for determination of the correlation function from the small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles.
    Keywords: ddc:548
    Language: English
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  • 4
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    Imaging the Absorbing Feeding and Eruptive Pathways of Deception Island, Antarctica (2022)
    Details
    Publication Date: 2022-12-10
    Description: Deception Island is one of the most active and best‐documented volcanoes in Antarctica. Since its last eruption in 1970, several geophysical surveys have targeted reconstructing its magmatic systems. However, geophysics fails to reconstruct the pathways magma and fluids follow from depth to erupt at the surface. Here, novel data selection strategies and multi‐frequency absorption inversions have been framed in a Geographical Information System, using all available geological (vents and faults distribution), geochemical and geophysical knowledge of the volcano. The result is the detection of these eruptive pathways. The model offers the first image of the magma and associated fluids pathways feed the 1967, 1969, and 1970 eruptions. Results suggest that future ascending paths might lead to active research bases and zones of planned helicopter rescue. The connection between seismic absorption, temperature, and fluid content makes it a promising attribute for detecting and monitoring eruptions at active calderas.
    Description: Plain Language Summary: Deception Island is the gateway for tourists to Antarctica and a laboratory to understand ice‐capped volcanoes and their eruptions. While the Island has been the target of many geophysical studies, no clear tomographic model shows how deep eruptive pathways of its last eruptions have reached the surface in the 1960s and 1970s. This is a recurrent topic in volcano geophysics: dikes and fluid migrations develop across structures considered too small to be detected by tomographic techniques. This paper demonstrates that seismic absorption has sufficient sensitivity to temperature and fluid content to detect these pathways. Once integrated within a Geographical Information System with all the information we have on the volcano, the models resolve the feeding systems of these eruptions, from a tectonically deformed deep magma chamber to shallow cold dyke intrusions and fluid migrations still feeding the volcano today. The correlation between seismic absorption, temperature, and fluid content offers a new tool for detecting and monitoring shallow volcanic hazards.
    Description: Key Points: High absorption detects deep eruptive pathways from the caldera center to its rim. Absorption imaging reconstructs shallow pathways of hazardous materials. Seismic absorption is sensitive to thermal anomalies at depth.
    Description: https://doi.org/10.5281/zenodo.6561124
    Description: https://zenodo.org/badge/latestdoi/493744216
    Keywords: ddc:551 ; seismic absorption ; seismic tomography ; Deception Island ; Volcanology ; remote sensing
    Language: English
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  • 5
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    Curie Temperatures and Emplacement Conditions of Pyroclastic Deposits From Popocatépetl Volcano, Mexico (2022)
    Details
    Publication Date: 2022-12-15
    Description: Most pyroclastic deposits of Popocatépetl volcano were emplaced at high temperatures and have similar mafic to more evolved compositions, suggesting a long‐lived, interconnected magma environment. We performed a magnetic and microscopic study on different eruptive sequences 〈14 ky in age and found that temperature and field dependence of magnetic susceptibility are suited to separate eruption phases. We observed homogeneous titanomagnetite with Curie temperatures (TC) of 50–200°C and 200–400°C, together with different amounts of oxy‐exsolved titanomagnetite with TC ∼ 570°C. Some block‐and‐ash flow deposits show remarkably irreversible TC in heating and cooling branches with a positive ΔTC (TC heating–TC cooling) of up to 130°C in the center. The central part of this sequence is characterized by decreasing magnetic susceptibility and low field dependence of magnetic susceptibility (〈10%), which is atypical for ulvöspinel‐rich titanomagnetite. The nonreversibility of heating and cooling runs measured with rates of around 10 K/min is probably related to vacancy‐enhanced nanoscale chemical clustering, which seems to occur preferentially during rapid quenching, possibly combined with subtle maghemitization. In contrast, pumice layers have the highest field dependence (∼20%) and contain Ti‐rich and intermediate titanomagnetite with TC 〈 100 and ∼300°C, which are in line with mafic and more evolved magma composition. In intermediate phases, irreversibility of TC is more common but with a relatively low ΔTC of ±20°C. We suggest that magneto‐mineralogy in pyroclastic density currents is complex but offers a complementary tool to the paleomagnetic directional analysis for emplacement temperature and contribute information on the volcanic material history and their emplacement conditions.
    Description: Plain Language Summary: Explosive eruptions of volcanoes are a dangerous threat to human settlements. In this study, we investigated pyroclastic material from the last 14 ky of Popocatépetl volcano using magnetic mineral assemblages, hysteresis properties, and temperature‐ and field‐dependent magnetic susceptibility. The data are suited to separate different eruption phases and provide information on the volcanic material history and emplacement conditions. Magnetic susceptibility analyses are suggested to be a complementary tool to the paleomagnetic directional analysis for the determination of emplacement temperatures.
    Description: Key Points: Several Curie temperatures were observed in pyroclastic deposits. Temperature and field dependence of magnetic susceptibility are suited to separate eruption phases. Irreversible Curie temperatures in heating and cooling curves observed in block‐and‐ash flows may suggest rapid quenching.
    Description: DGAPA‐UNAM
    Description: https://doi.org/10.17632/9g2tszftvr.2
    Description: https://earthref.org/MagIC/19591/206809c5-acfc-41e3-b4cb-411630a7025e
    Keywords: ddc:552.2 ; Popocatépetl volcano ; pyroclastic deposits ; magnetic rock studies ; magnetic mineralogy studies ; cooling temerature
    Language: English
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  • 6
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    Intra-annual relationship between precipitation and forest disturbance in the African rainforest (2022)
    In:  Environmental Research Letters
    Details
    Publication Date: 2022-05-17
    Description: Analysis of forest disturbance patterns in relation to precipitation seasonality is important for understanding African tropical forest dynamics under changing climate conditions and different levels of human activities. Newly available radar-based forest disturbance information now enables an investigation of the intra-annual relationship between precipitation and forest disturbance in a spatially and temporally explicit manner, especially in the tropics, where frequent cloud cover hinders the use of optical-based remote sensing products. In this study, we applied cross-correlation on monthly precipitation and forest disturbance time series for 2019 and 2020 at a 0.5° grid in the African rainforest. We used the magnitude of the correlation and time lag to assess the intra-annual relationship between precipitation and forest disturbance, and introduced accessibility proxies to analyse the spatial variation of the relationship. Results revealed that a significant negative correlation between forest disturbance and precipitation dominates the study region. We found that significant negative correlations appear on average closer to settlements with overall smaller variations in travel time to settlements compared to grid cells with non-significant and significant positive correlation. The magnitude of the negative correlation increases as the travel time to settlements increases, implying that forest disturbances in less accessible areas are more affected by precipitation seasonality and that in particular human-induced disturbance activities are predominantly carried out in the drier months. Few areas showed a significant positive correlation, mainly resulting from natural causes such as flooding. These new insights in the interaction between forest disturbance, precipitation and accessibility provide a step forward in understanding the complex interactions that underlie the complexity of forest loss patterns that we can increasingly capture with Earth Observation approaches. As such, they can support forest conservation and management in coping with climate change induced changes of precipitation patterns in African rainforest countries.
    Type: info:eu-repo/semantics/article
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  • 7
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    Fundamental Science and Engineering Questions in Planetary Cave Exploration (2022)
    In:  Journal of Geophysical Research: Planets
    Details
    Publication Date: 2022-12-09
    Description: Nearly half a century ago, two papers postulated the likelihood of lunar lava tube caves using mathematical models. Today, armed with an array of orbiting and fly-by satellites and survey instrumentation, we have now acquired cave data across our solar system—including the identification of potential cave entrances on the Moon, Mars, and at least nine other planetary bodies. These discoveries gave rise to the study of planetary caves. To help advance this field, we leveraged the expertise of an interdisciplinary group to identify a strategy to explore caves beyond Earth. Focusing primarily on astrobiology, the cave environment, geology, robotics, instrumentation, and human exploration, our goal was to produce a framework to guide this subdiscipline through at least the next decade. To do this, we first assembled a list of 198 science and engineering questions. Then, through a series of social surveys, 114 scientists and engineers winnowed down the list to the top 53 highest priority questions. This exercise resulted in identifying emerging and crucial research areas that require robust development to ultimately support a robotic mission to a planetary cave— principally the Moon and/or Mars. With the necessary financial investment and institutional support, the research and technological development required to achieve these necessary advancements over the next decade are attainable. Subsequently, we will be positioned to robotically examine lunar caves and search for evidence of life within Martian caves; in turn, this will set the stage for human exploration and potential habitation of both the lunar and Martian subsurface.
    Type: info:eu-repo/semantics/article
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  • 8
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    MarineMetagenomeDB: a public repository for curated and standardized metadata for marine metagenomes (2022)
    In:  Environmental Microbiome
    Details
    Publication Date: 2022-11-24
    Description: Metagenomics is an expanding field within microbial ecology, microbiology, and related disciplines. The number of metagenomes deposited in major public repositories such as Sequence Read Archive (SRA) and Metagenomic Rapid Annotations using Subsystems Technology (MG-RAST) is rising exponentially. However, data mining and interpretation can be challenging due to mis-annotated and misleading metadata entries. In this study, we describe the Marine Metagenome Metadata Database (MarineMetagenomeDB) to help researchers identify marine metagenomes of interest for re-analysis and meta-analysis. To this end, we have manually curated the associated metadata of several thousands of microbial metagenomes currently deposited at SRA and MG-RAST.
    Type: info:eu-repo/semantics/article
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  • 9
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    Biosignature stability in space enables their use for life detection on Mars (2022)
    In:  Science Advances
    Details
    Publication Date: 2022-09-29
    Description: Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, among other instruments, Raman spectrometers. However, there are many unknowns about the stability of Raman-detectable biomolecules in the martian environment, clouding the interpretation of the results. To quantify Raman-detectable biomolecule stability, we exposed seven biomolecules for 469 days to a simulated martian environment outside the International Space Station. Ultraviolet radiation (UVR) strongly changed the Raman spectra signals, but only minor change was observed when samples were shielded from UVR. These findings provide support for Mars mission operations searching for biosignatures in the subsurface. This experiment demonstrates the detectability of biomolecules by Raman spectroscopy in Mars regolith analogs after space exposure and lays the groundwork for a consolidated space-proven database of spectroscopy biosignatures in targeted environments.
    Type: info:eu-repo/semantics/article
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  • 10
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    Pleistocene depositional environments and links to cryosphere-ocean interactions on the eastern Ross Sea continental slope, Antarctica (IODP Hole U1525A) (2022)
    In:  EPIC3Marine Geology, 443, pp. 106674, ISSN: 00253227
    Details
    Publication Date: 2022-04-12
    Description: The repeated proximity of West Antarctic Ice Sheet (WAIS) ice to the eastern Ross Sea continental shelf break during past ice age cycles has been inferred to directly influence sedimentary processes occurring on the continental slope, such as turbidity current and debris flow activity; thus, the records of these processes can be used to study the past history of the WAIS. Ross Sea slope sediments may additionally provide an archive on the history and interplay of density-driven or geostrophic oceanic bottom currents with ice-sheet-driven depositional mechanisms. We investigate the upper 121 m of Hole U1525A, collected during International Ocean Discovery Program (IODP) Expedition 374 in 2018. Hole U1525A is located on the southwestern external levee of the Hillary Canyon (Ross Sea, Antarctica) and the depositional lobe of the nearby trough-mouth fan. Using core descriptions, grain size analysis, and physical properties datasets, we develop a lithofacies scheme that allows construction of a detailed depositional model and environmental history of past ice sheet-ocean interactions at the eastern Ross Sea continental shelf break/slope since ~2.4 Ma. The earliest Pleistocene interval (~2.4- ~ 1.4 Ma) represents a hemipelagic environment dominated by ice-rafting and reworking/deposition by relatively persistent bottom current activity. Finely interlaminated silty muds with ice-rafted debris (IRD) layers are interpreted as contourites. Between ~1.4 and ~0.8 Ma, geostrophic bottom current activity was weaker and turbiditic processes more common, likely related to the increased proximity of grounded ice at the shelf edge. Silty, normally-graded laminations with sharp bases may be the result of flow-stripped turbidity currents overbanking the canyon levee during periods when ice was grounded at or proximal to the shelf edge. A sandy, IRD- and foraminifera-bearing interval dated to ~1.18 Ma potentially reflects warmer oceanographic conditions and a period of stronger Antarctic Slope Current flow. This may have enhanced upwelling of warm Circumpolar Deep Water onto the shelf, leading to large-scale glacial retreat at that time. The thickest interval of turbidite interlamination was deposited after ~1 Ma, following the onset of the Mid-Pleistocene Transition, interpreted as a time when most ice sheets grew and glacial periods were longer and more extreme. Sedimentation after ~0.8 Ma was dominated by glacigenic debris flow deposition, as the trough mouth fan that dominates the eastern Ross Sea continental slope prograded and expanded over the site. These findings will help to improve estimations of WAIS ice extent in future Ross Sea shelf-based modelling studies, and provide a basis for more detailed analysis of the inception and growth of the WAIS under distinct oceanographic conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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