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  • 1
    Publication Date: 2018-07-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 2
    Publication Date: 2019
    Description: The timing of reproduction is a critical component of how free‐living organisms respond to ongoing climate change, especially in the Arctic, which is disproportionally impacted by climate warming. Arctic seabirds respond to climate change by moving the start of their reproduction earlier, coincident with an advancing onset of spring, but their response is dependent on the ocean basin and foraging strategy. Surface‐feeding species advanced their reproduction in the last 35 years while diving species showed remarkably stable breeding timing. The earlier reproduction for Arctic surface‐feeding birds was significant in the Pacific only, where the spring advancement was most pronounced. Abstract The timing of annual events such as reproduction is a critical component of how free‐living organisms respond to ongoing climate change. This may be especially true in the Arctic, which is disproportionally impacted by climate warming. Here, we show that Arctic seabirds responded to climate change by moving the start of their reproduction earlier, coincident with an advancing onset of spring and that their response is phylogenetically and spatially structured. The phylogenetic signal is likely driven by seabird foraging behavior. Surface‐feeding species advanced their reproduction in the last 35 years while diving species showed remarkably stable breeding timing. The earlier reproduction for Arctic surface‐feeding birds was significant in the Pacific only, where spring advancement was most pronounced. In both the Atlantic and Pacific, seabirds with a long breeding season showed a greater response to the advancement of spring than seabirds with a short breeding season. Our results emphasize that spatial variation, phylogeny, and life history are important considerations in seabird phenological response to climate change and highlight the key role played by the species’ foraging behavior.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 3
    Publication Date: 2016-08-19
    Description: Correlative width-discharge relationships from the Missouri River Basin are commonly used to estimate fluvial paleodischarge on Mars. However, hydraulic geometry provides alternative, and causal, width-discharge relationships derived from broader samples of channels, including those in reduced-gravity (submarine) environments. Comparison of these relationships implies that causal relationships from hydraulic geometry should yield more accurate and more precise discharge estimates. Our remote analysis of a Martian-terrestrial analog channel, combined with in situ discharge data, substantiates this implication. Applied to Martian features, these results imply paleodischarges of interior channels of Noachian-Hesperian (~3.7 Ga) valley networks have been underestimated by a factor of several, whereas paleodischarges for smaller fluvial deposits of the Late Hesperian-Early Amazonian (~3.0 Ga) have been overestimated. Thus, these new paleodischarges significantly magnify the contrast between early and late Martian hydrologic activity. Width-discharge relationships from hydraulic geometry represent validated tools for quantifying fluvial input near candidate landing sites of upcoming missions.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Publication Date: 2016-05-29
    Description: In seasonal environments, organisms are expected to optimally schedule reproduction within an annual range of environmental conditions. Latitudinal gradients generate a range of seasonality to which we can expect adaptations to have evolved, and can be used to explore drivers of timing strategies across species’ distribution ranges. This study compares the timing of egg hatching in four seabird species (Atlantic puffin Fratercula arctica, black-legged kittiwake Rissa tridactyla, common guillemot Uria aalge , and Brünnich's guillemot U. lomvia ) covering a subarctic to Arctic latitudinal gradient along the Norwegian coast to Svalbard (65–79°N). Hatching was significantly delayed by an estimated 1.7, 2.3, and 1.9 d per latitudinal degree for puffins, kittiwakes, and common guillemots, respectively, but was not delayed for Brünnich's guillemots. Hatching distributions revealed an increase in intra-annual breeding synchronicity along a latitudinal gradient for kittiwakes only, whereas the two guillemots exhibited high hatching synchronicity at all colonies. We used this large-scale, multispecies timing data series to discuss constraints, adaptations, and mechanisms affecting breeding timing, a necessary step to recognize risks to populations and predict future ecosystem change.
    Electronic ISSN: 2150-8925
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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  • 5
    Publication Date: 2015-10-20
    Description: According to the properties determined for the ternary end-members, MAX phases in the quaternary Cr–Ti–Al–C system could be of interest as protective coatings for nuclear fuel cladding in the case of severe accident conditions. In this study, syntheses of 211 and 312 MAX phase compositions were attempted using pressureless reactions starting from Cr, TiH 2 , Al, and C (graphite) powders. It was observed that both the Ti substitution by Cr in Ti 3 AlC 2 and the mutual solubility of Ti 2 AlC and Cr 2 AlC are limited to a few atomic percent. In addition, the remarkable stability of the (Cr 2/3 Ti 1/3 ) 3 AlC 2 MAX phase composition was confirmed. Due to the low miscibility of MAX phases in the Cr–Ti–Al–C system, most samples contained substantial amounts of TiC x and Al–Cr alloys as secondary phases, thus forming composite materials. After sintering, all samples were submitted to a single oxidation test (12 h at 1400°C in air) to identify compositions potentially offering high-temperature oxidation resistance and so warranting further investigation. In addition to (Cr 0.95 Ti 0.05 ) 2 AlC, composite samples containing substantial quantities of Al 8 Cr 5 and AlCr 2 formed a stable and passivating Al 2 O 3 scale, whereas the other samples were fully oxidized.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 6
    Publication Date: 2015-01-31
    Description: Reconstructed coral skeletal Pb : Ca and Ba : Ca ratios from the Northern Coast of Lanyu Islet are shown to be sensitive indicators of land–use practices which took place on the islet during the past 30 years. Coral skeletal Pb : Ca and Ba : Ca both increased dramatically. Pb : Ca ratios are very sensitive to biomass burning on Lanyu Islet while Ba : Ca generally respond to rainfall variations except in case of instantaneous flooding. The method presented here provides a quantitative technique for identifying human effects that can be used for coastal land management and offers a way to study the environment during prehistoric times, where no written records are available.
    Print ISSN: 0024-3590
    Electronic ISSN: 1939-5590
    Topics: Biology , Geosciences , Physics
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  • 7
    Publication Date: 2019
    Description: Abstract Historical data provides observational information crucial to our understanding of the evolution of geophysical processes. However, there is a gap between predigital age observations, which are typically handwritten, and data that is discoverable and analysable. The data rescue protocols here address this gap, covering the information lifecycle from handwritten register pages to transcription‐ready content, describing the historical data, the database design for the data rescue, and the development of an application design to transcribe the meteorological information directly from an image file to the database. The preparatory steps necessary to organize, curate, image, and structure the meteorological information, prior to transcribing the historical data, are outlined here in an integrated methodology. The initial organization, the development of an image file nomenclature to link the rescued data to the original source, and the description of a metadata schema to optimize the transcription application are all vital to the process of ensuring traceability and transparency in the data rescue process. Taken together, these steps describe best practices guidelines for similar projects. Although we designed the methodology and application to be used in any data rescue context, our particular concern was to accommodate the needs of citizen scientists. We thus focused on making our application easily maintained, flexible, direct to database, clear, and simple to use. Open Practices This article has earned an Open Data badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://citsci.geog.mcgill.ca. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.
    Electronic ISSN: 2049-6060
    Topics: Geosciences
    Published by Wiley
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  • 8
    Publication Date: 2019
    Description: Abstract Central pit craters (CPCs) are complex craters that exhibit depressions within their floors or central uplifts. Some proposed models for central pit formation can be grouped by similar mechanism: (A) explosive volatile release, (B) central peak collapse, and (C) drainage of subsurface melted volatiles. We test these groups of mechanisms for central pit formation on Mars based on morphometries expected from each mechanism. Volatiles in the target (A and C) would be expected to result in a correlation with layered ejecta, also formed from volatiles, for CPCs over non‐CPCs. Central peak collapse (B) should result in larger diameters for pit rims than central peaks due to outward flow. Explosive volatile release (A) should yield smaller volumes for pit rims than pits due to mass loss. Data were collected on Context Camera images and digital elevation models for random samples of CPCs to assess the presence of these expected morphologies. Results of a Fisher exact test showed no preference in layered ejecta with CPCs over non‐CPCs, inconsistent with volatiles in the target. Results of an independent t test showed that central pit rim diameters are larger than central peak diameters, supporting some component of central peak collapse, although measurement uncertainty makes this interpretation tentative. Central pit rim volumes were not found to be statistically smaller than their pits, weighing against formation by explosive volatile release. Thus, our findings do not support any single group of formation mechanism tested here, although they allow for formation by some combination of these (or other) processes.
    Print ISSN: 2169-9097
    Electronic ISSN: 2169-9100
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
    Publication Date: 2015-10-31
    Description: Fault dips are a function of the coefficient of internal friction, μ i , of the lithospheric material. Laboratory deformation experiments of H 2 O ice at conditions applicable to icy bodies yield 0 ≤ μ i ≤ 0.55 such that normal faults dip between 45° and 59°. We tested the hypothesis that normal faults on icy bodies reflect these values by using digital elevation models to examine geometries of large extensional systems on three Saturnian satellites. Analyzed faults within Ithaca Chasma on Tethys and Avaiki Chasmata on Rhea all exhibit shallower-than-predicted topographic slopes across the fault scarp, which we term ‘fault slopes’. A scarp of Padua Chasmata within Dione's Wispy Terrain also has a shallow fault slope, although three others that make up Palatine Chasmata exhibit steeper slopes as predicted. We infer that viscous relaxation is the most viable explanation for these shallow fault slopes, and we model the potential role of viscous relaxation in creating shallow fault slopes. Our modeling results support formation of these normal faults with steep dips consistent with deformation experiments, followed by their relaxation due to lithospheric heating events related to radionuclide decay. The steepest fault slopes in this terrain yield 0 ≤ μ i ≤ 0.73 for Dione's lithospheric ice, which overlaps the dip range predicted from experiments. Results of this work suggest that viscous relaxation substantially affected fault slopes on Tethys, Rhea, and Dione. By implication, these processes may have also affected fault geometries on other icy satellites.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
    Publication Date: 2019
    Description: Abstract Estimating thermal conductivity of snow, firn, and porous ice is key for modeling the thermal regime of alpine and polar glaciers. Whereas thermal conductivity of snow was widely investigated, studies on firn and porous ice are very scarce. This study presents the effective thermal conductivity tensor computed from 64 3‐D images of microstructures of snow, antarctic firn, and porous ice at −3, −20, and −60°C. We show that, in contrast with snow, conductivity of firn and porous ice correlates linearly with density, is approximately isotropic, and is largely impacted by temperature. We report that performances of commonly used estimates of thermal conductivity vary largely with density. In particular, formulas designed for snow lead to significant underestimations when applied to denser ice structures. We present a new formulation to accurately estimate the thermal conductivity throughout the whole density range, from fresh snow to bubbly ice, and for any temperature conditions encountered in glaciers.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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