Toward cyberinfrastructure to facilitate collaboration and reproducibility for marine integrated ecosystem assessments

There is a growing need for cyberinfrastructure to support science-based decision making in management of natural resources. In particular, our motivation was to aid the development of cyberinfrastructure for Integrated Ecosystem Assessments (IEAs) for marine ecosystems. The IEA process involves analysis of natural and socio-economic information based on diverse and disparate sources of data, requiring collaboration among scientists of many disciplines and communication with other stakeholders. Here we describe our bottom-up approach to developing cyberinfrastructure through a collaborative process engaging a small group of domain and computer scientists and software engineers. We report on a use case evaluated for an Ecosystem Status Report, a multi-disciplinary report inclusive of Earth, life, and social sciences, for the Northeast U.S. Continental Shelf Large Marine Ecosystem. Ultimately, we focused on sharing workflows as a component of the cyberinfrastructure to facilitate collaboration and reproducibility. We developed and deployed a software environment to generate a portion of the Report, retaining traceability of derived datasets including indicators of climate forcing, physical pressures, and ecosystem states. Our solution for sharing workflows and delivering reproducible documents includes IPython (now Jupyter) Notebooks. We describe technical and social challenges that we encountered in the use case and the importance of training to aid the adoption of best practices and new technologies by domain scientists. We consider the larger challenges for developing end-to-end cyberinfrastructure that engages other participants and stakeholders in the IEA process.     

Scenarios of methane emission reductions to 2030: abatement costs and co-benefits to ozone air quality and human mortality

Methane emissions contribute to global baseline surface ozone concentrations; therefore reducing methane to address climate change has significant co-benefits for air quality and human health. We analyze the costs of reducing methane from 2005 to 2030, as might be motivated to reduce climate forcing, and the resulting benefits from lower surface ozone to 2060. We construct three plausible scenarios of methane emission reductions, relative to a base scenario, ranging from 75 to 180 Mton CH₄ yr^?1 decreased in 2030. Using compilations of the global availability of methane emission reductions, the least aggressive scenario (A) does not incur any positive marginal costs to 2030, while the most aggressive (C) requires discovery of new methane abatement technologies. The present value of implementation costs for Scenario B are nearly equal to Scenario A, as it implements cost-saving options more quickly, even though it adopts positive cost measures. We estimate the avoided premature human mortalities due to surface ozone decreases by combining transient full-chemistry simulations of these scenarios in a global atmospheric chemical transport model, with concentration-mortality relationships from a short-term epidemiologic study and projected global population. An estimated 38,000 premature mortalities are avoided globally in 2030 under Scenario B. As benefits of methane reduction are positive but costs are negative for Scenario A, it is justified regardless of how avoided mortalities are valued. The incremental benefits of Scenario B also far outweigh the incremental costs. Scenario C has incremental costs that roughly equal benefits, only when technological learning is assumed. Benefits within industrialized nations alone also exceed costs in Scenarios A and B, assuming that the lowest-cost emission reductions, including those in developing nations, are implemented. Monetized co-benefits of methane mitigation for human health are estimated to be $13–17 per ton CO₂eq, with a wider range possible under alternative assumptions. Methane mitigation can be a cost-effective means of long-term and international air quality management, with concurrent benefits for climate.     

Experimental transplanting of Posidonia australis seagrass in Port Hacking, Australia, to assess the feasibility of restoration

Over the last 50 years, about one-third of the original area of the seagrass Posidonia australis has been lost from Port Hacking (Australia) due to anthropogenic impacts. To assess the feasibility of restoring these seagrass meadows, healthy Posidonia rhizomes were transplanted to four impact sites and one control site. Survival rates of transplanted shoots were monitored in situ bi-monthly for 16 months and, at the end of the experiment, rhizome growth, shoot growth, shoot production and growth architecture were assessed by harvesting tagged rhizomes. A total of 575 shoots were transplanted and after 16 months 650 shoots were present. Four of the five sites exhibited high survival rates in the short term (less than six months) but only two impact sites, Burraneer Bay (BB) and Red Jacks Point (RJP), and the control site (CS) survived to the end of the experiment. Total number of shoots increased by 61% at CS, tripled at BB, but decreased by 22% at RJP. Rhizome growth varied significantly between site, from 22.3 +/- 1.4 cm yr(-1) at BB to 9.1 +/- 1.0 cm yr(-1) at RJP. Shoot growth did not vary significantly between sites and was approximately 2-3 cm yr(-1). At BB and CS there was substantial colonisation of the surrounding substrate, with new rhizomes, orthotropic shoots and transitional shoots produced. Survival of transplants appeared to depend on whether the factors that had caused the original loss of Posidonia were still operating in the study area.     

Considering the influence of sequestration duration and carbon saturation on estimates of soil carbon capacity

Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional plow tillage to no-till can increase soil C by an estimated 16±3%, whereas increasing rotation intensity can increase soil C by an estimated 6±3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C steady state is reached. However, soils could potentially sequester additional C following additional changes in management until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes in land management.     

Comets

Summary The status of cometary astronomy and astrophysics as of mid-1992 is reviewed, i.e. at a time when the first in situ observations of comets in 1985–86 have been thoroughly discussed, interpreted and compared with ground-based investigations. Many earlier ideas about comets were vindicated and a plethora of new discoveries resulted which have now led to reformulation of certain observational strategies and, in particular, to greatly improved possibilities for the detailed physical/chemical modelling of many cometary phenomena.A main purpose of this paper is to assess the current situation and to provide a reasonably complete, yet concise and critical evaluation of the most important questions and promising lines of research in this field. After a short introduction which defines the overall subject and the framework of the present review (Sect. 1), we take a look at some of the major past developments of our concepts about comets, in particular the crucial new insights which were gained during the past four decades (Sect. 2). The rapid advances in observational technology have greatly extended the realm of accessible problems and we next discuss the present possibilities and restrictions of the various techniques employed (Sect. 3).Part II of this paper discusses the modelling of cometary comae and tails (Sect. 4), the cometary nucleus (Sect. 5), the evolution (Sect. 6) and origin (Sect. 7) of comets and ends with an overview of the main questions now being asked by cometary studies (Sect. 8).     

Sea-ice characterization measurements needed for testing ofmicrowave remote sensing models

The nature and accuracy of ice-characterization measurements needed to test two microwave backscattering models are clarified by examining the sensitivities of these models to variations in the geophysical parameters they require as input. First, the Bragg, or small perturbation, model for rough surface scattering, which appears appropriate for backscattering from new ice types at L-band, is considered. The sensitivities of this model to variations in the dielectric constant of the ice and to the power spectrum of surface roughness are examined. The dense-medium radiation-transfer model at X-band is considered for backscattering from air bubbles embedded in multilayer ice. The sensitivities of this model to air-bubble size, air-volume fraction, and dielectric loss in the ice are examined. Based on these sensitivities, quantitative characterization guidelines for model testing are discussed     

Observations of the longitudinal magnetic field in the transition region and photosphere of a sunspot

The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft has observed for the first time the longitudinal component of the magnetic field by means of the Zeeman effect in the transition region above a sunspot. The data presented here were obtained on three days in one sunspot, have spatial resolutions of 10 arc sec and 3 arc sec, and yield maximum field strengths greater than 1000 G above the umbrae in the spot. The method of analysis, including a line-width calibration feature used during some of the observations, is described in some detail in an appendix; the line width is required for the determination of the longitudinal magnetic field from the observed circular polarization.The transition region data for one day are compared with photospheric magnetograms from the Marshall Space Flight Center. Vertical gradients of the magnetic field are computed from the two sets of data; the maximum gradients of 0.41 to 0.62 G km^–1 occur above the umbra and agree with or are smaller than values observed previously in the photosphere and low chromosphere.     

Geochemistry of tholeiites from Lanai,Hawaii

Lanai is the third smallest of the fifteen principal subaerial shield volcanoes of the Hawaiian hotspot. This volcano apparently became extinct during the shield-building stage of volcanism, as shown by the absence of both alkalic cap and post-erosional lavas. Major and trace element analyses of 22 new samples collected primarily from 3 stratigraphic sections show that Lanai tholeiites span a large range in composition. Some Lanai lavas are unique geochemically among Hawaiian tholeiites in having the lowest abundances of incompatible trace elements of any Hawaiian lavas and well-developed positive Eu anomalies. The geochemical characteristics of these low-abundance Lanai tholeiites are not the result of alteration, differences in mantle source modal mineralogy, the presence of residual accessory mantle phases or fractional crystallization of such phases, assimilation of depleted [MORB] wall-rock, or accumulation/resorption of phenocrysts or xenocrysts. Incompatible trace element ratios (e.g., Nb/La, Nb/Th, La/Th, La/Hf, Ce/Pb) in Lanai tholeiites span considerable ranges and form coherent trends with each other and with absolute abundances of these elements. Large variations in La/Sm, La/Yb, and absolute REE abundances at constant MgO suggest that Lanai tholeiites formed by variable amounts of partial melting. However, large ranges in incompatible element ratios cannot be explained solely by variations in partial melting of a geochemically homogeneous source, but must reflect geochemical heterogeneities in the Lanai source. Partial melting modeling indicates that the mixed Lanai source is probably LREE-enriched [i.e., (La/Yb)_CN>1]. One component in the Lanai source, exemplified by the low-abundance tholeiites, has markedly lower REE/HFSE, Th/HFSE, alkali/HFSE, and Ce/Pb ratios than other Lanai or Hawaiian tholeiites and may indicate the presence of recycled residual subduction zone materials in the Hawaiian plume source. The positive Eu anomalies that characterize the low-abundance Lanai tholeiites are not the result of plagioclase accumulation or assimilation but are a feature of this source component. Progressive temporal geochemical variations in Lanai tholeiites from 2 stratigraphic sections indicate that the source composition of these lavas probably evolved over time. This change could have resulted from a progressive decrease in the extent of partial melting of the Lanai source. The compositional variability of Lanai tholeiites suggests that geochemical heterogeneities in their source are larger than the scale of partial melting. Lanai tholeiites could not have formed by smaller degrees of partial melting of plume material than did the larger-volume Hawaiian shields. Therefore, volume differences between Hawaiian shields must be controlled primarily by differences in the volume of supplied plume material rather than by differences in the degree of partial melting. The premature cessation of eruptive activity at Lanai may be attributed to relatively large degrees of partial melting of a small plume.     

Archaean volcanism and sedimentation near Meekatharra,Western Australia

Archaean volcanic rocks and volcanogenic sediments exposed in a regional syncline south of Meekatharra, Western Australia are described. Initial volcanic activity produced a suite of high-Mg basalts containing 10–19% MgO. Pillowed tholeiitic basalts overlie the high-Mg basalts. These lower units are thought to have been derived from a central fracture zone. The uppermost units consist of volcanogenic sediments interlayered with andesite and dacite flows which appear to have been derived from a marginal andesite pile to the east. The Archaean sequence has been tightly folded, cross-faulted and intruded by post-Archaean dykes.The central succession is predominantly submarine, although the marginal andesite pile may be in part subaerial. Whilst there are some similarities with the Marda complex to the southeast (Hallberg et al., 1976), the rocks near Meekatharra are more analogous to those associated with modern island arcs.     

Analysis of recent crustal movement in the central and northern Sierra Nevada, California, using repeated geodetic leveling data

A comparative analysis of repeated geodetic leveling data was made along nine subparallel, E—NE-trending leveling lines located in the central to northern Sierra Nevada and the eastern Central Valley. The analysis was made to identify relative changes of elevation and evaluate these changes with respect to the regional geology and tectonics. The analysis used National Geodetic Survey first- and second-order, unadjusted, observed elevations.The relative changes in elevation indicate that crustal deformation is continuing to occur in the Sierra Nevada along pre-existing zones of crustal weakness and that this deformation is localized along some strands of Late Cenozoic faulting within the Mesozoic Foothills fault system. This deformation is characterized by variable and nonunifor westward tilt of the Sierran block west of the Melones fault zone, and relatively consistent eastward tilt of the Sierran block east of the Melones fault zone. Variable elevation changes occur within the Foothills fault system and are often associated with prominent geological or structural contacts. In addition, subsidence in the Central Valley appears to be of small magnitude and localized in extent, indicating nontectonic changes in elevation problably due to compaction of unconsolidated sediments.