Earth Science Community Research Articles

Open science in practice: Learning integrated modeling of coupled surface‐subsurface flow processes from scratch

AbstractIntegrated modeling of coupled surface‐subsurface flow and ensuing role in diverse Earth system processes is of current research interest to characterize nonlinear rainfall‐runoff response and also to understand land surface energy balances, biogeochemical processes, geomorphological dynamics, etc. A growing number of complex models have been developed for water‐related research, and many of these are made available to the Earth science community. However, relatively few resources have been made accessible to the potentially large group of Earth science and engineering users. New users have to invest an extraordinary effort to study the models. To provide a stimulating experience focusing on the learning curve of integrated modeling of coupled surface‐subsurface flow, we describe use cases of an open source model, the Penn State Integrated Hydrologic Model, PIHM. New users were guided through data processing and model application by reproducing a numerical benchmark problem and a real‐world watershed simulation. Specifically, we document the PIHM application and its computational workflow to enable intuitive understanding of coupled surface‐subsurface flow processes. In addition, we describe the user experience as important evidence of the significance of reusability. The interaction shows that documentation of data, software, and computational workflow in research papers is a promising method to foster open scientific collaboration and reuse. This study demonstrates how open science practice in research papers would promote the utility of open source software. Addressing such open science practice in publications would promote the utility of journal papers. Further, popularization of such practice will require coordination among research communities, funding agencies, and journals.

Benchmarking numerical models of brittle thrust wedges

We report quantitative results from three brittle thrust wedge experiments, comparing numerical results directly with each other and with corresponding analogue results. We first test whether the participating codes reproduce predictions from analytical critical taper theory. Eleven codes pass the stable wedge test, showing negligible internal deformation and maintaining the initial surface slope upon horizontal translation over a frictional interface. Eight codes participated in the unstable wedge test that examines the evolution of a wedge by thrust formation from a subcritical state to the critical taper geometry. The critical taper is recovered, but the models show two deformation modes characterised by either mainly forward dipping thrusts or a series of thrust pop-ups. We speculate that the two modes are caused by differences in effective basal boundary friction related to different algorithms for modelling boundary friction. The third experiment examines stacking of forward thrusts that are translated upward along a backward thrust. The results of the seven codes that run this experiment show variability in deformation style, number of thrusts, thrust dip angles and surface slope. Overall, our experiments show that numerical models run with different numerical techniques can successfully simulate laboratory brittle thrust wedge models at the cm-scale. In more detail, however, we find that it is challenging to reproduce sandbox-type setups numerically, because of frictional boundary conditions and velocity discontinuities. We recommend that future numerical-analogue comparisons use simple boundary conditions and that the numerical Earth Science community defines a plasticity test to resolve the variability in model shear zones.

SWAT hydrological model as a DaaS cloud service

Earth Science community depends on the exploration, analysis and reprocessing of high volumes of data as well as the modeling and simulation of complex coupled systems on multiple scales. The main aim of this article is to introduce a new hydrological modeling service based on the Soil and Water Assessment Tool (SWAT) (Arnold et al. J American Water Resour Assoc 34(1), 73–89, 1998 ; Arnold and Fohrer Hydrol Process 19(3), 563–572, 2005) model using high efficiency, resource sharing and low cost cloud computing resources (Astsatryan et al. International Journal of Scientific & Engineering Research 1(1), 1130–1133, 2014). Such a Desktop as a Service (DaaS) approach allowing users to work from anywhere, and gives centralized desktop management and great performance. Within the Spatial Data Infrastructure (SDI) and cloud platform, the DaaS service gives secure access to the model and a centralized data storage to get a SWAT model input. The article illustrates the analyses of the implementation of the SWAT model for the Sotk watershed of Lake Sevan in Armenia (Sargsyan 2007).

Cenozoic chronostratigraphic terminology: In defense of formal subseries

Ever since the series and corresponding epochs of the Cenozoic began to be defined over 180 years ago, the Earth science community has recognized bi- and tripartite lower/early, middle, and upper/late divisions of these units. As chronostratigraphy became more precise, these divisions assumed an essential role in the integration of the continuous deep-sea successions where the tools for worldwide correlation were developed, and the historic but disjunct sequences on land in which the stages/ages of the time scale were defined. Rather than being discarded as too vague, the essential value of these subdivisions has been tacitly recognized by describing them in terms of the newly recognized global stages, allowing their boundaries to be identified by the GSSPs (Global Stratotype Section and Point) of the lowest component stage. In this way, and without noticeable controversy, the modern Cenozoic literature treats the lower, middle and upper divisions of its series as elements within the chronostratigraphic hierarchy, i.e., as de facto subseries. Their status in the hierarchy has nonetheless been questioned recently by several members of the ICS (International Commission of Stratigraphy) Bureau on the basis that subseries, as such, have not been explicitly defined by ratified GSSPs. Accordingly, this rank has been omitted from versions of the ICC (International Chronostratigraphic Chart), a product of the ICS. Such omission fails to consider that subseries (and by inference subepochs) are valuable in circumstances where individual stages are inappropriate or often not applicable, e.g., in such disciplines as seismic stratigraphy and climatostratigraphy. The status of subseries in the Cenozoic Erathem is presently under discussion, and there exists within the Subcommissions on Paleogene and Neogene Stratigraphy of the ICS the view that such divisions should have informal status (i.e., non IUGS-ratified subseries/subepochs). This would seemingly contradict the primary goal of the ICS, which since 1986 has focused on establishing a functional common language for all whoworkwith geological time, by making the widely used concepts of subseries and subepochs open to misunderstanding. It also begs the question, as to why should something that consists of GSSP-defined units, and which is in turn a component of higher units in the chronostratigraphic hierarchy, not be considered a formal chronostratigraphic unit in its own right? The reality is that whether formal or informal, the subseries/subepochs of the Cenozoic will continue to be broadly used. Therefore, the interest of the ICS and the Earth science community is best served by formally recognizing them in the ICC hierarchy. This will clarify the problem of inconsistent capitalization of the terms lower, early, middle, upper and late where these are in fact part of a formal unit name and not just a modifier for an indefinite interval, and it will satisfy the broad consensus of the profession, as evidenced during a recent open meeting of the ICS during the 2nd International Congress on Stratigraphy in Graz in 2015.

Strategies towards statistically robust interpretations of in situ U–Pb zircon geochronology

Zircon U–Pb geochronology has become a keystone tool across Earth science, arguably providing the gold standard in resolving deep geological time. The development of rapid in situ analysis of zircon (via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable (e.g. detrital zircons as a sediment fingerprinting method). The ease of acquisition, while bringing benefit to the Earth science community, has also led to diverse interpretations of geochronological data. In this work we seek to refocus U–Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow. We discuss a range of data filtering approaches and their inherent limitations (e.g. discordance and the reduced chi-squared; MSWD). We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both 238U/206Pb and 207Pb/206Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios. As our in situ analytical techniques become progressively more precise, appropriate statistical handing of U–Pb datasets will become increasingly pertinent.

Community Recommendations for Sustainable Scientific Software

Science software has contributed to research practices, but the sustainability of scientific software presents challenges for the future use of research resources. Identifying improvements for science software sustainability practices can contribute to the re-use of science software. A focus group study was conducted to identify ways to improve science software sustainability practices of the Earth science community. A facilitated, roundtable discussion activity at the 2014 Federation of Earth Science Information Partners (ESIP) Summer Meeting elicited recommendations on community activities to improve practices for the sustainability of scientific software. These suggestions fell into three broad themes – (1) improving collaboration and community engagement through publications and presentations (2) developing workshops, training, and documenting best practices and (3) creating incentives and motivation with awards, citation and a reviewed software repository. In addition to the recommendations coming out of the roundtable activity, this paper highlights how community-led groups such as ESIP are key to move a sustainable software effort in its various forms from concept to reality.

Open-pit mining geomorphic feature characterisation

Among the anthropogenic topographic signatures on Earth, open-pit mines are of great importance. Mining is of interest to geomorphologists and environmental researchers because of its implication in geomorphic hazards and processes. In addition, open-pit mines and quarries are considered the most dangerous industrial sector, with injuries and accidents occurring in numerous countries. Their fast, accurate and low-cost investigation, therefore, represents a challenge for the Earth science community. The purpose of this work is to characterise the open-pit mining features using high-resolution topography and a recently published landscape metric, the Slope Local Length of Auto-Correlation (SLLAC) (Sofia et al., 2014). As novel steps, aside from the correlation length, the terrace’s orientation is also calculated, and a simple empirical model to derive the percentage of artificial surfaces is tested. The research focuses on two main case studies of iron mines, both located in the Beijing district (P.R. China). The main topographic information (Digital Surface Models, DSMs) was derived using an Unmanned Aerial Vehicle (UAV) and the Structure from Motion (SfM) photogrammetric technique. The results underline the effectiveness of the adopted methodologies and survey techniques in the characterisation of the main mine’s geomorphic features. Thanks to the SLLAC, the terraced area given by open-cast/open-pit mining for iron extraction is automatically depicted, thus, allowing researchers to quickly estimate the surface covered by the open-pit. This information could be used as a starting point for future research (i) given the availability of multi-temporal surveys to track the changes in the extent of the mine; (ii) to relate the extent of the mines to the amount of processes in the area (e.g. pollution, erosion, etc.), and to (iii) combine the two points, and analyse the effects of the change related to changes in erosion. The analysis of the correlation length orientation also allows researchers to identify the terrace’s orientation and to understand the shape of the open-pit area. The tectonic environment and history, or inheritance, of a given slope can determine if and how it fails, and the orientation of the topographic surface or excavation face, with respect to geologic features, is of major significance. Therefore, the proposed approach can provide a basis for a large-scale and low-cost topographic survey for sustainable environmental planning and, for example, for the mitigation of environmental anthropogenic impacts due to mining.

Tracking Land Use/Land Cover Dynamics in Cloud Prone Areas Using Moderate Resolution Satellite Data: A Case Study in Central Africa

Tracking land surface dynamics over cloud prone areas with complex mountainous terrain is an important challenge facing the Earth Science community. One such region is the Lake Kivu region in Central Africa. We developed a processing chain to systematically monitor the spatio-temporal land use/land cover dynamics of this region over the years 1988, 2001, and 2011 using Landsat data, complemented by ancillary data. Topographic compensation was performed on Landsat reflectances to avoid the strong illumination angle impacts and image compositing was used to compensate for frequent cloud cover and thus incomplete annual data availability in the archive. A systematic supervised classification was applied to the composite Landsat imagery to obtain land cover thematic maps with overall accuracies of 90% and higher. Subsequent change analysis between these years found extensive conversions of the natural environment as a result of human related activities. The gross forest cover loss for 1988–2001 and 2001–2011 period was 216.4 and 130.5 thousand hectares, respectively, signifying significant deforestation in the period of civil war and a relatively stable and lower deforestation rate later, possibly due to conservation and reforestation efforts in the region. The other dominant land cover changes in the region were aggressive subsistence farming and urban expansion displacing natural vegetation and arable lands. Despite limited data availability, this study fills the gap of much needed detailed and updated land cover change information for this biologically important region of Central Africa. These multi-temporal datasets will be a valuable baseline for land use managers in the region interested in developing ecologically sustainable land management strategies and measuring the impacts of biodiversity conservation efforts.

Web-Based Data Integration and Interoperability for a Massive Spatial-Temporal Dataset of the Heihe River Basin EScience Framework

To solve the messy problem of data types and form a unified data-processing solution, data in the Heihe River Basin were first classified into five types to integrate them and achieve unified management of data and metadata, preventing the loss of metadata, in the data model of eScience framework. Considering many of the challenges that exist in the construction of the online spatial-temporal data integration and interoperability eScience platform, we used the open data interfaces and standards such as the Common DataModel (CDM) interface, common scientific data modelling (i.e., NetCDF, GRIB, and HDF), and Open Geospatial Consortium (OGC) standards. Through the eScience platform, we also provided online data processing tools by collecting free tools (e.g., NetCDF tool, quality control tool). This eScience platform enables researchers to make full use of scientific research information and results and facilitates collaboration, especially between the GIS community and other members of the earth science community, with the purpose of establishing an online platform of uniform spatial data from the Heihe River Basin via common scientific data modelling.

The Effectiveness of Science on a Sphere Stories to Improve Climate Literacy Among the General Public

ABSTRACT Engaging the general public on climate topics and deepening their understanding of key discoveries by the Earth science community requires a collaborative approach between scientists, developers, and museum educators to converge on the most effective format. Large Science On a Sphere (SOS) displays of Earth attract attention to global data at museums worldwide, yet just looking at raw data does not generally lead to new insights by the public. Working closely with the Maryland Science Center, the EarthNow project realized the time limitations of the museum staff and audience and began creating short, narrated videos for SOS. The videos introduce recent climate science findings on a variety of topics and can be used as part of live, facilitated programs or played while SOS is in its autorun mode. To measure the effectiveness of the delivery method, we developed a survey and tested several groups that saw a video within a live show compared to groups that saw it in autorun without a live program. We also wondered whether adding a hands-on activity would enhance learning and how hearing the information while doing an activity would compare to watching and hearing the SOS show, so we tested two large groups using the activity with and without seeing Science On a Sphere. Overall survey results demonstrate the groups who saw an SOS show gained certain concepts better than the group that only heard the information while doing the activity. The live shows conferred a slight but not substantial advantage over the autorun shows. Playing short, narrated videos on SOS that include global Earth processes, such as atmospheric and oceanic circulation, seems to enhance understanding of certain concepts more than hearing the information while doing an activity. Ongoing communication with museums and their visitors is critical for ensuring that these stories are as effective as possible and make best use of the strengths of the Science On a Sphere exhibit to enhance the public's climate literacy.

NSF Geosciences Draft Report Available for Comment

The U.S. National Science Foundation's Advisory Committee for the Geosciences (NSF's AC GEO) is seeking comments from the Earth science community on a draft document issued on 7 August that outlines “imperatives and frontier areas” for NSF's Directorate for Geosciences (GEO). The report, Dynamic Earth: GEO Priorities & Frontiers 2015–2020, is an update to the directorate's 2009 report, GEO Vision.

High-pressure structural behaviour of CaIrO3polymorphs

The two known polymorphs of CaIrO3 crystallize int the orthorhombic space groups Pbnm and Cmcm. These compounds have been the focus of much research in the Earth sciences community because they are isostructural with MgSiO3 perovskite and post-perovskite structures which are likely the most abundant minerals in the Earth's lower mantle. CaIrO3 post-perovskite is stable at ambient conditions and transforms at 1-3 GPa and at temperatures above 13500C to the CaIrO3 perovskite structure providing an ideal low pressure and low temperature analogue for the MgSiO3 perovskite to post-perovskite phase transformation which occurs at the extreme conditions of 125 GPa and 2500 K. However, in order to assess whether the CaIrO3 compounds can be used as analogues of MgSiO3 phases, a correct knowledge of their atomic structures and their response to changes in pressure and temperature is essential. In this study the structural behavior of both CaIrO3 polymorphs has been investigated using single-crystal X-ray diffraction at different pressures up to 10 GPa. The orthorhombic distortion of CaIrO3 perovskite derives from the cubic perovskite aristotype by tilting of the octahedral units. These tilts are very large and their variation with pressure is clearly different from the tilting reported for other Ca-oxide perovskites giving rise to a much stiffer structure. The CaIrO3 post-perovskite phase has a layered structure consisting of alternating sheets of Ca atoms and distorted IrO6 octahedra which share edges to form rows running parallel to [100]. With increasing pressure the octahedral tilting remains practically constant and compression of the post-perovskite structure occurs as a result of compression of Ca layers. With increasing temperature, instead, the octahedral tilting increases giving rise to smaller distances between oxygens of adjacent octahedra whose repulsion likely causes the transformation to the CaIrO3 perovskite structure.

Promoting geodiversity: learning lessons from biodiversity

Progress made in promoting geodiversity in recent times is reviewed, concluding that it is now an established component of the Earth Sciences. However, it still lacks the status and standing of biodiversity in governmental, political and public forums. The paper assesses what can be learnt from the experience of the development and promotion of biodiversity. Based on this experience, eight suggestions for increasing the understanding and ownership of geodiversity beyond the Earth science community are provided as a basis for discussion.

Using Semantic Search and Knowledge Reasoning to Improve the Discovery of Earth Science Records

Web resources exploration is increasingly driven by semantic web technologies with automated processing. Earth science communities generate large amounts of datasets described in hundreds of millions of metadata records. It is critical to discover the accurate data from the millions of data records based on the end user's searching intent. However, the big challenge is how to ensure that catalogs and Spatial Web Portals can understand end user's intents. To enable portals effectively ‘understand' the meaning of user's queries and to provide a better searching experience for end users, we collaborated with Earth Science Information Partners (ESIP) to develop such a capability through a semantic Testbed. We implemented a reasoning engine using similarity calculations to facilitate the meaningful discovery of Earth science data and to improve the accuracy of searching results.

Megaclasts: Proposed Revised Nomenclature At the Coarse End of the Udden-Wentworth Grain-Size Scale for Sedimentary Particles

Abstract The expanded Udden-Wentworth (U-W) grain-size scale is an important tool for classifying the size of sedimentary particles. However, some of the existing terminology at the coarse end of the scale is problematic. In particular, the current terms “block” and “slab” are used to define size ranges, despite having recognized shape connotations and simultaneous application in particle form (shape) diagrams. The dual usage such of terminology is undesirable and may have contributed to the lack of strict adherence by the earth science community to the upper end of the U-W scale, resulting in part in the plethora of alternative expressions that have appeared in recent years for describing very large clasts. Our solution to this conundrum is to abandon shape-related terms and replace them with an incremental system based on the prefixes meso- and macro- to classify very large boulder size ranges. In this way, both size and shape classification of very coarse sediments can be accomplished satisfactorily without unnecessary overlap or confusion in nomenclature. The term “megaclast” is appropriate to remain as a universal descriptor for all clasts greater than boulder size (i.e., b axis > 4.1 m), as previously defined.

Plate tectonics in the late Paleozoic

As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere) becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying) plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma) together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

Cyber‐Infrastructure and Synergistic Opportunities Across the Geosciences

To enable transformational research and education within and across geoscience disciplines, as part of the U.S. National Science Foundation's (NSF) EarthCube initiative, over the past 2 years NSF has sponsored 26 end user workshops in diverse geoscience domains. EarthCube is a collaboration among NSF, other government agencies, and the geoscience and cyber‐infrastructure communities. The workshops engaged more than 1200 participants from the academic, government, and private sectors of the Earth, atmospheric, ocean, computer, information, and social science communities with the overarching objectives of better understanding the limitations of existing cyber‐infrastructure and identifying synergistic opportunities that will help make Web‐based technologies for sharing data, tools, and models accessible to the majority of geoscientists.

Geoscience Data Provenance: An Overview

The advancement of Earth observing sensors, data, and information systems enhances significantly the capabilities to access and process large volumes of geoscience data, which are often consumed by scientific workflows and processed in a distributed information environment. Consequently, data provenance becomes important since it allows users to determine the usability and reliability of data products. Motivation for capturing and sharing provenance also comes from the distributed data and information infrastructure that has been benefiting the Earth science community in the past decade, such as spatial data and information infrastructure, e-Science, and cyberinfrastructure. This paper provides an overview of geoscience data provenance in supporting provenance-aware geoscience data and information systems by summarizing state-of-the-art technologies and methodologies of geoscience data provenance and highlighting key considerations and possible solutions for geoscience data provenance.

Optimal Satellite Formation Reconfiguration Based on Closed-Loop Brain Storm Optimization

In recent years, satellite formation flying has become an increasingly hot topic for both the astronomy and earth science communities due to its potential merits compared with a single monolithic spacecraft system. This paper proposes a novel approach based on closed-loop brain storm optimization (CLBSO) algorithms to address the optimal formation reconfiguration of multiple satellites using two-impulse control. The optimal satellite formation reconfiguration is formulated as an optimization problem with the constraints of overall fuel cost minimization, final configuration, and collision avoidance. Three versions of CLBSOs are developed by replacing the creating operator in basic brain storm optimization (BSO) with closed-loop strategies, which facilitate search characteristic capture and enhance the optimization performance by taking advantage of feedback information in the search process. Numerical simulations are carried out using particle swarm optimization (PSO), basic BSO, and the three versions of CLBSOs. Comparison results show that all versions of CLBSOs outperform PSO and the original BSO in terms of final results and convergence speed. In addition, CLBSO reduces the computation burden and shortens CPU time to a certain extent in contrast with basic BSO. Furthermore, among the three CLBSO algorithms, the one using the strategy of difference with the best gains the best overall performance, which is inspired by the updating rule in PSO that each particle tends to move towards the individual with the best fitness.

Earth and Space Science Community Assesses Impacts of U.S. Government Shutdown

The recent 16‐day shutdown of the U.S. federal government cost the U.S. economy an estimated $24 billion. Federal science agencies are also tallying significant negative effects, including interruptions, delays, and, in some cases, cancellation of critical research projects in the Earth and space sciences.