bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Global Assessment of Terrestrial Evapotranspiration Increase Due to Surface Water Area Change
Authors: Zhan Shengan , Song Chunqiao , Wang Jida , Sheng Yongwei , Quan Jiping 
Published: February 2019

AbstractSurface water, which is changing constantly, is a crucial component in the global water cycle, as it greatly affects the water flux between the land and the atmosphere through evaporation. However, the influences of changing surface water area on the global water budget have largely been neglected. Here we estimate an extra water flux of 30.38 ± 15.51 km3/year omitted in global evaporation calculation caused by a net increase of global surface water area between periods 1984–1999 and 2000–2015. Our estimate is at a similar magnitude to the recent average annual change in global evapotranspiration assuming a stationary surface water area. It is also comparable to the estimated trends in various components of the hydrological cycle such as precipitation, discharge, groundwater depletion, and glacier melting. Our findings suggest that the omission of surface water area changes may cause considerable biases in global evaporation estimation, so an improved understanding of water area dynamics and its atmospheric coupling is crucial to reduce the uncertainty in the estimation of future global water budgets.
A Coherent Statistical Model for Coastal Flood Frequency Analysis Under Nonstationary Sea Level Conditions
Authors: Ghanbari Mahshid , Arabi Mazdak , Obeysekera Jayantha , Sweet William 
Published: February 2019

AbstractFlood exposure is increasing in coastal communities due to rising sea levels. Understanding the effects of sea level rise (SLR) on frequency and consequences of coastal flooding and subsequent social and economic impacts is of utmost importance for policymakers to implement effective adaptation strategies. Effective strategies may consider impacts from cumulative losses from minor flooding as well as acute losses from major events. In the present study, a statistically coherent Mixture Normal‐Generalized Pareto Distribution model was developed, which reconciles the probabilistic characteristics of the upper tail as well as the bulk of the sea level data. The nonstationary sea level condition was incorporated in the mixture model using Quantile Regression method to characterize variable Generalized Pareto Distribution thresholds as a function of SLR. The performance validity of the mixture model was corroborated for 68 tidal stations along the Contiguous United States (CONUS) coast with long‐term observed data. The method was subsequently employed to assess existing and future coastal minor and major flood frequencies. The results indicate that the frequency of minor and major flooding will increase along all CONUS coastal regions in response to SLR. By the end of the century, under the “Intermediate” SLR scenario, major flooding is anticipated to occur with return period less than a year throughout the coastal CONUS. However, these changes vary geographically and temporally. The mixture model was reconciled with the property exposure curve to characterize how SLR might influence Average Annual Exposure to coastal flooding in 20 major CONUS coastal cities.
A Geodetic Strain Rate and Tectonic Velocity Model for China
Authors: Rui X. , Stamps D. S. 
Published: February 2019

AbstractThe conjoining and interfering influence of the Circum‐Pacific zone and the Tethys‐Himalayan zone make China a country of intense intracontinental seismicity. Here we provide three new quantitatively assessed products and use them to better constrain seismic hazards in China. First, we process ~2,700 Global Positioning System (GPS) data spanning 1996–2017 provided by the Crustal Movement Observation Network of China (CMONOC) network and the Nevada Geodetic Laboratory. To produce a robust tectonic velocity solution, we implement a data editing scheme to account for 8 Mw ≥ 7 earthquakes to reduce the influence of transient phenomena. The solution is then rotated into a consistent reference frame with 10 other published velocity sources surrounding mainland China. Second, we calculate a new geodetic strain rate model using an optimal mesh grid definition of 0.4° × 0.4° determined jointly by the Nyquist frequency method and checkerboard tests. We evaluate and validate the geodetic strain rate results from both a statistical (i.e., based on the Bayesian factor) and quantitative (i.e., based on the comparison with the 2‐D analytical strain rate result) approaches. Third, we use our new geodetic strain rate model to estimate seismicity rates.
Bubble Coalescence and Percolation Threshold in Expanding Rhyolitic Magma
Authors: Giachetti Thomas , Gonnermann Helge M. , Gardner James E. , Burgisser Alain , Hajimirza Sahand , Earley Tobias C. , Truong Nathan , Toledo Pamela 
Published: February 2019

AbstractCoalescence during bubble nucleation and growth in crystal‐free rhyolitic melt was experimentally investigated, and the percolation threshold, defined as the porosity at which the vesicular melt first becomes permeable, was estimated. Experiments with bubble number densities between 1014 and 1015 m−3 were compared to four suites of rhyolitic Plinian pumices, which have approximately equal bubble number densities. At the same total porosity, Plinian samples have a higher percentage of coalesced bubbles compared to their experimental counterparts. Percolation modeling of the experimental samples indicates that all of them are impermeable and have percolation thresholds of approximately 80–90%, irrespective of their porosity. Percolation modeling of the Plinian pumices, all of which have been shown to be permeable, gives a percolation threshold of approximately 60%. The experimental samples fall on a distinct trend in terms of connected versus total porosity relative to the Plinian samples, which also have a greater melt‐bubble structural complexity. The same holds true for experimental samples of lower bubble number densities. We interpret the comparatively higher coalescence within the Plinian samples to be a consequence of shear deformation of the erupting magma, together with an inherently greater structural complexity resulting from a more complex nucleation process.
How the Transition Region Along the Cascadia Megathrust Influences Coseismic Behavior: Insights From 2‐D Dynamic Rupture Simulations
Authors: Ramos Marlon D. , Huang Yihe 
Published: February 2019

AbstractThere is a strong need to model potential rupture behaviors for the next Cascadia megathrust earthquake. However, there exists significant uncertainty regarding the extent of downdip rupture and rupture speed. To address this problem, we study how the transition region (i.e., the gap), which separates the locked from slow‐slip regions, influences coseismic rupture propagation using 2‐D dynamic rupture simulations governed by a slip‐weakening friction law. We show that rupture propagation through the gap is strongly controlled by the amount of accumulated tectonic initial shear stress and gap friction level. A large amplitude negative dynamic stress drop is needed to arrest downdip rupture. We also observe downdip supershear rupture when the gradient in effective normal stress from the locked to slow‐slip regions is dramatic. Our results justify kinematic rupture models that extend below the gap and suggests the possibility of high‐frequency energy radiation during the next Cascadia megathrust earthquake.
Singular Spectrum Analysis With Conditional Predictions for Real‐Time State Estimation and Forecasting
Authors: Ogrosky H. Reed , Stechmann Samuel N. , Chen Nan , Majda Andrew J. 
Published: February 2019

AbstractSingular spectrum analysis (SSA) or extended empirical orthogonal function methods are powerful, commonly used data‐driven techniques to identify modes of variability in time series and space‐time data sets. Due to the time‐lagged embedding, these methods can provide inaccurate reconstructions of leading modes near the endpoints, which can hinder the use of these methods in real time. A modified version of the traditional SSA algorithm, referred to as SSA with conditional predictions (SSA‐CP), is presented to address these issues. It is tested on low‐dimensional, approximately Gaussian data, high‐dimensional non‐Gaussian data, and partially observed data from a multiscale model. In each case, SSA‐CP provides a more accurate real‐time estimate of the leading modes of variability than the traditional reconstruction. SSA‐CP also provides predictions of the leading modes and is easy to implement. SSA‐CP is optimal in the case of Gaussian data, and the uncertainty in real‐time estimates of leading modes is easily quantified.
Satellite‐Observed Changes in Mexico's Offshore Gas Flaring Activity Linked to Oil/Gas Regulations
Authors: Zhang Yuzhong , Gautam Ritesh , Zavala‐Araiza Daniel , Jacob Daniel J. , Zhang Ruixiong , Zhu Lei , Sheng Jian‐Xiong , Scarpelli Tia 
Published: February 2019

AbstractGas flaring is a commonly used practice in the oil and gas sector that leads to key air pollutant and greenhouse gas emissions. Here we use multipollutant (NO2, SO2) satellite observations from 2005 to 2017 to quantify gas flaring activity in Mexico's offshore production cluster, which produces ~50–70% of the country's oil and is among the world's largest oil fields. We estimate annual flared gas volume ranging from 5.5 to 20 × 109 m3 over the Mexican offshore corresponding to >40% associated gas production, which is significantly larger than for instance offshore United States where reportedly <3% of associated gas is flared. The 13‐year record of satellite‐derived gas flaring indicates a drastic increase until 2008 and a decline afterward. While the increased flaring is associated with efforts to enhance oil production, the post‐2008 decline is linked to an expanding capacity of associated gas utilization, providing a continuing opportunity to reduce flaring for environmental and economic benefits.
Nonlinearity in the North Pacific Atmospheric Response to a Linear ENSO Forcing
Authors: Jiménez‐Esteve B. , Domeisen D. I. V. 
Published: February 2019

AbstractEl Niño Southern Oscillation (ENSO) exerts a remote impact on the North Pacific and North American winter climate. Both observational and model studies have suggested nonlinearities in this teleconnection. However, it remains unclear if possible nonlinearities arise from the forcing strength or the forcing location in the tropical Pacific, or from factors external to the tropical Pacific. To separate these factors, an idealized model is forced with seasonally varying sea surface temperature with linearly varying strength at a fixed location. Whereas for moderate events the North Pacific response is more linear, strong events exhibit significant nonlinearity both in terms of the strength and location of the impact. The nonlinearity can be traced back to the relationship between sea surface temperature and tropical convection. Nonlinearity in the North Pacific response can have important impacts for long‐range prediction and for potential changes in the diversity of ENSO with climate change.
A Cool, Nutrient‐Enriched Eastern Equatorial Pacific During the Mid‐Pleistocene Transition
Authors: Robinson Rebecca S. , Jones Colin A. , Kelly Roger P. , Rafter Patrick , Etourneau Johan , Martinez Philippe 
Published: February 2019

AbstractThe emergence of high‐amplitude, low‐frequency glacial‐interglacial cycles during the mid‐Pleistocene climate transition (MPT; 800–1,200 ka) is associated with global cooling. In the eastern equatorial Pacific, sea surface temperatures cooled, and the upwelling‐induced cold tongue expanded significantly during the MPT. Here we use sedimentary records of iron, biogenic silica, and nutrient‐nitrogen consumption to evaluate biogeochemical changes hypothesized to accompany the cold tongue expansion. Our results suggest that the eastern equatorial Pacific of the MPT hosted surface waters with higher nitrate contents and biogenic silica production relative to the last 600 ka. Increased production occurred despite low iron supply. We attribute this to enhanced upwelling and nutrient enrichment of thermocline waters, both likely related to the northward migration of Southern Ocean fronts. The return of these fronts to their southward positions after the MPT may be associated with stronger drawdown of nutrients and, potentially, atmospheric CO2 in the Southern Ocean.
Arctic‐Boreal Lake Dynamics Revealed Using CubeSat Imagery
Authors: Cooley Sarah W. , Smith Laurence C. , Ryan Jonathan C. , Pitcher Lincoln H. , Pavelsky Tamlin M. 
Published: February 2019

AbstractFine‐scale, subseasonal fluctuations in Arctic‐Boreal surface water reflect regional water balance and modulate trace gas emissions to the atmosphere but have eluded detection using traditional satellite remote sensing. We use high‐resolution (~3–5 m), high‐frequency CubeSat sensors to measure near‐daily changes in lake surface area through an object‐based tracking method that incorporates machine learning to overcome notable limitations of CubeSat imagery. From ~76,000 images we obtain >2.2 million individual observations of changing surface areas for 85,358 lakes in Northern Canada and Alaska between 1 May and 1 October 2017. We find broad‐scale lake area declines across diverse climatic, hydrologic, and physiographic terrains. Localized exceptions reveal lowland flooding and aquatic vegetation phenology cycles. Cumulative small shoreline changes of abundant lakes on the Canadian Shield exceed total inundation variations of better‐studied lowland environments, revealing a surprisingly dynamic landscape with respect to subseasonal variations in surface water extent and trace gas emissions.
Seismic Constraints on the Magmatic System Beneath the Changbaishan Volcano: Insight Into its Origin and Regional Tectonics
Authors: Fan Xingli , Chen Qi‐Fu 
Published: February 2019

AbstractThere is a growing concern about the potential eruption of the Changbaishan volcano (CBV) in recent years, but the magmatic system beneath this volcano remains hotly debated. In this study, we construct a high‐resolution 3‐D crust and upper mantle S wave velocity (Vs) model beneath the CBV and adjacent regions combining ambient noise and earthquake surface wave tomography. Distinct low Vs anomalies are revealed in the crust and upper mantle beneath the CBV. The middle‐lower crustal low‐velocity body is interpreted to be the main magma chamber that may feed the surface volcanism and hydrothermal activities. The upper mantle low‐velocity zone is representative of upwelling asthenosphere. The lower crust beneath the Longgang volcano and Jingpohu volcano is also characterized by low Vs anomalies, maybe indicating low‐degree partial melting. We propose that the intraplate volcanism of the CBV as well as the Longgang volcano and Jingpohu volcano is driven by the decompression melting of upwelling asthenosphere, which could originate from the mantle transition zone as suggested by previous large‐scale tomographic studies. Moreover, the geologically identified Solonker‐Xar Moron‐Changchun‐Yanji suture zone is delineated by a prominent high Vs anomaly in the uppermost mantle, which may be explained by the fossil slab remnants or deformational fabrics resulted from the final closure of the Paleo‐Asian Ocean in the Late Paleozoic to Early Mesozoic.
Gravity Changes Due to Large Earthquakes Detected in GRACE Satellite Data via Empirical Orthogonal Function Analysis
Authors: Chao B. F. , Liau J. R. 
Published: February 2019

AbstractWe report on the seven largest earthquakes for which we can detect unequivocal coseismic signals in the time‐variable gravity (TVG) data of the GRACE (Gravity Recovery and Climate Experiment) satellite mission during the GRACE era of 2002–2017. After reducing the land‐hydrological effect according to model Global Land Data Assimilation System, we employ the empirical orthogonal function (EOF) analysis to solve for the spatial pattern and time history of the coherent (standing‐oscillation) modes, which provide in an objective manner an overall view of the spatiotemporal scenario. The solved EOF mode for an earthquake‐induced TVG typically features a spatial pattern (along with polarity) for the coseismic jump, in conjunction with the time series showing the jump (plus possible preseismic and postseismic variability). In all cases the earthquake EOF mode solutions match well with the least squares coseismic jump in both spatial pattern and amplitude and agree generally with previous reports in the literature. We conclude according to the examined cases that the lowest earthquake magnitude threshold that can be detected by GRACE is the Mw 8.3 of the 2013 deep‐focus Okhotsk event, which in fact provides a testable case where the TVG we observe versus the seismologically derived source models may reflect different aspects of the source mechanism under different timescales.
Processing Choices Affect Ocean Mass Estimates From GRACE
Authors: Uebbing B. , Kusche J. , Rietbroek R. , Landerer F. W. 
Published: February 2019

AbstractAccurate estimates of ocean mass change are necessary to infer steric sea level change from sea level changes measured with satellite altimeters. Published studies using the Gravity Recovery and Climate Experiment (GRACE) satellite mission indicated a large range in trends (∼1–2 mm/year) with reported standard errors of 0.1–0.3 mm/year. Here we show that a large part of this discrepancy (up to 0.6 mm/year) can be explained by which model is used to account for the effect of glacial isostatic adjustment (GIA). The second largest contribution (0.3–0.4 mm/year) is related to the way how different studies have restored atmospheric and oceanic signals which have been removed during the GRACE gravity estimation process. Here two processing strategies, which previously resulted in differing ocean mass trends, are considered. The “direct” method uses the standard GRACE Stokes coefficients, while the “inverse” method applies a joint inversion of data from GRACE and altimetry. After accounting for differences in processing corrections, global mean ocean mass estimates from the direct, the mascon, and inverse approach agree with each other on global scales within less than 0.1 mm/year. Using the A et al. (2013; https://doi.org/10.1093/gji/ggs030) GIA model, we provide a reconciled monthly time series of global mean ocean mass, which suggests that ocean mass has increased by 1.43 mm/year over 2002.6–2014.5, with an amplified rate of 1.75 mm/year over 2002.6–2016.5 which covers almost the complete GRACE time span. However, we note that estimates as low as 1.05 mm/year cannot be ruled out when other published GIA corrections with lower mass‐equivalent signals over Antarctica are used.
A Game Theory Warning to Blind Drivers Playing Chicken With Public Goods
Authors: Ristić Bora , Madani Kaveh 
Published: February 2019

AbstractWe develop a game theoretic model of the role of foresight in games involving users interacting over a public good. Previous research in this area has applied game theory to understand social dilemmas and inform policy initiatives. However, considerations of the “evolving structure” of natural resource games over time and agents' planning horizon raises the complexity of game analysis substantially and has often been overlooked. We analyze a simple model of an irrigation system shared by two users and consider how players will act under different levels of foresight. Without foresight into game changes over time, players are blind to the fact that they are in a game of chicken. We model agents with foresight by interconnecting games across time and show how this creates opportunities for “strategic loss” early on, allowing players with foresight to reduce total costs. High future costs can thus be avoided with foresight if the rising costs of inaction are made apparent. We consider the effect of discounting and differences between players to provide policy recommendations regarding incentives for foresight.
Bioclimatic and Soil Moisture Monitoring Across Elevation in a Mountain Watershed: Opportunities for Research and Resource Management
Authors: Osenga E. C. , Arnott James C. , Endsley K. Arthur , Katzenberger J. W. 
Published: February 2019

AbstractSoil moisture data are critical to understanding biophysical and societal impacts of climate change. However, soil moisture data availability is limited due to sparse in situ monitoring, particularly in mountain regions. Here we present methods, specifications, and initial results from the interactive Roaring Fork Observation Network (iRON), a soil, weather, and ecological monitoring system in the Southern Rocky Mountains of Colorado. Initiated in 2012, the network is currently composed of nine stations, distributed in elevation from 1,890 to 3,680 m, that continually collect and transmit measurements of soil moisture at three depths (5, 20, and 50 cm), soil temperature (20 cm), and meteorological conditions. Time‐lapse cameras for phenological observations, snow depth sensors, and periodic co‐located vegetation surveys complement selected stations. iRON was conceived and designed with the joint purpose of supporting bioclimatic research and resource management objectives in a snow‐dominated watershed. In the short term, iRON data can be applied to assessing the impact of temperature and precipitation on seasonal soil moisture conditions and trends. As more data are collected over time, iRON will help improve understanding of climate‐driven changes to soil, vegetation, and hydrologic conditions. In presenting this network and its initial data, we hope that the network's elevational gradient will contribute to bioclimatic mountain research, while active collaboration with partners in resource management may provide a model for science‐practice interaction in support of long‐term monitoring.
TGFβ/BMP immune signaling affects abundance and function of C. elegans gut commensals
Authors: Berg Maureen , Monnin David , Cho Juhyun , Nelson Lydia , Crits-Christoph Alex , Shapira Michael 
Published: February 2019

AbstractThe gut microbiota contributes to host health and fitness, and imbalances in its composition are associated with pathology. However, what shapes microbiota composition is not clear, in particular the role of genetic factors. Previous work in Caenorhabditis elegans defined a characteristic worm gut microbiota significantly influenced by host genetics. The current work explores the role of central regulators of host immunity and stress resistance, employing qPCR and CFU counts to measure abundance of core microbiota taxa in mutants raised on synthetic communities of previously-isolated worm gut commensals. This revealed a bloom, specifically of Enterobacter species, in immune-compromised TGFβ/BMP mutants. Imaging of fluorescently labeled Enterobacter showed that TGFβ/BMP-exerted control operated primarily in the anterior gut and depended on multi-tissue contributions. Enterobacter commensals are common in the worm gut, contributing to infection resistance. However, disruption of TGFβ/BMP signaling turned a normally beneficial Enterobacter commensal to pathogenic. These results demonstrate specificity in gene-microbe interactions underlying gut microbial homeostasis and highlight the pathogenic potential of their disruption.