bluuebunny/crossref_metadata_2025_split huggingface dataset:
The GFDL Earth System Model Version 4.1 (GFDL‐ESM 4.1): Overall Coupled Model Description and Simulation Characteristics
Authors: Dunne J. P. , Horowitz L. W. , Adcroft A. J. , Ginoux P. , Held I. M. , John J. G. , Krasting J. P. , Malyshev S. , Naik V. , Paulot F. , Shevliakova E. , Stock C. A. , Zadeh N. , Balaji V. , Blanton C. , Dunne K. A. , Dupuis C. , Durachta J. , Dussin R. , Gauthier P. P. G. , Griffies S. M. , Guo H. , Hallberg R. W. , Harrison M. , He J. , Hurlin W. , McHugh C. , Menzel R. , Milly P. C. D. , Nikonov S. , Paynter D. J. , Ploshay J. , Radhakrishnan A. , Rand K. , Reichl B. G. , Robinson T. , Schwarzkopf D. M. , Sentman L. T. , Underwood S. , Vahlenkamp H. , Winton M. , Wittenberg A. T. , Wyman B. , Zeng Y. , Zhao M. 
Published: August 2020

AbstractWe describe the baseline coupled model configuration and simulation characteristics of GFDL's Earth System Model Version 4.1 (ESM4.1), which builds on component and coupled model developments at GFDL over 2013–2018 for coupled carbon‐chemistry‐climate simulation contributing to the sixth phase of the Coupled Model Intercomparison Project. In contrast with GFDL's CM4.0 development effort that focuses on ocean resolution for physical climate, ESM4.1 focuses on comprehensiveness of Earth system interactions. ESM4.1 features doubled horizontal resolution of both atmosphere (2° to 1°) and ocean (1° to 0.5°) relative to GFDL's previous‐generation coupled ESM2‐carbon and CM3‐chemistry models. ESM4.1 brings together key representational advances in CM4.0 dynamics and physics along with those in aerosols and their precursor emissions, land ecosystem vegetation and canopy competition, and multiday fire; ocean ecological and biogeochemical interactions, comprehensive land‐atmosphere‐ocean cycling of CO2, dust and iron, and interactive ocean‐atmosphere nitrogen cycling are described in detail across this volume of JAMES and presented here in terms of the overall coupling and resulting fidelity. ESM4.1 provides much improved fidelity in CO2 and chemistry over ESM2 and CM3, captures most of CM4.0's baseline simulations characteristics, and notably improves on CM4.0 in (1) Southern Ocean mode and intermediate water ventilation, (2) Southern Ocean aerosols, and (3) reduced spurious ocean heat uptake. ESM4.1 has reduced transient and equilibrium climate sensitivity compared to CM4.0. Fidelity concerns include (1) moderate degradation in sea surface temperature biases, (2) degradation in aerosols in some regions, and (3) strong centennial scale climate modulation by Southern Ocean convection.
Methane Emissions in a Chemistry‐Climate Model: Feedbacks and Climate Response
Authors: Heimann I. , Griffiths P. T. , Warwick N. J. , Abraham N. L. , Archibald A. T. , Pyle J. A. 
Published: August 2020

AbstractUnderstanding the past, present, and future evolution of methane remains a grand challenge. Here we have used a hierarchy of models, ranging from simple box models to a chemistry‐climate model (CCM), UM‐UKCA, to assess the contemporary and possible future atmospheric methane burden. We assess two emission data sets for the year 2000 deployed in UM‐UKCA against key observational constraints. We explore the impact of the treatment of model boundary conditions for methane and show that, depending on other factors, such as CO emissions, satisfactory agreement may be obtained with either of the CH4 emission data sets, highlighting the difficulty in unambiguous choice of model emissions in a coupled chemistry model with strong feedbacks. The feedbacks in the CH4‐CO‐OH system, and their uncertainties, play a critical role in the projection of possible futures. In a future driven by large increases in greenhouse gas forcing, increases in tropospheric temperature drive, an increase in water vapor, and, hence, [OH]. In the absence of methane emission changes this leads to a significant decrease in methane compared to the year 2000. However, adding a projected increase in methane emissions from the RCP8.5 scenario leads to a large increase in methane abundance. This is modified by changes to CO and NOx emissions. Clearly, future levels of methane are uncertain and depend critically on climate change and on the future emission pathways of methane and ozone precursors. We highlight that further work is needed to understand the coupled CH4‐CO‐OH system in order to understand better future methane evolution.
The Effectiveness of the South‐to‐North Water Diversion Middle Route Project on Water Delivery and Groundwater Recovery in North China Plain
Authors: Zhang Chong , Duan Qingyun , Yeh Pat J.‐F. , Pan Yun , Gong Huili , Gong Wei , Di Zhenhua , Lei Xiaohui , Liao Weihong , Huang Zhiyong , Zheng Longqun , Guo Xueru 
Published: August 2020

AbstractThe South‐to‐North Water Diversion Middle Route Project (MRP), which started its operation in December 2014, was designed to transfer water from Danjiangkou Reservoir (DR) in Hanjiang River Basin to North China Plain (NCP) to alleviate water shortage and long‐term groundwater depletion in the water‐receiving region. This study investigates the effectiveness of actual MRP operation during 2015–2018 using the observed water budget data collected from DR and the groundwater level data from 559 monitoring wells. Assuming that MRP was in operation during 2005–2014, ensemble water diversion simulations were performed to study the sensitivity of MRP effectiveness to two important factors: the downstream water demand of DR (Dwd) and the ratio (Ir) of water diversion volume (Qd) replacing groundwater pumping in NCP. Even though the observed and simulated mean annual Qd during 2015–2018 (i.e., 4.3 and 7.0 km3/year, respectively) failed to meet the original water delivery target of 9.5 km3/year due to its short operation and the coincidence with a dry cycle, MRP is effective in groundwater recovery as an increasing trend (+0.3 km3/year) in groundwater storage (GWS) was observed in NCP during 2015–2018. MRP's effectiveness is sensitive to Dwd and Ir. Dwd should not exceed 23.0 km3/year to guarantee Qd reaching the original target, and Ir should not be less than 33% to guarantee GWS recovery. Those findings suggest that a reasonable decrease of Dwd and an increase of Ir are the recommended pathway to ensure the effectiveness of MRP in meeting both water delivery and groundwater recovery targets.
Modeling Transition Metals in East Asia and Japan and Its Emission Sources
Authors: Kajino Mizuo , Hagino Hiroyuki , Fujitani Yuji , Morikawa Tazuko , Fukui Tetsuo , Onishi Kazunari , Okuda Tomoaki , Kajikawa Tomoki , Igarashi Yasuhito 
Published: August 2020

AbstractEmission inventories of anthropogenic transition metals, which contribute to aerosol oxidative potential (OP), in Asia (Δx = 0.25°, monthly, 2000–2008) and Japan (Δx = 2 km, hourly, mainly 2012) were developed, based on bottom‐up inventories of particulate matters and metal profiles in a speciation database for particulate matters. The new inventories are named Transition Metal Inventory (TMI)‐Asia v1.0 and TMI‐Japan v1.0, respectively. It includes 10 transition metals in PM2.5 and PM10, which contributed to OP based on reagent experiments, namely, Cu, Mn, Co, V, Ni, Pb, Fe, Zn, Cd, and Cr. The contributions of sectors in the transition metals emission in Japan were also investigated. Road brakes and iron‐steel industry are primary sources, followed by other metal industry, navigation, incineration, power plants, and railway. In order to validate the emission inventory, eight elements such as Cu, Mn, V, Ni, Pb, Fe, Zn, and Cr in anthropogenic dust and those in mineral dust were simulated over East Asia and Japan with Δx = 30 km and Δx = 5 km domains, respectively, and compared against the nation‐wide seasonal observations of PM2.5 elements in Japan and the long‐term continuous observations of total suspended particles (TSPs) at Yonago, Japan in 2013. Most of the simulated elements generally agreed with the observations, while Cu and Pb were significantly overestimated. This is the first comprehensive study on the development and evaluation of emission inventory of OP active elements, but further improvement is needed.
Public Health and Climate Benefits and Trade‐Offs of U.S. Vehicle Electrification
Authors: Peters D. R. , Schnell J. L. , Kinney P. L. , Naik V. , Horton D. E. 
Published: August 2020

AbstractVehicle electrification is a common climate change mitigation strategy, with policymakers invoking co‐beneficial reductions in carbon dioxide (CO2) and air pollutant emissions. However, while previous studies of U.S. electric vehicle (EV) adoption consistently predict CO2 mitigation benefits, air quality outcomes are equivocal and depend on policies assessed and experimental parameters. We analyze climate and health co‐benefits and trade‐offs of six U.S. EV adoption scenarios: 25% or 75% replacement of conventional internal combustion engine vehicles, each under three different EV‐charging energy generation scenarios. We transfer emissions from tailpipe to power generation plant, simulate interactions of atmospheric chemistry and meteorology using the GFDL‐AM4 chemistry climate model, and assess health consequences and uncertainties using the U.S. Environmental Protection Agency Benefits Mapping Analysis Program Community Edition (BenMAP‐CE). We find that 25% U.S. EV adoption, with added energy demand sourced from the present‐day electric grid, annually results in a ~242 M ton reduction in CO2 emissions, 437 deaths avoided due to PM2.5 reductions (95% CI: 295, 578), and 98 deaths avoided due to lesser ozone formation (95% CI: 33, 162). Despite some regions experiencing adverse health outcomes, ~$16.8B in damages avoided are predicted. Peak CO2 reductions and health benefits occur with 75% EV adoption and increased emission‐free energy sources (~$70B in damages avoided). When charging‐electricity from aggressive EV adoption is combustion‐only, adverse health outcomes increase substantially, highlighting the importance of low‐to‐zero emission power generation for greater realization of health co‐benefits. Our results provide a more nuanced understanding of the transportation sector's climate change mitigation‐health impact relationship.
Genesis of the Antarctic Slope Current in West Antarctica
Authors: Thompson Andrew F. , Speer Kevin G. , Schulze Chretien Lena M. 
Published: August 2020

AbstractThe stability of the West Antarctic Ice Sheet (WAIS) depends on ocean heat transport toward its base and remains a source of uncertainty in sea level rise prediction. The Antarctic Slope Current (ASC), a major boundary current of the ocean's global circulation, serves as a dynamic gateway for heat transport toward Antarctica. Here, we use observations collected from the Bellingshausen Sea to propose a mechanistic explanation for the initiation of the westward‐flowing ASC. Waters modified throughout the Bellingshausen Sea by ocean‐sea‐ice and ocean‐ice‐shelf interactions are exported to the continental slope in a narrow, topographically steered western boundary current. This focused outflow produces a localized front at the shelf break that supports the emerging ASC. This mechanism emphasizes the importance of buoyancy forcing, integrated over the continental shelf, as opposed to local wind forcing, in the generation mechanism and suggests the potential for remote control of melt rates of WAIS' largest ice shelves.
Temperature and Fluid Pressurization Effects on Frictional Stability of Shale Faults Reactivated by Hydraulic Fracturing in the Changning Block, Southwest China
Authors: An Mengke , Zhang Fengshou , Chen Zhaowei , Elsworth Derek , Zhang Lianyang 
Published: August 2020

AbstractA shale fault reactivated during multistage hydraulic fracturing in the Changning block in the Sichuan Basin, southwest China, accompanied a cluster of small earthquakes with the largest reaching ML ~ 0.8. We illuminate the underlying mechanisms of fault reactivation through measurements of frictional properties on simulated fault gouge under hydrothermal conditions. Velocity‐stepping experiments were performed at a confining pressure of 60 MPa, temperatures from 30 to 300°C, pore fluid pressures from 10 to 55 MPa, and shear velocities between 0.122 and 1.22 μm/s. Results show that the gouge is frictionally strong with coefficient of friction of 0.6–0.7 across all experimental conditions. At observed in situ pore fluid pressure (30 MPa), the slip stability response is characterized by velocity strengthening at temperatures of 30–200°C and velocity weakening at temperatures of 250–300°C. Increasing the pore fluid pressure can increase values of (a − b) at temperatures ≥200°C, narrowing the temperature range where velocity weakening occurs. At the in situ temperature (90°C), the simulated gouge shows only velocity strengthening behavior and aseismic slip at elevated pore fluid pressures, contrary to the observed seismicity. We postulate that the aseismic slip at elevated pore fluid pressures may trigger seismicity by activating adjacent earthquake‐prone faults.
The Lithospheric Structure of the Gibraltar Arc System From Wide‐Angle Seismic Data
Authors: Gómez de la Peña Laura , Grevemeyer Ingo , Kopp Heidrun , Díaz Jordi , Gallart Josep , Booth‐Rea Guillermo , Gràcia Eulàlia , R. Ranero César 
Published: August 2020

AbstractIn continental settings, seismic failure is generally restricted to crustal depth. Crustal structure is therefore an important proxy to evaluate seismic hazard of continental fault systems. Here we present a seismic velocity model across the Gibraltar Arc System, from the Eurasian Betics Range (South Iberian margin), across offshore East Alboran and Pytheas (African margin) basins, and ending onshore in North Morocco. Our results reveal the nature and configuration of the crust supporting the coexistence of three different crustal domains: the continental crust of the Betics, the continental crust of the Pytheas Basin (south Alboran Basin) and onshore Morocco, and a distinct domain formed of magmatic arc crust under the East Alboran Basin. The magmatic arc under the East Alboran Basin is characterized by a velocity structure containing a relatively high‐velocity lower crust (~7 km/s) bounded at the top and base by reflections. The lateral extension of this crust is mapped integrating a second perpendicular wide‐angle seismic profile along the Eastern Alboran basin, together with basement samples, multibeam bathymetry, and a grid of deep‐penetrating multichannel seismic profiles. The transition between crustal domains is currently unrelated to extensional and magmatic processes that formed the basin. The abrupt transition zones between the different crustal domains support that they are bounded by crustal‐scale active fault systems that reactivate inherited structures. Seismicity in the area is constrained to upper‐middle crust depths, and most earthquakes nucleate outside of the magmatic arc domain.
A Comparison on the E‐Change Pulses Occurring in the Bi‐Level Polarity‐Opposite Charge Regions of the Intracloud Lightning Flashes
Authors: Shi Dongdong , Wang Daohong , Wu Ting , Takagi Nobuyuki 
Published: August 2020

AbstractWe have compared the E‐change pulses occurring in the upper positive charge region (UPCR) and the middle negative charge region (MNCR) of 41 normal intracloud (IC) flashes. E‐change pulses can be roughly grouped into isolated pulses and pulse trains with both positive and negative polarities. Although isolated pulses occurred about equally in UPCR and MNCR, there were much more pulse trains in MNCR than UPCR. Overall, the average amplitude, rise time, half‐peak width, and fall time of isolated pulses (pulse trains) are 56% larger (115% larger), 31% faster (43% slower), 25% narrower (46% wider), and 26% shorter (62% longer) in UPCR than in MNCR. Interestingly, in the same charge region, positive and negative pulses share similar characteristics. Based on a typical well‐structured IC, it was found that the majority of isolated pulses in both UPCR and MNCR occurred at or close to the leader tips. In contrast, about 30% UPCR pulse trains occurred at or close to the tip, while the remaining 70% pulse trains occurred in the leader channel retracing along the leader channel away from the flash origin; for MNCR pulse trains, about 60% occurred close to the tip, and 40% occurred in the channel with a backward extension to the flash origin. Based on these characteristics, we have discussed the physical nature of various types of pulses and pointed out that a leader is likely to progress with a fluctuating behavior when it is neutralizing space charge distributed in a region with sufficient thickness and width.
Integrating Suspended Sediment Flux in Large Alluvial River Channels: Application of a Synoptic Rouse‐Based Model to the Irrawaddy and Salween Rivers
Authors: Baronas J. Jotautas , Stevenson Emily I. , Hackney Christopher R. , Darby Stephen E. , Bickle Michael J. , Hilton Robert G. , Larkin Christina S. , Parsons Daniel R. , Myo Khaing Aung , Tipper Edward T. 
Published: August 2020

AbstractA large portion of freshwater and sediment is exported to the ocean by a small number of major rivers. Many of these megarivers are subject to substantial anthropogenic pressures, which are having a major impact on water and sediment delivery to deltaic ecosystems. Due to hydrodynamic sorting, sediment grain size and composition vary strongly with depth and across the channel in large rivers, complicating flux quantification. To account for this, we modified a semi‐empirical Rouse model, synoptically predicting sediment concentration, grain‐size distribution, and organic carbon (%OC) concentration with depth and across the river channel. Using suspended sediment depth samples and flow velocity data, we applied this model to calculate sediment fluxes of the Irrawaddy (Ayeyarwady) and the Salween (Thanlwin), the last two free‐flowing megarivers in Southeast Asia. Deriving sediment‐discharge rating curves, we calculated an annual sediment flux of
Mt/year for the Irrawaddy and
Mt/year for the Salween, together exporting 46% as much sediment as the Ganges‐Brahmaputra system. The mean flux‐weighted sediment exported by the Irrawaddy is significantly coarser (D84 = 193 ± 13 μm) and OC‐poorer (0.29 ± 0.08 wt%) compared to the Salween (112 ± 27 μm and 0.59 ± 0.16 wt%, respectively). Both rivers export similar amounts of particulate organic carbon, with a total of
Mt C/year, 53% as much as the Ganges‐Brahmaputra. These results underline the global significance of the Irrawaddy and Salween rivers and warrant continued monitoring of their sediment flux, given the increasing anthropogenic pressures on these river basins.
Improving Data‐Driven Global Weather Prediction Using Deep Convolutional Neural Networks on a Cubed Sphere
Authors: Weyn Jonathan A. , Durran Dale R. , Caruana Rich 
Published: August 2020

AbstractWe present a significantly improved data‐driven global weather forecasting framework using a deep convolutional neural network (CNN) to forecast several basic atmospheric variables on a global grid. New developments in this framework include an off‐line volume‐conservative mapping to a cubed‐sphere grid, improvements to the CNN architecture and the minimization of the loss function over multiple steps in a prediction sequence. The cubed‐sphere remapping minimizes the distortion on the cube faces on which convolution operations are performed and provides natural boundary conditions for padding in the CNN. Our improved model produces weather forecasts that are indefinitely stable and produce realistic weather patterns at lead times of several weeks and longer. For short‐ to medium‐range forecasting, our model significantly outperforms persistence, climatology, and a coarse‐resolution dynamical numerical weather prediction (NWP) model. Unsurprisingly, our forecasts are worse than those from a high‐resolution state‐of‐the‐art operational NWP system. Our data‐driven model is able to learn to forecast complex surface temperature patterns from few input atmospheric state variables. On annual time scales, our model produces a realistic seasonal cycle driven solely by the prescribed variation in top‐of‐atmosphere solar forcing. Although it currently does not compete with operational weather forecasting models, our data‐driven CNN executes much faster than those models, suggesting that machine learning could prove to be a valuable tool for large‐ensemble forecasting.
Patagonian Aridification at the Onset of the Mid‐Miocene Climatic Optimum
Authors: Trayler Robin B. , Kohn Matthew J. , Bargo M. Susana , Cuitiño José I. , Kay Richard F. , Strömberg Caroline A. E. , Vizcaíno Sergio F. 
Published: August 2020

AbstractFossil‐rich sediments of the Santa Cruz Formation, Patagonia, Argentina, span the initiation of the Miocene Climatic Optimum (MCO), the most recent period of warm and wet conditions in the Cenozoic. These conditions drove the expansion of tropical and subtropical ecosystems to much higher latitudes, with the fossiliferous Santa Cruz Formation recording one of the southernmost examples. We collected new carbon and oxygen isotope compositions of herbivore tooth enamel from fossils ~17.4 to 16.4 Ma in age to investigate ecological and climatic changes across the initiation of the MCO. Enamel δ13C values are consistent with a C3‐dominated ecosystem with moderate precipitation and a mix of wooded and more open areas. Serially sampled teeth reveal little zoning in δ13C and δ18O values, suggesting little seasonal variation in water and plant isotope compositions or seasonal changes in diet. Carbon isotope‐based estimates of mean annual precipitation (MAP) are consistent with aridification, with MAP decreasing from ~1,000 ± 235 mm/yr at 17.4 Ma to ~525 ± 105 mm/yr at the start of the climatic optimum (~16.9 Ma). This decrease corresponds to increasing global temperatures, as indicated by marine proxy records, and was followed by a rebound to ~840 ± 270 mm/yr by ~16.4 Ma. In comparison to a modern mean annual temperature (MAT) in the region of ~8°C, oxygen isotopes indicate high MAT (at least 20°C) at the onset of the MCO at 16.9 Ma and a significant increase in MAT to ~25°C by 16.4 Ma.
Seismic Coupling Quantified on Inferred Décollements Beneath the Western Syntaxis of the Himalaya
Authors: Jouanne François , Munawar Naveed , Mugnier Jean‐Louis , Ahmed Awais , Awan Adnan Alam , Bascou Pascale , Vassallo Riccardo 
Published: August 2020

AbstractWe used episodic GNSS measurements to quantify the present‐day velocity field in the northwestern Himalaya from the Himalayan foreland to the Karakoram Range. We report a progressive N‐S compressional velocity gradient with two noticeable exceptions: in the Salt Range, where important southward velocities are recorded, and in Nanga Parbat, where an asymmetrical E‐W velocity gradient is recorded. A review of Quaternary slip along active thrusts both in and out of sequence allows us to propose a 14 mm/yr shortening rate. This constraint, together with a geometrical model of the Main Himalayan Thrust (MHT), allows us to propose estimations of the slip distributions along the active faults. The lower flat of the MHT is characterized by ductile slip, whereas the coupling increases along the crustal ramp and along the upper flat of the MHT. The basal thrust of the Potwar Plateau and Salt Range presents weak coupling, which is interpreted as the existence of a massive salt layer forming an excellent décollement. In the central part of the frontal Salt Range, the velocities suggest the existence of a southward horizontal flux in the massive salt layer. The simulations also suggest that the velocities recorded in Nanga Parbat can be explained by active westward thrusting along the fault that borders the massif to the west. Simulations suggest that the slip along this fault evolves with depth from 5 mm/yr ductile slip near the MHT to no slip along the upper part of the fault.