Quantitative Numerical Models Research Articles

Evaluation of emission reduction and other societal and environmental outcomes: Structured decision making for the Louisiana climate action plan

Climate action planning continues to accelerate rapidly across the globe as communities seek to prepare to thrive in an uncertain future. Climate action planning is a particularly contentious and complex topic in the southern United States, however, because of significant economic reliance on industries that contribute substantially to greenhouse gas emissions, and due to a complicated relationship between industry and persistent racial and economic inequities that contribute to distrust between communities, businesses, and state governments. Within the last decade, research efforts have begun to evaluate approaches used to develop city, state, and national-level climate action plans, finding that planning efforts are often as diverse as the localities they represent. Climate action planning processes that evaluate the potential implications of climate action on greenhouse gas emissions and societal values are often driven by either qualitative stakeholder engagement or by the results of numerical models. While both approaches are valuable, they also have limitations that can result in climate action plans that are unrealistic or unimplementable. Limited research is available that assesses planning efforts that integrate multiple evaluation methodologies. In this study, we evaluate the strengths and limitations of integrating qualitative and quantitative climate action evaluation methodologies in a planning process grounded in structured decision making using Louisiana as a case study. This mixed method planning approach applied both quantitative numerical models and qualitative expert elicitation to evaluate potential implications of climate action for Louisiana. We found that integration of approaches through a transparent, structured, and objectives-orientated process allowed for robust analysis of potential climate actions while engendering process buy-in across diverse stakeholder interests. This process ultimately resulted in the unanimous adoption of Louisiana's climate action plan, characterized by a wholistic and implementable set of climate actions balanced against the values of Louisianians. The process outlined in this study represents a replicable approach for other climate action planning efforts.

Geoid Reveals the Density Structure of Cratonic Lithosphere

AbstractGeoid is a key observable for understanding the dynamics of the deep Earth, but has been considered largely transparent to long‐wavelength shallow density structures, especially those of the cratonic lithosphere. Here, we demonstrate that the observed flat craton‐ocean geoid pattern, traditionally interpreted as reflecting neutrally buoyant cratonic keels, provides critical constraints on both the net buoyancy and the depth‐dependent density distribution of cratonic mantle lithosphere. Using both simple theoretical calculations and quantitative numerical models, we show that the recent seismic data on lithospheric structure require the existence of a dense cratonic mantle lithosphere to explain the observed topography and geoid. In practice, topography reveals the net buoyancy of the cratonic lithosphere, while geoid further delineates the depth‐dependence of excess density. We find that the mantle lithosphere below large cratons bears net negative buoyancy close to that of a pure‐thermal lithosphere, with most of the excess density distributed within the lower half of the lithosphere. Density profiles of small cratons, due to strong edge effects from surrounding orogenic belts, are harder to constrain, except that their mantle lithosphere is also negatively buoyant.

How do carbonate factories influence carbonate platform morphology? Exploring production−transport interactions with numerical forward modelling

AbstractUnderstanding how carbonate factories influence platform evolution is either based on qualitative conceptual models or quantitative numerical stratigraphic forward models. This study establishes new production depth profiles for four Cenozoic carbonate factories and uses two‐dimensional stratigraphic forward models to explore how interactions between sediment production and transport within carbonate systems influence carbonate platform development. Newly established production/depth profiles are used to model photozoan and heterozoan carbonate grain associations, and the associated carbonate producing factories, and results are compared with well‐studied outcrop successions. Sediment production from photozoan and heterozoan grain associations is also equalized, so that the total sediment production is the same but the depth/production profiles retain their distinctly different form. Thus, the effect of the different production profiles can be assessed. Ramps form when sediment diffusional transport rates are high relative to production rates and flat‐top steep‐margin platforms form when sediment diffusional transport rates are low relative to production rates, whether they are photozoan or heterozoan grain associations. The control exerted by sediment production and transport is expressed as a sediment transport–production ratio where transport ratio is a diffusional sediment transport in two‐dimensions and production ratio is the total sediment production rate which is the product of a production profile that varies in depth and laterally. The transport–production ratio is a key control on the evolution and geometry of carbonate platforms. This is the case with different production profiles (both euphotic and oligophotic) and in mixed grain‐size and mixed transport‐rate systems. Carbonate producing factories significantly influence the rate of sediment production, the depth distribution of sediment production (production profiles), as well as the type of grain sizes produced (influencing resistance to erosion). Thus, different types of carbonate grain associations, and the associated carbonate producing factories, can produce the critical differences between carbonate platform geometries.

Strain, stress, and mechanical relaxation in fin-patterned Si/SiGe multilayers for sub-7 nm nanosheet gate-all-around device technology

Pre-strained fin-patterned Si/SiGe multilayer structures for sub-7 nm stacked gate-all-around Si-technology transistors that have been grown onto bulk-Si, virtually relaxed SiGe, strained Silicon-On-Insulator, and compressive SiGe-On-Insulator were investigated. From strain maps with a nanometer spatial resolution obtained by transmission electron microscopy, we developed 3D quantitative numerical models describing the mechanics of the structures. While elastic interactions describe every other system reported here, the patterning on the compressive SiGe-On-Insulator substrate that is fabricated by Ge-condensation results in relaxation along the semiconductor/insulator interface, revealing a latent plasticity mechanism. As a consequence, Si layers with a uniaxial stress of 1.4 GPa are obtained, bringing fresh perspectives for strain engineering in advanced devices. These findings could be extended to other semiconductor technologies.

First report of Paleoproterozoic incipient charnockite from the North China Craton: Implications for ultrahigh-temperature metasomatism

The assembly of crustal blocks within the North China Craton (NCC) at the terminal stage of craton building during Paleoproterozoic witnessed major subduction-collision events. Here we illustrate a case where hot and anhydrous magmas emplaced in the lower crust during the early Paleoproterozoic subduction realm in the NCC led to the formation of orthopyroxene-bearing dehydrated zones of incipient charnockites within the adjacent TTG (tonalite-trondhjemite-granodiorite) suite. The coarse greenish anhydrous zones of incipient charnockite show an assemblage of antiperthitic plagioclase+orthopyroxene+K-feldspar+quartz with minor clinopyroxene, ilmenite+magnetite and secondary biotite. The peak P–T conditions of the incipient charnockite are estimated as 890–970°C and 3.5–6.5kbar based on mineral chemical analysis and pseudosection modeling in the system NCKFMASHTO, suggesting ultra-high temperature metasomatism, and the ‘hottest incipient charnockites’ so far reported. Zircons from the massive charnockite show oscillatory-zoned magmatic cores with high Th/U values rimmed by unzoned and luminescent thin metamorphic overgrowths. A concordant group of magmatic zircons yields weighted mean 207Pb/206Pb age of 2401±29Ma, and a lower intercept age of ca. 1834±81Ma. A similar concordant group of zircons from the TTG yields a weighted mean 207Pb/206Pb age of 2446±18Ma and a weighted mean lower intercept age of 1834±47Ma. The ca. 2.45Ga age from the TTG and 2.40 age from the charnockite are taken to represent the magma emplacement ages, and the identical 1.83Ga from zircons in both rocks denoting the timing of late Paleoproterozoic metamorphism. Lu–Hf analysis of magmatic cores of the zircons from the charnockite and the TTG show clear positive ɛHf(t) values (1.2–5.9), suggesting juvenile sources.The formation of incipient charnockite zones close to the contact with the charnockite pluton is consistent with the quantitative numerical models that predict CO2 migration in anhydrous silicate melt and metasomatic fluid from a rapidly cooling pluton. The ultra-high temperature metasomatism and solid-state reaction generating the incipient charnockites provide important insights on CO2 advection from lower crustal magmas during Paleoproterozoic orogeny in the North China Craton.

Backward stacking of submarine channel–fan successions controlled by strike-slip faulting: The Izumi Group (Cretaceous), southwest Japan

Field surveys and numerical simulations were conducted to examine lithostratigraphic cyclicity in strike-slip basins, which is still poorly understood due to its complexity. The basin-filling processes in strike-slip basins are closely associated with regional tectonics represented by configuration of faults and spatial/temporal variations in the slip rate. We attempted to bridge the gap between qualitative sedimentary facies analyses and quantitative numerical models in order to better understand the formation of these sedimentary successions. This paper focuses on the Izumi Group (Upper Cretaceous), southwest Japan, which was deposited in an elongate basin (300 km long by 10–20 km wide) along the Median Tectonic Line, which at the time of deposition was a sinistral strike-slip fault related to oblique subduction along a forearc margin. The depositional environments of the group were deduced from five lithofacies associations (LAs): submarine channel-fill facies (LA I), proximal facies of lobes or frontal splays (LA II), distal facies of lobes or frontal splays (LA III), slope-apron facies (LA IV), and basin floor facies (LA V). LAs I–III represent point-sourced submarine channel–fan successions in the axial facies, with unidirectional paleocurrent directions from ENE to WSW, and LAs IV–V constitute the marginal facies, the paleoslope of which dipped to the SSW. Two units of submarine channel–fan successions are stacked with ~10 km of eastward (backward) shift. Each unit shows a cyclic lithostratigraphy of rapid upward coarsening and thickening in the lower part (~350 m thick) and gradual upward fining and thinning in the upper part (1–3.5 km thick). It is estimated to have taken 5–7 × 10 5 yr for 10 km offset on each stratigraphic unit based on the depositional ages. Although many processes can control the stratigraphic architecture, such as global and local sea level, climate, and tectonics, the stratigraphic cyclicity observed in the study area is closely related to the depocenter migration, suggesting that fault movement was the primary control on the stratigraphy. On the assumption that the formation and filling processes of the Izumi sedimentary basin were basically controlled by strike-slip faults, a numerical simulation suggests that episodic changes in fault-slip rate or sediment-supply rate could control the stratigraphic cyclicity. In this paper, we propose a model where cyclic stratigraphy is ascribed to temporal variations of fault activity controlling accommodation generation, sediment supply, and relative sea level, which could generate cyclic stratigraphy associated with depocenter migration in strike-slip basins.

Field investigation and numerical simulation toward the control of longshore sediment transport on Laura islet in Majuro Atoll

Although the sustainable land use is a significant issue in the atoll islands, the quantitative information and numerical models of island changes are lacked. In this study, the measurements of beach profiles were carried out in Laura islet located in the western part of Majuro Atoll, Marshall Islands. Comparing our measurement results with the previous SOPAC's profiles revealed the quantitative profile changes during the last decade: from 1997 to 2007. We also reproduced these profile changes by the numerical model which was based on longshore sediment transport system. The calculated results and the measured profile changes showed a good agreement. And, the artificial control of longshore sediment transport was considered one of the valuable ways for sustainable land management on sandy beach of Laura islet.

Crystal nucleation in hydrous rhyolite: Experimental data applied to classical theory

Feldspar nucleation rate data obtained by laboratory decompression of hydrous silicate melt are interpreted in view of the classical theory of nucleation (CNT) and a non-classical variation, the diffuse-interface theory (DIT). The nucleation rate data can be modeled by the CNT formalism only if the interfacial free energy (σ) is allowed to vary as a function of composition. The values thus obtained vary by a factor of four (0.024–0.100 J/m2) and decrease systematically over a sixfold increase in dissolved H2O content (0.8–4.8 wt%). This result is qualitatively consistent with the effects of dissolved H2O on the liquid-vapor interfacial free energy in haplogranite magma (Mangan and Sisson 2000) and the liquid-crystal interfacial free energy in the one-component Li-disilicate system (Davis et al. 1997). The DIT states that the interfacial region between the bulk solid and bulk melt has thermodynamic properties intermediate between these phases, and that σ is defined as the difference between the interfacial enthalpy ( H int) and interfacial entropy ( TS int). If the DIT model is correct, the nucleation rate data for feldspar may indicate that: (1) dissolved H2O content controls the spatial distribution of enthalpy and configurational entropy around incipient crystals, and (2) the spatial gradients of these potentials diverge during devolatilization. This study suggests that crystal nucleation studies may yield insights into the structure and thermodynamics of hydrous melts; likewise, experimental studies are important for refining a physical understanding of nucleation phenomena. Our results can be applied to quantitative numerical models of ascent-driven magma crystallization.

Mechanical aspects of continental rifting

Continental rifting is associated with characteristic processes such as crustal extension and vertical movements observed on the surface, and deep-seated phenomena such as lithospheric thinning and upwelling of mantle material. These characteristics are expressed in a variety of geophysical anomalies; increased heat flow, low long wavelength Bouguer gravity with relative gravity high along the rift, delayed body-wave travel times, as well as by volcanic activity with various depth of magma source. We discuss the concepts of rifting by either lateral or vertical transmission of mechanical energy on the basis of several quantitative numerical models. The results suggest that, in particular, plate collision and plate bending at hot spots fail as self supporting mechanisms of rifting because of the mechanical problems of transmitting the necessary energy over the required distances. Lithospheric stretching mechanisms have been rejected on the basis of geothermal arguments. Mantle diapir models are discussed in detail with reference to the initiation and diapir phases of development, and the induced stress regime. The typical wavelength of continental rifts requires the existence of a distinct crustal layer. Even with a low amplitude diapir, the ascending mantle material deforms the upper layers by necking and doming. Modelled rates of mantle diapirism satisfy the available constraints from data. The maximum rate of diapiric ascent coincides with the maximum rate of crustal extension, which is, however, confined to a narrow surface zone. The stress regime becomes drastically altered by the structural changes at the crust-mantle boundary, induced by a crustal mass excess developed during rifting. There is a substantial decrease in the amount of extensive stresses after structural modification during rifting, and possibly even a change to a compressive stress regime. Such changes are related to the development into the so-called fossil grabens beneath basins. The initiation and development of elongated mantle diapirs is the only concept that explains the majority of phenomena associated with continental rifting.