scholarly journals Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth’s lower mantle

2021 ◽  
Author(s):  
Anna Gülcher ◽  
Maxim Ballmer ◽  
Paul Tackley
Keyword(s):  
Lower Mantle ◽  
Large Scale ◽  
Basal Layer ◽  
Global Scale ◽  
Physical Parameters ◽  
Mantle Heterogeneity ◽  
Mantle Evolution ◽  
Earth Like Planets ◽  
Material Volume

The nature of compositional heterogeneity in Earth’s lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermo- chemical mantle convection to investigate the coupled evolution and mixing of (intrinsically-dense) recycled and (intrinsically- strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma-ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyrs. Over a wide parameter range, primordial and recycled heterogeneity are predicted to co-exist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as mid-to-large scale blobs (or streaks) in the mid-mantle, around 1000-2000 km depth, and this preservation is largely independent on the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with an additional dense FeO-rich layer initially present at the base of the mantle, the ancient dense material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of such an ancient FeO-rich basal layer significantly aids the preservation of the viscous domains in the mid-mantle. Finally, we find that primordial blobs are commonly directly underlain by thick ROC piles, and aid their longevity and stability. Based on our results, we propose an integrated style of mantle heterogeneity for the Earth, involving the preservation of primordial domains along with recycled piles. This style has important implications for early Earth evolution, and has the potential of reconciling geophysical and geochemical discrepancies on present-day lower-mantle heterogeneity.

scholarly journals Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth's lower mantle

Solid Earth ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 2087-2107
Author(s):  
Anna Johanna Pia Gülcher ◽  
Maxim Dionys Ballmer ◽  
Paul James Tackley
Keyword(s):  
Lower Mantle ◽  
Large Scale ◽  
Basal Layer ◽  
Global Scale ◽  
Physical Parameters ◽  
Mantle Heterogeneity ◽  
Mantle Evolution ◽  
Earth Like Planets ◽  
Material Volume

Abstract. The nature of compositional heterogeneity in Earth's lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermochemical mantle convection to investigate the coupled evolution and mixing of (intrinsically dense) recycled and (intrinsically strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyr. Over a wide parameter range, primordial and recycled heterogeneity are predicted to co-exist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as medium- to large-scale blobs (or streaks) in the mid-mantle, around 1000–2000 km depth, and this preservation is largely independent of the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with an additional dense FeO-rich layer initially present at the base of the mantle, the ancient dense material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of such an ancient FeO-rich basal layer significantly aids the preservation of the viscous domains in the mid-mantle. Finally, we find that primordial blobs are commonly directly underlain by thick ROC piles and aid their longevity and stability. Based on our results, we propose an integrated style of mantle heterogeneity for the Earth involving the preservation of primordial domains along with recycled piles. This style has important implications for early Earth evolution and has the potential to reconcile geophysical and geochemical discrepancies on present-day lower-mantle heterogeneity.

scholarly journals Coupled dynamics and evolution of primordial and recycled heterogeneity in Earth's lower mantle

2020 ◽  
Author(s):  
Anna Johanna Pia Gülcher ◽  
Maxim Dyonis Ballmer ◽  
Paul James Tackley
Keyword(s):  
Lower Mantle ◽  
Large Scale ◽  
Basal Layer ◽  
Global Scale ◽  
Physical Parameters ◽  
Mantle Evolution ◽  
Earth Like Planets ◽  
Rich Material ◽  
Geochemical Constraints

Abstract. The nature of compositional heterogeneity in Earth’s lower mantle remains a long-standing puzzle that can inform about the long-term thermochemical evolution and dynamics of our planet. Here, we use global-scale 2D models of thermochemical mantle convection to investigate the coupled evolution and mixing of (intrinsically-dense) recycled and (intrinsically-strong) primordial heterogeneity in the mantle. We explore the effects of ancient compositional layering of the mantle, as motivated by magma-ocean solidification studies, and of the physical parameters of primordial material. Depending on these physical parameters, our models predict various regimes of mantle evolution and heterogeneity preservation over 4.5 Gyrs. Over a wide parameter range, primordial and recycled heterogeneity are predicted to coexist with each other in the lower mantle of Earth-like planets. Primordial material usually survives as mid-to-large scale blobs (or streaks) in the mid-mantle, around 1000–2000 km depth. This preservation is largely independent on the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as large piles at the base of the mantle and as small streaks everywhere else. In models with a dense FeO-rich layer that is initially present at the base of the mantle, the FeO-rich material partially survives at the top of ROC piles, causing the piles to be compositionally stratified. Moreover, the addition of an ancient FeO-rich basal layer in the lowermost mantle significantly aids the preservation of the viscous domains in the mid-mantle. Primordial blobs are commonly (but not always) directly underlain by thick ROC piles, and aid their longevity and stability. The preservation of primordial domains along with recycled piles is relevant for Earth as it may reconcile geophysical and geochemical constraints on lower mantle heterogeneity.

Coupled dynamics of primordial and recycled heterogeneity in Earth's lower mantle, and their present-day seismic signatures

2021 ◽  
Author(s):  
Anna J. P. Gülcher ◽  
Maxim D. Ballmer ◽  
Paul J. Tackley
Keyword(s):  
Oceanic Crust ◽  
Seismic Tomography ◽  
Lower Mantle ◽  
Large Scale ◽  
Numerical Models ◽  
Global Scale ◽  
Physical Parameters ◽  
Compositional Heterogeneity ◽  
Seismic Velocities ◽  
S Wave

<p>The nature of compositional heterogeneity in Earth’s lower mantle is a long-standing puzzle that can inform about the thermochemical evolution and dynamics of our planet. On relatively small scales (<1km), streaks of recycled oceanic crust (ROC) and lithosphere are distributed and stirred throughout the mantle, creating a “marble cake” mantle. On larger scales (10s-100s of km), compositional heterogeneity may be preserved by delayed mixing of this marble cake with either intrinsically-dense or -strong materials of e.g. primordial origin. Intrinsically-dense materials may accumulate as piles at the core-mantle boundary, while intrinsically viscous (e.g., enhanced in the strong mineral MgSiO<sub>3 </sub>bridgmanite) may survive as blobs in the mid-mantle for large timescales (i.e., as plums in the mantle “plum pudding”). So far, only few, if any, studies have quantified mantle dynamics in the presence of different types of heterogeneity with distinct physical properties.<br><br>Here, we use 2D numerical models of global-scale mantle convection to investigate the coupled evolution and mixing of (intrinsically-dense) recycled and (intrinsically-strong) primordial material. We explore the effects of ancient compositional layering of the mantle, as motivated by magma-ocean solidification studies, and the physical parameters of the primordial material. Over a wide parameter range, primordial and recycled heterogeneity is predicted to coexist with each other. Primordial material usually survives as mid-to-large scale blobs in the mid-mantle, and this preservation is largely independent on the initial primordial-material volume. In turn, recycled oceanic crust (ROC) persists as piles at the base of the mantle and as small streaks everywhere else. The robust coexistence between recycled and primordial materials in the models indicate that the modern mantle may be in a hybrid state between the “marble cake” and “plum pudding” styles.<br><br>Finally, we put our model predictions in context with geochemical studies on early Earth dynamics as well as seismic discoveries of present-day lower-mantle heterogeneity. For the latter, we calculate synthetic seismic velocities from output model fields, and compare these synthetics to tomography models, taking into account the limited resolution of seismic tomography. Because of the competing effects of compositional and thermal anomalies on S-wave velocities, it is difficult to identify mid-mantle bridgmanitic domains in seismic tomography images. This result suggests that, if present, bridgmanitic domains in the mid-mantle may be “hidden” from seismic tomographic studies, and other approaches are needed to establish the presence/absence of these domains in the present-day deep Earth.</p>

scholarly journals Long‐term predictability of soil moisture dynamics at the global scale: Persistence versus large‐scale drivers

2016 ◽  
Vol 43 (16) ◽  
pp. 8554-8562 ◽  
Author(s):  
Nadine Nicolai‐Shaw ◽  
Lukas Gudmundsson ◽  
Martin Hirschi ◽  
Sonia I. Seneviratne
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Global Scale ◽  
Soil Moisture Dynamics ◽  
Moisture Dynamics

scholarly journals Development of a global dataset of Wetland Area and Dynamics for Methane Modeling (WAD2M)

2020 ◽  
Author(s):  
Zhen Zhang ◽  
Etienne Fluet-Chouinard ◽  
Katherine Jensen ◽  
Kyle McDonald ◽  
Gustaf Hugelius ◽  
...  
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Southern Oscillation ◽  
Microwave Remote Sensing ◽  
Global Scale ◽  
Annual Maximum ◽  
Time Step ◽  
Wetland Area ◽  
Wetland Extent

Abstract. Seasonal and interannual variations in global wetland area is a strong driver of fluctuations in global methane (CH4) emissions. Current maps of global wetland extent vary with wetland definition, causing substantial disagreement and large uncertainty in estimates of wetland methane emissions. To reconcile these differences for large-scale wetland CH4 modeling, we developed a global Wetland Area and Dynamics for Methane Modeling (WAD2M) dataset at ~25 km resolution at equator (0.25 arc-degree) at monthly time-step for 2000–2018. WAD2M combines a time series of surface inundation based on active and passive microwave remote sensing at coarse resolution (~25 km) with six static datasets that discriminate inland waters, agriculture, shoreline, and non-inundated wetlands. We exclude all permanent water bodies (e.g. lakes, ponds, rivers, and reservoirs), coastal wetlands (e.g., mangroves and sea grasses), and rice paddies to only represent spatiotemporal patterns of inundated and non-inundated vegetated wetlands. Globally, WAD2M estimates the long-term maximum wetland area at 13.0 million km2 (Mkm2), which can be separated into three categories: mean annual minimum of inundated and non-inundated wetlands at 3.5 Mkm2, seasonally inundated wetlands at 4.0 Mkm2 (mean annual maximum minus mean annual minimum), and intermittently inundated wetlands at 5.5 Mkm2 (long-term maximum minus mean annual maximum). WAD2M has good spatial agreements with independent wetland inventories for major wetland complexes, i.e., the Amazon Lowland Basin and West Siberian Lowlands, with high Cohen's kappa coefficient of 0.54 and 0.70 respectively among multiple wetlands products. By evaluating the temporal variation of WAD2M against modeled prognostic inundation (i.e., TOPMODEL) and satellite observations of inundation and soil moisture, we show that it adequately represents interannual variation as well as the effect of El Niño-Southern Oscillation on global wetland extent. This wetland extent dataset will improve estimates of wetland CH4 fluxes for global-scale land surface modeling. The dataset can be found at http://doi.org/10.5281/zenodo.3998454 (Zhang et al., 2020).

The Necessity for Scale Up in R&D: Approach for Waste Immobilisation in Cement by BNFL

1995 ◽  
Vol 412 ◽  
Author(s):  
Graham A Fairhall ◽  
Eric W Miller
Keyword(s):  
Material Properties ◽  
Large Scale ◽  
Scale Up ◽  
Scaling Up ◽  
Full Scale ◽  
Physical Parameters ◽  
Wide Range ◽  
Regulatory Bodies ◽  
Major Factors

AbstractThe full scale processing of nuclear wastes immobilised in cement utilises a wide range of chemical and physical parameters. The success of this work however, involves many factors and material properties which are affected by the actual scaling up processes. The paper outlines the approach and experience gained by BNFL to recognise and evaluate the major factors involved in order to successfully produce large scale stable products acceptable to the appropriate regulatory bodies and suitable for long term disposal.

scholarly journals Spatiotemporal Comparison and Validation of Three Global-Scale Fractional Vegetation Cover Products

2019 ◽  
Vol 11 (21) ◽  
pp. 2524 ◽  
Author(s):  
Duanyang Liu ◽  
Kun Jia ◽  
Xiangqin Wei ◽  
Mu Xia ◽  
Xiwang Zhang ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Land Surface ◽  
Large Scale ◽  
High Spatial Resolution ◽  
Remote Sensing Data ◽  
Global Scale ◽  
Glass Product ◽  
Fractional Vegetation Cover ◽  
Temporal Profiles

Fractional vegetation cover (FVC) is an important parameter for many environmental and ecological models. Large-scale and long-term FVC products are critical for various applications. Currently, several global-scale FVC products have been generated with remote sensing data, such as VGT bioGEOphysical product Version 2 (GEOV2), PROBA-V bioGEOphysical product Version 3 (GEOV3) and Global LAnd Surface Satellite (GLASS) FVC products. However, studies comparing and validating these global-scale FVC products are rare. Therefore, in this study, the performances of three global-scale time series FVC products, including the GEOV2, GEOV3, and GLASS FVC products, are investigated to assess their spatial and temporal consistencies. Furthermore, reference FVC data generated from high-spatial-resolution data are used to directly evaluate the accuracy of these FVC products. The results show that these three FVC products achieve general agreements in terms of spatiotemporal consistencies over most regions. In addition, the GLASS and GEOV2 FVC products have reliable spatial and temporal completeness, whereas the GEOV3 FVC product contains much missing data over high-latitude regions, especially during wintertime. Furthermore, the GEOV3 FVC product presents higher FVC values than GEOV2 and GLASS FVC products over the equator. The main differences between the GEOV2 and GLASS FVC products occur over deciduous forests, for which the GLASS product presents slightly higher FVC values than the GEOV2 product during wintertime. Finally, temporal profiles of the GEOV2 and GLASS FVC products show better consistency than the GEOV3 FVC product, and the GLASS FVC product presents more reliable accuracy (R2 = 0.7878, RMSE = 0.1212) compared with the GEOV2 (R2 = 0.5798, RMSE = 0.1921) and GEOV3 (R2 = 0.7744, RMSE = 0.2224) FVC products over these reference FVC data.

scholarly journals Investigating Optimizing Mirror Orbits for Dark-side Illumination

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Kaisa Elisabeth Anne Crawford-Taylor
Keyword(s):  
Large Scale ◽  
Satellite Orbit ◽  
Dark Side ◽  
Satellite Orbits ◽  
Low Mass Stars ◽  
Earth Like Planets ◽  
Low Mass ◽  
Side Illumination ◽  
Selection Of

When a planet is tidally locked with its star, the same side always faces the star; thus one side is always dark. This synchronization occurs quickly for potentially habitable Earth-like planets orbiting dim, low-mass stars. Korpela, Sallmen, & Leystra Greene (2015; KSG) suggest that advanced extraterrestrial civilizations may put large-scale mirror fleets in orbit around such exoplanets to reflect starlight to the dark side of the planet. They might also use such mirrors to alter the climate of their own or another planet. Radiation pressure (RP) will be important for such large, lightweight mirrors, but research on satellite orbit stability typically neglects its effects. The long-term goal of this research is to determine fuel-efficient satellite orbits in situations where RP is important. We use Python and REBOUND to simulate mirrors orbiting an Earth-like exoplanet in the habitable zone for a variety of stars. Our simulations use two settings: “Always RP” always reflects starlight towards the planet’s center while “Nighttime RP” only does so on its dark side. We found mirrors survive longer when initially orbiting face on to the star compared to edge on. We present a selection of results illustrating how RP affects the mirror’s survival time.

scholarly journals Present and Future Observations of the Earthshine from Antarctica

2012 ◽  
Vol 8 (S288) ◽  
pp. 214-217 ◽  
Author(s):  
Danielle Briot ◽  
Luc Arnold ◽  
Stéphane Jacquemoud
Keyword(s):  
Global Scale ◽  
Spectral Signature ◽  
Research Station ◽  
The Moon ◽  
Spectral Signatures ◽  
The Earth ◽  
Earth Like Planets ◽  
Elementary Mapping ◽  
Absorption Features

AbstractIt is likely that images of Earth-like planets will be obtained in the next years. The first images will actually come down to single dots, in which biomarkers can be searched. Taking the Earth as a example of planet providing life, Earthshine observations showed that the spectral signature of photosynthetic pigments and atmospheric biogenic molecules was detectable, suggesting that, in principle, life on other planets could be detected on a global scale, if it is widely spread and distinguishable from known abiotic spectral signatures. As for the Earth, we already showed that the Vegetation Red Edge which is related to chlorophyll absorption features was larger when continents, versus oceans, were facing the Moon. It proved that an elementary mapping of a planet was even possible. In the frame of the LUCAS (LUmière Cendrée en Antarctique par Spectroscopie) project, the Earthshine has been measured in the Concordia Research Station (Dome C, Antarctica) long enough to observe variations corresponding to different parts of the Earth facing the Moon. An extension of this project, called LUCAS II, would allow long-term observations to detect seasonal variations in the vegetation signal. These data, together with precise measurements of the Earth's albedo, will help to validate a model of global and spectral albedo of our planet.

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