255,974 research outputs found
Remote Sensing by Satellite Gravimetry
Over the last two decades, satellite gravimetry has become a new remote sensing technique that provides a detailed global picture of the physical structure of the Earth. With the CHAMP, GRACE, GOCE and GRACE Follow-On missions, mass distribution and mass transport in the Earth system can be systematically observed and monitored from space. A wide range of Earth science disciplines benefit from these data, enabling improvements in applied models, providing new insights into Earth system processes (e.g., monitoring the global water cycle, ice sheet and glacier melting or sea-level rise) or establishing new operational services. Long time series of mass transport data are needed to disentangle anthropogenic and natural sources of climate change impacts on the Earth system. In order to secure sustained observations on a long-term basis, space agencies and the Earth science community are currently planning future satellite gravimetry mission concepts to enable higher accuracy and better spatial and temporal resolution. This Special Issue provides examples of recent improvements in gravity observation techniques and data processing and analysis, applications in the fields of hydrology, glaciology and solid Earth based on satellite gravimetry data, as well as concepts of future satellite constellations for monitoring mass transport in the Earth system
Geodetic Sciences
Space geodetic techniques, e.g., global navigation satellite systems (GNSS), Very Long Baseline Interferometry (VLBI), satellite gravimetry and altimetry, and GNSS Reflectometry & Radio Occultation, are capable of measuring small changes of the Earth�s shape, rotation, and gravity field, as well as mass changes in the Earth system with an unprecedented accuracy. This book is devoted to presenting recent results and development in space geodetic techniques and sciences, including GNSS, VLBI, gravimetry, geoid, geodetic atmosphere, geodetic geophysics and geodetic mass transport associated with the ocean, hydrology, cryosphere and solid-Earth. This book provides a good reference for geodetic techniques, engineers, scientists as well as user community
Determination of crustal motions using satellite laser ranging
Satellite laser ranging has matured over the last decade into one of the essential space geodesy techniques. It has demonstrated centimeter site positioning and millimeter per year velocity determinations in a frame tied dynamically to the mass center of the solid Earth hydrosphere atmosphere system. Such a coordinate system is a requirement for studying long term eustatic sea level rise and other global change phenomena. Earth orientation parameters determined with the coordinate system have been produced in near real time operationally since 1983, at a relatively modest cost. The SLR ranging to Lageos has also provided a rich spectrum of results based upon the analysis of Lageos orbital dynamics. These include significant improvements in the knowledge of the mean and variable components of the Earth's gravity field and the Earth's gravitational parameter. The ability to measure the time variations of the Earth's gravity field has opened as exciting area of study in relating global processes, including meteorologically derived mass transport through changes in the satellite dynamics. New confirmation of general relativity was obtained using the Lageos SLR data
Editorial : Volumes, timescales, and frequency of magmatic processes in the Earth's lithosphere
Heat, mass, and fluid transfer processes related to the formation and growth of the continental crust along convergent and divergent plate boundaries, and the formation, modification, and recycling of the continental crust are key research themes in the solid Earth Science community. Establishing the link between magma generation, transport, emplacement, and eruption can therefore significantly improve our understanding of crust-forming processes associated with plate tectonics, and, particularly, help determining the architecture, and composition of the Earth's lithosphere
Linking the evolution of terrestrial interiors and an early outgassed atmosphere to astrophysical observations
A terrestrial planet is molten during formation and may remain so if subject
to intense insolation or tidal forces. Observations continue to favour the
detection and characterisation of hot planets, potentially with large outgassed
atmospheres. We aim to determine the radius of hot Earth-like planets with
large outgassed atmospheres and explore differences between molten and solid
silicate planets and their influence on the mass-radius relationship and
transmission and emission spectra. An interior-atmosphere model, combined with
static structure calculations, tracks the evolving radius of a rocky mantle
that is outgassing CO and HO. Synthetic emission and transmission
spectra are generated for CO and HO dominated atmospheres. Atmospheres
dominated by CO suppress the outgassing of HO to a greater extent than
previously realised, as previous studies have applied an erroneous relationship
between volatile mass and partial pressure. We therefore predict more HO
can be retained by the interior during the later stages of magma ocean
crystallisation. Furthermore, formation of a lid at the surface can tie
outgassing of HO to the efficiency of heat transport through the lid,
rather than the atmosphere's radiative timescale. Contraction of the mantle as
it solidifies gives radius decrease, which can partly be offset by
addition of a relatively light species to the atmosphere. We conclude that a
molten silicate mantle can increase the radius of a terrestrial planet by
around compared to its solid counterpart, or equivalently account for a
decrease in bulk density. An outgassing atmosphere can perturb the total
radius according to its speciation. Atmospheres of terrestrial planets around
M-stars that are dominated by CO or HO can be distinguished by
observing facilities with extended wavelength coverage (e.g., JWST).Comment: 19 pages, published in A&A, abstract shortene
Atmospheric gravitational tides of Earth-like planets orbiting low-mass stars
Temperate terrestrial planets orbiting low-mass stars are subject to strong
tidal forces. The effects of gravitational tides on the solid planet and that
of atmospheric thermal tides have been studied, but the direct impact of
gravitational tides on the atmosphere itself has so far been ignored. We first
develop a simplified analytic theory of tides acting on the atmosphere of a
planet. We then implement gravitational tides into a general circulation model
of a static-ocean planet in a short-period orbit around a low-mass star -- the
results agree with our analytic theory. Because atmospheric tides and
solid-body tides share a scaling with the semi-major axis, we show that there
is a maximum amplitude of the atmospheric tide that a terrestrial planet can
experience while still having a solid surface; Proxima Centauri b is the poster
child for a planet that could be geophysically Earth-like but with atmospheric
tides more than 500 stronger than Earth's. In this most extreme
scenario, we show that atmospheric tides significantly impact the planet's
meteorology -- but not its climate. Two possible modest climate impacts are
enhanced longitudinal heat transport and cooling of the lowest atmospheric
layers. The strong radiative forcing of such planets dominates over
gravitational tides, unlike moons of cold giant planets, such as Titan. We
speculate that atmospheric tides could be climatologically important on planets
where the altitude of maximal tidal forcing coincides with the altitude of
cloud formation and that the effect could be detectable for non-Earth-like
planets subject to even greater tides
A continuum model of multi-phase reactive transport in igneous systems
Multi-phase reactive transport processes are ubiquitous in igneous systems. A
challenging aspect of modelling igneous phenomena is that they range from
solid-dominated porous to liquid-dominated suspension flows and therefore
entail a wide spectrum of rheological conditions, flow speeds, and length
scales. Most previous models have been restricted to the two-phase limits of
porous melt transport in deforming, partially molten rock and crystal settling
in convecting magma bodies. The goal of this paper is to develop a framework
that can capture igneous system from source to surface at all phase proportions
including not only rock and melt but also an exsolved volatile phase. Here, we
derive an n-phase reactive transport model building on the concepts of Mixture
Theory, along with principles of Rational Thermodynamics and procedures of
Non-equilibrium Thermodynamics. Our model operates at the macroscopic system
scale and requires constitutive relations for fluxes within and transfers
between phases, which are the processes that together give rise to reactive
transport phenomena. We introduce a phase- and process-wise symmetrical
formulation for fluxes and transfers of entropy, mass, momentum, and volume,
and propose phenomenological coefficient closures that determine how fluxes and
transfers respond to mechanical and thermodynamic forces. Finally, we
demonstrate that the known limits of two-phase porous and suspension flow
emerge as special cases of our general model and discuss some ramifications for
modelling pertinent two- and three-phase flow problems in igneous systems.Comment: Revised preprint submitted for peer-reviewed publication: main text
with 8 figures, 1 table; appendix with 3 figures and 2 table
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