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Evaluation of the Heat,Entropy,and Rotational Changes Produced by Gravitational Segregation during Core Formation

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Journal of earth Science 2015年第1期26卷 124-133页

作者： Anne M.Hofmeister Robert E.Criss department of earth and planetary sciences Washington University

Core formation by gravitational segregation allegedly released sufficient interior heat to melt the earth. Analysis of the energetics, which compare gravitational potential energy （Ug） of a fictitious, homogeneous reference state to earth＇s current layered configuration, needs updating to correct errors and omissions, and to accommodate recent findings：（1） An erroneous positive sign was used for Ug while maintaining the reference value of 0 at infinity, which results in an incorrect sign fur AUg, which is crucial in determining whether a process is endothermic or exothermic. （2） The value of Ug for earth＇s initial state is uncertain. （3） Recent meteorite evidence indicates that core formation began before the earth was full-sized, which severely limits AUg. （4） Inhomogeneous accretion additionally reduced AUg. （5） The potentially large effect of differential rotation between the core and the mantle was not accounted for. （6） Entropy changes associated with creating order were neglected. Accordingly, we revise values of Ug, evaluate uncertainties, and show that AUg was converted substantially to eonfigurational energy （TAS）. These considerations limit the large sources of primordial heat to impacts and radioactivity. Although these processes may play a role in core formation, their energies are independent of gravitational segregation, which produces order and rotational energy, not internal heat. Instead, gravitational segregation promotes planetary cooling mainly because it segregates lithophilic radioactive elements upward, increasing surface heat flux while shortening the distance over which radiogenic heat diffuses outwards.

关键词： core formation primordial heat configurational energy thermodynamics rotational energy.

Climate change response to astronomical forcing during the Oligocene-Miocene transition in the equatorial Atlantic(ODP Site 926)

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Science China earth sciences 2016年第8期59卷 1665-1673页

作者： ZOU ZhuoYan HUANG ChunJu LI MingSong ZHANG Yang State Key Laboratory of Biogeology and Environmental Geology School of Earth Sciences China University of Geosciences department of earth and planetary sciences Johns Hopkins University department of earth Atmospheric and Planetary Sciences Purdue University

The Oligocene-Miocene transition period was characterized by a decrease in global CO2 levels, expansion of polar ice sheet, fall in global sea-level, etc. However, the reasons for, and mechanisms of, this global, extreme-cold climate change event（Mi-1） still remain controversial. Our samples from the core of the Ocean Drilling Program（ODP） Leg 154, Site 926, located in the equatorial Atlantic, mainly consist of light-gray, nannofossil chalk with foraminifers interbedded with greenish-gray, clayey, nannofossil chalk sediments. Color variation from light-gray layers（up to 80% carbonate content） to dark layers（60% carbonate content） was observed to occur cyclically at the meter scale. Therefore, we chose color reflectance lightness（L*） data as the paleoclimate proxy on which to perform cyclostratigraphic analysis because it could reflect carbonate content changes. Based on the recognition of the 405 kyr long eccentricity and 40 kyr obliquity cycles of the L* series, we tuned the series to establish an absolute astronomical time scale using the published age of the Oligocene-Miocene boundary（OMB） as the anchor for an absolute age control point. The power spectra of the tuned L* series showed that the long eccentricity signals became significantly weak, while the obliquity signals became strong, from the Late Oligocene to the Early Miocene. The 405 kyr long eccentricity minimum coincided with the 1.2 Myr obliquity node at the OMB, and similar convergences might be closely related to other extreme-cold events in earth’s history. In addition, the sedimentation accumulation rate, oxygen isotopes of benthonic foraminifers, and rodents’ per-taxon turnover rate from Central Spain showed the same 2 Myr cyclicity, which indicates the significant influence of earth-orbital forcing on the earth system and ecological evolution on the million-year time scale.

关键词： Late Oligocene-Early Miocene ODP Site 926 Lightness Astronomical time scale Astronomical forcing

Calcium isotope compositions as a means to trace carbonate recycling

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National Science Review 2022年第6期9卷 8-10页

作者： Shichun Huang Stein B.Jacobsen department of Geoscience University of Nevada department of earth and planetary sciences Harvard University

Marine carbonates, such as sedimentary carbonates and secondary carbonates formed during marine alteration processes, are returned to the mantle at subduction zones, and their fates regulate the global carbon cycle. S... 详细信息

关键词： Carbonates

Equatorial aurora: the aurora-like airglow in the negative magnetic anomaly

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National Science Review 2020年第10期7卷 1606-1615页

作者： Fei He Yong Wei Weixing Wan Key Laboratory of earth and planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences College of earth and planetary sciences University of Chinese Academy of Sciences

The most fantastic optical phenomena in the earth’s upper atmosphere are the auroras. They are highly informative indicators of solar activity, geomagnetic activity, upper atmospheric structures and dynamics,and magnetospheric energetic particles. An area where the geomagnetic field differs significantly from the expected symmetric dipole, such as at the South Atlantic Anomaly, where the magnetic field intensity is low,gives rise to stronger precipitation of energetic particles into the upper atmosphere. Impact excitation and the subsequent airglow emissions exhibit aurora-like dynamic signatures. Nomenclatures of nonpolar aurora or equatorial auroras are similar to those used with the polar auroras owing to their similar excitation mechanisms. This paper provides an overview of the knowledge and the challenges concerning auroral activity at the South Atlantic Anomaly, or more generally, at the negative magnetic anomaly. We emphasize systematic investigation of the equatorial auroras to reveal the temporal and spatial evolution of the magnetic anomaly and the behaviour of energetic particles in near-earth space.

关键词： aurora geomagnetic field South Atlantic Anomaly negative magnetic anomaly energetic particles

Statistics of Evolving Populations and Their Relevance to Flood Risk

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Journal of earth Science 2016年第1期27卷 2-8页

作者： Robert E.Criss department of earth and planetary sciences Washington University in St.Louis

Statistical methods are commonly used to evaluate natural populations and environmental variables, yet these must recognize temporal trends in population character to be appropriate in an evolving world. New equations presented here define the statistical measures of aggregate historical populations affected by linear changes in population means and standard deviations. These can be used to extract the statistical character of present-day populations, needed to define modern variability and risk, from tables of historical data that are dominated by measurements made when conditions were different. As an example, many factors such as climate change and in-channel structures are causing flood levels to rise, so realistic estimation of future flood levels must take such secular changes into account. The new equations provide estimates of water levels for ＂100-year＂ floods in the USA Midwest that are 0.5 to 2 m higher than official calculations that routinely assume population stationarity. These equations also show that flood levels will continue to rise by several centimeters per year. This rate is nearly ten times faster than the rise of sea level, and thus represents one of the fastest and most damaging rates of change that is documented by robust data.

关键词： flood risk statistical theory Mississippi River.

High-resolution model experiments unveil the crucial role of small-scale air-sea interactions in large-scale oceanic water mass formation

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National Science Review 2023年第9期10卷 120-121页

作者： Shoshiro Minobe department of earth and planetary sciences Faculty of Science Hokkaido University

Subtropical mode water (STMW) plays a crucial role in the earth’s climate,including the oceans’ absorption of anthropogenic CO2and heat produced by global warming,thus slowing the progression of global ***,accurate prediction of STMW is important for future climate change ***,there has been a problem with the climate models that have been used for climate projections in that they have not been able to adequately reproduce STMW.

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Dependence of Mean and Peak Streamflow on Basin Area in the Conterminous United States

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Journal of earth Science 2016年第1期27卷 83-88页

作者： William E.Winston Robert E.Criss department of earth and planetary sciences Washington University in St.Louis

Basin area is the primary control on both mean and peak streamflows, but relationships vary with regional meteorological conditions. Rich historical data sets permit deduction of these relationships for most areas of the United States, revealing both expected and unexpected correlations. On log-log plots, mean flows for most basins with 〉75 cm/y rainfall have unit slopes, with the y-intercept approximating the mean annual runoff. Lower slopes characterize regions where runoff is greatest at high topographic elevations, or where significant withdrawals for irrigation occur at lower elevations. Peak flows also correlate strongly with basin area, but the regressions for most regions have slopes ranging from 0.4 to 0.9, and y-intercepts that increase with increasing flood recurrence interval. The slopes on these log-log plots for peak flows are highest in cool regions with low sunshine and low evapotranspiration, and lowest where sunshine is abundant, evapotranspiration is high, and small convective storm cells are common. Effects of relief are small and inconsistent. Peak flows of small watersheds are huge compared to their mean flows, commonly being several thousand times greater, particularly in the USA midcontinent where the slopes for peak flows are low.

关键词： floods GIS runoff rivers.

Water and other volatiles on Mars

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National Science Review 2024年第6期11卷 12-14页

作者： Sen Hu Yubing Gao Zhan Zhou Liang Gao Yangting Lin Key Laboratory of the earth and planetary Physics Institute of Geology and GeophysicsChinese Academy of Sciences College of earth and planetary sciences University of Chinese Academy of Sciences

Mars, the intriguing red planet, is one of the planets most similar to the earth in our solar system. It is widely accepted that Mars could have had a warm and wet climate in its early history supported by numerous lines of evidence, e.g. topography, canyons, outflow channels, presence of phyllosilicates and evaporative salts,sedimentary formation, and many others (e.g.[1]), and thus Mars is believed to once have a potentially habitable environment which could be able to supply fundamental conditions for the evolution of potential lives.

关键词： mars water other volatiles

The thermal conductivity of the earth's core and implications for its thermal and compositional evolution

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National Science Review 2021年第4期8卷 18-20页

作者： Kenji Ohta Kei Hirose department of earth and planetary sciences Tokyo Institute of Technology earth-Life Science Institute Tokyo Institute of Technology department of earth and planetary Science The University of Tokyo

The thermal conductivity of iron alloys is a key to understanding the mechanism of convection in the earth’s liquid core and its thermal history. The earth’s magnetic field is formed by a dynamo action that requires...

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