Mapping Earth Analogs from Photometric Variability: Spin-Orbit Tomography for Planets in Inclined Orbits

Aiming at obtaining detailed information of surface environment of Earth analogs, Kawahara & Fujii (2011) proposed an inversion technique of annual scattered light curves named the spin-orbit tomography (SOT), which enables one to sketch a two-dimensional albedo map from annual variation of the disk-integrated scattered light, and demonstrated the method with a planet in a face-on orbit. We extend it to be applicable to general geometric configurations, including low-obliquity planets like the Earth in inclined orbits. We simulate light curves of the Earth in an inclined orbit in three photometric bands (0.4-0.5um, 0.6-0.7um, and 0.8-0.9um) and show that the distribution of clouds, snow, and continents is retrieved with the aid of the SOT. We also demonstrate the SOT by applying it to an upright Earth, a tidally locked Earth, and Earth analogs with ancient continental configurations. The inversion is model independent in the sense that we do not assume specific albedo models when mapping the surface, and hence applicable in principle to any kind of inhomogeneity. This method can potentially serve as a unique tool to investigate the exohabitats/exoclimes of Earth analogs.Comment: 15 pages, 14 figures, 2 tables; published in The Astrophysical Journa

Environmentally driven extinction and opportunistic origination explain fern diversification patterns.

Combining palaeontological and neontological data offers a unique opportunity to investigate the relative roles of biotic and abiotic controls of species diversification, and the importance of origination versus extinction in driving evolutionary dynamics. Ferns comprise a major terrestrial plant radiation with an extensive evolutionary history providing a wealth of modern and fossil data for modelling environmental drivers of diversification. Here we develop a novel Bayesian model to simultaneously estimate correlations between diversification dynamics and multiple environmental trajectories. We estimate the impact of different factors on fern diversification over the past 400 million years by analysing a comprehensive dataset of fossil occurrences and complement these findings by analysing a large molecular phylogeny. We show that origination and extinction rates are governed by fundamentally different processes: originations depend on within-group diversity but are largely unaffected by environmental changes, whereas extinctions are strongly affected by external factors such as climate and geology. Our results indicate that the prime driver of fern diversity dynamics is environmentally driven extinction, with origination being an opportunistic response to diminishing ecospace occupancy

Elevated CO2 degassing rates prevented the return of Snowball Earth during the Phanerozoic

The Cryogenian period (~720–635 Ma) is marked by extensive Snowball Earth glaciations. These have previously been linked to CO₂ draw-down, but the severe cold climates of the Cryogenian have never been replicated during the Phanerozoic despite similar, and sometimes more dramatic changes to carbon sinks. Here we quantify the total CO₂ input rate, both by measuring the global length of subduction zones in plate tectonic reconstructions, and by sea-level inversion. Our results indicate that degassing rates were anomalously low during the Late Neoproterozoic, roughly doubled by the Early Phanerozoic, and remained comparatively high until the Cenozoic. Our carbon cycle modelling identifies the Cryogenian as a unique period during which low surface temperature was more easily achieved, and shows that the shift towards greater CO₂ input rates after the Cryogenian helped prevent severe glaciation during the Phanerozoic. Such a shift appears essential for the development of complex animal life

Climate model boundary conditions for four Cretaceous time slices

International audienceGeneral circulation models (GCMs) are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution) for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma). These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude × longitude) paleo Digital Elevation Models (paleoDEMs) of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University) and published literature and were then modified for use in GCMs. The paleovegetation distribution is based on published data and reconstructions and consultation with members of the paleobotanical community and is represented as generalized biomes that should be easily translatable to many vegetation-modeling schemes

Professional learning communities for early childhood teachers

This study describes research related to professional development, mainly professional learning communities. The author created two professional learning communities within a child care facility in Queens, New York. This study implies that professional learning communities can be beneficial to early childhood teachers

A Diatom Phosphorus Inference Model for 30 Freshwater Lakes in NE Ohio and NW Pennsylvania

Nutrient enrichment in the form of anthropogenic phosphorous and nitrogen inputs has occurred in lakes worldwide. In the absence of historical water chemistry data, the extent to which this disturbance has impacted lakes in the Erie/Ontario drift and lake plain and Western Allegheny Plateau ecoregions remains to be determined. The objective of this study was to develop a diatom calibration set through analysis of surface sediments and water chemistry from 30 lakes spanning a phosphorous and nitrogen gradient in the glaciated regions of northeast Ohio and northwest Pennsylvania with an additional lake in New York. No current training set exists for this unique geographic region. The relationship between diatom species and environmental variables was established using ordination techniques involving multiple regression and weighted-averaging methods. Canonical correspondence analysis (CCA) was used to determine environmental variables that have a strong influence on diatoms from the ecoregions studied. Total phosphorus, ammonia, and magnesium were the three most statistically significant variables determined through multivariate analyses, although maximum depth and nickel concentrations were also found to be important. At a total phosphorus inference model was developed from recent diatom fossil remains and contemporary water chemistry measurements. The ecological indicator values (optima and tolerances) of 40 abundant diatom species were defined using C2 computer software. The root mean squared error associated with prediction of the TP inference model was 17 ug/L, and the R2 linear coefficient of correlation between observed and diatom-inferred TP values was 0.77. The optima developed in this research match closely those constructed from calibration studies covering similar or longer TP gradients (12 ug/L-153 ug/L TP). A comparison with optima developed from other studies yields values much lower than those in this project and illustrates the need for regional calibration studies. This calibration set will be u

The fate of the homoctenids (Tentaculitoidea) during the Frasnian-Famennian mass extinction (Late Devonian)

The homoctenids (Tentaculitoidea) are small, conical-shelled marine animals which are amongst the most abundant and widespread of all Late Devonian fossils. They were a principal casualty of the Frasnian-Famennian (F-F, Late Devonian) mass extinction, and thus provide an insight into the extinction dynamics. Despite their abundance during the Late Devonian, they have been largely neglected by extinction studies. A number of Frasnian-Famennian boundary sections have been studied, in Poland, Germany, France, and the United States. These sections have yielded homoctenids, which allow precise recognition of the timing of the mass extinction. It is clear that the homoctenids almost disappear from the fossil record during the latest Frasnian “Upper Kellwasser Event”. The coincident extinction of this pelagic group, and the widespread development of intense marine anoxia within the water column, provides a causal link between anoxia and the F-F extinction. Most notable is the sudden demise of a group, which had been present in rock-forming densities, during this anoxic event. One new species, belonging to Homoctenus is described, but is not formally named here

A Diatom Phosphorus Inference Model for 30 Freshwater Lakes in NE Ohio and NW Pennsylvania

Nutrient enrichment in the form of anthropogenic phosphorous and nitrogen inputs has occurred in lakes worldwide. In the absence of historical water chemistry data, the extent to which this disturbance has impacted lakes in the Erie/Ontario drift and lake plain and Western Allegheny Plateau ecoregions remains to be determined. The objective of this study was to develop a diatom calibration set through analysis of surface sediments and water chemistry from 30 lakes spanning a phosphorous and nitrogen gradient in the glaciated regions of northeast Ohio and northwest Pennsylvania with an additional lake in New York. No current training set exists for this unique geographic region. The relationship between diatom species and environmental variables was established using ordination techniques involving multiple regression and weighted-averaging methods. Canonical correspondence analysis (CCA) was used to determine environmental variables that have a strong influence on diatoms from the ecoregions studied. Total phosphorus, ammonia, and magnesium were the three most statistically significant variables determined through multivariate analyses, although maximum depth and nickel concentrations were also found to be important. At a total phosphorus inference model was developed from recent diatom fossil remains and contemporary water chemistry measurements. The ecological indicator values (optima and tolerances) of 40 abundant diatom species were defined using C2 computer software. The root mean squared error associated with prediction of the TP inference model was 17 ug/L, and the R2 linear coefficient of correlation between observed and diatom-inferred TP values was 0.77. The optima developed in this research match closely those constructed from calibration studies covering similar or longer TP gradients (12 ug/L-153 ug/L TP). A comparison with optima developed from other studies yields values much lower than those in this project and illustrates the need for regional calibration studies. This calibration set will be u

Wage inequality, tasks and occupations

This paper assesses the relationship between occupation attributes and changes in wage inequality finding partial support for the computerization hypothesis. While wages associated with non-routine cognitive tasks have risen; current versions of the hypothesis cannot explain the pattern of within occupation wage changes, the differential impact of various types of non-routine cognitive tasks and the declining return to tasks that complement machines. Despite significant employment shifts, occupational composition alone matters little for changes in wage inequality. Changes in wage dispersion within occupations are quantitatively just as important as wage changes between occupations for explaining wage inequality between 1980 and 2000.wage inequality, computerization, skill, tasks

The Location and Styles of Ice-Free “Oases” during Neoproterozoic Glaciations with Evolutionary Implications

Evidence based on molecular clocks, together with molecular evidence/biomarkers and putative body fossils, points to major evolutionary events prior to and during the intense Cryogenian and Ediacaran glaciations. The glaciations themselves were of global extent. Sedimentological evidence, including hummocky cross-stratification (representing ice-free seas affected by intra-glacial storms), dropstone textures, microbial mat-bearing ironstones, ladderback ripples, and wave ripples, militates against a “hard” Snowball Earth event. Each piece of sedimentological evidence potentially allows insight into the shape and location, with respect to the shoreline, of ice-free areas (“oases”) that may be viewed as potential refugia. The location of such oases must be seen in the context of global paleogeography, and it is emphasized that continental reconstructions at 600 Ma (about 35 millions years after the “Marinoan” ice age) are non-unique solutions. Specifically, whether continents such as greater India, Australia/East Antarctica, Kalahari, South and North China, and Siberia, were welded to a southern supercontinent or not, has implications for island speciation, faunal exchange, and the development of endemism