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Sample records for early terrestrial atmosphere

  1. The persistent and pernicious myth of the early CO2-N2 atmospheres of terrestrial planets

    NASA Astrophysics Data System (ADS)

    Shaw, G. H.

    2009-12-01

    The accepted model for early atmospheres of terrestrial planets has settled on a CO2-N2 composition. Unfortunately, while it is largely based on a brilliant geological analysis by Rubey, there is no compelling evidence whatsoever for such a composition as the first “permanent” atmosphere for Earth or any other planet. In fact, geological discoveries of the past 50+ years reveal several problems with a CO2-N2 atmosphere, some of which Rubey recognized in his own analysis. He clearly addressed the problem of timing of degassing, concluding that early massive degassing of CO2 would produce readily observed and profound effects, which are not evident. Modeling and constraints on the timing of planetary accretion and core formation indicate massive early degassing. If early degassing emitted CO2-N2, the effects are concealed. Plate tectonic recycling is not a solution, as conditions would have persisted beyond the time of the earliest rocks, which do not show the effects. Attempts to return degassed CO2 to the mantle are not only ad hoc, but inconsistent with early thermal structure of the Earth. Second, production of prebiotic organic compounds from a CO2-N2 atmosphere has been a nagging problem. At best this has been addressed by invoking hydrogen production from the mantle to provide reducing capacity. While hydrogen may be emitted in volcanic eruptions, it is exceedingly difficult to imagine this process generating enough organics to yield high concentrations in a global ocean. The recent fashion of invoking organic synthesis at deep-sea vents suffers from the same problem: how to achieve sufficient concentrations of organics in a global ocean by abiotic synthesis when hydrothermal activity stirs the solution and carries the prebiotic products off to great dilution? Suggesting life began at deep-sea vents, and continues to carry on chemosynthesis there, begs the question. Unless you get high enough concentrations of prebiotics by abiotic processes, you simply don’t get life. Third, solutions invoking high atmospheric CO2 as the answer to the faint young sun problem encounter exactly the same problems associated with prompt degassing of CO2. Fourth, the carbon isotope record, in which early carbonaceous deposits show signs of photosynthetic fractionation of carbon are problematical if most of the primary surface and near-surface carbon was CO2. Finally, the delay in oxidation of Earth’s surface following oxygenic photosynthesis is problematical if early photosynthesizers had a vast CO2 source from early degassing. Given an abundant food supply, what prevented early cyanobacteria from rapidly oxidizing the surface? Although discovery of CO2-rich atmospheres on Venus and Mars seem to support CO2 as the primary surface carbon reservoir, these atmospheres are the result of atmospheric evolution, particularly loss of H to space. ALL of these problems disappear with early degassing of reduced gases such as CH4 and NH3. Considerations of meteoritic compositions, accretionary processes, and early atmosphere/hydrosphere chemical processing all support reduced gases as dominant in the early atmospheres of the terrestrial planets. The time has come to revert to any earlier idea of strongly reducing conditions on early terrestrial planet surfaces, followed by long-term evolutionary trends toward oxidation.

  2. Atmospheric oxygen levels affect mudskipper terrestrial performance: implications for early tetrapods.

    PubMed

    Jew, Corey J; Wegner, Nicholas C; Yanagitsuru, Yuzo; Tresguerres, Martin; Graham, Jeffrey B

    2013-08-01

    The Japanese mudskipper (Periophthalmus modestus), an amphibious fish that possesses many respiratory and locomotive specializations for sojourns onto land, was used as a model to study how changing atmospheric oxygen concentrations during the middle and late Paleozoic Era (400-250 million years ago) may have influenced the emergence and subsequent radiation of the first tetrapods. The effects of different atmospheric oxygen concentrations (hyperoxia = 35%, normoxia = 21%, and hypoxia = 7% O2) on terrestrial performance were tested during exercise on a terrestrial treadmill and during recovery from exhaustive exercise. Endurance and elevated post-exercise oxygen consumption (EPOC; the immediate O2 debt repaid post-exercise) correlated with atmospheric oxygen concentration indicating that when additional oxygen is available P. modestus can increase oxygen utilization both during and following exercise. The time required post-exercise for mudskippers to return to a resting metabolic rate did not differ between treatments. However, in normoxia, oxygen consumption increased above hyperoxic values 13-20 h post-exercise suggesting a delayed repayment of the incurred oxygen debt. Finally, following exercise, ventilatory movements associated with buccopharyngeal aerial respiration returned to their rest-like pattern more quickly at higher concentrations of oxygen. Taken together, the results of this study show that P. modestus can exercise longer and recover quicker under higher oxygen concentrations. Similarities between P. modestus and early tetrapods suggest that increasing atmospheric oxygen levels during the middle and late Paleozoic allowed for elevated aerobic capacity and improved terrestrial performance, and likely led to an accelerated diversification and expansion of vertebrate life into the terrestrial biosphere. PMID:23620255

  3. On the relationship between early solar activity and the evolution of terrestrial planet atmospheres

    NASA Technical Reports Server (NTRS)

    Repin, Robert O.

    1989-01-01

    Mass fractionation during hydrodynamic escape of hydrogen-rich primordial atmospheres form Venus, earth, and Mars can account for most of the salient features of mass distributions in their present-day atmospheres. The principal assumptions and results of an escape-fractionation model for the evolution of terrestrial planet atmospheres from primary to final states are qualitatively described, with emphasis on the astrophysical conditions needed to enable the loss process. A substantial and rapidly declining flux of energetic solar radiation into atmospheric exospheres is required, initially (at solar ages of about 1-10 million years) two to three orders of magnitude more intense than that supplied by extreme-ultraviolet emission from the contemporary sun. The solar accretion disk must have dissipated if such radiation is to penetrate the system midplane to planetray distances. On both criteria, hydrodynamic escape from planets appears plausible in the astrophysical environment of the naked T-Tauri stars.

  4. The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

    2015-01-01

    We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

  5. Photochemistry of Terrestrial Exoplanet Atmospheres

    NASA Astrophysics Data System (ADS)

    Hu, Renyu; Seager, S.

    2013-01-01

    Terrestrial exoplanet atmospheres require photochemistry for their study. This is because the steady state composition depends critically on the component gas sources (surface emission) and sinks (chemical reactions initiated by UV photolysis). For my Ph.D. research I have developed a comprehensive photochemistry model for terrestrial exoplanet atmospheres from the ground up, which includes 111 molecules and aerosols made of C, H, O, N, S elements, and more than 800 chemical reactions linking them. With updated numerical algorithms, the photochemistry model has desirable features for exoplanet exploration, notably the capacity of treating both reduced and oxidized atmospheres, the elimination of the need of fine-tuned initial conditions, and the flexibility of choosing a subset of chemical species and chemical reactions for the computation. Using the photochemistry model, I provided benchmark atmospheric composition models for reducing, weakly oxidizing, and highly oxidizing atmospheres on terrestrial exoplanets; I systemized the short-lived nature of sulfur gases on virtually all types of terrestrial exoplanet atmospheres; I revisited O2 as the remote-sensing probe of biotic photosynthesis and found a potential false positive in high CO2 atmospheres without surface emission of reducing gases (e.g., H2 and CH4); and I provided atmosphere models to propose NH3 as a new biosignature gas in hydrogen-rich atmospheres. I have also extended the photochemistry model to the regime of thick atmospheres (at depths of which thermochemical equilibrium can be effectively achieved), and summarized a zoo of super-Earths including water planets, hydrocarbon planets, and even oxygen planets depending on the C-H-O elemental abundances of their atmospheres.

  6. Synthetic spectra of simulated terrestrial atmospheres containing possible biomarker gases.

    PubMed

    Schindler, T L; Kasting, J F

    2000-05-01

    NASA's proposed Terrestrial Planet Finder, a space-based interferometer, will eventually allow spectroscopic analyses of the atmospheres of extrasolar planets. Such analyses would provide information about the existence of life on these planets. One strategy in the search for life is to look for evidence of O3 (and hence O2) in a planet's atmosphere; another is to look for gases that might be present in an atmosphere analogous to that of the inhabited early Earth. In order to investigate these possibilities, we have calculated synthetic spectra for several hypothetical terrestrial-type atmospheres. The model atmospheres represent four different scenarios. The first two, representing inhabited terrestrial planets, are an Earth-like atmosphere containing variable amounts of oxygen and an early Earth-type atmosphere containing methane. In addition, two cases representing Mars-like and early Venus-like atmospheres were evaluated, to provide possible "false positive" spectra. The calculated spectra suggest that ozone could be detected by an instrument like Terrestrial Planet Finder if the O2 concentration in the planet's atmosphere is > or = 200 ppm, or 10(-3) times the present atmospheric level. Methane should be observable on an early-Earth type planet if it is present in concentrations of 100 ppm or more. Methane has both biogenic and abiogenic sources, but concentrations exceeding 1000 ppm, or 0.1% by volume, would be difficult to produce from abiogenic sources alone. High methane concentrations in a planet's atmosphere are therefore another potential indicator for extraterrestrial life. PMID:11543302

  7. Impact erosion of terrestrial planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Ahrens, Thomas J.

    1992-01-01

    I review current ideas about the nature of the planetesimals - composition, size distribution, and the planetary encounter velocity. Previous papers on accretion and erosion of planetary atmospheres as a result of multiple impacts are reviewed. Finally, the effects of blowing off a substantial fraction of the atmosphere from a terrestrial planet due to a single giant body impact are discussed.

  8. Early Formation of Terrestrial Crust

    NASA Astrophysics Data System (ADS)

    Harrison, T. M.; Schmitt, A. K.; McCulloch, M. T.; Lovera, O. M.

    2007-12-01

    Early (≥4.5 Ga) Formation of Terrestrial Crust T.M. Harrison1, A.K. Schmitt1, M.T. McCulloch2, and O.M. Lovera1 1Department of Earth and Space Sciences and IGPP, UCLA, Los Angeles, CA 90095, USA; 2Research School of Earth Sciences, Australian National University, Canberra, A.C.T. 2601 AUSTRALIA Large deviations in ǎrepsilonHf(T) from bulk silicate Earth seen in >4 Ga detrital zircons from Jack Hills, Western Australia, have been interpreted as reflecting a major differentiation of the silicate Earth at ca. 4.4 to 4.5 Ga. We have expanded the characterization of 176Hf/177Hf (Hf) in Hadean zircons by acquiring a further 116 laser ablation Lu-Hf measurements on 87 grains with ion microprobe 207Pb/206Pb ages up to 4.36 Ga. Most measurements employed concurrent Lu-Hf and 207Pb/206Pb analyses, permitting assessment of the use of ion microprobe data to characterize the age of the volumetrically larger domain sampled by laser drilling. Our new results confirm and extend the earlier observation of significant negative deviations in ǎrepsilonHf(T) throughout the Hadean, although no positive ǎrepsilonHf(T) values were documented in this study. These data yields an essentially uniform spectrum of single-stage model ages between 4.54 and 4.20 Ga for extraction of the zircons' protoliths from a chondritic reservoir. We derived the full error propagation expression for a parameter, ǎrepsilono, which measures the difference of a sample from solar system initial (Hf) (Hfo), and from this conclude that data plotting close to (Hfo), are statistically meaningful and consistent with silicate differentiation at 4.540±0.006 Ga. δ18O and Ti thermometry for these Hadean zircons show little obvious correlation with initial (Hf), consistent with their derivation through fusion of a broad suite of crustal rock types under near water-saturated conditions. Together with the inclusion assemblage and other isotopic and trace element data obtained from these ancient zircons, our results indicate essentially continuous derivation of crust from the mantle from 4.5 to 4.2 Ga, concurrent with recycling into the mantle and internal crustal re-working. These results represent further evidence that by 4.35 Ga, portions of the crust had taken on continental characteristics.

  9. Linkages between terrestrial ecosystems and the atmosphere

    NASA Technical Reports Server (NTRS)

    Bretherton, Francis; Dickinson, Robert E.; Fung, Inez; Moore, Berrien, III; Prather, Michael; Running, Steven W.; Tiessen, Holm

    1992-01-01

    The primary research issue in understanding the role of terrestrial ecosystems in global change is analyzing the coupling between processes with vastly differing rates of change, from photosynthesis to community change. Representing this coupling in models is the central challenge to modeling the terrestrial biosphere as part of the earth system. Terrestrial ecosystems participate in climate and in the biogeochemical cycles on several temporal scales. Some of the carbon fixed by photosynthesis is incorporated into plant tissue and is delayed from returning to the atmosphere until it is oxidized by decomposition or fire. This slower (i.e., days to months) carbon loop through the terrestrial component of the carbon cycle, which is matched by cycles of nutrients required by plants and decomposers, affects the increasing trend in atmospheric CO2 concentration and imposes a seasonal cycle on that trend. Moreover, this cycle includes key controls over biogenic trace gas production. The structure of terrestrial ecosystems, which responds on even longer time scales (annual to century), is the integrated response to the biogeochemical and environmental constraints that develop over the intermediate time scale. The loop is closed back to the climate system since it is the structure of ecosystems, including species composition, that sets the terrestrial boundary condition in the climate system through modification of surface roughness, albedo, and, to a great extent, latent heat exchange. These separate temporal scales contain explicit feedback loops which may modify ecosystem dynamics and linkages between ecosystems and the atmosphere. The long-term change in climate, resulting from increased atmospheric concentrations of greenhouse gases (e.g., CO2, CH4, and nitrous oxide (N2O)) will further modify the global environment and potentially induce further ecosystem change. Modeling these interactions requires coupling successional models to biogeochemical models to physiological models that describe the exchange of water, energy, and biogenic trace gases between the vegetation and the atmosphere at fine time scales. There does not appear to be any obvious way to allow direct reciprocal coupling of atmospheric general circulation models (GCM's), which inherently run with fine time steps, to ecosystem or successional models, which have coarse temporal resolution, without the interposition of physiological canopy models. This is equally true for biogeochemical models of the exchange of carbon dioxide and trace gases. This coupling across time scales is nontrivial and sets the focus for the modeling strategy.

  10. Solar-terrestrial coupling through atmospheric electricity

    NASA Technical Reports Server (NTRS)

    Roble, R. G.; Hays, P. B.

    1979-01-01

    There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

  11. Atmospheric evolution of the terrestrial planets

    SciTech Connect

    Hunten, D.M. )

    1993-02-12

    The major atmospheric gases on Earth, Venus, and Mars were probably CO[sub 2], H[sub 2]O, and N[sub 2]. Most of the Earth's CO[sub 2] is tied up in minerals such as limestone, and Venus has lost most of its H[sub 2]O, leaving the CO[sub 2] in the atmosphere. Much of Mars' atmosphere may have been eroded in impacts by large meteoroids early in solar-system history. Noble gases are very underabundant everywhere, and must have been lost during an early period; they were probably dragged along during rapid loss of massive amounts of hydrogen. The tenuous atmospheres of Mercury and the moon have lifetimes of a few days or less and must be continuously replenished from internal or external sources.

  12. Were early pterosaurs inept terrestrial locomotors?

    PubMed Central

    2015-01-01

    Pterodactyloid pterosaurs are widely interpreted as terrestrially competent, erect-limbed quadrupeds, but the terrestrial capabilities of non-pterodactyloids are largely thought to have been poor. This is commonly justified by the absence of a non-pterodactyloid footprint record, suggestions that the expansive uropatagia common to early pterosaurs would restrict hindlimb motion in walking or running, and the presence of sprawling forelimbs in some species. Here, these arguments are re-visited and mostly found problematic. Restriction of limb mobility is not a problem faced by extant animals with extensive fight membranes, including species which routinely utilise terrestrial locomotion. The absence of non-pterodactyloid footprints is not necessarily tied to functional or biomechanical constraints. As with other fully terrestrial clades with poor ichnological records, biases in behaviour, preservation, sampling and interpretation likely contribute to the deficit of early pterosaur ichnites. Suggestions that non-pterodactyloids have slender, mechanically weak limbs are demonstrably countered by the proportionally long and robust limbs of many Triassic and Jurassic species. Novel assessments of pterosaur forelimb anatomies conflict with notions that all non-pterodactyloids were obligated to sprawling forelimb postures. Sprawling forelimbs seem appropriate for species with ventrally-restricted glenoid articulations (seemingly occurring in rhamphorhynchines and campylognathoidids). However, some early pterosaurs, such as Dimorphodon macronyx and wukongopterids, have glenoid arthrologies which are not ventrally restricted, and their distal humeri resemble those of pterodactyloids. It seems fully erect forelimb stances were possible in these pterosaurs, and may be probable given proposed correlation between pterodactyloid-like distal humeral morphology and forces incurred through erect forelimb postures. Further indications of terrestrial habits include antungual sesamoids, which occur in the manus and pes anatomy of many early pterosaur species, and only occur elsewhere in terrestrial reptiles, possibly developing through frequent interactions of large claws with firm substrates. It is argued that characteristics possibly associated with terrestriality are deeply nested within Pterosauria and not restricted to Pterodactyloidea as previously thought, and that pterodactyloid-like levels of terrestrial competency may have been possible in at least some early pterosaurs. PMID:26157605

  13. Sulfuric acid aerosols in the atmospheres of the terrestrial planets

    NASA Astrophysics Data System (ADS)

    McGouldrick, Kevin; Toon, Owen B.; Grinspoon, David H.

    2011-08-01

    Clouds and hazes composed of sulfuric acid are observed to exist or postulated to have once existed on each of the terrestrial planets with atmospheres in our solar system. Venus today maintains a global cover of clouds composed of a sulfuric acid/water solution that extends in altitude from roughly 50 km to roughly 80 km. Terrestrial polar stratospheric clouds (PSCs) form on stratospheric sulfuric acid aerosols, and both PSCs and stratospheric aerosols play a critical role in the formation of the ozone hole. Stratospheric aerosols can modify the climate when they are enhanced following volcanic eruptions, and are a current focus for geoengineering studies. Rain is made more acidic by sulfuric acid originating from sulfur dioxide generated by industry on Earth. Analysis of the sulfur content of Martian rocks has led to the hypothesis that an early Martian atmosphere, rich in SO 2 and H 2O, could support a sulfur-infused hydrological cycle. Here we consider the plausibility of frozen sulfuric acid in the upper clouds of Venus, which could lead to lightning generation, with implications for observations by the European Space Agency's Venus Express and the Japan Aerospace Exploration Agency's Venus Climate Orbiter (also known as Akatsuki). We also present simulations of a sulfur-rich early Martian atmosphere. We find that about 40 cm/yr of precipitation having a pH of about 2.0 could fall in an early Martian atmosphere, assuming a surface temperature of 273 K, and SO 2 generation rates consistent with the formation of Tharsis. This modeled acid rain is a powerful sink for SO 2, quickly removing it and preventing it from having a significant greenhouse effect.

  14. Formation and Internal Structure of Terrestrial Planets, and Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Jin, S.

    2014-11-01

    As of 2014 April 21, over 1490 confirmed exoplanets and 3705 Kepler candidates have been detected. This implies that exoplanets may be ubiquitous in the universe. In this paper, we focus on the formation, evolution, and internal structure of terrestrial planets, and the atmospheric escape of close-in planets. In chapter 2, we investigate the dynamical evolution of planetary system after the protoplanetary disk has dissipated. We find that in the final assembly stage, the occurrence of terrestrial planets is quite common and in 40% of our simulations finally at least one planet is formed in the habitable zone. We also find that if there is a highly-inclined giant planet in the system, a great many bodies will be either driven out of the system, or collide with the giant planet or the central star. This will lead to the difficulty in planetary accretion. Moreover, our results show that planetary migration can lead to the formation of close-in planets. Besides migration, close-in terrestrial planets can also be formed by a collision-merger mechanism, which means that planetary embryos can kick terrestrial planets directly into orbits that are extremely close to their parent stars. In chapter 3, we construct numerically an internal structure model for terrestrial planets, and provide three kinds of possible internal structures of Europa (Jupiter's moon) based on this model. Then, we calculate the radii of low-mass exoplanets for various mass combinations of core and mantle, and find that some of them are inconsistent with the observed radius of rocky planets. This phenomenon can be explained only if there exists a large amount of water in the core, or they own gaseous envelopes. In chapter 4, we improve our planetary evolution codes using the semi-gray model of Guillot (2010), which includes the incident flux from the host star as a heating source in planetary atmosphere. The updated codes can solve the structure of the top radiative zone of intensely irradiated planets, and thus can simulate the atmospheric escape of close-in planets driven by strong stellar X-ray or EUV emissions. We find that low-mass planets are sensitive to the atmospheric escape, and they could lose all their initial H/He envelopes during the evolution. On the other hand, gas giant can only lose a small fraction of their initial envelopes. We then carry out a parameter study of atmospheric escape at the planetary core mass, envelope mass fraction, and semi-major axis space. We find that the most intense phase of evaporation occurs within the early 100 Myr. Afterwards, atmospheric escape only has a small impact on the planetary evolution. In chapter 5, we apply our new planetary evolution model to different synthetic planet populations that are directly produced by the core-accretion paradigm (Mordasini et al. 2012a,b). We show that although the mass distribution of the planet populations is hardly affected by evaporation, the radius distribution clearly shows a break around 2 R_{⊕}. This break leads to a bimodal distribution in planet sizes (Owen & Wu 2013). Furthermore, the bimodal distribution is related to the initial characteristics of the planetary populations. We find that in two extreme cases, namely without any evaporation or with a 100% heating efficiency in the evaporation model, the final radius distributions show significant differences compared to the radius distribution of Kepler candidates. In chapter 6, we introduce a radiative transfer model that can calculate the radiation spectrum of close-in exoplanets.

  15. Synchronous negative carbon isotope shifts in marine and terrestrial biomarkers at the onset of the early Aptian oceanic anoxic event 1a: Evidence for the release of 13C-depleted carbon into the atmosphere

    NASA Astrophysics Data System (ADS)

    van Breugel, Yvonne; Schouten, Stefan; Tsikos, Harilaos; Erba, Elisabetta; Price, Gregory D.; Sinninghe Damsté, Jaap S.

    2007-03-01

    A common feature of records of the early Aptian oceanic anoxic event (OAE) 1a is the sharp negative δ13C excursion displayed in both carbonate and organic matter at the onset of this event. A synchronous negative δ13C excursion has also been noted for terrestrial organic matter. This negative excursion has been attributed to either an injection of 13C-depleted light carbon into the atmosphere or, in case of marine sediments, recycling of 13C-depleted CO2. However, most studies were done on separate cores, and no information on the relative timing of the negative spikes in terrestrial versus marine records has been obtained. Here we examine early Aptian core sections from two geographically distal sites (Italy and the mid-Pacific) to elucidate the causes and relative timing of this negative "spike." At both sites, increased organic carbon (Corg) and decreased bulk carbonate contents characterize the interval recording OAE 1a (variously referred to as the "Selli event"). The organic material within the "Selli level" is immature and of autochthonous origin. Measured δ13C values of marine and terrestrial biomarkers largely covary with those of bulk organic carbon, with lowest values recorded at the base of the organic-rich section. By contrast, sediments enveloping the "Selli level" exhibit very low Corg contents, and their extractable Corg is predominantly of allochthonous origin. Hydrous pyrolysis techniques used to obtain an autochthonous, pre-Selli δ13C value for algal-derived pristane from corresponding sample material yielded a negative δ13C shift of up to 4‰. A negative δ13C shift of similar magnitude was also measured for the terrigenous n-alkanes. The results are collectively best explained by means of a massive, syndepositional, rapid input of 13C-depleted carbon into the atmosphere and surface oceans, likely delivered either via methane produced from the dissociation of sedimentary clathrates or perhaps by widespread thermal metamorphism of Corg-rich sedimentary rocks.

  16. Atmospheric Escape from Solar System Terrestrial Planets and Exoplanets

    NASA Astrophysics Data System (ADS)

    Tian, Feng

    2015-05-01

    It has been known for decades that atmospheric escape is important for the evolution of terrestrial planets in the Solar System, although exactly how atmospheric escape changes the atmospheres of these bodies is still hotly debated. Rapidly increasing numbers of exoplanet observations provide new targets against which atmospheric escape models are tested. In this review we summarize recent studies related to atmospheric escape from exoplanets. The most important conclusions are that (a) escape can significantly influence the volatile contents of low-mass exoplanets (with mass lower than those of Uranus and Neptune) and the atmosphere and climate evolution histories of Solar System terrestrial planets; (b) models including detailed physics and chemistry in planetary upper atmospheres will be important for the interpretation of existing and future observations of exoplanets; and (c) fluid models considering 2D or 3D planetary upper atmospheres and particle models for planetary exospheres will be important not only for comparisons with observations but also for order of magnitude estimates of atmospheric escape rates. Our understanding of how escape shapes planetary atmospheres and influences the climate of low-mass planets can be expected to advance substantially in the coming decade.

  17. Terrestrial nitrous oxide cycles and atmospheric effects

    NASA Technical Reports Server (NTRS)

    Whitten, R. C.; Lawless, J. G.; Banin, A.

    1984-01-01

    The basic processes that cause N2O emission from soils are briefly discussed, and the rate of the processes is shown to vary widely in space and time, depending on soil, climate, and agrotechnical conditions. Although significant amounts of N2O are indeed emitted from the land, the complexity of the soil processes involved and the wide variation of measured rates still prevents the quantitative evaluation, global budgeting, and reliable prediction of atmospheric N2O. Increased atmospheric N2O abundance increases the levels of odd-nitrogen in the stratosphere, which, in turn, decreases the stratospheric ozone density via a catalytic cycle. Using appropriate atmospheric models and current chemical kinetic data, it has been found that the dependence of ozone reduction on N2O increase is nearly linear; a simulated doubling of N2O leads to a predicted decrease of about 14 percent in total ozone column density. A 10 percent increase in N2O yields a predicted increase in nonmelanoma skin cancer of several percent, and a possible raising of surface temperature of 0.03 K.

  18. To terrestrial planets upper atmosphere superrotation

    NASA Astrophysics Data System (ADS)

    Bespalov, Peter A.; Savina, Olga N.

    2010-05-01

    We considered the kinetics of a rarefied exosphere replenished by particles injected from a spherical surface inside which collisions are significant. As we have shown, peculiarities of the motion of a rarefied gas in the gravitational field of a slowly rotating planet, Venus, Earth and Mars, can give rise to superrotation. We have shown that one of the superrotation mechanisms for rarefied planetary atmospheres is the separation of particles: some of them fly away from the planet, while others become its satellites. Based on the proposed mechanism, we estimated the superrotation for the exospheres of Venus, Earth, and Mars. Our main results are as follows. 1) We found an exact solution of the boundary value problem for the two-dimensional collision less Boltzmann equation that includes particles with elliptical and hyperbolic orbits. 2) We obtained and analyzed the solution of the kinetic equation with weak elastic collisions. We determined the spatial distributions of the atmospheric-gas density and mean angular velocity and established the possibility of exospheric superrotation. In conclusion, it should be emphasized that the separation of particles with weak collisions is a universal, although, probably, not the only superrotation mechanism for an upper rarefied slowly rotating atmosphere.

  19. Space, Atmospheric, and Terrestrial Radiation Environments

    NASA Technical Reports Server (NTRS)

    Barth, Janet L.; Dyer, C. S.; Stassinopoulos, E. G.

    2003-01-01

    The progress on developing models of the radiation environment since the 1960s is reviewed with emphasis on models that can be applied to predicting the performance of microelectronics used in spacecraft and instruments. Space, atmospheric, and ground environments are included. It is shown that models must be adapted continually to account for increased understanding of the dynamics of the radiation environment and the changes in microelectronics technology. The IEEE Nuclear and Space Radiation Effects Conference is a vital forum to report model progress to the radiation effects research community.

  20. Aerosol charging processes in planetary and terrestrial atmospheres

    NASA Astrophysics Data System (ADS)

    Tripathi, S.; Michael, M.

    2015-10-01

    Interactions between the ions and aerosols cause charge exchange, which can lead to substantial aerosol charge and ion removal in the atmosphere. Aerosol charging plays an important role in various processes such as aerosol scavenging by droplets and aerosol growth by affecting aerosol-aerosol coagulation rates. Ions are removed in regions with abundant aerosol, which may modify charge flow in an atmosphere, such as that associated with an atmospheric electrical circuit. A review will be made of the charging processes and the consequences occurring in atmospheres of Mars, Venus and Titan and compared with terrestrial atmosphere [1], [2], [3],[4], [5]. Some recent results on charging of aerosols in the lower and upper atmosphere of Titan will be presented and consequences will be discussed.

  1. Sulphur cycling between terrestrial agroecosystem and atmosphere.

    PubMed

    Zgorelec, Zeljka; Pehnec, Gordana; Bašić, Ferdo; Kisić, Ivica; Mesić, Milan; Zužul, Silva; Jurišić, Aleksandra; Sestak, Ivana; Vađić, Vladimira; Cačković, Mirjana

    2012-09-01

    Central gas station of the natural gas borehole system Podravina is located near the village Molve. It delivers more than a quarter of total energy used in Croatia to its consumers. Over the years, adapting technology to increasingly demanding and rigorous standards in environmental protection has become paramount. Yet, despite all the industry has undertaken to address the risk of harmful substances entering the food chain, a multidisciplinary research team of independent scientists monitors the content of specific substances in all components of the ecosystem. This paper presents measurements of total sulphur contents in soil surface [(0 to 3) cm] and subsurface [(3 to 8) cm] layers (study period: autumn 2006 - spring 2010) and in plants (study period: spring 2000 - spring 2010), and the concentration of gaseous sulphur compounds in the air. Concentrations of hydrogen sulphide (H2S) and mercaptans (RSH) were measured from the summer of 2002 until the autumn of 2010, while concentrations of sulphur dioxide (SO2) were measured from the spring of 2008 until the autumn of 2010. The paper also shows total annual atmospheric sulphur (S-SO4) deposition at Bilogora measuring station (study period: 2001 - 2010). Average monthly concentrations of H2S in air varied between 0.2 μg m-3 and 2.0 μg m-3, RSH between 0.1 μg m-3 and 24.5 μg m-3, and SO2 between 0.4 μg m-3 and 2.8 μg m-3 depending on the location and the season of sampling. Mean values of total sulphur in soil and in Plantago lanceolata plant ranged between 610 mg kg-1 and 1,599 mg kg-1 and between 3,614 mg kg-1 and 4,342 mg kg-1, respectively, depending on the soil type, location, and sampling depth. Average values of total sulphur mass ratio for all examined single soil samples (n=80) were 1,080 mg kg-1 for both studied layers, and 4,108 mg kg-1 for all analysed plant samples (n=85). Average total annual atmospheric sulphur deposition at Bilogora measuring station was 6.3 kg of S-SO4 per hectare. PMID:23152380

  2. Solar Wind Ablation of Terrestrial Planet Atmospheres

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Fok, Mei-Ching H.; Delcourt, Dominique C.

    2009-01-01

    Internal plasma sources usually arise in planetary magnetospheres as a product of stellar ablation processes. With the ignition of a new star and the onset of its ultraviolet and stellar wind emissions, much of the volatiles in the stellar system undergo a phase transition from gas to plasma. Condensation and accretion into a disk is replaced by radiation and stellar wind ablation of volatile materials from the system- Planets or smaller bodies that harbor intrinsic magnetic fields develop an apparent shield against direct stellar wind impact, but UV radiation still ionizes their gas phases, and the resulting internal plasmas serve to conduct currents to and from the central body along reconnected magnetic field linkages. Photoionization and thermalization of electrons warms the ionospheric topside, enhancing Jeans' escape of super-thermal particles, with ambipolar diffusion and acceleration. Moreover, observations and simulations of auroral processes at Earth indicate that solar wind energy dissipation is concentrated by the geomagnetic field by a factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Thus internal plasmas enable coupling with the plasma, neutral gas and by extension, the entire body. The stellar wind is locally loaded and slowed to develop the required power. The internal source plasma is accelerated and heated, inflating the magnetosphere as it seeks escape, and is ultimately blown away in the stellar wind. Bodies with little sensible atmosphere may still produce an exosphere of sputtered matter when exposed to direct solar wind impact. Bodies with a magnetosphere and internal sources of plasma interact more strongly with the stellar wind owing to the magnetic linkage between the two created by reconnection.

  3. Kinetics of Fast Atoms in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Kharchenko, Vasili A.; Dalgarno, A.; Mellott, Mary (Technical Monitor)

    2002-01-01

    This report summarizes our investigations performed under NASA Grant NAG5-8058. The three-year research supported by the Geospace Sciences SR&T program (Ionospheric, Thermospheric, and Mesospheric Physics) has been designed to investigate fluxes of energetic oxygen and nitrogen atoms in the terrestrial thermosphere. Fast atoms are produced due to absorption of the solar radiation and due to coupling between the ionosphere and the neutral thermospheric gas. We have investigated the impact of hot oxygen and nitrogen atoms on the thermal balance, chemistry and radiation properties of the terrestrial thermosphere. Our calculations have been focused on the accurate quantitative description of the thermalization of O and N energetic atoms in collisions with atom and molecules of the ambient neutral gas. Upward fluxes of oxygen and nitrogen atoms, the rate of atmospheric heating by hot oxygen atoms, and the energy input into translational and rotational-vibrational degrees of atmospheric molecules have been evaluated. Altitude profiles of hot oxygen and nitrogen atoms have been analyzed and compared with available observational data. Energetic oxygen atoms in the terrestrial atmosphere have been investigated for decades, but insufficient information on the kinetics of fast atmospheric atoms has been a main obstacle for the interpretation of observational data and modeling of the hot geocorona. The recent development of accurate computational methods of the collisional kinetics is seen as an important step in the quantitative description of hot atoms in the thermosphere. Modeling of relaxation processes in the terrestrial atmosphere has incorporated data of recent observations, and theoretical predictions have been tested by new laboratory measurements.

  4. Hydrogen and climate in primitive terrestrial and super-Earth atmospheres (Invited)

    NASA Astrophysics Data System (ADS)

    Wordsworth, R.

    2013-12-01

    For the three terrestrial planets with significant atmospheres in the Solar System (Earth, Venus and Mars), present-day conditions are oxidizing, with combinations of CO2, N2, O2 and H2O dominating by mass and in terms of the greenhouse effect. However, primitive terrestrial or ';super-Earth' exoplanet atmospheres may be much more reducing (i.e., hydrogen-rich), with major implications for climate, composition, and pre-biotic chemistry. Here I discuss recent work on the role of hydrogen in terrestrial planetary atmospheres, with a particular focus on the early Earth. I describe how collision-induced absorption (CIA) by hydrogen may have significantly warmed Earth's surface in the Archean and Hadean by blocking the critical water vapour absorption window at 800-1200 cm-1. This warming may have helped mitigate the faint young Sun effect early on. After the emergence of widespread methanogenesis, the consumption of H2 and CO2 should have led to a global shift in climate, with potentially observable consequences in the geological record. Because of variations in planetary mass, stellar XUV input and outgassing rates, hydrogen is also likely to be an important component of many super-Earth atmospheres. As I will discuss, this should have a significant effect on climate evolution and the carbon cycle on such planets, which should be considered in future predictions of atmospheric spectra and biosignatures.

  5. Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology

    NASA Technical Reports Server (NTRS)

    Schimel, David S.; Parton, William J.; Kittel, Timothy G. F.

    1991-01-01

    A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models couple primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that coupling of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.

  6. Transient simulations of Holocene atmospheric carbon dioxide and terrestrial carbon since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Joos, Fortunat; Gerber, Stefan; Prentice, I. C.; Otto-Bliesner, Bette L.; Valdes, Paul J.

    2004-06-01

    Conflicting hypotheses are investigated for the observed atmospheric CO2 increase of 20 ppm between 8 ka BP and pre-industrial time. The carbon component of the Bern Carbon Cycle Climate (Bern CC) model, which couples the Lund-Potsdam-Jena Dynamic Global Vegetation Model to an atmosphere-ocean-sediment component, is driven by climate fields from time-slice simulations of the past 21 ka with the Hadley Centre Unified Model or the NCAR Climate System Model. The entire Holocene ice core record of CO2 is matched within a few ppm for the standard model setup, and results are broadly consistent with proxy data of atmospheric 13CO2, mean ocean δ13C, and pollen data, within their uncertainties. Our analysis suggests that a range of mechanisms, including calcite compensation in response to earlier terrestrial uptake, terrestrial carbon uptake and release, SST changes, and coral reef buildup, contributed to the 20 ppm rise. The deep sea δ13C record constrains the contribution of the calcite compensation mechanism to 4-10 ppm. Terrestrial carbon inventory changes related to climate and CO2 forcing, the greening of the Sahara, peat buildup, and land use have probably influenced atmospheric CO2 by a few ppm only. The early Holocene CO2 decrease is quantitatively explained by terrestrial uptake and calcite compensation in response to terrestrial uptake during the glacial-interglacial transition. The recent hypothesis by [2003] that anthropogenic land use caused a 40 ppm CO2 anomaly over the past 8 ka, preventing the climate system from entering a new glacial, would imply an anthropogenic emission of 700 GtC and a decrease in atmospheric δ13C of 0.6 permil. This is not compatible with the ice core δ13C record and would require an upward revision of land use emission estimates by a factor of 3 to 4.

  7. ABIOTIC OXYGEN-DOMINATED ATMOSPHERES ON TERRESTRIAL HABITABLE ZONE PLANETS

    SciTech Connect

    Wordsworth, Robin; Pierrehumbert, Raymond

    2014-04-20

    Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is an atmosphere where oxygen is a major constituent. Here we show that lifeless habitable zone terrestrial planets around any star type may develop oxygen-dominated atmospheres as a result of water photolysis, because the cold trap mechanism that protects H{sub 2}O on Earth is ineffective when the atmospheric inventory of non-condensing gases (e.g., N{sub 2}, Ar) is low. Hence the spectral features of O{sub 2} and O{sub 3} alone cannot be regarded as robust signs of extraterrestrial life.

  8. Early terrestrial ecosystems: the animal evidence

    SciTech Connect

    Gray, J.

    1985-01-01

    Work on fossil spores indicates that plants at a level of vegetative organization comparable to bryophytes and vascular plants existed on land in the Early Silurian. Vascular plants, limnetic fishes, and probable Ascomycetes have Late Silurian records. Charophytes are known in the Late Silurian but may have been marine. The presence of microarthropods in the Ludlovian has been hypothesized from fungal masses in the Burgsvik Sandstone that closely resemble microarthropod frass. A number of microarthropods such as collembolans and mites are microphagous; these animals are among the earliest known from the Early Devonian. These fungal masses as animal traces have been given added credibility by the recovery of animal body fossils from basal Llandovery age fluvial deposits of the Central Appalachians that yield abundant plant spores but that lack marine invertebrates, phytoplankton or chitinozoans. The remains are abundant and sufficiently varied to suggest that they may represent a variety of organisms. Some are eurypterid-like, others grossly arthropod-like, although they may represent an unknown phylum or phyla. Many small invertebrates are associated with extant bryophytes, which have been viewed as stepping stones or halfway houses for them as they emerged from water onto land. The occurrence of these Early Silurian invertebrate remains with abundant spore tetrads, which Gray has hypothesized represent land plants at a bryophyte or hepatic grade of organization, is of great interest in trying to understand the early development of nonmarine ecosystems.

  9. Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Kharchenko, Vasili; Dalgarno, A.

    2005-01-01

    This report summarizes our research performed under NASA Grant NAG5-11857. The three-year grant have been supported by the Geospace Sciences SR&T program. We have investigated the energetic metastable oxygen and nitrogen atoms in the terrestrial stratosphere, mesosphere and thermosphere. Hot atoms in the atmosphere are produced by solar radiation, the solar wind and various ionic reactions. Nascent hot atoms arise in ground and excited electronic states, and their translational energies are larger by two - three orders of magnitude than the thermal energies of the ambient gas. The relaxation kinetics of hot atoms determines the rate of atmospheric heating, the intensities of aeronomic reactions, and the rate of atom escape from the planet. Modeling of the non-Maxwellian energy distributions of metastable oxygen and nitrogen atoms have been focused on the determination of their impact on the energetics and chemistry of the terrestrial atmosphere between 25 and 250 km . At this altitudes, we have calculated the energy distribution functions of metastable O and N atoms and computed non-equilibrium rates of important aeronomic reactions, such as destruction of the water molecules by O(1D) atoms and production of highly excited nitric oxide molecules. In the upper atmosphere, the metastable O(lD) and N(2D) play important role in formation of the upward atomic fluxes. We have computed the upward fluxes of the metastable and ground state oxygen atoms in the upper atmosphere above 250 km. The accurate distributions of the metastable atoms have been evaluated for the day and night-time conditions.

  10. Data Assimilation and Transport Modeling in Terrestrial and Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Houben, Howard C.; Young, Richard E. (Technical Monitor)

    2002-01-01

    Data assimilation is a blanket term used to describe a number of techniques for retrieving important physical parameters from observational data, subject to constraints imposed by prior knowledge (such as, in the case of meteorology, the primitive equations that govern atmospheric motion). Since these newly developed methods make efficient use of computational resources, they are of great importance in the interpretation of the voluminous datasets that are now produced by satellite missions. As proposed, these techniques have been applied to the study of the Martian and terrestrial atmospheres based on available satellite observations. In addition, a sophisticated hydrodynamic model (non-hydrostatic, and therefore applicable to the study of the interiors of the giant planets) has also been developed and successfully applied to the study of tidally induced motions in Jupiter.

  11. Terrestrial production vs. extraterrestrial delivery of prebiotic organics to the early Earth

    NASA Technical Reports Server (NTRS)

    Chyba, C. F.; Sagan, C.; Thomas, P. J.; Brookshaw, L.

    1991-01-01

    A comprehensive treatment of comet/asteroid interaction with the atmosphere, ensuring surface impact, and resulting organic pyrolysis is required to determine whether more than a negligible fraction of the organics in incident comets and asteroids actually survived collision with Earth. Results of such an investigation, using a smoothed particle hydrodynamic simulation of cometary and asteroidal impacts into both oceans and rock, demonstrate that organics will not survive impacts at velocities approx. greater than 10 km s(exp -1), and that even comets and asteroids as small as 100m in radius cannot be aerobraked to below this velocity in 1 bar atmospheres. However, for plausible dense (10 bar CO2) early atmospheres, there will be sufficient aerobraking during atmospheric passage for some organics to survive the ensuing impact. Combining these results with analytical fits to the lunar impact record shows that 4.5 Gyr ago Earth was accreting at least approx. 10(exp 6) kg yr(exp 1) of intact cometary organics, a flux which thereafter declined with a approx. 100 Myr half-life. The extent to which this influx was augmented by asteroid impacts, as well as the effect of more careful modelling of a variety of conservative approximations, is currently being quantified. These results may be placed in context by comparison with in situ organic production from a variety of terrestrial energy sources, as well as organic delivery by interplanetary dust. Which source dominated the early terrestrial prebiotic inventory is found to depend on the nature of the early terrestrial atmosphere. However, there is an intriguing symmetry: it is exactly those dense CO2 atmospheres where in situ atmospheric production of organic molecules should be the most difficult, in which intact cometary organics would be delivered in large amounts.

  12. Atmospheric Escape and Climate Evolution of Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Tian, F.; Chassefière, E.; Leblanc, F.; Brain, D.

    The climate of a planet is primarily determined by its orbital distance from its star, the luminosity of the star, the existence of oceans, the pressure of its atmosphere, and the composition of its atmosphere. The last two components are what could be impacted by atmosphere escape. The Sun, as the dominant energy source driving the climate of terrestrial planets, was not always as bright as it is today. Stellar evolution theory predicts that the luminosity of the young Sun was 75% of its present luminosity, at approximately 4 b.y. ago (4 Ga) (Gough, 1981). Although the Sun could have lost some of its mass, thus making the very young Sun somewhat more massive than it is now and therefore could have emitted more energy, most of this mass loss was completed prior to 4 Ga (Wood et al., 2005). Thus the Sun has provided increasingly more energy to solar system planets during the past 4 b.y. Contrary to the evolutionary trend of the total luminosity increasing with time, the young Sun should have emitted much stronger EUV, soft X-ray, and far-UV photons than at present. These photons are from the upper atmosphere of the Sun and are linked to solar magnetic activity. Generally speaking, a young star rotates much faster and thus has stronger magnetic activity. Observations of solar-type stars with different ages show that the EUV energy flux from a 0.5-b.y.-old solar-type star could be as much as 20 times that of the present Sun (Ribas et al., 2005). Accompanying this much-enhanced solar extreme ultraviolet (XUV) radiation is a much stronger solar wind, with mass flux up to 1000 times more intense than the present solar wind flux (Wood et al., 2005). It can be expected that many more energetic-particle events were caused by the young Sun. The fate of the atmospheres of terrestrial planets in such an environment and the consequences for their climates are the focus of this chapter.

  13. Are terrestrial mosses good biomonitors of atmospheric deposition of Mn?

    NASA Astrophysics Data System (ADS)

    Boquete, M. T.; Fernndez, J. A.; Aboal, J. R.; Carballeira, A.

    2011-05-01

    A series of field and laboratory experiments was carried out to determine whether the terrestrial moss Pseudoscleropodium purum is a good biomonitor of the atmospheric deposition of Mn. Samples of the species were collected from sampling sites located in industrial areas and in unpolluted areas in Galicia (NW Spain). The results showed that: i) uptake of Mn by the moss may be reduced under certain conditions (related with the environment, moss ecophysiology and source and type of emission), even though atmospheric inputs and inputs from vegetation remain the same. The concentration of Mn in moss samples from the surroundings of an aluminium smelter was 6 times lower than in samples from an unpolluted site, in which levels were similar to the regional background level. The low concentrations were maintained over time; ii) the decrease in the uptake of Mn was due to differences in the environmental conditions to which the organisms are exposed. Genetic causes for the differences were ruled out as the study of moss samples transplanted within and between unpolluted and contaminated areas showed that the final concentrations in the transplanted moss in each of the scenarios were very similar; iii) the direct relationship between exposure and concentration was altered in the surroundings of the contaminated sampling site, although the causes of the inhibition of uptake could not be established by incubation of moss samples under laboratory conditions, and v) unlike other metals, there are few sources of emission of Mn to the atmosphere. However, when the emissions were in a particulate form, the concentrations of Mn in the moss varied in accordance with the atmospheric deposition. For all of these reasons, we consider that P. purum is not a good biomonitor of the atmospheric deposition of Mn, except under certain circumstances, and we recommend exclusion of the element from regional surveys.

  14. Early Martian environments - The antarctic and other terrestrial analogs

    NASA Technical Reports Server (NTRS)

    Wharton, R. A., Jr.; Mckay, C. P.; Mancinelli, R. L.; Simmons, G. M., Jr.

    1989-01-01

    The comparability of the early environments of Mars and earth, and the biological evolution which occurred on early earth, motivates serious consideration of the possibility of an early Martian biota. Environments which could have contained this early Martian life and which may presently contain evidence of this former life include aquatic, ice, soil, and rock habitats. Several analogs of these potential early Martian environments, which can provide useful information in searching for extinct life on Mars, are currently available for study on earth. These terrestrial analogs include the perennially ice-covered lakes and sandstone rocks in the polar deserts of Antarctica, surface of snowfields and glaciers, desert soils, geothermal springs, and deep subsurface environments.

  15. Contribution of natural terrestrial sources to the atmospheric chloroform budget

    NASA Astrophysics Data System (ADS)

    Rhew, R. C.; Abel, T.; Pan, D.; Whelan, M.

    2008-12-01

    Chloroform (trichloromethane, CHCl3) is the second largest carrier of natural chlorine in the troposphere after methyl chloride, contributing to the reactive chlorine burden in the troposphere and to ozone destruction in the stratosphere. Our understanding of the biogeochemical cycling of atmospheric CHCl3 has undergone major adjustments recently, including the quantification of the total atmospheric burden of this compound, the estimated global source and sink strengths, and the relative contributions of anthropogenic versus natural contributions. Numerous natural terrestrial sources have been identified, including temperate peatlands, Arctic tundra, termite mounds, salt marshes, grasslands, forests and woodlands. However, the wide variability of fluxes within each ecosystem has complicated efforts to quantify the overall terrestrial source. In addition, the environmental and biogeochemical controls remain largely unknown. We shall present a comparison of recent CHCl3 flux measurements that cover a range of biome types and climatic conditions. To address within-biome variability, flux measurements from the Arctic tundra and temperate grasslands will be compared to common environmental parameters (e.g., temperature, soil moisture, solar insolation) and other trace gas fluxes (CH3Cl, CH4, CCl4). The generally poor correlations demonstrate that the variability of CHCl3 emissions may be affected by site-specific parameters that are not currently measured or by drastic changes in hydrologic conditions. Similar patterns are observed in laboratory incubations of tundra peat and grassland soils. We explore the possibility that the humification of plant material, which has been shown to produce organochlorine compounds through the chlorination of organic matter, may contribute to CHCl3 emissions. If this link exists, then CHCl3 production could potentially act as a proxy for organic matter degradation and carbon sequestration, essential biogeochemical and ecosystem processes.

  16. Dissipation of the Primordial Terrestrial Atmosphere Due to Irradiation of the Solar EUV

    NASA Astrophysics Data System (ADS)

    Sekiya, M.; Nakazawa, K.; Hayashi, C.

    1980-12-01

    The escape of a primordial Earth's atmosphere due to heating by solar radiation is studied by integrating numerically hydrodynamic equations for steady and spherically-symmetric outflow of hydrogen molecules and helium atoms. As heating sources, we take account of (1) the solar EUV radiation which is expected to be very strong during the T Tauri stage, (2) the solar visible light and (3) the release of gravitational energy of accreting planetesimals. The effect of solar wind is neglected but the condition of this neglect is estimated. The results show that the primordial atmosphere, having existed in the early stage of the Earth's history, is dissipated with a period of 5 × 108 y, which is the upper limit imposed from the origin of the present terrestrial atmosphere, as far as the solar EUV flux is more than 2 × 102 times as large as the present one.

  17. Morphological Biosignatures in Early Terrestrial and Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Westall, Frances

    2008-03-01

    Biosignatures in early terrestrial rocks are highly relevant in the search for traces of life on Mars because the early geological environments of the two planets were, in many respects, similar and, thus, the potential habitats for early life forms were similar. However, the identification and interpretation of biosignatures in ancient terrestrial rocks has proven contentious over the last few years. Recently, new investigations using very detailed field studies combined with highly sophisticated analytical techniques have begun to document a large range of biosignatures in Early Archaean rocks. Early life on Earth was diversified, widespread and relatively evolved, but its traces are generally, but not always, small and subtle. In this contribution I use a few examples of morphological biosignatures from the Early-Mid Archaean to demonstrate their variety in terms of size and type: macroscopic stromatolites from the 3.443 Ga Strelley Pool Chert, Pilbara; a meso-microscopic microbial mat from the 3.333 Ga Josefsdal Chert, Barberton; microscopic microbial colonies and a biofilm from the 3.446 Ga Kitty’s Gap Chert, Pilbara; and microscopic microbial corrosion pits in the glassy rinds of 3.22-3.48 Ga pillow lavas from Barberton. Some macroscopic and microscopic structures may be identifiable in an in situ robotic mission to Mars and in situ methods of organic molecule detection may be able to reveal organic traces of life. However, it is concluded that it will probably be necessary to return suitably chosen Martian rocks to Earth for the reliable identification of signs of life, since multiple observational and analytical methods will be necessary, especially if Martian life is significantly different from terrestrial life.

  18. Morphological Biosignatures in Early Terrestrial and Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Westall, Frances

    Biosignatures in early terrestrial rocks are highly relevant in the search for traces of life on Mars because the early geological environments of the two planets were, in many respects, similar and, thus, the potential habitats for early life forms were similar. However, the identification and interpretation of biosignatures in ancient terrestrial rocks has proven contentious over the last few years. Recently, new investigations using very detailed field studies combined with highly sophisticated analytical techniques have begun to document a large range of biosignatures in Early Archaean rocks. Early life on Earth was diversified, widespread and relatively evolved, but its traces are generally, but not always, small and subtle. In this contribution I use a few examples of morphological biosignatures from the Early-Mid Archaean to demonstrate their variety in terms of size and type: macroscopic stromatolites from the 3.443 Ga Strelley Pool Chert, Pilbara; a meso-microscopic microbial mat from the 3.333 Ga Josefsdal Chert, Barberton; microscopic microbial colonies and a biofilm from the 3.446 Ga Kitty's Gap Chert, Pilbara; and microscopic microbial corrosion pits in the glassy rinds of 3.22-3.48 Ga pillow lavas from Barberton. Some macroscopic and microscopic structures may be identifiable in an in situ robotic mission to Mars and in situ methods of organic molecule detection may be able to reveal organic traces of life. However, it is concluded that it will probably be necessary to return suitably chosen Martian rocks to Earth for the reliable identification of signs of life, since multiple observational and analytical methods will be necessary, especially if Martian life is significantly different from terrestrial life.

  19. Water loss from terrestrial planets with CO{sub 2}-rich atmospheres

    SciTech Connect

    Wordsworth, R. D.; Pierrehumbert, R. T.

    2013-12-01

    Water photolysis and hydrogen loss from the upper atmospheres of terrestrial planets is of fundamental importance to climate evolution but remains poorly understood in general. Here we present a range of calculations we performed to study the dependence of water loss rates from terrestrial planets on a range of atmospheric and external parameters. We show that CO{sub 2} can only cause significant water loss by increasing surface temperatures over a narrow range of conditions, with cooling of the middle and upper atmosphere acting as a bottleneck on escape in other circumstances. Around G-stars, efficient loss only occurs on planets with intermediate CO{sub 2} atmospheric partial pressures (0.1-1 bar) that receive a net flux close to the critical runaway greenhouse limit. Because G-star total luminosity increases with time but X-ray and ultraviolet/ultravoilet luminosity decreases, this places strong limits on water loss for planets like Earth. In contrast, for a CO{sub 2}-rich early Venus, diffusion limits on water loss are only important if clouds caused strong cooling, implying that scenarios where the planet never had surface liquid water are indeed plausible. Around M-stars, water loss is primarily a function of orbital distance, with planets that absorb less flux than ∼270 W m{sup –2} (global mean) unlikely to lose more than one Earth ocean of H{sub 2}O over their lifetimes unless they lose all their atmospheric N{sub 2}/CO{sub 2} early on. Because of the variability of H{sub 2}O delivery during accretion, our results suggest that many 'Earth-like' exoplanets in the habitable zone may have ocean-covered surfaces, stable CO{sub 2}/H{sub 2}O-rich atmospheres, and high mean surface temperatures.

  20. Processes Impacting Atmosphere-Surface Exchanges at Arctic Terrestrial Sites

    NASA Astrophysics Data System (ADS)

    Persson, Ola; Grachev, Andrey; Konopleva, Elena; Cox, Chris; Stone, Robert; Crepinsek, Sara; Shupe, Matthew; Uttal, Taneil

    2015-04-01

    Surface energy fluxes are key to the annual cycle of near-surface and soil temperature and biologic activity in the Arctic. While these energy fluxes are undoubtedly changing to produce the changes observed in the Arctic ecosystem over the last few decades, measurements have generally not been available to quantify what processes are regulating these fluxes and what is determining the characteristics of these annual cycles. The U.S. National Oceanic and Atmospheric Administration has established, or contributed to the establishment of, several terrestrial "supersites" around the perimeter of the Arctic Ocean at which detailed measurements of atmospheric structure, surface fluxes, and soil thermal properties are being made. These sites include Barrow, Alaska; Eureka and Alert, Canada; and Tiksi, Russia. Atmospheric structure measurements vary, but include radiosoundings at all sites and remote sensing of clouds at two sites. Additionally, fluxes of sensible heat and momentum are made at all of the sites, while fluxes of moisture and CO2 are made at two of the sites. Soil temperatures are also measured in the upper 120 cm at all sites, which is deep enough to define the soil active layer. The sites have been operating between 3 years (Tiksi) and 24 years (Barrow). While all sites are located north of 71° N, the summer vegetation range from lush tundra grasses to rocky soils with little vegetation. This presentation will illustrate some of the atmospheric processes that are key for determining the annual energy and temperature cycles at these sites, and some of the key characteristics that lead to differences in, for instance, the length of the summer soil active layer between the sites. Atmospheric features and processes such as cloud characteristics, snowfall, downslope wind events, and sea-breezes have impacts on the annual energy cycle. The presence of a "zero curtain" period, when autumn surface temperature remains approximately constant at the freezing point for up to a month, seems to be a characteristic of the autumn freeze-up in the annual energy cycle at some of the sites.

  1. North America's net terrestrial carbon exchange with the atmosphere 1990-2009

    NASA Astrophysics Data System (ADS)

    King, A. W.; Andres, R. J.; Davis, K. J.; Hafer, M.; Hayes, D. J.; Huntzinger, D. N.; de Jong, B.; Kurz, W. A.; McGuire, A. D.; Vargas, R.; Wei, Y.; West, T. O.; Woodall, C. W.

    2014-07-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil-fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America over the period (1990-2009). This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North America land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the atmospheric inversion estimate forms the lower bound of that range (a larger land-sink) and the inventory-based estimate the upper (a smaller land sink). Integrating across estimates, "best" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil-fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. The continent's CO2 source to sink ratio for this time period was likely in the range of 4 : 1 to 3 : 1.

  2. North America s net terrestrial CO2 exchange with the atmosphere 1990-2009

    SciTech Connect

    King, Anthony Wayne; Andres, Robert Joseph; Davis, Ken J.; Hafer, Mark; Hayes, Daniel J; Huntzinger, Deborah N; De Jong, Ben; Kurz, Werner; McGuire, Anthony; Vargas, Roberto; Wei, Yaxing; West, Tristam O.; Woodall, Christopher

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil-fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America over the period (1990-2009). This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North America land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the atmospheric inversion estimate forms the lower bound of that range (a larger land-sink) and the inventory-based estimate the upper (a smaller land sink). Integrating across estimates, a best estimates (i.e., measures of central tendency) are -472 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil-fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. The continent s CO2 source to sink ratio for this time period was likely in the range of 4:1 to 3:1.

  3. Atmospheric Dynamics of Terrestrial Exoplanets over a Wide Range of Orbital and Atmospheric Parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Yohai; Showman, Adam P.

    2015-05-01

    The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.

  4. Atmospheric Dynamics of Terrestrial Exoplanets Over a Wide Range of Orbital and Atmospheric Parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Yohai; Showman, Adam P.

    2014-11-01

    Since the mid-1990s, nearly 1800 exoplanets have been discovered around other stars. Exoplanet discovery and characterization began with giant planets, but as the observational techniques are advancing the emphasis is gradually shifting to smaller worlds. The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters suggests that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone---including transitions to Snowball-like states and runaway-greenhouse feedbacks---depend on the equator-to-pole temperature differences, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we discuss the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass, surface gravity, heat flux from a parent star, optical thickness and atmospheric mass affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet stream, Hadley and Ferrel cells and latitudinal temperature differences. Finally, we will discuss how the atmospheric dynamics influence the global-scale climate feedbacks that control the width of the habitable zone, and their effects on the global climate.

  5. Evolution of an early Titan atmosphere

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.; Volkov, A. N.

    2016-06-01

    Rapid escape from a proposed early CH4/NH3 atmosphere on Titan could, in principle, limit the amount of NH3 that is converted by photolysis into the present N2 atmosphere. Assuming that this conversion occurred, a recent estimate of escape driven by the surface temperature and pressure was used to constrain Titan's accretion temperature. Here we show that for the range of temperatures of interest, heating of the surface is not the primary driver for escape. Atmospheric loss from a thick Titan atmosphere is predominantly driven by heating of the upper atmosphere; therefore, the loss rate cannot be used to easily constrain the accretion temperature. We give an estimate of the solar driven escape rate from an early atmosphere on Titan, and then briefly discuss its relevance to the cooling rate, isotope ratios, and the time period suggested to convert NH3 to the present N2 atmosphere.

  6. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    USGS Publications Warehouse

    King, A.W.; Andres, R.J.; Davis, K.J.; Hafer, M.; Hayes, D.J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, W.A.; McGuire, Anthony; Vargas, Rodrigo I.; Wei, Y.; West, Tristram O.; Woodall, Christopher W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

  7. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    DOE PAGESBeta

    King, Anthony W.; Andres, Robert; Davis, Kenneth J.; Hafer, M.; Hayes, Daniel J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, Werner; McGuire, A. David; Vargas, Rodrigo; et al

    2015-01-21

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North Americanmore » land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, \\"best\\" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.« less

  8. North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

    SciTech Connect

    King, Anthony W.; Andres, Robert; Davis, Kenneth J.; Hafer, M.; Hayes, Daniel J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, Werner; McGuire, A. David; Vargas, Rodrigo; Wei, Yaxing; West, Tristram O.; Woodall, Chris W.

    2015-01-21

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, \\"best\\" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

  9. North America's net terrestrial CO2 exchange with the atmosphere 1990-2009

    NASA Astrophysics Data System (ADS)

    King, A. W.; Andres, R. J.; Davis, K. J.; Hafer, M.; Hayes, D. J.; Huntzinger, D. N.; de Jong, B.; Kurz, W. A.; McGuire, A. D.; Vargas, R.; Wei, Y.; West, T. O.; Woodall, C. W.

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990-2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990-2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

  10. Ecological impacts of atmospheric CO2 enrichment on terrestrial ecosystems.

    PubMed

    Körner, Christian

    2003-09-15

    Global change has many facets, of which land use and the change of atmospheric chemistry are unquestioned primary agents, which induce a suite of secondary effects, including climatic changes. The largest single contribution to the compositional change of the atmosphere, CO(2) enrichment, has (besides its influence on climate) immediate and direct effects on plants. Quantitatively, CO(2) is the plant 'food' number one, and the rate of photosynthetic CO(2) uptake by leaves is not yet CO(2)-saturated. This abrupt change of the biosphere's diet does and will affect all aspects of life, including our food. However, the plant and ecosystem responses are more subtle than had been assumed from the results of responses of isolated, well-fertilized and well-watered plants in greenhouses during the early days of CO(2)-enrichment research. In this article, I discuss potential responses of complex natural grassland and diverse forests, and address three key themes: CO(2) and nutrients; CO(2) and water; CO(2) and plant-animal interactions. Examples from a suite of climatic regions emphasize that the most important ecosystem level responses to elevated CO(2) will be introduced by differential responses of species. Atmospheric CO(2) enrichment is a biodiversity issue. Classical physiological baseline responses of leaves to elevated CO(2) can be overrun by biodiversity effects to such an extent that some of the traditional predictions may even become reversed. For instance, biodiversity effects may cause humid tropical forests (those which avoid destruction) to become more dynamic and store less, rather than more, carbon as CO(2) enrichment continues. The abundance of certain life forms and species and their lifespans exert major controls over the half-life of carbon stored in forest biomass, and there is evidence that elevated CO(2) can affect these controls and most likely does so already. Also, long-term hydrological consequences of atmospheric CO(2) enrichment will be driven by biodiversity effects, given that some, but not all, species reduce their rate of water loss when exposed to a CO(2)-rich atmosphere. Such insights call for much more realistic experimental conditions and larger-scale test units, which permit biotic interactions across taxa and trophic levels to occur while simulating our CO(2) future. The evidence currently available suggests that ecosystem processes reflect the composition of their biological inventory and this will be affected by a shift in carbon supply. PMID:14558907

  11. A massive early atmosphere on Triton

    NASA Technical Reports Server (NTRS)

    Lunine, Jonathan I.; Nolan, Michael C.

    1992-01-01

    The idea of an early greenhouse atmosphere for Triton is presented and the conditions under which it may have been sustained are quantified. The volatile content of primordial Triton is modeled, and tidal heating rates are assessed to set bounds on the available energy. The atmospheric model formalism is presented, and it is shown how a massive atmosphere could have been raised by modest tidal heating fluxes. The implications of the model atmospheres for the atmospheric escape rates, the chemical evolution, and the cratering record are addressed.

  12. Contribution of the terrestrial biosphere to interannual variations in atmospheric CO{sub 2}

    SciTech Connect

    King, A.W.; Post, W.M.; Wullschleger, S.D.

    1995-06-01

    Interannual fluctuations in atmospheric CO{sub 2} concentration may reflect interannual variations in the CO{sub 2} source/sink strength of the terrestrial biosphere. Recurrent changes in climate like those associated with El Nino events and episodic changes like those associated with the Mt. Pinatubo eruption could alter the global balance between terrestrial net primary production and heterotrophic (decomposer) respiration and thus influence net CO{sub 2} exchange with the atmosphere. A georeferenced global terrestrial biosphere model (0.5{degrees} spatial resolution and monthly temporal resolution) was used to simulate interannual variations in net CO{sub 2} exchange with the atmosphere. The model was driven with monthly temperature and precipitation data for the period 1900 to present. Interannual variations in simulated net CO{sub 2} exchange were compared with historical records of atmospheric CO{sub 2}. Consecutive years of an enhanced terrestrial sink were associated with periods of declining atmospheric CO{sub 2} concentration; consecutive years of enhanced source strength were associated with positive atmospheric CO{sub 2} anomalies. We conclude that interannual variations in terrestrial biospheric carbon flux contribute significantly to interannual variations in atmospheric CO{sub 2}.

  13. Relating GRACE terrestrial water storage variations to global fields of atmospheric forcing

    NASA Astrophysics Data System (ADS)

    Humphrey, Vincent; Gudmundsson, Lukas; Isabelle Seneviratne, Sonia

    2015-04-01

    Synoptic, seasonal and inter-annual fluctuations in atmospheric dynamics all influence terrestrial water storage, with impacts on ecosystems functions, human activities and land-climate interactions. Here we explore to which degree atmospheric variables can explain GRACE estimates of terrestrial water storage on different time scales. Since 2012, the most recent GRACE gravity field solutions (Release 05) can be used to monitor global changes in terrestrial water storage with an unprecedented level of accuracy over more than a decade. In addition, the release of associated gridded and post-processed products facilitates comparisons with other global datasets such as land surface model outputs or satellite observations. We investigate how decadal trends, inter-annual fluctuations as well as monthly anomalies of the seasonal cycle of terrestrial water storage can be related to fields of atmospheric forcing, including e.g. precipitation and temperature as estimated in global reanalysis products using statistical techniques. In the majority of the locations with high signal to noise ratio, both short and long-term fluctuations of total terrestrial water storage can be reconstructed to a large degree based on available atmospheric forcing. However, in some locations atmospheric forcing alone is not sufficient to explain the total change in water storage, suggesting strong influence of other processes. Within that framework, the question of an amplification or attenuation of atmospheric forcing through land-surface feedbacks and changes in long term water storage is discussed, also with respect to uncertainties and potential systematic biases in the results.

  14. The Center for the Study of Terrestrial and Extraterrestrial Atmospheres (CSTEA)

    NASA Technical Reports Server (NTRS)

    Thorpe, Arthur N.; Morris, Vernon R.

    1997-01-01

    The Center for the Study of Terrestrial and Extraterrestrial Atmospheres (CSTEA) was established in 1992. The center began with 14 active Principal Investigators (PI's). The research of the Center's PIs has, for the most part, continued in the same four areas as presented in the original proposal: Remote Sensing, Atmospheric Chemistry, Sensors and Detectors, and Spacecraft Dynamics.

  15. Atmospheric transport of persistent pollutants governs uptake by holarctic terrestrial biota

    SciTech Connect

    Larsson, P.; Okla, L.; Woin, Per )

    1990-10-01

    The atmospheric deposition of PCBs, DDT, and lindane, governed uptake in terrestrial biota in the Scandinavian peninsula. Mammalian herbivores and predators as well as predatory insects contained higher levels of pollutants at locations where the fallout load was high than at stations where atmospheric deposition was lower, and the two variables were significantly correlated.

  16. On the (anticipated) diversity of terrestrial planet atmospheres

    NASA Astrophysics Data System (ADS)

    Leconte, Jérémy; Forget, François; Lammer, Helmut

    2015-12-01

    On our way toward the characterization of smaller and more temperate planets, missions dedicated to the spectroscopic observation of exoplanets will teach us about the wide diversity of classes of planetary atmospheres, many of them probably having no equivalent in the Solar System. But what kind of atmospheres can we expect? To start answering this question, many theoretical studies have tried to understand and model the various processes controlling the formation and evolution of planetary atmospheres, with some success in the Solar System. Here, we shortly review these processes and we try to give an idea of the various type of atmospheres that these processes can create. As will be made clear, current atmosphere evolution models have many shortcomings yet, and need heavy calibrations. With that in mind, we will thus discuss how observations with a mission similar to EChO would help us unravel the link between a planet's environment and its atmosphere.

  17. Origin of the atmospheres of the terrestrial planets

    SciTech Connect

    Cameron, A.G.W.

    1983-11-01

    The monotonic decrease in the atmospheric abundance of per gram of planet in the sequence, Venus, earth, and Mars has been assumed to reflect some conditions in the primitive solar nebula at the time of formation of the planetary atmospheres, having to do either with the composition of the nebula itself or the composition of the trapped gases in small solid bodies in the nebula. Behind such hypotheses lies the assumption that planetary atmospheres steadily gain components. However, not only can gases enter atmospheres they may also be lost from atmospheres both by adsorption into the planetary interior and by loss into space as a result of collisions with minor and major planetesimals. In this paper a necessarily qualitative discussion is given of the problem of collisions with minor planetesimals, a process called atmospheric cratering or atmospheric erosion, and a discussion is given of atmospheric loss accompanying collision of a planet with a major planetesimal, such as may have produced the earth's moon. 17 references.

  18. Proposed reference models for atomic oxygen in the terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Llewellyn, E. J.; Mcdade, I. C.; Lockerbie, M. D.

    1989-01-01

    A provisional Atomic Oxygen Reference model was derived from average monthly ozone profiles and the MSIS-86 reference model atmosphere. The concentrations are presented in tabular form for the altitude range 40 to 130 km.

  19. Biogeochemistry of CO sub 2 exchange between terrestrial ecosystems and the atmosphere

    SciTech Connect

    Dale, V.H.; Houghton, R.A. Woods Hole Research Center, MA )

    1988-09-01

    Changes in the amount of carbon stored in terrestrial ecosystems are, in part, responsible for the increase in atmospheric CO{sub 2} levels, as observed since about 1750. Changes in atmospheric CO{sub 2} may affect future climate conditions. Therefore, it is important to understand both the distribution of carbon in terrestrial systems and the factors changing that distribution. There are three major sources of uncertainty in estimates of carbon release from terrestrial ecosystems due to land use changes: (1) uncertainties in rates of deforestation, land clearing, and abandonment; (2) uncertainties in estimates of the carbon in biomass of managed and unmanaged ecosystems; and (3) uncertainties in rates of change in carbon storage following conversion from one land use to another. Obtaining better quantitative estimates of these three factors will improve understanding of the effect of land use changes on the flux of carbon from the land to the atmosphere.

  20. Evaluation of terrestrial carbon cycle models with atmospheric CO2 measurements: Results from transient simulations considering increasing CO2, climate, and land-use effects

    USGS Publications Warehouse

    Dargaville, R.J.; Heimann, Martin; McGuire, A.D.; Prentice, I.C.; Kicklighter, D.W.; Joos, F.; Clein, J.S.; Esser, G.; Foley, J.; Kaplan, J.; Meier, R.A.; Melillo, J.M.; Moore, B., III; Ramankutty, N.; Reichenau, T.; Schloss, A.; Sitch, S.; Tian, H.; Williams, L.J.; Wittenberg, U.

    2002-01-01

    An atmospheric transport model and observations of atmospheric CO2 are used to evaluate the performance of four Terrestrial Carbon Models (TCMs) in simulating the seasonal dynamics and interannual variability of atmospheric CO2 between 1980 and 1991. The TCMs were forced with time varying atmospheric CO2 concentrations, climate, and land use to simulate the net exchange of carbon between the terrestrial biosphere and the atmosphere. The monthly surface CO2 fluxes from the TCMs were used to drive the Model of Atmospheric Transport and Chemistry and the simulated seasonal cycles and concentration anomalies are compared with observations from several stations in the CMDL network. The TCMs underestimate the amplitude of the seasonal cycle and tend to simulate too early an uptake of CO2 during the spring by approximately one to two months. The model fluxes show an increase in amplitude as a result of land-use change, but that pattern is not so evident in the simulated atmospheric amplitudes, and the different models suggest different causes for the amplitude increase (i.e., CO2 fertilization, climate variability or land use change). The comparison of the modeled concentration anomalies with the observed anomalies indicates that either the TCMs underestimate interannual variability in the exchange of CO2 between the terrestrial biosphere and the atmosphere, or that either the variability in the ocean fluxes or the atmospheric transport may be key factors in the atmospheric interannual variability.

  1. PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. I. PHOTOCHEMISTRY MODEL AND BENCHMARK CASES

    SciTech Connect

    Hu Renyu; Seager, Sara; Bains, William

    2012-12-20

    We present a comprehensive photochemistry model for exploration of the chemical composition of terrestrial exoplanet atmospheres. The photochemistry model is designed from the ground up to have the capacity to treat all types of terrestrial planet atmospheres, ranging from oxidizing through reducing, which makes the code suitable for applications for the wide range of anticipated terrestrial exoplanet compositions. The one-dimensional chemical transport model treats up to 800 chemical reactions, photochemical processes, dry and wet deposition, surface emission, and thermal escape of O, H, C, N, and S bearing species, as well as formation and deposition of elemental sulfur and sulfuric acid aerosols. We validate the model by computing the atmospheric composition of current Earth and Mars and find agreement with observations of major trace gases in Earth's and Mars' atmospheres. We simulate several plausible atmospheric scenarios of terrestrial exoplanets and choose three benchmark cases for atmospheres from reducing to oxidizing. The most interesting finding is that atomic hydrogen is always a more abundant reactive radical than the hydroxyl radical in anoxic atmospheres. Whether atomic hydrogen is the most important removal path for a molecule of interest also depends on the relevant reaction rates. We also find that volcanic carbon compounds (i.e., CH{sub 4} and CO{sub 2}) are chemically long-lived and tend to be well mixed in both reducing and oxidizing atmospheres, and their dry deposition velocities to the surface control the atmospheric oxidation states. Furthermore, we revisit whether photochemically produced oxygen can cause false positives for detecting oxygenic photosynthesis, and find that in 1 bar CO{sub 2}-rich atmospheres oxygen and ozone may build up to levels that have conventionally been accepted as signatures of life, if there is no surface emission of reducing gases. The atmospheric scenarios presented in this paper can serve as the benchmark atmospheres for quickly assessing the lifetime of trace gases in reducing, weakly oxidizing, and highly oxidizing atmospheres on terrestrial exoplanets for the exploration of possible biosignature gases.

  2. Stability of ammonia in the primitive terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.

    1982-01-01

    The rate at which ammonia would have been destroyed in the earth's atmosphere under assumed NH3 mixing ratio conditions of 10 to the -8th to 0.0001 is calculated by a one-dimensional photochemical model, and the destruction rates are compared with possible biotic and abiotic ammonia sources. It is found that, while the mixing ratio of 10 to the -8th needed for the evolution of life could have been maintained by abiotic sources, the value of 0.00001 needed for the production of significant greenhouse warming could not have been sustained abiotically. The increase of atmospheric ammonia due to biological activities during the Archean is also considered lower than the level required for the generation of measurable thermal effects.

  3. The Martian atmospheric water cycle as viewed from a terrestrial perspective

    NASA Technical Reports Server (NTRS)

    Zurek, Richard W.

    1988-01-01

    It is noted that the conditions of temperature and pressure that characterize the atmosphere of Mars are similar to those found in the Earth's stratosphere. Of particular significance is the fact that liquid water is unstable in both environments. Thus, it is expected that terrestrial studies of the dynamical behavior of stratospheric water should benefit the understanding of water transport on Mars as well.

  4. Carbon in the atmosphere and terrestrial biosphere in the 21st century

    NASA Astrophysics Data System (ADS)

    Malhi, Yadvinder

    2002-12-01

    The release of carbon dioxide from fossil-fuel combustion and land-use change has caused a significant perturbation in the natural cycling of carbon between land, atmosphere and oceans. Understanding and managing the effects of this disruption on atmospheric composition and global climate are likely to be amongst the most pressing issues of the 21st century. However, the present-day carbon cycle is still poorly understood. One remarkable feature is that an increasing amount of atmospheric carbon dioxide appears to be being absorbed by terrestrial vegetation. I review the recent evidence for the magnitude and spatial distribution of this 'terrestrial carbon sink', drawing on current research on the global atmospheric distribution and transport of carbon dioxide, oxygen and their isotopes; direct measurement of CO2 fluxes above various biomes; and inventories of forest biomass and composition. I review the likely causes of these carbon sinks and sources and their implications for the ecology and stability of these biomes. Finally, I examine prospects and key issues over coming decades. Within a few years, satellite measurements of atmospheric CO2 and forest biomass, coupled with 'real-time' biosphere-atmosphere models, will revolutionize our understanding of the terrestrial carbon cycle. Controlling deforestation and managing forests has the potential to play a significant but limited part in reaching the goal of stabilizing atmospheric CO2 concentrations. However, there are likely to be limits to the amount of carbon storage possible in natural vegetation, and, in the long term, terrestrial carbon storage may be unstable, with the potential to accelerate rather than brake global warming.

  5. The early atmosphere: a new picture.

    PubMed

    Levine, J S

    1986-01-01

    Over the last several years, many of the fundamental ideas concerning the composition and chemical evolution of the Earth's early atmosphere have changed. While many aspects of this subject are clouded--either uncertain or unknown, a new picture is emerging. We are just beginning to understand how astronomical, geochemical, and atmospheric processes each contributed to the development of the gaseous envelope around the third planet from the sun some 4.6 billion years ago and how that envelope chemically evolved over the history of our planet. Simple compounds in that gaseous envelope, energized by atmospheric lightning and/or solar ultraviolet radiation, formed molecules of increasing complexity that eventually evolved into the first living systems on our planet. This process is called "chemical evolution" and immediately preceded biological evolution; once life developed and evolved, it began to alter the chemical composition of the atmosphere that provided the very essence of its creation. Photosynthetic organisms which have the ability to biochemically transform carbon dioxide and water to carbohydrates, which they use for food, produce large amounts of molecular oxygen (O2) as a by-product of the reaction. Atmospheric oxygen photochemically formed ozone, which absorbs ultraviolet radiation from the sun and shields the Earth's surface from this biologically lethal radiation. Once atmospheric ozone levels increased sufficiently, life could leave the safety of the oceans and go ashore for the first time. Throughout the history of our planet, there has been strong interaction between life and the atmosphere. Understanding our cosmic roots is particularly relevant as we embark on a search for life outside the Earth. At this very moment, several radio telescopes around the world are searching for extraterrestrial intelligence (SETI). PMID:11542093

  6. The Evolution of Stellar Rotation and the Hydrogen Atmospheres of Habitable-zone Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Johnstone, C. P.; Güdel, M.; Stökl, A.; Lammer, H.; Tu, L.; Kislyakova, K. G.; Lüftinger, T.; Odert, P.; Erkaev, N. V.; Dorfi, E. A.

    2015-12-01

    Terrestrial planets formed within gaseous protoplanetary disks can accumulate significant hydrogen envelopes. The evolution of such an atmosphere due to XUV driven evaporation depends on the activity evolution of the host star, which itself depends sensitively on its rotational evolution, and therefore on its initial rotation rate. In this Letter, we derive an easily applicable method for calculating planetary atmosphere evaporation that combines models for a hydrostatic lower atmosphere and a hydrodynamic upper atmosphere. We show that the initial rotation rate of the central star is of critical importance for the evolution of planetary atmospheres and can determine if a planet keeps or loses its primordial hydrogen envelope. Our results highlight the need for a detailed treatment of stellar activity evolution when studying the evolution of planetary atmospheres.

  7. Synchronized terrestrial-atmospheric deglacial records around the North Atlantic

    SciTech Connect

    Bjoerck, S.; Rasmussen, T.L.; Kromer, B.

    1996-11-15

    On the basis of synchronization of three carbon-14 ({sup 14}C)-dated lacustrine sequences from Sweden with tree ring and ice core records, the absolute age of the Younger Dryas-Preboreal climatic shift was determined to be 11,450 to 11,390 {plus_minus} 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising {Delta} {sup 14}C values, is evident in all records and indicates an ocean ventilation change. This cooling is similar to earlier deglacial coolings, and box-model calculations suggest that they all may have been the result of increased freshwater forcing that inhibited the strength of the North Atlantic heat conveyor, although the Younger Dryas may have been begun as an anomalous meltwater event. 53 refs., 8 figs., 1 tab.

  8. An impact-induced terrestrial atmosphere and iron-water reactions during accretion of the Earth

    NASA Technical Reports Server (NTRS)

    Lange, M. A.; Ahrens, T. J.

    1985-01-01

    Shock wave data and theoretical calculations were used to derive models of an impact-generated terrestrial atmosphere during accretion of the Earth. The models showed that impacts of infalling planetesimals not only provided the entire budget of terrestrial water but also led to a continuous depletion of near-surface layers of water-bearing minerals of their structural water. This resulted in a final atmospheric water reservoir comparable to the present day total water budget of the Earth. The interaction of metallic iron with free water at the surface of the accreting Earth is considered. We carried out model calcualtions simulating these processes during accretion. It is assumed that these processes are the prime source of the terrestrial FeO component of silicates and oxides. It is demonstrated that the iron-water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed. In order to obtain the necessary amount of terrestrial water, slightly heterogeneous accretion with initially 36 wt% iron planetesimals, as compared with a homogeneous value of 34 wt% is required.

  9. Late Impacts and the Origins of the Atmospheres on the Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, S.; Stewart, S. T.; Lock, S. J.; Parai, R.; Tucker, J. M.

    2014-12-01

    Models for the origin of terrestrial atmospheres typically require an intricate sequence of events, including hydrodynamic escape, outgassing of mantle volatiles and late delivery. Here we discuss the origin of the atmospheres on the terrestrial planets in light of new ideas about the formation of the Moon, giant impact induced atmospheric loss and recent noble gas measurements. Our new measurements indicate that noble gases in the Earth's atmosphere cannot be derived from any combination of fractionation of a nebular-derived atmosphere followed by outgassing of deep or shallow mantle volatiles. While Ne in the mantle retains a nebular component, the present-day atmosphere has no memory of nebular gases. Rather, atmospheric noble gases have a close affinity to chondrites. On the other hand, Venus's atmosphere has 20 and 70 times higher abundance of 20Ne and 36Ar, respectively, and a 20Ne/22Ne ratio closer to the solar value than Earth's atmosphere. While the present atmosphere of Mars is significantly fractionated in the lighter noble gases due to long term atmospheric escape, the Kr isotopic ratios in Martian atmosphere are identical to solar. Thus, while Earth's atmosphere has no memory of accretion of nebular gases, atmospheres on both Venus and Mars preserve at least a component of nebular gases. To explain the above observations, we propose that a common set of processes operated on the terrestrial planets, and that their subsequent evolutionary divergence is simply explained by planetary size and the stochastic nature of giant impacts. We present geochemical observations and simulations of giant impacts to show that most of Earth's mantle was degassed and the outgassed volatiles were largely lost during the final sequence of giant impacts onto Earth. Earth's noble gases were therefore dominantly derived from late-accreting planetesimals. In contrast, Venus did not suffer substantial atmospheric loss by a late giant impact and retains a higher abundance of both nebular and chondritic noble gases compared to Earth. Fast-accreting Mars has a noble gas signature inherited from the solar nebula, and its low mass allowed for gravitational escape of the volatile components in late accreting planetesimals due to vaporization upon impact.

  10. PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. II. H{sub 2}S AND SO{sub 2} PHOTOCHEMISTRY IN ANOXIC ATMOSPHERES

    SciTech Connect

    Hu Renyu; Seager, Sara; Bains, William

    2013-05-20

    Sulfur gases are common components in the volcanic and biological emission on Earth, and are expected to be important input gases for atmospheres on terrestrial exoplanets. We study the atmospheric composition and the spectra of terrestrial exoplanets with sulfur compounds (i.e., H{sub 2}S and SO{sub 2}) emitted from their surfaces. We use a comprehensive one-dimensional photochemistry model and radiative transfer model to investigate the sulfur chemistry in atmospheres ranging from reducing to oxidizing. The most important finding is that both H{sub 2}S and SO{sub 2} are chemically short-lived in virtually all types of atmospheres on terrestrial exoplanets, based on models of H{sub 2}, N{sub 2}, and CO{sub 2} atmospheres. This implies that direct detection of surface sulfur emission is unlikely, as their surface emission rates need to be extremely high (>1000 times Earth's volcanic sulfur emission) for these gases to build up to a detectable level. We also find that sulfur compounds emitted from the surface lead to photochemical formation of elemental sulfur and sulfuric acid in the atmosphere, which would condense to form aerosols if saturated. For terrestrial exoplanets in the habitable zone of Sun-like stars or M stars, Earth-like sulfur emission rates result in optically thick haze composed of elemental sulfur in reducing H{sub 2}-dominated atmospheres for a wide range of particle diameters (0.1-1 {mu}m), which is assumed as a free parameter in our simulations. In oxidized atmospheres composed of N{sub 2} and CO{sub 2}, optically thick haze, composed of elemental sulfur aerosols (S{sub 8}) or sulfuric acid aerosols (H{sub 2}SO{sub 4}), will form if the surface sulfur emission is two orders of magnitude more than the volcanic sulfur emission of Earth. Although direct detection of H{sub 2}S and SO{sub 2} by their spectral features is unlikely, their emission might be inferred by observing aerosol-related features in reflected light with future generation space telescopes.

  11. Mercury in terrestrial biomass and soils and factors determining atmospheric mercury sequestration

    NASA Astrophysics Data System (ADS)

    Obrist, D.; Johnson, D. W.; Lindberg, S.; Luo, Y.

    2008-12-01

    Terrestrial carbon (C) pools play an important role in uptake, deposition, sequestration, and emission of atmospheric mercury (Hg). The objective of this study is to assess atmospheric Hg sequestration associated with vegetation and soil C pools in forest ecosystems. As part of an ongoing EPA STAR project, we are systematically evaluating Hg pools and fluxes associated with terrestrial C pools in all major ecosystem compartments (i.e., leaves, branches, bole, litter, soils) across selected US forest ecosystems. Results from the first five sites located in the remote western United States show that the dominant above-ground pool of mercury is associated with surface litter with smaller pools associated with leaves and branches. Mass concentrations greatly increase in the following order: green leaves, dry leaves, initial litter, partially decomposed litter, humus. Based on detailed comparison of stochiometric relationships (e.g., Hg/C and Hg/N ratios) we conclude that these concentration increases are dominated by additional atmospheric deposition retained in the decomposing plant material while exposed to the environment rather than by organic C losses during decomposition. The large majority of total ecosystem mercury, up to 98 percent, however, is sequestered belowground in the soils. Soil Hg accumulation across all sites is greatly determined by the availability of organic matter in these systems, with soil C and soil N explaining more than 90 percent of the variability in observed soil Hg stocks. Our results suggest that the availability of soil organic matter is the main determinant for retention of atmospheric inputs in soils and hence in terrestrial ecosystems. Ecosystem structure and soil organic accumulation hence determine the resilience of Hg in terrestrial ecosystems with important implication for the stability and runoff of atmospheric Hg deposition to surrounding waterbodies.

  12. Time-Dependent Simulations of the Formation and Evolution of Disk-Accreted Atmospheres Around Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Stoekl, Alexander; Dorfi, Ernst

    2014-05-01

    In the early, embedded phase of evolution of terrestrial planets, the planetary core accumulates gas from the circumstellar disk into a planetary envelope. This atmosphere is very significant for the further thermal evolution of the planet by forming an insulation around the rocky core. The disk-captured envelope is also the staring point for the atmospheric evolution where the atmosphere is modified by outgassing from the planetary core and atmospheric mass loss once the planet is exposed to the radiation field of the host star. The final amount of persistent atmosphere around the evolved planet very much characterizes the planet and is a key criterion for habitability. The established way to study disk accumulated atmospheres are hydrostatic models, even though in many cases the assumption of stationarity is unlikely to be fulfilled. We present, for the first time, time-dependent radiation hydrodynamics simulations of the accumulation process and the interaction between the disk-nebula gas and the planetary core. The calculations were performed with the TAPIR-Code (short for The adaptive, implicit RHD-Code) in spherical symmetry solving the equations of hydrodynamics, gray radiative transport, and convective energy transport. The models range from the surface of the solid core up to the Hill radius where the planetary envelope merges into the surrounding protoplanetary disk. Our results show that the time-scale of gas capturing and atmospheric growth strongly depends on the mass of the solid core. The amount of atmosphere accumulated during the lifetime of the protoplanetary disk (typically a few Myr) varies accordingly with the mass of the planet. Thus, a core with Mars-mass will end up with about 10 bar of atmosphere while for an Earth-mass core, the surface pressure reaches several 1000 bar. Even larger planets with several Earth masses quickly capture massive envelopes which in turn become gravitationally unstable leading to runaway accretion and the eventual formation of a gas planet.

  13. Exploring the control of land-atmospheric oscillations over terrestrial vegetation productivity

    NASA Astrophysics Data System (ADS)

    Depoorter, Mathieu; Green, Julia; Gentine, Pierre; Liu, Yi; van Eck, Christel; Regnier, Pierre; Dorigo, Wouter; Verhoest, Niko; Miralles, Diego

    2015-04-01

    Vegetation dynamics play an important role in the climate system due to their control on the carbon, energy and water cycles. The spatiotemporal variability of vegetation is regulated by internal climate variability as well as natural and anthropogenic forcing mechanisms, including fires, land use, volcano eruptions or greenhouse gas emissions. Ocean-atmospheric oscillations, affect the fluxes of heat and water over continents, leading to anomalies in radiation, precipitation or temperature at widely separated locations (i.e. teleconnections); an effect of ocean-atmospheric oscillations on terrestrial primary productivity can therefore be expected. While different studies have shown the general importance of internal climate variability for global vegetation dynamics, the control by particular teleconnections over the regional growth and decay of vegetation is still poorly understood. At continental to global scales, satellite remote sensing offers a feasible approach to enhance our understanding of the main drivers of vegetation variability. Traditional studies of the multi-decadal variability of global vegetation have been usually based on the normalized difference vegetation index (NDVI) derived from the Advanced Very High Resolution Radiometer (AVHRR), which extends back to the early '80s. There are, however, some limitations to NDVI observations; arguably the most important of these limitations is that from the plant physiology perspective the index does not have a well-defined meaning, appearing poorly correlated to vegetation productivity. On the other hand, recently developed records from other remotely-sensed properties of vegetation, like fluorescence or microwave vegetation optical depth, have proven a significantly better correspondence to above-ground biomass. To enhance our understanding of the controls of ocean-atmosphere oscillations over vegetation, we propose to explore the link between climate oscillation extremes and net primary productivity over the last two decades. The co-variability of a range of climate oscillation indices and newly-derived records of fluorescence and vegetation optical depth is analyzed using a statistical framework based on correlations, bootstrapping and Empirical Orthogonal Functions (EOFs). Results will enable us to characterize regional hotspots where particular climatic oscillations control vegetation productivity, as well as allowing us to underpin the climatic variables behind this control.

  14. Preliminary experiment requirements document for Solar and Terrestrial Atmospheres Spectrometer (STAS)

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The principal scientific objective of the Solar and Terrestrial Atmospheres Spectrometer (STAS) project is the measurement of the absolute ultraviolet solar spectral irradiance with: (1) resolution of better than 15 mA, and (2) absolute irradiance uncertainty at the state of the art (less than or equal to 3%). High measurement accuracy coupled with high spectral resolution are necessary to identify the nature of the radiation, its variability, and to identify solar processes which may cause the changes. Solar radiation between 1200 and 3600 A dominates the photochemistry of the mesosphere and stratosphere. Some important minor species, such as NO, show very complex and fundamentally narrow structure in their photodestruction cross sections, especially in the region of the Schumann-Runge bands of O2. Understanding the photochemical processes in the terrestrial atmosphere requires knowledge of both the cross sections and of the solar spectrum with the highest possible resolution and accuracy.

  15. The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems.

    PubMed

    Kürschner, Wolfram M; Kvacek, Zlatko; Dilcher, David L

    2008-01-15

    The Miocene is characterized by a series of key climatic events that led to the founding of the late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments, and particularly the role of atmospheric CO2 as a forcing factor, are poorly understood. Here we present a CO2 record based on stomatal frequency data from multiple tree species. Our data show striking CO2 fluctuations of approximately 600-300 parts per million by volume (ppmv). Periods of low CO2 are contemporaneous with major glaciations, whereas elevated CO2 of 500 ppmv coincides with the climatic optimum in the Miocene. Our data point to a long-term coupling between atmospheric CO2 and climate. Major changes in Miocene terrestrial ecosystems, such as the expansion of grasslands and radiations among terrestrial herbivores such as horses, can be linked to these marked fluctuations in CO2. PMID:18174330

  16. Terrestrial biomarkers : a proxy for reconstructing the past history of atmospheric circulation and vegetation changes

    NASA Astrophysics Data System (ADS)

    Sicre, M.; Ezat, U.

    2006-12-01

    The Sea Air Exchange Program (SEAREX) has significantly contributed to the understanding of the long-range transport of aerosols, over distances of several thousand kilometers. Naturally occurring organic compounds (n-alkanes, fatty alcohols, long-chain n-aldehydes,...) of epicuticular waxes produced by terrestrial plant provide important background information on the source emission and atmospheric transport pathways of terrestrial carbon. Source identifications based on airborne biomarker distribution patterns during SEAREX experiment have shown to be consistent with the origin of the aerosols infered by isentropic air mass trajectories. More recent progress have been made from aerosol monitoring over several years, showing that leaf waxes are introduced into the atmosphere mainly by wind ablation off the living vegetation rather than from soil remobilization of detrital waxes during soil deflation. The ablated wax constituents would thus integrate the vegetation signature over large continental areas and might be applied to investigate vegetation changes at a regional scale. Few studies have shown that stratigraphic records of terrestrial biomarkers in hemi-pelagic and pelagic sediments remote from the continents, where pollen are lacking, can be useful tools to reconstruct the atmospheric circulation history and/or changes of the vegetation production.

  17. The molecular composition of impact-generated atmospheres on terrestrial planets during the post-accretion stage

    NASA Astrophysics Data System (ADS)

    Kuwahara, Hideharu; Sugita, Seiji

    2015-09-01

    Both geochemical measurements and theoretical calculations suggest that impact degassing from meteoritic materials after the completion of main phase of planetary accretion may have produced a large fraction of the early terrestrial atmospheres. However, the molecular compositions of such impact-generated atmospheres are not well constrained because the thermodynamic cooling path, which controls the chemical reactions in impact-induced vapor, has not been investigated extensively. In this study, we theoretically assess the chemical reactions within impact-induced vapor that cools adiabatically until the pressure equilibrates with the ambient atmosphere. The calculation results indicate that there are two primary controlling factors for the cooling path: impact entropy gain and atmospheric pressure. The former is mainly determined by both impact velocity and the presence/absence of an ocean. The degree of atmospheric effect depends on vapor plume size. For large impacts, atmospheric containment of vapor expansion is inefficient. However, the expansion of small vapor plumes is contained by the pre-existing atmosphere and their terminal molecular composition is controlled by this process. This is because whether a chemical reaction quenches during adiabatic cooling or during subsequent radiative cooling would depend on the cooling transition temperature, at which adiabatic expansion stops and radiative cooling takes over. For high atmospheric pressures and/or the vapor generated by high-velocity impacts, adiabatic expansion will cease at higher temperatures than typical quenching temperatures. Thus, the molecular composition of the vapor will not greatly depend on the impact velocity. The calculation results suggest that the molecular composition of the impact-induced vapor would vary widely (i.e., CH4/CO ratios) even if the compositions of the impactors are the same. More specifically, the impact-induced vapor generated by lower velocity impacts may be rich in CH4. Given average impact conditions on terrestrial planets, these calculation results further suggest that impact-generated atmospheres may have been rich in CH4 on Mars and an ocean-covered Earth and rich in H2 and CO on land-covered Venus and super Earths.

  18. Evaluation of atmospheric aerosol and tropospheric ozone effects on global terrestrial ecosystem carbon dynamics

    NASA Astrophysics Data System (ADS)

    Chen, Min

    The increasing human activities have produced large amounts of air pollutants ejected into the atmosphere, in which atmospheric aerosols and tropospheric ozone are considered to be especially important because of their negative impacts on human health and their impacts on global climate through either their direct radiative effect or indirect effect on land-atmosphere CO2 exchange. This dissertation dedicates to quantifying and evaluating the aerosol and tropospheric ozone effects on global terrestrial ecosystem dynamics using a modeling approach. An ecosystem model, the integrated Terrestrial Ecosystem Model (iTem), is developed to simulate biophysical and biogeochemical processes in terrestrial ecosystems. A two-broad-band atmospheric radiative transfer model together with the Moderate-Resolution Imaging Spectroradiometer (MODIS) measured atmospheric parameters are used to well estimate global downward solar radiation and the direct and diffuse components in comparison with observations. The atmospheric radiative transfer modeling framework were used to quantify the aerosol direct radiative effect, showing that aerosol loadings cause 18.7 and 12.8 W m -2 decrease of direct-beam Photosynthetic Active Radiation (PAR) and Near Infrared Radiation (NIR) respectively, and 5.2 and 4.4 W m -2 increase of diffuse PAR and NIR, respectively, leading to a total 21.9 W m-2 decrease of total downward solar radiation over the global land surface during the period of 2003-2010. The results also suggested that the aerosol effect may be overwhelmed by clouds because of the stronger extinction and scattering ability of clouds. Applications of the iTem with solar radiation data and with or without considering the aerosol loadings shows that aerosol loading enhances the terrestrial productions [Gross Primary Production (GPP), Net Primary Production (NPP) and Net Ecosystem Production (NEP)] and carbon emissions through plant respiration (RA) in global terrestrial ecosystems over the period of 2003-2010. Ecosystem heterotrophic respiration (RH) was negatively affected by the aerosol loading. These results support previous conclusions of the advantage of aerosol light scattering effect on plant productions in other studies but suggest there is strong spatial variation. This study finds indirect aerosol effects on terrestrial ecosystem carbon dynamics through affecting plant phenology, thermal and hydrological environments. All these evidences suggested that the aerosol direct radiative effect on global terrestrial ecosystem carbon dynamics should be considered to better understand the global carbon cycle and climate change. An ozone sub-model is developed in this dissertation and fully coupled with iTem. The coupled model, named iTemO3 considers the processes of ozone stomatal deposition, plant defense to ozone influx, ozone damage and plant repairing mechanism. By using a global atmospheric chemical transport model (GACTM) estimated ground-level ozone concentration data, the model estimated global annual stomatal ozone deposition is 234.0 Tg O3 yr-1 and indicates which regions have high ozone damage risk. Different plant functional types, sunlit and shaded leaves are shown to have different responses to ozone. The model predictions suggest that ozone has caused considerable change on global terrestrial ecosystem carbon storage and carbon exchanges over the study period 2004-2008. The study suggests that uncertainty of the key parameters in iTemO3 could result in large errors in model predictions. Thus more experimental data for better model parameterization is highly needed.

  19. XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part I: Atmospheric Expansion and Thermal Escape

    PubMed Central

    Lammer, Helmut; Odert, Petra; Kulikov, Yuri N.; Kislyakova, Kristina G.; Khodachenko, Maxim L.; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-01-01

    Abstract The recently discovered low-density “super-Earths” Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H2O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 REarth and a mass of 10 MEarth. We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1011–1029. PMID:24251443

  20. Historical space psychology: Early terrestrial explorations as Mars analogues

    NASA Astrophysics Data System (ADS)

    Suedfeld, Peter

    2010-03-01

    The simulation and analogue environments used by psychologists to circumvent the difficulties of conducting research in space lack many of the unique characteristics of future explorations, especially the mission to Mars. This paper suggests that appropriate additional analogues would be the multi-year maritime and terrestrial explorations that mapped the surface of the Earth in previous centuries. These, like Mars, often involved a hazardous trek through unknown territory, flanked by extended, dangerous voyages to and from the exploration sites. Characteristic issues included interpersonal relationships under prolonged stress, stretches of boredom interspersed with intense work demands, the impossibility of rescue, resupply, or other help from home, chronic danger, physical discomfort and lack of privacy, and the crucial role of the leader. Illustrative examples of one important factor, leadership style, are discussed. The examination of such expeditions can help to identify the psychological stressors that are likely to be experienced by Mars explorers, and can also indicate countermeasures to reduce the damaging impact of those stressors.

  1. Wind enhanced planetary escape - Collisional modifications. [thermal escape of terrestrial H and He from atmosphere

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Hartle, R. E.

    1977-01-01

    Effects of collisions and finite winds characteristic of a highly perturbed atmosphere on the thermal escape of terrestrial hydrogen and helium are investigated using a Monte Carlo approach. The limiting cases of vertical and horizontal winds are considered, and the relaxation layer between the collisionless exosphere and the collision-dominated thermosphere is modeled as a plane-parallel slab of given column density, depth, and atmospheric density. For both gases, the upwardly injected flux at the base of the relaxation layer is compared with the returning downward flux distribution at the same location; the technique is also applied to the atmosphere of Titan. The results show that inclusion of collisions in the escape model for terrestrial hydrogen with winds effectively throttles the escape process, that collisional throttling is negligible for helium when the exobase temperature is at least 5000 K, and that the escape of a planetary-atmosphere constituent depends on the ratio of its gravitational and kinetic energies as well as on the ratio of its mass to that of the background gas.

  2. Nitrogen fixation on early Mars and other terrestrial planets: experimental demonstration of abiotic fixation reactions to nitrite and nitrate.

    PubMed

    Summers, David P; Khare, Bishun

    2007-04-01

    Understanding the abiotic fixation of nitrogen is critical to understanding planetary evolution and the potential origin of life on terrestrial planets. Nitrogen, an essential biochemical element, is certainly necessary for life as we know it to arise. The loss of atmospheric nitrogen can result in an incapacity to sustain liquid water and impact planetary habitability and hydrological processes that shape the surface. However, our current understanding of how such fixation may occur is almost entirely theoretical. This work experimentally examines the chemistry, in both gas and aqueous phases, that would occur from the formation of NO and CO by the shock heating of a model carbon dioxide/nitrogen atmosphere such as is currently thought to exist on early terrestrial planets. The results show that two pathways exist for the abiotic fixation of nitrogen from the atmosphere into the crust: one via HNO and another via NO(2). Fixation via HNO, which requires liquid water, could represent fixation on a planet with liquid water (and hence would also be a source of nitrogen for the origin of life). The pathway via NO(2) does not require liquid water and shows that fixation could occur even when liquid water has been lost from a planet's surface (for example, continuing to remove nitrogen through NO(2) reaction with ice, adsorbed water, etc.). PMID:17480164

  3. Atmospheric Dispersal of Bioactive Streptomyces albidoflavus Strains Among Terrestrial and Marine Environments.

    PubMed

    Sarmiento-Vizcaíno, Aida; Braña, Alfredo F; González, Verónica; Nava, Herminio; Molina, Axayacatl; Llera, Eva; Fiedler, Hans-Peter; Rico, José M; García-Flórez, Lucía; Acuña, José L; García, Luis A; Blanco, Gloria

    2016-02-01

    Members of the Streptomyces albidoflavus clade, identified by 16S rRNA sequencing and phylogenetic analyses, are widespread among predominant terrestrial lichens (Flavoparmelia caperata and Xanthoria parietina) and diverse intertidal and subtidal marine macroalgae, brown red and green (Phylum Heterokontophyta, Rhodophyta, and Chlorophyta) from the Cantabrian Cornice. In addition to these terrestrial and coastal temperate habitats, similar strains were also found to colonize deep-sea ecosystems and were isolated mainly from gorgonian and solitary corals and other invertebrates (Phylum Cnidaria, Annelida, Echinodermata, Arthropoda, and Porifera) living up to 4700-m depth and at a temperature of 2-4 °C in the submarine Avilés Canyon. Similar strains have been also repeatedly isolated from atmospheric precipitations (rain drops, snow, and hailstone) collected in the same area throughout a year observation time. These ubiquitous strains were found to be halotolerant, psychrotolerant, and barotolerant. Bioactive compounds with diverse antibiotic and cytotoxic activities produced by these strains were identified by high-performance liquid chromatography (HPLC) and database comparison. These include antibacterials (paulomycins A and B), antifungals (maltophilins), antifungals displaying also cytotoxic activities (antimycins and 6-epialteramides), and the antitumor compound fredericamycin. A hypothetical dispersion model is here proposed to explain the biogeographical distribution of S. albidoflavus strains in terrestrial, marine, and atmospheric environments. PMID:26224165

  4. A terrestrial Eocene stack: tying terrestrial lake ecology to marine carbon cycling through the Early Eocene Climatic Optimum

    NASA Astrophysics Data System (ADS)

    Grogan, D. S.; Whiteside, J. H.; Musher, D.; Rosengard, S. Z.; Vankeuren, M. A.; Pancost, R. D.

    2010-12-01

    The lacustrine Green River Formation is known to span ≥15 million years through the early-middle Eocene, and recent work on radioisotopic dating has provided a framework on which to build ties to the orbitally-tuned marine Eocene record. Here we present a spliced stack of Fischer assay data from drilled cores of the Green River Formation that span both an East-West and a North-South transect of the Uinta Basin of Utah. Detailed work on two cores demonstrate that Fischer assay measurements covary with total organic carbon and bulk carbon isotopes, allowing us to use Fisher assay results as a representative carbon cycling proxy throughout the stack. We provide an age model for this core record by combining radioisotopic dates of tuff layers with frequency analysis of Fischer assay measurements. Identification of orbital frequencies tied directly to magnetochrons through radioisotopic dates allows for a direct comparison of the terrestrial to the marine Eocene record. Our analysis indicates that the marker beds used to correlate the stack cores represent periods of enhanced lake productivity and extreme carbon burial; however, unlike the hyperthermal events that are clearly marked in the marine Eocene record, the hydrocarbon-rich "Mahogany Bed" period of burial does not correspond to a clear carbon isotope excursion. This suggests that the terrestrial realm may have experienced extreme ecological responses to relatively small perturbations in the carbon cycle during the Early Eocene Climatic Optimum. To investigate the ecological responses to carbon cycle perturbations through the hydrocarbon rich beds, we analyzed a suite of microbial biomarkers, finding evidence for cyanobacteria, dinoflagellates, and potentially green sulfur bacteria. These taxa indicate fluctuating oxic/anoxic conditions in the lake during abrupt intervals of carbon burial, suggesting a lake biogeochemical regime with no modern analogues.

  5. Trophic network models explain instability of Early Triassic terrestrial communities.

    PubMed

    Roopnarine, Peter D; Angielczyk, Kenneth D; Wang, Steve C; Hertog, Rachel

    2007-09-01

    Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction. PMID:17609191

  6. Venus as illustration of the importance of atmospheric evolution when modeling terrestrial planets and their surface conditions

    NASA Astrophysics Data System (ADS)

    Gillmann, C.; Tackley, P. J.; Golabek, G.

    2012-12-01

    The best way we can study what determines habitability is by comparing the one planet we know shelters life to other bodies. As extrasolar super-Earths will be found, we'll have access to more planetary samples, starting with their atmosphere. Taking our solar system as pattern, CO2 atmospheres might be common. Therefore, we use Venus to test our numerical modeling of the evolution of the atmosphere of terrestrial planets, as an intermediary between life-sustaining Earth and yet to be discovered exoplanets. We propose to investigate the evolution of the atmosphere and surface conditions on Venus. Here, we focus on mechanisms that deplete or replenish the atmosphere: volcanic degassing and atmospheric escape. These processes are linked together to obtain a coupled model, using retroaction of the atmosphere on the mantle. We study potential divergent evolutions this could cause. Two aspects of the atmospheric escape are taken into account. During early evolution, hydrodynamic escape is dominant. We use a model developed to take into account the linked escape of Hydrogen and Oxygen (Gillmann et al., 2009). A significant portion of the early atmosphere can be removed this way. For later evolution, we focus on non-thermal escape, as observed by the ASPERA instrument and modeled in various recent numerical studies. Post 4 Ga escape is low. Water escapes moderately, while we are not able to detect the present-day escape of CO2. The atmosphere is replenished by volcanic degassing, bringing volatiles from the mantle to the surface. Volcanic activity is obtained by adapting the highly advanced StagYY mantle dynamics model (Tackley, 2008) for Venus. Volatile fluxes are estimated for different mantle compositions and partitioning ratios. Surface conditions are estimated by tracking the amount of CO2 and water in the atmosphere and computing the surface temperature with a gray radiative-convective atmosphere model. These surface conditions in turn act as a boundary condition for the mantle dynamic model and have an influence on convection, volcanism and subsequent degassing. Our results show that we are able to obtain a Venus-like behavior for the solid planet, with resurfacing events which constitute an efficient way of losing Venus' internal heat. The atmosphere shows several interesting features. We are able to create evolution leading to present conditions. CO2 pressure seems unlikely to vary much over the history of the planet, only slightly increasing due to degassing. A late build-up of the atmosphere with several resurfacing events seems unlikely. On the other hand, water pressure is strongly sensitive to volcanic activity and varies rapidly. This leads to variations in surface temperatures of up to 200K, which have been identified to have an effect on volcanic activity. While a positive feedback (increasing atmosphere temperature leading to increasing mantle temperatures and melting) is not immediately apparent, we observe a clear link between temperature changes and volcanic spikes, in particular a strong correlation between large temperature drops and increased volcanism. Mobilization of the upper layers occurs, which imply that our coupling is not complete without taking into account rehydratation of the mantle. This depends on the surface alteration processes and could have important effects.

  7. Buildup of Abiotic Oxygen and Ozone in Atmospheres of Temperate Terrestrial Exoplanets

    NASA Astrophysics Data System (ADS)

    Kleinboehl, Armin; Willacy, Karen; Friedson, Andrew James; Swain, Mark R.

    2015-12-01

    The last two decades have seen a rapid increase in the detection and characterization of exoplanets. A focus of future missions will be on the subset of transiting, terrestrial, temperate exoplanets as they are the strongest candidates to harbor life as we know it.An important bioindicator for life as we know it is the existence of significant amounts of oxygen, and its photochemical byproduct ozone, in the exoplanet’s atmosphere. However, abiotic processes also produce oxygen and ozone, and the amount of oxygen abiotically produced in an atmosphere will largely depend on other atmospheric parameters. Constraining this parameter space will be essential to avoid ‘false positive’ detections of life, that is the interpretation of oxygen or ozone as a bioindicator despite being produced abiotically.Based on 1D radiative-convective model calculations, Wordsworth and Pierrehumbert (ApJL, 2014) recently pointed out that the formation and buildup of abiotic oxygen on water-rich planets largely depends on the amount of non-condensable gases in the atmosphere. The amount of non-condensable gases determines whether an atmosphere will develop a 'cold-trap' (similar to the tropopause on Earth) that contains most of the water in the lower atmosphere and dries out the upper atmosphere. If water vapor is a major constituent of the atmosphere, this cold-trapping is inhibited, leading to a much moister upper atmosphere. Water vapor in the upper atmosphere is photolyzed due to the availability of hard UV radiation, yielding oxygen.We use a photochemical model coupled to a 1D radiative-convective climate model to self-consistently study this effect in atmospheres with N2, CO2 and H2O as the main constituents. These are typical constituents for secondary, oxidized atmospheres, and they can exist in a wide range of ratios. We calculate the amounts of abiotically produced oxygen and ozone and determine the vertical structure of temperature and constituent mixing ratios for various input parameters. We use a radiative transfer model to study the spectroscopic fingerprint of these atmospheres in transit observations with a focus on the capabilities of the James Webb Space Telescope. We compare these results to spectra of Earth as it would be seen as an exoplanet.

  8. Modeling the terrestrial hydrology for the global atmosphere - The future role of satellite data

    NASA Technical Reports Server (NTRS)

    Lin, J. D.; Bock, P.; Alfano, J. J.

    1981-01-01

    A global terrestrial hydrology model has been developed for the transport and storage of moisture and heat in the ground surface layer where the hydrological parameters react to diurnal and seasonal changes in the atmosphere. The spatial and temporal variability of land surface features is considered in the model by means of large scale parameterizations. The model can be either forced by the atmosphere using conventional meteorological data or coupled to an atmospheric general circulation model (GCM) for interactive studies. The global surface is divided into 4 deg longitude by 5 deg latitude cells while the ground is represented by a thin surface layer, a bulk layer (the root zone), and a deep layer (the ground water zone). Results are presented from a seven-day global experiment which was conducted utilizing the GLAS GCM (NASA Goddard Laboratory for Atmospheric Sciences). The model has demonstrated its capability to predict, over a large region, the overall soil moisture storage and major flux exchanges with the atmosphere above and the ground water below.

  9. The Heat-Pipe Hypothesis for Early Crustal Development of Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Webb, A. G.; Moore, W. B.; Simon, J. I.

    2014-12-01

    Crusts of the terrestrial planets other than Earth are dominated by mafic / ultramafic volcanics, with some contractional tectonics and minor extension. This description may also fit the early Earth. Therefore, a single process may have controlled early crustal development. Here we explore the hypothesis that heat-pipe cooling mode dominates early phases of terrestrial planet evolution. Volcanism is the hallmark of heat-pipe cooling: hot magma moves through the lithosphere in narrow channels, then is deposited and cools at the surface. A heat-pipe planet develops a thick, cold, downward-advecting lithosphere dominated by mafic/ultra-mafic flows. Contractional deformation occurs throughout the lithosphere as the surface is buried and forced toward smaller radii. Geologies of the Solar system's terrestrial planets are consistent with early heat-pipe cooling. Mercury's surface evolution is dominated by low-viscosity volcanism until ~4.1-4.0 Ga, with little activity other than global contraction since. Similar, younger features at Venus are commonly interpreted in terms of catastrophic resurfacing events with ~0.5 billion-year periodicity, but early support of high topography suggests a transition from heat-pipe to rigid-lid tectonics. Thick heat-pipe lithosphere may preserve the crustal dichotomy between Mars' northern and southern hemispheres, and explain the range in trace element abundances and isotopic compositions of Martian meteorites. At the Moon, global serial volcanism can explain refinement of ferroan anorthite rich rocks and coeval production of the "Mg-suite" rocks. The Moon's shape is out of hydrostatic equilibrium; it may represent a fossil preserved by thick early lithosphere. Active development of Jupiter's moon Io, which is warmed by tidal heating, is widely interpreted in terms of heat-pipe cooling. Given its potential ubiquity in the Solar system, heat-pipe cooling may be a universal process experienced by all terrestrial bodies of sufficient size.

  10. Ice clathrate as a possible source of the atmospheres of the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Sill, G. T.; Wilkening, L. L.

    1978-01-01

    The presence and compositions of atmospheres on the terrestrial planets do not follow directly from condensation models which would have earth accreting near 500 K. No single mechanism yet proposed adequately accounts for the abundances of noble gases and carbon and nitrogen in the atmospheres. We show that the composition of clathrates forming at low temperatures in cold regions of the nebula can be predicted. Addition of about 1 ppm clathrate material to the earth can explain observed abundances of Ar, Kr, and Xe. Condensation and adsorption processes occurring at 400-500 K are necessary to explain the observed abundances of Ne, H2O, C, and N. Possible sources of clathrates could be cometary bodies formed in the outer solar system.

  11. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars.

    PubMed

    Shaheen, R; Abramian, A; Horn, J; Dominguez, G; Sullivan, R; Thiemens, Mark H

    2010-11-23

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess (17)O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O(3) reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  12. Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

    PubMed Central

    Shaheen, R.; Abramian, A.; Horn, J.; Dominguez, G.; Sullivan, R.; Thiemens, Mark H.

    2010-01-01

    The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4–3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth. PMID:21059939

  13. Variation of Atmospheric Oxygen in the Phanerozoic Recorded By δ13c of Terrestrial Organic Matter

    NASA Astrophysics Data System (ADS)

    Muehlenbachs, K.; Tappert, R.; McKellar, R. C.; Wolfe, A. P.; Tappert, M.; Schoell, M.

    2014-12-01

    One important factor controlling the δ13C of C3 plants is pO2 and thus δ13C of fossil terrestrial organic matter is a proxy for ancient pO2 once variations of δ13C of the atmosphere and paleo pCO2 are corrected for. We reconstructed pO2 since the emergence of land plants in the Ordovician following the approach of Tappert et al. [1], and using the published δ13C record of fossil resins (amber), coals and dispersed terrestrial organic matter. For most of this time, atmospheric pO2 was considerably lower (pO2 ~ 10-21%) compared to today (pO2 = 21%). Secular variations in pO2 must reflect changing amounts of burial of organic matter and sulfides. We observe a strong correlation between pO2 calculated from land plants, and the strontium and lithium isotopic compositions of marine carbonates. The marine Sr isotope record reflects secular changes of continental weathering and climate driven by tectonic activity. Synchronicity of pO2 with the marine strontium isotope record implies that tectonic processes, including orogeneses and the formation of associated sedimentary basins, not only control the rate of weathering and volume of sedimentation, but also the amount and proportion of the biomass that is buried on geological timescales.

  14. The terrestrial biosphere as a net source of greenhouse gases to the atmosphere.

    PubMed

    Tian, Hanqin; Lu, Chaoqun; Ciais, Philippe; Michalak, Anna M; Canadell, Josep G; Saikawa, Eri; Huntzinger, Deborah N; Gurney, Kevin R; Sitch, Stephen; Zhang, Bowen; Yang, Jia; Bousquet, Philippe; Bruhwiler, Lori; Chen, Guangsheng; Dlugokencky, Edward; Friedlingstein, Pierre; Melillo, Jerry; Pan, Shufen; Poulter, Benjamin; Prinn, Ronald; Saunois, Marielle; Schwalm, Christopher R; Wofsy, Steven C

    2016-03-10

    The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate. Anthropogenic activities such as land-use change, agriculture and waste management have altered terrestrial biogenic greenhouse gas fluxes, and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate change. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively, but the net biogenic greenhouse gas balance resulting from anthropogenic activities and its effect on the climate system remains uncertain. Here we use bottom-up (inventory, statistical extrapolation of local flux measurements, and process-based modelling) and top-down (atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981 and 2010 resulting from anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic methane and nitrous oxide emissions is a factor of about two larger than the cooling effect resulting from the global land carbon dioxide uptake from 2001 to 2010. This results in a net positive cumulative impact of the three greenhouse gases on the planetary energy budget, with a best estimate (in petagrams of CO2 equivalent per year) of 3.9 ± 3.8 (top down) and 5.4 ± 4.8 (bottom up) based on the GWP100 metric (global warming potential on a 100-year time horizon). Our findings suggest that a reduction in agricultural methane and nitrous oxide emissions, particularly in Southern Asia, may help mitigate climate change. PMID:26961656

  15. The terrestrial biosphere as a net source of greenhouse gases to the atmosphere

    NASA Astrophysics Data System (ADS)

    Tian, Hanqin; Lu, Chaoqun; Ciais, Philippe; Michalak, Anna M.; Canadell, Josep G.; Saikawa, Eri; Huntzinger, Deborah N.; Gurney, Kevin R.; Sitch, Stephen; Zhang, Bowen; Yang, Jia; Bousquet, Philippe; Bruhwiler, Lori; Chen, Guangsheng; Dlugokencky, Edward; Friedlingstein, Pierre; Melillo, Jerry; Pan, Shufen; Poulter, Benjamin; Prinn, Ronald; Saunois, Marielle; Schwalm, Christopher R.; Wofsy, Steven C.

    2016-03-01

    The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate. Anthropogenic activities such as land-use change, agriculture and waste management have altered terrestrial biogenic greenhouse gas fluxes, and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate change. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively, but the net biogenic greenhouse gas balance resulting from anthropogenic activities and its effect on the climate system remains uncertain. Here we use bottom-up (inventory, statistical extrapolation of local flux measurements, and process-based modelling) and top-down (atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981 and 2010 resulting from anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic methane and nitrous oxide emissions is a factor of about two larger than the cooling effect resulting from the global land carbon dioxide uptake from 2001 to 2010. This results in a net positive cumulative impact of the three greenhouse gases on the planetary energy budget, with a best estimate (in petagrams of CO2 equivalent per year) of 3.9 ± 3.8 (top down) and 5.4 ± 4.8 (bottom up) based on the GWP100 metric (global warming potential on a 100-year time horizon). Our findings suggest that a reduction in agricultural methane and nitrous oxide emissions, particularly in Southern Asia, may help mitigate climate change.

  16. Stability of CO2 Atmospheres on Terrestrial Exoplanets in the Proximity of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Gao, P.; Hu, R.; Yung, Y. L.

    2013-12-01

    M dwarfs are promising targets for the search and characterization of terrestrial exoplanets that might be habitable, as the habitable planets around M dwarfs are in much more close-in orbits compared to their counterparts around Sun-like stars. CO2, one of the most important greenhouse gases on our planet, is conventionally adopted as a major greenhouse gas in studying the habitability of terrestrial exoplanets around M dwarfs. However, the stability of CO2 in terrestrial atmospheres has been called into question due to the high FUV/NUV flux ratio of some M dwarfs in comparison to that of Sun-like stars. While CO2 is photolyzed into CO and O by photons in the FUV, with O2 forming from the O atoms through third body catalytic reactions, NUV photons are able to photolyze water, producing HOx radicals which go on to catalytically recombine the relatively stable CO and O2 molecules back into CO2. The comparatively low NUV flux of some M dwarfs leads to a significantly reduced efficiency of catalytic recombination of CO and O2 and the possible net destruction of CO2 and the build up of CO and O2. In this work we test the above hypothesis using a 1D photochemical kinetics model for a Mars-sized planet with an initial atmospheric composition similar to that of Mars and the incoming stellar flux of a weakly active M dwarf, assuming the exoplanet is 0.1 AU away from its parent star, in proximity of its habitable zone. We show that a CO2-dominated atmosphere can be converted into a CO2/CO/O2-dominated atmosphere in 10^3-10^4 years by CO2 photolysis. This process is kept from running away by a combination of O2 photolysis, three body reactions of O, O2, and another species to form O3, and reactions of CO with OH to form CO2 and H. However, such a large amount of O2 and CO, combined with some amount of H and H2, may be susceptible to spontaneous combustion or detonation, and thus could prove to be an especially unstable state in itself. Thus there could arise a situation whereby a CO2 atmosphere dissociating into CO and O2 would be periodically and violently converted back into mostly CO2 due to some "spark". Our simulation results suggest that it is unlikely that CO2 atmospheres can remain stable on terrestrial planets around M dwarfs with high FUV/NUV flux ratios unless it is extremely quiescent. Furthermore, any detection of O2 and O3 in such atmospheres is far more likely to be due to photochemical processes rather than as a result of biology.

  17. Sulfur Chemistry in the Early and Present Atmosphere of Mars

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.; Summers, M. E.

    2011-01-01

    Atmospheric sulfur species resulting from volcanic emissions impact the composition and chemistry of the atmosphere, impact the climate, and hence, the habitability of Mars and impact the mineralogy and composition of the surface of Mars. The geochemical/ photochemical cycling of sulfur species between the interior (via volcanism), the atmosphere (atmospheric photochemical and chemical processes) and the deposition of sulfuric acid on the surface of Mars is an important, but as yet poorly understood geochemical/ photochemical cycle on Mars. There is no observational evidence to indicate that Mars is volcanically active at the present time, however, there is strong evidence that volcanism was an important and widespread process on early Mars. The chemistry and photochemistry of sulfur species in the early and present atmosphere of Mars will be assessed using a one-dimensional photochemical model. Since it is generally assumed that the atmosphere of early Mars was significantly denser than the present 6-millibar atmosphere, photochemical calculations were performed for the present atmosphere and for the atmosphere of early Mars with assumed surface pressures of 60 and 350-millibars, where higher surface pressure resulted from enhanced atmospheric concentrations of carbon dioxide (CO2). The following sections include the results of earlier modeling studies, a summary of the one-dimensional photochemical model used in this study, a summary of the photochemistry and chemistry of sulfur species in the atmosphere of Mars and some of the results of the calculations.

  18. CO2 greenhouse in the early martian atmosphere: SO2 inhibits condensation

    NASA Technical Reports Server (NTRS)

    Yung, Y. L.; Nair, H.; Gerstell, M. F.

    1997-01-01

    Many investigators of the early martian climate have suggested that a dense carbon dioxide atmosphere was present and warmed the surface above the melting point of water (J.B. Pollack, J.F. Kasting, S.M. Richardson, and K. Poliakoff 1987. Icarus 71, 203-224). However, J.F. Kasting (1991. Icarus 94, 1-13) pointed out that previous thermal models of the primitive martian atmosphere had not considered the condensation of CO2. When this effect was incorporated, Kasting found that CO2 by itself is inadequate to warm the surface. SO2 absorbs strongly in the near UV region of the solar spectrum. While a small amount of SO2 may have a negligible effect by itself on the surface temperature, it may have significantly warmed the middle atmosphere of early Mars, much as ozone warms the terrestrial stratosphere today. If this region is kept warm enough to inhibit the condensation of CO2, then CO2 remains a viable greenhouse gas. Our preliminary radiative modeling shows that the addition of 0.1 ppmv of SO2 in a 2 bar CO2 atmosphere raises the temperature of the middle atmosphere by approximately 10 degrees, so that the upper atmosphere in a 1 D model remains above the condensation temperature of CO2. In addition, this amount of SO2 in the atmosphere provides an effective UV shield for a hypothetical biosphere on the martian surface.

  19. The Upper Valanginian (Early Cretaceous) positive carbon-isotope event recorded in terrestrial plants [rapid communication

    NASA Astrophysics Data System (ADS)

    Gröcke, Darren R.; Price, Gregory D.; Robinson, Stuart A.; Baraboshkin, Evgenij Y.; Mutterlose, Jörg; Ruffell, Alastair H.

    2005-12-01

    Our understanding of the ancient ocean-atmosphere system has focused on oceanic proxies. However, the study of terrestrial proxies is equally necessary to constrain our understanding of ancient climates and linkages between the terrestrial and oceanic carbon reservoirs. We have analyzed carbon-isotope ratios from fossil plant material through the Valanginian and Lower Hauterivian from a shallow-marine, ammonite-constrained succession in the Crimean Peninsula of the southern Ukraine in order to determine if the Upper Valanginian positive carbon-isotope excursion is expressed in the atmosphere. δ13C plant values fluctuate around - 23‰ to - 22‰ for the Valanginian-Hauterivian, except during the Upper Valanginian where δ13C plant values record a positive excursion to ˜- 18‰. Based upon ammonite biostratigraphy from Crimea, and in conjunction with a composite Tethyan marine δ13C carb curve, several conclusions can be drawn: (1) the δ13C plant record indicates that the atmospheric carbon reservoir was affected; (2) the defined ammonite correlations between Europe and Crimea are synchronous; and (3) a change in photosynthetic carbon-isotope fractionation, caused by a decrease in atmospheric pCO 2, occurred during the Upper Valanginian positive δ13C excursion. Our new data, combined with other paleoenvironmental and paleoclimatic information, indicate that the Upper Valanginian was a cool period (icehouse) and highlights that the Cretaceous period was interrupted by periods of cooling and was not an equable climate as previously thought.

  20. Terrestrial microorganisms at an altitude of 20,000 m in Earth's atmosphere

    USGS Publications Warehouse

    Griffin, Dale W.

    2004-01-01

    A joint effort between the U.S. Geological Survey's (USGS) Global Desert Dust and NASA's Stratospheric and Cosmic Dust Programs identified culturable microbes from an air sample collected at an altitude of 20,000 m. A total of 4 fungal (Penicillium sp.) and 71 bacteria colonyforming units (70 colonies of Bacillus luciferensis believed to have originated from a single cell collected at altitude and one colony of Bacillus sphaericus) were enumerated, isolated and identified using a morphological key and 16S rDNA sequencing respectively. All of the isolates identified were sporeforming pigmented fungi or bacteria of terrestrial origin and demonstrate that the presence of viable microorganisms in Earth's upper atmosphere may not be uncommon.

  1. Solar wind and terrestrial atmosphere effects on lunar sample surface composition

    NASA Technical Reports Server (NTRS)

    Cadenhead, D. A.; Jones, B. R.; Buergel, W. G.; Stetter, J. R.

    1973-01-01

    Samples returned from the Apollo missions have been shown to have undergone a partial surface oxidation with the degree of oxidation being dependent on the intensity and duration of exposure to a terrestrial or other oxidizing atmosphere. Exposure to atomic hydrogen at room temperature, or molecular hydrogen above 100 C results in a surface reduction. The adsorption of water vapor on a test sample was found to be only slightly dependent on the state of surface oxidation, a situation consistent with the formation of hydroxyl groups on the surface when a sample is exposed to hydrogen. That hydroxyl groups are indeed formed is substantiated by the release of water vapor (and by release of heavy water following exposure to deuterium), indicating that water vapor can be synthesized from solar wind hydrogen and sample oxygen. Observations of trace amounts of methane indicate that the reduction process is by no means restricted to the formation of water vapor.

  2. Climate change and coupling of macronutrient cycles along the atmospheric, terrestrial, freshwater and estuarine continuum.

    TOXLINE Toxicology Bibliographic Information

    Jarvie HP; Jickells TD; Skeffington RA; Withers PJ

    2012-09-15

    This paper provides an introduction to the Special Issue on "Climate Change and Coupling of Macronutrient Cycles along the Atmospheric, Terrestrial, Freshwater and Estuarine Continuum", dedicated to Colin Neal on his retirement. It is not intended to be a review of this vast subject, but an attempt to synthesize some of the major findings from the 22 contributions to the Special Issue in the context of what is already known. The major research challenges involved in understanding coupled macronutrient cycles in these environmental media are highlighted, and the difficulties of making credible predictions of the effects of climate change are discussed. Of particular concern is the possibility of interactions which will enhance greenhouse gas concentrations and provide positive feedback to global warming.

  3. Understanding the early Mesozoic world: New geochronological data from terrestrial and marine strata

    NASA Astrophysics Data System (ADS)

    Mundil, Roland; Irmis, Randall B.; Ickert, Ryan B.

    2013-04-01

    The first ~50 Ma of the Mesozoic (the Triassic Period) are marked by two major mass extinctions at the end-Permian and end-Triassic, extensive flood volcanic events (the Siberian Traps and the Central Atlantic Magmatic Province), perturbations of the ocean chemistry, paleoenvironmental changes in a greenhouse world and the origin of modern terrestrial ecosystems. Marine records of events leading to the end-Permian extinction as well as subsequent recovery during the Early and Middle Triassic are now well understood in terms of their relative and absolute timing, mainly due to significant advances in both the quantity and quality of geochronological data. This includes a detailed understanding of the Middle and end-Permian extinction events and their potential causes, their aftermath, and also the timing of large scale perturbations of the global carbon cycle in the Early Triassic. For the remaining ~30 Ma of the Triassic, however, there was until recently virtually no chronostratigraphic framework, and hence there is a major lag in our understanding of major events such as the origin and early diversification of dinosaurs, major reef building episodes in marine ecosystems, paleoenvironmental changes (e.g., the Carnian Pluvial Event), and a large extraterrestrial bolide impact (the Manicouagan impact). In absence of high-resolution radioisotopic ages, assumptions about causal inference and the role of these events, remain poorly constrained. We have therefore started to build a chronostratigraphic framework by applying U-Pb CA-TIMS analyses to zircon from primary and redeposited volcanic strata within both marine and terrestrial sequences of Late Triassic age. In particular, the potential of geochronological techniques applied to redeposited volcanic layers has long been ignored because the time lag between zircon crystallization and deposition is unknown; however, our initial results calibrating terrestrial sequences in North and South America are very promising and many of the obtained maximum ages are in agreement with stratigraphic order. Our new marine ages support the hypothesis of a long Norian Stage (~20 Ma), and new data suggest a wholly Norian age for the fossiliferous terrestrial Chinle Formation in the southwestern US. Thus, previous correlations based on terrestrial biostratigraphy with deposits in South American sequences are now thought to be flawed, suggesting that the rise of dinosaurs was diachronous, and occurred later in North America than in South America. Further complementary geochronological analyses from marine sequences are currently underway and are aimed at correlating and understanding key events and processes that are recorded both marine and terrestrial sedimentary archives of Late Triassic age.

  4. Exploring the Sensitivity of Terrestrial Ecosystems and Atmospheric Exchange of CO2 to Global Environmental Factors

    NASA Astrophysics Data System (ADS)

    Jain, A. K.; Meiyappan, P.; Song, Y.; Barman, R.

    2011-12-01

    This presentation explores the sensitivity of terrestrial ecosystems and atmospheric exchange of carbon to global environmental factors to advance our understanding of uncertainty in CO2 projections. We use a land surface model, the Integrated Science Assessment Model (ISAM) recently coupled into the NCAR Community Earth System Model (CESM1) framework to evaluate ecosystem variability due to climatic and anthropogenic factors. The factors considered here include climate change, increasing ambient CO2 concentrations, anthropogenic nitrogen deposition, and land use change (LUC) activities such as clearing of land for agriculture, pasture, and wood harvest. Each factor has a potential to influence the net ecosystem exchange (NEE) of CO2. Using the ISAM-CESM modeling framework, we evaluate the individual and concurrent effects of all these environmental factors on the terrestrial NEE over the 20th century and the 21st century. The ISAM biogeochemical cycles consist of fully prognostic carbon and nitrogen dynamics associated with changes in land cover, litter decomposition, and soil organic matter. The ISAM biophysical model accounts for water and energy processes in the vegetation and soil column, integrated over a time step of 30 minutes. The newly available CRU-NCEP climate forcing data (1850-2010, 0.5ox0.5o spatial resolution) will be used for the historical period simulations. The 21st century simulations will be carried out using the Representative Concentration Pathway (RCP) storylines. This study will help quantify the importance of various environmental factors towards modeling land-atmosphere carbon exchange and better understand model related differences in CO2 estimates.

  5. New satellite project Aerosol-UA: Remote sensing of aerosols in the terrestrial atmosphere

    NASA Astrophysics Data System (ADS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Mishchenko, M.; Rosenbush, V.; Ivanov, Yu.; Makarov, A.; Bovchaliuk, A.; Danylevsky, V.; Sosonkin, M.; Moskalov, S.; Bovchaliuk, V.; Lukenyuk, A.; Shymkiv, A.; Udodov, E.

    2016-06-01

    We discuss the development of the Ukrainian space project Aerosol-UA which has the following three main objectives: (1) to monitor the spatial distribution of key characteristics of terrestrial tropospheric and stratospheric aerosols; (2) to provide a comprehensive observational database enabling accurate quantitative estimates of the aerosol contribution to the energy budget of the climate system; and (3) quantify the contribution of anthropogenic aerosols to climate and ecological processes. The remote sensing concept of the project is based on precise orbital measurements of the intensity and polarization of sunlight scattered by the atmosphere and the surface with a scanning polarimeter accompanied by a wide-angle multispectral imager-polarimeter. Preparations have already been made for the development of the instrument suite for the Aerosol-UA project, in particular, of the multi-channel scanning polarimeter (ScanPol) designed for remote sensing studies of the global distribution of aerosol and cloud properties (such as particle size, morphology, and composition) in the terrestrial atmosphere by polarimetric and spectrophotometric measurements of the scattered sunlight in a wide range of wavelengths and viewing directions from which a scene location is observed. ScanPol is accompanied by multispectral wide-angle imager-polarimeter (MSIP) that serves to collect information on cloud conditions and Earth's surface image. Various components of the polarimeter ScanPol have been prototyped, including the opto-mechanical and electronic assemblies and the scanning mirror controller. Preliminary synthetic data simulations for the retrieval of aerosol parameters over land surfaces have been performed using the Generalized Retrieval of Aerosol and Surface Properties (GRASP) algorithm. Methods for the validation of satellite data using ground-based observations of aerosol properties are also discussed. We assume that designing, building, and launching into orbit a multi-functional high-precision scanning polarimeter and an imager-polarimeter should make a significant contribution to the study of natural and anthropogenic aerosols and their climatic and ecological effects.

  6. The composition, spatial patterns, and influencing factors of atmospheric wet nitrogen deposition in Chinese terrestrial ecosystems.

    PubMed

    Zhu, Jianxing; He, Nianpeng; Wang, Qiufeng; Yuan, Guofu; Wen, Ding; Yu, Guirui; Jia, Yanlong

    2015-04-01

    Atmospheric nitrogen (N) deposition is an important component of the global N cycle, and is a key source of biologically available N. Understanding the spatio-temporal patterns and influencing factors of N deposition is essential to evaluate its ecological effects on terrestrial ecosystems, and to provide a scientific basis for global change research. In this study, we monitored the monthly atmospheric N deposition in rainfall at 41 stations from the Chinese Ecosystem Research Network through measuring total N (TN), total dissolved N (TDN), ammonium (NH4+-N), and nitrate (NO3--N). The results showed that the atmospheric wet deposition of TDN, NH4+-N, and NO3--N were 13.69, 7.25, and 5.93 kg N ha(-1) yr(-1), respectively. The deposition of TN and total particulate N (TPN) was 18.02 and 4.33 kg N ha(-1) yr(-1) respectively, in 2013. TPN accounted for 24% of TN, while NH4+-N and NO3--N made up 40% and 33%, respectively, confirming the assumption that atmospheric wet N deposition would be underestimated without particulate N in rainfall. The N deposition was higher in Central and Southern China, and lower in North-west, North-east, Inner Mongolia, and Qinghai-Tibet regions. Precipitation, N fertilizer use, and energy consumption were significantly correlated with wet N deposition (all p<0.01). Models that included precipitation and N fertilizer can explain 80-91% of the variability in wet N deposition. Our findings reveal, for the first time, the composition of the wet N deposition in China at different scales and highlight the importance of TPN. PMID:25617702

  7. New Constraints on Terrestrial Surface-Atmosphere Fluxes of Gaseous Elemental Mercury Using a Global Database.

    PubMed

    Agnan, Yannick; Le Dantec, Tho; Moore, Christopher W; Edwards, Grant C; Obrist, Daniel

    2016-01-19

    Despite 30 years of study, gaseous elemental mercury (Hg(0)) exchange magnitude and controls between terrestrial surfaces and the atmosphere still remain uncertain. We compiled data from 132 studies, including 1290 reported fluxes from more than 200?000 individual measurements, into a database to statistically examine flux magnitudes and controls. We found that fluxes were unevenly distributed, both spatially and temporally, with strong biases toward Hg-enriched sites, daytime and summertime measurements. Fluxes at Hg-enriched sites were positively correlated with substrate concentrations, but this was absent at background sites. Median fluxes over litter- and snow-covered soils were lower than over bare soils, and chamber measurements showed higher emission compared to micrometeorological measurements. Due to low spatial extent, estimated emissions from Hg-enriched areas (217 Mga(-1)) were lower than previous estimates. Globally, areas with enhanced atmospheric Hg(0) levels (particularly East Asia) showed an emerging importance of Hg(0) emissions accounting for half of the total global emissions estimated at 607 Mga(-1), although with a large uncertainty range (-513 to 1353 Mga(-1) [range of 37.5th and 62.5th percentiles]). The largest uncertainties in Hg(0) fluxes stem from forests (-513 to 1353 Mga(-1) [range of 37.5th and 62.5th percentiles]), largely driven by a shortage of whole-ecosystem fluxes and uncertain contributions of leaf-atmosphere exchanges, questioning to what degree ecosystems are net sinks or sources of atmospheric Hg(0). PMID:26599393

  8. Studies of volatiles and organic materials in early terrestrial and present-day outer solar system environments

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Thompson, W. Reid; Chyba, Christopher F.; Khare, B. N.

    1991-01-01

    A review and partial summary of projects within several areas of research generally involving the origin, distribution, chemistry, and spectral/dielectric properties of volatiles and organic materials in the outer solar system and early terrestrial environments are presented. The major topics covered include: (1) impact delivery of volatiles and organic compounds to the early terrestrial planets; (2) optical constants measurements; (3) spectral classification, chemical processes, and distribution of materials; and (4) radar properties of ice, hydrocarbons, and organic heteropolymers.

  9. Impacts and the early environment and evolution of the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Melosh, H. J.; Vickery, A. M.

    1991-01-01

    It is now admitted that very large impacts may have played an important role in the accretion of the terrestrial planets. The size-frequency distribution of these impacts fits the formal definition of a catastrophic process: the mass and momentum added by a rare large impact is larger than that added by all the more frequent small impacts combined. The effects of such large impacts on the thermal states of growing planets is discussed. At a later stage of planetary evolution, the smaller impacts during late heavy bombardment may have played an important role in stripping the original gaseous atmospheres of the planets and in segregating condensible substances from volatile ones.

  10. Middle atmosphere electrodynamics: Report of the workshop on the Role of the Electrodynamics of the Middle Atmosphere on Solar Terrestrial Coupling

    NASA Technical Reports Server (NTRS)

    Maynard, N. C. (Editor)

    1979-01-01

    Significant deficiencies exist in the present understanding of the basic physical processes taking place within the middle atmosphere (the region between the tropopause and the mesopause), and in the knowledge of the variability of many of the primary parameters that regulate Middle Atmosphere Electrodynamics (MAE). Knowledge of the electrical properties, i.e., electric fields, plasma characteristics, conductivity and currents, and the physical processes that govern them is of fundamental importance to the physics of the region. Middle atmosphere electrodynamics may play a critical role in the electrodynamical aspects of solar-terrestrial relations. As a first step, the Workshop on the Role of the Electrodynamics of the Middle Atmosphere on Solar-Terrestrial Coupling was held to review the present status and define recommendations for future MAE research.

  11. The chemical composition and climatology of the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Henderson-Sellers, A.

    1983-01-01

    The earth's climate as it relates to the evolution of life is discussed.. Seven fundamental characteristics of the early evolutionary environment are examined, including a carbon dioxide and water vapor atmosphere, atmospheric mass between 500 and 1000 mb, a global hydrosphere, lowered solar luminosity, hospitable average global temperatures, a convectively active atmosphere, and trace gases. The influence of the early earth's extensive hydrosphere on the origin of life is considered. The warming of that hydrosphere due to radiative fluxes and the greenhouse effect is examined, and the nature of the feedback between clouds and climate is addressed.

  12. Remote sensing of aerosol in the terrestrial atmosphere from space: new missions

    NASA Astrophysics Data System (ADS)

    Milinevsky, G.; Yatskiv, Ya.; Degtyaryov, O.; Syniavskyi, I.; Ivanov, Yu.; Bovchaliuk, A.; Mishchenko, M.; Danylevsky, V.; Sosonkin, M.; Bovchaliuk, V.

    2015-09-01

    The distribution and properties of atmospheric aerosols on a global scale are not well known in terms of determination of their effects on climate. This mostly is due to extreme variability of aerosol concentrations, properties, sources, and types. Aerosol climate impact is comparable to the effect of greenhouse gases, but its influence is more difficult to measure, especially with respect to aerosol microphysical properties and the evaluation of anthropogenic aerosol effect. There are many satellite missions studying aerosol distribution in the terrestrial atmosphere, such as MISR/Terra, OMI/Aura, AVHHR, MODIS/Terra and Aqua, CALIOP/CALIPSO. To improve the quality of data and climate models, and to reduce aerosol climate forcing uncertainties, several new missions are planned. The gap in orbital instruments for studying aerosol microphysics has arisen after the Glory mission failed during launch in 2011. In this review paper, we describe several planned aerosol space missions, including the Ukrainian project Aerosol-UA that obtains data using a multi-channel scanning polarimeter and wide-angle polarimetric camera. The project is designed for remote sensing of the aerosol microphysics and cloud properties on a global scale.

  13. Terrestrial influence on atmospheric carbon dioxide, a mechanistic study using oxygen-18

    NASA Astrophysics Data System (ADS)

    Fessenden, Julianna Eileen

    The present carbon budget is unbalanced due to anthropogenic influences. Atmospheric warming might have resulted from rising atmospheric carbon dioxide levels. Sequestration of this CO2 is observed in oceans and land vegetation, though questions arise regarding the magnitude of the terrestrial biosphere sink. These questions can be addressed by measuring the abundance of the light stable isotopes of oxygen (16O, and 18O in CO2) in the biological and chemical processes which produce and consume CO2. This work applies known methods of CO2 isolation and mass spectrometric analysis to address questions regarding the mechanisms of isotopic fractionation during land-atmosphere exchange where global, regional, local, and point-spot studies are researched. Atmospheric CO2 exchange with land masses influences about 80% of the delta18O signature yielding exchange fluxes on the order of 200 GtC yr-1. Land biosphere controls the seasonal cycle of CO2 and the offsets observed in the seasonal swing of the isotopic ratios, 13C/12C and 18O/16O (4--6 month shifts). When we looked closer at magnitudes of land-atmosphere exchanges, we saw that the respiratory flux was 100 times greater than the photosynthetic flux during the summer on the day of measurement in a coniferous forest system (3612 mumol m-2 s-1). Therefore, this regional isotopic signature was thought to be dominated by the delta 18O of soil respired CO2. Further inspection of the controlling mechanisms of soil respired CO 2 was then addressed where offsets (20‰) from soil water were observed in moisture limited ridge-top soils. Also, kinetic fractionation due to molecular diffusion through the soil column (thought to be 8.8‰) was not observed within the moisture limited, unsaturated, or saturated conditions within a grassland or forest ecosystem. On a localized scale, we conducted experiments on isotopically tracing water movement in a rooting zone. The results showed increased production of trace gases leading to increased emission rates (shown in CO2). In conclusion, plant ecosystems have a strong influence on isotopic compositions of atmospheric CO2, where fluxes can be monitored with delta 18O.

  14. Early Paleogene evolution of terrestrial climate in the SW Pacific, Southern New Zealand

    NASA Astrophysics Data System (ADS)

    Pancost, Richard D.; Taylor, Kyle W. R.; Inglis, Gordon N.; Kennedy, Elizabeth M.; Handley, Luke; Hollis, Christopher J.; Crouch, Erica M.; Pross, Jörg; Huber, Matthew; Schouten, Stefan; Pearson, Paul N.; Morgans, Hugh E. G.; Raine, J. Ian

    2013-12-01

    We present a long-term record of terrestrial climate change for the Early Paleogene of the Southern Hemisphere that complements previously reported marine temperature records. Using the MBT'-CBT proxy, based on the distribution of soil bacterial glycerol dialkyl glycerol tetraether lipids, we reconstructed mean annual air temperature (MAT) from the Middle Paleocene to Middle Eocene (62-42 Ma) for southern New Zealand. This record is consistent with temperature estimates derived from leaf fossils and palynology, as well as previously published MBT'-CBT records, which provides confidence in absolute temperature estimates. Our record indicates that through this interval, temperatures were typically 5°C warmer than those of today at such latitudes, with more pronounced warming during the Early Eocene Climate Optimum (EECO; ˜50 Ma) when MAT was ˜20°C. Moreover, the EECO MATs are similar to those determined for Antarctica, with a weak high-latitude terrestrial temperature gradient (˜5°C) developing by the Middle Eocene. We also document a short-lived cooling episode in the early Late Paleocene when MAT was comparable to present. This record corroborates the trends documented by sea surface temperature (SST) proxies, although absolute SSTs are up to 6°C warmer than MATs. Although the high-calibration error of the MBT'-CBT proxy dictates caution, the good match between our MAT results and modeled temperatures supports the suggestion that SST records suffer from a warm (summer?) bias, particularly during times of peak warming.

  15. Using Dimers to Measure Biosignatures and Atmospheric Pressure for Terrestrial Exoplanets

    PubMed Central

    Meadows, Victoria; Claire, Mark; Crisp, Dave

    2014-01-01

    Abstract We present a new method to probe atmospheric pressure on Earth-like planets using (O2-O2) dimers in the near-infrared. We also show that dimer features could be the most readily detectable biosignatures for Earth-like atmospheres and may even be detectable in transit transmission with the James Webb Space Telescope (JWST). The absorption by dimers changes more rapidly with pressure and density than that of monomers and can therefore provide additional information about atmospheric pressures. By comparing the absorption strengths of rotational and vibrational features to the absorption strengths of dimer features, we show that in some cases it may be possible to estimate the pressure at the reflecting surface of a planet. This method is demonstrated by using the O2 A band and the 1.06 μm dimer feature, either in transmission or reflected spectra. It works best for planets around M dwarfs with atmospheric pressures between 0.1 and 10 bar and for O2 volume mixing ratios above 50% of Earth's present-day level. Furthermore, unlike observations of Rayleigh scattering, this method can be used at wavelengths longer than 0.6 μm and is therefore potentially applicable, although challenging, to near-term planet characterization missions such as JWST. We also performed detectability studies for JWST transit transmission spectroscopy and found that the 1.06 and 1.27 μm dimer features could be detectable (SNR>3) for an Earth analogue orbiting an M5V star at a distance of 5 pc. The detection of these features could provide a constraint on the atmospheric pressure of an exoplanet and serve as biosignatures for oxygenic photosynthesis. We calculated the required signal-to-noise ratios to detect and characterize O2 monomer and dimer features in direct imaging–reflected spectra and found that signal-to-noise ratios greater than 10 at a spectral resolving power of R=100 would be required. Key Words: Remote sensing—Extrasolar terrestrial planets—Habitability—Radiative transfer—Biosignatures. Astrobiology 14, 67–86. PMID:24432758

  16. A terrestrial vegetation turnover in the middle of the Early Triassic

    NASA Astrophysics Data System (ADS)

    Saito, Ryosuke; Kaiho, Kunio; Oba, Masahiro; Takahashi, Satoshi; Chen, Zhong-Qiang; Tong, Jinnan

    2013-06-01

    Land-plant productivity was greatly reduced after the end-Permian mass extinction, causing a pronounced "coal gap" worldwide during the Early Triassic. Newly obtained organic geochemistry data from the Chaohu area, south China, indicated an abrupt and profound terrestrial vegetation change over the middle part of the Early Triassic Smithian-Spathian (S-S) interval. Herbaceous lycopsids and/or bryophytes dominated terrestrial vegetation from Griesbachian to Smithian times. The terrestrial ecosystem underwent an abrupt change, and woody conifers became dominant over the S-S interval. Several important biomarkers, namely retene, simonellite, and dehydroabietane (with multiple sources: conifer, lycopsid, and/or herbaceous bryophyte), were relatively abundant during Griesbachian, Dienerian, and Smithian times. The relatively low C/N ratio values during the Griesbachian-Smithian interval indicate that these biomarkers were likely sourced from herbaceous lycopsids and/or bryophytes. The extremely abundant conifer-sourced pimanthrene, combined with relatively high C/N ratio values, suggested the recovery of woody conifers after the S-S boundary. The new data revealed that the switch from herbaceous vegetation to woody coniferous vegetation marked a terrestrial plant recovery, which occurred globally within 3 million years after the end-Permian crisis rather than at a later date estimated in previous studies. In Chaohu, the S-S terrestrial event was marked by a reappearance of woody vegetation, while the S-S marine event was marked by an increase in ichnodiversity, trace complexity, burrow size, infaunal tiering level, and bioturbation level, and a possible intense upwelling event indicated by the extended tricyclic terpane ratios (ETR). Coeval vegetation changes with comparable patterns have also been documented in Europe and Pakistan based on palynologic studies. The S-S boundaries in Asia and Europe are associated with a positive δ13C excursion, the rebound of woody vegetation, a turnover of ammonoid faunas, and possible global climate cooling. This is the first study to document the S-S event using biomarkers and C/N ratios.

  17. The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO2 in the United States

    USGS Publications Warehouse

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, A.D.; Helfrich, J.

    1999-01-01

    We use the Terrestrial Ecosystem Model (TEM, Version 4.1) and the land cover data set of the international geosphere-biosphere program to investigate how increasing atmospheric CO2 concentration and climate variability during 1900-1994 affect the carbon storage of terrestrial ecosystems in the conterminous USA, and how carbon storage has been affected by land-use change. The estimates of TEM indicate that over the past 95 years a combination of increasing atmospheric CO2 with historical temperature and precipitation variability causes a 4.2% (4.3 Pg C) decrease in total carbon storage of potential vegetation in the conterminous US, with vegetation carbon decreasing by 7.2% (3.2 Pg C) and soil organic carbon decreasing by 1.9% (1.1 Pg C). Several dry periods including the 1930s and 1950s are responsible for the loss of carbon storage. Our factorial experiments indicate that precipitation variability alone decreases total carbon storage by 9.5%. Temperature variability alone does not significantly affect carbon storage. The effect of CO2 fertilization alone increases total carbon storage by 4.4%. The effects of increasing atmospheric CO2 and climate variability are not additive. Interactions among CO2, temperature and precipitation increase total carbon storage by 1.1%. Our study also shows substantial year-to-year variations in net carbon exchange between the atmosphere and terrestrial ecosystems due to climate variability. Since the 1960s, we estimate these terrestrial ecosystems have acted primarily as a sink of atmospheric CO2 as a result of wetter weather and higher atmospheric CO2 concentrations. For the 1980s, we estimate the natural terrestrial ecosystems, excluding cropland and urban areas, of the conterminous US have accumulated 78.2 Tg C yr-1 because of the combined effect of increasing atmospheric CO2 and climate variability. For the conterminous US, we estimate that the conversion of natural ecosystems to cropland and urban areas has caused a 18.2% (17.7 Pg C) reduction in total carbon storage from that estimated for potential vegetation. The carbon sink capacity of natural terrestrial ecosystems in the conterminous US is about 69% of that estimated for potential vegetation.

  18. Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.

    PubMed

    Krupa, S V

    2003-01-01

    At the global scale, among all N (nitrogen) species in the atmosphere and their deposition on to terrestrial vegetation and other receptors, NH3 (ammonia) is considered to be the foremost. The major sources for atmospheric NH3 are agricultural activities and animal feedlot operations, followed by biomass burning (including forest fires) and to a lesser extent fossil fuel combustion. Close to its sources, acute exposures to NH3 can result in visible foliar injury on vegetation. NH3 is deposited rapidly within the first 4-5 km from its source. However, NH3 is also converted in the atmosphere to fine particle NH4+ (ammonium) aerosols that are a regional scale problem. Much of our current knowledge of the effects of NH3 on higher plants is predominantly derived from studies conducted in Europe. Adverse effects on vegetation occur when the rate of foliar uptake of NH3 is greater than the rate and capacity for in vivo detoxification by the plants. Most to least sensitive plant species to NH3 are native vegetation > forests > agricultural crops. There are also a number of studies on N deposition and lichens, mosses and green algae. Direct cause and effect relationships in most of those cases (exceptions being those locations very close to point sources) are confounded by other environmental factors, particularly changes in the ambient SO2 (sulfur dioxide) concentrations. In addition to direct foliar injury, adverse effects of NH3 on higher plants include alterations in: growth and productivity, tissue content of nutrients and toxic elements, drought and frost tolerance, responses to insect pests and disease causing microorganisms (pathogens), development of beneficial root symbiotic or mycorrhizal associations and inter species competition or biodiversity. In all these cases, the joint effects of NH3 with other air pollutants such as all-pervasive O3 or increasing CO2 concentrations are poorly understood. While NH3 uptake in higher plants occurs through the shoots, NH4+ uptake occurs through the shoots, roots and through both pathways. However, NH4+ is immobile in the soil and is converted to NO3- (nitrate). In agricultural systems, additions of NO3- to the soil (initially as NH3 or NH4+) and the consequent increases in the emissions of N2O (nitrous oxide, a greenhouse gas) and leaching of NO3- into the ground and surface waters are of major environmental concern. At the ecosystem level NH3 deposition cannot be viewed alone, but in the context of total N deposition. There are a number of forest ecosystems in North America that have been subjected to N saturation and the consequent negative effects. There are also heathlands and other plant communities in Europe that have been subjected to N-induced alterations. Regulatory mitigative approaches to these problems include the use of N saturation data or the concept of critical loads. Current information suggests that a critical load of 5-10 kg ha(-1) year(-1) of total N deposition (both dry and wet deposition combined of all atmospheric N species) would protect the most vulnerable terrestrial ecosystems (heaths, bogs, cryptogams) and values of 10-20 kg ha(-1) year(-1) would protect forests, depending on soil conditions. However, to derive the best analysis, the critical load concept should be coupled to the results and consequences of N saturation. PMID:12713921

  19. Early tetrapod evolution and the progressive integration of Permo-Carboniferous terrestrial ecosystems

    SciTech Connect

    Beerbower, J.R. . Dept. of Geological Science); Olson, E.C. . Dept. of Biology); Hotton, N. III . Dept. of Paleobiology)

    1992-01-01

    Variation among Permo-Carboniferous tetrapod assemblages demonstrates major transformations in pathways and rates of energy and nutrient transfer, in integration of terrestrial ecosystems and in predominant ecologic modes. Early Carboniferous pathways were through plant detritus to aquatic and terrestrial detritivores and thence to arthropod and vertebrate meso-and macro-predators. Transfer rates (and efficiency) were low as was ecosystem integration; the principal ecologic mode was conservation. Late Carboniferous and Early Permian assemblages demonstrate an expansion in herbivory, primarily in utilization of low-fiber plant tissue by insects. But transfer rates, efficiency and integration were still limited because the larger portion of plant biomass, high-fiber tissues, still went into detrital pathways; high-fiber'' herbivores, i.e., tetrapods, were neither abundant or diverse, reflecting limited resources, intense predation and limited capabilities for processing fiber-rich food. The abundance and diversity of tetrapod herbivores in upper Permian assemblages suggests a considerable transfer of energy from high-fiber tissues through these animals to tetrapod predators and thus higher transfer rates and efficiencies. It also brought a shift in ecological mode toward acquisition and regulation and tightened ecosystem integration.

  20. Effects of Earth's rotation on the early differentiation of a terrestrial magma ocean

    NASA Astrophysics Data System (ADS)

    Maas, Christian; Hansen, Ulrich

    2015-11-01

    Similar to other terrestrial planets like Moon and Mars, Earth experienced a magma ocean period about 4.5 billion years ago. On Earth differentiation processes in the magma ocean set the initial conditions for core formation and mantle evolution. During the magma ocean period Earth was rotating significantly faster than today. Further, the viscosity of the magma was low, thus that planetary rotation potentially played an important role for differentiation. However, nearly all previous studies neglect rotational effects. All in all, our results suggest that planetary rotation plays an important role for magma ocean crystallization. We employ a 3-D numerical model to study crystal settling in a rotating and vigorously convecting early magma ocean. We show that crystal settling in a terrestrial magma ocean is crucially affected by latitude as well as by rotational strength and crystal density. Due to rotation an inhomogeneous accumulation of crystals during magma ocean solidification with a distinct crystal settling between pole and equator could occur. One could speculate that this may have potentially strong effects on the magma ocean solidification time and the early mantle composition. It could support the development of a basal magma ocean and the formation of anomalies at the core-mantle boundary in the equatorial region, reaching back to the time of magma ocean solidification.

  1. 3D-radiative transfer in terrestrial atmosphere: An efficient parallel numerical procedure

    NASA Astrophysics Data System (ADS)

    Bass, L. P.; Germogenova, T. A.; Nikolaeva, O. V.; Kokhanovsky, A. A.; Kuznetsov, V. S.

    2003-04-01

    Light propagation and scattering in terrestrial atmosphere is usually studied in the framework of the 1D radiative transfer theory [1]. However, in reality particles (e.g., ice crystals, solid and liquid aerosols, cloud droplets) are randomly distributed in 3D space. In particular, their concentrations vary both in vertical and horizontal directions. Therefore, 3D effects influence modern cloud and aerosol retrieval procedures, which are currently based on the 1D radiative transfer theory. It should be pointed out that the standard radiative transfer equation allows to study these more complex situations as well [2]. In recent year the parallel version of the 2D and 3D RADUGA code has been developed. This version is successfully used in gammas and neutrons transport problems [3]. Applications of this code to radiative transfer in atmosphere problems are contained in [4]. Possibilities of code RADUGA are presented in [5]. The RADUGA code system is an universal solver of radiative transfer problems for complicated models, including 2D and 3D aerosol and cloud fields with arbitrary scattering anisotropy, light absorption, inhomogeneous underlying surface and topography. Both delta type and distributed light sources can be accounted for in the framework of the algorithm developed. The accurate numerical procedure is based on the new discrete ordinate SWDD scheme [6]. The algorithm is specifically designed for parallel supercomputers. The version RADUGA 5.1(P) can run on MBC1000M [7] (768 processors with 10 Gb of hard disc memory for each processor). The peak productivity is equal 1 Tfl. Corresponding scalar version RADUGA 5.1 is working on PC. As a first example of application of the algorithm developed, we have studied the shadowing effects of clouds on neighboring cloudless atmosphere, depending on the cloud optical thickness, surface albedo, and illumination conditions. This is of importance for modern satellite aerosol retrieval algorithms development. [1] Sobolev, V. V., 1972: Light scattering in planetary atmosphere, M.:Nauka. [2] Evans, K. F., 1998: The spherical harmonic discrete ordinate method for three dimensional atmospheric radiative transfer, J. Atmos. Sci., 55, 429 446. [3] L.P. Bass, T.A. Germogenova, V.S. Kuznetsov, O.V. Nikolaeva. RADUGA 5.1 and RADUGA 5.1(P) codes for stationary transport equation solution in 2D and 3D geometries on one and multiprocessors computers. Report on seminar “Algorithms and Codes for neutron physical of nuclear reactor calculations” (Neutronica 2001), Obninsk, Russia, 30 October 2 November 2001. [4] T.A. Germogenova, L.P. Bass, V.S. Kuznetsov, O.V. Nikolaeva. Mathematical modeling on parallel computers solar and laser radiation transport in 3D atmosphere. Report on International Symposium CIS countries “Atmosphere radiation”, 18 21 June 2002, St. Peterburg, Russia, p. 15 16. [5] L.P. Bass, T.A. Germogenova, O.V. Nikolaeva, V.S. Kuznetsov. Radiative Transfer Universal 2D 3D Code RADUGA 5.1(P) for Multiprocessor Computer. Abstract. Poster report on this Meeting. [6] L.P. Bass, O.V. Nikolaeva. Correct calculation of Angular Flux Distribution in Strongly Heterogeneous Media and Voids. Proc. of Joint International Conference on Mathematical Methods and Supercomputing for Nuclear Applications, Saratoga Springs, New York, October 5 9, 1997, p. 995 1004. [7] http://www/jscc.ru

  2. Effects of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Dach, R.; Heflin, M. B.; Gross, R. S.; König, R.; Lemoine, F. G.; MacMillan, D. S.; Parker, J. W.; van Dam, T. M.; Wu, X.

    2013-12-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS global networks used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, the effect of non-tidal atmospheric loading (NTAL) corrections on the TRF is assessed adopting a Remove/Restore approach: (i) Focusing on the a-posteriori approach, the NTAL model derived from the National Center for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations. (ii) Adopting a Kalman-filter based approach, a linear TRF is estimated combining the 4 SG solutions free from NTAL displacements. (iii) Linear fits to the NTAL displacements removed at step (i) are restored to the linear reference frame estimated at (ii). The velocity fields of the (standard) linear reference frame in which the NTAL model has not been removed and the one in which the model has been removed/restored are compared and discussed.

  3. Mobile sampler for use in acquiring samples of terrestrial atmospheric gases

    NASA Technical Reports Server (NTRS)

    Tucker, C. E.; Holway, H. P. (Inventor)

    1981-01-01

    Samples of terrestrial atmospheric gasses from a free body of such gasses using a device characterized by a plurality of tubular bodies adapted to be mounted in side by side relation on a motorized highway vehicle in mutual parallelism with the axis of the normal path of travel for the vehicles. Each of the bodies is of a cylindrical configuration and has an axial opening at each of its opposite ends through which a linear flow path is defined. A pair of pivotally supported, spring-biased sealing caps is mounted adjacent to the ends of the body and continuously urged into a hermetic sealing relationship. A restraint for securing the caps against spring-urged pivotal displacement, includes a separable, normally tensioned line interconnecting the caps and an operable release mechanism for simultaneously releasing the caps for spring-urged displacement. A hot wire cutter is included for separating the line, whereby samples of air are trapped in the body as the caps are spring-driven to assume an hermetically sealed relation with the openings defined in each of the opposite ends of the body.

  4. Photochemical model for NH3 in an early Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Brown, L. L.; Kasting, J. F.

    1992-01-01

    A warm and wet climate scenario for early Mars has been explained by invoking a 5-bar CO2 atmosphere; however, Kasting has shown that CO2 will condense in the Martian atmosphere at these pressures. The formation of CO2 clouds will reduce the convection lapse rate and reduce the magnitude of the greenhouse effect. It is possible that additional greenhouse gases such as methane and ammonia were present in the early Mars atmosphere. We are using a one dimensional photochemical model to estimate the magnitude of the ammonia source required to maintain a given ammonia concentration in a dense CO2 atmosphere. Because CO2 is 2.5 times more efficient at Rayleigh scattering than Earth's N2 atmosphere, we anticipate increased scattering opacities and decreased photolytic destruction rates of ammonia on early Mars. The reduced gravity on Mars means that a 1 bar atmosphere will be approximately 3 times as thick as on Earth. It is possible that ammonia could have been shielded from photolysis by hydrocarbon aerosols which form as a product of methane photolysis.

  5. Increased delivery of condensation nuclei during the Late Heavy Bombardment to the terrestrial and martian atmospheres

    NASA Astrophysics Data System (ADS)

    Losiak, Anna

    2014-05-01

    During the period of the Late Heavy Bombardment (LHB), between 4.1 and 3.8 Ga, the impact rate within the entire Solar System was up to a few thousand times higher than the current value (Ryder 2002, Bottke et al. 2012, Fassett and Minton 2013). Multiple basin-forming events on inner planets that occurred during this time had a strong but short-lasting (up to few thousands of years) effect on atmospheres of Earth and Mars (Sleep et al. 1989, Segura et al. 2002, 2012). However, the role of the continuous flux of smaller impactors has not been assessed so far. We calculated the amount of meteoric material in the 10^-3 kg to 106 kg size range delivered to Earth and Mars during the LHB based on the impact flux at the top of the Earth's atmosphere based on results from Bland and Artemieva (2006). Those values were recalculated for Mars based on Ivanov and Hartmann (2009) and then recalculated to the LHB peak based on estimates from Ryder (2002), Bottke et al. (2012), Fassett and Minton (2013). During the LHB, the amount of meteoritic material within this size range delivered to Earth was up to ~1.7*10^10 kg/year and 1.4*10^10 kg/year for Mars. The impactors that ablate and are disrupted during atmospheric entry can serve as cloud condensation nuclei (Rosen 1968, Hunten et al. 1980, Ogurtsov and Raspopov 2011). The amount of material delivered during LHB to the upper stratosphere and lower mezosphere (Hunten et al. 1980, Bland and Artemieva 2006) is comparable to the current terrestrial annual emission of mineral cloud condensation nuclei of 0.5-8*10^12 kg/year (Tegen 2003). On Mars, the availability of condensation nuclei is one of the main factors guiding water-ice cloud formation (Montmessin et al. 2004), which is in turn one of the main climatic factors influencing the hydrological cycle (Michaels et al. 2006) and radiative balance of the planet (Haberle et al. 1999, Wordsworth et al. 2013, Urata and Toon 2013). Increased delivery of condensation nuclei during the LHB should be taken into account when constructing models of terrestrial and Martian climates around 4 Ga. Bland P.A., Artemieva N.A. (2006) Meteorit.Planet.Sci. 41:607-631. Bottke W.F. et al. (2012) Nature 485: 78-81. Fassett C.I., Minton D.A. (2013) Nat.Geosci. 6:520-524 (2013). Hunten D.M. et al. (1980) J.Atmos.Sci. 37:1342-1357. Haberle R.M. et al. (1999) J.Geophys.Res. 104:8957-8974. Ivanov B.A., Hartmann W.K. (2009) Planets and Moons: Treatise on Geophysics (eds. Spohn T.): 207-243. Michaels T.I. et al. (2006) Geophys.Res.Lett. 33:L16201. Montmessin F. et al. (2004) J.Geophys.Res. 109:E10004. Ogurtsov M.G., Raspopov O.M. (2011) Geomagnetism&Aeronomy 51:275-283. Rosen J.M. (1968) Space Sci.Rev. 9:58-89. Ryder G. (2002) J.Geophys.Res. 107: doi:10.1029/2001JE001583. Segura T.L. et al. (2002) Science 298:1977-1980. Segura T.L. et al. (2012) Icarus 220:144-148. Sleep N.S. et al. (1989) Nature 342:139-142. Tegen I. (2003) Quat.Sci.Rev. 22:1821-1834. Urata R.A., Toon O.B. (2013) Icarus 226:229-250. Wordsworth R. et al. (2012) Icarus 222:1-19.

  6. Comparative analysis of the atmospheres of early earth and early Mars

    NASA Technical Reports Server (NTRS)

    Durham, R.; Schmunk, R. B.; Chamberlain, J. W.

    1989-01-01

    Assuming that the primitive atmospheres of Mars and earth were similar and that present differences in atmospheres of earth and Mars are a result of their different distances from the sun and their different masses, the atmospheres of the early earth and early Mars were analyzed. A one-dimensional radiative-convective model derived from that of Kasting et al. (1984) and Kasting and Ackerman (1986) was then used to determine if a 1.3-bar CO2 partial pressure on Mars (which is equivalent to about 9 bars on earth) is consistent with the climatic conditions thought to have existed on earth four billion years ago. Results indicate that a dense CO2 atmosphere on early Mars at perihelion is consistent with conditions expected to have existed four billion years ago on earth. Earth would then have had a stable atmosphere with temperatures warm enough to support liquid water on the surface.

  7. Simulation of atmospheric and terrestrial background signatures for detection and tracking scenarios

    NASA Astrophysics Data System (ADS)

    Schweitzer, Caroline; Stein, Karin

    2015-10-01

    In the fields of early warning, one is depending on reliable image exploitation: Only if the applied detection and tracking algorithms work efficiently, the threat approach alert can be given fast enough to ensure an automatic initiation of the countermeasure. In order to evaluate the performance of those algorithms for a certain electro-optical (EO) sensor system, test sequences need to be created as realistic and comprehensive as possible. Since both, background and target signature, depend on the environmental conditions, a detailed knowledge of the meteorology and climatology is necessary. Trials for measuring these environmental characteristics serve as a solid basis, but might only constitute the conditions during a rather short period of time. To represent the entire variation of meteorology and climatology that the future system will be exposed to, the application of comprehensive atmospheric modelling tools is essential. This paper gives an introduction of the atmospheric modelling tools that are currently used at Fraunhofer IOSB to simulate spectral background signatures in the infrared (IR) range. It is also demonstrated, how those signatures are affected by changing atmospheric and climatic conditions. In conclusion - and with a special focus on the modelling of different cloud types - sources of error and limits are discussed.

  8. Variations in carbon exchange between terrestrial ecosystems and the atmosphere due to CO{sub 2} evaluation and climate change

    SciTech Connect

    Cao, M.; Woodward, F.I.

    1997-12-31

    The global carbon budget for atmospheric CO{sub 2} can`t been balanced, a sink of 1 to 3 Gt C yr{sup -1} has not yet been clearly identified. Without a good account for the fate of the miss carbon, prediction of future atmospheric CO{sub 2} concentration and climate change will remain uncertain. It is suggested that terrestrial ecosystems may take up the miss carbon. To validate this hypothesis and to improve the estimates of the carbon sink or source strength requires a direct investigation of the carbon exchange of terrestrial ecosystems and its response to atmospheric CO{sub 2} elevation and climate change at the global scale. In this study, a highly aggregated model was developed on the basis of photosynthesis, plant growth, litter production and soil organic carbon decomposition. And the model was use to predict the variations in carbon fluxes between terrestrial ecosystems and the atmosphere from 1860 to 2020. In our estimates, climate change alone does not cause a significant variation in net primary production (NPP), but results in a reduction in net ecosystem production (NEP) by 50% thus, a decrease in the total carbon storage, since 1960s. Climate change happened undercuts the capacity of terrestrial ecosystems taking up atmospheric CO{sub 2}. Without climate change, CO{sub 2} elevation enhances NPP and NEP steadily. NPP is enhanced by 26% and NEP is increased from about 1.0 Gt C yr{sup -1} in 1860s to 4.0 Gt C yr{sup -1} in 2020s. The combined CO{sub 2} elevation and climate change increase the global annual NPP from 46.0 Gt C in 1860s to 57.0 Gt C in 2010s. NEP is increased to 2.1 Gt C yr{sup -1} in 1980s and about 3.6 Gt C yr{sup -1} in 2010s. The increase occurs in both the northern middle-high latitudes and tropical regions. Taking land use change into account, terrestrial ecosystems are nearly carbon-balanced before 1950s, but afterwards they become a significant sink of about 1.6 Gt C yr{sup -1} for atmospheric CO{sub 2}.

  9. Modelling the impact of atmospheric and terrestrial inputs on the Black Sea coastal dynamics

    NASA Astrophysics Data System (ADS)

    Kourafalou, V. H.; Stanev, E. V.

    2001-02-01

    The dynamics on the North Western Shelf area of the Black Sea are examined, with an emphasis on the circulation induced by buoyancy due to the land drained fresh waters and by the interaction with the atmosphere, notably wind stress. A three-dimensional, multi-layer hydrodynamic model is employed with realistic topography and parameterisation of river plume physics. We focus on the seasonal patterns of transport of the river induced low-salinity waters within the Coastal Low Salinity Band and the conditions that influence their removal toward the shelf interior. The numerical simulations show that coastal circulation is greatly influenced by river runoff and especially in the case of the Danube, which is excessively high with monthly aver-aged values ranging from 5000 to 10000 m3 /s. A significant contribution of runoff comes from the neighbouring rivers. At the same time, the North Western Shelf is quite broad, so that the coastal dynamics are largely sheltered from the conditions in the deeper sea. Buoyancy due to river runoff thus dominates, creating a southward coastal current that is the predominant pathway for the land-drained inputs. As in all shelf areas, wind stress is a major circulation forcing mechanism and it modifies the buoyancy induced flow. It is shown that the seasonal variability in river runoff and wind stress, in combination with the shelf topography, determines the different pathways for the terrestrial inputs. Implications on the overall basin circulation are drawn, as the availability of low-salinity waters of river origin affects the upper Black Sea layer. Consequently, the formation of distinct water masses (such as the Cold Intermediate Layer) and the properties of the outflow toward the Mediterranean are also influenced.

  10. An approach to balancing the positive and negative effects of elevated nitrogen oxides in the lower atmosphere on terrestrial plants.

    PubMed

    Semenov, S

    2001-09-24

    Elevated NOx in the lower atmosphere has three major effects on terrestrial plants. On the one hand, it causes an increase in surface ozone concentration. This reduces plant growth rate. On the other hand, elevated NOx causes an increase in the flux of oxidized N compounds from the atmosphere to the land surface. This plays a dual role in the life of terrestrial plants. Additional N in soils stimulates plant growth (N-fertilization effect), whereas soil acidification may negatively affect plants. A simple empirical model for calculating the overall effect of anthropogenic increase in NOx level has been developed. The model is based on experimental "cause-response" data presented in world scientific literature. Calculations showed that at the large scale, among the above-mentioned changes, elevated O3 plays a major and negative role in plant life. Its negative effect on plants is partly compensated by N fertilization in unmanaged ecosystems. Such compensation appears to be negligible in agricultural lands. There are vast territories in Euro--Asia--for instance, a territory of Russia--in which acid atmospheric deposition has no significant effect on terrestrial plants. PMID:12806067

  11. Heterogeneous Reactions of Polycyclic Aromatic Hydrocarbons on Atmospheric and Terrestrial Surfaces

    NASA Astrophysics Data System (ADS)

    Simonich, S. L.

    2014-12-01

    The heterogeneous reactions of five higher molecular weight polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene-d12 (BaP-d12), benzo(k)fluoranthene-d12 (BkF-d12), benzo[g,h,i]perylene-d12 (BghiP-d12), dibenzo(a,i)pyrene-d14 (DBaiP-d14), and dibenzo[a,l]pyrene (DalP), with NO2, NO3/N2O5, O3, and OH radicals were investigated in a 7000 L indoor Teflon chamber. Quartz fiber filters (QFF) were used as the reaction surface and substrate and the analyses of parent PAHs and Nitro-PAH (NPAH) products was conducted using electron impact gas chromatographic mass spectrometry (GC/MS) and negative chemical ionization GC/MS. In parallel to the laboratory experiments, a theoretical study was conducted to assist in determining the formation of NPAH isomers based on the OH-radical initiated reaction. The thermodynamic stability of OH-PAH intermediates was used to indicate the position of highest electron density and the most stable NPAH products were synthesized to confirm their identity. NO2 and NO3/N2O5 were the most effective oxidizing agents in transforming PAHs deposited on filters to NPAHs, under the experimental conditions. Reaction of BaP-d12, BkF-d12 and BghiP-d12 resulted in the formation of several mono-nitro PAH isomer product, while the reaction of DalP and DaiP-d14 resulted in the formation of only one mono-nitro PAH isomer product. The direct-acting mutagenicity of the products increased the most after NO3/N2O5 exposure, particularly for BkF-d12 in which the formation of dinitro- PAHs was observed. In addition, the degradation of particulate matter (PM)-bound PAHs by heterogeneous reaction with OH radicals, O3, NO3/N2O5 was also studied. Ambient PM samples collected from Beijing, China and Riverside, California were exposed in an indoor chamber under simulated trans-Pacific atmospheric transport conditions and the formation of NPAHs was studied. NPAHs were most effectively formed during the NO3/N2O5 exposure and, for all exposures, there was no significant formation of 2-nitrofluoranthene or 2-nitropyrene, suggesting that heterogeneous reactions predominated. The importance of this research with respect to atmospheric long-range transport of PM-bound PAHs and heterogeneous reaction of PAHs on terrestrial surfaces will be discussed.

  12. Land Use Effects on Atmospheric C-13 Imply a Sizable Terrestrial CO2 Sink in Tropical Latitudes

    NASA Technical Reports Server (NTRS)

    Townsend, Alan R.; Asner, Gregory P.; Tans, Pieter P.; White, James W. C.

    2000-01-01

    Records of atmospheric CO2 and 13-CO2, can be used to distinguish terrestrial vs. oceanic exchanges of CO2 with the atmosphere. However, this approach has proven difficult in the tropics, partly due to extensive land conversion from C-3 to C-4 vegetation. We estimated the effects of such conversion on biosphere-atmosphere C-13 exchange for 1991 through 1999, and then explored how this 'land-use disequilibrium' altered the partitioning of net atmospheric CO2 exchanges between ocean and land using NOAA-CMDL data and a 2D, zonally averaged atmospheric transport model. Our results show sizable CO2 uptake in C-3-dominated tropical regions in seven of the nine years; 1997 and 1998, which included a strong ENSO event, are near neutral. Since these fluxes include any deforestation source, our findings imply either that such sources are smaller than previously estimated, and/or the existence of a large terrestrial CO2 sink in equatorial latitudes.

  13. Early MAVEN results on the Mars Upper Atmosphere and Atmospheric Loss to Space

    NASA Astrophysics Data System (ADS)

    Jakosky, B. M.; Grebowsky, J. M.; Luhmann, J. G.

    2015-10-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft went into orbit around Mars on 21 September 2014. After a commissioning phase that included science observations of Mars and of Comet Siding Spring during its close approach, its primary science phase began on 16 November 2014 and will run for a full Earth year, until November 2015. Early results on structure, composition and dynamics of the upper atmosphere and on escape to space will be presented.

  14. Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish

    PubMed Central

    Dahl, Tais W.; Hammarlund, Emma U.; Anbar, Ariel D.; Bond, David P. G.; Gill, Benjamin C.; Gordon, Gwyneth W.; Knoll, Andrew H.; Nielsen, Arne T.; Schovsbo, Niels H.; Canfield, Donald E.

    2010-01-01

    The evolution of Earths biota is intimately linked to the oxygenation of the oceans and atmosphere. We use the isotopic composition and concentration of molybdenum (Mo) in sedimentary rocks to explore this relationship. Our results indicate two episodes of global ocean oxygenation. The first coincides with the emergence of the Ediacaran fauna, including large, motile bilaterian animals, ca. 550560million year ago (Ma), reinforcing previous geochemical indications that Earth surface oxygenation facilitated this radiation. The second, perhaps larger, oxygenation took place around 400Ma, well after the initial rise of animals and, therefore, suggesting that early metazoans evolved in a relatively low oxygen environment. This later oxygenation correlates with the diversification of vascular plants, which likely contributed to increased oxygenation through the enhanced burial of organic carbon in sediments. It also correlates with a pronounced radiation of large predatory fish, animals with high oxygen demand. We thereby couple the redox history of the atmosphere and oceans to major events in animal evolution. PMID:20884852

  15. Requirements for the early atmosphere of Mars from nitrogen isotope ratios

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1993-01-01

    The N escape models of Fox and Dalgarno and Fox required the presence of a dense, early CO2 atmosphere to inhibit fractionation of the N isotopes N-15 and N-14. The computed photochemical escape fluxes are so large at the present that the isotope ratio measured by Viking (about 1.62x terrestrial) can be produced in about 1.5 b.y. This model was refined in several ways. It was updated to incorporate the variation of the escape fluxes with increases in the solar fluxes at earlier times according to the model of Zahnle and Walker. As expected, this exacerbates the problem with overfractionation, but not greatly. Most of the escape and fractionation of the N occurs in the last 1.5 b.y., when the solar flux was only slightly different from the present. The dense early atmosphere must persist only a bit longer in order to reproduce the measured isotope ratio. The model was also modified to take into account changes in the O mixing ratio with time in the past, assuming that the O abundance is proportional to the square root of the solar flux. Although the production rate of O from photodissociation of CO2 scales as the solar flux, the strength of the winds and other mixing processes also increases with the solar flux, resulting in possibly more effective transport of O to the lower atmosphere where it is destroyed by catalytic and three-body recombination mechanisms.

  16. A carbon dioxide/methane greenhouse atmosphere on early Mars

    NASA Technical Reports Server (NTRS)

    Brown, L. L.; Kasting, J. F.

    1993-01-01

    One explanation for the formation of fluvial surface features on early Mars is that the global average surface temperature was maintained at or above the freezing point of water by the greenhouse warming of a dense CO2 atmosphere; however, Kasting has shown that CO2 alone is insufficient because the formation of CO2 clouds reduces the magnitude of the greenhouse effect. It is possible that other gases, such as NH3 and CH4, were present in the early atmosphere of Mars and contributed to the greenhouse effect. Kasting et al. investigated the effect of NH3 in a CO2 atmosphere and calculated that an NH3 mixing ratio of approximately 5 x 10 (exp -4) by volume, combined with a CO2 partial pressure of 4-5 bar, could generate a global average surface temperature of 273 K near 3.8 b.y. ago when the fluvial features are believed to have formed. Atmospheric NH3 is photochemically converted to N2 by ultraviolet radiation at wavelengths shortward of 230 nm; maintenance of sufficient NH3 concentrations would therefore require a source of NH3 to balance the photolytic destruction. We have used a one-dimensional photochemical model to estimate the magnitude of the NH3 source required to maintain a given NH3 concentration in a dense CO2 atmosphere. We calculate that an NH3 mixing ratio of 10(exp -4) requires a flux of NH3 on the order of 10(exp 12) molecules /cm-s. This figure is several orders of magnitude greater than estimates of the NH3 flux on early Mars; thus it appears that NH3 with CO2 is not enough to keep early Mars warm.

  17. Contrasting roles of interception and transpiration in the hydrological cycle - Part 1: Simple Terrestrial Evaporation to Atmosphere Model

    NASA Astrophysics Data System (ADS)

    Wang-Erlandsson, L.; van der Ent, R. J.; Gordon, L. J.; Savenije, H. H. G.

    2014-03-01

    Terrestrial evaporation consists of biophysical (i.e., transpiration) and physical fluxes (i.e., interception, soil moisture, and open water). The partitioning between them depends on both climate and the land surface, and determines the time scale of evaporation. However, few land-surface models have analysed and evaluated evaporative partitioning based on land use, and no studies have examined their subsequent paths in the atmosphere. This paper constitutes the first of two companion papers that investigate the contrasting effects of interception and transpiration in the hydrological cycle. Here, we present STEAM (Simple Terrestrial Evaporation to Atmosphere Model) used to produce partitioned evaporation and analyse the characteristics of different evaporation fluxes on land. STEAM represents 19 land-use types (including irrigated land) at sub-grid level with a limited set of parameters, and includes phenology and stress functions to respond to changes in climate conditions. Using ERA-Interim reanalysis forcing for the years 1999-2008, STEAM estimates a mean global terrestrial evaporation of 73 800 km3 year-1, with a transpiration ratio of 59%. We show that the terrestrial residence time scale of transpiration (days to months) has larger inter-seasonal variation and is substantially longer than that of interception (hours). Furthermore, results from an offline land-use change experiment illustrate that land-use change may lead to significant changes in evaporative partitioning even when total evaporation remains similar. In agreement with previous research, our simulations suggest that the vegetation's ability to transpire by retaining and accessing soil moisture at greater depth is critical for sustained evaporation during the dry season. Despite a relatively simple model structure, validation shows that STEAM produces realistic evaporative partitioning and hydrological fluxes that compare well with other global estimates over different locations, seasons and land-use types. We conclude that the simulated evaporation partitioning by STEAM is useful for understanding the links between land use and water resources, and can with benefit be employed for atmospheric moisture tracking.

  18. The Role of Hydrogen in Determining the Stability of CO2 Atmospheres of Terrestrial Exoplanets Around M Dwarfs

    NASA Astrophysics Data System (ADS)

    Gao, Peter; Hu, Renyu; Robinson, Tyler D.; Yung, Yuk L.

    2014-11-01

    The recent discovery of terrestrial worlds in the Habitable Zones of M Dwarfs necessitates a more intensive investigation of the properties of these planets. One major feature of certain M Dwarfs is their high fluxes of EUV radiation, which photolyzes CO2, an important greenhouse gas that should be abundant on rocky worlds. This photolytic destruction of CO2 can be countered by HOx chemistry: photolysis of HOx species by NUV radiation generates OH, which reacts with CO to regenerate CO2. These processes are balanced around Sun-like stars such that Venus and Mars can maintain CO2-dominated atmospheres. However, M Dwarfs tend to have much lower NUV/EUV flux ratios, which could prevent the formation of significant CO2 atmospheres on any planets they may host. In this study, we evaluate the properties of CO2 atmospheres surrounding an Earth-massed, Earth-sized exoplanet in orbit of an M Dwarf using a 1D photochemical kinetics model. We consider an atmosphere similar in composition to that of Mars, but scaled to have a surface pressure of 1 bar. We choose to focus on Mars-like atmospheres rather than Earth-like ones, as Earth's atmosphere has been altered through biological sources and sinks and the presence of a large liquid water ocean, which are not necessarily present on terrestrial exoplanets. Our preliminary results show that the hydrogen content of the atmosphere is crucial in determining the ratio of CO2 to CO and O2. In particular, for a H2 mixing ratio identical to that of Mars 20-30 ppm), a steady state atmosphere is reached after 10 Gyr consisting of ~85% CO2, ~10% CO, and ~5% O2, with an ozone mixing ratio of ~0.01 ppm. In the extreme case where all hydrogen is lost to space, an atmosphere consisting of ~64% CO2, ~24% CO, and 12% O2 results, while ozone levels reach ~10 ppm. Finally, for H2 mixing ratios similar to that of Earth 0.5 ppm) and no atmospheric escape, a 49% CO2, 34% CO, 17% O2, and 0.1 ppm O3 atmosphere is possible. This not only points to the potential prevalence of abiotic O2 and O3 in M Dwarf exoplanet atmospheres, but also that hydrogen species, including H2O, are essential in determining the global atmospheric makeup of these planets despite their relatively low concentrations.

  19. Atmospheric composition and climate on the early Earth.

    PubMed

    Kasting, James F; Howard, M Tazewell

    2006-10-29

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85 degrees C. We argue, following others, that this interpretation is incorrect-the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot.A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. PMID:17008214

  20. Atmospheric composition and climate on the early Earth

    PubMed Central

    Kasting, James F; Howard, M. Tazewell

    2006-01-01

    Oxygen isotope data from ancient sedimentary rocks appear to suggest that the early Earth was significantly warmer than today, with estimates of surface temperatures between 45 and 85°C. We argue, following others, that this interpretation is incorrect—the same data can be explained via a change in isotopic composition of seawater with time. These changes in the isotopic composition could result from an increase in mean depth of the mid-ocean ridges caused by a decrease in geothermal heat flow with time. All this implies that the early Earth was warm, not hot. A more temperate early Earth is also easier to reconcile with the long-term glacial record. However, what triggered these early glaciations is still under debate. The Paleoproterozoic glaciations at approximately 2.4 Ga were probably caused by the rise of atmospheric O2 and a concomitant decrease in greenhouse warming by CH4. Glaciation might have occurred in the Mid-Archaean as well, at approximately 2.9 Ga, perhaps as a consequence of anti-greenhouse cooling by hydrocarbon haze. Both glaciations are linked to decreases in the magnitude of mass-independent sulphur isotope fractionation in ancient rocks. Studying both the oxygen and sulphur isotopic records has thus proved useful in probing the composition of the early atmosphere. PMID:17008214

  1. Terrestrial origin of viviparity in mesozoic marine reptiles indicated by early triassic embryonic fossils.

    PubMed

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction. PMID:24533127

  2. Terrestrial Origin of Viviparity in Mesozoic Marine Reptiles Indicated by Early Triassic Embryonic Fossils

    PubMed Central

    Motani, Ryosuke; Jiang, Da-yong; Tintori, Andrea; Rieppel, Olivier; Chen, Guan-bao

    2014-01-01

    Viviparity in Mesozoic marine reptiles has traditionally been considered an aquatic adaptation. We report a new fossil specimen that strongly contradicts this traditional interpretation. The new specimen contains the oldest fossil embryos of Mesozoic marine reptile that are about 10 million years older than previous such records. The fossil belongs to Chaohusaurus (Reptilia, Ichthyopterygia), which is the oldest of Mesozoic marine reptiles (ca. 248 million years ago, Early Triassic). This exceptional specimen captures an articulated embryo in birth position, with its skull just emerged from the maternal pelvis. Its headfirst birth posture, which is unlikely to be a breech condition, strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature. The unequivocally marine origin of viviparity is so far not known among amniotes, a subset of vertebrate animals comprising mammals and reptiles, including birds. Therefore, obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors. Viviparous land reptiles most likely appeared much earlier than currently thought, at least as early as the recovery phase from the end-Permian mass extinction. PMID:24533127

  3. Using atmospheric observations to evaluate the spatiotemporal variability of CO2 fluxes simulated by terrestrial biospheric models

    NASA Astrophysics Data System (ADS)

    Fang, Y.; Michalak, A. M.; Shiga, Y. P.; Yadav, V.

    2014-12-01

    Terrestrial biospheric models (TBMs) are used to extrapolate local observations and process-level understanding of land-atmosphere carbon exchange to larger regions, and serve as predictive tools for examining carbon-climate interactions. Understanding the performance of TBMs is thus crucial to the carbon cycle and climate science communities. In this study, we present and assess an approach to evaluating the spatiotemporal patterns, rather than aggregated magnitudes, of net ecosystem exchange (NEE) simulated by TBMs using atmospheric CO2 measurements. The approach is based on statistical model selection implemented within a high-resolution atmospheric inverse model. Using synthetic data experiments, we find that current atmospheric observations are sensitive to the underlying spatiotemporal flux variability at sub-biome scales for a large portion of North America, and that atmospheric observations can therefore be used to evaluate simulated spatiotemporal flux patterns as well as to differentiate between multiple competing TBMs. Experiments using real atmospheric observations and four prototypical TBMs further confirm the applicability of the method, and demonstrate that the performance of TBMs in simulating the spatiotemporal patterns of NEE varies substantially across seasons, with best performance during the growing season and more limited skill during transition seasons. This result is consistent with previous work showing that the ability of TBMs to model flux magnitudes is also seasonally-dependent. Overall, the proposed approach provides a new avenue for evaluating TBM performance based on sub-biome-scale flux patterns, presenting an opportunity for assessing and informing model development using atmospheric observations.

  4. Hydrogen-nitrogen greenhouse warming in Earth's early atmosphere.

    PubMed

    Wordsworth, Robin; Pierrehumbert, Raymond

    2013-01-01

    Understanding how Earth has sustained surface liquid water throughout its history remains a key challenge, given that the Sun's luminosity was much lower in the past. Here we show that with an atmospheric composition consistent with the most recent constraints, the early Earth would have been significantly warmed by H(2)-N(2) collision-induced absorption. With two to three times the present-day atmospheric mass of N(2) and a H(2) mixing ratio of 0.1, H(2)-N(2) warming would be sufficient to raise global mean surface temperatures above 0°C under 75% of present-day solar flux, with CO(2) levels only 2 to 25 times the present-day values. Depending on their time of emergence and diversification, early methanogens may have caused global cooling via the conversion of H(2) and CO(2) to CH(4), with potentially observable consequences in the geological record. PMID:23288536

  5. Quantitative Hydraulic Models Of Early Land Plants Provide Insight Into Middle Paleozoic Terrestrial Paleoenvironmental Conditions

    NASA Astrophysics Data System (ADS)

    Wilson, J. P.; Fischer, W. W.

    2010-12-01

    Fossil plants provide useful proxies of Earth’s climate because plants are closely connected, through physiology and morphology, to the environments in which they lived. Recent advances in quantitative hydraulic models of plant water transport provide new insight into the history of climate by allowing fossils to speak directly to environmental conditions based on preserved internal anatomy. We report results of a quantitative hydraulic model applied to one of the earliest terrestrial plants preserved in three dimensions, the ~396 million-year-old vascular plant Asteroxylon mackei. This model combines equations describing the rate of fluid flow through plant tissues with detailed observations of plant anatomy; this allows quantitative estimates of two critical aspects of plant function. First and foremost, results from these models quantify the supply of water to evaporative surfaces; second, results describe the ability of plant vascular systems to resist tensile damage from extreme environmental events, such as drought or frost. This approach permits quantitative comparisons of functional aspects of Asteroxylon with other extinct and extant plants, informs the quality of plant-based environmental proxies, and provides concrete data that can be input into climate models. Results indicate that despite their small size, water transport cells in Asteroxylon could supply a large volume of water to the plant's leaves--even greater than cells from some later-evolved seed plants. The smallest Asteroxylon tracheids have conductivities exceeding 0.015 m^2 / MPa * s, whereas Paleozoic conifer tracheids do not reach this threshold until they are three times wider. However, this increase in conductivity came at the cost of little to no adaptations for transport safety, placing the plant’s vegetative organs in jeopardy during drought events. Analysis of the thickness-to-span ratio of Asteroxylon’s tracheids suggests that environmental conditions of reduced relative humidity (<20%) combined with elevated temperatures (>25°C) could cause sufficient cavitation to reduce hydraulic conductivity by 50%. This suggests that the Early Devonian environments that supported the earliest vascular plants were not subject to prolonged midseason droughts, or, alternatively, that the growing season was short. This places minimum constraints on water availability (e.g., groundwater hydration, relative humidity) in locations where Asteroxylon fossils are found; these environments must have had high relative humidities, comparable to tropical riparian environments. Given these constraints, biome-scale paleovegetation models that place early vascular plants distal to water sources can be revised to account for reduced drought tolerance. Paleoclimate proxies that treat early terrestrial plants as functionally interchangeable can incorporate physiological differences in a quantitatively meaningful way. Application of hydraulic models to fossil plants provides an additional perspective on the 475 million-year history of terrestrial photosynthetic environments and has potential to corroborate other plant-based paleoclimate proxies.

  6. Spectral identification of abiotic O2 buildup from early runaways and rarefied atmospheres

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Meadows, Victoria; Domagal-Goldman, Shawn; Arney, Giada; Robinson, Tyler D.; Luger, Rodrigo; Barnes, Rory

    2016-01-01

    The spectral detection of oxygen (O2) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive on planets with Earth-like redox buffers and because significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that significant O2 may build-up in terrestrial atmospheres through (1) photochemical channels or (2) through the escape of hydrogen. We focus on the latter category here. Significant amounts of abiotic O2 could remain in the atmospheres of planets in the habitable zones of late type stars, where an early runaway greenhouse and massive hydrogen escape during the pre-main-sequence phase could have irreversibly oxidized the crust and mantle (Luger & Barnes 2015). Additionally, it has been hypothesized that O2 could accumulate in the atmospheres of planets with sufficiently low abundances of non-condensable gases such as N2 where water would not be cold trapped in the troposphere, leading to H-escape from UV photolysis in a wet stratosphere (Wordsworth & Pierrehumbert 2014). We self-consistently model the climate, photochemistry, and spectra of both rarefied and post-runaway, high-O2 atmospheres. Because an early runaway might not have lasted long enough for the entire water inventory to escape, we explore both completely desiccated scenarios and cases where a surface ocean remains. We find "habitable" surface conditions for a wide variety of oxygen abundances, atmospheric masses, and CO2 mixing ratios. If O2 builds up from massive or sustained H escape, the O2 abundance should be very high, and could be spectrally indicated by the presence of O2-O2 (O4) collisionally-induced absorption (CIA) features. We generate synthetic direct-imaging and transit transmission spectra of these atmospheres and calculate the strength of the UV/Visible and NIR O4 features. We find that while both the UV/Visible and NIR O4 features are strong in the radiance spectra of very high-O2 atmospheres, only the NIR O4 features are strong in transmission spectra. We also conclude that detection of N2-N2 CIA near 4.2 μm in transmission or direct-imaging spectra could rule out O2 origination from H-escape from thin atmospheres.

  7. Spectral identification of abiotic O2 buildup from early runaways and rarefied atmospheres

    NASA Astrophysics Data System (ADS)

    Schwieterman, Edward; Meadows, Victoria; Domagal-Goldman, Shawn; Arney, Giada; Luger, Rodrigo; Barnes, Rory

    2015-11-01

    The spectral detection of oxygen (O2) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive on planets with Earth-like redox buffers and because significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that significant O2 may build-up in terrestrial planet atmospheres through (1) photochemical channels or (2) through massive hydrogen escape. We focus on the latter category here. Significant amounts of abiotic O2 could remain in the atmospheres of planets in the habitable zones of late type stars, where an early runaway greenhouse and massive hydrogen escape during the pre-main-sequence phase could have irreversibly oxidized the crust and mantle (Luger & Barnes 2015). Additionally, it has been hypothesized that O2 could accumulate in the atmospheres of planets with sufficiently low abundances of noncondensable gases such as N2 where water would not be cold trapped in the troposphere, leading to H-escape from UV photolysis in a wet stratosphere (Wordsworth & Pierrehumbert 2014). We self-consistently model the climate, photochemistry, and spectra of both rarefied and post-runaway, high-O2 atmospheres. Because an early runaway might not have lasted long enough for the entire water inventory to have escaped, we explore both completely desiccated scenarios and cases where a surface ocean remains. We find “habitable” surface conditions for a wide variety of oxygen abundances, atmospheric masses, and CO2 mixing ratios. If O2 builds up from H escape, the O2 abundance should be very high, and could be spectrally indicated by the presence of O2 collisionally-induced absorption (CIA) features. We generate synthetic direct-imaging and transit transmission spectra of these atmospheres and calculate the strength of the UV/Visible and NIR O2 CIA features. We find that while both the UV/Visible and NIR O2 CIA features are strong in the direct-imaging spectra of very high-O2 atmospheres, only the NIR O2 CIA features are significant in transmission spectra. We also conclude that detection of N2-N2 CIA in transmission or direct-imaging spectra could rule out O2 origination from H-escape from thin atmospheres.

  8. Photochemistry in terrestrial exoplanet atmospheres. III. Photochemistry and thermochemistry in thick atmospheres on super Earths and mini Neptunes

    SciTech Connect

    Hu, Renyu; Seager, Sara

    2014-03-20

    Some super Earths and mini Neptunes will likely have thick atmospheres that are not H{sub 2}-dominated. We have developed a photochemistry-thermochemistry kinetic-transport model for exploring the compositions of thick atmospheres on super Earths and mini Neptunes, applicable for both H{sub 2}-dominated atmospheres and non-H{sub 2}-dominated atmospheres. Using this model to study thick atmospheres for wide ranges of temperatures and elemental abundances, we classify them into hydrogen-rich atmospheres, water-rich atmospheres, oxygen-rich atmospheres, and hydrocarbon-rich atmospheres. We find that carbon has to be in the form of CO{sub 2} rather than CH{sub 4} or CO in a H{sub 2}-depleted water-dominated thick atmosphere and that the preferred loss of light elements from an oxygen-poor carbon-rich atmosphere leads to the formation of unsaturated hydrocarbons (C{sub 2}H{sub 2} and C{sub 2}H{sub 4}). We apply our self-consistent atmosphere models to compute spectra and diagnostic features for known transiting low-mass exoplanets GJ 1214 b, HD 97658 b, and 55 Cnc e. For GJ 1214 b, we find that (1) C{sub 2}H{sub 2} features at 1.0 and 1.5 μm in transmission and C{sub 2}H{sub 2} and C{sub 2}H{sub 4} features at 9-14 μm in thermal emission are diagnostic for hydrocarbon-rich atmospheres; (2) a detection of water-vapor features and a confirmation of the nonexistence of methane features would provide sufficient evidence for a water-dominated atmosphere. In general, our simulations show that chemical stability has to be taken into account when interpreting the spectrum of a super Earth/mini Neptune. Water-dominated atmospheres only exist for carbon to oxygen ratios much lower than the solar ratio, suggesting that this kind of atmospheres could be rare.

  9. Hf-W chronology of the accretion and early evolution of asteroids and terrestrial planets

    NASA Astrophysics Data System (ADS)

    Kleine, Thorsten; Touboul, Mathieu; Bourdon, Bernard; Nimmo, Francis; Mezger, Klaus; Palme, Herbert; Jacobsen, Stein B.; Yin, Qing-Zhu; Halliday, Alexander N.

    2009-09-01

    The 182Hf- 182W systematics of meteoritic and planetary samples provide firm constraints on the chronology of the accretion and earliest evolution of asteroids and terrestrial planets and lead to the following succession and duration of events in the earliest solar system. Formation of Ca,Al-rich inclusions (CAIs) at 4568.3 0.7 Ma was followed by the accretion and differentiation of the parent bodies of some magmatic iron meteorites within less than 1 Myr. Chondrules from H chondrites formed 1.7 0.7 Myr after CAIs, about contemporaneously with chondrules from L and LL chondrites as shown by their 26Al- 26Mg ages. Some magmatism on the parent bodies of angrites, eucrites, and mesosiderites started as soon as 3 Myr after CAI formation and may have continued until 10 Myr. A similar timescale is obtained for the high-temperature metamorphic evolution of the H chondrite parent body. Thermal modeling combined with these age constraints reveals that the different thermal histories of meteorite parent bodies primarily reflect their initial abundance of 26Al, which is determined by their accretion age. Impact-related processes were important in the subsequent evolution of asteroids but do not appear to have induced large-scale melting. For instance, Hf-W ages for eucrite metals postdate CAI formation by 20 Myr and may reflect impact-triggered thermal metamorphism in the crust of the eucrite parent body. Likewise, the Hf-W systematics of some non-magmatic iron meteorites were modified by impact-related processes but the timing of this event(s) remains poorly constrained. The strong fractionation of lithophile Hf from siderophile W during core formation makes the Hf-W system an ideal chronometer for this major differentiation event. However, for larger planets such as the terrestrial planets the calculated Hf-W ages are particularly sensitive to the occurrence of large impacts, the degree to which impactor cores re-equilibrated with the target mantle during large collisions, and changes in the metal-silicate partition coefficients of W due to changing fO 2 in differentiating planetary bodies. Calculated core formation ages for Mars range from 0 to 20 Myr after CAI formation and currently cannot distinguish between scenarios where Mars formed by runaway growth and where its formation was more protracted. Tungsten model ages for core formation in Earth range from 30 Myr to >100 Myr after CAIs and hence do not provide a unique age for the formation of Earth. However, the identical 182W/ 184W ratios of the lunar and terrestrial mantles provide powerful evidence that the Moon-forming giant impact and the final stage of Earth's core formation occurred after extinction of 182Hf (i.e., more than 50 Myr after CAIs), unless the Hf/W ratios of the bulk silicate Moon and Earth are identical to within less than 10%. Furthermore, the identical 182W/ 184W of the lunar and terrestrial mantles is difficult to explain unless either the Moon consists predominantly of terrestrial material or the W in the proto-lunar magma disk isotopically equilibrated with the Earth's mantle. Hafnium-tungsten chronometry also provides constraints on the duration of magma ocean solidification in terrestrial planets. Variations in the 182W/ 184W ratios of martian meteorites reflect an early differentiation of the martian mantle during the effective lifetime of 182Hf. In contrast, no 182W variations exist in the lunar mantle, demonstrating magma ocean solidification later than 60 Myr, in agreement with 147Sm- 143Nd ages for ferroan anorthosites. The Moon-forming giant impact most likely erased any evidence of a prior differentiation of Earth's mantle, consistent with a 146Sm- 142Nd age of 50-200 Myr for the earliest differentiation of Earth's mantle. However, the Hf-W chronology of the formation of Earth's core and the Moon-forming impact is difficult to reconcile with the preservation of 146Sm- 142Nd evidence for an early (<30 Myr after CAIs) differentiation of a chondritic Earth's mantle. Instead, the combined 182W- 142Nd evidence suggests that bulk Earth may have superchondritic Sm/Nd and Hf/W ratios, in which case formation of its core must have terminated more than 42 Myr after formation of CAIs, consistent with the Hf-W age for the formation of the Moon.

  10. Magma ocean influence on early atmosphere mass and composition

    NASA Astrophysics Data System (ADS)

    Hirschmann, Marc M.

    2012-08-01

    Redox conditions in magma oceans (MOs) have a key influence on the mass and composition of Earth's early atmosphere. If the shallow part of the MO is oxidized, it may be overlain by an H2O-CO2 atmosphere, but if the near-surface magma is close to equilibrium with Fe-rich alloy, then the atmosphere will consist chiefly of H2, H2O, and CO, and on cooling will be rich in CH4. Although MOs are intimately associated with core-forming metal, the redox conditions in their shallow parts are not necessarily reducing. The magmatic Fe3+/FeT ratio is set by equilibrium with metal at depth and homogenized through the magma column by convection. Indirect evidence suggests that the Fe3+/FeT ratio of magmas in equilibrium with alloy at high pressure is greater than at low pressure, such that the shallow part of the MO may be comparatively oxidized and coexist with an atmosphere consisting chiefly of H2O and CO2. The mass of the atmosphere is dictated by the concentrations of volatile-species dissolved in the magma, which in turn are determined by partitioning between magma and alloy. Very strong partitioning of C into alloy may capture most of the carbon delivered to the growing planet, leaving behind a C-poor bulk silicate Earth (BSE) and a C-poor atmosphere. However, modest solubility of CH4 in the magma may allow the BSE to retain significant C. Alternatively, if partitioning of C into alloy is extreme but the fraction of metal equilibrated with the MO is small, the alloy may become saturated with diamond. Floatation of diamond in the MO may retain a substantial inventory of C in the early mantle. BSE C may also have been replenished in a late veneer. Following segregation of metal to the core, crystallization of the MO may have prompted precipitation of C-rich phases (graphite, diamond, carbide), limiting the C in the early atmosphere and creating a substantial interior C inventory that may account for the large fraction of BSE carbon in the mantle today. Such precipitation could have occurred owing to a combination of the redox evolution of the crystallizing MO and cooling.

  11. Late Paleocene-early Eocene carbon isotope stratigraphy from a near-terrestrial tropical section and antiquity of Indian mammals

    NASA Astrophysics Data System (ADS)

    Samanta, A.; Sarkar, A.; Bera, M. K.; Rai, Jyotsana; Rathore, S. S.

    2013-02-01

    Late Paleocene to early Eocene (~56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene-Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope ( δ 13C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. δ 13C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the `out of India' hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

  12. Responses of global terrestrial evapotranspiration to climate change and increasing atmospheric CO2 in the 21st century

    NASA Astrophysics Data System (ADS)

    Pan, Shufen; Tian, Hanqin; Dangal, Shree R. S.; Yang, Qichun; Yang, Jia; Lu, Chaoqun; Tao, Bo; Ren, Wei; Ouyang, Zhiyun

    2015-01-01

    Quantifying the spatial and temporal patterns of the water lost to the atmosphere through land surface evapotranspiration (ET) is essential for understanding the global hydrological cycle, but remains much uncertain. In this study, we use the Dynamic Land Ecosystem Model to estimate the global terrestrial ET during 2000-2009 and project its changes in response to climate change and increasing atmospheric CO2 under two IPCC SRES scenarios (A2 and B1) during 2010-2099. Modeled results show a mean annual global terrestrial ET of about 549 (545-552) mm yr-1 during 2000-2009. Relative to the 2000s, global terrestrial ET for the 2090s would increase by 30.7 mm yr-1 (5.6%) and 13.2 mm yr-1 (2.4%) under the A2 and B1 scenarios, respectively. About 60% of global land area would experience increasing ET at rates of over 9.5 mm decade-1 over the study period under the A2 scenario. The Arctic region would have the largest ET increase (16% compared with the 2000s level) due to larger increase in temperature than other regions. Decreased ET would mainly take place in regions like central and western Asia, northern Africa, Australia, eastern South America, and Greenland due to declines in soil moisture and changing rainfall patterns. Our results indicate that warming temperature and increasing precipitation would result in large increase in ET by the end of the 21st century, while increasing atmospheric CO2 would be responsible for decrease in ET, given the reduction of stomatal conductance under elevated CO2.

  13. The non-homogeneous accumulation model for terrestrial planet formation and the consequences for the atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Turekian, K. K.; Clark, S. P., Jr.

    1975-01-01

    The nonhomogeneous-accumulation model for the formation of the terrestrial planets is described, and its consequences for the formation of the Venusian atmosphere are assayed in the context of our knowledge of the composition of the earth and carbonaceous chondrites. The relative abundances of the low-temperature condensibles in the reservoirs at the earth's surface are applied to Venus. Although carbonaceous chondrites show similar properties for the chemically bound elements, they show large deficiencies for the rare gases. The major gases on Venus, by volume, are predicted to be 98.12% CO2, 1.86% N2 and 0.02% Ar-40.

  14. Mentors, networks, and resources for early career female atmospheric scientists

    NASA Astrophysics Data System (ADS)

    Hallar, A. G.; Avallone, L. M.; Edwards, L. M.; Thiry, H.; Ascent

    2011-12-01

    Atmospheric Science Collaborations and Enriching NeTworks (ASCENT) is a workshop series designed to bring together early career female scientists in the field of atmospheric science and related disciplines. ASCENT is a multi-faceted approach to retaining these junior scientists through the challenges in their research and teaching career paths. During the workshop, senior women scientists discuss their career and life paths. They also lead seminars on tools, resources and methods that can help early career scientists to be successful. Networking is a significant aspect of ASCENT, and many opportunities for both formal and informal interactions among the participants (of both personal and professional nature) are blended in the schedule. The workshops are held in Steamboat Springs, Colorado, home of a high-altitude atmospheric science laboratory - Storm Peak Laboratory, which also allows for nearby casual outings and a pleasant environment for participants. Near the conclusion of each workshop, junior and senior scientists are matched in mentee-mentor ratios of two junior scientists per senior scientist. An external evaluation of the three workshop cohorts concludes that the workshops have been successful in establishing and expanding personal and research-related networks, and that seminars have been useful in creating confidence and sharing resources for such things as preparing promotion and tenure packages, interviewing and negotiating job offers, and writing successful grant proposals.

  15. Multiple Tectonic Regimes and Diverging Geologic Histories of Terrestrial Planets: The Importance of the Early Years

    NASA Astrophysics Data System (ADS)

    Weller, M. B.; Lenardic, A.

    2013-12-01

    We use 3D mantle convection and planetary tectonics simulations to explore the links between tectonic regimes, the age of a planet, and its surface evolution. We demonstrate that the tectonic regime of a planet is dependant on its thermal and climatic evolution. A young planet with a high degree of internal heating has a strong susceptibility to climate-induced transitions in tectonic styles. The amplitude of a long lived surface temperature perturbation needed to initiate a transition from a mobile- to a stagnant-lid mode of tectonics decreases with increasing degrees of internal heating. As surface temperatures increase, episodic convection occurs over a larger range of lid strengths, suggesting that young and high temperature planetary bodies have a higher potential to exist in a long-lived mode of episodic tectonics. Once the system transitions into a stagnant-lid, the reverse transition is not attainable by a return to the original surface temperature, which indicates that the climate-tectonic system is bi-stable [multiple tectonic states are possible for the same parameter values]. As a planet ages, the system becomes increasingly insensitive to surface temperature induced transitions after ~30 - 50% of the original radiogenics decay. For a planet to transition from mobile- into episodic-, or stagnant-lid modes through the mechanism of increasing surface temperatures, the implication is that the change would have to occur early in its evolution, within the first 1-2 giga years. While the sensitivity to climatic perturbations decreases with the age of the planet, decreasing internal heat production can usher in a transition in tectonic regimes from a stagnant-lid state, into an episodic- and finally mobile-/sluggish-lid regimes. The implications are that terrestrial worlds can alternate between multiple tectonic states over giga-year timescales. The implications for the early Earth and Earth-Venus differences will be discussed.

  16. Heat flow vs. atmospheric greenhouse on early Mars

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Postawko, S. E.

    1991-01-01

    Researchers derived a quantitative relationship between the effectiveness of an atmospheric greenhouse and internal heat flow in producing the morphological differences between earlier and later Martian terrains. The derivation is based on relationships previously derived by other researchers. The reasoning may be stated as follows: the CO2 mean residence time in the Martian atmosphere is almost certainly much shorter than the total time span over which early climate differences are thought to have been sustained. Therefore, recycling of previously degassed CO2 quickly becomes more important than the ongoing supply of juvenile CO2. If so, then the atmospheric CO2 pressure, and thereby the surface temperature, may be approximated mathematically as a function of the total degassed CO2 in the atmosphere plus buried material and the ratio of the atmospheric and regolith mean residence times. The latter ratio can also be expressed as a function of heat flow. Hence, it follows that the surface temperature may be expressed as a function of heat flow and the total amount of available CO2. However, the depth to the water table can simultaneously be expressed as a function of heat flow and the surface temperature (the boundary condition). Therefore, for any given values of total available CO2 and regolith conductivity, there exist coupled independent equations which relate heat flow, surface temperature, and the depth to the water table. This means we can now derive simultaneous values of surface temperature and the depth of the water table for any value of the heat flow. The derived relationship is used to evaluate the relative importance of the atmospheric greenhouse effect and the internal regolith thermal gradient in producing morphological changes for any value of the heat flow, and to assess the absolute importance of each of the values of the heat flow which are thought to be reasonable on independent geophysical grounds.

  17. The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns

    USGS Publications Warehouse

    Weems, R.E.

    1992-01-01

    A catastrophic terminal Triassic extinction event among terrestrial vertebrates is not supported by available evidence. The current model for such an extinction is based on at least eight weak or untenable assumptions: (1) a terminal Triassic extinction-inducing asteroid impact occurred, (2) a terminal Triassic synchronous mass extinction of terrestrial vertebrates occurred, (3) a concurrent terminal Triassic marine extinction occurred, (4) all terrestrial vertebrate families have similar diversities and ecologies, (5) changes in familial diversity can be gauged accurately from the known fossil record, (6) extinction of families can be compared through time without normalizing for changes in familial diversity through time, (7) extinction rates can be compared without normalizing for differing lengths of geologic stages, and (8) catastrophic mass extinctions do not select for small size. These assumptions have resulted in unsupportable and (or) erroneous conclusions. Carboniferous through Early Jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal Cretaceous event. Only the Serpukhovian (mid Carboniferous) extinction event shows strong analogy to the terminal Cretaceous event. Available data suggest no terminal Triassic extinction anomaly, but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the Triassic and earliest Jurassic. ?? 1992.

  18. Changes in the terrestrial atmosphere-ionosphere-magnetosphere system due to ion propulsion for solar power satellite placement

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Grebowsky, J. M.

    1980-01-01

    In order to construct solar power satellites using earth-based materials, sections of a satellite must be lifted from low earth to geosynchronous orbit. The most plausible method of accomplishing this task is by means of ion propulsion based on the relatively abundant terrestrial atmospheric component, Ar. The proposed propulsion system will release a dense beam of about 5 keV Ar(+). The total amount of Ar(+) injected in transporting the components for each solar power satellite is comparable to the total ion content of the ionosphere-plasmasphere system while the total energy injected is larger than that of this system. Preliminary estimates are given of the effects massive Ar(+) injections have on the ionosphere-plasmasphere system with specific emphasis on potential communications disruptions. The effects stem from direct Ar(+) precipitation into the atmosphere and from Ar(+) beam induced precipitation of MeV radiation belt protons.

  19. Changes in the terrestrial atmosphere-ionosphere-magnetosphere system due to ion propulsion for solar power satellite placement

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Grebowsky, J. M.

    1979-01-01

    Preliminary estimates of the effects massive Ar(+) injections on the ionosphere-plasmasphere system with specific emphasis on potential communications disruptions are given. The effects stem from direct Ar(+) precipitation into the atmosphere and from Ar(+) beam induced precipitation of MeV radiation belt protons. These injections result from the construction of Solar Power Satellites using earth-based materials in which sections of a satellite must be lifted from low earth to geosynchronous orbit by means of ion propulsion based on the relatively abundant terrestrial atmospheric component, Ar. The total amount of Ar(+) injected in transporting the components for each Solar Power Satellite is comparable to the total ion content of the ionosphere-plasmasphere system while the total energy injected is larger than that of this system. It is suggested that such effects may be largely eliminated by using lunar-based rather than earth-based satellite construction materials.

  20. The armoured dissorophid Cacops from the Early Permian of Oklahoma and the exploitation of the terrestrial realm by amphibians.

    PubMed

    Reisz, Robert R; Schoch, Rainer R; Anderson, Jason S

    2009-07-01

    Cacops, one of the most distinctive Paleozoic amphibians, is part of a clade of dissorophoid temnospondyls that diversified in the equatorial region of Pangea during the Late Carboniferous and Early Permian, persisting into the Late Permian in Central Russia and China. Dissorophids were a successful group of fully terrestrial, often spectacularly armoured predators, the only amphibians apparently able to coexist with amniotes when the latter started to dominate terrestrial ecosystems. In this paper, we describe excellent new skulls from the Early Permian of Oklahoma attributed to Cacops, Cacops morrisi sp. nov. and provide for the first time detailed information about this iconic dissorophid. These specimens show anatomical and ontogenetic features that will impact on future studies on the evolution of terrestriality in tetrapods. For example, the large, posteriorly closed tympanic embayment has fine striations on an otherwise smooth surface, documenting the oldest known clear evidence for the presence of a tympanic membrane in the fossil record, a structure that is used for hearing airborne sound in extant tetrapods. The skull of C. morrisi also has several features associated with predatory behaviour, indicating that this dissorophid may have been one of the top terrestrial predators of its time. PMID:19347261

  1. The armoured dissorophid Cacops from the Early Permian of Oklahoma and the exploitation of the terrestrial realm by amphibians

    NASA Astrophysics Data System (ADS)

    Reisz, Robert R.; Schoch, Rainer R.; Anderson, Jason S.

    2009-07-01

    Cacops, one of the most distinctive Paleozoic amphibians, is part of a clade of dissorophoid temnospondyls that diversified in the equatorial region of Pangea during the Late Carboniferous and Early Permian, persisting into the Late Permian in Central Russia and China. Dissorophids were a successful group of fully terrestrial, often spectacularly armoured predators, the only amphibians apparently able to coexist with amniotes when the latter started to dominate terrestrial ecosystems. In this paper, we describe excellent new skulls from the Early Permian of Oklahoma attributed to Cacops, Cacops morrisi sp. nov. and provide for the first time detailed information about this iconic dissorophid. These specimens show anatomical and ontogenetic features that will impact on future studies on the evolution of terrestriality in tetrapods. For example, the large, posteriorly closed tympanic embayment has fine striations on an otherwise smooth surface, documenting the oldest known clear evidence for the presence of a tympanic membrane in the fossil record, a structure that is used for hearing airborne sound in extant tetrapods. The skull of C. morrisi also has several features associated with predatory behaviour, indicating that this dissorophid may have been one of the top terrestrial predators of its time.

  2. Multiple scattering of polarized light in planetary atmospheres. II - Sunlight reflected by terrestrial water clouds.

    NASA Technical Reports Server (NTRS)

    Hansen, J. E.

    1971-01-01

    The intensity and polarization of sunlight reflected by terrestrial water clouds are computed with the doubling method. The calculations illustrate that this method can be effectively used in problems involving strongly anisotropic phase matrices. The method can, therefore, be used to derive information about planetary clouds, including those of the earth, from polarimetric observations. The results of the computations indicate that the polarization is more sensitive than the intensity to cloud microstructure, such as particle size and shape.

  3. Mutli-Scale Synthesis and Terrestrial Model Intercomparison Project - A Systematic Approach for Evaluating Land-Atmosphere Flux Estimates

    NASA Astrophysics Data System (ADS)

    Huntzinger, D. N.; Post, W. M.; Schaefer, K. M.; Jacobson, A. R.; Schwalm, C. R.; Cook, R. B.; Michalak, A. M.; MsTMIP Participants

    2011-12-01

    Our understanding of how carbon is exchanged between terrestrial ecosystems and the atmosphere is gained from direct observations and experiments, as well as through modeling activities. Although models vary in their specific goals and approaches, their central role within carbon cycle research is to provide a better understanding of the mechanisms currently controlling carbon exchange. The multi-scale synthesis and intercomparison project (MsTMIP) has an overall goal of providing feedback to the TBM community to improve the diagnosis and attribution of carbon fluxes at regional and global scales. This project builds upon current and past synthesis activities by developing an integrative framework that all TBMs can use as a tool to continually evaluate overall model performance against a consistent set of observational constraints. The ability of the models to partition changes in estimated carbon flux among drivers such as climate variability, nutrient limitation, land management, and recovery from historical land use and disturbance is fundamental to understanding the terrestrial carbon cycle and improving terrestrial biospheric models. Therefore, in combination with baseline simulations, or a model's best estimate of carbon flux, the MsTMIP activity includes a series of sensitivity simulations that are designed to isolate the impact of specific drivers on model results. Over 18 different TBMs are participating in the study and will be submitting simulation results for the time period 1980 to 2010. A key component of the MsTMIP activity is to evaluate model performance against observations, inversions, and other model estimates through a set of quantitative performance measures and metrics based on inventory and flux tower-based observations. By prescribing standard spin-up procedures, input data sets, and output parameter formats, we quantify and diagnose any biases and uncertainties in TBM estimates of regional and global carbon budgets resulting from differences in model formulation and parameterization. This information will ultimately aid in improving model predictions of land-atmosphere carbon exchange.

  4. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    PubMed

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. PMID:24251443

  5. The Net Exchange Between Terrestrial Ecosystems and the Atmosphere as a Result of Changes in Land Use

    NASA Technical Reports Server (NTRS)

    Houghton, R. A.

    1998-01-01

    The general purpose of this research was to improve and update (to 1990) estimates of the net flux of carbon between the world's terrestrial ecosystems and the atmosphere from changes in land use (e.g., deforestation and reforestation). The estimates are important for understanding the global carbon cycle, and for predicting future concentrations of atmospheric CO2 that will result from emissions. The emphasis of the first year's research was on the northern temperate zone and boreal forests, where the greatest discrepancy exists between estimates of flux. Forest inventories suggest net sinks of 0.6 PgC/yr; inversion analyses based on atmospheric data and models suggest much larger sinks 2-3.6 PgC/yr (e.g., Tans et al. 1990, Ciais et al. 1995). The work carried out with this grant calculated the flux attributable to changes in land use. The estimated flux was somewhat smaller than the flux calculated from inventory data suggesting that environmental changes have led to a small accumulation of carbon in forests that exceeds the accumulation expected from past rates of harvest. Two publications have described these results (Houghton 1996, 1998). The large difference between these estimates and those obtained with atmospheric data and models remains unexplained. The recent estimate of a 1.7 PgC/yr sink in North America, alone (Fan et al. 1998), is particularly difficult to explain. That part of the sink attributable to land-use change, however, is defined as a result of this grant.

  6. Evolving Oxygen Landscape of the Early Atmosphere and Oceans

    NASA Astrophysics Data System (ADS)

    Lyons, T. W.; Reinhard, C. T.; Planavsky, N. J.

    2013-12-01

    The past decade has witnessed remarkable advances in our understanding of oxygen on the early Earth, and a new framework, the topic of this presentation, is now in place to address the controls on spatiotemporal distributions of oxygen and their potential relationships to deep-Earth processes. Recent challenges to the Archean biomarker record have put an added burden on inorganic geochemistry to fingerprint and quantify the early production, accumulation, and variation of biospheric oxygen. Fortunately, a wide variety of techniques now point convincingly to photosynthetic oxygen production and dynamic accumulation well before the canonical Great Oxidation Event (GOE). Recent modeling of sulfur recycling over this interval allows for transient oxygen accumulation in the atmosphere without the disappearance of non-mass-dependent (NMD) sulfur isotope anomalies from the stratigraphic record and further allows for persistent accumulation in the atmosphere well before the permanent disappearance of NMD signals. This recent work suggests that the initial rise of oxygen may have occurred in fits and starts rather than a single step, and that once permanently present in the atmosphere, oxygen likely rose to high levels and then plummeted, in phase with the Paleoproterozoic Lomagundi positive carbon isotope excursion. More than a billion years of oxygen-free conditions in the deep ocean followed and set a challenging course for life, including limited abundances and diversity of eukaryotic organisms. Despite this widespread anoxia, sulfidic (euxinic) conditions were likely limited to productive ocean margins. Nevertheless, euxinia was sufficiently widespread to impact redox-dependent nutrient relationships, particularly the availability of bioessential trace metals critical in the nitrogen cycle, which spawned feedbacks that likely maintained oxygen at very low levels in the ocean and atmosphere and delayed the arrival of animals. Then, in the mid, pre-glacial Neoproterozoic we see evidence for an oxygenation event that significantly predated recent evidence for ocean ventilation in the post-glacial Ediacaran ocean. The trigger that facilitated the transition out of the oxygen-lean ';boring billion' is an area of active study. Additional evidence points to the likelihood of rising and falling oxygen levels through the later Neoproterozoic, which would have had a strong impact on early animal diversification and development of oxygen-demanding ecologies marked by large animals with complex trophic relationships. These observations now provide a context for interpreting the cause-and-effect relationships among the late Proterozoic rise in oxygen, the onset and dynamics of global-scale Neoproterozoic glaciation, metazoan diversification, and large-scale tectonic processes as surface expressions of deep-Earth processes.

  7. Argon isotopic composition of Archaean atmosphere probes early Earth geodynamics.

    PubMed

    Pujol, Magali; Marty, Bernard; Burgess, Ray; Turner, Grenville; Philippot, Pascal

    2013-06-01

    Understanding the growth rate of the continental crust through time is a fundamental issue in Earth sciences. The isotopic signatures of noble gases in the silicate Earth (mantle, crust) and in the atmosphere afford exceptional insight into the evolution through time of these geochemical reservoirs. However, no data for the compositions of these reservoirs exists for the distant past, and temporal exchange rates between Earth's interior and its surface are severely under-constrained owing to a lack of samples preserving the original signature of the atmosphere at the time of their formation. Here, we report the analysis of argon in Archaean (3.5-billion-year-old) hydrothermal quartz. Noble gases are hosted in primary fluid inclusions containing a mixture of Archaean freshwater and hydrothermal fluid. Our analysis reveals Archaean atmospheric argon with a (40)Ar/(36)Ar value of 143 ± 24, lower than the present-day value of 298.6 (for which (40)Ar has been produced by the radioactive decay of the potassium isotope (40)K, with a half-life of 1.25 billion years; (36)Ar is primordial in origin). This ratio is consistent with an early development of the felsic crust, which might have had an important role in climate variability during the first half of Earth's history. PMID:23739427

  8. Early Results from the MODIS Atmosphere Cloud Algorithms

    NASA Technical Reports Server (NTRS)

    Platnick, S.; Ackerman, S. A.; King, M. D.; Menzel, W. P.; Gao, B.-C.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of five instruments aboard the Terra Earth Observing System platform launched in December 1999. With 36 spectral bands from the visible through the infrared, and spatial resolution from 250m to 1km, the instrument provides an unprecedented opportunity for global cloud studies. A comprehensive set of remote sensing algorithms for cloud masking and retrieval of cloud physical and optical properties have been developed by members of the MODIS atmosphere team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud top physical parameters (temperature, pressure, emissivity), cloud phase, cloud optical parameters (optical depth, effective particle radius, water path), visible cirrus reflectance, a contrail flag, and other derived parameters. All products are archived into two categories: pixel-level retrievals at a 1 km or 5 km spatial resolution at nadir (referred to as Level-2 products) and 1 degree global gridded statistics (Level-3 products). An overview of the MODIS atmosphere algorithms and products, their status, validation activities, and early level-2 and -3 results will be presented.

  9. Increasing retention of early career female atmospheric scientists

    NASA Astrophysics Data System (ADS)

    Edwards, L. M.; Hallar, A. G.; Avallone, L. M.; Thiry, H.

    2010-12-01

    Atmospheric Science Collaborations and Enriching NeTworks (ASCENT) is a workshop series designed to bring together early career female scientists in the field of atmospheric science and related disciplines. ASCENT uses a multi-faceted approach to provide junior scientists with tools that will help them meet the challenges in their research and teaching career paths and will promote their retention in the field. During the workshop, senior women scientists discuss their career and life paths. They also lead seminars on tools, resources and methods that can help early career scientists to be successful and prepared to fill vacancies created by the “baby boomer” retirees. Networking is a significant aspect of ASCENT, and many opportunities for both formal and informal interactions among the participants (of both personal and professional nature) are blended in the schedule. The workshops are held in Steamboat Springs, Colorado, home of a high-altitude atmospheric science laboratory, Storm Peak Laboratory, which also allows for nearby casual outings and a pleasant environment for participants. Near the conclusion of each workshop, junior and senior scientists are matched in mentee-mentor ratios of two junior scientists per senior scientist. Post-workshop reunion events are held at national scientific meetings to maintain connectivity among each year’s participants, and for collaborating among participants of all workshops held to date. Evaluations of the two workshop cohorts thus far conclude that the workshops have been successful in achieving the goals of establishing and expanding personal and research-related networks, and that seminars have been useful in creating confidence and sharing resources for such things as preparing promotion and tenure packages, interviewing and negotiating job offers, and writing successful grant proposals.

  10. Fractionation of terrestrial neon by hydrodynamic hydrogen escape from ancient steam atmospheres

    NASA Technical Reports Server (NTRS)

    Zahnle, K.

    1991-01-01

    Atmospheric neon is isotopically heavier than mantle neon. By contrast, nonradiogenic mantle Ar, Kr, and Xe are not known to differ from the atmosphere. These observations are most easily explained by selective neon loss to space; however, neon is much too massive to escape from the modern atmosphere. Steam atmospheres are a likely, if intermittent, feature of the accreting Earth. They occur because, on average, the energy liberated during accretion places Earth above the runaway greenhouse threshold, so that liquid water is not stable at the surface. It is found that steam atmospheres should have lasted some ten to fifty million years. Hydrogen escape would have been vigorous, but abundant heavy constituents would have been retained. There is no lack of plausible candidates; CO2, N2, or CO could all suffice. Neon can escape because it is less massive than any of the likely pollutants. Neon fractionation would have been a natural byproduct. Assuming that the initial Ne-20/Ne-22 ratio was solar, it was found that it would have taken some ten million years to effect the observed neon fractionation in a 30 bar steam atmosphere fouled with 10 bars of CO. Thicker atmospheres would have taken longer; less CO, shorter. This mechanism for fractionating neon has about the right level of efficiency. Because the lighter isotope escapes much more readily, total neon loss is pretty minimal; less than half of the initial neon endowment escapes.

  11. Uncertainty in carbon, climate and nutrient interactions following human disturbance in simulating terrestrial greenhouse-gas exchange with the atmosphere

    NASA Astrophysics Data System (ADS)

    King, A. W.

    2008-12-01

    Human change in vegetation, especially deforestation for agriculture, is second only to the combustion of fossil fuels as an anthropogenic source of CO2 in the Earth's atmosphere. At the same time, the recovery of forests from historical land use, both agriculture and timber harvest, is the single largest contributor to the North American carbon sink, partially mitigating fossil-fuel contributions to increased atmospheric CO2 concentration. These trends are likely to continue in the future, but in a future of changing climate with increasing demand for land to produce food and fuel for growing, more affluent human populations. Understanding, and accurately simulating, terrestrial-ecosystem response to human disturbance and how these disturbed systems respond to management, climate and other environmental change are critical to understanding historical anthropogenic climate forcing and for projecting future trends and uncertainties. These responses remain, however, one of the most uncertain elements of earth system modeling. A great deal is known about individual components: carbon and nutrient cycling, physiological and ecological response to climate and nutrient variability and perturbation; but much less is known about interactions and feedbacks among these components especially in response to disturbance and how they change over time after disturbance, with and without human management. What is known is certainly not well integrated into global earth system models. Here, I use three types of models, a phenomenological model of ecosystem response to land-use change, a mechanistic model of carbon-cycle response to climate and atmospheric CO2, and an individual-based model of forest succession to illustrate how interactions among climate, carbon, nutrients, and human activities are, or are not, represented in terrestrial ecosystem modeling and by extension in global climate models. I also use these models to investigate model sensitivities and their expression as uncertainties in simulation results. I argue that understanding these sensitivities and uncertainties can provide a triage for determining the critical elements of this exceedingly complex system that must be included in integrated terrestrial models for global earth system modeling.

  12. Assessing the impact of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

    NASA Astrophysics Data System (ADS)

    Abbondanza, Claudio; Altamimi, Zuheir; Chin, Toshio; Collilieux, Xavier; Dach, Rolf; Gross, Richard; Heflin, Michael; König, Rolf; Lemoine, Frank; Macmillan, Dan; Parker, Jay; van Dam, Tonie; Wu, Xiaoping

    2014-05-01

    The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, we assess the impact of non-tidal atmospheric loading (NTAL) corrections on the TRF computation. Focusing on the a-posteriori approach, (i) the NTAL model derived from the National Centre for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations; (ii) adopting a Kalman-filter based approach, two distinct linear TRFs are estimated combining the 4 SG solutions with (corrected TRF solution) and without the NTAL displacements (standard TRF solution). Linear fits (offset and atmospheric velocity) of the NTAL displacements removed during step (i) are estimated accounting for the station position discontinuities introduced in the SG solutions and adopting different weighting strategies. The NTAL-derived (atmospheric) velocity fields are compared to those obtained from the TRF reductions during step (ii). The consistency between the atmospheric and the TRF-derived velocity fields is examined. We show how the presence of station position discontinuities in SG solutions degrades the agreement between the velocity fields and compare the effect of different weighting structure adopted while estimating the linear fits to the NTAL displacements. Finally, we evaluate the effect of restoring the atmospheric velocities determined through the linear fits of the NTAL displacements to the single-technique linear reference frames obtained by stacking the standard SG SINEX files. Differences between the velocity fields obtained restoring the NTAL displacements and the standard stacked linear reference frames are discussed.

  13. Using atmospheric observations to evaluate the spatiotemporal variability of CO2 fluxes simulated by terrestrial biospheric models

    NASA Astrophysics Data System (ADS)

    Fang, Y.; Michalak, A. M.; Shiga, Y. P.; Yadav, V.

    2014-06-01

    Terrestrial biospheric models (TBMs) are used to extrapolate local observations and process-level understanding of land-atmosphere carbon exchange to larger regions, and serve as a predictive tool for examining carbon-climate interactions. Understanding the performance of TBMs is thus crucial to the carbon cycle and climate science. In this study, we propose a statistical model selection approach for evaluating the spatiotemporal patterns of net ecosystem exchange (NEE) simulated by TBMs using atmospheric CO2 measurements. We find that current atmospheric observations are sensitive to the underlying spatiotemporal flux variability at sub-biome scales for a large portion of the North American continent, and that atmospheric observations can therefore be used to evaluate simulated spatiotemporal flux patterns, rather than focusing solely on flux magnitudes at aggregated scales. Results show that the proposed approach can be used to assess whether a TBM represents a substantial portion of the underlying flux variability as well as to differentiate among multiple competing TBMs. When applying the proposed approach to four prototypical TBMs, we find that the performance of TBMs varies substantially across seasons, with best performance during the growing season and limited skill during transition seasons. This seasonal difference in the ability of TBMs to represent the spatiotemporal flux variability may reflect the models' capability to represent the seasonally-varying influence of environmental drivers on fluxes. While none of the TBMs consistently outperforms the others, differences among the examined models are at least partially attributable to their internal structures. Overall, the proposed approach provides a new avenue for evaluating TBM performance based on sub-biome scale flux patterns, presenting an opportunity for assessing and informing model development using atmospheric observations.

  14. Three-Dimensional Tracer Model Study of Atmospheric CO2 - Response to Seasonal Exchanges with the Terrestrial Biosphere

    NASA Technical Reports Server (NTRS)

    Fung, I.; Prentice, K.; Matthews, E.; Lerner, J.; Russell, G.

    1983-01-01

    A three-dimensional tracer transport model is used to investigate the annual cycle of atmospheric CO2 concentration produced by seasonal exchanges with the terrestrial biosphere. The tracer model uses winds generated by a global general circulation model to advect and convect CO2; no explicit diffusion coefficients are employed. A biospheric exchange function constructed from a map of net primary productivity, and Azevedo's (1982) seasonality of CO2 uptake and release closely simulates the annual cycles at coastal stations. The results show that zonal homogeneity in surface CO2 concentrations can never be achieved at mid-latitudes where the time scale for zonal mixing is longer than the time scale for biospheric exchange. Analysis of the zonal mean balance in the lower troposphere reveals that atmospheric transport processes may alter the CO2 response to local biospheric exchanges by 50% or more. Hence year-to-year variation of the annual CO2 cycle may result from the natural variability of the atmospheric circulation as well as from changes in the sources and sinks.

  15. Early warning of atmospheric regime transitions using transfer operators

    NASA Astrophysics Data System (ADS)

    Tantet, Alexis; Dijkstra, Henk

    2015-04-01

    The existence of persistent midlatitude atmospheric regimes, such as blocking events, with time scales larger than 5-10 days and indications of preferred transition paths between them motivates the development of early-warning indicators of regime transitions. Here, we use a barotropic model of the northern midlatitudes winter flow to study such meta-stable regimes. We look at estimates of transfer operators acting on densities evolving on a reduced phase space spanned by the first Empirical Orthogonal Functions of the streamfunction and develop an early-warning indicator of zonal to blocked flow transition. The study of the spectra of transfer operators estimated for different lags reveals a multi-level structure in the flow as well as the effect of memory on the reduced dynamics due to past interactions between the resolved and unresolved variables. The slowest motions in the reduced phase space are thereby found to have time scales larger than 8 days and to behave as Markovian for larger lags. These motions are associated with meta-stable regimes and their transitions and can be detected as almost-invariant sets of the transfer operator. The early-warning indicator is based on the action on an initial density of products of the transfer operators estimated for sufficiently long lags, making use of the semi-group property of these operators and shows relatively good Peirce skill score. From the energy budget of the model, we are able to explain the meta-stability of the regimes and the existence of preferred transition paths as the manifestation of barotropic instability. Finally, even though the model is highly simplified, the skill of the early warning indicator is promising, suggesting that the transfer operator approach can be used in parallel to an operational deterministic model for stochastic prediction or to assess forecast uncertainty.

  16. Early MAVEN Results on the Mars Upper Atmosphere and Atmospheric Loss to Space

    NASA Astrophysics Data System (ADS)

    Jakosky, Bruce; Grebowsky, Joseph; Luhmann, Janet

    2015-04-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft went into orbit around Mars on 21 September 2014. After a commissioning phase that included science observations of Mars and of Comet Siding Spring during its close approach, its primary science phase began on 16 November 2014 and will run for a full Earth year, until November 2015. The science objectives of the MAVEN mission are to characterize the upper atmosphere and ionospheric structure and composition, the interactions of the sun and the solar wind with the planet, and the processes driving loss of gas from the atmosphere to space. Our goal is to understand the chain of processes leading to escape today, learn how to extrapolate back in time, and determine the integrated escape of atmosphere over Martian history. MAVEN has nine instrument sensors collected into eight separate instruments. The sensors can be thought of as being grouped into instruments measuring different aspects pertaining to the goals of MAVEN. The first group of instruments measures the properties of the solar wind and of the sun that drive the processes in the upper atmosphere. The second group measures the structure and composition of the upper atmosphere and of the ions in the ionosphere, and also measures isotope ratios that can tell us about the integrated escape to space. In this group, NGIMS measures properties in situ at the location of the spacecraft, and IUVS measures them remotely, providing a powerful combination of local and global measurements. The third group measures the properties of the ionosphere that both drive escape and determine the composition and properties of the escaping ions. The spacecraft and all science instruments are functioning nominally, and science data is being collected utilizing our planned observing scenarios. The first deep-dip campaign is scheduled for the second week of February 2015. By the time of the EGU meeting, we expect to have a preliminary understanding of the instrument behavior, operations, and calibrations. We also expect to have sufficient data collected to allow us to reach preliminary conclusions about the state of the upper atmosphere, interactions with the solar wind, escape of atmospheric gas to space at the present epoch, and integrated escape to space over time. These early results will be presented.

  17. Dynamic oxygenation of the early atmosphere and oceans

    NASA Astrophysics Data System (ADS)

    Lyons, Timothy W.; Planavsky, Noah J.; Reinhard, Christopher T.

    2014-05-01

    The traditional view of the oxygenation of the early atmosphere and oceans depicts irreversibly rising abundances in two large steps: one at the Great Oxidation Event (GOE) ca. 2.3-2.4 billion years ago (Ga) and another near the end of the Neoproterozoic. This talk will explore how the latest data challenge this paradigm. Recent results reveal a far more dynamic history of early oxygenation, one with both rising and falling levels, long periods of sustained low concentrations even after the GOE, complex feedback relationships that likely coupled nutrients and ocean redox, and dramatic changes tied through still-emerging cause-and-effect relationships to first-order tectonic, climatic, and evolutionary events. In the face of increasing doubt about the robustness of organic biomarker records from the Archean, researchers are increasingly reliant on inorganic geochemical proxies for the earliest records of oxygenic photosynthesis. Proxy data now suggest oxygenesis at ca. 3.0 Ga with a likelihood of local oxygen build up in the surface ocean long before the GOE, as well as low (and perhaps transient) accumulation in the atmosphere against a backdrop of mostly less than ca. 0.001% of the present atmospheric concentration. By the GOE, the balance between oxygen sources and sinks shifted in favor of persistent accumulation, although sedimentary recycling of non-mass-dependent sulfur isotope signatures allows for the possibility of rising and falling atmospheric oxygen before the GOE as traditionally defined by the sulfur isotope record. Recycling may also hinder our ability to precisely date the transition to permanent oxygen accumulation beyond trace levels. Diverse data point to a dramatic increase in biospheric oxygen following the GOE, coincident with the largest positive carbon isotope excursion in Earth history, followed by an equally dramatic drop. This decline in Earth surface redox potential ushered in more than a billion years of dominantly low oxygen levels in the atmosphere—at perhaps much less than 1% of modern levels, as suggested by new chromium isotope data—and persistent anoxia in the deep ocean with euxinia limited to productive ocean margins. Under conditions of ca. 1-10% euxinic seafloor, bioessential trace metals would have been drawn down to levels that may have deleteriously impacted the availability of fixed nitrogen in the oceans and, through associated redox-dependent feedbacks, sustained comparatively low global levels of primary production and corresponding deficiencies in biospheric oxygen. This episode of intermediate redox gave way to increases in ocean-atmosphere oxygen that appear to predate the Sturtian glaciation. Although the causes behind this transition are not well understood, they are certain to reflect relationships among large-scale tectonic, climatic, and biotic drivers of nutrient availability and organic carbon production and burial. Oxygen during the Ediacaran, following the Marinoan glaciation, likely rose and fell episodically in ways that must have impacted the diversity and ecological relationships among early animals. Also, the low oxygen concentrations purported for the mid-Proterozoic are consistent with the long-held, but recently challenged, suggestion that the rise of animals was ultimately coincident with, and likely causally related to, a Neoproterozoic rise in oxygen.

  18. A Carbon Flux Super Site. New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling

    SciTech Connect

    Leclerc, Monique Y.

    2014-11-17

    This final report presents the main activities and results of the project “A Carbon Flux Super Site: New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling” from 10/1/2006 to 9/30/2014. It describes the new AmeriFlux tower site (Aiken) at Savanna River Site (SC) and instrumentation, long term eddy-covariance, sodar, microbarograph, soil and other measurements at the site, and intensive field campaigns of tracer experiment at the Carbon Flux Super Site, SC, in 2009 and at ARM-CF site, Lamont, OK, and experiments in Plains, GA. The main results on tracer experiment and modeling, on low-level jet characteristics and their impact on fluxes, on gravity waves and their influence on eddy fluxes, and other results are briefly described in the report.

  19. Development of a model of atmospheric oxygen variations to estimate terrestrial carbon storage and release

    NASA Technical Reports Server (NTRS)

    Najjar, Raymond G.; Keeling, Ralph F.; Erickson, David J., III

    1995-01-01

    Two years of work has been completed towards the development of a model of atmospheric oxygen variations on seasonal to decadal timescales. During the first year we (1) constructed a preliminary monthly-mean climatology of surface ocean oxygen anomalies, (2) began modeling studies to assess the importance of short term variability on the monthly-mean oxygen flux, and (3) conducted preliminary simulations of the annual mean cycle of oxygen in the atmosphere. Most of the second year was devoted to improving the monthly mean climatology of oxygen in the surface ocean.

  20. A sensitivity study of the obliquity of the early Earth with the ECHAM/MESSy Atmospheric Chemistry model

    NASA Astrophysics Data System (ADS)

    Hamann-Reinus, Anke; Kunze, Markus; Langematz, Ulrike; Godolt, Mareike; Jöckel, Patrick; Rauer, Heike

    Studying the evolution of early Earth's atmosphere is of crucial importance for the understand-ing of the habitability of the terrestrial planets and, in the end, the development of life. In this contribution we investigate the influence of the Earth's obliquity on atmospheric dynam-ics. For this parameter study of obliquity we use here the Chemistry Climate model EMAC (ECHAM/MESSy Atmospheric Chemistry model). According to Ito and Hamano (1995), the obliquity of the Earth's axis was only 19.5 at the age of 2.5 Gyr. To analyse in particular the sen-sitivity of the model dynamics we selected therefore three representative obliquity values: 23.5 (control run), 19.5 (lowered obliquity, see Ito and Hamano (1995)), 27.5 (increased obliquity-comparative study). For our numerical experiments we use the present day atmospheric compo-sition, land-mask, and solar luminosity. We present results regarding the atmospheric dynamics and circulation focussing thereby on the middle atmosphere.

  1. Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 due to uncertainty in biological nitrogen fixation

    NASA Astrophysics Data System (ADS)

    Meyerholt, J.; Zaehle, S.; Smith, M. J.

    2015-12-01

    Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere-climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important, but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty, and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity (NPP) and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 95 to 134 Tg N yr-1 (median 119 Tg N yr-1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between -4 Tg N yr-1 (-3 %) and 56 Tg N yr-1 (+42 %) (median 7 Tg N yr-1 (+8 %)). As a consequence, future projections of global ecosystem carbon storage (+281 to +353 Pg C, or +13 to +16 %), as well as N2O emission (-1.6 to +0.5 Tg N yr-1, or -19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

  2. Variability of projected terrestrial biosphere responses to elevated levels of atmospheric CO2 due to uncertainty in biological nitrogen fixation

    NASA Astrophysics Data System (ADS)

    Meyerholt, Johannes; Zaehle, Sönke; Smith, Matthew J.

    2016-03-01

    Including a terrestrial nitrogen (N) cycle in Earth system models has led to substantial attenuation of predicted biosphere-climate feedbacks. However, the magnitude of this attenuation remains uncertain. A particularly important but highly uncertain process is biological nitrogen fixation (BNF), which is the largest natural input of N to land ecosystems globally. In order to quantify this uncertainty and estimate likely effects on terrestrial biosphere dynamics, we applied six alternative formulations of BNF spanning the range of process formulations in current state-of-the-art biosphere models within a common framework, the O-CN model: a global map of static BNF rates, two empirical relationships between BNF and other ecosystem variables (net primary productivity and evapotranspiration), two process-oriented formulations based on plant N status, and an optimality-based approach. We examined the resulting differences in model predictions under ambient and elevated atmospheric [CO2] and found that the predicted global BNF rates and their spatial distribution for contemporary conditions were broadly comparable, ranging from 108 to 148 Tg N yr-1 (median: 128 Tg N yr-1), despite distinct regional patterns associated with the assumptions of each approach. Notwithstanding, model responses in BNF rates to elevated levels of atmospheric [CO2] (+200 ppm) ranged between -4 Tg N yr-1 (-3 %) and 56 Tg N yr-1 (+42 %) (median: 7 Tg N yr-1 (+8 %)). As a consequence, future projections of global ecosystem carbon (C) storage (+281 to +353 Pg C, or +13 to +16 %) as well as N2O emission (-1.6 to +0.5 Tg N yr-1, or -19 to +7 %) differed significantly across the different model formulations. Our results emphasize the importance of better understanding the nature and magnitude of BNF responses to change-induced perturbations, particularly through new empirical perturbation experiments and improved model representation.

  3. Introduction to the study of cosmic rays and their interaction with the terrestrial atmosphere

    NASA Astrophysics Data System (ADS)

    Schuch, Luiz Alexandre

    A broad survey is presented on the origin and composition of cosmic rays, its modulation associated with solar activity, its interaction with the Earth's magnetic field and atmosphere and its energy spectrum at sea level. Special attention is given to detection systems and to the effects of cosmic rays on material and live beings, especially man.

  4. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid.

    PubMed

    Donaldson, Melissa A; Bish, David L; Raff, Jonathan D

    2014-12-30

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼ 3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  5. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid

    PubMed Central

    Donaldson, Melissa A.; Bish, David L.; Raff, Jonathan D.

    2014-01-01

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  6. Continental scale atmospheric and terrestrial water budget modeling and comparison to GRACE

    NASA Astrophysics Data System (ADS)

    Fersch, B.; Kunstmann, H.; Sneeuw, N.; Devaraju, B.

    2009-04-01

    Estimation of large scale water balances is still an unsolved challenge in hydrological sciences, particularly for data spare regions. The GRACE satellite mission (launched in 2002) provides a completely new opportunity to investigate seasonal large scale water mass changes based on measurements of gravitational acceleration differences. Our study aims at determining the potential of GRACE data for hydrological applications. Our approach assumes that vertically integrated atmospheric moisture convergence equals 1) precipitated minus evapotranspired water masses and therefore equals 2) aggregated surface runoff minus water storage changes. Using observed basin runoff, this interrelation allows us to compare GRACE derived water storage changes with modeled atmospheric moisture convergences. As regional atmospheric modeling is expected to yield more accurate meteorological fields than global model results, we use the WRF model for a dynamic downscaling of global atmospheric fields and hence derive high resolution fields of air pressure, horizontal moisture flux divergence, precipitation minus evapotranspiration, soil water storage, etc. Our study focuses on sensitivities and uncertainties of regionally modeled atmospheric mass and moisture fluxes due to specific model setup, origin of global driving data (NCEP vs. ECMWF) and spatial resolution. This is performed for four regions: Australia, Sahara, Siberia and the Amazon. The first three regions are characterized by a simplified hydrological mass balance, i.e. either evaporation or precipitation is close to zero. Central Australia represents a region with no outlet, meaning runoff is negligible. The Sahara also has zero runoff and for the dry periods evapotranspiration is close to zero. Siberia, comprising the catchments of Lena and Yenisei has negligible evapotranspiration for the winter months. The basin of the Amazon is representative for regions with high precipitation and evaporation terms. For the years 2003 to 2008, correlations between monthly GRACE derived and regionally modeled water storage changes are shown for the mentioned areas. Also, the uncertainty bounds of the atmospheric moisture flux computations that arise from different atmospheric driving data (NCEP Reanalysis, ECMWF Operational Analysis, ECMWF ERA-INTERIM) are estimated. Also, the effects of different sea surface temperature data and nudging towards global datasets will be depicted. Furthermore, the estimated water budgets are compared to weekly GRACE solutions that have become available in late 2008 by GFZ Potsdam.

  7. Verification of Atmospheric Signals Associated with Major Seismicity by Space and Terrestrial Observations

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick

    2008-01-01

    Observations from the last twenty years suggest the existence of electromagnetic (EM) phenomena during or preceding some earthquakes [Haykawa et a!, 2004; Pulinets at al, 1999,2004, 2006, Ouzounov et all 2007 and Liu et all 20041. Both our previous studies [Pulinets at al, 2005, 2006, Ouzounov et al, 2006, 20071 and the latest review by the Earthquake Remote Precursor Sensing panel [ERPS; 2003- 20051; have shown that there were precursory atmospheric TIR signals observed on the ground and in space associated with several recent earthquakes. [Tramutoli at al, 2005, 2006, Cervone et al, 2006, Ouzounov et all 2004,2006JT.o study these signals, we applied both multi parameter statistical analysis and data mining methods that require systematic measurements from an Integrated Sensor Web of observations of several physical and environmental parameters. These include long wave earth infra-red radiation, ionospheric electrical and magnetic parameters, temperature and humidity of the boundary layer, seismicity and may be associated with major earthquakes. Our goal is to verify the earthquake atmospheric correlation in two cases: (i) backward analysis - 2000-2008 hindcast monitoring of multi atmospheric parameters over the Kamchatka region, Russia ; and (ii) forward real-time alert analysis over different seismo-tectonic regions for California, Turkey, Taiwan and Japan. Our latest results, from several post-earthquake independent analyses of more then 100 major earthquakes, show that joint satellite and some ground measurements, using an integrated web, could provide a capability for observing pre-earthquake atmospheric signals by combining the information from multiple sensors into a common framework. Using our methodology, we evaluated and compared the observed signals preceding the latest M7.9 Sichuan earthquake (0511212008), M8.0 earthquake in Peru (0811512007), M7.6 Kashmir earthquake (1010812005) and M9.0 Sumatra earthquake (1212812004). We found evidence of the systematic appearance of both atmospheric and ionospheric anomalies preceding most of the major events during the period of our analysis 2001 -2008.

  8. Teaching about the Early Earth: Evolution of Tectonics, Life, and the Early Atmosphere

    NASA Astrophysics Data System (ADS)

    Mogk, D. W.; Manduca, C. A.; Kirk, K.; Williams, M. L.

    2007-12-01

    The early history of the Earth is the subject of some of the most exciting and innovative research in the geosciences, drawing evidence from virtually all fields of geoscience and using a variety of approaches that include field, analytical, experimental, and modeling studies. At the same time, the early Earth presents unique opportunities and challenges in geoscience education: how can we best teach "uncertain science" where the evidence is either incomplete or ambiguous? Teaching about early Earth provides a great opportunity to help students understand the nature of scientific evidence, testing, and understanding. To explore the intersection of research and teaching about this enigmatic period of Earth history, a national workshop was convened for experts in early Earth research and undergraduate geoscience education. The workshop was held in April, 2007 at the University of Massachusetts at Amherst as part of the On the Cutting Edge faculty professional development program. The workshop was organized around three scientific themes: evolution of global tectonics, life, and the early atmosphere. The "big scientific questions" at the forefront of current research about the early Earth were explored by keynote speakers and follow-up discussion groups: How did plate tectonics as we know it today evolve? Were there plates in the Hadean Eon? Was the early Earth molten? How rapidly did it cool? When and how did the atmosphere and hydrosphere evolve? How did life originate and evolve? How did all these components interact at the beginning of Earth's history and evolve toward the Earth system we know today? Similar "big questions" in geoscience education were addressed: how to best teach about "deep time;" how to help students make appropriate inferences when geologic evidence is incomplete; how to engage systems thinking and integrate multiple lines of evidence, across many scales of observation (temporal and spatial), and among many disciplines. Workshop participants developed a collection of teaching strategies to begin to address the challenge of integrating new scientific advances with effective instructional practices with an emphasis on data analysis and critical review of evidence. The workshop webpage includes the workshop program with links to all presentations and discussion summaries, a collection of recommended readings about early Earth research, ideas for teaching about Early Earth, suggestions on how to teach uncertain science, and classroom activities.

  9. Impact of Aquatic and Terrestrial Emissions on Atmospheric N2O Variability

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.; Riddick, S. N.; Saikawa, E.; Hess, P. G.

    2013-12-01

    Atmospheric concentrations of the greenhouse gas nitrous oxide (N2O) have increased by about 20% since the preindustrial era, an increase that has been driven largely by use of anthropogenic nitrogen fertilizers. The N2O source associated with agriculture was historically underestimated by assessments that considered only direct emissions from fertilized fields, but more recently it has been recognized that 'indirect' emissions associated with N leaching and runoff to rivers and may account for as much as half of total agricultural N2O emissions. Meanwhile, recent regional atmospheric N2O inversions have inferred large North American agricultural N2O sources that are difficult to reconcile with global budget constraints. At the same time, it is not clear whether the inversions can detect indirect N2O emissions associated with nitrogen leaching and runoff. Here, we will present forward model simulations aimed at quantifying the relative magnitude, spatial distribution and timing of direct and indirect agricultural N2O emissions. The model simulations will be based on the Community Land Model (CLM), with new agricultural and trace N gas parameterizations, coupled to the River Transport Model (RTM), with a module for estimating river N transport and N2O production associated with in-stream sediment denitrification. The coupled CLM-RTM N2O fluxes will be used to force atmospheric chemistry tracer transport model (ACTM) simulations, with direct and indirect emissions carried as separate tracers. The ACTM results will be used to evaluate the impact of both types of emissions on site-specific variability in atmospheric N2O at United States monitoring sites and to assess the likelihood that current atmospheric monitoring networks can detect these signals. Locations of selected NOAA monitoring sites for atmospheric N2O over the continental United States, showing both aircraft (triangles) and surface flask or tower sites (filled circles). Site locations are superimposed on a map of present-day N fertilizer use, one of the primary drivers of N2O fluxes in our CLM-RTM simulations.

  10. Effects of long-period solar activity fluctuation on temperature and pressure of the terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Rubashev, B. M.

    1978-01-01

    The present state of research on the influence of solar sunspot activity on tropospheric temperature and pressure is reviewed. The existence of an 11-year temperature cycle of 5 different types is affirmed. A cyclic change in atmospheric pressure, deducing characteristic changes between 11-year cycles is discussed. The existence of 80-year and 5-to-6-year cycles of temperature is established, and physical causes for birth are suggested.

  11. Observed and Modeled Tritium Concentrations in the Terrestrial Food Chain near a Continuous Atmospheric Source

    SciTech Connect

    Davis, P.A.; Kim, S.B.; Chouhan, S.L.; Workman, W.J.G.

    2005-07-15

    Tritium concentrations were measured in a large number of environmental and biological samples collected during 2002 at two dairy farms and a hobby farm near Pickering Nuclear Generating Station in Ontario, Canada. The data cover most compartments of the terrestrial food chain in an agricultural setting and include detailed information on the diets of the local farm animals. Ratios of plant OBT concentration to air moisture HTO varied between 0.12 and 0.56, and were generally higher for the forage crops collected at the dairy farms than for the garden vegetables sampled at the hobby farm. Animal OBT to air HTO ratios were more uniform, ranging from 0.18 to 0.45, and were generally higher for the milk and beef samples from the dairy farms than for the chicken products from the hobby farm. The observed OBT concentrations in plants and animals were compared with predictions of IMPACT, the model used by the Canadian nuclear industry to calculate annual average doses due to routine releases. The model performed well on average for the animal endpoints but overestimated concentrations in plants by a factor of 2.

  12. Verification of Atmospheric Signals Associated with Major Seismicity by Space and Terrestrial Observations

    NASA Astrophysics Data System (ADS)

    Ouzounov, D.; Pulinets, S.; Taylor, P.; Bryant, N.; Cervone, G.; Kafatos, M.; Habib, S.

    2008-12-01

    Observations from the last twenty years suggest the existence of electromagnetic (EM) phenomena during or preceding some earthquakes [Hayakawa et al, 2004; Pulinets at al, 1999,2004, 2006, Ouzounov et al, 2007 and Liu et al, 2004]. Both our previous studies [Pulinets at al, 2005, 2006, Ouzounov et al, 2006, 2007] and the latest review by the Earthquake Remote Precursor Sensing panel [ERPS; 2003-2005]; have shown that there were precursory atmospheric TIR signals observed on the ground and in space associated with several recent earthquakes. [Tramutoli et al, 2005, 2006, Cervone et al, 2006, Ouzounov et al, 2004,2006]. To study these signals, we applied both multi parameter statistical analysis and data mining methods that require systematic measurements from an Integrated Sensor Web of observations of several physical and environmental parameters. These include long wave earth infra-red radiation, ionospheric electrical and magnetic parameters, temperature and humidity of the boundary layer, seismicity and may be associated with major earthquakes. Our goal is to verify the earthquake atmospheric correlation in two cases: (i) backward analysis - 2000-2008 hindcast monitoring of multi atmospheric parameters over the Kamchatka region, Russia ; and (ii) forward real-time alert analysis over different seismo-tectonic regions for California, Turkey, Taiwan and Japan. Our latest results, from several post-earthquake independent analyses of more then 100 major earthquakes, show that joint satellite and some ground measurements, using an integrated web, could provide a capability for observing pre-earthquake atmospheric signals by combining the information from multiple sensors into a common framework. Using our methodology, we evaluated and compared the observed signals preceding the latest M7.9 Sichuan earthquake (05/12/2008), M8.0 earthquake in Peru (08/15/2007), M7.6 Kashmir earthquake (10/08/2005) and M9.0 Sumatra earthquake (12/26/2004). We found evidence of the systematic appearance of both atmospheric and ionospheric anomalies preceding most of the major events during the period of our analysis 2001-2008.

  13. Using dimers to measure biosignatures and atmospheric pressure for terrestrial exoplanets.

    PubMed

    Misra, Amit; Meadows, Victoria; Claire, Mark; Crisp, Dave

    2014-02-01

    We present a new method to probe atmospheric pressure on Earth-like planets using (O2-O2) dimers in the near-infrared. We also show that dimer features could be the most readily detectable biosignatures for Earth-like atmospheres and may even be detectable in transit transmission with the James Webb Space Telescope (JWST). The absorption by dimers changes more rapidly with pressure and density than that of monomers and can therefore provide additional information about atmospheric pressures. By comparing the absorption strengths of rotational and vibrational features to the absorption strengths of dimer features, we show that in some cases it may be possible to estimate the pressure at the reflecting surface of a planet. This method is demonstrated by using the O2 A band and the 1.06 μm dimer feature, either in transmission or reflected spectra. It works best for planets around M dwarfs with atmospheric pressures between 0.1 and 10 bar and for O2 volume mixing ratios above 50% of Earth's present-day level. Furthermore, unlike observations of Rayleigh scattering, this method can be used at wavelengths longer than 0.6 μm and is therefore potentially applicable, although challenging, to near-term planet characterization missions such as JWST. We also performed detectability studies for JWST transit transmission spectroscopy and found that the 1.06 and 1.27 μm dimer features could be detectable (SNR>3) for an Earth analogue orbiting an M5V star at a distance of 5 pc. The detection of these features could provide a constraint on the atmospheric pressure of an exoplanet and serve as biosignatures for oxygenic photosynthesis. We calculated the required signal-to-noise ratios to detect and characterize O2 monomer and dimer features in direct imaging-reflected spectra and found that signal-to-noise ratios greater than 10 at a spectral resolving power of R=100 would be required. PMID:24432758

  14. Climate and year-to-year variability of atmospheric and terrestrial water cycles in the three great Siberian rivers

    NASA Astrophysics Data System (ADS)

    Oshima, Kazuhiro; Tachibana, Yoshihiro; Hiyama, Tetsuya

    2015-04-01

    Among all the rivers that flow into the Arctic Ocean, the Lena, Yenisei, and Ob are the three largest in terms of water discharge (R), and they are a large source of freshwater. We analyzed the R observed at the river mouths and precipitation minus evapotranspiration (P - E) estimated from atmospheric reanalyses. P is a key player in the water cycles of the Siberian rivers, but regional differences of E also affect the long-term means of R and P - E. Climate fields and terrestrial conditions play some roles for the regional differences of P and E. A decomposition analysis of the moisture flux revealed that moisture transport associated with cyclone activity dominates the climatological features of P - E over the Lena, whereas moisture transport associated with seasonal mean winds dominates the features of P - E over the Ob. Both transport processes affect over the Yenisei. Whereas the moisture transports related to the climatological P - E differs among the rivers, P - E variations are mainly affected by the stationary component of moisture transport for all three Siberian rivers. Although previous studies have shown considerable deviations between P - E and R variations, the year to year variations agree very well with each other when appropriate seasonal time lags are taken into account. Comparison with the results of six atmospheric reanalyses indicated that estimations of P - E with the reanalyses produce values comparable to observed Rs and are therefore an effective way to examine the water cycles of the Siberian rivers.

  15. The National Ecological Observatory Network's Atmospheric and Terrestrial Instrumentation: Quality Control Approaches

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.; Luo, H.; Ayres, E.; Metzger, S. R.; Loescher, H. W.

    2012-12-01

    The National Ecological Observatory Network's Fundamental Instrument Unit (NEON-FIU) is responsible for making automated terrestrial observations at 60 different sites across the continent. FIU will provide data on key local physical, chemical, and climate forcing, as well as associated biotic responses (CO2, H2O, and energy exchanges). The sheer volume of data that will be generated far exceeds that of any other observatory network or agency, (i.e., > 45 Tb/year from 10's of thousands of remotely deployed sensors). We address the question of how to develop and implement a large ecological observatory that can accommodate such a large volume of data while maintaining high quality. Here, we describe our quality assurance and quality control (QA/QC) program to produce quality data while leveraging cyber infrastructure tools and optimizing technician time. Results focus on novel approaches that advance the quality control techniques that have been historically employed in other networks (DOE-ARM, AmeriFlux, USDA ARS, OK Mesonet) to new state-of-the-art functionality. These automated and semi-automated approaches are also used to inform automated problem tracking to efficiently deploy field staff. Ultimately, NEON will define its own standards for QA/QC and maintenance by building upon these existing frameworks. The overarching philosophy relies on attaining the highest levels of accuracy, precision, and operational time, while efficiently optimizing the effort needed to produce quality data products. Our preliminary results address the challenges associated with automated implementation of sensor command/control, plausibility testing, despiking, and data verification of FIU observations.

  16. Time evolution of ionization effect due to cosmic rays in terrestrial atmosphere during GLE 70

    NASA Astrophysics Data System (ADS)

    Mishev, A. L.; Velinov, P. I. Y.

    2015-07-01

    In the last years the possible effect of solar variability on atmospheric physics and chemistry is highly debated. In most of the proposed models the role of ion production in the atmosphere due to cosmic rays is significant. At present, effects on minor constituents and aerosols are observed over polar regions during major solar events. According to recent findings for such a study it is necessary an essential increase of ion production, specifically during the winter season. Therefore, the ground level enhancement on 13th of December 2006 is appropriate for such a study. Here, we compute the ion production on 13th of December 2006 on the basis of a full target model based on Monte Carlo simulations. The ion production is computed on a step ranging from 10 to 30 min throughout the event. The spectral and angular characteristics of the solar protons are explicitly considered as well as their time evolution. The ionization effect is computed at several altitudes above the sea level, namely 25 km, 18 km, 15 km, 12 km and 8 km in a sub-polar a and polar region, where the effect is maximal. Several applications of the obtained results are discussed.

  17. On the emission of amines from terrestrial vegetation in the context of atmospheric new particle formation

    NASA Astrophysics Data System (ADS)

    Neftel, Albrecht; Sintermann, Jörg

    2015-04-01

    Airborne amines, specifically methylamines (MAs), play a key role in atmospheric new particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NFP events observed in remote regions. High MA contents as well as emissions by plants have already been described in the 19th century. Strong MA emissions predominantly occur during flowering as part of a pollination strategy. The behaviour is species specific, but examples of such species are common and widespread. In addition, vegetative plant tissue exhibiting high amounts of MAs might potentially lead to significant emissions, and the decomposition of organic material could constitute another source for airborne MAs. These mechanisms would provide sources, which could be crucial for the amine's role in NPF, especially in remote regions. Knowledge about vegetation-related amine emissions is, however, very limited and thus it is also an open question how Global Change and the intensified cycling of reactive nitrogen over the last 200 years have altered amine emissions from vegetation with a corresponding effect on NPF.

  18. Effects of the upper atmosphere on terrestrial and earth-space communications: final results of the eu cost271 action

    NASA Astrophysics Data System (ADS)

    Zolesi, B.; Cander, Lj.

    Project ``Effects of the Upper Atmosphere on Terrestrial and Earth-Space Communications (EACOS)'' was inaugurated as a four-year 271 Action in the Telecommunications and Information Science and Technology domain of the EU COST (Co-operation in the Field of Scientific and Technical Research) in October 2000. It follows two previous successful Actions COST 238 on PRIME (Prediction and Retrospective Ionospheric Modelling over Europe) and COST 251 on IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation). The COST 271 Action (EACOS) has been oriented towards: (i) collection of new ionospheric and plasmaspheric data for now-casting and forecasting purposes, (ii) development methods and algorithms to predict and to minimise the effects of plasmaspheric-ionospheric perturbations and variations on communications; (iii) perform studies that influence the technical development and the implementation of new communication services, particularly for the GNSS and other advanced Earth-space and satellite to satellite applications; and (iv) dissemination and correlation of results, ideas and information which will provide a valuable support to European research centres and industry. This paper reviews the main results achieved in the COST 271 Action concerning in particular a range of the ionospheric space weather issues as: nowcasting, forecasting and warning tools, methods and supporting databases for ionospheric propagation prediction; total electron content variations and their use in the reconstruction of plasmaspheric-ionospheric structures as a key parameter for navigation error in GNSS applications and effects of planetary and gravity waves and gradients of the electron density on terrestrial and satellite communications.

  19. Effects of the upper atmosphere on terrestrial and Earth space communications: Final results of the EU COST 271 Action

    NASA Astrophysics Data System (ADS)

    Zolesi, B.; Cander, Lj. R.

    Project “Effects of the Upper Atmosphere on Terrestrial and Earth Space Communications (EACOSs)” was inaugurated as a four-year 271 Action in the Telecommunications and Information Science and Technology domain of the EU COST (Co-operation in the Field of Scientific and Technical Research) in October 2000. It followed two previous successful Actions COST 238 on PRIME (Prediction and Retrospective Ionospheric Modelling over Europe) and COST 251 on IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation). The COST 271 Action (EACOS) has been oriented towards: (i) collection of new ionospheric and plasmaspheric data for now-casting and forecasting purposes, (ii) development of methods and algorithms to predict and to minimise the effects of plasmaspheric ionospheric perturbations and variations on communications; (iii) perform studies that influence the technical development and the implementation of new communication services, particularly for the GNSS and other advanced Earth space and satellite-to-satellite applications; and (iv) dissemination and correlation of results, ideas and information which will provide a valuable support to European research centres and industry. This paper reviews the main results achieved in the COST 271 Action concerning in particular a range of the ionospheric space weather issues, specifically: now-casting, forecasting and warning tools, methods and supporting databases for ionospheric propagation prediction; total electron content variations and their use in the reconstruction of plasmaspheric ionospheric structures as a key parameter for navigation error in GNSS applications and effects of planetary and gravity waves and gradients of the electron density on terrestrial and satellite communications.

  20. Transit Observations of Venus's Atmosphere in 2012 from Terrestrial and Space Telescopes as Exoplanet Analogs

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann, T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Dantowitz, R.

    2013-06-01

    We extensively observed the 8 June 2012 transit of Venus from several sites on Earth; we provide this interim status report about this and about two subsequent ToVs observed from space. From Haleakala Obs., we observed the entire June transit over almost 7 h with a coronagraph of the Venus Twilight Experiment B filter) and with a RED Epic camera to compare with simultaneous data from ESA's Venus Express, to study the Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry at 1.6 µm from the aureole and during the disk crossing that compare well with carbon dioxide spectral models; from Sac Peak/IBIS we have high-resolution imaging of the Cytherean aureole for 22 min, starting even before 1st contact; from Big Bear, we have high-resolution imaging of Venus's atmosphere and the black-drop effect through 2nd contact; and we had 8 other coronagraphs around the world. For the Sept 21 ToV as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds as a reflecting surface to search for an 0.01% diminution in light and a differential drop that would result from Venus's atmosphere by observing in both IR/UV, for which we have 170 HST exposures. As of this writing, preliminary data reduction indicates that variations in Jovian clouds and the two periods of Jupiter's rotation will be too great to allow extraction of the transit signal. For the December 20 ToV as seen from Saturn, we had 22 hours of observing time with VIMS on Cassini, for which we are looking for a signal of the 10-hr transit in total solar irradiance and of Venus's atmosphere in IR as an exoplanet-transit analog. Our Maui & Sac Peak expedition was sponsored by National Geographic Society's Committee for Research and Exploration; HST data reduction by NASA: HST-GO-13067. Some of the funds for the carbon dioxide filter for Sac Peak provided by NASA through AAS's Small Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur Astronomers; Rob Lucas, Aram Friedman, Eric Pilger, Stan Truitt, and Steve Bisque/Software Bisque for Haleakala support/operations; Vasyl Yurchyshyn and Joseph Gangestad '06 of The Aerospace Corp. at Big Bear Solar Obs; LMSAL and Hinode science/operations team.

  1. Solar Terrestrial Influences on the D Region as Shown by the Level of Atmospheric Radio Noise

    NASA Technical Reports Server (NTRS)

    Satori, G.; Schaning, B.

    1984-01-01

    Measurements of the integrated atmospheric radio noise field strength at 27 kHz, used here, were made from 1965 to 1975 at Uppsala, Kuhlungsborn, and Prague-Panska Ves. The large scale meteorological situation was considered by comparing solar disturbed and undisturbed periods under similar weather situations. In order to show the effects of the precipitating high energy particle (HEP) flux and of the Forbush decrease on the noise level between pairs of stations were computed as deviations from the monthly median. Delta E (dB), day by day for all six periods was studied. The correlation coefficients for noon as well as for night values were computed. The correlation coefficients were compared with those for solar undisturbed periods.

  2. Can we reconcile atmospheric estimates of the Northern terrestrial carbon sink with land-based accounting?

    SciTech Connect

    Ciais, Philippe; Luyssaert, Sebastiaan; Chevallier, Fredric; Poussi, Zegbeu; Peylin, Philippe; Breon, Francois-Marie; Canadell, J.G.; Shvidenko, Anatoly; Jonas, Matthias; King, Anthony Wayne; Schulze, E.-D.; Roedenbeck, Christian; Piao, Shilong; Peters, Wouter

    2010-10-01

    We estimatethenorthernhemisphere(NH)terrestrialcarbon sink bycomparingfourrecentatmosphericinversionswith land-based Caccountingdataforsixlargenorthernregions. The meanNHterrestrialCO2 sink fromtheinversionmodelsis 1.7 PgCyear1 over theperiod2000 2004. Theuncertaintyof this estimateisbasedonthetypicalindividual(1-sigma) precision ofoneinversion(0.9PgCyear1) andisconsistent with themin max rangeofthefourinversionmeanestimates (0.8 PgCyear1). Inversionsagreewithintheiruncertaintyfor the distributionoftheNHsinkofCO2 in longitude,withRussia being thelargestsink.Theland-basedaccountingestimateof NH carbonsinkis1.7PgCyear1 for thesumofthesixregions studied. The1-sigmauncertaintyoftheland-basedestimate (0.3 PgCyear1) issmallerthanthatofatmosphericinversions, but noindependentland-basedfluxestimateisavailableto derive a betweenaccountingmodel uncertainty. Encouragingly, thetop-downatmosphericandthebottom-up land-based methodsconvergetoconsistentmeanestimates within theirrespectiveerrors,increasingtheconfidenceinthe overall budget.Theseresultsalsoconfirmthecontinuedcritical role ofNHterrestrialecosystemsinslowingdownthe atmospheric accumulationofanthropogenicCO2

  3. ATCOM: accelerated image processing for terrestrial long-range imaging through atmospheric effects

    NASA Astrophysics Data System (ADS)

    Curt, Petersen F.; Paolini, Aaron

    2013-05-01

    Long-range video surveillance performance is often severely diminished due to atmospheric turbulence. The larger apertures typically used for video-rate operation at long-range are particularly susceptible to scintillation and blurring effects that limit the overall diffraction efficiency and resolution. In this paper, we present research progress made toward a digital signal processing technique which aims to mitigate the effects of turbulence in real-time. Our previous work in this area focused on an embedded implementation for portable applications. Our more recent research has focused on functional enhancements to the same algorithm using general-purpose hardware. We present some techniques that were successfully employed to accelerate processing of high-definition color video streams and study performance under nonideal conditions involving moving objects and panning cameras. Finally, we compare the real-time performance of two implementations using a CPU and a GPU.

  4. The oxidation state of Hadean magmas and implications for early Earth's atmosphere.

    PubMed

    Trail, Dustin; Watson, E Bruce; Tailby, Nicholas D

    2011-12-01

    Magmatic outgassing of volatiles from Earth's interior probably played a critical part in determining the composition of the earliest atmosphere, more than 4,000 million years (Myr) ago. Given an elemental inventory of hydrogen, carbon, nitrogen, oxygen and sulphur, the identity of molecular species in gaseous volcanic emanations depends critically on the pressure (fugacity) of oxygen. Reduced melts having oxygen fugacities close to that defined by the iron-wüstite buffer would yield volatile species such as CH(4), H(2), H(2)S, NH(3) and CO, whereas melts close to the fayalite-magnetite-quartz buffer would be similar to present-day conditions and would be dominated by H(2)O, CO(2), SO(2) and N(2) (refs 1-4). Direct constraints on the oxidation state of terrestrial magmas before 3,850 Myr before present (that is, the Hadean eon) are tenuous because the rock record is sparse or absent. Samples from this earliest period of Earth's history are limited to igneous detrital zircons that pre-date the known rock record, with ages approaching ∼4,400 Myr (refs 5-8). Here we report a redox-sensitive calibration to determine the oxidation state of Hadean magmatic melts that is based on the incorporation of cerium into zircon crystals. We find that the melts have average oxygen fugacities that are consistent with an oxidation state defined by the fayalite-magnetite-quartz buffer, similar to present-day conditions. Moreover, selected Hadean zircons (having chemical characteristics consistent with crystallization specifically from mantle-derived melts) suggest oxygen fugacities similar to those of Archaean and present-day mantle-derived lavas as early as ∼4,350 Myr before present. These results suggest that outgassing of Earth's interior later than ∼200 Myr into the history of Solar System formation would not have resulted in a reducing atmosphere. PMID:22129728

  5. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2

    PubMed Central

    Friend, Andrew D.; Lucht, Wolfgang; Rademacher, Tim T.; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B.; Dankers, Rutger; Falloon, Pete D.; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R.; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F. Ian

    2014-01-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 C of global land surface warming (510758 ppm of CO2), vegetation carbon increases by 52477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

  6. Effect of the shrinking dipole on solar-terrestrial energy input to the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    McPherron, R. L.

    2011-12-01

    The global average temperature of the Earth is rising rapidly. This rise is primarily attributed to the release of greenhouse gases as a result of human activity. However, it has been argued that changes in radiation from the Sun might play a role. Most energy input to the Earth is light in the visible spectrum. Our best measurements suggest this power input has been constant for the last 40 years (the space age) apart from a small 11-year variation due to the solar cycle of sunspot activity. Another possible energy input from the Sun is the solar wind. The supersonic solar wind carries the magnetic field of the Sun into the solar system. As it passes the Earth it can connect to the Earth's magnetic field whenever it is antiparallel t the Earth's field. This connection allows mass, momentum, and energy from the solar wind to enter the magnetosphere producing geomagnetic activity. Ultimately much of this energy is deposited at high latitudes in the form of particle precipitation (aurora) and heating by electrical currents. Although the energy input by this process is miniscule compared to that from visible radiation it might alter the absorption of visible radiation. Two other processes affected by the solar cycle are atmospheric entry of galactic cosmic rays (GCR) and solar energetic protons (SEP). A weak solar magnetic field at sunspot minimum facilitates GCR entry which has been implicated in creation of clouds. Large coronal mass ejections and solar flares create SEP at solar maximum. All of these alternative energy inputs and their effects depend on the strength of the Earth's magnetic field. Currently the Earth's field is decreasing rapidly and conceivably might reverse polarity in 1000 years. In this paper we describe the changes in the Earth's magnetic field and how this might affect GCR, SEP, electrical heating, aurora, and radio propagation. Whether these effects are important in global climate change can only be determined by detailed physical models.

  7. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2.

    PubMed

    Friend, Andrew D; Lucht, Wolfgang; Rademacher, Tim T; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B; Dankers, Rutger; Falloon, Pete D; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F Ian

    2014-03-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

  8. The terrestrial plant and herbivore arms race -- A major control of Phanerozoic atmospheric CO[sub 2

    SciTech Connect

    Olsen, P.E. )

    1993-03-01

    Much recent work points to chemical weathering of continental silicates as the principal control of atmospheric CO[sub 2]. Presently, chemical weathering is mediated by plants. Vascular plants increase chemical weathering by drastically increasing acid leaching through respiration, decay, and microbial symbionts. Through the Phanerozoic the continuing evolution of terrestrial plant communities must have had a major effect on weathering rates. However, the efficacy of plant-induced-weathering is decreased by herbivory, which in turn decreases the invasion of soil by roots and leads to increased physical weathering. The author proposes that the major ice house--hot house cycles of the Devonian-Quaternary were caused by the lag between plant innovations and complete compensation by herbivore-detritivore response. In this way, it seems possible that: (1) the Carboniferous coals are a consequence of limited herbivory and soil litter decomposition and the Permo-Carboniferous glaciations were caused by dramatically increased chemical weathering caused by the previous global spread of vascular plants; (2) the Mesozoic hot house was brought on by massive increases in megaherbivores and litter decomposers; and (3) Cenozoic cooling and Quaternary glaciations resulted from the spread of herbaceous angiosperms and most recently grasslands. Earth's own superherbivory, if continued for tens of millions of years, will brings one back to mid-Mesozoic hot house conditions, not by the burning of fossil fuels, but rather by a global increase in physical over chemical weathering.

  9. A Molecular Approach to the Study of Green Algal Evolution and Early Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Kodner, R. B.; Summons, R. E.; Knoll, A. H.

    2004-12-01

    The biological nature of pre-land plant terrestrial ecosystems remains an enigmatic chapter of the history of life on earth due to lack of fossil evidence. Molecular phylogenies have shown that Charophycean green algae are the closest relatives of the bryophytes, which have been hypothesized to be the earliest divergent land plants. However, there is no fossil evidence to support this relationship nor is there a reliable fossil record of the earliest land plants. Microfossils representing the earliest land plants appear to have a bryophytes affinity based on limited morphological comparisons but this remains controversial. We are applying a biomolecular approach to study both green algal evolution and its relation to bryophytes using the resistant biopolymer algaenan and phytosterols as biological markers. Algaenan has been shown to have high preservation potential and may be the primary component of enigmatic microfossils assumed to be of algal origin. Algaenan and the green algal sterols, stigmasterol and sitosterol, may also be the precursors of n-alkanes and the hydrocarbon stigmastane that are major components of many Neoproterozoic bitumens. The biological nature and phylogenetic distribution of algaenan is still not well understood. Here we explore the presence and structure of algaenans in terrestrial green algae and bryophytes in relation to their phylogenetic distributions.

  10. The production of trace gases by photochemistry and lightning in the early atmosphere

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Tennille, G. M.; Towe, K. M.; Khanna, R. K.

    1986-01-01

    Recent atmospheric calculation suggest that the prebiological atmosphere was most probably composed of nitrogen, carbon dioxide, and water vapor, resulting from volatile outgassing, as opposed to the older view of a strongly reducing early atmosphere composed of methane, ammonia, and hydrogen. Photochemical calculations indicate that methane would have been readily destroyed via reaction with the hydroxyl radical produced from water vapor and that ammonia would have been readily lost via photolysis and rainout. The rapid loss of methane and ammonia, coupled with the absence of a significant source of these gases, suggest that atmospheric methane and ammonia were very short lived, if they were present at all. An early atmosphere of N2, CO2, and H2O is stable and leads to the chemical production of a number of atmospheric species of biological significance, including oxygen, ozone, carbon monoxide, formaldehyde, and hydrogen cyanide. Using a photochemical model of the early atmosphere, the chemical productionof these species over a wide range of atmospheric parameters were investigated. These calculations indicate that early atmospheric levels of O3 were significantly below the levels needed to provide UV shielding. The fate of volcanically emitted sulfur species, e.g., sulfur dioxide and hydrogen sulfide, was investigated in the early atmosphere to assess their UV shielding properties. The photochemical calculations show that these species were of insufficient levels, due in part to their short photochemical lifetimes, to provide UV shielding.

  11. Early terrestrial impact events: Archean spherule layers in the Barberton Greenstone Belt, South Africa

    NASA Astrophysics Data System (ADS)

    Ozdemir, Seda; Koeberl, Christian; Schulz, Toni; Reimold, W. Uwe; Hofmann, Axel

    2015-04-01

    In addition to the oldest known impact structure on Earth, the 2.02-billion-year-old Vredefort Structure in South Africa, the evidence of Early Earth impact events are Archean spherule beds in South Africa and Australia. These spherules have been interpreted as condensation products from impact plumes and molten impact ejecta or/and impact ejecta that were melted during atmospheric re-entry [e.g., 1,2]. The 3.2-3.5 Ga spherule layers in the Barberton Greenstone Belt in South Africa currently represent the oldest known remnants of impact deposits on Earth. Aiming at identification of extraterrestrial components and to determine the diagenetic and metamorphic history of spherule layer intersections recently recovered in the CT3 drill core from the northeastern part of the Barberton Greenstone Belt, we have studied samples from these layers in terms of petrography and geochemistry. All samples, including spherule layer intersections and intercalating country rocks, were studied for mineral identification by optical and electron microscopy, as well as electron microprobe analysis (EPMA) at Natural History Museum Vienna and Museum für Naturkunde Berlin (MfN). Major and trace element compositions were determined via X-ray fluorescence spectrometry at MfN and instrumental neutron activation analysis (INAA) at University of Vienna. Os isotopes were measured by thermal ionization mass spectrometry (N-TIMS) at University of Vienna. Eighteen spherule beds are distributed over 150 meter drill core in CT3. Spherules are variably, deformed or undeformed. The high number of these layers may have been caused by tectonic duplication. Spherule beds are intercalated with shale, chert, carbonate, and/or sulfide deposits (country rocks). The size range of spherules is 0.5 to 2 mm, and some layers exhibit gradation. Shapes of spherules differ from spherical to ovoid, as well as teardrops, and spherules commonly show off-center vesicles, which have been interpreted as a primary characteristic pointing toward an impact origin [3]. Mineralogical and petrographic studies indicate that most of the mineralogy of the spherule layers is secondary due to secondary overprint by alteration and metamorphism. The mineral assemblages comprise quartz, K-feldspar, various muscovite types, phyllosilicates, Mg-siderite, Ti/Fe-Ti oxides, sulfides such as pyrite, pyrrhotite, chalkopyrite, sphalerite, and galena. INAA data show that some spherule layer intersections have extremely high siderophile element contents, with up to 1.60 wt% Ni, 0.69 wt% Cr, 0.05 wt% Co, 2.06 ppm Ir and 0.02 ppm Au, which is considered extraterrestrial component. This is further supported by their chondritic to slightly supercondritic 187Os/188Os ratios (ranging from 0.11 to 0.19), contrasting more radiogenic values of the spherule layer intercalations in comparison to country rocks, and Os concentrations up to ~4312 ppb. References: [1] Artemieva, N.A., and Simonson, B.M., 2012, LPSC 43, abstract #1372. [2] Johnson, B.C., and Melosh, H.J., 2014, Icarus, 228, 347-363. [3] Glass, B.P. and Simonson, B.M., 2012, Elements 8, 15-60.

  12. Biospheric-atmospheric coupling on the early Earth

    NASA Technical Reports Server (NTRS)

    Levine, J. S.

    1991-01-01

    Theoretical calculations performed with a one-dimensional photochemical model have been performed to assess the biospheric-atmospheric transfer of gases. Ozone reached levels to shield the Earth from biologically lethal solar ultraviolet radiation (220-300 nm) when atmospheric oxygen reached about 1/10 of its present atmospheric level. In the present atmosphere, about 90 percent of atmospheric nitrous oxide is destroyed via solar photolysis in the stratosphere with about 10 percent destroyed via reaction with excited oxygen atoms. The reaction between nitrous oxide and excited oxygen atoms leads to the production of nitric oxide in the stratosphere, which is responsible for about 70 percent of the global destruction of oxygen in the stratosphere. In the oxygen/ozone deficient atmosphere, solar photolysis destroyed about 100 percent of the atmospheric nitrous oxide, relegating the production of nitric oxide via reaction with excited oxygen to zero. Our laboratory and field measurements indicate that atmospheric oxygen promotes the biogenic production of N2O and NO via denitrification and the biogenic production of methane by methanogenesis.

  13. Impacts and atmospheric erosion on the early Earth

    NASA Technical Reports Server (NTRS)

    Vickery, A. M.

    1991-01-01

    It was suggested that heating and/or vaporization of accreting carbonaceous-chondrite-type planetestimals could result in the release of their volatile components. Modeling of this process strongly suggests that substantial atmospheres/hydrospheres could develop this way. During most of the accretionary process, impact velocities generally differed from the escape velocity of the growing proto-planet because most of the collisions were between bodies in nearly matching orbits. Toward the end of accretion, however, collisions were rarer but more energetic, involving large planetestimals and higher impact velocities. Such impacts result in a net loss of atmosphere from a planet, and the cumulative effect impacts during the period of heavy bombardment might have dramatically depleted the original atmospheres. Models developed to study atmospheric erosion by impacts on Mars and the interaction of the vapor plume produced by KT impactor on Earth are applied to the case of the evolution of Earth's atmosphere.

  14. A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the Global Carbon Cycle

    SciTech Connect

    Stephen C. Piper

    2005-10-15

    The primary goal of our research program, consistent with the goals of the U.S. Climate Change Science Program and funded by the terrestrial carbon processes (TCP) program of DOE, has been to improve understanding of changes in the distribution and cycling of carbon among the active land, ocean and atmosphere reservoirs, with particular emphasis on terrestrial ecosystems. Our approach is to systematically measure atmospheric CO2 to produce time series data essential to reveal temporal and spatial patterns. Additional measurements of the 13C/12C isotopic ratio of CO2 provide a basis for distinguishing organic and inorganic processes. To pursue the significance of these patterns further, our research also involved interpretations of the observations by models, measurements of inorganic carbon in sea water, and of CO2 in air near growing land plants.

  15. Stepwise atmospheric carbon-isotope excursion during the Toarcian Oceanic Anoxic Event (Early Jurassic, Polish Basin)

    NASA Astrophysics Data System (ADS)

    Hesselbo, Stephen P.; Pieńkowski, Grzegorz

    2011-01-01

    During the Mesozoic (250-64 Ma) intervals of about 0.5 Myr were subject to severe environmental changes, including high sea-surface temperature and very low oxygen content of marine water. These Oceanic Anoxic Events, or OAEs, occurred simultaneously with profound disturbance to the carbon cycle. The carbon-isotope anomaly in the Early Jurassic that marks the Toarcian Oceanic Anoxic Event (T-OAE) at ~ 182 Ma is characterized in marine sections by a series of dramatic steps towards lighter values. Herein we present new carbon-isotope data from terrestrial organic matter (phytoclast separates), collected through a Late Pliensbachian-Middle Toarcian coastal and marginal marine succession in the Polish Basin, a setting where hinterland climate and sea-level change are well recorded. The results show that the shift to light carbon-isotope values in the woody organic matter, and therefore also in atmospheric carbon dioxide, similarly occurred in major steps. The steps are here correlated with those identified from marine organic matter, where they have previously been attributed to 100 kyr eccentricity forcing of climate. The results provide strong support for orbitally and climatically controlled release of isotopically light carbon from gas hydrates into the ocean-atmosphere system in a series of rapid bursts. Additionally, a link between the carbon-isotope steps and shoreline movements can be demonstrated. Individual peaks of the negative excursion are mostly associated with facies indicative of sea-level rise (flooding surfaces). However, at the same time inferred higher atmospheric carbon-dioxide content may be expected to have resulted in increased rainfall and temperature, leading to accelerated weathering and erosion, and consequently increased sediment supply, progradation and regression, causing some mismatches between isotope shifts and inferred sea-level changes. Enhanced abundance of megaspores derived from hydrophilic plant groups, and marked increase in kaolinite, are coincident with the overall development of the negative isotope excursion. The combined data suggest that each 100-kyr cycle in carbon-isotope values was characterized by increasingly severe palaeoclimatic change, culminating in extremely hot and humid conditions co-incident with the peak of the final most negative carbon-isotope excursion. The chemostratigraphic correlation allows very precise dating of the Late Pliensbachian-Middle Toarcian coastal and marginal marine sedimentary succession in the Polish Basin.

  16. Removal of CO2 from the terrestrial atmosphere to curtail global warming: From methodology to laboratory prototype

    NASA Astrophysics Data System (ADS)

    Orton, Andrea E.

    This research has focused on the initial phase of required investigations in pursuit of a global scale methodology for reduction of CO 2 in terrestrial air for the purpose of curtailment of global warming. This methodology was initially presented by Agee, Orton, and Rogers (2013), and has provided the basis for pursuing this thesis research. The first objective of the research project was to design and build a laboratory prototype system, capable of depleting CO2 from terrestrial air at 1 bar of pressure through LN2 refrigeration. Design considerations included a 26.5L cylindrical Pyrex glass sequestration chamber, a container to hold a reservoir of LN2 and an interface between the two to allow for cooling and instrumentation ports for measurements inside the sequestration chamber. Further, consideration was given to the need for appropriate insulating material to enclose the assembled apparatus to help achieve efficient cooling and the threshold depositional temperature of 135 K. The Amy Facility in the Department of Chemistry provided critical expertise to machine the apparatus to specifications, especially the stainless steel interface plate. Research into available insulating materials resulted in the adaption of TRYMER RTM 2500 Polyisocyanurate, effective down to 90 K. The above described DAC prototype designed for CO2 sequestration accomplished two of the initial research objectives investigated: 1) conduct refrigeration experiments to achieve CO2 terrestrial deposition temperature of 135 K (uniformly) and 2) deplete CO2 from the chamber air at 1 bar of pressure, documented by appropriate measurements. It took approximately 5.5 hours for the chamber to be completely uniform in temperature of 135 K (and below) through the use of LN2 poured into the container sitting on an aluminum interface on top of the sequestration Pyrex chamber. As expected, Rayleigh-Taylor instability (more dense fluid over less dense fluid) was observed through the duration of the experiments, which helped to achieve approximate uniform temperature within the sequestration chamber. The lowest temperature achieved in any experiment was 125 K. Using ambient laboratory air to fill the chamber naturally, CO2 depletion was observed to be 90% with residual CO2 contained in air that was pulled through the leaks into the sequestration chamber. CO2 values were taken from 440-500 ppmv down to 30-50 ppmv, in the series of experiments executed. An appropriate new consideration for the sequestration process is to determine how the CO2 is being deposited within the chamber, i.e. on the base of the aluminum plate (and possibly the side walls of the chamber) in the form of frost, or as a CO2 cloud of suspended dry ice particles through deposition of CO2 gas onto Ice Nuclei (IN), or by a combination of both processes. Although this was an early envisioned research goal, such was not pursued in this M.S. thesis research. Further, CO2 snow would only be expected if large amounts of CO2 gas were sequestered, producing a precipitating cloud.

  17. Seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere: extrapolation from site-specific models to regional models

    SciTech Connect

    King, A.W.

    1986-01-01

    Ecological models of the seasonal exchange of carbon dioxide (CO/sub 2/) between the atmosphere and the terrestrial biosphere are needed in the study of changes in atmospheric CO/sub 2/ concentration. In response to this need, a set of site-specific models of seasonal terrestrial carbon dynamics was assembled from open-literature sources. The collection was chosen as a base for the development of biome-level models for each of the earth's principal terrestrial biomes or vegetation complexes. The primary disadvantage of this approach is the problem of extrapolating the site-specific models across large regions having considerable biotic, climatic, and edaphic heterogeneity. Two methods of extrapolation were tested. The first approach was a simple extrapolation that assumed relative within-biome homogeneity, and generated CO/sub 2/ source functions that differed dramatically from published estimates of CO/sub 2/ exchange. The second extrapolation explicitly incorporated within-biome variability in the abiotic variables that drive seasonal biosphere-atmosphere CO/sub 2/ exchange.

  18. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Zahnle, K. J.

    1986-01-01

    A one-dimensional photochemical model is used to analyze the photochemistries of CH4 and HCN in the primitive terrestrial atmosphere. CH4, N2, and HCN photolysis are examined. The background atmosphere and boundary conditions applied in the analysis are described. The formation of HCN as a by-product of N2 and CH4 photolysis is investigated; the effects of photodissociation and rainfall on HCN is discussed. The low and high CH4 mixing ratios and radical densities are studied.

  19. Long-range atmospheric transport of terrestrial biomarkers by the Asian winter monsoon: Evidence from fresh snow from Sapporo, northern Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu

    2011-07-01

    Molecular distributions of terrestrial biomarkers were investigated in fresh snow samples from Sapporo, northern Japan, to better understand the long-range atmospheric transport of terrestrial organic matter by the Asian winter monsoon. Stable carbon (δ 13C) and hydrogen (δD) isotope ratios of C 22-C 28n-alkanoic acids were also measured to decipher their source regions. The snow samples are found to contain higher plant-derived n-alkanes, n-alkanols and n-alkanoic acids as major components. Relative abundances of these three biomarker classes suggest that they are likely derived from higher plants in the Asian continent. The C 27/C 31 ratios of terrestrial n-alkanes in the snow samples range from 1.3 to 5.5, being similar to those of the plants growing in the latitudes >40°N of East Asia. The δ 13C values of the n-alkanoic acids in the snow samples (-33.4 to -27.6‰) are similar to those of typical C 3 gymnosperm from Sapporo (-34.9 to -29.3‰). However, the δD values of the n-alkanoic acids (-208 to -148‰) are found to be significantly depleted with deuterium (by ˜72‰) than those of plant leaves from Sapporo. Such depletion can be most likely interpreted by the long-range atmospheric transport of the n-alkanoic acids from vegetation in the latitudes further north of Sapporo because the δD values of terrestrial higher plants tend to decrease northward in East Asia reflecting the δD of precipitation. Together with the results of backward trajectory analyses, this study suggests that the terrestrial biomarkers in the Sapporo snow samples are likely transported from Siberia, Russian Far East and northeast China to northern Japan by the Asian winter monsoon.

  20. Early archean spherule beds in the Barberton mountain land, South Africa: Impact or terrestrial origin?

    NASA Astrophysics Data System (ADS)

    Reimold, Wolf Uwe; Koeberl, Christian; Johnson, Steven; McDonald, Iain

    The origin of multiple spherule-rich layers of millimeter to meter width, all occurring within the transition from the Fig Tree to the Onverwacht Group of the Barberton Greenstone Belt in South Africa, has been strongly debated during the last decade. One school subscribes to an origin by large meteorite impact, whereas others have preferred terrestrial processes. In particular, strong enrichments in siderophile elements, especially Ir, and chondrite-like PGE patterns for spherule layer samples have been cited as evidence favoring an impact origin. Recently, Cr isotopic signatures obtained for samples from two spherule layers have provided further support for this hypothesis. In contrast, our group has emphasized that secondary hydrothermal processes have pervasively overprinted the whole stratigraphy at this transition. Ir concentrations up to 5 times chondritic are suspect as primary impact-produced signatures. Here, we report new petrographic and geochemical data for samples from spherulitic horizons marking the S2 layer and from interlayered BIF, chert, and mudstone strata. In contrast to earlier work, the new samples were obtained from outside of the gold-sulfide mineralized ore zone on Agnes Mine. Both spherule and country rock samples are enriched in siderophile elements, with up to >1500 ppb Ir. Some of the highest values are related to clearly secondary fault and shear zone deposits. Chrome-spinel in spherule layers is often zoned. A proton microprobe study identified in one case the mineral gersdorffite, of likely secondary origin, as a carrier phase for Ir, whereas in other samples Ir must be contained in matrix silicates. New PGE analyses for more or less sulfidemineralized samples yielded uniformly flat, near-chondritic patterns.

  1. Differentiating pedogenesis from diagenesis in early terrestrial paleoweathering surfaces formed on granitic composition parent materials

    USGS Publications Warehouse

    Driese, S.G.; Medaris, L.G., Jr.; Ren, M.; Runkel, Anthony C.; Langford, R.P.

    2007-01-01

    Unconformable surfaces separating Precambrian crystalline basement and overlying Proterozoic to Cambrian sedimentary rocks provide an exceptional opportunity to examine the role of primitive soil ecosystems in weathering and resultant formation of saprolite (weathered rock retaining rock structure) and regolith (weathered rock without rock structure), but many appear to have been affected by burial diagenesis and hydrothermal fluid flow, leading some researchers to discount their suitability for such studies. We examine one modern weathering profile (Cecil series), four Cambrian paleoweathering profiles from the North American craton (Squaw Creek, Franklin Mountains, Core SQ-8, and Core 4), one Neoproterozoic profile (Sheigra), and one late Paleoproterozoic profile (Baraboo), to test the hypothesis that these paleoweathering profiles do provide evidence of primitive terrestrial weathering despite their diagenetic and hydrothermal overprinting, especially additions of potassium. We employ an integrated approach using (1) detailed thin-section investigations to identify characteristic pedogenic features associated with saprolitization and formation of well-drained regoliths, (2) electron microprobe analysis to identify specific weathered and new mineral phases, and (3) geochemical mass balance techniques to characterize volume changes during weathering and elemental gains and losses of major and minor elements relative to the inferred parent materials. There is strong pedogenic evidence of paleoweathering, such as clay illuviation, sepic-plasmic fabrics, redoximorphic features, and dissolution and alteration of feldspars and mafic minerals to kaolinite, gibbsite, and Fe oxides, as well as geochemical evidence, such as whole-rock losses of Na, Ca, Mg, Si, Sr, Fe, and Mn greater than in modern profiles. Evidence of diagenesis includes net additions of K, Ba, and Rb determined through geochemical mass balance, K-feldspar overgrowths in overlying sandstone sections, and K-feldspars with reaction rims in weathered basement. The sub-Cambrian paleoweathering profiles formed on granite are remarkably similar to modern weathering profiles formed on granite, in spite of overprinting by potassium diagenesis. ?? 2007 by The University of Chicago. All rights reserved.

  2. Beyond the atmosphere: Early years of space science

    NASA Technical Reports Server (NTRS)

    Newell, H. E.

    1980-01-01

    From the rocket measurements of the upper atmosphere and Sun that began in 1946, space science gradually emerged as a new field of scientific activity. The course of the United State space program is viewed in an historical context. Major emphasis is on NASA and its programs. The funding, staffing, organization, and priorities of the space program were reviewed.

  3. Biological modulation of planetary atmospheres: The early Earth scenario

    NASA Astrophysics Data System (ADS)

    Schidlowski, M.

    The establishment and subsequent evolution of life on Earth had a profound impact on the chemical regime at the planet's surface and its atmosphere. A thermodynamic gradient was imposed on near-surface environments that served as the driving force for a number on important geochemical transformations. An example is the redox imbalance between the modern atmosphere and the material of the Earth's crust. Current photochemical models predict extremely low partial pressures of oxygen in the Earth's prebiological atmosphere. There is widespread consensus that any large-scale oxygenation of the primitive atmosphere was contingent on the advent of biological (autotrophic) carbon fixation. It is suggested that photoautotrophy existed both as a biochemical process and as a geochemical agent since at least 3.8 Ga ago. Combining the stoichiometry of the photosynthesis reaction with a carbon isotope mass balance and current concepts for the evolution of the stationary sedimentary mass as a funion of time, it is possible to quantify, the accumulation of oxygen and its photosynthetic oxidation equivalents through Earth history.

  4. Early harvest: The upper atmosphere and cosmic rays

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Achievements in space science through 1958 are summarized. Topics discussed are: the scheduling of V-2 flights; the development of newer rockets; the testing of spaceborne instruments; the seeking of financial support for space research; and the problems of international cooperation. Special emphasis is placed on atmospheric sounding.

  5. Thermal expansion and thermal stress in the moon and terrestrial planets - Clues to early thermal history

    NASA Technical Reports Server (NTRS)

    Solomon, S. C.; Chaiken, J.

    1976-01-01

    The paper discusses how features of the surface geology of the moon and also Mars and Mercury impose constraints on the volumetric expansion or contraction of a planet and consequently provide a test of thermal history models. The moon has changed very little in volume over the last 3.8 b.y. Thermal models satisfying this constraint involve early heating and perhaps melting of the outer 200 km of the moon and an initially cold interior. Mercury has contracted by about 2 km in radius since emplacement of its present surface, so core formation must predate that surface. A hot initial temperature distribution is implied.

  6. The role of terrestrial vegetation in atmospheric Hg deposition: Pools and fluxes of spike and ambient Hg from the METAALICUS experiment

    NASA Astrophysics Data System (ADS)

    Graydon, Jennifer A.; St. Louis, Vincent L.; Lindberg, Steve E.; Sandilands, Ken A.; Rudd, John W. M.; Kelly, Carol A.; Harris, Reed; Tate, Michael T.; Krabbenhoft, Dave P.; Emmerton, Craig A.; Asmath, Hamish; Richardson, Murray

    2012-03-01

    As part of the Mercury Experiment to Assess Atmospheric Loading in Canada and the U.S. (METAALICUS), different stable Hg(II) isotope spikes were applied to the upland and wetland areas of a boreal catchment between 2001 and 2006 to examine retention of newly deposited Hg(II). In the present study, a Geographical Information Systems (GIS)-based approach was used to quantify canopy and ground vegetation pools of experimentally applied upland and wetland spike Hg within the METAALICUS watershed over the terrestrial loading phase of the experiment. A chemical kinetic model was also used to describe the changes in spike Hg concentrations of canopy and ground vegetation over time. An examination of the fate of spike Hg initially present on canopy vegetation using a mass balance approach indicated that the largest percentage flux from the canopy over one year post-spray was emission to the atmosphere (upland: 45%; wetland: 71%), followed by litterfall (upland: 14%; wetland: 10%) and throughfall fluxes (upland: 12%; wetland: 9%) and longer term retention of spike in the forest canopy (11% for both upland and wetland). Average half-lives (t1/2) of spike on deciduous (110 ± 30 days) and coniferous (180 ± 40 days) canopy and ground vegetation (890 ± 620 days) indicated that retention of new atmospheric Hg(II) on terrestrial (especially ground) vegetation delays downward transport of new atmospheric Hg(II) into the soil profile and runoff into lakes.

  7. Water loss from Venus: Implications for the Earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Richardson, S. M.; Pollack, J. B.; Reynolds, R. T.

    1985-01-01

    The atmosphere of Venus outgassed rapidly as a result of planetary heating during accretion, resulting in massive water loss. The processes affecting atmospheric chemistry following accretion have consisted largely of hydrogen escape and internal re-equilibrium. The initial bulk composition of Venus and Earth are assumed to have been roughly similar. Chemical speciation on Venus was controlled by the temperature and oxygen buffering capacity of the surface magma. It is also assumed that the surfaces of planetary bodies of the inner solar system were partly or wholly molten during accretion with a temperature estimated at 1273 to 1573 K. To investigate the range of reasonable initial atmospheric compositions on Venus, limits have to be set for the proportion of total hydrogen and the buffered fugacity of oxygen. Using the C/H ratio of 0.033 set for Earth, virtually all of the water generated during outgassing must later have been lost in order to bring the current CO2/H2O ratio for Venus up to its observed value of 10 sup 4 to 10 sup 5. The proportion of H2O decreases in model atmospheres with successfully higher C/H values, ultimately approaching the depleted values currently observed on Venus. Increasing C/H also results in a rapid increase in CO/H2O and provides an efficient mechanism for water loss by the reaction CO+H2O = CO2 + H2. This reaction, plus water loss mechanisms involving crustal iron, could have removed a very large volume of water from the Venusian atmosphere, even at a low C/H value.

  8. Early public impressions of terrestrial carbon capture and storage in a coal-intensive state.

    PubMed

    Carley, Sanya R; Krause, Rachel M; Warren, David C; Rupp, John A; Graham, John D

    2012-07-01

    While carbon capture and storage (CCS) is considered to be critical to achieving long-term climate-protection goals, public concerns about the CCS practice could pose significant obstacles to its deployment. This study reports findings from the first state-wide survey of public perceptions of CCS in a coal-intensive state, with an analysis of which factors predict early attitudes toward CCS. Nearly three-quarters of an Indiana sample (N = 1001) agree that storing carbon underground is a good approach to protecting the environment, despite 80% of the sample being unaware of CCS prior to participation in the two-wave survey. The majority of respondents do not hold strong opinions about CCS technology. Multivariate analyses indicate that support for CCS is predicted by a belief that humankind contributes to climate change, a preference for increased use of renewable energy, and egalitarian and individualistic worldviews, while opposition to CCS is predicted by self-identified political conservatism and by selective attitudes regarding energy and climate change. Knowledge about early impressions of CCS can help inform near-term technology decisions at state regulatory agencies, utilities, and pipeline companies, but follow-up surveys are necessary to assess how public sentiments evolve in response to image-building efforts with different positions on coal and CCS. PMID:22681614

  9. Contributions of icy planetesimals to the Earth's early atmosphere.

    PubMed

    Owen, T C; Bar-Nun, A

    2001-01-01

    Laboratory experiments on the trapping of gases by ice forming at low temperatures implicate comets as major carriers of the heavy noble gases to the inner planets. These icy planetesimals may also have brought the nitrogen compounds that ultimately produced atmospheric N2. However, if the sample of three comets analyzed so far is typical, the Earth's oceans cannot have been produced by comets alone, they require an additional source of water with low D/H. The highly fractionated neon in the Earth's atmosphere may also indicate the importance of non-icy carriers of volatiles. The most important additional carrier is probably the rocky material comprising the bulk of the mass of these planets. Venus may require a contribution from icy planetesimals formed at the low temperatures characteristic of the Kuiper Belt. PMID:11599179

  10. Early Cretaceous terrestrial ecosystems in East Asia based on food-web and energy-flow models

    USGS Publications Warehouse

    Matsukawa, M.; Saiki, K.; Ito, M.; Obata, I.; Nichols, D.J.; Lockley, M.G.; Kukihara, R.; Shibata, K.

    2006-01-01

    In recent years, there has been global interest in the environments and ecosystems around the world. It is helpful to reconstruct past environments and ecosystems to help understand them in the present and the future. The present environments and ecosystems are an evolving continuum with those of the past and the future. This paper demonstrates the contribution of geology and paleontology to such continua. Using fossils, we can make an estimation of past population density as an ecosystem index based on food-web and energy-flow models. Late Mesozoic nonmarine deposits are distributed widely on the eastern Asian continent and contain various kinds of fossils such as fishes, amphibians, reptiles, dinosaurs, mammals, bivalves, gastropods, insects, ostracodes, conchostracans, terrestrial plants, and others. These fossil organisms are useful for late Mesozoic terrestrial ecosystem reconstruction using food-web and energy-flow models. We chose Early Cretaceous fluvio-lacustrine basins in the Choyr area, southeastern Mongolia, and the Tetori area, Japan, for these analyses and as a potential model for reconstruction of other similar basins in East Asia. The food-web models are restored based on taxa that occurred in these basins. They form four or five trophic levels in an energy pyramid consisting of rich primary producers at its base and smaller biotas higher in the food web. This is the general energy pyramid of a typical ecosystem. Concerning the population densities of vertebrate taxa in 1 km2 in these basins, some differences are recognized between Early Cretaceous and the present. For example, Cretaceous estimates suggest 2.3 to 4.8 times as many herbivores and 26.0 to 105.5 times the carnivore population. These differences are useful for the evaluation of past population densities of vertebrate taxa. Such differences may also be caused by the different metabolism of different taxa. Preservation may also be a factor, and we recognize that various problems occur in past ecosystem reconstructions. Counts of small numbers of confirmed species and estimates of maximum numbers of species present in the basin are used for the analysis and estimation of energy flow. This approach applies the methods of modern ecosystem analysis. ?? 2005 Elsevier Ltd. All rights reserved.

  11. Atmospheric carbon dioxide as a driver for deglaciation during the Mi-1 event: new evidence from terrestrial Southern Hemisphere proxies

    NASA Astrophysics Data System (ADS)

    Fox, B.; Wilson, G. S.; Lee, D.; Haworth, M.; Wartho, J.; Kaulfuss, U.; Bannister, J.; Gorman, A. R.; Jones, D. A.; Lindqvist, J.

    2011-12-01

    Foulden Maar is an annually-resolved maar lake deposit dating from the Oligocene/Miocene boundary. The deposit, from the South Island of New Zealand, is the first high-resolution terrestrial record of the O/M boundary and the rapid deglaciation of Antarctica that occurred during the second half of the Mi-1 event. A ~180 m core from the centre of the lake bed comprises ~60 m of basal graded breccias, sands and muds overlain by ~120 m of diatomite punctuated by volcanogenic horizons. The basal siliciclastic sediments contain clasts of basalt and country rock and are interpreted as diatreme breccias coeval with the formation of the maar. The diatomite succession consists of mm-scale light-dark couplets and diatomaceous turbidites. Radiometric dates were obtained from basaltic clasts found at ~110 m depth (close to the base of the diatomite sucession) in a slump deposit of crater wall material. These give ages of 23.45 ± 0.25 Ma and 23.68 ± 0.36 Ma. A nearby basaltic dyke formed during the same episode of volcanism as the maar crater gives a date of 23.17 ± 0.17 Ma. A magnetic reversal occurs at ~106 m depth in the core, constraining the age of this point to 23.34 Ma (the base of chron C6Cn.3n) or 23.03 Ma (the base of chron C6Cn.2n). Spectral analysis of physical properties measurements of the diatomite section of the core reveals obliquity and precessional frequencies. An age model based on these frequencies shows that individual light-dark couplets of diatomite represent annual varves and that the normally magnetised section from ~106 m depth to the top of the core covers ~100,000 years. This rules out C6Cn.3n, which is only 50,000 years long, placing the base of the diatomite succession at the Oligocene-Miocene boundary and the peak of the Mi-1 event. We have collected stomatal index values from Litsea and Podocarpus leaves found in the succession. The Podocarpus values are calibrated using Podocarpus plants grown at various concentrations of carbon dioxide from 380 ppmv to 1500 ppmv. The Litsea values are calibrated using published SI values for various Litsea species of similar morphology and inferred ecology (the NLE approach). Our results show an atmospheric carbon dioxide level of ~400 ppmv at ~23.01 Ma (77 m depth below the top of the core), with concentration increasing to ~800-1200 ppmv at ~22.98 Ma (55 m) and dropping back to ~400-600 ppmv at ~22.9 Ma (0 m, the present-day surface outcrop). This short-lived, rapid increase in atmospheric carbon dioxide concentration coincides with the initiation of the deglaciation phase of the Mi-1 event and implies that CO2 was the driver of this deglaciation.

  12. Net exchanges of CO2, CH4, and N2O between China's terrestrial ecosystems and the atmosphere and their contributions to global climate warming

    NASA Astrophysics Data System (ADS)

    Tian, Hanqin; Xu, Xiaofeng; Lu, Chaoqun; Liu, Mingliang; Ren, Wei; Chen, Guangsheng; Melillo, Jerry; Liu, Jiyuan

    2011-06-01

    China's terrestrial ecosystems have been recognized as an atmospheric CO2 sink; however, it is uncertain whether this sink can alleviate global warming given the fluxes of CH4 and N2O. In this study, we used a process-based ecosystem model driven by multiple environmental factors to examine the net warming potential resulting from net exchanges of CO2, CH4, and N2O between China's terrestrial ecosystems and the atmosphere during 1961-2005. In the past 45 years, China's terrestrial ecosystems were found to sequestrate CO2 at a rate of 179.3 Tg C yr-1 with a 95% confidence range of (62.0 Tg C yr-1, 264.9 Tg C yr-1) while emitting CH4 and N2O at rates of 8.3 Tg C yr-1 with a 95% confidence range of (3.3 Tg C yr-1, 12.4 Tg C yr-1) and 0.6 Tg N yr-1 with a 95% confidence range of (0.2 Tg N yr-1, 1.1 Tg N yr-1), respectively. When translated into global warming potential, it is highly possible that China's terrestrial ecosystems mitigated global climate warming at a rate of 96.9 Tg CO2eq yr-1 (1 Tg = 1012 g), substantially varying from a source of 766.8 Tg CO2eq yr-1 in 1997 to a sink of 705.2 Tg CO2eq yr-1 in 2002. The southeast and northeast of China slightly contributed to global climate warming; while the northwest, north, and southwest of China imposed cooling effects on the climate system. Paddy land, followed by natural wetland and dry cropland, was the largest contributor to national warming potential; forest, followed by woodland and grassland, played the most significant role in alleviating climate warming. Our simulated results indicate that CH4 and N2O emissions offset approximately 84.8% of terrestrial CO2 sink in China during 1961-2005. This study suggests that the relieving effects of China's terrestrial ecosystems on climate warming through sequestering CO2 might be gradually offset by increasing N2O emission, in combination with CH4 emission.

  13. Effects of giant impacts on the mantle and atmosphere of terrestrial planets at medium and long time scales.

    NASA Astrophysics Data System (ADS)

    Gillmann, C.; Golabek, G.; Tackley, P.

    2015-10-01

    Our main interest is to understand how surface conditions change during a planet's evolution and which mechanisms are most important. Therefore,we investigate howthe coupled evolution of Venus' atmosphere and mantle is modified by giant impacts. We focus on volatile fluxes in and out of the atmosphere: atmospheric escape and degassing. We link those processes into a coupled model of mantle convection and atmospheric evolution. Feedback of the atmosphere on the mantle is included via surface temperature. As large impacts are capable of contributing to atmospheric escape, volatile replenishment and energy transfer, we estimate their effects on the evolution of Venus.

  14. Early hominin diet included diverse terrestrial and aquatic animals 1.95 Ma in East Turkana, Kenya

    PubMed Central

    Braun, David R.; Harris, John W. K.; Levin, Naomi E.; McCoy, Jack T.; Herries, Andy I. R.; Bamford, Marion K.; Bishop, Laura C.; Richmond, Brian G.; Kibunjia, Mzalendo

    2010-01-01

    The manufacture of stone tools and their use to access animal tissues by Pliocene hominins marks the origin of a key adaptation in human evolutionary history. Here we report an in situ archaeological assemblage from the Koobi Fora Formation in northern Kenya that provides a unique combination of faunal remains, some with direct evidence of butchery, and Oldowan artifacts, which are well dated to 1.95 Ma. This site provides the oldest in situ evidence that hominins, predating Homo erectus, enjoyed access to carcasses of terrestrial and aquatic animals that they butchered in a well-watered habitat. It also provides the earliest definitive evidence of the incorporation into the hominin diet of various aquatic animals including turtles, crocodiles, and fish, which are rich sources of specific nutrients needed in human brain growth. The evidence here shows that these critical brain-growth compounds were part of the diets of hominins before the appearance of Homo ergaster/erectus and could have played an important role in the evolution of larger brains in the early history of our lineage. PMID:20534571

  15. Seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere: extrapolation from site-specific models to regional models

    SciTech Connect

    King, A.W.

    1986-01-01

    Ecological models of the seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere are needed in the study of changes in atmospheric CO/sub 2/ concentration. In response to this need, a set of site-specific models of seasonal terrestrial carbon dynamics was assembled from open-literature sources. The collection was chosen as a base for the development of biome-level models for each of the earth's principal terrestrial biomes or vegetation complexes. Two methods of extrapolation were tested. The first approach was a simple extrapolation that assumed relative within-biome homogeneity, and generated CO/sub 2/ source functions that differed dramatically from published estimates of CO/sub 2/ exchange. The differences were so great that the simple extrapolation was rejected as a means of incorporating site-specific models in a global CO/sub 2/ source function. The second extrapolation explicitly incorporated within-biome variability in the abiotic variables that drive seasonal biosphere-atmosphere CO/sub 2/ exchange. Simulated site-specific CO/sub 2/ dynamics were treated as a function of multiple random variables. The predicated regional CO/sub 2/ exchange is the computed expected value of simulated site-specific exchanges for that region times the area of the region. The test involved the regional extrapolation of tundra and a coniferous forest carbon exchange model. Comparisons between the CO/sub 2/ exchange estimated by extrapolation and published estimates of regional exchange for the latitude belt support the appropriateness of extrapolation by expected value.

  16. Terrestrial Planets: Comparative Planetology

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Papers were presented at the 47th Annual Meteoritical Society Meeting on the Comparative planetology of Terrestrial Planets. Subject matter explored concerning terrestrial planets includes: interrelationships among planets; plaentary evolution; planetary structure; planetary composition; planetary Atmospheres; noble gases in meteorites; and planetary magnetic fields.

  17. LONG-RANGE ATMOSPHERIC TRANSPORT AND DEPOSITION OF ANTHROPOGENIC CONTAMINANTS AND THEIR POTENTIAL EFFECTS ON TERRESTRIAL ECOSYSTEMS

    EPA Science Inventory

    Through the processes of atmospheric transport and deposition, many anthropogenic contaminants such as industrial organics, pesticides, and trace metals have become widely distributed around the globe. ue to the phenomenon of long-range atmospheric transport, even the most remote...

  18. Early MAVEN Results on the Mars Upper Atmosphere and Atmospheric Loss to Space

    NASA Astrophysics Data System (ADS)

    Jakosky, Bruce; Grebowsky, Joe; Luhmann, Janet

    2015-04-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft went into orbit around Mars on 21 September 2014. After a commissioning phase that included science observations of Mars and of Comet Siding Spring during its close approach, its primary science phase began on 16 November 2014 and will run for a full Earth year, until November 2015.The science objectives of the MAVEN mission are to characterize the upper atmosphere and ionospheric structure and composition, the interactions of the sun and the solar wind with the planet, and the processes driving loss of gas from the atmosphere to space. Our goal is to understand the chain of processes leading to escape today, learn how to extrapolate back in time, and determine the integrated escape of atmosphere over Martian history.MAVEN has nine instrument sensors collected into eight separate instruments. The first group of instruments measures the properties of the solar wind and of the sun that drive the processes in the upper atmosphere. The second group measures the structure and composition of the upper atmosphere and of the ions in the ionosphere, and also measures isotope ratios that can tell us about the integrated escape to space. In this group, NGIMS measures properties in situ at the location of the spacecraft, and IUVS measures them remotely, providing a powerful combination of local and global measurements. The third group measures the properties of the ionosphere that both drive escape and determine the composition and properties of the escaping ions.The spacecraft and all science instruments are functioning nominally, and science data is being collected utilizing our planned observing scenarios. The first deep-dip campaign is scheduled for the second week of February 2015.By the time of the TESS meeting, we expect to have a preliminary understanding of the instrument behavior, operations, and calibrations. We also expect to have sufficient data collected to allow us to reach preliminary conclusions about the state of the upper atmosphere, interactions with the solar wind, escape of atmospheric gas to space at the present epoch, and integrated escape to space over time.

  19. Integrated Estimates of Global Terrestrial Carbon Sequestration

    SciTech Connect

    Thomson, Allison M.; Izaurralde, R Cesar; Smith, Steven J.; Clarke, Leon E.

    2008-02-01

    Assessing the contribution of terrestrial carbon sequestration to international climate change mitigation requires integration across scientific and disciplinary boundaries. As part of a scenario analysis for the US Climate Change Technology Program, measurements and geographic data were used to develop terrestrial carbon sequestration estimates for agricultural soil carbon, reforestation and pasture management. These estimates were then applied in the MiniCAM integrated assessment model to evaluate mitigation strategies within policy and technology scenarios aimed at achieving atmospheric CO2 stabilization by 2100. Adoption of terrestrial sequestration practices is based on competition for land and economic markets for carbon. Terrestrial sequestration reach a peak combined rate of 0.5 to 0.7 Gt carbon yr-1 in mid-century with contributions from agricultural soil (0.21 Gt carbon yr-1), reforestation (0.31 Gt carbon yr-1) and pasture (0.15 Gt carbon yr-1). Sequestration rates vary over time period and with different technology and policy scenarios. The combined contribution of terrestrial sequestration over the next century ranges from 31 to 41 GtC. The contribution of terrestrial sequestration to mitigation is highest early in the century, reaching up to 20% of total carbon mitigation. This analysis provides insight into the behavior of terrestrial carbon mitigation options in the presence and absence of climate change mitigation policies.

  20. Role of land atmosphere interactions in WCRP - overview of the terrestrial component of GEWEX and the observing networks and field campaigns

    NASA Astrophysics Data System (ADS)

    Try, P.

    2002-06-01

    The Global Energy and Water Cycle Experiment (GEWEX) of the World Climate Research Programme (WCRP) has been designed to observe and model the hydrologic cycle and energy fluxes in the atmosphere, at the land surface, and in the upper oceans. GEWEX is an integrated program of research, observations, and science activities ultimately leading to the prediction of global and regional climate change. The objectives of the GEWEX Program are to: -- determine the hydrological cycle and energy fluxes by means of global measurements of atmospheric and surface properties; -- model the global hydrological cycle and its impact on the atmosphere, oceans and land surfaces; -- develop the ability to predict the variations of global and regional hydrological processes and water resources, and their response to environmental change; and, -- advance the development of observing techniques, data management, and assimiliation systems for operational application to long-range weather forecasts, hydrology, and climate predictions. The primary activities of GEWEX are a) global data set development, b) process studies, c) model development support. To accomplish this, GEWEX has many components to address the critical elements with roles in the energy and water cycles. The data projects focus on global distribution and variability of clouds, water vapour, aerosols, surface radiation, precipitation and the features of the land surface and near surface meteorology that couple the land to the atmosphere. The modelling projects focus on the cloud, land-atmosphere and boundary layer parameterizations necessary to drive our regional and global predictive models. Coupling the land-atmosphere at the mesoscale has been the initial strategy for GEWEX and five major continental-scale field campaigns have been underway to provide new process and modelling understanding in the Amazon, Baltic Sea, Mississippi River Basin, MacKenzie River Basin, and four basins in Asia (Thailand, Tibet, Siberia and China). A West African campaign is also in the planning stages. All of these GEWEX components have elements that consider and address the carbon aspects of the land-atmosphere interactions and GEWEX has two integrating projects to facilitate these activities: the International Satellite Land Surface Climatology Project (ISLSCP) and the Global Land Atmosphere System Study (GLASS). ISLSCP focuses on the field campaigns, data sets and role of carbon exchange in the land-atmosphere coupling while GLASS focuses on the integration and parameterization of key land-atmosphere features in the full range of modelling activities. The major focus of ISLSCP is to improve our understanding of how carbon, energy and water are exchanged between the atmosphere and the terrestrial biosphere as an important component in understanding and predicting climate change. This is done by ISLSCP with the following objectives: -- Demonstrate the types of surface and near-surface satellite measurements that are relevant to climate and global change studies. -- Develop and improve algorithms for the interpretation of satellite measurements of land-surface features. -- Develop methods to validate area-averaged quantities derived from satellite measurements for climate simulation models. -- Prepare the groundwork for future operational production of landsurface data sets, which can be directly applied to climate problems. GEWEX also plays a vital role in the new WCRP-IGBP-IHDP joint Carbon Initiative and there are a series of new developments that impact the new carbon studies related to the interdisciplinary aspects of coupled land-atmosphere-ocean modelling and global observations. The new satellite spectrometer-interferometer instrumentation, improved land-atmosphere coupling in models and new carbon treatment and transport within global atmospheric models, all relate to the overall need for an improved integrated view of the global carbon-ocean-land-atmosphere interactions based on new observations and modelling techniques. This presentation will update the activities and plans of GEWEX as they relate to the terrestrial carbon cycle and its vital role in the Earth-atmosphere system.

  1. Paleoceanographic Implications of the Terrestrial Carbon-Isotope Record of the Early Toarcian (Jurassic) Oceanic Anoxic Event

    NASA Astrophysics Data System (ADS)

    Hesselbo, S.; Jenkyns, H. C.; Duarte, L. V.

    2005-12-01

    Macrofossil wood in two European sections representing the Toarcian (Early Jurassic) Oceanic Anoxic Event (OAE) have previously been shown to exhibit a large (~ -6 to -7 %) shift in d13C values which has been interpreted as a massive and geologically short-lived perturbation to the global carbon cycle. This interpretation has recently been challenged on the basis of a compilation of carbon-isotope data from belemnites collected from sections in northern Europe that exhibit carbon isotope values that are heavier than expected at the peak of the OAE. Here we present new carbon isotope measurements from wood collected from a marine record of the early Toarcian at Peniche, Portugal, a section currently under consideration as a GSSP for the base of the Toarcian. A large negative excursion (~ -7%) is confirmed for the OAE in these samples. These cannot have been severely impregnated by hydrocarbons of marine origin and the ages are well defined by ammonite biostratigraphy and by Sr-isotope stratigraphy. Carbon-isotope data is also presented for an early diagenetic silica nodule that formed within jet from the Toarcian of the Yorkshire coast, northeast England; values are indistinguishable from those of stratigraphically equivalent jet samples from which solvent extractable hydrocarbons had been removed. Thus, the early Toarcian negative carbon-isotope excursion is confirmed as a phenomenon of the global shallow-ocean, biosphere and atmosphere. It is likely that the anomalously heavy values obtained from belemnites from the OAE interval derive their isotopic signature from localized and possibly seasonal water masses characterized by dissolved inorganic carbon strongly enriched in heavy carbon by very high organic productivity.

  2. The Formation of Haze During the Rise of Oxygen in the Atmosphere of the Early Earth

    NASA Astrophysics Data System (ADS)

    Horst, S. M.; Jellinek, M.; Pierrehumbert, R.; Tolbert, M. A.

    2013-12-01

    Atmospheric aerosols play an important role in determining the radiation budget of an atmosphere and can also provide a wealth of organic material to the surface. Photochemical hazes are abundant in reducing atmospheres, such as the N2/CH4 atmosphere of Titan, but are unlikely to form in oxidizing atmospheres, such as the N2/O2 atmosphere of present day Earth. However, information about haze formation in mildly oxidizing atmospheres is lacking. Understanding haze formation in mildly oxidizing atmospheres is necessary for models that wish to investigate the atmosphere of the Early Earth as O2 first appeared and then increased in abundance. Previous studies of the atmosphere of the Early Earth have focused on haze formation in N2/CO2/CH4 atmospheres. In this work, we experimentally investigate the effect of the addition of O2 on the formation and composition of aerosols. Using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) (see e.g. [1]) we have obtained in situ composition measurements of aerosol particles produced in N2/CO2/CH4/O2 gas mixtures subjected to FUV radiation (deuterium lamp, 115-400 nm) for a range of initial CO2/CH4/O2 mixing ratios. In particular, we studied the effect of O2 ranging from 2 ppm to 2%. The particles were also investigated using a Scanning Mobility Particle Sizer (SMPS), which measures particle size, number density and mass loading. A comparison of the composition of the aerosols will be presented. The effect of variation of O2 mixing ratio on aerosol production, size, and composition will also be discussed. [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326.

  3. Effect of O3 on the atmospheric temperature structure of early Mars

    NASA Astrophysics Data System (ADS)

    von Paris, P.; Selsis, F.; Godolt, M.; Grenfell, J. L.; Rauer, H.; Stracke, B.

    2015-09-01

    Ozone is an important radiative trace gas in the Earth's atmosphere and has also been detected on Venus and Mars. The presence of ozone can significantly influence the thermal structure of an atmosphere due to absorption of stellar UV radiation, and by this e.g. cloud formation. Photochemical studies suggest that ozone can form in carbon dioxide-rich atmospheres. Therefore, we investigate the effect of ozone on the temperature structure of simulated early martian atmospheres. With a 1D radiative-convective model, we calculate temperature-pressure profiles for a 1 bar carbon dioxide atmosphere containing various amounts of ozone. These ozone profiles are fixed, parameterized profiles. We vary the location of the ozone layer maximum and the concentration at this maximum. The maximum is placed at different pressure levels in the upper and middle atmosphere (1-10 mbar). Results suggest that the impact of ozone on surface temperatures is relatively small. However, the planetary albedo significantly decreases at large ozone concentrations. Throughout the middle and upper atmospheres, temperatures increase upon introducing ozone due to strong UV absorption. This heating of the middle atmosphere strongly reduces the zone of carbon dioxide condensation, hence the potential formation of carbon dioxide clouds. For high ozone concentrations, the formation of carbon dioxide clouds is inhibited in the entire atmosphere. In addition, due to the heating of the middle atmosphere, the cold trap is located at increasingly higher pressures when increasing ozone. This leads to wetter stratospheres hence might increase water loss rates on early Mars. However, increased stratospheric H2O would lead to more HOx, which could efficiently destroy ozone by catalytic cycles, essentially self-limiting the increase of ozone. This result emphasizes the need for consistent climate-chemistry calculations to assess the feedback between temperature structure, water content and ozone chemistry. Furthermore, convection is inhibited at high ozone amounts, leading to a stably stratified atmosphere.

  4. Study of the Role of Terrestrial Processes in the Carbon Cycle Based on Measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Piper, Stephen C; Keeling, Ralph F

    2012-01-03

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic ratios 13C/12C, 18O/16O, and 14C/12C. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. Using models of varying complexity, the concentration and isotopic measurements were used to study long-term change in the interhemispheric gradients in CO2 and 13C/12C to assess the magnitude and evolution of the northern terrestrial carbon sink, to study the increase in amplitude of the seasonal cycle of CO2, to use isotopic data to refine constraints on large scale changes in isotopic fractionation which may be related to changes in stomatal conductance, and to motivate improvements in terrestrial carbon cycle models. The original proposal called for a continuation of the new time series of 14C measurements but subsequent descoping to meet budgetary constraints required termination of measurements in 2007.

  5. Terrestrial Carbon-Isotope Records from Early Cretaceous Coastal Deposits (Algarve, Portugal): High-Resolution Chemostratigraphy on an Intrabasinal and Global Scale

    NASA Astrophysics Data System (ADS)

    Heimhofer, U.

    2001-12-01

    The carbon-isotope composition of terrestrial organic matter (OM), obtained from Aptian coastal deposits of the western Algarve basin, Portugal, displays significant small- and large-scale variations throughout the record, which can be related to perturbations of the global carbon-cycle. The dominance of continent-derived plant debris in the bulk OM fraction is confirmed by optical studies, Rock-Eval pyrolysis and by comparison with the δ 13C signature of different types of vascular land-plant particles, including charcoal, lignite, cuticules and leaf fragments. Two terrestrial δ 13CbulkOM records from different study sites within the Algarve basin can be correlated on a high-resolution scale resulting in a significant enhancement of the stratigraphic resolution of these shallow water sections. The global significance of the Portuguese land-plant δ 13C data is demonstrated by comparison with existing terrestrial and marine carbon-isotope records and indicates that variations in the terrestrial δ 13C record are primarily controlled by changes in the carbon-isotopic composition of the mid-Cretaceous atmospheric CO2.

  6. Xenological constraints on the impact erosion of the early Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin J.

    1993-01-01

    This paper considers impact erosion as the agent of the early Martian atmophere escape, by examining xenon-related constraints imposed on the impact erosion. It is found that, if impact erosion of a planetary atmosphere is important, the remnant atmosphere is likely to fall into one of two qualitatively distinct categories: (1) cometary xenon has an unexpected isotopic composition or (2) factors other than impacts, such as outgassing or recycling, are needed. Neither of these categories can readily account for the present Martian atmosphere.

  7. Xenological constraints on the impact erosion of the early Martian atmosphere

    NASA Astrophysics Data System (ADS)

    Zahnle, K. J.

    1993-06-01

    This paper considers impact erosion as the agent of the early Martian atmophere escape, by examining xenon-related constraints imposed on the impact erosion. It is found that, if impact erosion of a planetary atmosphere is important, the remnant atmosphere is likely to fall into one of two qualitatively distinct categories: (1) cometary xenon has an unexpected isotopic composition or (2) factors other than impacts, such as outgassing or recycling, are needed. Neither of these categories can readily account for the present Martian atmosphere.

  8. MODIS-Derived Terrestrial Primary Production

    NASA Astrophysics Data System (ADS)

    Zhao, Maosheng; Running, Steven; Heinsch, Faith Ann; Nemani, Ramakrishna

    Temporal and spatial changes in terrestrial biological productivity have a large impact on humankind because terrestrial ecosystems not only create environments suitable for human habitation, but also provide materials essential for survival, such as food, fiber and fuel. A recent study estimated that consumption of terrestrial net primary production (NPP; a list of all the acronyms is available in the appendix at the end of the chapter) by the human population accounts for about 14-26% of global NPP (Imhoff et al. 2004). Rapid global climate change is induced by increased atmospheric greenhouse gas concentration, especially CO2, which results from human activities such as fossil fuel combustion and deforestation. This directly impacts terrestrial NPP, which continues to change in both space and time (Melillo et al. 1993; Prentice et al. 2001; Nemani et al. 2003), and ultimately impacts the well-being of human society (Milesi et al. 2005). Additionally, substantial evidence show that the oceans and the biosphere, especially terrestrial ecosystems, currently play a major role in reducing the rate of the atmospheric CO2 increase (Prentice et al. 2001; Schimel et al. 2001). NPP is the first step needed to quantify the amount of atmospheric carbon fixed by plants and accumulated as biomass. Continuous and accurate measurements of terrestrial NPP at the global scale are possible using satellite data. Since early 2000, for the first time, the MODIS sensors onboard the Terra and Aqua satellites, have operationally provided scientists with near real-time global terrestrial gross primary production (GPP) and net photosynthesis (PsnNet) data. These data are provided at 1 km spatial resolution and an 8-day interval, and annual NPP covers 109,782,756 km2 of vegetated land. These GPP, PsnNet and NPP products are collectively known as MOD17 and are part of a larger suite of MODIS land products (Justice et al. 2002), one of the core Earth System or Climate Data Records (ESDR or CDR).

  9. An upper limit on Early Mars atmospheric pressure from small ancient craters

    NASA Astrophysics Data System (ADS)

    Kite, E. S.; Williams, J.; Lucas, A.; Aharonson, O.

    2012-12-01

    Planetary atmospheres brake, ablate, and disrupt small asteroids and comets, filtering out small hypervelocity surface impacts and causing fireballs, airblasts, meteors, and meteorites. Hypervelocity craters <1 km diameter on Earth are typically caused by irons (because stones are more likely to break up), and the smallest hypervelocity craters near sea-level on Earth are ~20 m in diameter. 'Zap pits' as small as 30 microns are known from the airless moon, but the other airy worlds show the effects of progressively thicker atmospheres:- the modern Mars atmosphere is marginally capable of removing >90% of the kinetic energy of >240 kg iron impactors; Titan's paucity of small craters is consistent with a model predicting atmospheric filtering of craters smaller than 6-8km; and on Venus, craters below ~20 km diameter are substantially depleted. Changes in atmospheric CO2 concentration are believed to be the single most important control on Mars climate evolution and habitability. Existing data requires an early epoch of massive atmospheric loss to space; suggests that the present-day rate of escape to space is small; and offers only limited evidence for carbonate formation. Existing evidence has not led to convergence of atmosphere-evolution models, which must balance poorly understood fluxes from volcanic degassing, surface weathering, and escape to space. More direct measurements are required in order to determine the history of CO2 concentrations. Wind erosion and tectonics exposes ancient surfaces on Mars, and the size-frequency distribution of impacts on these surfaces has been previously suggested as a proxy time series of Mars atmospheric thickness. We will present a new upper limit on Early Mars atmospheric pressure using the size-frequency distribution of 20-100m diameter ancient craters in Aeolis Dorsa, validated using HiRISE DTMs, in combination with Monte Carlo simulations of the effect of paleo-atmospheres of varying thickness on the crater flux. These craters are interbedded with river deposits, and so the atmospheric state they record corresponds to an era when Mars was substantially wetter than the present, probably >3.7 Ga. An important caveat is that our technique cannot exclude atmospheric collapse-reinflation cycles on timescales much shorter than the sedimentary basin-filling time, so it sets an upper limit on the density of a thick stable paleoatmosphere. We will discuss our results in relation to previous estimates of ancient atmospheric pressure, and place new constraints on models of Early Mars climate.

  10. Coupled Nd-142, Nd-143 and Hf-176 Isotopic Data from 3.6-3.9 Ga Rocks: New Constraints on the Timing of Early Terrestrial Chemical Reservoirs

    NASA Technical Reports Server (NTRS)

    Bennett, Vickie C.; Brandon, alan D.; Hiess, Joe; Nutman, Allen P.

    2007-01-01

    Increasingly precise data from a range of isotopic decay schemes, including now extinct parent isotopes, from samples of the Earth, Mars, Moon and meteorites are rapidly revising our views of early planetary differentiation. Recognising Nd-142 isotopic variations in terrestrial rocks (which can only arise from events occurring during the lifetime of now extinct Sm-146 [t(sub 1/2)=103 myr]) has been an on-going quest starting with Harper and Jacobsen. The significance of Nd-142 variations is that they unequivocally reflect early silicate differentiation processes operating in the first 500 myr of Earth history, the key time period between accretion and the beginning of the rock record. The recent establishment of the existence of Nd-142 variations in ancient Earth materials has opened a new range of questions including, how widespread is the evidence of early differentiation, how do Nd-142 compositions vary with time, rock type and geographic setting, and, combined with other types of isotopic and geochemical data, what can Nd-142 isotopic variations reveal about the timing and mechanisms of early terrestrial differentiation? To explore these questions we are determining high precision Nd-142, Nd-143 and Hf-176 isotopic compositions from the oldest well preserved (3.63- 3.87 Ga), rock suites from the extensive early Archean terranes of southwest Greenland and western Australia.

  11. The observational influence of the North Atlantic SST tripole on the early spring atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Han, Zhe; Luo, Feifei; Wan, Jianghua

    2016-03-01

    This study investigated the forcing of the North Atlantic sea surface temperature (SST) tripole on the North Atlantic Oscillation (NAO)-like circulation in early spring (February-April) in observations. Corresponding to an SST tripole forcing in early spring, the atmospheric circulation is very weak and insignificant. However, further analyses indicate that the observational effect of the SST anomalies on the NAO-like circulation is disturbed by the concomitant sea ice anomalies. With the linear effects of sea ice anomalies removed, there is an equivalent barotropic NAO-like circulation in early spring related to a North Atlantic SST tripole.

  12. The Formation of Haze During the Rise of Oxygen in the Atmosphere of the Early Earth

    NASA Astrophysics Data System (ADS)

    Horst, S. M.; Jellinek, M.; Pierrehumbert, R.; Tolbert, M. A.

    2014-12-01

    also provide a wealth of organic material to the surface. Photochemical hazes are abundant in reducing atmospheres, such as the N2/CH4 atmosphere of Titan, but are unlikely to form in oxidizing atmospheres, such as the N2/O2 atmosphere of present day Earth. However, information about haze formation in mildly oxidizing atmospheres is lacking. Understanding haze formation in mildly oxidizing atmospheres is necessary for models that wish to investigate the atmosphere of the Early Earth as O2 first appeared and then increased in abundance. Previous studies of the atmosphere of the Early Earth have focused on haze formation in N2/CO2/CH4 atmospheres. In this work, we experimentally investigate the effect of the addition of O2 on the formation and composition of aerosols. Using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) (see e.g. [1]) we have obtained in situ composition measurements of aerosol particles produced in N2/CO2/CH4/O2 gas mixtures subjected to FUV radiation (deuterium lamp, 115-400 nm) for a range of initial CO2/CH4/O2 mixing ratios. In particular, we studied the effect of O2 ranging from 2 ppm to 2%. The particles were also investigated using a Scanning Mobility Particle Sizer (SMPS), which measures particle size, number density and mass loading. A comparison of the composition of the aerosols will be presented. The effect of variation of O2 mixing ratio on aerosol production, size, and composition will also be discussed. [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326.

  13. Multiple States in the Vegetation-Atmosphere System during the Early Eocene

    NASA Astrophysics Data System (ADS)

    Port, U.; Claussen, M.

    2014-12-01

    Model simulations suggest that different initial conditions can lead to multiple stable vegetation-atmosphere states in the present-day Sahara. Here, we explore the stability of the vegetation-atmosphere system in the warm, nearly ice-free early Eocene climate. Using the MPI-ESM, we simulate the early Eocene vegetation starting from two different states: Continents are either completely covered by forest or completely barren, devoid of any vegetation. The soil albedo is similar to vegetation albedo. Hence, the albedo effect of vegetation is negligible. Without the albedo effect, the Charney effect which is suggested to cause multiple stable vegetation states in the present-day Sahara is absent. In our simulations, the hydrological effect of vegetation plays the major role. We perform the same simulations with preindustrial conditions to compare the stability of the vegetation-atmosphere system in both climate states. A desert evolves in Central Asia in both early Eocene simulations. This Asian desert is larger when the simulation starts from bare soil instead forest. Bare soil causes a dry climate in Central Asia in the beginning of the simulation. In the dry climate, vegetation does not establish. Forest enhances evaporation relative to bare soil leading to a stronger Asian monsoon and higher precipitation rates. The increased precipitation sustains plant growth and a smaller Asian desert evolves than in the simulation started from bare soil. Moreover, the stronger Asian monsoon affects global climate. Therefore, the two vegetation states in Central Asia accompany two globally different vegetation-atmosphere states. In the preindustrial climate, the Sahara is larger when the initial vegetation is bare soil instead of forest. The same hydrological effect causes the multiple vegetation states the Sahara as in the early Eocene Asian desert. However, the multiple stable vegetation states in the Sahara do not affect the global climate. This result emphasises that the vegetation-atmosphere system is more sensitive to the initial vegetation cover during the early Eocene than today.

  14. Complex Spatiotemporal Responses of Global Terrestrial Primary Production to Climate Change and Increasing Atmospheric CO2 in the 21st Century

    PubMed Central

    Pan, Shufen; Tian, Hanqin; Dangal, Shree R. S.; Zhang, Chi; Yang, Jia; Tao, Bo; Ouyang, Zhiyun; Wang, Xiaoke; Lu, Chaoqun; Ren, Wei; Banger, Kamaljit; Yang, Qichun; Zhang, Bowen; Li, Xia

    2014-01-01

    Quantitative information on the response of global terrestrial net primary production (NPP) to climate change and increasing atmospheric CO2 is essential for climate change adaptation and mitigation in the 21st century. Using a process-based ecosystem model (the Dynamic Land Ecosystem Model, DLEM), we quantified the magnitude and spatiotemporal variations of contemporary (2000s) global NPP, and projected its potential responses to climate and CO2 changes in the 21st century under the Special Report on Emission Scenarios (SRES) A2 and B1 of Intergovernmental Panel on Climate Change (IPCC). We estimated a global terrestrial NPP of 54.6 (52.8–56.4) PgC yr−1 as a result of multiple factors during 2000–2009. Climate change would either reduce global NPP (4.6%) under the A2 scenario or slightly enhance NPP (2.2%) under the B1 scenario during 2010–2099. In response to climate change, global NPP would first increase until surface air temperature increases by 1.5°C (until the 2030s) and then level-off or decline after it increases by more than 1.5°C (after the 2030s). This result supports the Copenhagen Accord Acknowledgement, which states that staying below 2°C may not be sufficient and the need to potentially aim for staying below 1.5°C. The CO2 fertilization effect would result in a 12%–13.9% increase in global NPP during the 21st century. The relative CO2 fertilization effect, i.e. change in NPP on per CO2 (ppm) bases, is projected to first increase quickly then level off in the 2070s and even decline by the end of the 2080s, possibly due to CO2 saturation and nutrient limitation. Terrestrial NPP responses to climate change and elevated atmospheric CO2 largely varied among biomes, with the largest increases in the tundra and boreal needleleaf deciduous forest. Compared to the low emission scenario (B1), the high emission scenario (A2) would lead to larger spatiotemporal variations in NPP, and more dramatic and counteracting impacts from climate and increasing atmospheric CO2. PMID:25401492

  15. Complex spatiotemporal responses of global terrestrial primary production to climate change and increasing atmospheric CO2 in the 21st century.

    PubMed

    Pan, Shufen; Tian, Hanqin; Dangal, Shree R S; Zhang, Chi; Yang, Jia; Tao, Bo; Ouyang, Zhiyun; Wang, Xiaoke; Lu, Chaoqun; Ren, Wei; Banger, Kamaljit; Yang, Qichun; Zhang, Bowen; Li, Xia

    2014-01-01

    Quantitative information on the response of global terrestrial net primary production (NPP) to climate change and increasing atmospheric CO2 is essential for climate change adaptation and mitigation in the 21st century. Using a process-based ecosystem model (the Dynamic Land Ecosystem Model, DLEM), we quantified the magnitude and spatiotemporal variations of contemporary (2000s) global NPP, and projected its potential responses to climate and CO2 changes in the 21st century under the Special Report on Emission Scenarios (SRES) A2 and B1 of Intergovernmental Panel on Climate Change (IPCC). We estimated a global terrestrial NPP of 54.6 (52.8-56.4) PgC yr(-1) as a result of multiple factors during 2000-2009. Climate change would either reduce global NPP (4.6%) under the A2 scenario or slightly enhance NPP (2.2%) under the B1 scenario during 2010-2099. In response to climate change, global NPP would first increase until surface air temperature increases by 1.5 °C (until the 2030s) and then level-off or decline after it increases by more than 1.5 °C (after the 2030s). This result supports the Copenhagen Accord Acknowledgement, which states that staying below 2 °C may not be sufficient and the need to potentially aim for staying below 1.5 °C. The CO2 fertilization effect would result in a 12%-13.9% increase in global NPP during the 21st century. The relative CO2 fertilization effect, i.e. change in NPP on per CO2 (ppm) bases, is projected to first increase quickly then level off in the 2070s and even decline by the end of the 2080s, possibly due to CO2 saturation and nutrient limitation. Terrestrial NPP responses to climate change and elevated atmospheric CO2 largely varied among biomes, with the largest increases in the tundra and boreal needleleaf deciduous forest. Compared to the low emission scenario (B1), the high emission scenario (A2) would lead to larger spatiotemporal variations in NPP, and more dramatic and counteracting impacts from climate and increasing atmospheric CO2. PMID:25401492

  16. Sensitivity of Holocene atmospheric CO2 and the modern carbon budget to early human land use: analyses with a process-based model

    NASA Astrophysics Data System (ADS)

    Stocker, B. D.; Strassmann, K.; Joos, F.

    2011-01-01

    A Dynamic Global Vegetation model coupled to a simplified Earth system model is used to simulate the impact of anthropogenic land cover changes (ALCC) on Holocene atmospheric CO2 and the contemporary carbon cycle. The model results suggest that early agricultural activities cannot explain the mid to late Holocene CO2 rise of 20 ppm measured on ice cores and that proposed upward revisions of Holocene ALCC imply a smaller contemporary terrestrial carbon sink. A set of illustrative scenarios is applied to test the robustness of these conclusions and to address the large discrepancies between published ALCC reconstructions. Simulated changes in atmospheric CO2 due to ALCC are less than 1 ppm before 1000 AD and 30 ppm at 2004 AD when the HYDE 3.1 ALCC reconstruction is prescribed for the past 12 000 years. Cumulative emissions of 69 GtC at 1850 and 233 GtC at 2004 AD are comparable to earlier estimates. CO2 changes due to ALCC exceed the simulated natural interannual variability only after 1000 AD. To consider evidence that land area used per person was higher before than during early industrialisation, agricultural areas from HYDE 3.1 were increased by a factor of two prior to 1700 AD (scenario H2). For the H2 scenario, the contemporary terrestrial carbon sink required to close the atmospheric CO2 budget is reduced by 0.5 GtC yr-1. Simulated CO2 remains small even in scenarios where average land use per person is increased beyond the range of published estimates. Even extreme assumptions for preindustrial land conversion and high per-capita land use do not result in simulated CO2 emissions that are sufficient to explain the magnitude and the timing of the late Holocene CO2 increase.

  17. Early Eocene carbon isotope excursions: Evidence from the terrestrial coal seam in the Fushun Basin, Northeast China

    NASA Astrophysics Data System (ADS)

    Chen, Zuoling; Ding, Zhongli; Tang, Zihua; Wang, Xu; Yang, Shiling

    2014-05-01

    A series of transient global warming events between 56 and 50 Ma are characterized by a pronounced negative carbon isotope excursion (CIE). However, the documents of these hyperthermals, such as Eocene Thermal Maximum 2 and H2 events, have come chiefly from marine sediments, and their expression in terrestrial organic carbon is still poorly constrained. Here we yield a high-resolution carbon isotope record of terrestrial organic material from the Fushun Basin, which displays four prominent CIEs with magnitudes larger than 2.5‰. Based on age constraint and comparisons with deep-sea records, our data provide the first evidence of the four hyperthermals in coal seams and suggest a global significance of these events. Moreover, the difference of CIE magnitudes between marine and terrestrial records shows a significant linear correlation with the marine carbonate CIE, implying that these events are likely attributable to recurring injections of 13C-depleted carbon from submarine methane hydrates and/or permafrost.

  18. Influence of Carbonic Anhydrase Activity in Terrestrial Vegetation on the 18O Content of Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Gillon, Jim; Yakir, Dan

    2001-03-01

    The oxygen-18 (18O) content of atmospheric carbon dioxide (CO2) is an important indicator of CO2 uptake on land. It has generally been assumed that during photosynthesis, oxygen in CO2 reaches isotopic equilibrium with oxygen in 18O-enriched water in leaves. We show, however, large differences in the activity of carbonic anhydrase (which catalyzes CO2 hydration and 18O exchange in leaves) among major plant groups that cause variations in the extent of 18O equilibrium (?eq). A clear distinction in ?eq between C3 trees and shrubs, and C4 grasses makes atmospheric C18OO a potentially sensitive indicator to changes in C3 and C4 productivity. We estimate a global mean ?eq value of ~0.8, which reasonably reconciles inconsistencies between 18O budgets of atmospheric O2 (Dole effect) and CO2.

  19. Habitability of Terrestrial-Mass Planets in the HZ of M Dwarfs. I. H/He-Dominated Atmospheres.

    NASA Astrophysics Data System (ADS)

    Owen, James E.; Mohanty, Subhanjoy

    2016-04-01

    The ubiquity of M dwarfs, combined with the relative ease of detecting terrestrial-mass planets around them, has made them prime targets for finding and characterising planets in the "Habitable Zone" (HZ). However, Kepler finds that terrestrial-mass exoplanets are often born with voluminous H/He envelopes, comprising mass-fractions (Menv/Mcore) ≳ 1%. If these planets retain such envelopes over Gyr timescales, they will not be "habitable" even within the HZ. Given the strong X-ray/UV fluxes of M dwarfs, we study whether sufficient envelope mass can be photoevaporated away for these planets to become habitable. We improve upon previous work by using hydrodynamic models that account for radiative cooling as well as the transition from hydrodynamic to ballistic escape. Adopting a template active M dwarf XUV spectrum, including stellar evolution, and considering both evaporation and thermal evolution, we show that: (1) the mass-loss is (considerably) lower than previous estimates that use an "energy-limited" formalism and ignore the transition to Jeans escape; (2) at the inner edge of the HZ, planets with core mass ≲ 0.9 M⊕ can lose enough H/He to become habitable if their initial envelope mass-fraction is ˜1%; (3) at the outer edge of the HZ, evaporation cannot remove a ˜1% H/He envelope even from cores down to 0.8 M⊕. Thus, if planets form with bulky H/He envelopes, only those with low-mass cores may eventually be habitable. Cores ≳ 1 M⊕, with ≳1% natal H/He envelopes, will not be habitable in the HZ of M dwarfs.

  20. A Simple Approach to Estimating Temporal Changes in Global Vegetation for Use in a Coupled Terrestrial Ecosystem-Atmosphere Model

    NASA Astrophysics Data System (ADS)

    Wang, A.; Price, D. T.; Arora, V.

    2004-05-01

    Human-caused conversion of natural ecosystems to agricultural land is thought to have significant impacts on the global carbon cycle and climate. Hence, capturing such effects in global terrestrial ecosystem models is an important requirement when accounting for land-use change effects in coupled carbon-climate models. In this study, changes in area fractions of 10 Plant Functional Types (PFT) were estimated for the period 1850-2100, from changes in global cropland area obtained from the Ramankutty & Foley dataset (R&F). The Seasonal Land Cover Regions (SLCR) version 2.0 dataset was used to identify present-day (1992) vegetation. Each SLCR class was split into estimated area fractions of the 10 PFTs according to knowledge of natural vegetation and cropland composition. Global land cover in 1850 was estimated from a potential natural vegetation map adjusted for cropland area from R&F, combined with natural vegetation observed in the SLCR. Two methods were used to estimate fractional coverage of PFTs. The Linear Interpolation model assumed that natural vegetation area varies in inverse proportion to cropland area. In contrast, the Rule-based model used simple transition rules to represent how natural PFTs are converted to agriculture (e.g., grassland before forest) and how abandoned cropland reverts to natural vegetation. Estimates of land use change for 1992-2100 were based on the IPCC SRES A2 and B2 development scenarios simulated by the IMAGE model for 1970-2100. Differences in the representation of 1992 vegetation cover between SLCR and IMAGE were resolved using a multiple regression approach. The adjusted data were then used to initialize the two models and forecast changes in distribution of natural vegetation and cropland cover. The simulated changes in PFTs for 1850-2100 will be used to represent land-use change effects in the Canadian Terrestrial Ecosystem Model (CTEM), currently being developed for the Canadian Centre for Climate Modelling and Analysis (CCCma) coupled carbon-climate model.

  1. Sulfur in the early martian atmosphere revisited: Experiments with a 3-D Global Climate Model

    NASA Astrophysics Data System (ADS)

    Kerber, Laura; Forget, François; Wordsworth, Robin

    2015-11-01

    Volcanic SO2 in the martian atmosphere has been invoked as a way to create a sustained or transient greenhouse during early martian history. Many modeling studies have been performed to test the feasibility of this hypothesis, resulting in a range of conclusions, from highly feasible to highly improbable. In this study we perform a wide range of simulations using the 3-D Laboratoire de Météorologie Dynamique Generic Global Climate Model (GCM) in order to place earlier results into context and to explore the sensitivity of model outcomes to parameters such as SO2 mixing ratio, atmospheric H2O content, background atmospheric pressure, and aerosol size, abundance, and composition. We conclude that SO2 is incapable of creating a sustained greenhouse on early Mars, and that even in the absence of aerosols, local and daily temperatures rise above 273 K for only for limited periods with favorable background CO2 pressures. In the presence of even small amounts of aerosols, the surface is dramatically cooled for realistic aerosol sizes. Brief, mildly warm conditions require the co-occurrence of many improbable factors, while cooling is achieved for a wide range of model parameters. Instead of causing warming, sulfur in the martian atmosphere may have caused substantial cooling, leading to the end of clement climate conditions on early Mars.

  2. Loss of Water in Early Earth's Atmosphere and Its Effects on Habitability

    NASA Astrophysics Data System (ADS)

    Airapetian, Vladimir; Glocer, Alex; Khazanov, George

    2015-08-01

    The short wavelength emission from the Sun has a profound impact on the Earth’s atmosphere. High energy photons ionize the atmosphere and produce photoelectrons. This process provides a major contribution to the acceleration of atmospheric ions due to the vertical separation of ions and electrons, and the formation of the resulting ambipolar electric field. Observations and theory suggest that even a relatively small fraction of super-thermal electrons (photoelectrons) produced due to photoionization can drive the ”polar wind” that is responsible for the transport of ionospheric constituents to the Earth’s magnetosphere.The young Sun was a magnetically active star generating powerful radiative output from its chromosphere, transition region and corona which was a few hundred times greater than that observed today. What effects would the photoionization processes due to the X-ray-UV solar flux from early Sun have on the loss of water from the early Earth?We use the Fokker-Plank code coupled with 1D hydrodynamic code to model the effect of intensive short-wavelength (X-rays to UV band) emission from the young Sun (3.8 and 4.4 Ga) on Earth's atmosphere. Our simulations include the photoionization processes of the Earth’s atmosphere forming a population of photoelectrons (E<600 eV), the kinetic effects of their propagation associated and their contribution in ionosphere - magnetosphere energy redistribution. Our coupled simulations show that the ambipolar electric field can drag atmospheric ions of oxygen and hydrogen to the magnetosphere and produce significant mass loss that can affect the loss of water from the early Earth in the first half a billion years. This process became less efficient in the next 0.2-0.3 Ga that could have provided a window of opportunity for origin of life.

  3. Shock-induced CO2 loss from CaCO3: Implications for early planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Lange, M. A.; Ahrens, T. J.

    1984-01-01

    Recovered samples from shock recovery experiments on single crystal calcite were subjected to thermogravimetric analysis to determine the amount of post-shock CO2, the decarbonization interval and the activation energy, for the removal of remaining CO2 in shock-loaded calcite. Comparison of post-shock CO2 with that initially present determines shock-induced CO2 loss as a function of shock pressure. Incipient to complete CO2 loss occurs over a pressure range of approximately 10 to approximately 70 GPa. Optical and scanning electron microscopy reveal structural changes, which are related to the shock-loading. The occurrence of dark, diffuse areas, which can be resolved as highly vesicular areas as observed with a scanning electron microscope are interpreted as representing quenched partial melts, into which shock-released CO2 was injected. The experimental results are used to constrain models of shock-produced, primary CO2 atmospheres on the accreting terrestrial planets.

  4. Effects of elevated atmospheric carbon dioxide on soil carbon in terrestrial ecosystems of the Southeastern U.S.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants depend on carbon dioxide (CO2) as the substrate for photosynthesis; they remove CO2 from the atmosphere and use it for tissue production, respiring a portion back to the air. A portion of the carbon (C) fixed by plants enters the soil via root exudation and as plant litter (both aboveground ...

  5. ROLE OF LEAF SURFACE WATER IN THE BI-DIRECTIONAL AMMONIA EXCHANGE BETWEEN THE ATMOSPHERE AND TERRESTRIAL BIOSPHERE

    EPA Science Inventory

    A field experiment was conducted to study the ammonia exchange between plants and the atmosphere in a soybean field in Duplin County, North Carolina during the summer of 2002. Measurements indicate that the net canopy-scale ammonia exchange is bi-directional and has a significant...

  6. Studies of the airglow, the aurora, the ion and neutral composition, and the chemistry of the terrestrial atmosphere

    NASA Technical Reports Server (NTRS)

    Zipf, E. C., Jr.

    1974-01-01

    Results obtained by rocket-borne optical spectrometry are presented. Composition measurements and auroral studies are reported. The production of N (D-2) atoms by photo-absorption processes, and by electron impact excitation of N2 are discussed along with vibrationally excited CO2(+) ions in planetary atmospheres.

  7. Latitudinal distribution of terrestrial lipid biomarkers and n-alkane compound-specific stable carbon isotope ratios in the atmosphere over the western Pacific and Southern Ocean

    NASA Astrophysics Data System (ADS)

    Bendle, James; Kawamura, Kimitaka; Yamazaki, Koji; Niwai, Takeji

    2007-12-01

    We investigated the latitudinal changes in atmospheric transport of organic matter to the western Pacific and Southern Ocean (27.58°N-64.70°S). Molecular distributions of lipid compound classes (homologous series of C 15 to C 35n-alkanes, C 8 to C 34n-alkanoic acids, C 12 to C 30n-alkanols) and compound-specific stable isotopes (δ 13C of C 29 and C 31n-alkanes) were measured in marine aerosol filter samples collected during a cruise by the R/V Hakuho Maru. The geographical source areas for each sample were estimated from air-mass back-trajectory computations. Concentrations of TC and lipid compound classes were several orders of magnitude lower than observations from urban sites in Asia. A stronger signature of terrestrial higher plant inputs was apparent in three samples collected under conditions of strong terrestrial winds. Unresolved complex mixtures (UCM) showed increasing values in the North Pacific, highlighting the influence of the plume of polluted air exported from East Asia. n-Alkane average chain length (ACL) distribution had two clusters, with samples showing a relation to latitude between 28°N and 47°S (highest ACL values in the tropics), whilst a subset of southern samples had anomalously high ACL values. Compound-specific carbon isotopic analysis of the C 29 (-25.6‰ to -34.5‰) and C 31n-alkanes (-28.3‰ to -37‰) revealed heavier δ 13C values in the northern latitudes with a transition to lighter values in the Southern Ocean. By comparing the isotopic measurements with back-trajectory analysis it was generally possible to discriminate between different source areas. The terrestrial vegetation source for a subset of the southernmost Southern Ocean is enigmatic; the back-trajectories indicate eastern Antarctica as the only intercepted terrestrial source area. These samples may represent a southern hemisphere background of well mixed and very long range transported higher plant organic material.

  8. Evidence for ancient atmospheric xenon in Archean rocks and implications for the early evolution of the atmosphere

    NASA Astrophysics Data System (ADS)

    Pujol, M.; Marty, B.; Burnard, P.; Hofmann, A.

    2012-12-01

    The initial atmospheric xenon isotopic composition has been much debated over the last 4 decades. A Non radiogenic Earth Atmospheric xenon (NEA-Xe) composition has been proposed to be the best estimate of the initial signature ([1]). NEA-Xe consists of modern atmospheric Xe without fission (131-136Xe) or radioactive decay (129Xe) products. However, the isotope composition of such non-radiogenic xenon is very different to that of potential cosmochemical precursors such as solar or meteoritic Xe, as it is mass-fractionated by up to 3-4 % per amu relative to the potential precursors, and it is also elementally depleted relative to other noble gases. Because the Xe isotopic composition of the Archean appears to be intermediate between that of these cosmochemical end-members and that of the modern atmosphere, we argued that isotopic fractionation of atmospheric xenon did not occur early in Earth's history by hydrodynamic escape, as postulated by all other models ([1], [2], [3]), but instead was a continuous, long term process that lasted during at least the Hadean and Archean eons. Taken at face value, the decrease of the Xe isotopic fractionation from 1.6-2.1 % amu-1 3.5 Ga ago ([4]) to 1 % amu-1 3.0 Ga ago (Ar-Ar age in fluid inclusions trapped in quartz from the same Dresser Formation, [5]) could reflect a secular variation of the atmospheric Xe signature. Nevertheless, up until now, all data showing an isotopic mass fractionation have been measured in rocks and fluids from the same formation (Dresser Formation, Western Australia, aged 3.5 Ga), and have yet to be confirmed in rocks from different locations. In order to better constrain xenon isotopic fractionation of the atmosphere through time, we decided to analyze barites from different ages, geological environments and metamorphism grade. We started this study with barite from the Fig Tree Formation (South Africa, aged 3.26 Ga). This barite was sampled in old mines so have negligible modern exposure time. It is well preserved (no apparent metamorphism) and was deposited in a shallow submarine environment ("Finger type" barites) associated with hydrothermal circulation (white smokers). Compared to barite from the Dresser formation, Fig Tree barite had a long ancient exposure time in the subsurface (under shallow water for example) resulting in huge excesses of 131Xe (131Xe/130Xe ratio ~38 compared to 5.213 for the modern atmosphere one) due to 130Ba(n,γ) reactions. Fissiogenic products (132 to 136Xe) are also more present than in barites from the Dresser Formation and are compatible with the age of the Fig Tree formation. Despite corrections for secondary productions that are hard to constrain, the Fig Tree barite still shows an isotopic mass fractionation of about 1% amu-1, consistent with our expected atmospheric fractionation evolution. [1] Pepin R. O. (1991) Icarus 92(1), 2-79. [2] Dauphas N. (2003) Icarus 165, 326-339. [3] Tolstikhin I. and O'Nions R.K. (1994) Chem. Geol. 115, 1-6. [4] Pujol M., Marty B., Burnard P. and Philippot P. (2009) Geochim. Cosmochim. Acta 73, 6834-46. [5] Pujol M., Marty B. and Burgess R. (2011) Earth Planet. Sci. Lett. 308, 298-306

  9. Synthesis of nitrous oxide by lightning in the early anoxic Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Navarro, K. F.; Navarro-Gonzalez, R.; McKay, C. P.

    2013-12-01

    Carbon dioxide (CO2) was the main atmospheric component of the early Earth's atmosphere and exerted a key role in climate by maintaining a hydrosphere during a primitive faint Sun [1]; however, CO2 was eventually removed from the atmosphere by rock weathering and sequestered in the Earth's crust and mantle [1]. Nitric oxide (NO) was fixed by lightning discharges at a rate of 1×1016 molecules J-1 in CO2 (50-80%) rich atmospheres [2]. As the levels of atmospheric CO2 dropped to 20%, the production rate of NO by lightning rapidly decreased to 2×1014 molecules J-1 and then slowly diminished to 1×1014 molecules J-1 at CO2 levels of about 2.5% [2]. In order to maintain the existence of liquid water in the early Earth, it is required to warm up the planet with other greenhouse gases such as methane (CH4) [3]. Here we report an experimental study of the effects of lightning discharges on the nitrogen fixation rate during the evolution of the Earth's early atmosphere from 10 to 0.8 percent of carbon dioxide with methane concentrations from 0 to 1,000 ppm in molecular nitrogen. Lightning was simulated in the laboratory by a plasma generated with a pulsed Nd-YAG laser [2]. Our results show that the production of NO by lightning is independent of the presence of methane but drops from 3×1014 molecules J-1 in 10% CO2 to 5×1013 molecules J-1 in 1% CO2. Surprisingly, nitrous oxide (N2O) is also produced at a rate of 4×1013 molecules J-1 independent of the levels of CH4 and CO2. N2O is produced by lightning in the contemporaneous oxygenated Earth's atmosphere at a comparable rate of (0.4-1.5)×1013 molecules J-1 [4, 5], but was not detected in nitrogen-carbon dioxide mixtures in the absence of oxygen [6]. The only previously reported abiotic synthesis of N2O was by corona discharges in rich CO2 atmospheres (20-80%) with a production rate of 8×1012 molecules J-1 [6]; however at lower CO2 (<20%) levels, N2O is no longer produced. Therefore, lightning in the early Earth's atmosphere was the main source of N2O in nitrogen dominated atmospheres. N2O is not known to have played a role in abiotic synthesis. It is not incorporated by microorganisms, and hence may not have had a role in the supply of reactive nitrogen to the biosphere. However, it is a powerful greenhouse gas and may have had a role in warming up the early Earth's atmosphere [7]. Lightning activity is enhanced in a warmer climate [8] and so the production of N2O by lightning may have had a positive feedback in increasing lightning activity resulting in more N2O production. N2O is also produced by microbial activity and has been suggested as a potential biosignature in the atmospheres of extrasolar planets [9]. Here we show that lightning can interfere with the remote detection of life using N2O as a biosignature. [1] Kasting, J.F.: 1993, Science 259, 920; [2] Navarro-González, R., et al.: 2001, Nature 412, 61; [3] Tian, F., et al.: 2011, Earth Planet. Sci. Lett. 308, 417; [4] Levine, J.S. et al.: 1979, Geophys. Res. Lett. 6, 557; [5] [5] Hill, R.D. et al.: 1984, J. Geophys. Res. 89, 1411; [6] Nna Mvondo, D. et al.,: 2005, Origins Life Evol. Biosph. 35, 401; [7] Roberson, A.L. et al., Geobiology 9, 313; [8] Williams, E.R.: 2004, Atmos. Res. 76, 272; and [9] Rauer, H.S. et al., Astron. Astrophys. 529, A8.

  10. The solar terrestrial observatory

    NASA Technical Reports Server (NTRS)

    Chappell, C. R.

    1978-01-01

    The larger system of the earth environment is controlled externally by electromagnetic and particle energy from the sun. Recent studies have shown that the sun is a variable star with changes in its radiation which produce significant effects in the earth's climate and weather. The study of the solar-terrestrial system requires simultaneous, long-duration observations of the different elements or 'links' in the solar-terrestrial chain. Many investigations must be conducted in space from a vantage point above the earth's atmosphere where all of the sun's emissions can be observed free from atmospheric distortion, where the magnetospheric particles and fields can be measured directly, and where the atmosphere can be observed on a global scale. The extension of the Shuttle on-orbit capability in connection with the development of the power module will offer an important near-term step in an evolutionary process leading toward a permanent manned Solar Terrestrial Observatory capability in low-earth orbit. Attention is given to the required solar-terrestrial measurements, the operation of the Solar Terrestrial Observatory, and an evolutionary approach to the Solar Terrestrial Observatory.

  11. The young sun and the atmosphere and photochemistry of the early earth

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Levine, J. S.; Augustsson, T. R.; Imhoff, C. L.; Giampapa, M. S.

    1983-01-01

    The origin and evolution of the earth's early atmosphere depend crucially on the dissipation time of the primitive solar nebula (SN). Using different theories of turbulence, the dissipation time of an SN of 0.1 solar mass is estimated as 2.5-8.3 Myr. Because accretion times are usually much longer, it is concluded that most planetary accretion must have occurred in a gas-free environment. Using new IUE data, a wavelength-dependent UV flux is constructed for the young sun which is then used to study the photochemistry and concentrations of O, O2, O3, OH, H, HCO and formaldehyde H2CO in the earth's early prebiological atmosphere.

  12. Drip Magmatism: Intra-Plate Volcanism and Its Importance to the Early Earth and Other Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Elkins-Tanton, L. T.

    2014-12-01

    In the present neither Mars nor Venus has Earth-like plate tectonics, though both are likely still volcanically active. Volcanism on Mars and Venus most resembles intra-plate volcanism on Earth, where magmatism occurs through intact lithospheric plates, away from plate boundaries. On Earth intra-plate magmatism has long been proposed to be the result of lithospheric thinning through delamination or ductile dripping. Exactly how these processes create volcanism, however, has remained obscure; particularly in the case of ductile dripping, which does not produce significant topography in the lithosphere-asthenosphere boundary. Though its fall may not trigger significant asthenospheric upwelling, the sinking drip itself will heat conductively as it enters the asthenosphere, and may itself melt, depending upon its solidus temperature and the temperature of the asthenosphere. We refer to this as "drip magmatism," following the hypothesis of Elkins-Tanton (2007). This model produces testable predictions for the resulting magmatic compositions. Drip magmatism was tested by Ducea (2013) for the Altiplano Plateau in the central Andes, by Holbig and Grove (2008) for magmas from Tibet, by Elkins-Tanton (2014) for the Sierra Nevada, and by Furman et al. (2014) for the central African rift; geochemistry in all these localities confirm drip magmatism. Drip magmatism provides a quantifiable mechanism for slow but regular recycling of volatiles into a planetary atmosphere. Further, it could be driven primarily by carbon, or halogens, or other incompatible and volatile elements, in addition to water. Thus, volcanism on one-plate planets, or during a putative "hot" or "slow" tectonics phase on the early Earth, may provide sufficient volatile recycling for habitability.

  13. Martian supergene enrichment in Shalbatana Valley: Implications for Mars Early atmosphere

    NASA Astrophysics Data System (ADS)

    Popa, Ciprian; Carrozzo, Giacomo; DiAchille, Gaetano; Silvestro, Simone; Espostio, Francesca; Mennella, Vito

    2015-04-01

    The present work focuses on the detailed description of the first ever-identified supergene enrichment zone on Mars. The mineral paragenesis present at the site sets constrains on the characteristics of early Martian atmosphere. A chrysocolla/malachite bearing unit in the largest of Shalbatana Valley paleolacustrine sediment accumulation constitutes the proof for this process. The water permanence at the formation time is the main implication of this finding. Furthermore, the potential biogenic involvement at the mineralization stage adds scientific importance to the site. The latter implication could set the site as a high priority choice for future Martian in-situ robotic roving/sample-return missions. The relative age of the area (˜3.7 Ba) adds weight to this finding for purposes of planetary atmosphere evolution comparison. No Earth supergene deposit has survived that long, making this site extremely important to address the problem of the oxidative conditions of the primordial Earth and Mars atmospheres.

  14. Methane fluxes between terrestrial ecosystems and the atmosphere at northern high latitudes during the past century: A retrospective analysis with a process-based biogeochemistry model

    USGS Publications Warehouse

    Zhuang, Q.; Melillo, J.M.; Kicklighter, D.W.; Prinn, R.G.; McGuire, A.D.; Steudler, P.A.; Felzer, B.S.; Hu, S.

    2004-01-01

    We develop and use a new version of the Terrestrial Ecosystem Model (TEM) to study how rates of methane (CH4) emissions and consumption in high-latitude soils of the Northern Hemisphere have changed over the past century in response to observed changes in the region's climate. We estimate that the net emissions of CH4 (emissions minus consumption) from these soils have increased by an average 0.08 Tg CH4 yr-1 during the twentieth century. Our estimate of the annual net emission rate at the end of the century for the region is 51 Tg CH4 yr-1. Russia, Canada, and Alaska are the major CH4 regional sources to the atmosphere, responsible for 64%, 11%, and 7% of these net emissions, respectively. Our simulations indicate that large interannual variability in net CH4 emissions occurred over the last century. Our analyses of the responses of net CH4 emissions to the past climate change suggest that future global warming will increase net CH4 emissions from the Pan-Arctic region. The higher net CH4 emissions may increase atmospheric CH 4 concentrations to provide a major positive feedback to the climate system. Copyright 2004 by the American Geophysical Union.

  15. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene

    NASA Astrophysics Data System (ADS)

    Levy, Richard; Harwood, David; Florindo, Fabio; Sangiorgi, Francesca; Tripati, Robert; von Eynatten, Hilmar; Gasson, Edward; Kuhn, Gerhard; Tripati, Aradhna; DeConto, Robert; Fielding, Christopher; Field, Brad; Golledge, Nicholas; McKay, Robert; Naish, Timothy; Olney, Matthew; Pollard, David; Schouten, Stefan; Talarico, Franco; Warny, Sophie; Willmott, Veronica; Acton, Gary; Panter, Kurt; Paulsen, Timothy; Taviani, Marco; SMS Science Team; Acton, Gary; Askin, Rosemary; Atkins, Clifford; Bassett, Kari; Beu, Alan; Blackstone, Brian; Browne, Gregory; Ceregato, Alessandro; Cody, Rosemary; Cornamusini, Gianluca; Corrado, Sveva; DeConto, Robert; Del Carlo, Paola; Di Vincenzo, Gianfranco; Dunbar, Gavin; Falk, Candice; Field, Brad; Fielding, Christopher; Florindo, Fabio; Frank, Tracy; Giorgetti, Giovanna; Grelle, Thomas; Gui, Zi; Handwerger, David; Hannah, Michael; Harwood, David M.; Hauptvogel, Dan; Hayden, Travis; Henrys, Stuart; Hoffmann, Stefan; Iacoviello, Francesco; Ishman, Scott; Jarrard, Richard; Johnson, Katherine; Jovane, Luigi; Judge, Shelley; Kominz, Michelle; Konfirst, Matthew; Krissek, Lawrence; Kuhn, Gerhard; Lacy, Laura; Levy, Richard; Maffioli, Paola; Magens, Diana; Marcano, Maria C.; Millan, Cristina; Mohr, Barbara; Montone, Paola; Mukasa, Samuel; Naish, Timothy; Niessen, Frank; Ohneiser, Christian; Olney, Mathew; Panter, Kurt; Passchier, Sandra; Patterson, Molly; Paulsen, Timothy; Pekar, Stephen; Pierdominici, Simona; Pollard, David; Raine, Ian; Reed, Joshua; Reichelt, Lucia; Riesselman, Christina; Rocchi, Sergio; Sagnotti, Leonardo; Sandroni, Sonia; Sangiorgi, Francesca; Schmitt, Douglas; Speece, Marvin; Storey, Bryan; Strada, Eleonora; Talarico, Franco; Taviani, Marco; Tuzzi, Eva; Verosub, Kenneth; von Eynatten, Hilmar; Warny, Sophie; Wilson, Gary; Wilson, Terry; Wonik, Thomas; Zattin, Massimiliano

    2016-03-01

    Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (˜280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (˜500 ppm) atmospheric CO2. These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene.

  16. Atmospheric 14C variations derived from tree rings during the early Younger Dryas

    NASA Astrophysics Data System (ADS)

    Hua, Quan; Barbetti, Mike; Fink, David; Kaiser, Klaus Felix; Friedrich, Michael; Kromer, Bernd; Levchenko, Vladimir A.; Zoppi, Ugo; Smith, Andrew M.; Bertuch, Fiona

    2009-12-01

    Atmospheric radiocarbon variations over the Younger Dryas interval, from ˜13,000 to 11,600 cal yr BP, are of immense scientific interest because they reveal crucial information about the linkages between climate, ocean circulation and the carbon cycle. However, no direct and reliable atmospheric 14C records based on tree rings for the entire Younger Dryas have been available. In this paper, we present (1) high-precision 14C measurements on the extension of absolute tree-ring chronology from 12,400 to 12,560 cal yr BP and (2) high-precision, high-resolution atmospheric 14C record derived from a 617-yr-long tree-ring chronology of Huon pine from Tasmania, Australia, spanning the early Younger Dryas. The new tree-ring 14C records bridge the current gap in European tree-ring radiocarbon chronologies during the early Younger Dryas, linking the floating Lateglacial Pine record to the absolute tree-ring timescale. A continuous and reliable atmospheric 14C record for the past 14,000 cal yr BP including the Younger Dryas is now available. The new records indicate that the abrupt rise in atmospheric Δ 14C associated with the Younger Dryas onset occurs at ˜12,760 cal yr BP, ˜240 yrs later than that recorded in Cariaco varves, with a smaller magnitude of ˜40‰ followed by several centennial Δ 14C variations of 20-25‰. Comparing the tree-ring Δ 14C to marine-derived Δ 14C and modelled Δ 14C based on ice-core 10Be fluxes, we conclude that changes in ocean circulation were mainly responsible for the Younger Dryas onset, while a combination of changes in ocean circulation and 14C production rate were responsible for atmospheric Δ 14C variations for the remainder of the Younger Dryas.

  17. A process-level evaluation of the spatiotemporal variability of CO2 fluxes predicted by terrestrial biosphere models using atmospheric data

    NASA Astrophysics Data System (ADS)

    Fang, Y.; Michalak, A. M.; Shiga, Y. P.; Yadav, V.

    2013-12-01

    Terrestrial biosphere models (TBMs) are used to extrapolate local observations and process-level understanding of land-atmosphere carbon exchange to larger regions, and can serve as a predictive tool for examining carbon-climate interactions and global change. Understanding and improving the performance of TBMs is thus crucial to the carbon cycle research community. In this work, we evaluate the spatiotemporal patterns of net ecosystem exchange (NEE) simulated by TBMs using atmospheric CO2 observations and a Geostatistical Inverse Modeling (GIM) framework. The evaluation methodology is based on the ability (or inability) of the spatiotemporal patterns in NEE estimates to explain the variability observed in atmospheric CO2 distribution. More simply, we examine whether the spatiotemporal patterns of NEE simulated by TBMs (including CASA-GFED, ORCHIDEE, VEGAS2 and SiB3) are consistent with the variations observed in the atmosphere. A similar GIM methodology is also applied using environmental variables (such as water availability, temperature, radiation, etc.) rather than TBMs, to explore the environmental processes associated with the variability of NEE, and determine which processes are associated with good/poor performance in TBMs. We find that NEE simulated by TBMs is consistent with that seen by atmospheric measurements more often during growing season months (Apr-Sept) than during the non-growing season. Over Temperate Broadleaf and Mixed Forests, Temperate Coniferous Forests and Temperate Grasslands, Savannas and Shrublands, atmospheric measurements are sufficiently sensitive to NEE fluxes to constrain the evaluation of model performance during the majority of the year (about 7-8 months in a year, mostly in growing season). For these regions and months, at least one of the TBMs is found to be able to reproduce the observed variability, but the most representative TBM varies by region and month. For the remaining months, none of the TBMs are able to reproduce the observed variability, whereas a linear combination of environmental variables is able to do so. By further comparing environmental processes associated with the spatiotemporal variability of NEE from the observations and from each TBM, we find that TBMs perform well when radiation-related processes are dominant; however, TBMs perform less well when water-availability (and temperature) are more important. It thus appears that the representation of water availability and its impact on fluxes within TBMs are areas of opportunity for improving TBM predictions, for example, in the seasonal transition. Further exploration of the processes associated with water availability in state-of-the-art TBMs, such as soil respiration, could therefore lead to improvements in their ability to represent the spatiotemporal variability of fluxes during the dormant season and their ability to represent phenology and carbon exchange during transition months.

  18. Modeled responses of terrestrial ecosystems to elevated atmospheric CO2: A comparison of simulations by the biogeochemistry models of the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP)

    USGS Publications Warehouse

    Pan, Y.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Pitelka, L.F.; Hibbard, K.; Pierce, L.L.; Running, S.W.; Ojima, D.S.; Parton, W.J.; Schimel, D.S.; Borchers, J.; Neilson, R.; Fisher, H.H.; Kittel, T.G.F.; Rossenbloom, N.A.; Fox, S.; Haxeltine, A.; Prentice, I.C.; Sitch, S.; Janetos, A.; McKeown, R.; Nemani, R.; Painter, T.; Rizzo, B.; Smith, T.; Woodward, F.I.

    1998-01-01

    Although there is a great deal of information concerning responses to increases in atmospheric CO2 at the tissue and plant levels, there are substantially fewer studies that have investigated ecosystem-level responses in the context of integrated carbon, water, and nutrient cycles. Because our understanding of ecosystem responses to elevated CO2 is incomplete, modeling is a tool that can be used to investigate the role of plant and soil interactions in the response of terrestrial ecosystems to elevated CO2. In this study, we analyze the responses of net primary production (NPP) to doubled CO2 from 355 to 710 ppmv among three biogeochemistry models in the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP): BIOME-BGC (BioGeochemical Cycles), Century, and the Terrestrial Ecosystem Model (TEM). For the conterminous United States, doubled atmospheric CO2 causes NPP to increase by 5% in Century, 8% in TEM, and 11% in BIOME-BGC. Multiple regression analyses between the NPP response to doubled CO2 and the mean annual temperature and annual precipitation of biomes or grid cells indicate that there are negative relationships between precipitation and the response of NPP to doubled CO2 for all three models. In contrast, there are different relationships between temperature and the response of NPP to doubled CO2 for the three models: there is a negative relationship in the responses of BIOME-BGC, no relationship in the responses of Century, and a positive relationship in the responses of TEM. In BIOME-BGC, the NPP response to doubled CO2 is controlled by the change in transpiration associated with reduced leaf conductance to water vapor. This change affects soil water, then leaf area development and, finally, NPP. In Century, the response of NPP to doubled CO2 is controlled by changes in decomposition rates associated with increased soil moisture that results from reduced evapotranspiration. This change affects nitrogen availability for plants, which influences NPP. In TEM, the NPP response to doubled CO2 is controlled by increased carboxylation which is modified by canopy conductance and the degree to which nitrogen constraints cause down-regulation of photosynthesis. The implementation of these different mechanisms has consequences for the spatial pattern of NPP responses, and represents, in part, conceptual uncertainty about controls over NPP responses. Progress in reducing these uncertainties requires research focused at the ecosystem level to understand how interactions between the carbon, nitrogen, and water cycles influence the response of NPP to elevated atmospheric CO2.

  19. Simulation of the capabilities of an orbiter for monitoring the entry of interplanetary matter into the terrestrial atmosphere

    NASA Astrophysics Data System (ADS)

    Bouquet, Alexis; Baratoux, David; Vaubaillon, Jérémie; Gritsevich, Maria I.; Mimoun, David; Mousis, Olivier; Bouley, Sylvain

    2014-11-01

    In comparison with existing ground-based camera networks for meteors monitoring, a space-based optical system would escape dependency on weather and atmospheric conditions and would offer a wide spatial coverage and an unrestricted and extinction-free spectral domain. The potential rates of meteor detections by such systems are evaluated in this paper as a function of observations parameters (optical system capabilities, orbital parameters) and considering a reasonable range of meteoroids properties (e.g., mass, velocity, composition) determining their luminosity. A numerical tool called SWARMS (Simulator for Wide Area Recording of Meteors from Space) has been developed. SWARMS is also intended to be used in an operational phase to facilitate the comparison of observations with up-do-date constraints on the flux and characteristics of the interplanetary matter entering our planet's atmosphere. The laws governing the conversion of a fraction of the meteor kinetic energy into radiation during atmospheric entry have been revisited and evaluated based on an analysis of previously published meteor trajectories. Rates of detection were simulated for two different systems: the SPOSH (Smart Panoramic Optical Sensor Head) camera optimized for the observation of transient luminous events, and the JEM-EUSO (Japanese Experiment Module-Extreme Universe Space Observatory) experiment on the ISS (International Space Station). We conclude that up to 6 events per hour in the case of SPOSH, and up to 0.67 events in the case of JEM-EUSO may be detected. The optimal orbit for achieving such rates of detections depends on the mass index of the meteoroid populations. The determination of this parameter appears therefore critical before an optimal orbiting system might be designed for meteors monitoring.

  20. Turbulent atmospheric plumes above line sources with an application to volcanic fissure eruptions on the terrestrial planets

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

    The theory of turbulent plumes maintained above steady line sources of buoyancy is worked out in detail within the limitations of Taylor's entrainment assumption. It is applied to the structure of a pure plume injected into a stably stratified atmosphere. Volcanic basalt eruptions that develop from long, narrow vents create line source plumes, which rise well above the magmatic fire fountains playing near the ground level. The eruption of Laki in 1783 may provide an example of this style of eruption. Flood basalts are more ancient examples. Evidence of enormous fissure eruptions that occurred in the past on Mars and Venus also exists. Owing to the different properties of the atmospheres on these two planets from those on the earth, heights of line source plumes are expected to vary in the ratios 1:6:0.6 (earth:Mars:Venus). It is very unlikely that the observed increase of sulfur dioxide above the Venusian cloud deck in 1978 could have been due to a line source volcanic eruption, even if it had been a flood basalt eruption.

  1. Ideas and perspectives: on the emission of amines from terrestrial vegetation in the context of new atmospheric particle formation

    NASA Astrophysics Data System (ADS)

    Sintermann, J.; Neftel, A.

    2015-06-01

    In this article we summarise recent science which shows how airborne amines, specifically methylamines (MAs), play a key role in new atmospheric particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NPF events observed in remote regions. This leads us to the presentation of existing knowledge focussing on natural vegetation-related MA sources. High MA contents as well as emissions by plants was already described in the 19th century. Strong MA emissions predominantly occur during flowering as part of a pollination strategy. The behaviour is species-specific, but examples of such species are common and widespread. In addition, vegetative plant tissue exhibiting high amounts of MAs might potentially lead to significant emissions. The decomposition of organic material constitutes another, potentially ubiquitous, source of airborne MAs. These mechanisms would provide sources, which could be crucial for the amine's role in NPF, especially in remote regions. Knowledge about vegetation-related amine emissions is, however, very limited, and thus it is also an open question how global change and the intensified cycling of reactive nitrogen over the last 200 years have altered amine emissions from vegetation with a corresponding effect on NPF.

  2. Ideas and Perspectives: On the emission of amines from terrestrial vegetation in the context of atmospheric new particle formation

    NASA Astrophysics Data System (ADS)

    Sintermann, J.; Neftel, A.

    2015-02-01

    In this article we summarise recent science, which shows how airborne amines, specifically methylamines (MAs), play a key role in atmospheric new particle formation (NPF) by stabilising small molecule clusters. Agricultural emissions are assumed to constitute the most important MA source, but given the short atmospheric residence time of MAs, they can hardly have a direct impact on NFP events observed in remote regions. This leads us to the presentation of existing knowledge focussing on natural vegetation-related MA sources. High MA contents as well as emissions by plants have already been described in the 19th century. Strong MA emissions predominantly occur during flowering as part of a pollination strategy. The behaviour is species specific, but examples of such species are common and widespread. In addition, vegetative plant tissue exhibiting high amounts of MAs might potentially lead to significant emissions, and the decomposition of organic material could constitute another source for airborne MAs. These mechanisms would provide sources, which could be crucial for the amine's role in NPF, especially in remote regions. Knowledge about vegetation-related amine emissions is, however, very limited and thus it is also an open question how Global Change and the intensified cycling of reactive nitrogen over the last 200 years have altered amine emissions from vegetation with a corresponding effect on NPF.

  3. Atmosphere and water loss from early Mars under extreme solar wind and extreme ultraviolet conditions.

    PubMed

    Terada, Naoki; Kulikov, Yuri N; Lammer, Helmut; Lichtenegger, Herbert I M; Tanaka, Takashi; Shinagawa, Hiroyuki; Zhang, Tielong

    2009-01-01

    The upper limits of the ion pickup and cold ion outflow loss rates from the early martian atmosphere shortly after the Sun arrived at the Zero-Age-Main-Sequence (ZAMS) were investigated. We applied a comprehensive 3-D multi-species magnetohydrodynamic (MHD) model to an early martian CO(2)-rich atmosphere, which was assumed to have been exposed to a solar XUV [X-ray and extreme ultraviolet (EUV)] flux that was 100 times higher than today and a solar wind that was about 300 times denser. We also assumed the late onset of a planetary magnetic dynamo, so that Mars had no strong intrinsic magnetic field at that early period. We found that, due to such extreme solar wind-atmosphere interaction, a strong magnetic field of about approximately 4000 nT was induced in the entire dayside ionosphere, which could efficiently protect the upper atmosphere from sputtering loss. A planetary obstacle ( approximately ionopause) was formed at an altitude of about 1000 km above the surface due to the drag force and the mass loading by newly created ions in the highly extended upper atmosphere. We obtained an O(+) loss rate by the ion pickup process, which takes place above the ionopause, of about 1.5 x 10(28) ions/s during the first < or =150 million years, which is about 10(4) times greater than today and corresponds to a water loss equivalent to a global martian ocean with a depth of approximately 8 m. Consequently, even if the magnetic protection due to the expected early martian magnetic dynamo is neglected, ion pickup and sputtering were most likely not the dominant loss processes for the planet's initial atmosphere and water inventory. However, it appears that the cold ion outflow into the martian tail, due to the transfer of momentum from the solar wind to the ionospheric plasma, could have removed a global ocean with a depth of 10-70 m during the first < or =150 million years after the Sun arrived at the ZAMS. PMID:19216683

  4. Spectral Characteristic of Tholin Produced from Possible Early Earth Atmospheres and its Role in Antigreenhouse Effect on Early Earth

    NASA Technical Reports Server (NTRS)

    Khare, B. N.; Imanaka, H.; Wilhite, P.; McKay, C.; Bakes, E.; Cruikshank, D. P.; Arakawa, E. T.

    2003-01-01

    We have produced organic material simulating a methane photochemical haze in a CO2- rich atmosphere of the early Earth by irradiating gas mixtures in an inductively coupled cold plasma chamber with pressure approx. 0.25 mbar at 100 W total power. The flow rate was 24 cm3 min. We added progressively higher levels of CH, by combining gas mixtures of N2/CH4 (9/1) and N2/CO2 (9/1) to change the ratio of CH4/CO2. Tholin was accumulated for 5 hours in each experiment; the onset of tholin formation is in the range CH4/CO2 = 0.5 to 1. As the mixing ratio of CH, is increased, the production rate of the brownish tholin film increases. IR spectra showed the C-H and N-H bands similar to that of Titan tholin and closely resemble Titan tholin made at 0.13 mbar pressure. A decrease in the CH bonds on decreasing CH4/CO2 is noted. Ether bands (-(2-O-C) were tentatively detected, but no detectable carbonyl (C=O) band was found. The absorption in the UV region for the early Earth tholin is found to be substantially greater than the Titan tholin. Quantitative values of the optical constants of early Earth tholin are currently being measured.

  5. Isotopic and anatomical evidence of an herbivorous diet in the Early Tertiary giant bird Gastornis. Implications for the structure of Paleocene terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Angst, D.; Lécuyer, C.; Amiot, R.; Buffetaut, E.; Fourel, F.; Martineau, F.; Legendre, S.; Abourachid, A.; Herrel, A.

    2014-04-01

    The mode of life of the early Tertiary giant bird Gastornis has long been a matter of controversy. Although it has often been reconstructed as an apex predator feeding on small mammals, according to other interpretations, it was in fact a large herbivore. To determine the diet of this bird, we analyze here the carbon isotope composition of the bone apatite from Gastornis and contemporaneous herbivorous mammals. Based on 13C-enrichment measured between carbonate and diet of carnivorous and herbivorous modern birds, the carbonate δ13C values of Gastornis bone remains, recovered from four Paleocene and Eocene French localities, indicate that this bird fed on plants. This is confirmed by a morphofunctional study showing that the reconstructed jaw musculature of Gastornis was similar to that of living herbivorous birds and unlike that of carnivorous forms. The herbivorous Gastornis was the largest terrestrial tetrapod in the Paleocene biota of Europe, unlike the situation in North America and Asia, where Gastornis is first recorded in the early Eocene, and the largest Paleocene animals were herbivorous mammals. The structure of the Paleocene terrestrial ecosystems of Europe may have been similar to that of some large islands, notably Madagascar, prior to the arrival of humans.

  6. Isotopic and anatomical evidence of an herbivorous diet in the Early Tertiary giant bird Gastornis. implications for the structure of Paleocene terrestrial ecosystems.

    PubMed

    Angst, D; Lécuyer, C; Amiot, R; Buffetaut, E; Fourel, F; Martineau, F; Legendre, S; Abourachid, A; Herrel, A

    2014-04-01

    The mode of life of the early Tertiary giant bird Gastornis has long been a matter of controversy. Although it has often been reconstructed as an apex predator feeding on small mammals, according to other interpretations, it was in fact a large herbivore. To determine the diet of this bird, we analyze here the carbon isotope composition of the bone apatite from Gastornis and contemporaneous herbivorous mammals. Based on (13)C-enrichment measured between carbonate and diet of carnivorous and herbivorous modern birds, the carbonate δ(13)C values of Gastornis bone remains, recovered from four Paleocene and Eocene French localities, indicate that this bird fed on plants. This is confirmed by a morphofunctional study showing that the reconstructed jaw musculature of Gastornis was similar to that of living herbivorous birds and unlike that of carnivorous forms. The herbivorous Gastornis was the largest terrestrial tetrapod in the Paleocene biota of Europe, unlike the situation in North America and Asia, where Gastornis is first recorded in the early Eocene, and the largest Paleocene animals were herbivorous mammals. The structure of the Paleocene terrestrial ecosystems of Europe may have been similar to that of some large islands, notably Madagascar, prior to the arrival of humans. PMID:24563098

  7. Radionuclides in the terrestrial ecosystem near a Canadian uranium mill -- Part 3: Atmospheric deposition rates (pilot test)

    SciTech Connect

    Thomas, P.A.

    2000-06-01

    Atmospheric deposition rates of uranium series radionuclides were directly measured at three sites near the operating Key Lake uranium mill in northern Saskatchewan. Sites impacted by windblown tailings and mill dusts had elevated rates of uranium deposition near the mill and elevated {sup 226}Ra deposition near the tailings compared to a control site. Rainwater collectors, dust jars, and passive vinyl collectors previously used at the Ranger Mine in Australia were pilot-tested. Adhesive vinyl surfaces (1 m{sup 2}) were oriented horizontally, vertically, and facing the ground as a means of measuring gravitational settling, wind impaction, and soil resuspension, respectively. Although the adhesive glue on the vinyls proved difficult to digest, relative differences in deposition mode were found among radionuclides and among sites. Dry deposition was a more important transport mechanism for uranium, {sup 226}Ra, and {sup 210}Pb than rainfall, while more {sup 210}Po was deposited with rainfall.

  8. Investigating CO2 Reservoirs at Gale Crater and Evidence for a Dense Early Atmosphere

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Archer, P. D.; Heil, E.; Eigenbrode, J.; McAdam, A.; Sutter, B.; Franz, H.; Navarro-Gonzalez, R.; Ming, D.; Mahaffy, P. R.; Martin-Torres, F. J.; Zorzano, M.

    2015-01-01

    One of the most compelling features of the Gale landing site is its age. Based on crater counts, the formation of Gale crater is dated to be near the beginning of the Hesperian near the pivotal Hesperian/Noachian transition. This is a time period on Mars that is linked to increased fluvial activity through valley network formation and also marks a transition from higher erosion rates/clay mineral formation to lower erosion rates with mineralogies dominated by sulfate minerals. Results from the Curiosity mission have shown extensive evidence for fluvial activity within the crater suggesting that sediments on the floor of the crater and even sediments making up Mt. Sharp itself were the result of longstanding activity of liquid water. Warm/wet conditions on early Mars are likely due to a thicker atmosphere and increased abundance of greenhouse gases including the main component of the atmosphere, CO2. Carbon dioxide is minor component of the Earth's atmosphere yet plays a major role in surface water chemistry, weathering, and formation of secondary minerals. An ancient martian atmosphere was likely dominated by CO2 and any waters in equilibrium with this atmosphere would have different chemical characteristics. Studies have noted that high partial pressures of CO2 would result in increased carbonic acid formation and lowering of the pH so that carbonate minerals are not stable. However, if there were a dense CO2 atmosphere present at the Hesperian/Noachian transition, it would have to be stored in a carbon reservoir on the surface or lost to space. The Mt. Sharp sediments are potentially one of the best places on Mars to investigate these CO2 reservoirs as they are proposed to have formed in the early Hesperian, from an alkaline lake, and record the transition to an aeolian dominated regime near the top of the sequence. The total amount of CO2 in the Gale crater soils and sediments is significant but lower than expected if a thick atmosphere was present at the Hesperian/Noachian boundary. Likewise, the absence of carbonates suggests that CO2- weathering processes similar to those present on Earth were not dominant. Instead it is possible that more exotic CO2 deposition has occurred driven by atmospheric photochemistry and/or degradation of organic carbon.

  9. Centennial to millennial variations of atmospheric methane during the early Holocene

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Woong; Ahn, Jinho; Brook, Edward

    2015-04-01

    Atmospheric CH4 is one of the most important greenhouse gases. Ice core studies revealed strong correlations between millennial CH4 variations and Greenland climate during the last glacial period. However, millennial to sub-millennial CH4 variations during interglacial periods are not well studied. Recently, several high-resolution data sets have been produced for the late Holocene, but it is difficult to distinguish natural- from anthropogenic changes. In contrast, the methane budget of the early Holocene is not affected by anthropogenic disturbances, thus may help us better understand natural CH4 control mechanisms under interglacial climate boundary conditions. Here we present our new high-precision and high-resolution atmospheric CH4 record from Siple Dome ice core, Antarctica that covers the early Holocene. We used our new wet extraction system at Seoul National University that shows a good precision of ~1 ppb. Our data show several tens of ppb of centennial- to millennial CH4 variations and an anti-correlative evolution with Greenland climate on the millennial time scale. The CH4 record could have been affected by many different types of forcing, including temperature, precipitation (monsoon intensity), biomass burning, sea surface temperature, and solar activity. According to our data, early Holocene CH4 is well correlated with records of hematite stained grains (HSG) in North Atlantic sediment records, within age uncertainties. A red-noise spectral analysis yields peaks at frequencies of ~1270 and ~80 years, which are similar to solar frequencies, but further investigations are needed to determine major controlling factor of atmospheric CH4during the early Holocene.

  10. Comparative Climatology of Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Mackwell, Stephen J.; Simon-Miller, Amy A.; Harder, Jerald W.; Bullock, Mark A.

    Public awareness of climate change on Earth is currently very high, promoting significant interest in atmospheric processes. We are fortunate to live in an era where it is possible to study the climates of many planets, including our own, using spacecraft and groundbased observations as well as advanced computational power that allows detailed modeling. Planetary atmospheric dynamics and structure are all governed by the same basic physics. Thus differences in the input variables (such as composition, internal structure, and solar radiation) among the known planets provide a broad suite of natural laboratory settings for gaining new understanding of these physical processes and their outcomes. Diverse planetary settings provide insightful comparisons to atmospheric processes and feedbacks on Earth, allowing a greater understanding of the driving forces and external influences on our own planetary climate. They also inform us in our search for habitable environments on planets orbiting distant stars, a topic that was a focus of Exoplanets, the preceding book in the University of Arizona Press Space Sciences Series. Quite naturally, and perhaps inevitably, our fascination with climate is largely driven toward investigating the interplay between the early development of life and the presence of a suitable planetary climate. Our understanding of how habitable planets come to be begins with the worlds closest to home. Venus, Earth, and Mars differ only modestly in their mass and distance from the Sun, yet their current climates could scarcely be more divergent. Our purpose for this book is to set forth the foundations for this emerging science and to bring to the forefront our current understanding of atmospheric formation and climate evolution. Although there is significant comparison to be made to atmospheric processes on nonterrestrial planets in our solar system — the gas and ice giants — here we focus on the terrestrial planets, leaving even broader comparisons to a future volume. Our authors have taken on the task to look at climate on the terrestrial planets in the broadest sense possible — by comparing the atmospheric processes at work on the four terrestrial bodies, Earth, Venus, Mars, and Titan (Titan is included because it hosts many of the common processes), and on terrestrial planets around other stars. These processes include the interactions of shortwave and thermal radiation with the atmosphere, condensation and vaporization of volatiles, atmospheric dynamics, chemistry and aerosol formation, and the role of the surface and interior in the long-term evolution of climate. Chapters herein compare the scientific questions, analysis methods, numerical models, and spacecraft remote sensing experiments of Earth and the other terrestrial planets, emphasizing the underlying commonality of physical processes. We look to the future by identifying objectives for ongoing research and new missions. Through these pages we challenge practicing planetary scientists, and most importantly new students of any age, to find pathways and synergies for advancing the field. In Part I, Foundations, we introduce the fundamental physics of climate on terrestrial planets. Starting with the best studied planet by far, Earth, the first chapters discuss what is known and what is not known about the atmospheres and climates of the terrestrial planets of the solar system and beyond. In Part II, Greenhouse Effect and Atmospheric Dynamics, we focus on the processes that govern atmospheric motion and the role that general circulation models play in our current understanding. In Part III, Clouds and Hazes, we provide an in-depth look at the many effects of clouds and aerosols on planetary climate. Although this is a vigorous area of research in the Earth sciences, and very strongly influences climate modeling, the important role that aerosols and clouds play in the climate of all planets is not yet well constrained. This section is intended to stimulate further research on this critical subject. The study of climate involves much more than understanding atmospheric processes. This subtlety is particularly appreciated for Earth, where chemical cycles, geology, ocean influences, and biology are considered in most climate models. In Part IV, Surface and Interior, we look at the role that geochemical cycles, volcanism, and interior mantle processes play in the stability and evolution of terrestrial planetary climates. There is one vital commonality between the climates of all the planets of the solar system: Regardless of the different processes that dominate each of the climates of Earth, Mars, Venus, and Titan, they are all ultimately forced by radiation from the same star, albeit at variable distances. In Part V, Solar Influences, we discuss how the Sun's early evolution affected the climates of the terrestrial planets, and how it continues to control the temperatures and compositions of planetary atmospheres. This will be of particular interest as models of exoplanets, and the influences of much different stellar types and distances, are advanced by further observations. Comparisons of atmospheric and climate processes between the planets in our solar system has been a focus of numerous conferences over the past decade, including the Exoclimes conference series. In particular, this book project was closely tied to a conference on Comparative Climatology of Terrestrial Planets that was held in Boulder, Colorado, on June 25-28, 2012. This book benefited from the opportunity for the author teams to interact and obtain feedback from the broader community, but the chapters do not in general tie directly to presentations at the conference. The conference, which was organized by a diverse group of atmospheric and climate scientists led by Mark Bullock and Lori Glaze, sought to build connections between the various communities, focusing on synergies and complementary capabilities. Discussion panels at the end of most sessions served to build connections between planetary, solar, astrophysics, and Earth climate scientists. These presentations and discussions allowed broadening of the author teams and tuning of the material in each chapter. Comparative Climatology of Terrestrial Planets is the 38th book in the University of Arizona Press Space Sciences Series. The support and guidance from General Editor Richard Binzel has been critical in timely production of a quality volume. Renée Dotson of the Lunar and Planetary Institute, with support from Elizabeth Cunningham and Katy Buckaloo, provided outstanding help in the management of the book project and especially in the preparation of the chapters for publication. Her quiet reminders and attention to detail are critical in making the Space Science Series such an asset for the planetary science community. As for so many other books in this series, William Hartmann used his artistic skills to masterfully capture the book's theme. Much gratitude is owed to Adriana Ocampo of NASA Headquarters for her support of both the conference and book projects and her shepherding of the NASA contributions from the diverse groups within the Science Mission Directorate. Equally, James Green and Jonathan Rall of NASA Headquarters provided the financial resources and corporate oversight that helped make this book project such a success.

  11. Filling-in of far-red and near-Infrared solar lines by terrestrial and atmospheric effects: simulations and space-based observations from SCIAMACHY and GOSAT

    NASA Astrophysics Data System (ADS)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Middleton, E. M.; Campbell, P. K. E.; Yoshida, Y.; Kuze, A.; Corp, L. A.

    2012-01-01

    Global mapping of terrestrial vegetation fluorescence from space has recently been accomplished with high spectral resolution (ν/Δν>35 000) measurements from the Japanese Greenhouse gases Observing SATellite (GOSAT). These data are of interest because they can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Quantifying the impact of fluorescence on the O2-A band is important as this band is used for cloud- and aerosol-characterization for other trace-gas retrievals including CO2. Here, we explore whether fluorescence information can be derived from space using potentially lower-cost hyperspectral instrumentation, i.e., more than an order of magnitude less spectral resolution (ν/Δν ∼1600) than GOSAT, with a relatively simple algorithm. We simulate the filling-in, from various atmospheric and terrestrial effects, of one of the few wide and deep solar Fraunhofer lines in the long-wave tail of the fluorescence emission region, the calcium (Ca) II line near 866 nm. We then examine filling-in of this line using the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) satellite instrument. We develop and apply methodology to correct for various instrumental artifacts that produce false filling-in of solar lines in satellite radiance measurements. We then compare the derived additive near-InfraRed (NIR) signal at 866 nm, that fills in the Ca II line, with larger signals retrieved at 758 and 770 nm on the shoulders of the O2-A feature from GOSAT that are presumably due primarily to vegetation fluorescence. Finally, we compare temporal and spatial variations of GOSAT and SCIAMACHY additive signals with those of the Enhanced Vegetation Index (EVI) from the MODerate-resolution Imaging Spectroradiometer (MODIS). Although the observed filling-in signal from SCIAMACHY is extremely weak at 866 nm, the spatial and temporal patterns of the derived additive signal are consistent with a vegetation source, chlorophyll-a fluorescence being a plausible candidate. We also show that filling-in occurs at 866 nm over some barren areas, possibly originating from luminescent minerals in rock and soil.

  12. Leaf fossil record suggests limited influence of atmospheric CO2 on terrestrial productivity prior to angiosperm evolution

    PubMed Central

    Boyce, C. Kevin; Zwieniecki, Maciej A.

    2012-01-01

    Declining CO2 over the Cretaceous has been suggested as an evolutionary driver of the high leaf vein densities (728 mm mm?2) that are unique to the angiosperms throughout all of Earth history. Photosynthetic modeling indicated the link between high vein density and productivity documented in the modern low-CO2 regime would be lost as CO2 concentrations increased but also implied that plants with very low vein densities (less than 3 mm mm?2) should experience substantial disadvantages with high CO2. Thus, the hypothesized relationship between CO2 and plant evolution can be tested through analysis of the concurrent histories of alternative lineages, because an extrinsic driver like atmospheric CO2 should affect all plants and not just the flowering plants. No such relationship is seen. Regardless of CO2 concentrations, low vein densities are equally common among nonangiosperms throughout history and common enough to include forest canopies and not just obligate shade species that will always be of limited productivity. Modeling results can be reconciled with the fossil record if maximum assimilation rates of nonflowering plants are capped well below those of flowering plants, capturing biochemical and physiological differences that would be consistent with extant plants but previously unrecognized in the fossil record. Although previous photosynthetic modeling suggested that productivity would double or triple with each Phanerozoic transition from low to high CO2, productivity changes are likely to have been limited before a substantial increase accompanying the evolution of flowering plants. PMID:22689947

  13. The young sun, the early earth and the photochemistry of oxygen, ozone and formaldehyde in the early atmosphere

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Levine, J. S.; Augustsson, T. R.; Imhoff, C. L.; Goldman, I.; Hubickyj, O.

    1986-01-01

    Recent work on the evolution of the solar nebula and the subsequent formation of planets is reviewed, and the stages of star formation thought to lead to a protosun and an accompanying solar nebula are considered. Photochemical results suggest that concentrations of O2, O3, and H2CO, and the ratio of CO/CO2 in the prebiological paleoatmosphere are very sensitive to atmospheric levels of H2O and CO2 and to the flux of incident solar ultraviolet. For enhanced levels of CO2 and solar UV, surface levels of O2 may have approached the parts per billion level in the prebiological paleoatmosphere. It is suggested that 10 percent or more of the enhanced H2CO production could have been rained out of the atmosphere into the early oceans where synthesis into more complex organic molecules could have taken place. CO/CO2 values of greater than unity could have been possible for enhanced levels of solar UV flux.

  14. Solar terrestrial observatory

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Eight basic solar-terrestrial scientific objectives that benefit from the Shuttle/Platform approach and a program of measurements for each are discussed. The objectives are to understand: (1) solar variability, (2) wave-particle processes, (3) magnetosphere-ionosphere mass transport, (4) the global electric circuit, (5) upper atmospheric dynamics, (6) middle atmospheric chemistry and energetics, (7) lower atmospheric turbidity, and (8) planetary atmospheric waves. A two stage approach to a multidisciplinary payload is developed: an initial STO, that uses a single platform in a low-Earth orbit, and an advanced STO that uses two platforms in differing orbits.

  15. Reconciling estimates of the contemporary North American carbon balance among an inventory-based approach, terrestrial biosphere models, and atmospheric inversions

    NASA Astrophysics Data System (ADS)

    Hayes, D. J.; Turner, D. P.; Stinson, G.; McGuire, A. D.; Wei, Y.; West, T. O.; Heath, L. S.; De Jong, B. H.; McConkey, B. G.; Birdsey, R.; Kurz, W. A.; Jacobson, A. R.; Huntzinger, D. N.; Pan, Y.; Post, W. M.; Cook, R. B.

    2011-12-01

    Although the exact contribution is uncertain, North American (NA) ecosystems are thought to have a significant influence on the global carbon budget by acting as a large sink of atmospheric CO2 in recent decades. Assessments of the continental carbon balance have been based on various scaling approaches, including top-down atmospheric inverse models (AIMs) and bottom-up terrestrial biosphere models (TBMs), which vary widely in their estimates of the magnitude, timing and spatial pattern of sources and sinks of atmospheric CO2. A suite of results on NA ecosystem carbon flux from extant model simulations (based on both AIMs and TBMs) have been organized by the North American Carbon Program (NACP). Here, we assemble and analyze available inventory-based data on NA ecosystem carbon cycle components as an additional perspective alongside the NACP models. We develop an inventory-based approach for estimating net ecosystem exchange (NEE) over NA that notably retains information on the spatial distribution of the vertical fluxes as well as accounting for lateral transfers. The total inventory-based NEE estimate of a -327 ± 252 TgC yr-1 sink for NA was driven primarily by CO2 uptake in the Forest Lands (-248 TgC yr-1) and in the Crop Lands (-297 TgC yr-1) sectors. These sinks are counteracted by the CO2 source estimated for the Other Lands sector (+218 TgC yr-1), where much of the forest and crop products are returned to the atmosphere through consumption and decay. The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr-1) due to land use change. We compare these inventory-based estimates with results from the TBMs and AIMs, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr-1 and -931 TgC yr-1, respectively. Additional fluxes not measured by the inventories, though highly uncertain, could add an additional -239 TgC yr-1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches. Depending on the approach, the estimates of the NA sink presented here represent between 18% and 52% of continental fossil fuel emissions over this same time period.

  16. Solution of Time-dependent Hydrodynamic Equations and application in Early Earth's Atmosphere

    NASA Astrophysics Data System (ADS)

    Tian, F.; Toon, O. B.; Pavlov, A. A.; Sterck, H. D.

    2003-12-01

    Hydrodynamic escape has important applications in the formation and evolution of planetary atmospheres. Watson et. al. (1981) treated the time-independent hydrodynamic equations by assuming single layer heating and this approach has been followed by researches in this field since then. Solutions to the time-independent hydrodynamic equations are difficult to find due to the existence of a singularity point. In our work, the Lax-Friedrichs scheme is used to solve the 1D time-dependent hydrodynamic equations without the single layer heating approximation. Our results show that variables such as energy input rate at the top of the atmosphere, density and temperature at the homopause have a non-linear impact on the escape flux. In our preliminary calculations, for the same hydrogen mixing ratio near homopause in Earth's atmosphere, hydrodynamic escape flux driven by intense solar EUV heating is much smaller than the diffusion limited escape flux. This escape rate suggests that the huge amount of H2 outgassing from interior of the Earth to compensate the previously assumed large scale escape may not be necessary to support substantial CH4 mixing ratios in the early Earth's atmosphere. FT is supported by the CU Astrobiology Institute.

  17. Quantifying the Net Exchanges of Carbon Dioxide and Methane between the Atmosphere and Terrestrial Biosphere in Northern High Latitudes

    NASA Astrophysics Data System (ADS)

    Zhuang, Qianlai

    2015-04-01

    Wetlands occupy vast areas in boreal regions (above 45oN) and play an important role in the regional exchanges of carbon dioxide (CO2) and methane (CH4) between land ecosystems and the atmosphere. We have developed a biogeochemistry model that considers the effects of thawing permafrost and complex hydrological dynamics on plant photosynthesis, plan nutrient uptake, and both aerobic and anaerobic decompositions of organic carbon of wetland ecosystems in this region. The process-based biogeochemistry model was applied to evaluate how spatial and temporal variations in both CO2 and CH4 have changed in the last century and will change during this century. Our current estimate of net CH4 emissions from this region is 67.8±6.2 Tg CH4 yr-1 during the period of 1993-2004. In contrast, we estimate that the region acts as a net carbon sink of -1.28±0.03 Pg C yr-1 with a persistent wetland carbon sink from -0.38 to -0.41 Pg C yr-1 and an upland sink from -0.6 to -1.1 Pg C yr-1. Our analysis indicates that wetlands play a disproportionally important role in affecting regional greenhouse gas budgets given that they only occupy a small fraction of the total land area in the region. In addition, this talk will present our model projections of both CO2 and CH4 dynamics in the region during the 21st century. More importantly, this talk will make recommendations on data collection and model improvement based on our decade-long modeling efforts in this region.

  18. A Reducing Atmosphere From Out-gassing of the Early Earth

    NASA Astrophysics Data System (ADS)

    Schaefer, L.; Fegley, B., Jr.

    2005-08-01

    Earth's present atmosphere originated from out-gassing of volatile-bearing grains. We calculated the composition of volatiles out-gassed from chondritic planetary bodies. We present results for average CI, CM, CV, H, L, and EH chondrites, which are the building blocks of the Earth. From the oxygen-isotope mixing (OIM) model, we calculated a composition of 70% EH, 21% H, 5% CV, and 4% CI chondritic matter for the early Earth. The major out-gassed volatiles for these starting compositions are CH4, N2, NH3, H2, and H2O. The Miller-Urey experiment demonstrated that a reducing atmosphere like this generates amino acids and other organic compounds that are essential for the formation of life. This work is supported by the NASA Astrobiology Program. \\leavevmode \\epsfxsize=0.9\\hsize \\epsfbox{49.eps}

  19. Recharge of the early atmosphere of Mars by impact-induced release of CO2

    NASA Technical Reports Server (NTRS)

    Carr, Michael H.

    1989-01-01

    The question as to whether high impact rates early in the history of Mars could have aided in maintaining a relatively thick CO2 atmosphere is discussed. Such impacts could have released CO2 into the atmosphere by burial, by shock-induced release during impact events, and by the addition of carbon to Mars from the impacting bolides. On the assumption that cratering rates on Mars were comparable to those of the moon's Nectarial period, burial rates are a result of 'impact gardening' at the end of heavy bombardment are estimated to have ranged from 20 to 45 m/million years; at these rates, 0.1-0.2 bar of CO2 would have been released every 10 million years as a result of burial to depths at which carbonate dissociation temperatures are encountered.

  20. Recharge of the early atmosphere of Mars by impact-induced release of CO2

    NASA Astrophysics Data System (ADS)

    Carr, M. H.

    1989-06-01

    The question as to whether high impact rates early in the history of Mars could have aided in maintaining a relatively thick CO2 atmosphere is discussed. Such impacts could have released CO2 into the atmosphere by burial, by shock-induced release during impact events, and by the addition of carbon to Mars from the impacting bolides. On the assumption that cratering rates on Mars were comparable to those of the moon's Nectarial period, burial rates are a result of 'impact gardening' at the end of heavy bombardment are estimated to have ranged from 20 to 45 m/million years; at these rates, 0.1-0.2 bar of CO2 would have been released every 10 million years as a result of burial to depths at which carbonate dissociation temperatures are encountered.

  1. Early Validation Analyses of Atmospheric Profiles from EOS MLS on the Aura Satellite

    NASA Technical Reports Server (NTRS)

    Froidevaux, Lucien; Livesey, Nathaniel J.; Read, William G.; Jiang, Yibo B.; Jimenez, Carlos; Filipiak, Mark J.; Schwartz, Michael J.; Santee, Michelle L.; Pumphrey, Hugh C.; Jiang, Jonathan H.; Wu, Dong L.; Manney, Gloria L.; Drouin, Brian J.; Waters, Joe W.; Fetzer, Eric J.; Bernath, Peter F.; Boone, Chris D.; Walker, Kaley A.; Jucks, Kenneth W.; Geoffrey, C. Toon; Margitan, James J.; Sen, Bhaswar; Webster, Christopher R.; Christensen, Lance E.; Elkins, James W.

    2006-01-01

    We present results of early validation studies using retrieved atmospheric profiles from the Earth Observing System Microwave Limb Sounder (MLS) instrument on the Aura satellite. 'Global' results are presented for MLS measurements of atmospheric temperature, ozone, water vapor, hydrogen chloride, nitrous oxide, nitric acid, and carbon monoxide, with a focus on the January-March 2005 time period. These global comparisons are made using long-standing global satellites and meteorological datasets, as well as some measurements from more recently launched satellites. Comparisons of MLS data with measurements from the Ft. Sumner, NM, September 2004 balloon flights are also presented. Overall, good agreeement is obtained, often within 5% to 10%, but we point out certain issues to resolve and some larger systematic differences; some artifacts in the first publicly released MLS (version 1.5) dataset are noted.We comment briefly on future plans for validation and software improvements.

  2. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene

    PubMed Central

    Levy, Richard; Harwood, David; Florindo, Fabio; Sangiorgi, Francesca; Tripati, Robert; von Eynatten, Hilmar; Tripati, Aradhna; DeConto, Robert; Fielding, Christopher; Field, Brad; Golledge, Nicholas; McKay, Robert; Naish, Timothy; Olney, Matthew; Pollard, David; Schouten, Stefan; Talarico, Franco; Warny, Sophie; Willmott, Veronica; Acton, Gary; Panter, Kurt; Paulsen, Timothy; Taviani, Marco

    2016-01-01

    Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23–14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3–4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2 concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO2. These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2 during the early to mid-Miocene. PMID:26903644

  3. Antarctic ice sheet sensitivity to atmospheric CO2 variations in the early to mid-Miocene.

    PubMed

    Levy, Richard; Harwood, David; Florindo, Fabio; Sangiorgi, Francesca; Tripati, Robert; von Eynatten, Hilmar; Gasson, Edward; Kuhn, Gerhard; Tripati, Aradhna; DeConto, Robert; Fielding, Christopher; Field, Brad; Golledge, Nicholas; McKay, Robert; Naish, Timothy; Olney, Matthew; Pollard, David; Schouten, Stefan; Talarico, Franco; Warny, Sophie; Willmott, Veronica; Acton, Gary; Panter, Kurt; Paulsen, Timothy; Taviani, Marco

    2016-03-29

    Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2concentrations were similar to those projected for coming centuries. Importantly, this time interval includes the Miocene Climatic Optimum, a period of global warmth during which average surface temperatures were 3-4 °C higher than today. Miocene sediments in the ANDRILL-2A drill core from the Western Ross Sea, Antarctica, indicate that the Antarctic ice sheet (AIS) was highly variable through this key time interval. A multiproxy dataset derived from the core identifies four distinct environmental motifs based on changes in sedimentary facies, fossil assemblages, geochemistry, and paleotemperature. Four major disconformities in the drill core coincide with regional seismic discontinuities and reflect transient expansion of grounded ice across the Ross Sea. They correlate with major positive shifts in benthic oxygen isotope records and generally coincide with intervals when atmospheric CO2concentrations were at or below preindustrial levels (∼280 ppm). Five intervals reflect ice sheet minima and air temperatures warm enough for substantial ice mass loss during episodes of high (∼500 ppm) atmospheric CO2 These new drill core data and associated ice sheet modeling experiments indicate that polar climate and the AIS were highly sensitive to relatively small changes in atmospheric CO2during the early to mid-Miocene. PMID:26903644

  4. Sensitivity of terrestrial ecosystems to elevated atmospheric CO{sub 2}: Comparisons of model simulation studies to CO{sub 2} effect

    SciTech Connect

    Pan, Y.

    1995-06-01

    In the context of a project to compare terrestrial ecosystem models, the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP), we have analyzed how three biogeochemistry models link plant growth to doubled atmospheric CO{sub 2}. A common set of input data was used to drive three biogeochemistry models, BIOME-BGC, CENTURY and TEM. For the continental United States the simulation results show that with doubled CO{sub 2}, NPP increased by 8.7%, 5.0% and 10.8% for TEM, CENTURY and BIOME-BGC, respectively. At the biome level the range of NPP estimates varied considerably among models. TEM-simulated enhancement of NPP ranged from 2% to 28%; CENTURY, from 2% to 9%; and BIOME-BGC, from 4% to 27%. A transect analysis across several biomes along a latitude at 41.5 N shows that the TEM-simulated CO{sub 2} enhancement of NPP ranged from 0% to 22%; CENTURY, from 1% to 10% and BIOME-BGC, from 1% to 63%. In this study, we have investigated the underlying mechanisms of the three models to reveal how increased CO{sub 2} affects photosynthesis rate, water using efficiency and nutrient cycles. The relative importance of these mechanisms in each of the three biogeochemistry models will be discussed.

  5. Quantifying Net Carbon Exchanges Between the Atmosphere and Terrestrial Biosphere in the Arctic: What Have We Learned through Decade Regional Modeling Studies?

    NASA Astrophysics Data System (ADS)

    Zhuang, Q.

    2014-12-01

    Observed Arctic warming has been projected to continue in this century. Permafrost degradation is thus expected to continue, exposing large amounts of carbon for decomposition. Dynamics of Arctic landscape and hydrology are complicated due to changing climate and thawing permafrost, affecting the carbon biogeochemical cycling in the region. Further, human activities together with changing climate transform the regional land use and land cover, including wildfires, logging, and agricultural land conversion. This presentation will review the effects of factors, controls, and processes as well as landscape types (e.g., forests vs. lakes) on carbon biogeochemistry based on regional modeling studies and observations. Specific effects on carbon dynamics to be discussed will include: 1) thawing permafrost; 2) fire disturbances; 2) atmospheric carbon dioxide; 3) inorganic and organic nitrogen uptake by plants; 4) priming; 5) aerobic and anaerobic organic matter decomposition; and 6) various complexities of microbial physiology of soils. Partitioning the contribution of these processes to regional carbon dynamics shall help us improve the terrestrial biogeochemistry models, an important component of Earth System Models that are used to project our future climate.

  6. Use of stable isotopes in the study of CO2 fluxes between terrestrial vegetation and the atmosphere in shortgrass steppe

    NASA Astrophysics Data System (ADS)

    Shim, J. H.; Pendall, E.; Ojima, D. S.

    2001-12-01

    The shortgrass steppe ecosystem is ecologically sensitive to climate change due the mixture of C3 and C4 plant species and the semi-arid environment. In order to make reliable predictions about effects of climate change on plant communities, it is prerequisite to understand how individual C3 and C4 plant functional groups contribute gross photosynthetic activity and respiration in the semi-arid grassland. We observed diurnal and seasonal changes of CO2, CH4 and N2O fluxes, and associated isotopic signatures of 13C and 18O from air flasks above canopy at 1 and 2m heights, to estimate changes in activity of C3 andC4 plants and gross photosynthesis and respiration fluxes during the growing seasons of 2000 and 2001 in the shortgrass steppe region of north-eastern Colorado. Flasks were collected from a tower instrumented with Bowen ratio equipment, allowing us to evaluate latent heat fluxes simultaneously with flask measurements. We partitioned gross fluxes using the 13C and 18O isotopic mass balance method outlined by Yakir and Wang (1996). The results indicated that the grass canopy was a sink for CO2 during the daytime, as we expected, but peak times for CO2 uptake varied seasonally. Peak patterns of daily photosynthesis were attributed microclimatic variables such as leaf to air vapor pressure deficit related to stomatal conductance. The diurnal patterns of gradients for d13 C were similar to those for d18O. Discrimination against 13 C associated with CO2 fixation and isotopic exchange with 18O-enriched leaf water during daytime may be correlated process in this ecosystem. Seasonally, gross photosynthesis was positively correlated to magnitude of depleted d13C of CO2 from all sources, latent heat flux at night, and total greenness of plants. Seasonal changes in atmospheric d13C and d18O values, CO2 fluxes and gross photosynthesis reflected changes in plant biomass and its composition by functional groups (C3, C4 and CAM) and environmental variables especially related to hydrological cycling such as evapotranspiration. We compared local-scale (10 to 100 m) flask results with observations from chambers to assess fine-scale (0.1 to 1 m) differences in respiration and 13C and 18O values from selected species and bare ground.

  7. Century-scale shifts in early holocene atmospheric CO2 concentration

    PubMed

    Wagner; Bohncke; Dilcher; Kurschner; van Geel B; Visscher

    1999-06-18

    The inverse relation between atmospheric carbon dioxide concentration and stomatal frequency in tree leaves provides an accurate method for detecting and quantifying century-scale carbon dioxide fluctuations. Stomatal frequency signatures of fossil birch leaves reflect an abrupt carbon dioxide increase at the beginning of the Holocene. A succeeding carbon dioxide decline matches the Preboreal Oscillation, a 150-year cooling pulse that occurred about 300 years after the onset of the Holocene. In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the stomatal frequency signal suggests that early Holocene carbon dioxide concentrations were well above 300 ppmv. PMID:10373111

  8. Regional atmospheric deposition patterns of Ag, As, Bi, Cd, Hg, Mo, Sb and Tl in a 188,000 km 2 area in the European arctic as displayed by terrestrial moss samples-long-range atmospheric transport vs local impact

    NASA Astrophysics Data System (ADS)

    Reimann, Clemens; De Caritat, Patrice; Halleraker, Jo H.; Finne, Tor Erik; Boyd, Rognvald; Jæger, Øystein; Volden, Tore; Kashulina, Galina; Bogatyrev, Igor; Chekushin, Viktor; Pavlov, Vladimir; Äyräs, Matti; Räisänen, Marja Liisa; Niskavaara, Heikki

    The regional atmospheric deposition patterns of Ag, As, Bi, Cd, Hg, Mo, Sb and Tl have been mapped in a 188,000 km2 area of the European Arctic (N Finland, N Norway, NW Russia) using the moss technique. The Russian nickel mining and smelting industry (Nikel and Zapoljarnij (Pechenganikel) and Monchegorsk (Severonikel)) in the eastern part of the survey area represents two of the largest point sources for S0 2 and metal emissions on a world wide basis. In contrast, parts of northern Finland and northern Norway represent still some of the most pristine areas in Europe. The terrestrial mosses Hylocomium splendens and Pleurozium schreberi were used as monitors of airborne deposition. Samples in all three countries were collected during the summer of 1995 and analysed in one laboratory using ICP-MS. Maps for most elements clearly show elevated element concentrations near the industrial sites and delineate the extent of contamination. Pollution follows the main wind and topographical directions in the area (N-S). The gradients of deposition are rather steep. Background levels for all the elements are reached within 150-200 km from the industrial plants. The relative importance of long-range atmospheric transport of air pollutants from industrial point sources on the world wide increase of heavy metals observed in the atmosphere is thus debatable for many elements. Increasing population and traffic density, accompanied by increasing local dust levels, may play a much more important role than industrial emissions. The regional distribution patterns as displayed in the maps show some striking differences between the elements. The regional distribution of Hg and TI in the survey area is completely dominated by sources other than industry.

  9. An investigation of the small ice cap instability in the Southern Hemisphere with a coupled atmosphere-sea ice-ocean-terrestrial ice model

    NASA Astrophysics Data System (ADS)

    Morales Maqueda, M. A.; Willmott, A. J.; Bamber, J. L.; Darby, M. S.

    A simple climate model has been developed to investigate the existence of the small ice cap instability in the Southern Hemisphere. The model consists of four coupled components: an atmospheric energy balance model, a thermodynamic snow-sea ice model, an oceanic mixed layer model and a terrestrial ice model. Results from a series of experiments involving different degrees of coupling in the model show that the instability appears only in those cases when an explicit representation of the Antarctic ice sheet is not included in the model. In order to determine which physical processes in the ice sheet model lead to a stabilization of the system we have conducted several sensitivity experiments in each of which a given ice sheet process has been removed from the control formulation of the model. Results from these experiments suggest that the feedback between the elevation of the ice sheet and the snow accumulation-ice ablation balance is responsible for the disappearance of the small ice cap instability in our simulation. In the model, the mass balance of the ice sheet depends on the air temperature at sea level corrected for altitude and it is, therefore, a function of surface elevation. This altitude-mass balance feedback effectively decouples the location of the ice edge from any specific sea level isotherm, thus decreasing the model sensitivity to the albedo-temperature feedback, which is responsible for the appearance of the instability. It is also shown that the elevation-radiative cooling feedback tends to stabilize the ice sheet, although its effect does not seem to be strong enough to remove the instability. Another interesting result is that for those simulations which include the terrestrial ice model with elevation-dependent surface mass balance, hysteresis is exhibited, where for a given level of external forcing, two stable solutions with different, non-zero ice-sheet volume and area and different air and ocean temperature fields occur. However, no unstable transition between the two solutions is ever observed. Our results suggest that the small ice cap instability mechanism could be unsuitable for explaining the inception of glaciation in Antarctica.

  10. An Early Pleistocene atmospheric CO2 record based on pedogenic carbonate from the Chinese loess deposits

    NASA Astrophysics Data System (ADS)

    Da, Jiawei; Zhang, Yi Ge; Wang, Hongtao; Balsam, William; Ji, Junfeng

    2015-09-01

    The tight coupling between temperature and atmospheric CO2 is shown by ice core records for the past 0.8 million years (Myr). However, the modern atmospheric partial pressure of CO2 (pCO2) has exceeded previous interglacial pCO2 levels over the past 0.8 Myr, suggesting that the earlier part of the Pleistocene and Pliocene might be a better analog of today's radiative forcing of CO2. The early Pleistocene experienced a constant cooling characterized by the intensification of northern hemisphere glaciations. Existing pCO2 records developed from marine organic matter and inorganic precipitates, however, disagree with the trends and absolute values of CO2 over this time interval. Here we present quantitative interglacial pCO2 estimates from ∼ 2.6- 0.9 Myr using the stable carbon isotopic compositions of pedogenic carbonates collected from the Chinese Loess Plateau (CLP). Our pCO2 records provide the first documentation of pCO2 from continental sedimentary deposits over the early Pleistocene. The successive decrease of our pCO2 records is broadly consistent with the increase in deep-sea δ18O and the overall decline of sea surface temperature (SST) at this time, but in contrast with the increasing peak interglacial pCO2 recorded in ice cores for the last 0.8 Myr.

  11. Abiotic production of NO3 in the atmosphere of Early Mars

    NASA Astrophysics Data System (ADS)

    Gronoff, Guillaume; Airapetian, Vladimir; Hebrard, Eric

    2015-11-01

    Recent Curiosity/SAM measurements of Martian sediments have shown the presence of NO3 trapped in the samples. The ratio of nitrate to perchlorate has been suggested to be an indicator for habitability (Stern et al. 2015). However, the efficiency of the production of nitrate in the atmosphere has never been studied for the case of the active young Sun. To evaluate the effect of the abiotic production of nitrates, we apply our 1D atmospheric photochemical collisional model for the nitrogen-rich and CO2 atmosphere of early Mars, and calculate the production rate of NO3 mediated by the precipitation of energetic particles associated with the coronal mass ejections from the young Sun.We propose a method to check the hypothesis of the abiotic production: if the production is driven by the precipitating particles, then the magnetic shielding would reduce the NO3 production at the equator. Thus, samples collected at high latitudes should contain greater concentration of nitrates if the weathering did not homogenize it.

  12. Early stages in the evolution of the atmosphere and climate on the Earth-group planets

    NASA Technical Reports Server (NTRS)

    Moroz, V. I.; Mukhin, L. M.

    1977-01-01

    The early evolution of the atmospheres and climate of the Earth, Mars and Venus is discussed, based on a concept of common initial conditions and main processes (besides known differences in chemical composition and outgassing rate). It is concluded that: (1) liquid water appeared on the surface of the earth in the first few hundred million years; the average surface temperature was near the melting point for about the first two eons; CO2 was the main component of the atmosphere in the first 100-500 million years; (2) much more temperate outgassing and low solar heating led to the much later appearance of liquid water on the Martian surface, only one to two billion years ago; the Martian era of rivers, relatively dense atmosphere and warm climate ended as a result of irreversible chemical bonding of CO2 by Urey equilibrium processes; (3) a great lack of water in the primordial material of Venus is proposed; liquid water never was present on the surface of the planet, and there was practically no chemical bonding of CO2; the surface temperature was over 600 K four billion years ago.

  13. Terrestrial sequestration

    ScienceCinema

    Charlie Byrer

    2010-01-08

    Terrestrial sequestration is the enhancement of CO2 uptake by plants that grow on land and in freshwater and, importantly, the enhancement of carbon storage in soils where it may remain more permanently stored. Terrestrial sequestration provides an opportunity for low-cost CO2 emissions offsets.

  14. Terrestrial sequestration

    SciTech Connect

    Charlie Byrer

    2008-03-10

    Terrestrial sequestration is the enhancement of CO2 uptake by plants that grow on land and in freshwater and, importantly, the enhancement of carbon storage in soils where it may remain more permanently stored. Terrestrial sequestration provides an opportunity for low-cost CO2 emissions offsets.

  15. Sulfur in the Early Martian Atmosphere Revisited: Experiments with a 3-D Global Climate Model

    NASA Astrophysics Data System (ADS)

    Kerber, L.; Forget, F.; Wordsworth, R.

    2013-09-01

    Data returned from the surface of Mars during the 1970s revealed intriguing geological evidence for a warmer and wetter early martian climate. Dendritic valley networks were discovered by Mariner 9 on ancient Noachian terrain [1], indicating that liquid water had flowed across the surface in the distant past. Since this time, geological investigations into early Martian history have attempted to ascertain the nature and level of activity of the early Martian hydrological cycle [e.g. 2-5] while atmospheric modeling efforts have focused on how the atmosphere could be warmed to temperatures great enough to sustain such activity [see 6-7 for reviews]. Geological and spectroscopic investigations have refined the history and chronology of Noachian Mars over time, and circulation of liquid water has been invoked to explain several spatially and temporally distinct morphological and chemical signatures found in the geological record. Detections of iron and magnesium-rich clays are widespread in the oldest Martian terrains, suggesting a period of pH-neutral aqueous alteration [e.g., 8]. Valley network incision also took place during the Noachian period [9]. Some chains of river valleys and craters lakes extend for thousands of kilometers, suggesting temperatures at least clement enough for sustained ice-covered flow [3,10]. The commencement of valley network incision is not well constrained, but the period of Mg/Fe clay formation appears to have ended before the termination of valley network formation, as the visible fluvial systems appear to have remobilized existing clays rather than forming them [5,8]. There is also evidence that the cessation of valley network formation was abrupt [11]. Towards the end of the Noachian, erosion rates appear to have been significantly higher than during subsequent periods, a process that has also been attributed to aqueous processes [12]. A period of sulfate formation followed, likely characterized by acidic, evaporitic playa environments [8]. A successful working model for the early Martian atmosphere and hydrosphere must be able not only to produce conditions suitable for liquid water at the surface, but also to explain how the nature of this aqueous activity changed over time and eventually diminished. There are two major end-member hypotheses: first, that early Mars was wet and warm, with a sustained greenhouse that made it possible for liquid water to be stable on the surface for extended periods [e.g., 2, 12-14], and second, that early Mars was generally cold, and that most of the aqueous alteration took place underground [3,5] or during transient warm periods tied to impact cratering [15], or volcanism [16]. In both of these scenarios it is generally agreed that in order to make valley networks and sulfate deposits, a hydrological cycle is needed which is able to recycle water from the lowlands back to the highlands (i.e., the one-time emptying of a regional aquifer would not be sufficient to create the observed features) [4,17]. This would require some precipitation to fall on the southern highlands, either flowing overland or filtering into groundwater aquifers. In both cases, volcanic gases (especially SO2) have been suggested as a possible way of creating either a sustained or transient greenhouse. Several researchers have tested the addition of SO2 to climate models in order to assess whether it would provide an adequate amount of greenhouse warming to allow liquid water to flow across the surface [18-21], with differing results. Postawko and Kuhn [18] found a warming effect of 14 K in a 0.1 bar atmosphere with an SO2 abundance of 1000 ppm. Johnson et al. [20] used a 3-D global circulation model and found a warming of 15-25 K for 245 ppm of SO2 in a dry 0.5 bar atmosphere. Tian et al. [21] used a 1-D model to explore a wide range of SO2 mixing values and CO2 partial pressures, finding a warming of around ~25 K for 100 ppm in a 0.5 bar atmosphere with a fully saturated troposphere (~40 K for a 1 bar atmosphere). These authors also included the effect of sulfate aerosol particles, which caused a dramatic cooling effect which more than canceled the warming caused by the SO2 gas [21]. Here we reconsider the efficacy of a sulfurinduced greenhouse in early Noachian history using the LMD (Laboratoire de Météorologie Dynamique) 3-D Generic Climate Model (LMD-GCM), exploring the effects of SO2, H2S, and sulfate and S8 aerosols on the surface temperature, and the expected photochemical lifetime of SO2 in the atmosphere.

  16. Terrestrial Gravity Fluctuations

    NASA Astrophysics Data System (ADS)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^-23 Hz^-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.

  17. Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf-W chronometry.

    PubMed

    Kleine, T; Münker, C; Mezger, K; Palme, H

    2002-08-29

    The timescales and mechanisms for the formation and chemical differentiation of the planets can be quantified using the radioactive decay of short-lived isotopes. Of these, the (182)Hf-to-(182)W decay is ideally suited for dating core formation in planetary bodies. In an earlier study, the W isotope composition of the Earth's mantle was used to infer that core formation was late (> or = 60 million years after the beginning of the Solar System) and that accretion was a protracted process. The correct interpretation of Hf-W data depends, however, on accurate knowledge of the initial abundance of (182)Hf in the Solar System and the W isotope composition of chondritic meteorites. Here we report Hf-W data for carbonaceous and H chondrite meteorites that lead to timescales of accretion and core formation significantly different from those calculated previously. The revised ages for Vesta, Mars and Earth indicate rapid accretion, and show that the timescale for core formation decreases with decreasing size of the planet. We conclude that core formation in the terrestrial planets and the formation of the Moon must have occurred during the first approximately 30 million years of the life of the Solar System. PMID:12198541

  18. Deficit irrigation strategies combined with controlled atmosphere preserve quality in early peaches.

    PubMed

    Falagán, Natalia; Artés, Francisco; Gómez, Perla A; Artés-Hernández, Francisco; Conejero, Wenceslao; Aguayo, Encarna

    2015-10-01

    Due to the water scarcity in the Mediterranean countries, irrigation must be optimized while keeping fruit quality. The effect of deficit irrigation strategies on changes in quality parameters of the early "Flordastar" peaches was studied. The deficit irrigation was programmed according to signal intensity of the maximum daily trunk shrinkage; deficit irrigation plants were irrigated to maintain maximum daily trunk shrinkage signal intensity values close to 1.4 or 1.3 in the case of DI1 or DI2 plants, respectively. Results were compared to a control watered at 150% crop evapotranspiration. Fruits were stored up to 14 days at 0 ℃ and 95% Relative Humidity (RH) in air or in controlled atmosphere (controlled atmosphere; 3-4 kPa O2 and 12-14 kPa CO2), followed by a retail sale period of 4 days at 15 ℃ and 90-95% Relative Humidity in air. Weight losses were lower in controlled atmosphere stored peaches from deficit irrigation. Air-stored fruits developed a more intense red color due to a faster ripening, which was not affected by the type of watering. At harvest, deficit irrigation peaches showed higher soluble solids content, which provided a better sensory evaluation. The soluble phenolic content was initially higher (55.26 ± 0.18 mg gallic acid equivalents/100 g fresh weight) and more stable throughout postharvest life in DI1 fruits than in those from the other irrigation treatments. Concerning vitamin C, control fruits at harvest showed higher ascorbic acid than dehydroascorbic acid content (5.43 versus 2.43 mg/100 g fresh weight, respectively), while water stressed peaches showed the opposite results. The combination of DI2 and controlled atmosphere storage allowed saving a significant amount of water and provided peaches with good overall quality, maintaining the bioactive compounds analyzed. PMID:25280939

  19. Oceanic and atmospheric forcing of early Holocene ice shelf retreat, George VI Ice Shelf, Antarctica Peninsula

    NASA Astrophysics Data System (ADS)

    Smith, James A.; Bentley, Michael J.; Hodgson, Dominic A.; Roberts, Stephen J.; Leng, Melanie J.; Lloyd, Jeremy M.; Barrett, Melissa S.; Bryant, Charlotte; Sugden, David E.

    2007-02-01

    We use lake sediment records from an epishelf lake on Alexander Island to provide a detailed picture of the Holocene history of George VI Ice Shelf (GVI-IS). Core analyses included; micropaleontology (diatoms/foraminifera), stable isotope (δ18O, δ13C), geochemistry (total organic carbon (TOC), total nitrogen (TN), C/N ratios) and grain-size analyses. These data provide robust evidence for one period of past ice shelf absence during the early Holocene. The timing of this period has been constrained by 10 AMS 14C dates performed on mono-specific foraminifera samples. These dates suggest that GVI-IS was absent between c 9600 cal yr BP and c 7730 cal yr BP. This early Holocene collapse immediately followed a period of maximum Holocene warmth that is recorded in some Antarctic ice cores and coincides with an influx of warmer ocean water onto the western Antarctic Peninsula (AP) shelf at c 9000 cal yr BP. The absence of a currently extant ice shelf during this time interval suggests that early Holocene ocean-atmosphere variability in the AP was greater than that measured in recent decades.

  20. An early warning indicator for atmospheric blocking events using transfer operators

    SciTech Connect

    Tantet, Alexis Burgt, Fiona R. van der; Dijkstra, Henk A.

    2015-03-15

    The existence of persistent midlatitude atmospheric flow regimes with time-scales larger than 5–10 days and indications of preferred transitions between them motivates to develop early warning indicators for such regime transitions. In this paper, we use a hemispheric barotropic model together with estimates of transfer operators on a reduced phase space to develop an early warning indicator of the zonal to blocked flow transition in this model. It is shown that the spectrum of the transfer operators can be used to study the slow dynamics of the flow as well as the non-Markovian character of the reduction. The slowest motions are thereby found to have time scales of three to six weeks and to be associated with meta-stable regimes (and their transitions) which can be detected as almost-invariant sets of the transfer operator. From the energy budget of the model, we are able to explain the meta-stability of the regimes and the existence of preferred transition paths. Even though the model is highly simplified, the skill of the early warning indicator is promising, suggesting that the transfer operator approach can be used in parallel to an operational deterministic model for stochastic prediction or to assess forecast uncertainty.

  1. The 557.7 and 297.2 nm lines of O(1S) in the atmospheres of the terrestrial planets

    NASA Astrophysics Data System (ADS)

    Slanger, Tom; Sharpee, Brian; Pejakovic, Dusan; Gattinger, Richard; Llewellyn, Edward J.; McDade, Ian; Siskind, David; Minschwaner, Kenneth

    There are few examples of spectral features in nightglows or in auroras which can be used for relative intensity calibration from space, particularly over a broad wavelength region. One potential candidate is the atomic oxygen line pair at 297.2 nm (the trans-auroral line) and 557.7 nm (the green line). They share the common O(1 S0 ) upper level, and therefore the observed intensity ratio of the O(1 S0 -1 D2 ) and O(1 S0 -3 P1 ) lines has a value that is a quantum-mechanical constant, equal to the ratio of the respective transition probabilities. The recently-published figure of 9.3 ± 0.5 [Gattinger et al., 2009] for I557.7 /I297.2 confirms the earlier value of 9.8 ± 1.0 [Slanger et al., 2006] as well as a previous estimate of 9 [Sharp and Siskind,1989] (all expressed in photon units). Such good agreement suggests that this value can be used for a two-point calibration of orbiting spectrometers where both lines can be observed. O(1 S) emission is seen in the atmospheres of all three terrestrial planets -Venus, Earth, Mars. Comparison with theory is less satisfactory. The current ratio of these transition probabilities recommended by NIST is 16.7, based on numerous calculations. This emphasizes the uncertain-ties inherent in making calculations on strongly forbidden transitions. For the O(1 S) case, the transition to O(3 P) proceeds by spin-orbit interaction, whereas that to O(1 D) involves electric quadrupole interaction. References Gattinger, R.L., et al., Can. J. Phys. 87, 1133, 2009 Sharp, W.E. and D.E. Siskind, Geophys. Res. Lett. 16, 1453, 1989 Slanger, T.G., et al., J. Geophys. Res. 111, A12318, 2006

  2. Filling-In of Broad Far-Red Solar Lines by Terrestrial Fluorescence and Atmospheric Raman Scattering as Detected by SCIAMACHY Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Middleton, E. M.; Campbell, P. K. E.; Yoshida, Y.; Kuze, A.; Corp, L. A.

    2011-01-01

    Global mapping of terrestrial vegetation fluorescence from space has recently been accomplished with high spectral resolution measurements from the Japanese Greenhouse gases Observing SATellite (GOSAT). These data are of interest because they can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Quantifying the impact of fluorescence on the O2-A band is important as this band is used for cloud- and aerosol-characterization for other trace-gas retrievals including CO2. Here, we demonstrate that fluorescence information can be derived from space using potentially lower-cost hyperspectral instrumentation, i.e., more than an order of magnitude less spectral resolution than GOSAT, with a relatively simple algorithm. As a demonstration, we use the filling-in of one of the few wide and deep solar Fraunhofer lines in the red and far-red chlorophylla fluorescence bands, the calcium II line near 866 nm, to retrieve fluorescence with the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) satellite instrument. Although the signal from vegetation fluorescence is extremely weak at 866 nm, our results suggest that useful information may be obtained after adjustments are made to the observed spectra to correct for instrumental artifacts. We compare fluorescence from SCIAMACHY with that retrieved at 758 and 770 nm from similarly-corrected GOSAT data as well with the Enhanced Vegetation Index (EVI) from the MODerate-resolution Imaging Spectroradiometer (MODIS). We also show that filling-in occurs at 866 nm over barren areas, possibly originating from luminescent minerals in rock and soil.

  3. Toward understanding early Earth evolution: prescription for approach from terrestrial noble gas and light element records in lunar soils.

    PubMed

    Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A; Miura, Yayoi N

    2008-11-18

    Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an Earth-Moon dynamical system. PMID:19001263

  4. Toward understanding early Earth evolution: Prescription for approach from terrestrial noble gas and light element records in lunar soils

    PubMed Central

    Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.

    2008-01-01

    Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an Earth–Moon dynamical system. PMID:19001263

  5. The (146,147)Sm-(142,143)Nd systematics of early terrestrial differentiation and the lost continents of the early Earth

    NASA Technical Reports Server (NTRS)

    Harper, Charles L., Jr.; Jacobsen, Stein B.

    1992-01-01

    The very early history of the Earth has been one of the great enduring puzzles in the history of geology. We report evidence which clearly can be described as a vestige of a beginning, because the evidence that we report cannot be interpreted in any other way except as a geochemical signal of processes active in the very early history of the Earth. The evidence itself is a very small anomaly in the abundance of SM-146. The primary aims of this study were to: (1) verify the existence of the 'lost continents' of the Hadean era; and (2) determine their mean age.

  6. Neoarchean paleoweathering of tonalite and metabasalt: Implications for reconstructions of 2.69Ga early terrestrial ecosystems and paleoatmospheric chemistry

    USGS Publications Warehouse

    Driese, S.G.; Jirsa, M.A.; Ren, M.; Brantley, S.L.; Sheldon, N.D.; Parker, D.; Schmitz, M.

    2011-01-01

    Field and laboratory investigations of a 2690.83Ma (207Pb/206Pb age of Saganaga Tonalite) unconformity exposed in outcrop in northeastern Minnesota, USA, reveal evidence for development of a deep paleoweathering profile with geochemical biosignatures consistent with the presence of microbial communities and weakly oxygenated conditions. Weathering profiles are characterized by a 5-50m thick regolith that consists of saprolitized Saganaga Tonalite and Paulson Lake succession basaltic metavolcanic rocks retaining rock structure, which is cross-cut by a major unconformity surface marking development of a successor basin infilled with alluvial deposits. The regolith and unconformity are overlain by thick conglomerate deposits that contain both intrabasinal (saprock) as well as extrabasinal detritus. Thin-section microscopy and electron microprobe analyses reveal extensive hydrolysis and sericitization of feldspars, exfoliation and chloritization of biotite, and weathering of Fe-Mg silicates and Cu-Fe sulfides; weathering of Fe-Ti oxides was relatively less intense than for other minerals and evidence was found for precipitation of Fe oxides. Geochemical analyses of the tonalite, assuming immobile TiO2 during weathering (??Ti,j), show depletion of SiO2, Al2O3, Na2O, CaO, MgO, and MnO, and to a lesser degree of K2O, relative to least-weathered parent materials. Significant Fe was lost from the tonalite. A paleoatmospheric pCO2 of 10-50 times PAL is estimated based on geochemical mass-balance of the tonalite profile and assuming a formation time of 50-500Kyr. Interpretations of metabasalt paleoweathering are complicated by additions of sediment to the profile and extensive diagenetic carbonate (dolomite) overprinting. Patterns of release of P and Fe and retention of Y and Cu in tonalite are consistent with recent laboratory experiments of granite weathering, and with the presence of acidic conditions in the presence of organic ligands (produced, for example, by a primitive microbial community) during weathering. Cu metal in the profile may document lower pO2 than present day at the surface. Comparison with previous studies of weathered tonalite and basalt (Denison, 2.45-2.22Ga) in Ontario, Canada, reveal general similarities in paleoweathering with our study, as well as important differences related to lower paleoatmospheric pO2 and terrestrial biosignature for the older Minnesota profile. A falling water table in the Alpine Lake locality is presumed to have promoted formation of this gossan-like deep-weathering system that extends to 50-m depth. ?? 2011 Elsevier B.V.

  7. Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S.

    NASA Astrophysics Data System (ADS)

    Hadley, J. L.; Kuzeja, P.; Mulcahy, T.; Singh, S.

    2008-12-01

    Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S. Julian Hadley, Paul Kuzeja, Safina Singh and Thomas Mulcahy Transfers of water vapor from terrestrial ecosystems to the atmosphere affect regional hydrology, weather and climate over short time scales, and forest-atmosphere CO2 exchange affects global climate over long timescales. To better understand these effects for forests dominated by two very different tree species, we measured forest-atmosphere water vapor and CO2 transfers by the eddy flux technique to at two sites in central Massachusetts USA for three years. Average annual evapotranspiration (ET) for a young deciduous forest dominated by red oak (Quercus rubra L., the most abundant tree species in the area), was about 430 mm or 25 percent greater than for a coniferous forest dominated by 100 to 230 year old eastern hemlock (Tsuga canadensis L.). The difference in ET was most pronounced in July and August when the deciduous forest lost about 50 percent more water by ET in the average year (192 mm for oak forest versus 130 mm for hemlock). These data indicate that if deciduous trees with similar physiology to red oak replace hemlocks, summertime ET will increase while summer streamflow, soil water content and the extent of year- round wetlands will decrease. Increased summertime ET should also lead to slightly higher regional atmospheric humidity and precipitation. Hemlock-to-deciduous forest conversion has occurred from North Carolina to southern New England and is continuing northward as a lethal insect pest, the hemlock woolly adelgid (Adelges tsugae Annand) continues to kill hemlocks. Average annual carbon storage for the old hemlock forest in our study was about 3.3 Mg C/ha, nearly equal to the average for the deciduous forest, 3.5 Mg C/ha. This calls into question ecological theory that predicts large declines in the rate of carbon uptake for old forests, and indicates that annual carbon storage will not necessarily increase over the long term after hemlock trees are killed by the hemlock woolly adelgid and replaced by deciduous species. Maximum monthly carbon storage in the hemlock forest occurred in spring (April and May) and was enhanced by early soil thawing and cessation of nighttime frost. This pattern is probably common to many evergreen conifers in the northeastern U.S., so climate warming that includes an earlier end to freezing temperatures in spring should increase C storage by conifer forests in the northeastern U.S. - unless this effect is canceled out by reduced C uptake or enhanced C loss due to changes in summer and fall climate.

  8. Terrestrial nest-building by wild chimpanzees (Pan troglodytes): implications for the tree-to-ground sleep transition in early hominins.

    PubMed

    Koops, Kathelijne; McGrew, William C; Matsuzawa, Tetsuro; Knapp, Leslie A

    2012-07-01

    Nest-building is a great ape universal and arboreal nesting in chimpanzees and bonobos suggests that the common ancestor of Pan and Homo also nested in trees. It has been proposed that arboreal nest-building remained the prevailing pattern until Homo erectus, a fully terrestrial biped, emerged. We investigated the unusual occurrence of ground-nesting in chimpanzees (Pan troglodytes), which may inform on factors influencing the tree-to-ground sleep transition in the hominin lineage. We used a novel genetic approach to examine ground-nesting in unhabituated chimpanzees at Seringbara in the Nimba Mountains, Guinea. Previous research showed that ground-nesting at Seringbara was not ecologically determined. Here, we tested a possible mate-guarding function of ground-nesting by analyzing DNA from shed hairs collected from ground nests and tree nests found in close proximity. We examined whether or not ground-nesting was a group-level behavioral pattern and whether or not it occurred in more than one community. We used multiple genetic markers to identify sex and to examine variation in mitochondrial DNA control region (HV1, HV2) sequences. Ground-nesting was a male-biased behavior and males constructed more elaborate ("night") nests than simple ("day") nests on the ground. The mate-guarding hypothesis was not supported, as ground and associated tree nests were built either by maternally-related males or possibly by the same individuals. Ground-nesting was widespread and likely habitual in two communities. We suggest that terrestrial nest-building may have already occurred in arboreally-adapted early hominins before the emergence of H. erectus. PMID:22460549

  9. A Grid of NLTE Line-blanketed Model Atmospheres of Early B-Type Stars

    NASA Astrophysics Data System (ADS)

    Lanz, Thierry; Hubeny, Ivan

    2007-03-01

    We have constructed a comprehensive grid of 1540 metal line-blanketed, NLTE, plane-parallel, hydrostatic model atmospheres for the basic parameters appropriate to early B-type stars. The BSTAR2006 grid considers 16 values of effective temperatures, 15,000 K<=Teff<=30,000 K with 1000 K steps, 13 surface gravities, 1.75<=logg<=4.75 with 0.25 dex steps, six chemical compositions, and a microturbulent velocity of 2 km s-1. The lower limit of logg for a given effective temperature is set by an approximate location of the Eddington limit. The selected chemical compositions range from twice to one-tenth of the solar metallicity and metal-free. Additional model atmospheres for B supergiants (logg<=3.0) have been calculated with a higher microturbulent velocity (10 km s-1) and a surface composition that is enriched in helium and nitrogen and depleted in carbon. This new grid complements our earlier OSTAR2002 grid of O-type stars (our Paper I). The paper contains a description of the BSTAR2006 grid and some illustrative examples and comparisons. NLTE ionization fractions, bolometric corrections, radiative accelerations, and effective gravities are obtained over the parameter range covered by the grid. By extrapolating radiative accelerations, we have determined an improved estimate of the Eddington limit in absence of rotation between 55,000 and 15,000 K. The complete BSTAR2006 grid is available at the TLUSTY Web site.

  10. Earth's early atmosphere as seen from carbon and nitrogen isotopic analysis of Archean sediments

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Carr, L. P.; Gilmour, I.; Pillinger, C. T.

    1986-01-01

    The origin and evolution of the Earth's early atmosphere has long been a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of stromatolite deposits (Precambrian Paleobiology Research Group) has extended our knowledge of Archean ecosystems. It has been shown that many stromatolite deposits have undergone negligible alteration since their time of formation. The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archiean sediments and the observation that the 3.3 b.y. old Barberton cherts have remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of the volatile constituents present at their time of formation. Of primary interest to this study was the possibility that the stromatolites and other Archean sediments might retain a vestige of the atmosphere and thus afford an indication of the variations in carbon dioxide and nitrogen isotopic compositions with time. A suite of essentially unaltered Archean stromatolites and the cherts of different ages and geologic sites have been analyzed for their trapped carbon dioxide and nitrogen compositions by the stepped combustion extraction tech nique utilizing static mass spectrometers for the isotope measurements.

  11. Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution

    NASA Technical Reports Server (NTRS)

    Catling, David C.

    2004-01-01

    This project was to investigate models for aqueous sedimentation on early Mars from fluid evaporation. Results focused on three specific areas: (1) First, a fluid evaporation model incorporating iron minerals was developed to compute the evaporation of a likely solution on early Mars derived from the weathering of mafic rock. (2) Second, the fluid evaporation model was applied to salts within Martian meteorites, specifically salts in the nakhlites and ALH84001. Evaporation models were found to be consistent with the mineralogy of salt assemblages-anhydrite, gypsum, Fe-Mg-Ca carbonates, halite, clays-- and the concentric chemical fractionation of Ca-to Mg-rich carbonate rosettes in ALH84001. We made progress in further developing our models of fluid concentration by contributing to updating the FREZCHEM model. (3) Third, theoretical investigation was done to determine the thermodynamics and kinetics involved in the formation of gray, crystalline hematite. This mineral, of probable ancient aqueous origin, has been observed in several areas on the surface of Mars by the Thermal Emission Spectrometer on Mars Global Surveyor. The "Opportunity" Mars Exploration Rover has also detected gray hematite at its landing site in Meridiani Planum. We investigated how gray hematite can be formed via atmospheric oxidation, aqueous precipitation and subsequent diagenesis, or hydrothermal processes. We also studied the geomorphology of the Aram Chaos hematite region using Mars Orbiter Camera (MOC) images.

  12. A simplified model for calculating atmospheric radionuclide transport and early health effects from nuclear reactor accidents

    SciTech Connect

    Madni, I.K.; Cazzoli, E.G.; Khatib-Rahbar, M.

    1995-11-01

    During certain hypothetical severe accidents in a nuclear power plant, radionuclides could be released to the environment as a plume. Prediction of the atmospheric dispersion and transport of these radionuclides is important for assessment of the risk to the public from such accidents. A simplified PC-based model was developed that predicts time-integrated air concentration of each radionuclide at any location from release as a function of time integrated source strength using the Gaussian plume model. The solution procedure involves direct analytic integration of air concentration equations over time and position, using simplified meteorology. The formulation allows for dry and wet deposition, radioactive decay and daughter buildup, reactor building wake effects, the inversion lid effect, plume rise due to buoyancy or momentum, release duration, and grass height. Based on air and ground concentrations of the radionuclides, the early dose to an individual is calculated via cloudshine, groundshine, and inhalation. The model also calculates early health effects based on the doses. This paper presents aspects of the model that would be of interest to the prediction of environmental flows and their public consequences.

  13. Feldspar palaeo-isochrons from early Archaean TTGs: Pb-isotope evidence for a high U/Pb terrestrial Hadean crust

    NASA Astrophysics Data System (ADS)

    Kamber, B. S.; Whitehouse, M. J.; Moorbath, S.; Collerson, K. D.

    2001-12-01

    Feldspar lead-isotope data for 22 early Archaean (3.80-3.82 Ga) tonalitic gneisses from an area south of the Isua greenstone belt (IGB),West Greenland, define a steep linear trend in common Pb-isotope space with an apparent age of 4480+/-77 Ma. Feldspars from interleaved amphibolites yield a similar array corresponding to a date of 4455+/-540 Ma. These regression lines are palaeo-isochrons that formed during feldspar-whole rock Pb-isotope homogenisation a long time (1.8 Ga) after rock formation but confirm the extreme antiquity (3.81 Ga) of the gneissic protoliths [1; this study]. Unlike their whole-rock counterparts, feldspar palaeo-isochrons are immune to rotational effects caused by the vagaries of U/Pb fractionation. Hence, comparison of their intercept with mantle Pb-isotope evolution models yields meaningful information regarding the source history of the magmatic precursors. The locus of intersection between the palaeo-isochrons and terrestrial mantle Pb-isotope evolution lines shows that the gneissic precursors of these 3.81 Ga gneisses were derived from a source with a substantially higher time-integrated U/Pb ratio than the mantle. Similar requirements for a high U/Pb source have been found for IGB BIF [2], IGB carbonate [3], and particularly IGB galenas [4]. Significantly, a single high U/Pb source that separated from the MORB-source mantle at ca. 4.3 Ga with a 238U/204Pb of ca. 10.5 provides a good fit to all these observations. In contrast to many previous models based on Nd and Hf-isotope evidence we propose that this reservoir was not a mantle source but the Hadean basaltic crust which, in the absence of an operating subduction process, encased the early Earth. Differentiation of the early high U/Pb basaltic crust could have occurred in response to gravitational sinking of cold mantle material or meteorite impact, and produced zircon-bearing magmatic rocks. The subchondritic Hf-isotope ratios of ca. 3.8 Ga zircons support this model [5] provided that the redetermined 176Lu decay constant of Scherer et al. [6] is correct. Our model of a stable basaltic Hadean shell for the pre-plate tectonic era explicitly refutes operation of processes such as sediment recycling or melting of hydrated material in subduction zones as far back as 4.4 Ga (as recently suggested by [7]; and [8]). Instead, we propose that initiation of terrestrial subduction occurred at ca. 3.75 Ga, at which stage most of the Hadean basaltic shell (and its differentiation products) was recycled into the mantle, because of the lack of a stabilising mantle lithosphere. We further argue that >3.75 Ga terrestrial rocks and minerals were not preserved by chance, but because of creation of a lithospheric mantle keel concommitant with intrusion of voluminous granitoids immediately after establishment of global subduction. In other words, the only portions of >3.75 Ga crust (basaltic and otherwise) that survived were those that were involved in voluminous arc magmatism along the earliest subduction zones. [1] Nutman A.P. et al. (1999). Contr. Min. Pet. 137, 364. [2] Moorbath S. et al. (1973). Nature 245, 138. [3] Kamber B. S. et al.. (2001). Geol. Soc. London, Spec. Publ. 190, 177. [4] Frei R. & Rosing M. T. (in press). Chem. Geol. [5] Amelin Y. et al. (2000). GCA 64, 4205. [6] Scherer E. et al (2001) Science 293, 683. [7] Wilde S. A. et al.(2001). Nature 409, 175. [8] Mojzsis S. J. (2001). Nature 409, 178.

  14. XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape

    PubMed Central

    Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel; Hanslmeier, Arnold

    2013-01-01

    Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s−1 to ∼5.3×1030 s−1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to <3 EOH and usually is several times smaller in comparison to the thermal atmospheric escape rates. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1030–1048. PMID:24283926

  15. Filling-in of Far-Red and Near-Infrared Solar Lines by Terrestrial and Atmospheric Effects: Simulations and Space-Based Observations from SCHIAMACHY and GOSAT

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Middleton, E. M.; Campbell, P. K. E.; Kuze, A.; Corp, L. A.

    2012-01-01

    Mapping of terrestrial vegetation fluorescence from space is of interest because it can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Space-based measurement of solar-induced chlorophyll fluorescence is challenging, because its signal is small as compared with the much larger reflectance signal. Ground- and aircraft-based approaches have made use of the dark and spectrally-wide 02-A (approx 760 nm) and O2-B (approx 690 nm) atmospheric features to detect the weak fluorescence signal. More recently, Joiner et a1. and Frankenberg et a1. focused on longer-wavelength solar Fraunhofer lines that can be observed with space-based instruments such as the currently operational GOSAT. They showed that fluorescence can be detected using Fraunhofer lines away from the far-red chlorophyll-a fluorescence peak even when the surface is relatively bright. Here, we build on that work by developing methodology to correct for instrumental artifacts that produce false filling-in signals that can bias fluorescence retrievals. We also examine other potential sources of filling-in at far-red and NIR wavelengths. Another objective is to explore the possibility of making fluorescence measurements from space with lower spectral resolution instrumentation than the GOSAT interferometer. We focus on the 866 nm Ca II solar Fraunhofer line. Very few laboratory and ground-based measurements of vegetation fluorescence have been reported at wavelengths longer than 800 mn. Some results of fluorescence measurements of corn leaves acquired in the laboratory using polychromatic excitation at wavelengths shorter than 665 nm show that at 866 nm, the measured signal is of the order of 0.1-0.2 mw/sq m/nm/sr. In this work we use the following satellite observations: We use SCIAMACHY channel 5 in nadir mode that covers wavelengths between 773 and 1063 nm at a spectral resolution of 0.54 nm. GOSAT has two instrument packages: the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) and the Cloud and Aerosol Imager (CAI). We use TANSO-FTS band 1, which extends from approximately 758 to 775 mn and we use cloud fraction derived from the CAL We compare satellite-derived fluorescence with the Enhanced Vegetation Index (EVI), an Aqua/MODIS-derived vegetation reflectance-based index that indicates relative greenness and is used to infer photosynthetic function.

  16. Filling-in of Far-Red and Near-Infrared Solar Lines by Terrestrial and Atmospheric Effects: Simulations and Space-Based Observations from SCIAMACHY and GOSAT

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Middleton, E. M.; Campbell, P. K. E.; Yoshida, Y.; Kuse, A.; Corp, L. A.

    2012-01-01

    Mapping of terrestrial vegetation fluorescence from space is of interest because it can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Space-based measurement of solar-induced chlorophyll fluorescence is challenging, because its signal is small as compared with the much larger reflectance signal. Ground- and aircraft-based approaches have made use of the dark and spectrally-wide O2-A ( approx 760 nm) and O2-B (approx 690 nm) atmospheric features to detect the weak fluorescence signal. More recently, Joiner et al. and Frankenberg et al. focused on longer-wavelength solar Fraunhofer lines that can be observed with space-based instruments such as the currently operational GOSAT. They showed that fluorescence can be detected using Fraunhofer lines away from the far-red chlorophyll-a fluorescence peak even when the surface is relatively bright. Here, we build on that work by developing methodology to correct for instrumental artifacts that produce false filling-in signals that can bias fluorescence retrievals. We also examine other potential sources of filling-in at far-red and NIR wavelengths. Another objective is to explore the possibility of making fluorescence measurements from space with lower spectral resolution instrumentation than the GOSAT interferometer. We focus on the 866nm Ca II solar Fraunhofer line. Very few laboratory and ground-based measurements of vegetation fluorescence have been reported at wavelengths longer than 800 nm. Some results of fluorescence measurements of corn leaves acquired in the laboratory using polychromatic excitation at wavelengths shorter than 665nm show that at 866 nm, the measured signal is of the order of 0.1-0.2 mW/sq m/nm/sr. In this work, we use the following satellite observations: We use SCIAMACHY channel 5 in nadir mode that covers wavelengths between 773 and 1063nm at a spectral resolution of 0.54 nm. GOSAT has two instrument packages: the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) and the Cloud and Aerosol Imager (CAI). We use TANSO-FTS band 1, which extends from approximately 758 to 775nm and we use cloud fraction derived from the CAI. We compare satellite-derived fluorescence with the Enhanced Vegetation Index (EVI), an Aqua/MODIS-derived vegetation reflectance-based index that indicates relative greenness and is used to infer photosynthetic function.

  17. Speciation and solubility of reduced C-O-H-N volatiles in mafic melt: Implications for volcanism, atmospheric evolution, and deep volatile cycles in the terrestrial planets

    NASA Astrophysics Data System (ADS)

    Armstrong, Lora S.; Hirschmann, Marc M.; Stanley, Ben D.; Falksen, Emily G.; Jacobsen, Steven D.

    2015-12-01

    Using vibrational spectroscopy and SIMS, we determined the solubility and speciation of C-O-H-N dissolved volatiles in mafic glasses quenched from high pressure under reduced conditions, with fO2 from -3.65 to +1.46 relative to the iron-wüstite buffer (IW). Experiments were performed on martian and terrestrial basalts at 1.2 GPa and 1400 °C in graphite containers with variable availability of H2O, and in the presence of FePt alloys or Fe-C liquids. The dominant C-O-H-N species varies systematically with fO2 and H2O content: the carbonate ion prevails above IW + 1, but for dry conditions between IW-2 and IW + 1, Ctbnd O species are most important. Below IW, reduced NH-bearing species are present. At the most reducing and hydrous (∼0.5 wt% H2O) conditions, small amounts of CH4 are present. Concentrations of C diminish as conditions become more reduced, amounting to 10 s to ∼100 ppm in the interval ∼IW-2 to IW + 1 where Ctbnd O species dominate, and as little as 1-3 ppm at more reduced conditions. Concentrations of non-carbonate carbon, dominated by Ctbnd O species, correlate with CO fugacities along a trend implying that the species stoichiometry has just one Ctbnd O group and suggesting that carbonyl complexes (transition metals with multiple carbon monoxide ligands) are not important species under these conditions. C partition coefficients between Fe-C liquid and silicate melt increase with decreasing fO2 , becoming as great as 104 for the most reducing conditions investigated. The low solubility of C in silicate liquids under reducing conditions means that most C during the magma ocean stage of planetary differentiation is either segregated to the core or in the overlying atmosphere. Precipitation of C-rich phases in a carbon-saturated magma ocean is also possible, and is one mechanism by which some C can be retained in the mantle of a planet. The predominant magmatic carbonaceous species for both martian and lunar volcanism is likely Ctbnd O.

  18. Differential Expression of Metallothionein Isoforms in Terrestrial Snail Embryos Reflects Early Life Stage Adaptation to Metal Stress

    PubMed Central

    Baurand, Pierre-Emmanuel; Pedrini-Martha, Veronika; de Vaufleury, Annette; Niederwanger, Michael; Capelli, Nicolas; Scheifler, Renaud; Dallinger, Reinhard

    2015-01-01

    The aim of this study was to analyze the expression of three metallothionein (MT) isoform genes (CdMT, CuMT and Cd/CuMT), already known from adults, in the Early Life Stage (ELS) of Cantareus aspersus. This was accomplished by detection of the MT isoform-specific transcription adopting Polymerase Chain Reaction (PCR) amplification and quantitative Real Time (qRT)-PCR of the three MT genes. Freshly laid eggs were kept for 24 hours under control conditions or exposed to three cadmium (Cd) solutions of increasing concentration (5, 10, and 15 mg Cd/L). The transcription of the three MT isoform genes was detected via PCR in 1, 6 and 12-day-old control or Cd-exposed embryos. Moreover, the transcription of this isoform genes during development was followed by qRT-PCR in 6 and 12-day-old embryos. Our results showed that the CdMT and Cd/CuMT genes, but not the CuMT gene, are expressed in embryos at the first day of development. The transcription of the 3 MT genes in control embryos increased with development time, suggesting that the capacities of metal regulation and detoxification may have gradually increased throughout embryogenesis. However in control embryos, the most highly expressed MT gene was that of the Cd/CuMT isoform, whose transcription levels greatly exceeded those of the other two MT genes. This contrasts with the minor significance of this gene in adult snails and suggests that in embryos, this isoform may play a comparatively more important role in metal physiology compared to adult individuals. This function in adult snails appears not to be related to Cd detoxification. Instead, snail embryos responded to Cd exposure by over-expression of the CdMT gene in a concentration-dependent manner, whereas the expression of the Cd/CuMT gene remained unaffected. Moreover, our study demonstrates the ability of snail embryos to respond very early to Cd exposure by up-regulation of the CdMT gene. PMID:25706953

  19. On the early processing of terrestrial organic matter released to (sub-)Arctic coastal waters as deduced from biomarkers, isotopes and a simple model

    NASA Astrophysics Data System (ADS)

    Gustafsson, Örjan; Vonk, Jorien; van Dongen, Bart; Dudarev, Oleg; Semiletov, Igor

    2010-05-01

    The surface layer of the vast sub-Arctic and Arctic tundra and taiga holds over a third of the global soil carbon and this area is now experiencing among the largest climate warming of anywhere on Earth. Yet, there is a shortage of investigations of the biogeochemical fate of coastally exported terrestrial organic matter (terrOM) from these systems, in part due to the inaccessibility of the large Eurasian-Arctic shelves. This paper seeks to synthesize initial findings from a large-scale survey of single surface sediments outside the five Great Russian Arctic Rivers (GRARs; Ob,Yenisey, Lena, Kolyma and Indigirka) and from detailed process-studies of a water column and surface sediment transect off pristine sub-Arctic Kalix River, one of the largest unregulated rivers in Europe draining into the northernmost Baltic Sea. There is at present a discrepancy in the literature of how the early (water column) fate of terrestrial organic matter is believed to occur between the northern Baltic Sea and the Eurasian Arctic shelf seas. For the Baltic, one suggests substantial DOC degradation but no consideration of POC degradation. For the Arctic, terrestrial DOC is believed to be conservatively mixed while POC is assumed to follow a generic "global" average degradation. Our studies to date show that terrOM entering sub-Arctic Baltic and Eurasian-Arctic seas follows continent-scale trends in molecular and isotopic composition. Sphagnum is a key contributor to the pre-aged (1000s of 14C years) terrOM in these coastal waters with greatest Sphagnum contribution but youngest terrOM toward the west. The Kalix-Baltic transect revealed rapid degradation of acyl lipids along the 80 km distance from river mouth to the open bay. For instance, the ratio of HMW n-alkanoic acids to HMW n-alkanes in surface water suspended particles dropped from 2.7 to 1.2. There was also rapid degradation during settling and in the surface sediment as the same ratio in sediments dropped between the estuary - open bay from 1.5 to 0.2. A simple box model was parameterized with measurements of advective river input, settling fluxes and advective export and solved for degradation. The model was run for both individual biomarkers, bulk POC and bulk DOC. Rapid terrPOC degradation was constrained (65% during 5-day box transit). This translated into a degradation rate for terrPOC that is nearly 20 times more rapid as for terrDOC, which makes both pools roughly equally important for the total terrOM degradation. Similar trends for POC-biomarkers and degradation indexes between the Kalix-Baltic and GRAR systems suggest that the early processing may be similar on the Eurasian Arctic shelf.

  20. On the early processing of terrestrial organic matter released to (sub-)Arctic coastal waters as deduced from biomarkers, isotopes and a simple model

    NASA Astrophysics Data System (ADS)

    Gustafsson, Ö.; Vonk, J.; van Dongen, B.; Dudarev, O.; Semiletov, I.

    2009-04-01

    The surface layer of the vast sub-Arctic and Arctic tundra and taiga holds over a third of the global soil carbon and this area is now experiencing among the largest climate warming of anywhere on Earth. Yet, there is a shortage of investigations of the biogeochemical fate of coastally exported terrestrial organic matter (terrOM) from these systems, in part due to the inaccessibility of the large Eurasian-Arctic shelves. This paper seeks to synthesize initial findings from a large-scale survey of single surface sediments outside the five Great Russian Arctic Rivers (GRARs; Ob,Yenisey, Lena, Kolyma and Indigirka) and from detailed process-studies of a water column and surface sediment transect off pristine sub-Arctic Kalix River, one of the largest unregulated rivers in Europe draining into the northernmost Baltic Sea. There is at present a discrepancy in the literature of how the early (water column) fate of terrestrial organic matter is believed to occur between the northern Baltic Sea and the Eurasian Arctic shelf seas. For the Baltic, one suggests substantial DOC degradation but no consideration of POC degradation. For the Arctic, terrestrial DOC is believed to be conservatively mixed while POC is assumed to follow a "global" average degradation. Our studies to date show that terrOM entering sub-Arctic Baltic and Eurasian-Arctic seas follows continent-scale trends in molecular and isotopic composition. Sphagnum is a key contributor to the pre-aged (1000s of 14C years) terrOM in these coastal waters with greatest Sphagnum contribution but youngest terrOM toward the west. The Kalix-Baltic transect revealed rapid degradation of acyl lipids along the 80 km distance from river mouth to the open bay. For instance, the ratio of HMW n-alkanoic acids to HMW n-alkanes in surface water suspended particles dropped from 2.7 to 1.2. There was also rapid degradation during settling and in the surface sediment as the same ratio in sediments dropped between the estuary - open bay from 1.5 to 0.2. A simple box model was parameterized with measurements of advective river input, settling fluxes and advective export and solved for degradation. The model was run for both individual biomarkers, bulk POC and bulk DOC. Rapid terrPOC degradation was constrained (65% during 5-day box transit). This translated into a degradation rate for terrPOC that is nearly 20 times more rapid as for terrDOC, which makes both pools equally important for the total terrOM degradation. Similar trends for POC-biomarkers and degradation indexes between the Kalix-Baltic and GRAR systems suggest that the early processing may be similar on the Eurasian Arctic shelf.

  1. Satellite derived 30-year trends in terrestrial frozen and non-frozen seasons and associated impacts to vegetation and atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Kimball, J. S.; McDonald, K. C.; Glassy, J. M.

    2010-12-01

    Approximately 66 million km2 (52.5 %) of the global vegetated land area experiences seasonally frozen temperatures as a major constraint to ecosystem processes. The freeze-thaw (F/T) status of the landscape as derived from satellite microwave remote sensing is closely linked to surface energy budget and hydrological activity, vegetation phenology, terrestrial carbon budgets and land-atmosphere trace gas exchange. We utilized a seasonal threshold algorithm based temporal change classification of 37GHz frequency, vertically polarized brightness temperatures (Tb) from the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) pathfinder and Special Sensor Microwave Imager (SSM/I) to classify daily F/T status for all global land areas where seasonal frozen temperatures are a major constraint to ecosystem processes. A temporally consistent, long-term (30 year) daily F/T record was created by pixel-wise correction of the SMMR Tb record based on empirical analyses of overlapping SMMR and SSM/I measurements acquired during 1987. The resulting combined F/T record was validated against in situ temperature measurements from the global weather station network and applied to quantify regional patterns and trends in timing and length of frozen and non-frozen seasons. The F/T results were compared against other surrogate measures of biosphere activity including satellite AVHRR (GIMMS) based vegetation greenness (NDVI) and atmospheric CO2 concentrations over northern (>50N) land areas. The resulting F/T record showed mean annual classification accuracies of 91 (+/-1.0) and 84 (+/- 0.9) percent for PM and AM overpass retrievals relative to in situ weather station records. The F/T record showed significant (P=0.008) long-term trends in non-frozen period (0.207 days/yr) that were largely driven by earlier onset of spring thaw (-0.121 days/yr) and a small, delayed trend the arrival of the frozen period (0.107 days/yr). These results coincide with 0.025 C/yr warming trends in surface air temperatures for the domain as derived from global model reanalysis. The F/T results explain much (64.5%, P<0.001) of the mean temporal variability in the timing of CO2 drawdown by vegetation photosynthesis in spring over northern land areas. The F/T results also correspond significantly with NDVI temporal anomalies. However, correspondence between non-frozen period and NDVI is weaker after 2000 relative to earlier decades due to recent increases in the extent and severity of drought and associated water balance limitations to productivity. This work was performed at the University of Montana and the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration.

  2. Insights into the early Eocene hydrological cycle from an ensemble of atmosphere-ocean GCM simulations

    NASA Astrophysics Data System (ADS)

    Carmichael, M. J.; Lunt, D. J.; Huber, M.; Heinemann, M.; Kiehl, J.; LeGrande, A.; Loptson, C. A.; Roberts, C. D.; Sagoo, N.; Shields, C.; Valdes, P. J.; Winguth, A.; Winguth, C.; Pancost, R. D.

    2015-07-01

    Recent studies, utilising a range of proxies, indicate that a significant perturbation to global hydrology occurred at the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma). An enhanced hydrological cycle for the warm early Eocene is also suggested to have played a key role in maintaining high-latitude warmth during this interval. However, comparisons of proxy data to General Circulation Model (GCM) simulated hydrology are limited and inter-model variability remains poorly characterised, despite significant differences in simulated surface temperatures. In this work, we undertake an intercomparison of GCM-derived precipitation and P-E distributions within the EoMIP ensemble (Lunt et al., 2012), which includes previously-published early Eocene simulations performed using five GCMs differing in boundary conditions, model structure and precipitation relevant parameterisation schemes. We show that an intensified hydrological cycle, manifested in enhanced global precipitation and evaporation rates, is simulated for all Eocene simulations relative to preindustrial. This is primarily due to elevated atmospheric paleo-CO2, although the effects of differences in paleogeography/ice sheets are also of importance in some models. For a given CO2 level, globally-averaged precipitation rates vary widely between models, largely arising from different simulated surface air temperatures. Models with a similar global sensitivity of precipitation rate to temperature (dP/dT) display different regional precipitation responses for a given temperature change. Regions that are particularly sensitive to model choice include the South Pacific, tropical Africa and the Peri-Tethys, which may represent targets for future proxy acquisition. A comparison of early and middle Eocene leaf-fossil-derived precipitation estimates with the GCM output illustrates that a number of GCMs underestimate precipitation rates at high latitudes. Models which warm these regions, either via elevated CO2 or by varying poorly constrained model parameter values, are most successful in simulating a match with geologic data. Further data from low-latitude regions and better constraints on early Eocene CO2 are now required to discriminate between these model simulations given the large error bars on paleoprecipitation estimates. Given the clear differences apparent between simulated precipitation distributions within the ensemble, our results suggest that paleohydrological data offer an independent means by which to evaluate model skill for warm climates.

  3. Insights into the early Eocene hydrological cycle from an ensemble of atmosphere-ocean GCM simulations

    NASA Astrophysics Data System (ADS)

    Carmichael, Matthew; Lunt, Daniel; Pancost, Richard

    2015-04-01

    Recent studies utilising a range of geochemical proxies have indicated that a significant perturbation to global hydrology occurred at the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma). An enhanced hydrological cycle for the warm early Eocene is also suggested to have played a key role in maintaining high-latitude warmth during this interval. Comparisons of proxy data to General Circulation Model (GCM) simulated hydrology have not widely been made however, and inter-model variability remains poorly characterised despite significant differences in simulated surface temperatures. In this work, we address this by undertaking an intercomparison of GCM-derived precipitation distributions within the EoMIP ensemble (Lunt et al., 2012), which includes previously-published early Eocene simulations performed using five GCMs differing in boundary conditions, model structure and precipitation-relevant parameterisation schemes. We show that an intensified hydrological cycle is simulated for all Eocene simulations relative to preindustrial. This is primarily due to elevated atmospheric paleo-CO2, although the effects of differences in paleogeography/ice sheets are also of importance in some models. For a given CO2 level, globally-averaged precipitation rates vary widely between models, largely as a result of different climate sensitivities (dT/dCO2) and differing parameterisation schemes. Despite this, models with similar global precipitation sensitivities (dP/dT) display different regional responses for a given temperature change. Regions which are particularly model sensitive include the South Pacific, tropical Africa and the Tethys and may represent targets for future proxy acquisition. A comparison of leaf-fossil-derived precipitation estimates with GCM data illustrates that models tend to unanimously underestimate early Eocene precipitation rates at high latitudes. Models which warm these regions via elevated CO2 or by utilising alternative parameterisations are most successful in simulating a match with geologic data. Further data from low-latitude regions and better constraints on early Eocene CO2 are required to discriminate between these model simulations, given the large error bars on paleoprecipitation estimates. Given the clear differences apparent between simulated precipitation distributions within the ensemble, further interrogation of paleohydrological data may offer an independent means by which to evaluate model skill for warm climates.

  4. Variability in frozen and thawed seasons in the terrestrial high latitudes and relationships with land-atmosphere CO2 exchange: Characterization with spaceborne microwave remote sensing

    NASA Astrophysics Data System (ADS)

    McDonald, K. C.; Kimball, J. S.

    2006-12-01

    Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These relatively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw and autumn freeze timing are derived using daily brightness temperature measurements from the Special Sensor Microwave Imager (SSM/I), the Advanced Microwave Scanning Radiometer on EOS (AMSR-E), and the SeaWinds-on-QuikSCAT scatterometer. We examine relationships between freeze/thaw timing as related to sensor, satellite overpass time, and landcover, and in relation to regional biospheric activity indicated by atmospheric CO2 measurements. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North America and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to seasonal atmospheric CO2 concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Classification differences between AM and PM overpass data average approximately 5 days for the region, though both appear to be effective surrogates for monitoring annual growing seasons at high latitudes. Timing of the primary spring thaw event determined from early evening acquisitions generally precedes that determined from early morning data acquisitions for arctic tundra and boreal forest landscapes. Grasslands in the southern margins of the pan-Arctic watershed show opposite patterns for active and passive sensors. This difference in day/night thaw timing observed by radars vs. radiometers may arise from differences in the influence of vegetation on the surface energy budget across biomes. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and at the University of Montana, Missoula, under contract to the National Aeronautics and Space Administration.

  5. Mercury cycling in terrestrial watersheds

    USGS Publications Warehouse

    Shanley, James B.; Bishop, Kevin

    2012-01-01

    This chapter discusses mercury cycling in the terrestrial landscape, including inputs from the atmosphere, accumulation in soils and vegetation, outputs in streamflow and volatilization, and effects of land disturbance. Mercury mobility in the terrestrial landscape is strongly controlled by organic matter. About 90% of the atmospheric mercury input is retained in vegetation and organic matter in soils, causing a buildup of legacy mercury. Some mercury is volatilized back to the atmosphere, but most export of mercury from watersheds occurs by streamflow. Stream mercury export is episodic, in association with dissolved and particulate organic carbon, as stormflow and snowmelt flush organic-rich shallow soil horizons. The terrestrial landscape is thus a major source of mercury to downstream aquatic environments, where mercury is methylated and enters the aquatic food web. With ample organic matter and sulfur, methylmercury forms in uplands as well—in wetlands, riparian zones, and other anoxic sites. Watershed features (topography, land cover type, and soil drainage class) are often more important than atmospheric mercury deposition in controlling the amount of stream mercury and methylmercury export. While reductions in atmospheric mercury deposition may rapidly benefit lakes, the terrestrial landscape will respond only over decades, because of the large stock and slow turnover of legacy mercury. We conclude with a discussion of future scenarios and the challenge of managing terrestrial mercury.

  6. Paleoclimatic and paleoecological reconstruction of early Miocene terrestrial equatorial deposits, Rusinga and Mfangano Islands, Lake Victoria, Kenya

    NASA Astrophysics Data System (ADS)

    Michel, L. A.; Peppe, D. J.; McNulty, K. P.; Driese, S. G.; Lutz, J.; Nightingale, S.; Maxbauer, D. P.; Horner, W. H.; DiPietro, L. M.; Lehmann, T.; Dunsworth, H. M.; Harcourt-Smith, W. E.; Ogondo, J.

    2012-12-01

    Biological responses to climatic shifts are often studied to inform us on future anthropogenic-driven climate change. However, few of these climatic shifts occur over time scales appropriate to modern change and few occur with biota similar to modern. The Miocene Climatic Optimum is an ideal interval to study because of its rapid duration and because it occurred during the rise and proliferation of apes. The sediments on Rusinga and Mfangano Islands, Lake Victoria, Kenya were deposited between 18 and 20 Ma and record a changing equatorial climate just prior to the Miocene Climate Optimum. This location also offers an opportunity to use multiple proxies to constrain climate and landscape, including paleosol geochemistry, paleobotany and paleontology. Additionally, due to the rich fossil preservation on the islands, climatic shifts are framed within the context of early caterrhine evolution. Here, we report a climate shift recorded through three time slices spanning two formations over ~2 myr. The oldest unit, the Wayando Formation, records an arid, probably open ecosystem with pedogenic calcite rhizoliths, a high groundwater table, poorly-formed paleosols and permineralized sedges. The middle time slice, the Grit Member-Fossil Bed Member contact of the Hiwegi Formation, shows evidence of a local saline lake, with desiccation features, satin-spar after gypsum deposits and salt hoppers. Paleobotanical and sedimentological data from roughly contemporaneous strata indicate a warm, highly seasonal environment that supported a mixture of woodland and forested elements across the landscape. The youngest unit, which is within the Kibanga Member of the Hiwegi Formation, displays demonstrable evidence for a closed-canopy multistoried forest with the presence of tree-stump casts and permineralized root systems within a red-brown paleosol. Within the same paleosol horizon, the dental remains of the catarrhines Proconsul and Dendropithecus have been discovered in situ. This stratum is overlain by a sandstone with preserved leaves. Bulk soil geochemistry and paleobotanical proxies suggest the climate was warm (MAT estimates range = 22.6 - 34.5 °C) and relatively wet (MAP estimates range = 700 - 2,620 mm). This study suggests that tropical Africa may have had a much more dynamic climate leading up to the Miocene Climatic Optimum than previously suggested, and underwent considerable ecosystem reorganization both before and after the Miocene Climatic Optimum.

  7. Terrestrial multi-proxy late Miocene to early Pliocene climate reconstruction of Cook Inlet forearc basin, southern Alaska

    NASA Astrophysics Data System (ADS)

    Mongrain, J. R.; Wooller, M.; Fowell, S. J.; Mccarthy, P. J.; LePain, D.

    2011-12-01

    Understanding the climate and depositional systems in south-central Alaska during initial uplift of the central and western Alaska Range has been hampered by conflicting climatic interpretations and poor age control regarding the timing of exhumation and uplift. This study focuses on the late Miocene to early Pliocene climate record preserved in fluvial depositional systems that crop out near the margin of Cook Inlet forearc basin, south-central Alaska. These data, along with newly published exhumation and uplift ages for the central and western Alaska Range, provide new insights into the relationship between climate and uplift. Climate reconstructions are based on a multi-proxy approach that includes stable carbon isotopic analyses of residual pollen concentrates from palynological preparations, allowing direct comparisons with palynological data from the same samples. The pollen-derived stable carbon isotope data are supplemented with isotopic analyses of bulk sediment and coal. The palynological assemblages indicate prolonged warm conditions, as thermophilic taxa are consistently present. The exception is the youngest sample, which reveals a marked decrease in thermophilic taxa such as Podocarpus, Pterocarya/Cyclocarya, and Fagus and may record the initial cooling of south-central Alaska during the Pliocene. Pollen frequencies indicate relatively humid conditions over the interval from ~10 Ma to ~6.5 Ma, with the wettest conditions occurring ~8 Ma. The ?13C data are used to estimate mean annual precipitation (MAP), which provides supporting evidence of wet conditions between ~7.5 Ma and ~8.5 Ma. Considerable variability in MAP, ranging from 3600 to 300 mm, suggests that generally wet conditions were interrupted by periods of below average precipitation. Increases in precipitation due to uplift of the central and western Alaska Range and related orographic effects are probably not responsible for increases in MAP, as these events postdate the humid interval by ~ 2 Ma, as does the opening of the Bering Strait. However, evidence for thermal climatic optima from 11.5 to 10.5 and 7.5 to 6.5 Ma in North Pacific marine paleoclimate records are taken to indicate warm sea surface temperatures, which may be responsible for high MAP and persistence of thermophilic genera in Cook Inlet.

  8. A comparison of lyman alpha and He lambda 10830 line structures and variations in early-type star atmospheres

    NASA Technical Reports Server (NTRS)

    Meisel, D. D.

    1974-01-01

    Line profiles were first obtained at maximum velocity separation of the spectroscopic binary Spica (alpha Vir), and then high resolution spectrophotometric images of selected features in the 1.1 micron spectrum of Comet Kohoutek were obtained in order to gain insight into the structures and variations in early-type star atmospheres.

  9. Magnetostratigraphy of the Lowermost Paleocene Fort Union Formation in the Williston Basin of North Dakota: Base of a Terrestrial Reference Section for Early Cenozoic Global Change

    NASA Astrophysics Data System (ADS)

    Peppe, D. J.; Evans, D. D.

    2006-05-01

    Within the North Dakota Little Missouri Badlands, a continuous succession of Cretaceous through lowermost Eocene age sediments exposes a nearly complete terrestrial Paleocene record. Using the K-T boundary as the basal datum, a ca.180 meter composite section of the lowermost Fort Union Formation has been constructed. Paleomagnetic samples that have been analyzed from this section demonstrate a series of geomagnetic reversals that can be correlated from C29r through C28n of the Geomagnetic Polarity Time Scale. Based on these paleomagnetic data, the mean sedimentation rates during the interval from the K-T boundary to the top of 28r are estimated to be ca. 100 m/Myr. These data have allowed us to calibrate the two tongues of the marine Cannonball Member to within C29n and C28r respectively, and identify a major change in the composition and dominant taxa in the megafloral record near the end of C28r. One potential implication of this result, pending further data analysis and correlations to fossil-bearing sections, is the temporal restriction of the Puercan-Torrejonian 1 North American Land Mammal "Ages" (NALMAs) by nearly a factor of two relative to previous estimates (i.e. from ca. 2 Myr to ca. 1 Myr). This would in turn suggest that post-extinction mammal speciation occurred twice as fast as previously supposed. The ultimate aim of this research is to develop a high-precision chronostratigraphic reference section for the Paleocene of the Rocky Mountain Region of North America using lithostratigraphy, magnetostratigraphy, pollen and megafloral biostratigraphy, chemostratigraphy, and chronostratigraphy, that can be used to determine the temporal extent of floral and faunal radiation after the Cretaceous-Paleogene extinctions, and to assess patterns of floral and faunal diversity and composition in response to numerous climatic changes. Furthermore, we hope to use this chronostratigraphic section for comparisons with contemporaneous sections worldwide, which will lead to more accurate and detailed correlations of the terrestrial and marine climate records through the early Cenozoic.

  10. TERRESTRIAL ECOTOXICOLOGY

    EPA Science Inventory

    Terrestrial ecotoxicology is the study of how environmental pollutants affect land-dependent organisms and their environment. It requires three elements: (1) a source, (2) a receptor, and (3) an exposure pathway. This article reviews the basic principles of each of each element...

  11. Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate.

    PubMed

    Anagnostou, Eleni; John, Eleanor H; Edgar, Kirsty M; Foster, Gavin L; Ridgwell, Andy; Inglis, Gordon N; Pancost, Richard D; Lunt, Daniel J; Pearson, Paul N

    2016-05-19

    The Early Eocene Climate Optimum (EECO, which occurred about 51 to 53 million years ago), was the warmest interval of the past 65 million years, with mean annual surface air temperature over ten degrees Celsius warmer than during the pre-industrial period. Subsequent global cooling in the middle and late Eocene epoch, especially at high latitudes, eventually led to continental ice sheet development in Antarctica in the early Oligocene epoch (about 33.6 million years ago). However, existing estimates place atmospheric carbon dioxide (CO2) levels during the Eocene at 500-3,000 parts per million, and in the absence of tighter constraints carbon-climate interactions over this interval remain uncertain. Here we use recent analytical and methodological developments to generate a new high-fidelity record of CO2 concentrations using the boron isotope (δ(11)B) composition of well preserved planktonic foraminifera from the Tanzania Drilling Project, revising previous estimates. Although species-level uncertainties make absolute values difficult to constrain, CO2 concentrations during the EECO were around 1,400 parts per million. The relative decline in CO2 concentration through the Eocene is more robustly constrained at about fifty per cent, with a further decline into the Oligocene. Provided the latitudinal dependency of sea surface temperature change for a given climate forcing in the Eocene was similar to that of the late Quaternary period, this CO2 decline was sufficient to drive the well documented high- and low-latitude cooling that occurred through the Eocene. Once the change in global temperature between the pre-industrial period and the Eocene caused by the action of all known slow feedbacks (apart from those associated with the carbon cycle) is removed, both the EECO and the late Eocene exhibit an equilibrium climate sensitivity relative to the pre-industrial period of 2.1 to 4.6 degrees Celsius per CO2 doubling (66 per cent confidence), which is similar to the canonical range (1.5 to 4.5 degrees Celsius), indicating that a large fraction of the warmth of the early Eocene greenhouse was driven by increased CO2 concentrations, and that climate sensitivity was relatively constant throughout this period. PMID:27111509

  12. Terrestrial Biomarkers for Early Life on Earth as Analogs for Possible Martian Life Forms: Examples of Minerally Replaced Bacteria and Biofilms From the 3.5 - 3.3-Ga Barberton Greenstone Belt, South Africa

    NASA Technical Reports Server (NTRS)

    Westall, F.; McKay, D. S.; Gibson, E. K.; deWit, M. J.; Dann, J.; Gerneke, D.; deRonde, C. E. J.

    1998-01-01

    The search for extraterrestrial life and especially martian life hinges on a variety of methods used to identify vestiges of what we could recognize as life, including chemical signatures, morphological fossils, and biogenic precipitates. Although the possibility of extant life on Mars (subsurface) is being considered, most exploration efforts may be directed toward the search for fossil life. Geomorphological evidence points to a warmer and wetter Mars early on in its history, a scenario that encourages comparison with the early Earth. For this reason, study of the early terrestrial life forms and environment in which they lived may provide clues as to how to search for extinct martian life. As a contribution to the early Archean database of terrestrial microfossils, we present new data on morphological fossils from the 3.5-3.3-Ga Barberton greenstone belt (BGB), South Africa. This study underlines the variety of fossil types already present in some of the oldest, best-preserved terrestrial sediments, ranging from minerally replaced bacteria and bacteria molds of vaRious morphologies (coccoid, coccobacillus, bacillus) to minerally replaced biofilm. Biofilm or extracellular polymeric substance (EPS) is produced by bacteria and appears to be more readily fossilisable than bacteria themselves. The BGB fossils occur in shallow water to subaerial sediments interbedded with volcanic lavas, the whole being deposited on oceanic crust. Penecontemporaneous silicification of sediments and volcanics resulted in the chertification of the rocks, which were later subjected to low-grade metamorphism (lower greenschist).

  13. Evidence for a (15)N positive excursion in terrestrial foodwebs at the Middle to Upper Palaeolithic transition in south-western France: Implications for early modern human palaeodiet and palaeoenvironment.

    PubMed

    Bocherens, Hervé; Drucker, Dorothée G; Madelaine, Stéphane

    2014-04-01

    The Middle to Upper Palaeolithic transition around 35,000 years ago coincides with the replacement of Neanderthals by anatomically modern humans in Europe. Several hypotheses have been suggested to explain this replacement, one of them being the ability of anatomically modern humans to broaden their dietary spectrum beyond the large ungulate prey that Neanderthals consumed exclusively. This scenario is notably based on higher nitrogen-15 amounts in early Upper Palaeolithic anatomically modern human bone collagen compared with late Neanderthals. In this paper, we document a clear increase of nitrogen-15 in bone collagen of terrestrial herbivores during the early Aurignacian associated with anatomically modern humans compared with the stratigraphically older Châtelperronian and late Mousterian fauna associated with Neanderthals. Carnivores such as wolves also exhibit a significant increase in nitrogen-15, which is similar to that documented for early anatomically modern humans compared with Neanderthals in Europe. A shift in nitrogen-15 at the base of the terrestrial foodweb is responsible for such a pattern, with a preserved foodweb structure before and after the Middle to Upper Palaeolithic transition in south-western France. Such an isotopic shift in the terrestrial ecosystem may be due to an increase in aridity during the time of deposition of the early Aurignacian layers. If it occurred across Europe, such a shift in nitrogen-15 in terrestrial foodwebs would be enough to explain the observed isotopic trend between late Neanderthals and early anatomically modern humans, without any significant change in the diet composition at the Middle to Upper Palaeolithic transition. PMID:24630359

  14. Evolution of ore deposits on terrestrial planets

    NASA Astrophysics Data System (ADS)

    Burns, R. G.

    Ore deposits on terrestrial planets materialized after core formation, mantle evolution, crustal development, interactions of surface rocks with the hydrosphere and atmosphere, and, where life exists on a planet, the involvement of biological activity. Core formation removed most of the siderophilic and chalcophilic elements, leaving mantles depleted in many of the strategic and noble metals relative to their chondritic abundances. Basaltic magma derived from partial melting of the mantle transported to the surface several metals contained in immiscible silicate and sulfide melts. Magmatic ore deposits were formed during cooling, fractional crystallization and density stratification from the basaltic melts. Such ore deposits found in earth's Archean rocks were probably generated during early histories of all terrestrial planets and may be the only types of igneous ores on Mars. Where plate tectonic activity was prevalent on a terrestrial planet, temporal evolution of ore deposits took place. Repetitive episodes of subduction modified the chemical compositions of the crust and upper mantles, leading to porphyry copper and molybdenum ores in calc-alkaline igneous rocks and granite-hosted tin and tungsten deposits. Such plate tectonic-induced mineralization in relatively young igneous rocks on earth may also have produced hydrothermal ore deposits on Venus in addition to the massive sulfide and cumulate chromite ores associated with Venusian mafic igneous rock. Sedimentary ore deposits resulting from mechanical and chemical weathering in reducing atmospheres in Archean earth included placer deposits (e.g., uraninite, gold, pyrite ores). Chromite, ilmenite, and other dense unreactive minerals could also be present on channel floors and in valley networks on Mars, while banded iron formations might underlie the Martian northern plains regions. As oxygen evolved in earth's atmosphere, so too did oxide ores. By analogy, gossans above sulfide ores probably occur on Mars, but not submarine ferromanganese nodules and crusts which have precipitated in oxygenated seawater on earth.

  15. Evolution of ore deposits on terrestrial planets

    NASA Technical Reports Server (NTRS)

    Burns, R. G.

    1991-01-01

    Ore deposits on terrestrial planets materialized after core formation, mantle evolution, crustal development, interactions of surface rocks with the hydrosphere and atmosphere, and, where life exists on a planet, the involvement of biological activity. Core formation removed most of the siderophilic and chalcophilic elements, leaving mantles depleted in many of the strategic and noble metals relative to their chondritic abundances. Basaltic magma derived from partial melting of the mantle transported to the surface several metals contained in immiscible silicate and sulfide melts. Magmatic ore deposits were formed during cooling, fractional crystallization and density stratification from the basaltic melts. Such ore deposits found in earth's Archean rocks were probably generated during early histories of all terrestrial planets and may be the only types of igneous ores on Mars. Where plate tectonic activity was prevalent on a terrestrial planet, temporal evolution of ore deposits took place. Repetitive episodes of subduction modified the chemical compositions of the crust and upper mantles, leading to porphyry copper and molybdenum ores in calc-alkaline igneous rocks and granite-hosted tin and tungsten deposits. Such plate tectonic-induced mineralization in relatively young igneous rocks on earth may also have produced hydrothermal ore deposits on Venus in addition to the massive sulfide and cumulate chromite ores associated with Venusian mafic igneous rock. Sedimentary ore deposits resulting from mechanical and chemical weathering in reducing atmospheres in Archean earth included placer deposits (e.g., uraninite, gold, pyrite ores). Chromite, ilmenite, and other dense unreactive minerals could also be present on channel floors and in valley networks on Mars, while banded iron formations might underlie the Martian northern plains regions. As oxygen evolved in earth's atmosphere, so too did oxide ores. By analogy, gossans above sulfide ores probably occur on Mars, but not submarine ferromanganese nodules and crusts which have precipitated in oxygenated seawater on earth.

  16. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    SciTech Connect

    Hayes, D. J.; Turner, D. P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, L.; deJong, B.; McConkey, Brian; Birdsey, Richard A.; Kurz, Werner; Jacobson, Andy; Huntzinger, Deborah N.; Pan, Y.; Post, W. M.; Cook, R. B.

    2012-04-02

    While fossil fuel emissions are calculated with relatively high precision, understanding the fate of those emissions with respect to sequestration in terrestrial ecosystems requires data and methods that can reduce uncertainties in the diagnosis of land-based CO2 sinks. The wide range in the land surface flux estimates is related to a number of factors, but most generally because of the different methodologies used to develop estimates of carbon stocks and flux, and the uncertainties inherent in each approach. The alternative approaches to estimating continental scale carbon fluxes that we explored here can be broadly classified as applying a top-down or bottom-up perspective. Top-down approaches calculate land-atmosphere carbon fluxes based on atmospheric budgets and inverse modeling. Bottom-up approaches rely primarily on measurements of carbon stock changes (the inventory approach) or on spatially distributed simulations of carbon stocks and/or fluxes using process-based modeling (the forward modelapproach).

  17. Atmospheric control on ground and space based early warning system for hazard linked to ash injection into the atmosphere

    NASA Astrophysics Data System (ADS)

    Caudron, Corentin; Taisne, Benoit; Whelley, Patrick; Garces, Milton; Le Pichon, Alexis

    2014-05-01

    Violent volcanic eruptions are common in the Southeast Asia which is bordered by active subduction zones with hundreds of active volcanoes. The physical conditions at the eruptive vent are difficult to estimate, especially when there are only a few sensors distributed around the volcano. New methods are therefore required to tackle this problem. Among them, satellite imagery and infrasound may rapidly provide information on strong eruptions triggered at volcanoes which are not closely monitored by on-site instruments. The deployment of an infrasonic array located at Singapore will increase the detection capability of the existing IMS network. In addition, the location of Singapore with respect to those volcanoes makes it the perfect site to identify erupting blasts based on the wavefront characteristics of the recorded signal. There are ~750 active or potentially active volcanoes within 4000 kilometers of Singapore. They have been combined into 23 volcanic zones that have clear azimuth with respect to Singapore. Each of those zones has been assessed for probabilities of eruptive styles, from moderate (Volcanic Explosivity Index of 3) to cataclysmic (VEI 8) based on remote morphologic analysis. Ash dispersal models have been run using wind velocity profiles from 2010 to 2012 and hypothetical eruption scenarios for a range of eruption explosivities. Results can be used to estimate the likelihood of volcanic ash at any location in SE Asia. Seasonal changes in atmospheric conditions will strongly affect the potential to detect small volcanic eruptions with infrasound and clouds can hide eruption plumes from satellites. We use the average cloud cover for each zone to estimate the probability of eruption detection from space, and atmospheric models to estimate the probability of eruption detection with infrasound. Using remote sensing in conjunction with infrasound improves detection capabilities as each method is capable of detecting eruptions when the other is 'blind' or 'defened' by adverse atmospheric conditions. According to its location, each volcanic zone will be associated with a threshold value (minimum VEI detectable) depending on the seasonality of the wind velocity profile in the region and the cloud cover.

  18. Terrestrial planet formation

    PubMed Central

    Righter, K.; O’Brien, D. P.

    2011-01-01

    Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (∼106 y), followed by planetesimals to embryos (lunar to Mars-sized objects; few × 106 y), and finally embryos to planets (107–108 y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids. PMID:21709256

  19. Terrestrial planet formation.

    PubMed

    Righter, K; O'Brien, D P

    2011-11-29

    Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (~10(6) y), followed by planetesimals to embryos (lunar to Mars-sized objects; few 10(6) y), and finally embryos to planets (10(7)-10(8) y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids. PMID:21709256

  20. Mercury in the Canadian Arctic terrestrial environment: an update.

    PubMed

    Gamberg, Mary; Chételat, John; Poulain, Alexandre J; Zdanowicz, Christian; Zheng, Jiancheng

    2015-03-15

    Contaminants in the Canadian Arctic have been studied over the last twenty years under the guidance of the Northern Contaminants Program. This paper provides the current state of knowledge on mercury (Hg) in the Canadian Arctic terrestrial environment. Snow, ice, and soils on land are key reservoirs for atmospheric deposition and can become sources of Hg through the melting of terrestrial ice and snow and via soil erosion. In the Canadian Arctic, new data have been collected for snow and ice that provide more information on the net accumulation and storage of Hg in the cryosphere. Concentrations of total Hg (THg) in terrestrial snow are highly variable but on average, relatively low (<5 ng L(-1)), and methylmercury (MeHg) levels in terrestrial snow are also generally low (<0.1 ng L(-1)). On average, THg concentrations in snow on Canadian Arctic glaciers are much lower than those reported on terrestrial lowlands or sea ice. Hg in snow may be affected by photochemical exchanges with the atmosphere mediated by marine aerosols and halogens, and by post-depositional redistribution within the snow pack. Regional accumulation rates of THg in Canadian Arctic glaciers varied little during the past century but show evidence of an increasing north-to-south gradient. Temporal trends of THg in glacier cores indicate an abrupt increase in the early 1990 s, possibly due to volcanic emissions, followed by more stable, but relatively elevated levels. Little information is available on Hg concentrations and processes in Arctic soils. Terrestrial Arctic wildlife typically have low levels of THg (<5 μg g(-1) dry weight) in their tissues, although caribou (Rangifer tarandus) can have higher Hg because they consume large amounts of lichen. THg concentrations in the Yukon's Porcupine caribou herd vary among years but there has been no significant increase or decrease over the last two decades. PMID:24861531

  1. Forsterite/melt partitioning of argon and iodine: Implications for atmosphere formation by outgassing of an early Martian magma ocean

    NASA Technical Reports Server (NTRS)

    Musselwhite, Donald S.; Drake, Michael J.; Swindle, Timothy D.

    1992-01-01

    Argon and Xe in the Martian atmosphere are radiogenic relative to the Martian mantle if the SNC meteorites are from Mars. Decay of the short lived isotope I-129 to Xe-129 (t sub 1/2 = 16 m.y.) is the most plausible source of the radiogenic Xe. This short half life constrains any process responsible for the elevated Xe-129/Xe-132 ratio of the Martian atmosphere to occur very early in solar system history. Musselwhite et al. proposed that the differential solubility of I and Xe in liquid water played a key role in producing the radiogenic signature in the Martian atmosphere. Here we explore an alternative hypothesis involving purely igneous processes, and motivated in part by new experimental results on the partitioning of I and Xe between minerals and melt.

  2. Terrestrial ecosystems and climatic change

    SciTech Connect

    Emanuel, W.R. ); Schimel, D.S. . Natural Resources Ecology Lab.)

    1990-01-01

    The structure and function of terrestrial ecosystems depend on climate, and in turn, ecosystems influence atmospheric composition and climate. A comprehensive, global model of terrestrial ecosystem dynamics is needed. A hierarchical approach appears advisable given currently available concepts, data, and formalisms. The organization of models can be based on the temporal scales involved. A rapidly responding model describes the processes associated with photosynthesis, including carbon, moisture, and heat exchange with the atmosphere. An intermediate model handles subannual variations that are closely associated with allocation and seasonal changes in productivity and decomposition. A slow response model describes plant growth and succession with associated element cycling over decades and centuries. These three levels of terrestrial models are linked through common specifications of environmental conditions and constrain each other. 58 refs.

  3. Space Vehicle Terrestrial Environment Design Requirements Guidelines

    NASA Technical Reports Server (NTRS)

    Johnson, Dale L.; Keller, Vernon W.; Vaughan, William W.

    2006-01-01

    The terrestrial environment is an important driver of space vehicle structural, control, and thermal system design. NASA is currently in the process of producing an update to an earlier Terrestrial Environment Guidelines for Aerospace Vehicle Design and Development Handbook. This paper addresses the contents of this updated handbook, with special emphasis on new material being included in the areas of atmospheric thermodynamic models, wind dynamics, atmospheric composition, atmospheric electricity, cloud phenomena, atmospheric extremes, and sea state. In addition, the respective engineering design elements are discussed relative to terrestrial environment inputs that require consideration. Specific lessons learned that have contributed to the advancements made in the application and awareness of terrestrial environment inputs for aerospace engineering applications are presented.

  4. The Geology of the Terrestrial Planets

    NASA Technical Reports Server (NTRS)

    Carr, M. H. (Editor); Saunders, R. S.; Strom, R. G.; Wilhelms, D. E.

    1984-01-01

    The geologic history of the terrestrial planets is outlined in light of recent exploration and the revolution in geologic thinking. Among the topics considered are planet formation; planetary craters, basins, and general surface characteristics; tectonics; planetary atmospheres; and volcanism.

  5. Summer Sea Surface Temperature Conditions in the North Atlantic and Their Impact upon the Atmospheric Circulation in Early Winter.

    NASA Astrophysics Data System (ADS)

    Cassou, Christophe; Deser, Clara; Terray, Laurent; Hurrell, James W.; Drévillon, Marie

    2004-09-01

    The origin of the so-called summer North Atlantic “Horseshoe” (HS) sea surface temperature (SST) mode of variability, which is statistically linked to the next winter's North Atlantic Oscillation (NAO), is investigated from data and experiments with the CCM3 atmospheric general circulation model (AGCM). Lagged observational analyses reveal a linkage between HS and anomalous rainfall in the vicinity of the Atlantic intertropical convergence zone. Prescribing the observed anomalous convection in the model generates forced atmospheric Rossby waves that propagate into the North Atlantic sector. The accompanying perturbations in the surface turbulent and radiative fluxes are consistent with forcing the SST anomalies associated with HS. It is suggested that HS can therefore be interpreted as the remote footprint of tropical atmospheric changes.The ARPEGE AGCM is then used to test if the persistence of HS SST anomalies from summer to late fall can feed back to the atmosphere and have an impact on the next winter's North Atlantic variability. Observed HS SST patterns are imposed in the model from August to November. They generate a weak but coherent early winter response projecting onto the NAO and therefore reproduce the observed HS NAO relationship obtained from lagged statistics. Changes in the simulated upper-level jet are associated with the anomalous HS meridional SST gradient and interact with synoptic eddy activity from October onward. The strength and position of the transients as a function of seasons are hypothesized to be of central importance to explain the nature, timing, and sign of the model response.In summary, the present study emphasizes the importance of summer oceanic and atmospheric conditions in both the Tropics and extratropics, and their persistence into early winter for explaining part of the NAO's low-frequency variability.


  6. Pathways to Earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres.

    PubMed

    Lammer, Helmut; Kislyakova, K G; Odert, P; Leitzinger, M; Schwarz, R; Pilat-Lohinger, E; Kulikov, Yu N; Khodachenko, M L; Güdel, M; Hanslmeier, M

    2011-12-01

    We discuss the evolution of the atmosphere of early Earth and of terrestrial exoplanets which may be capable of sustaining liquid water oceans and continents where life may originate. The formation age of a terrestrial planet, its mass and size, as well as the lifetime in the EUV-saturated early phase of its host star play a significant role in its atmosphere evolution. We show that planets even in orbits within the habitable zone of their host stars might not lose nebular- or catastrophically outgassed initial protoatmospheres completely and could end up as water worlds with CO2 and hydrogen- or oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet evolves to an N2-rich atmosphere too early in its lifetime, the atmosphere may be lost. We show that the initial conditions set up by the formation of a terrestrial planet and by the evolution of the host star's EUV and plasma environment are very important factors owing to which a planet may evolve to a habitable world. Finally we present a method for studying the discussed atmosphere evolution hypotheses by future UV transit observations of terrestrial exoplanets. PMID:22314970

  7. Workshop on Oxygen in the Terrestrial Planets

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using Metal-Silicate Partitioning of Te, Se and S; 45) Solubility of Oxygen in Liquid Iron at High Pressure and Consequences for the Early Differentiation of Earth and Mars Metallic Liquid Segregation in Planetesimals; 46) Oxygen Fugacity of Lunar Basalts and the Lunar Mantle. Range of fo2 and the Effectiveness of Oxybarometers; 47) Thermodynamic Study of Dissociation Processes of Molecular Oxygen in Vapor over Oxide Compounds; 48) Oxygen Profile of a Thermo-Haliophilic Community in the Badwater Salt Flat; 49) Oxygen Barometry Using Synchrotron MicroXANES of Vanadium; 50) Mass-Independent Isotopic Fractionation of Sulfur from Sulfides in the Huronian Supergroup, Canada; 51) Mass Independent Isotopes and Applications to Planetary Atmospheres; 52) Electrical Conductivity, Oxygen Fugacity, and Mantle Materials; 53) Crustal Evolution and Maturation on Earth: Oxygen Isotope Evidence; 54) The Oxygen Isotope Composition of the Moon: Implications for Planet Formation; 55) Oxygen Isotope Composition of Eucrites and Implications for the Formation of Crust on the HED Parent Body; and 56) The Role of Water in Determining the Oxygen Isotopic Composition of Planets.

  8. The terrestrial impact cratering record.

    NASA Astrophysics Data System (ADS)

    Grieve, R. A. F.; Pesonen, L. J.

    1992-12-01

    Approximately 130 terrestrial hypervelocity impact craters are currently known. The rate of discovery of new craters is 3 - 5 craters per year. Although modified by erosion, terrestrial impact craters exhibit the range of morphologies observed for craters on other terrestrial planetary bodies. Due to erosion and its effects on form, terrestrial craters are recognized primarily by the occurrence of shock metamorphic effects. Terrestrial craters have a set of geophysical characteristics which are largely the result of the passage of a shock wave and impact-induced fracturing. Much current work is focused on the effects of impact on Earth evolution. Previous work on shock metamorphism and the contamination of impact melt rocks by meteoritic siderophile elements provides a basis for the interpretation of the physical and chemical evidence from Cretaceous-Tertiary boundary sites as resulting from a major impact. By analogy with the lunar record and modelling of the effects of very large impacts, it has been proposed that biological and atmospheric evolution of the Earth could not stabilize before the end of the late heavy bombardment ?3.8 Ga ago. The present terrestrial cratering rate is 5.42.710-15 km-2a-1 for a diameter ?20 km. On a gobal scale, a major impact sufficient to cripple human civilization severely will occur on time scales of ?106a.

  9. Development of a model of atmospheric oxygen variations to estimate terrestrial carbon storage and release. Progress report No. 2, 1 May 1994-30 April 1995

    SciTech Connect

    Najjar, R.G.; Keeling, R.F.; Erickson, D.J. III

    1995-04-01

    Two years of work has been completed towards the development of a model of atmospheric oxygen variations on seasonal to decadal timescales. During the first year the authors (1) constructed a preliminary monthly-mean climatology of surface ocean oxygen anomalies, (2) began modeling studies to assess the importance of short term variability on the monthly-mean oxygen flux, and (3) conducted preliminary simulations of the annual mean cycle of oxygen in the atmosphere. Most of the second year was devoted to improving the monthly mean climatology of oxygen in the surface ocean.

  10. Carbon Dioxide Clouds at High Altitude in the Tropics and in an Early Dense Martian Atmosphere

    NASA Technical Reports Server (NTRS)

    Colaprete, Anthony; Toon, Owen B.

    2001-01-01

    We use a time dependent, microphysical cloud model to study the formation of carbon dioxide clouds in the Martian atmosphere. Laboratory studies by Glandor et al. show that high critical supersaturations are required for cloud particle nucleation and that surface kinetic growth is not limited. These conditions, which are similar to those for cirrus clouds on Earth, lead to the formation of carbon dioxide ice particles with radii greater than 500 micrometers and concentrations of less than 0.1 cm(exp -3) for typical atmospheric conditions. Within the current Martian atmosphere, CO2 cloud formation is possible at the poles during winter and at high altitudes in the tropics during periods of increased atmospheric dust loading. In both cases, temperature perturbations of several degrees below the CO2 saturation temperature are required to nucleate new cloud particles suggesting that dynamical processes are the most common initiators of carbon dioxide clouds rather than diabatic cooling. The microphysical cloud model, coupled to a two-stream radiative transfer model, is used to reexamine the impact of CO2 clouds on the surface temperature within a dense CO2 atmosphere. The formation of carbon dioxide clouds leads to a warmer surface than what would be expected for clear sky conditions. The amount of warming is sensitive to the presence of dust and water vapor in the atmosphere, both of which act to dampen cloud effects. The radiative warming associated with cloud formation, as well as latent heating, work to dissipate the clouds when present. Thus, clouds never last for periods much longer than several days, limiting their overall effectiveness for warming the surface. The time average cloud optical depth is approximately unity leading to a 5-10 K warming, depending on the surface pressure. However, the surface temperature does not rise about the freezing point of liquid water even for pressures as high as 5 bars, at a solar luminosity of 75% the current value.

  11. Bolide impacts and the oxidation state of carbon in the Earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.

    1992-01-01

    A one-dimensional photochemical model was used to examine the effect of bolide impacts on the oxidation state of Earth's primitive atmosphere. The impact rate should have been high prior to 3.8 Ga before present, based on evidence derived from the Moon. Impacts of comets or carbonaceous asteroids should have enhanced the atmospheric CO/CO2 ratio by bringing in CO ice and/or organic carbon that can be oxidized to CO in the impact plume. Ordinary chondritic impactors would contain elemental iron that could have reacted with ambient CO2 to give CO. Nitric oxide (NO) should also have been produced by reaction between ambient CO2 and N2 in the hot impact plumes. High NO concentrations increase the atmospheric CO/CO2 ratio by increasing the rainout rate of oxidized gases. According to the model, atmospheric CO/CO2 ratios of unity or greater are possible during the first several hundred million years of Earth's history, provided that dissolved CO was not rapidly oxidized to bicarbonate in the ocean. Specifically, high atmospheric CO/CO2 ratios are possible if either: (1) the climate was cool (like today's climate), so that hydration of dissolved CO to formate was slow, or (2) the formate formed from CO was efficiently converted into volatile, reduced carbon compounds, such as methane. A high atmospheric CO/CO2 ratio may have helped to facilitate prebiotic synthesis by enhancing the production rates of hydrogen cyanide and formaldehyde. Formaldehyde may have been produced even more efficiently by photochemical reduction of bicarbonate and formate in Fe(++)-rich surface waters.

  12. Changes in IDP mineralogy and composition by terrestrial factors

    NASA Technical Reports Server (NTRS)

    Flynn, George J.

    1994-01-01

    Major objectives in the study of interplanetary dust particles (IDP's) are to constrain the physical and chemical conditions in the early solar system, to characterize the particles making up the zodiacal cloud, and to infer the physical, chemical, mineralogical, and isotopic properties of IDP parent bodies: the comets and the asteroids. However, the effects of terrestrial interactions alter the properties of some IDP's from those of the zodiacal cloud particles. The interactions can be separated into four distinct phases: near-earth gravitational segregation, atmospheric entry deceleration, stratospheric residence, and the collection/curation process.

  13. Cooperative research in terrestrial planetary geology and geophysics

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This final report for the period of July 1991 to August 1994 covered a variety of topics concerning the study of Earth and Mars. The Earth studies stressed the interpretation of the MAGSAT crustal magnetic anomalies in order to determine the geological structure, mineralogical composition, magnetic nature, and the historical background of submarine features, and also featured work in the area of terrestrial remote sensing. Mars research included the early evolution of the Martian atmosphere and hydrosphere and the investigations of the large Martian impact basins. Detailed summaries of the research is included, along with lists of the publications resulting from this research.

  14. Bolide impacts and the oxidation state of carbon in the earth's early atmosphere

    NASA Technical Reports Server (NTRS)

    Kasting, James F.

    1990-01-01

    A one-dimensional photochemical model was used to examine the effect of bolide impacts on the oxidation state of earth's primitive atmosphere. The impact rate should have been high prior to 3.8 Ga before present, based on evidence derived from the moon. Impacts of comets or carbonaceous asteroids should have enhanced the atmospheric CO/CO2 ratio by bringing in CO ice and/or organic carbon that can be oxidized to CO in the impact plume. Ordinary chondritic impactors would contain elemental iron that could have reacted with ambient CO2 to give CO. Nitric oxide (NO) should also have been produced by reaction between ambient CO2 and N2 in the hot impact plumes. High NO concentrations increase the atmospheric CO/CO2 ratio by increasing the rainout rate of oxidized gases. According to the model, atmospheric CO/CO2 ratios of unity or greater are possible during the first several hundred million years of earth's history, provided that dissolved CO was not rapidly oxidized to bicarbonate in the ocean.

  15. Terrestrial carbon cycle responses to drought and climate stress: New insights using atmospheric observations of CO2 and delta13C

    NASA Astrophysics Data System (ADS)

    Alden, Caroline B.

    Atmospheric concentrations of carbon dioxide (CO2) continue to rise well into the second decade of the new millennium, in spite of broad-scale human understanding of the impacts of fossil fuel emissions on the earth's climate. Natural sinks for CO2 that are relevant on human time scales---the world's oceans and land biosphere---appear to have kept pace with emissions. The continuously increasing strength of the land biosphere sink for CO2 is surpassing expectations given our understanding of the CO2 fertilization and warming effects on the balance between photosynthesis and respiration, especially in the face of ongoing forest degradation. The climate and carbon cycle links between the atmosphere and land biosphere are not well understood, especially at regional (100 km to 10,000 km) scales. The climate modulating effects of changing plant stomatal conductance in response to temperature and water availability is a key area of uncertainty. Further, the differential response to climate change of C3 and C4 plant functional types is not well known at regional scales. This work outlines the development of a novel application of atmospheric observations of delta13C of CO2 to investigate the links between climate and water and carbon cycling and the integrated responses of C3 and C4 ecosystems to climate variables. A two-step Bayesian batch inversion for 3-hourly, 1x1º CO2 fluxes (step one), and for 3-hourly 1x1º delta13C of recently assimilated carbon (step two) is created here for the first time, and is used to investigate links between regional climate indicators and changes in delta13C of the biosphere. Results show that predictable responses of regional-scale, integrated plant discrimination to temperature, precipitation and relative humidity anomalies can be recovered from atmospheric signals. Model development, synthetic data simulations to test sensitivity, and results for the year 2010 are presented here. This dissertation also includes two other applications of atmospheric observations of CO2 and delta13C: 1) a state of the art atmospheric CO2 budgeting exercise to show that global net sinks for CO2 have steadily increased over the last 50 years, and 2) a global investigation of the mechanistic drivers of interannual variability in biosphere discrimination against delta13C.

  16. Titan's surface and atmosphere

    NASA Astrophysics Data System (ADS)

    Hayes, Alexander G.; Soderblom, Jason M.; Ádámkovics, Máté

    2016-05-01

    Since its arrival in late 2004, the NASA/ESA Cassini-Huygens mission to Saturn has revealed Titan to be a world that is both strange and familiar. Titan is the only extraterrestrial body known to support standing bodies of stable liquid on its surface and, along with Earth and early Mars, is one of three places in the Solar System known to have had an active hydrologic cycle. With atmospheric pressures of 1.5 bar and temperatures of 90-95 K at the surface, methane and ethane condense out of Titan's nitrogen-dominated atmosphere and flow as liquids on the surface. Despite vast differences in environmental conditions and materials from Earth, Titan's methane-based hydrologic cycle drives climatic and geologic processes which generate landforms that are strikingly similar to their terrestrial counterparts, including vast equatorial dunes, well-organized channel networks that route material through erosional and depositional landscapes, and lakes and seas of liquid hydrocarbons. These similarities make Titan a natural laboratory for studying the processes that shape terrestrial landscapes and drive climates, probing extreme conditions impossible to recreate in earthbound laboratories. Titan's exotic environment ensures that even rudimentary measurements of atmospheric/surface interactions, such as wind-wave generation or aeolian dune development, provide valuable data to anchor physical models.

  17. FINAL REPORT: A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the GCC

    SciTech Connect

    Keeling, R. F.; Piper, S. C.

    2008-12-23

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic composition. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. The program also included the development of methods for measuring radiocarbon content in the collected CO2 samples and carrying out radiocarbon measurements in collaboration with Tom Guilderson of Lawrence Berkeley National Laboratory (LLNL). The radiocarbon measurements can provide complementary information on carbon exchange rates with the land and oceans and emissions from fossil-fuel burning. Using models of varying complexity, the concentration and isotopic measurements were used to establish estimates of the spatial and temporal variations in the net CO2 exchange with the atmosphere, the storage of carbon in the land and oceans, and variable isotopic discrimination of land plants.

  18. The composition of the primitive atmosphere and the synthesis of organic compounds on the early Earth

    NASA Technical Reports Server (NTRS)

    Bada, J. L.; Miller, S. L.

    1985-01-01

    The generally accepted theory for the origin of life on the Earth requires that a large variety of organic compounds be present to form the first living organisms and to provide the energy sources for primitive life either directly or through various fermentation reactions. This can provide a strong constraint on discussions of the formation of the Earth and on the composition of the primitive atmosphere. In order for substantial amounts of organic compounds to have been present on the prebiological Earth, certain conditions must have existed. There is a large body of literature on the prebiotic synthesis of organic compounds in various postulated atmospheres. In this mixture of abiotically synthesized organic compounds, the amino acids are of special interest since they are utilized by modern organisms to synthesize structural materials and a large array of catalytic peptides.

  19. Early Results from the Lunar Atmosphere and Dust Environment Explorer (LADEE)

    NASA Technical Reports Server (NTRS)

    Elphic, R. C.; Hine, B.; Delory, G. T.; Mahaffy, Paul; Benna, Mehdi; Horanyi, Mihaly; Colaprete, Anthony; Noble, Sarah

    2014-01-01

    On 6 September, 2013, a near-perfect launch of the first Minotaur V rocket successfully carried NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) into a high-eccentricity geocentric orbit. After 30 days of phasing, LADEE arrived at the Moon on 6 October, 2013. LADEE's science objectives are twofold: (1) Determine the composition of the lunar atmosphere, investigate processes controlling its distribution and variability, including sources, sinks, and surface interactions; (2) Characterize the lunar exospheric dust environment, measure its spatial and temporal variability, and effects on the lunar atmosphere, if any. After a successful commissioning phase, the three science instruments have made systematic observations of the lunar dust and exospheric environment. These include initial observations of argon, neon and helium exospheres, and their diurnal variations; the lunar micrometeoroid impact ejecta cloud and its variations; spatial and temporal variations of the sodium exosphere; and the search for sunlight extinction caused by dust. LADEE also made observations of the effects of the Chang'e 3 landing on 14 December 2013.

  20. Early Results from the Lunar Atmosphere and Dust Environment Explorer (LADEE)

    NASA Astrophysics Data System (ADS)

    Elphic, Richard C.; Hine, Butler; Delory, Gregory T.; Mahaffy, Paul; Benna, Mehdi; Horanyi, Mihaly; Colaprete, Anthony; Noble, Sarah

    2014-05-01

    On 6 September, 2013, a near-perfect launch of the first Minotaur V rocket success-fully carried NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) into a high-eccentricity geocentric orbit. After 30 days of phasing, LADEE arrived at the Moon on 6 October, 2013. LADEE's science objectives are twofold: (1) Determine the composition of the lunar atmosphere, investigate processes controlling its distribution and variability, including sources, sinks, and surface interactions; (2) Characterize the lunar exospheric dust environment, measure its spatial and temporal variability, and effects on the lunar atmosphere, if any. After a successful commissioning phase, the three science instruments have made systematic observations of the lunar dust and exospheric environment. These include initial observations of argon, neon and helium exospheres, and their diurnal variations; the lunar micrometeoroid impact ejecta cloud and its variations; spatial and temporal variations of the sodium exosphere; and the search for sunlight extinction caused by dust. LADEE also made observations of the effects of the Chang'e 3 landing on 14 December 2013.

  1. Recent increases in trifluoromethane (HFC-23) global emissions and early atmospheric changes observed for other hydrofluorocarbons

    NASA Astrophysics Data System (ADS)

    Montzka, S. A.; Miller, B. R.; Battle, M. O.; Aydin, K. M.; Fahey, D. W.; Hall, B. D.; Miller, L.; Verhulst, K. R.; Saltzman, E.; McFarland, M.

    2009-12-01

    Trifluoromethane (HFC-23) is an unintended by-product of chlorodifluoromethane (HCFC-22) production and has a 100-yr global warming potential of 14,800. Firn-air and ambient air measurements of HFC-23 from three firn sampling excursions to Antarctica between 2001 and 2009 are used to construct a consistent atmospheric history for this chemical in the Southern Hemisphere. The results show continued increases in the atmospheric abundance of HFC-23 and imply substantial increases in HFC-23 global emissions since 2003. These emission increases are coincident with rapidly increasing HCFC-22 production in developing countries and are observed despite efforts in recent years to limit emissions of HFC-23 through the Kyoto Protocol’s Clean Development Mechanism. These results will be considered along with new observations of additional HFCs from archived air, firn air, and ongoing flask-air measurements. Considered together, atmospheric increases observed for hydrochlorofluorocarbons and hydrofluorocarbons accounted for ~9% of the increase in total direct radiative forcing from anthropogenic gases during 2003-2008, an addition that was slightly larger than attributable to N2O over this same period.

  2. Assessing the impact of elevated atmospheric CO{sub 2} and climate change scenarios of two and three dimensional general circulation models on primary production and toatl carbon storage of global terrestrial ecosystems

    SciTech Connect

    Xiao, X.; Kicklighter, D.W.; Melillo, J.M.

    1995-09-01

    The Terrestrial Ecosystem Model (TEM version 4) was applied to simulate primary production and total carbon storage for two atmospheric CO{sub 2} concentrations (315ppm and 630ppm) and three climate scenarios (contemporary, 2-dimensional MIT L-O climate model and 3-dimensional GISS). For contemporary climate (Cramer & Leemans dataset) at 315ppm CO{sub 2}, global annual NPP was 47.9 Pg C.yr{sup {minus}1} and total carbon storage was 1658.2 Pg C. Under atmospheric CO{sub 2} concentration of 630ppm and projected double CO{sub 2} climate by the MIT L-O climate model, global annual NPP increased by 12%, and total carbon storage increased by 11%. Global annual NPP and total carbon storage under the GISS were about 1% to 2% higher than those under the MIT L-O model. The difference in annual NPP and total carbon storage between the GISS and MIT L-O models varied among the 18 biomes, in the range of 0% to 20%. The differences were greatest in the high latitude ecosystems.

  3. Anomalous Xenon in the Precambrian Nuclear Reactor in Okelobondo (Gabon): A Possible Connection to the Fission Component in the Terrestrial Atmosphere

    NASA Technical Reports Server (NTRS)

    Meshik, A. P.; Kehm, K.; Hohenberg, C. M.

    1999-01-01

    Some CFF-Xe (Chemically Fractionated Fission Xenon), whose isotopic composition is established by simultaneous decay and migration of radioactive fission products, is probably present in the Earth's lithosphere, a conclusion based on available Xe data from various crustal and mantle rocks . Our recent isotopic analysis of Xe in alumophosphate from zone 13 of Okelobondo (southern extension of Oklo), along with the independent estimation of the isotopic composition of atmospheric fission Xe , supports the hypothesis that CFF-Xe was produced on a planetary scale. Additional information is contained in the original extended abstract.

  4. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape.

    PubMed

    Kislyakova, Kristina G; Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V; Leitzinger, Martin; Khodachenko, Maxim L; Kulikov, Yuri N; Güdel, Manuel; Hanslmeier, Arnold

    2013-11-01

    We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates. PMID:24283926

  5. Venus: A search for clues to early biological possibilities

    NASA Technical Reports Server (NTRS)

    Colin, Larry; Kasting, James F.

    1992-01-01

    The extensive evidence that there is no extant life on Venus is summarized. The current atmospheric environment, which is far too hostile by terrestrial standards to support life, is described. However, exobiologists are interested in the possibility of extinct life on Venus. The early history of Venus is discussed in terms of its ability to sustain life that may now be extinct.

  6. Measurements of the CO_2 15 μm Band System Broadened by Air, N_2 and CO_2 at Terrestrial Atmospheric Temperatures

    NASA Astrophysics Data System (ADS)

    Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Blake, T. A.; Sams, R. L.

    2009-06-01

    In earth remote sensing, retrievals of atmospheric temperature profiles are often based on observed radiances in infrared spectral regions where emission from atmospheric CO_2 predominates. To achieve improved retrieval accuracy, systematic errors in the forward model must be reduced, especially those associated with errors in the spectroscopic line calculation. We have recorded more than 110 new high-resolution infrared spectra of the 15-μm band system of CO_2 to accurately determine line intensities, self-, air- and N_2-broadened widths and pressure-induced line shifts, along with their temperature dependences. The spectra were recorded with the Bruker IFS 120 HR Fourier transform spectrometer at Pacific Northwest National Laboratory (PNNL) and temperature-controlled sample cells. Sample temperatures were between 206K and 298K. Maximum total pressures were 15 Torr for self-broadening and 613 Torr for air- and N_2-broadening. Analysis is done using a multispectrum fitting technique to retrieve the spectroscopic parameters. Line mixing and other non-Lorentz, non-Voigt line shapes are also assessed. The resulting line parameters are compared with the HITRAN database and with other measurements. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer 96, 139-204 (2005) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer, in press (2009)

  7. Atmospheric and terrestrial water budgets: sensitivity and performance of configurations and global driving data for long term continental scale WRF simulations

    NASA Astrophysics Data System (ADS)

    Fersch, Benjamin; Kunstmann, Harald

    2014-05-01

    Driving data and physical parametrizations can significantly impact the performance of regional dynamical atmospheric models in reproducing hydrometeorologically relevant variables. Our study addresses the water budget sensitivity of the Weather Research and Forecasting Model System WRF (WRF-ARW) with respect to two cumulus parametrizations (Kain-Fritsch, Betts-Miller-Janjić), two global driving reanalyses (ECMWF ERA-INTERIM and NCAR/NCEP NNRP), time variant and invariant sea surface temperature and optional gridded nudging. The skill of global and downscaled models is evaluated against different gridded observations for precipitation, 2 m-temperature, evapotranspiration, and against measured discharge time-series on a monthly basis. Multi-year spatial deviation patterns and basin aggregated time series are examined for four globally distributed regions with different climatic characteristics: Siberia, Northern and Western Africa, the Central Australian Plane, and the Amazonian tropics. The simulations cover the period from 2003 to 2006 with a horizontal mesh of 30 km. The results suggest a high sensitivity of the physical parametrizations and the driving data on the water budgets of the regional atmospheric simulations. While the global reanalyses tend to underestimate 2 m-temperature by 0.2-2 K, the regional simulations are typically 0.5-3 K warmer than observed. Many configurations show difficulties in reproducing the water budget terms, e.g. with long-term mean precipitation biases of 150 mm month-1 and higher. Nevertheless, with the water budget analysis viable setups can be deduced for all four study regions.

  8. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    SciTech Connect

    Hayes, Daniel J; Turner, David P; Stinson, Graham; Mcguire, David; Wei, Yaxing; West, Tristram O.; Heath, Linda S.; De Jong, Bernardus; McConkey, Brian G.; Birdsey, Richard A.; Kurz, Werner; Jacobson, Andrew; Huntzinger, Deborah; Pan, Yude; Post, Wilfred M; Cook, Robert B

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000 2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a 327 252 TgC yr1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (248 TgC yr1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (297 TgC yr1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated tobe a small net source (+18 TgC yr1) due to land use change between 1993 and 2002. We compare these inventorybased estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is 511 TgC yr1 and 931 TgC yr1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional 239 TgC yr1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  9. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data

    USGS Publications Warehouse

    Hayes, Daniel J.; Turner, David P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, Linda S.; de Jong, Bernardus; McConkey, Brian G.; Birdsey, Richard A.; Kurz, Werner A.; Jacobson, Andrew R.; Huntzinger, Deborah N.; Pan, Yude; Post, W. Mac; Cook, Robert B.

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000–2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a -327 ± 252 TgC yr-1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (-248 TgC yr-1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (-297 TgC yr-1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr-1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr-1) due to land use change between 1993 and 2002. We compare these inventory-based estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr-1 and -931 TgC yr-1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional -239 TgC yr-1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  10. Terrestrial soil pH and MAAT records based on the MBT/CBT in the southern South China Sea: implications for the atmospheric CO2 evolution in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Dong, L.; Li, L.; Li, Q.; Zhang, C.

    2013-12-01

    Liang Dong1, Li Li1, Qianyu Li1,2, Chuanlun L. Zhang1,3 1State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China 2School of Earth and Environment Sciences, University of Adelaide, SA 5005, Australia 3Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA The methylation index of branched tetraethers (MBT) and/or the cyclization ratio of branched tetraethers (CBT) are derived from the branched glycerol dialkyl Glycerol tetraethers (GDGTs) of bacterial origin and are widely used to reconstruct the terrestrial soil pH and mean annual air temperature (MAAT); however, these proxies are less frequently used in the oceanic settings. Here we provide the first high resolution records of soil pH and MAAT since the last glacial maximum based on the sedimentary core of MD05-2896 in the southern South China Sea. The MAAT record exhibited typical glacial and interglacial cycles and was consistent with the winter insolation variation. The pH values were lower (6.4-7) in the glacial time and higher (7-8.4) in the interglacial time. Changes in soil pH allowed the evaluation of changes in soil CO2 based on the atmosphere-soil CO2 balance. The results imply that the lower winter MAAT variation with a lower winter atmospheric CO2 concentration might have resulted in a higher pH in the interglacial period. Our records provide a new insight into the evolution of atmospheric CO2 between glacial and interglacial cycles in East Asia. Key words: South China Sea, MBT/CBT, b-GDGTs, MAAT, pH

  11. Identification of nitrogenous organic species in Titan aerosols analogs: Nitrogen fixation routes in early atmospheres

    NASA Astrophysics Data System (ADS)

    He, Chao; Smith, Mark A.

    2013-09-01

    Titan, an icy world surrounded by auburn organic haze, is considered as one of the best targets for studying abiotic planetary organic chemistry. In spite of a great many efforts being made, the chemistry in Titan’s atmosphere and its resulting chemical structures are still not fully understood. In our previous work, we have investigated the structure of Titan aerosols analogs (tholin) by NMR and identified hexamethylenetetramine as a dominant small molecule in Titan tholin. Here we report a more complete and definitive structural investigation of the small molecule inventory in Titan tholin. We identified several nitrogenous organic molecules including cyanamide, guanidine, 2-cyanoguanidine, melamine, N‧-cyanoformamidine and 1,2,4-triazole in Titan tholin by using NMR and GC-MS and standard sample comparison. The structural characteristics of these molecules suggest a possible formation pathway from the reaction of HCN and NH3, both of which are known to exist in appreciable density in the atmosphere and were tentatively detected by the Huygens probe.

  12. Spherically symmetric, expanding, non-LTE model atmospheres for novae during their early stages

    NASA Technical Reports Server (NTRS)

    Hauschildt, P. H.; Wehrse, R.; Starrfield, S.; Shaviv, G.

    1992-01-01

    In the continuum and line-blanketed models presented here, nova atmospheres are characterized by a very slow decrease of density with increasing radius. This feature leads to very large geometrical extensions so that there are large temperature differences between the inner and outer parts of the line-forming regions. The theoretical spectra show a large IR excess and a small Balmer jump which may be either in absorption or in emission. For the parameters considered (effective temperature of about 10 exp 4 K, L = 2 x 10 exp 4 solar luminosities, outer boundary density of about 3 x 10 exp -15 g cm exp -3, mass-loss rate of 10 exp -5 solar masses/yr), most lines are in absorption. The effects of changes in the abundances of the heavy elements on the emergent spectra are discussed. The strong unidentified features observed in ultraviolet spectra of novae are found in actuality to be regions of transparency within the Fe 'forest'. Ultraviolet spectra obtained from the IUE archives are displayed, and spectral synthesis of these spectra is done using the theoretical atmospheres.

  13. Evaporative Control on Soil Water Isotope Ratios: Implications for Atmosphere-Land Surface Water Fluxes and Interpretation of Terrestrial Proxy Records

    NASA Astrophysics Data System (ADS)

    Kaushik, A.; Noone, D. C.; Berkelhammer, M. B.; O'Neill, M.

    2014-12-01

    The moisture balance of the continental boundary layer plays an important role in regulating the exchange of water and energy between the land surface and atmosphere. Near-surface moisture balance is controlled by a number of factors including precipitation, infiltration and evapotranspiration. Measurements of stable isotope ratios in water can be exploited to better understand the mechanisms controlling atmosphere-land surface water fluxes. Understanding the processes that set sub-surface water isotope ratios can prove useful for refining paleoclimate interpretations of stable oxygen and hydrogen isotope-based proxies. We present in situ tower-based measurements of stable isotope ratios of water (δD and δ18O) in vapor, precipitation and soil from the Boulder Atmospheric Observatory, a semi-arid tall-tower site in Erie, Colorado, from July 2012 to September 2014. Near surface profiles from 0 to 10 m were measured approximately every ninety minutes. Soil profiles from 0 to 30 cm, the region of maximum variability, were sampled on a weekly basis and cryogenically extracted for stable water isotope measurement. Evaporation-proof bulk rain collectors provided precipitation samples at this site. Results show disequilibrium exists between surface vapor and soil water isotopes, with the top 10 cm of soil water approaching equilibrium with the surface vapor right after a rain event because of high infiltration and saturation at the surface. At this semi-arid site with little vegetation, evaporative exchange is the main driver for soil water fluxes as the soil dries, corroborated by soil Dexcess profiles showing progressive enrichment through evaporation. In addition, when nighttime surface temperatures are cooler than deep soil, as is the case in many arid and semi-arid environments, upward vapor diffusion from the soil leads to dew formation at the surface which then contributes to surface vapor values. We use these observations to constrain a Craig-Gordon evaporation model at the land surface to weight the contributions of rainfall, surface water vapor exchange and sub-surface vapor diffusion to soil water isotope values. This has implications both for modeling short-term gas exchange at the land surface as well as for estimating past evaporative conditions from proxies like cave deposits and tree cellulose.

  14. Early atmospheric metal pollution provides evidence for Chalcolithic/Bronze Age mining and metallurgy in Southwestern Europe.

    PubMed

    Martínez Cortizas, Antonio; López-Merino, Lourdes; Bindler, Richard; Mighall, Tim; Kylander, Malin E

    2016-03-01

    Although archaeological research suggests that mining/metallurgy already started in the Chalcolithic (3rd millennium BC), the earliest atmospheric metal pollution in SW Europe has thus far been dated to ~3500-3200cal.yr. BP in paleo-environmental archives. A low intensity, non-extensive mining/metallurgy and the lack of appropriately located archives may be responsible for this mismatch. We have analysed the older section (>2100cal.yr. BP) of a peat record from La Molina (Asturias, Spain), a mire located in the proximity (35-100km) of mines which were exploited in the Chalcolithic/Bronze Age, with the aim of assessing evidence of this early mining/metallurgy. Analyses included the determination of C as a proxy for organic matter content, lithogenic elements (Si, Al, Ti) as markers of mineral matter, and trace metals (Cr, Cu, Zn, Pb) and stable Pb isotopes as tracers of atmospheric metal pollution. From ~8000 to ~4980cal.yr. BP the Pb composition is similar to that of the underlying sediments (Pb 15±4μgg(-1); (206)Pb/(207)Pb 1.204±0.002). A sustained period of low (206)Pb/(207)Pb ratios occurred from ~4980 to ~2470cal.yr. BP, which can be divided into four phases: Chalcolithic (~4980-3700cal.yr. BP), (206)Pb/(207)Pb ratios decline to 1.175 and Pb/Al ratios increase; Early Bronze Age (~3700-3500cal.yr. BP), (206)Pb/(207)Pb increase to 1.192 and metal/Al ratios remain stable; Late Bronze Age (~3500-2800cal.yr. BP), (206)Pb/(207)Pb decline to their lowest values (1.167) while Pb/Al and Zn/Al increase; and Early Iron Age (~2800-2470cal.yr. BP), (206)Pb/(207)Pb increase to 1.186, most metal/Al ratios decrease but Zn/Al shows a peak. At the beginning of the Late Iron Age, (206)Pb/(207)Pb ratios and metal enrichments show a rapid return to pre-anthropogenic values. These results provide evidence of regional/local atmospheric metal pollution triggered by the earliest phases of mining/metallurgy in the area, and reconcile paleo-environmental and archaeological records. PMID:26748004

  15. Polar front shift and atmospheric CO2 during the glacial maximum of the Early Paleozoic Icehouse

    PubMed Central

    Vandenbroucke, Thijs R. A.; Armstrong, Howard A.; Williams, Mark; Paris, Florentin; Zalasiewicz, Jan A.; Sabbe, Koen; Nlvak, Jaak; Challands, Thomas J.; Verniers, Jacques; Servais, Thomas

    2010-01-01

    Our new data address the paradox of Late Ordovician glaciation under supposedly high pCO2 (8 to 22 PAL: preindustrial atmospheric level). The paleobiogeographical distribution of chitinozoan (mixed layer) marine zooplankton biotopes for the Hirnantian glacial maximum (440Ma) are reconstructed and compared to those from the Sandbian (460Ma): They demonstrate a steeper latitudinal temperature gradient and an equatorwards shift of the Polar Front through time from 5570S to ?40S. These changes are comparable to those during Pleistocene interglacial-glacial cycles. In comparison with the Pleistocene, we hypothesize a significant decline in mean global temperature from the Sandbian to Hirnantian, proportional with a fall in pCO2 from a modeled Sandbian level of ?8 PAL to ?5 PAL during the Hirnantian. Our data suggest that a compression of midlatitudinal biotopes and ecospace in response to the developing glaciation was a likely cause of the end-Ordovician mass extinction. PMID:20696937

  16. Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction

    PubMed Central

    Chin, Karen; Pearson, Dean; Ekdale, A. A.

    2013-01-01

    The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms. PMID:23951041

  17. Fossil worm burrows reveal very early terrestrial animal activity and shed light on trophic resources after the end-cretaceous mass extinction.

    PubMed

    Chin, Karen; Pearson, Dean; Ekdale, A A

    2013-01-01

    The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms. PMID:23951041

  18. Statistical equilibrium calculations for silicon in early-type model stellar atmospheres

    NASA Technical Reports Server (NTRS)

    Kamp, L. W.

    1976-01-01

    Line profiles of 36 multiplets of silicon (Si) II, III, and IV were computed for a grid of model atmospheres covering the range from 15,000 to 35,000 K in effective temperature and 2.5 to 4.5 in log (gravity). The computations involved simultaneous solution of the steady-state statistical equilibrium equations for the populations and of the equation of radiative transfer in the lines. The variables were linearized, and successive corrections were computed until a minimal accuracy of 1/1000 in the line intensities was reached. The common assumption of local thermodynamic equilibrium (LTE) was dropped. The model atmospheres used also were computed by non-LTE methods. Some effects that were incorporated into the calculations were the depression of the continuum by free electrons, hydrogen and ionized helium line blocking, and auto-ionization and dielectronic recombination, which later were found to be insignificant. Use of radiation damping and detailed electron (quadratic Stark) damping constants had small but significant effects on the strong resonance lines of Si III and IV. For weak and intermediate-strength lines, large differences with respect to LTE computations, the results of which are also presented, were found in line shapes and strengths. For the strong lines the differences are generally small, except for the models at the hot, low-gravity extreme of our range. These computations should be useful in the interpretation of the spectra of stars in the spectral range B0-B5, luminosity classes III, IV, and V.

  19. Spaceborne Microwave Remote Sensing of Seasonal Freeze-Thaw Processes in the Terrestrial High Latitudes: Relationships with Land-Atmosphere CO2 exchange

    NASA Technical Reports Server (NTRS)

    McDonald, Kyle C.; Kimball, John S.; Zhao, Maosheng; Njoku, Eni; Zimmermann, Reiner; Running, Steven W.

    2004-01-01

    Landscape transitions between seasonally frozen and thawed conditions occur each year over roughly 50 million square kilometers of Earth's Northern Hemisphere. These relatively abrupt transitions represent the closest analog to a biospheric and hydrologic on/off switch existing in nature, affecting surface meteorological conditions, ecological trace gas dynamics, energy exchange and hydrologic activity profoundly. We utilize time series satellite-borne microwave remote sensing measurements from the Special Sensor Microwave Imager (SSM/I) to examine spatial and temporal variability in seasonal freeze/thaw cycles for the pan-Arctic basin and Alaska. Regional measurements of spring thaw timing are derived using daily brightness temperature measurements from the 19 GHz, horizontally polarized channel, separately for overpasses with 6 AM and 6 PM equatorial crossing times. Spatial and temporal patterns in regional freeze/thaw dynamics show distinct differences between North America and Eurasia, and boreal forest and Arctic tundra biomes. Annual anomalies in the timing of thawing in spring also correspond closely to seasonal atmospheric CO2 concentration anomalies derived from NOAA CMDL arctic and subarctic monitoring stations. Classification differences between AM and PM overpass data average approximately 5 days for the region, though both appear to be effective surrogates for monitoring annual growing seasons at high latitudes.

  20. Unusually strong nitric oxide descent in the Arctic middle atmosphere in early 2013 as observed by Odin/SMR

    NASA Astrophysics Data System (ADS)

    Pérot, K.; Urban, J.; Murtagh, D. P.

    2014-08-01

    The middle atmosphere was affected by an exceptionally strong midwinter stratospheric sudden warming (SSW) during the Arctic winter 2012/2013. These unusual meteorological conditions led to a breakdown of the polar vortex, followed by the reformation of a strong upper stratospheric vortex associated with particularly efficient descent of air. Measurements by the submillimetre radiometer (SMR), on board the Odin satellite, show that very large amounts of nitric oxide (NO), produced by energetic particle precipitation (EPP) in the mesosphere/lower thermosphere (MLT), could thus enter the polar stratosphere in early 2013. The mechanism referring to the downward transport of EPP-generated NOx during winter is generally called the EPP indirect effect. SMR observed up to 20 times more NO in the upper stratosphere than the average NO measured at the same latitude, pressure and time during three previous winters where no mixing between mesospheric and stratospheric air was noticeable. This event turned out to be the strongest in the aeronomy-only period of SMR (2007-present). Our study is based on a comparison with the Arctic winter 2008/2009, when a similar situation was observed. This outstanding situation is the result of the combination of a relatively high geomagnetic activity and an unusually high dynamical activity, which makes this case a prime example to study the EPP impacts on the atmospheric composition.

  1. Atmospheric CO2 from the late Oligocene to early Miocene reconstructed from photosynthesis data and leaf characteristics of fossil plants

    NASA Astrophysics Data System (ADS)

    Grein, Michaela; Oehm, Christoph; Konrad, Wilfried; Utescher, Torsten; Kunzmann, Lutz; Roth-Nebelsick, Anita

    2013-04-01

    In the Cenozoic era, global climate changed from greenhouse to icehouse conditions. During the Oligocene, the comparatively cool phase in the earlier part of the late Oligocene is followed by the Late Oligocene Warming and a major glaciation event at the Oligocene-Miocene transition (Mi-1). Various studies indicate that these climate events were coupled to changes in atmospheric CO2 levels. In this study, atmospheric CO2 from the late Oligocene to the early Miocene was reconstructed by using photosynthesis data and fossil leaf characteristics. We used plant material from various sites located in Germany and Austria comprising fossil leaves of four angiosperm plant species: Platanus neptuni (Platanaceae), Quercus rhenana, Q. praerhenana and Eotrigonobalanus furcinervis (all Fagaceae). A mechanistic-theoretical approach based on stomatal parameters, photosynthesis data and gas exchange parameters was applied to model palaeoatmospheric CO2 levels. Detailed climate data of the considered sites were reconstructed as well since the mechanistic-theoretical approach requires climate data as input parameters for calculating both assimilation rate and transpiration rate. Our results indicate a steady CO2 level of about 400 ppm for all sites and therefore suggest a decoupling of CO2 and cooling/warming events for the considered time slices.

  2. Early 21st Century Anomalously Cold Central Eurasian Winters Forced By Arctic Sea Ice Retreat in an Atmosphere Model

    NASA Astrophysics Data System (ADS)

    Semenov, V. A.; Latif, M.

    2014-12-01

    The early 21st century was marked by several severe winters over Central Eurasia linked to a blocking anti-cyclone centered south of the Barents Sea (BS). The increased occurrence of such anomalously cold winters coincided with a strong reduction of winter Arctic sea ice cover (ASIC), especially in the BS where sea ice area exhibited a step-like decline in 2005, suggesting a possible connection. To study the possible link we performed simulations with a high-resolution global atmospheric general circulation model forced by a set of multi-year sea ice anomalies observed during the last decades. The regional circulation response to reduced ASIC in 2005-2012 exhibits a statistically significant anti-cyclonic surface pressure anomaly and a surface temperature response similar to that observed. The results suggest that the recent BS sea ice reduction may have been responsible for the recent anomalously cold winters in Central Eurasia. Furthermore, a positive sea ice anomaly in the late 1960s associated with negative phase of the North Atlantic Oscillation also results in a similar anti-cyclonic anomaly and a cooling over the continent in the model. This implies that the atmospheric circulation response to sea ice anomalies during the period of modern sea ice decline can be essentially non-linear, both with respect to amplitude and pattern.

  3. Solar-terrestrial models and application software

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter

    1990-01-01

    The empirical models related to solar-terrestrial sciences are listed and described which are available in the form of computer programs. Also included are programs that use one or more of these models for application specific purposes. The entries are grouped according to the region of the solar-terrestrial environment to which they belong and according to the parameter which they describe. Regions considered include the ionosphere, atmosphere, magnetosphere, planets, interplanetary space, and heliosphere. Also provided is the information on the accessibility for solar-terrestrial models to specify the magnetic and solar activity conditions.

  4. Solar-terrestrial models and application software

    NASA Technical Reports Server (NTRS)

    Bilitza, D.

    1992-01-01

    The empirical models related to solar-terrestrial sciences are listed and described which are available in the form of computer programs. Also included are programs that use one or more of these models for application specific purposes. The entries are grouped according to the region of their solar-terrestrial environment to which they belong and according to the parameter which they describe. Regions considered include the ionosphere, atmosphere, magnetosphere, planets, interplanetary space, and heliosphere. Also provided is the information on the accessibility for solar-terrestrial models to specify the magnetic and solar activity conditions.

  5. Early deglacial Atlantic overturning decline and its role in atmospheric CO2 rise inferred from carbon isotopes (δ13C)

    NASA Astrophysics Data System (ADS)

    Schmittner, A.; Lund, D. C.

    2015-02-01

    The reason for the initial rise in atmospheric CO2 during the last deglaciation remains unknown. Most recent hypotheses invoke Southern Hemisphere processes such as shifts in midlatitude westerly winds. Coeval changes in the Atlantic meridional overturning circulation (AMOC) are poorly quantified, and their relation to the CO2 increase is not understood. Here we compare simulations from a global, coupled climate-biogeochemistry model that includes a detailed representation of stable carbon isotopes (δ13C) with a synthesis of high-resolution δ13C reconstructions from deep-sea sediments and ice core data. In response to a prolonged AMOC shutdown initialized from a preindustrial state, modeled δ13C of dissolved inorganic carbon (δ13CDIC) decreases in most of the surface ocean and the subsurface Atlantic, with largest amplitudes (more than 1.5‰) in the intermediate-depth North Atlantic. It increases in the intermediate and abyssal South Atlantic, as well as in the subsurface Southern, Indian, and Pacific oceans. The modeled pattern is similar and highly correlated with the available foraminiferal δ13C reconstructions spanning from the late Last Glacial Maximum (LGM, ~19.5-18.5 ka BP) to the late Heinrich stadial event 1 (HS1, ~16.5-15.5 ka BP), but the model overestimates δ13CDIC reductions in the North Atlantic. Possible reasons for the model-sediment-data differences are discussed. Changes in remineralized δ13CDIC dominate the total δ13CDIC variations in the model but preformed contributions are not negligible. Simulated changes in atmospheric CO2 and its isotopic composition (δ13CCO2) agree well with ice core data. Modeled effects of AMOC-induced wind changes on the carbon and isotope cycles are small, suggesting that Southern Hemisphere westerly wind effects may have been less important for the global carbon cycle response during HS1 than previously thought. Our results indicate that during the early deglaciation the AMOC decreased for several thousand years. We propose that the observed early deglacial rise in atmospheric CO2 and the decrease in δ13CCO2 may have been dominated by an AMOC-induced decline of the ocean's biologically sequestered carbon storage.

  6. Climate change effects on environment (marine, atmospheric and terrestrial) and human perception in an Italian Region (Marche) and the nearby northern Adriatic Sea.

    NASA Astrophysics Data System (ADS)

    Appiotti, F.; Krzelj, M.; Marincioni, F.; Russo, A.

    2012-04-01

    An integrated analysis of recent climate change, including atmosphere, sea and land, as well as some of the impacts on society, has been conducted on the Marche Region in central Italy and the northern portion of the Adriatic Sea. The Marche Region is one of the 20 administrative divisions of Italy, located at a latitude approximately 43° North, with a total surface area of 9,366 km2 and 1,565,000 residents. The northern Adriatic Sea is the northernmost area of the Mediterranean Sea, and it has peculiar relevance for several aspects (environment, tourism, fisheries, economy). The collected environmental data included meteorological stations (daily maximum and minimum air temperature, daily precipitation), oceanographic stations (sea temperature, salinity, dissolved oxygen, nutrient salts concentration, chlorophyll) and river flows, over the last 50 years. The collected social data include 800 questionnaires and interviews carried out on selected samples of residents, decision-makers and emergency managers. These questionnaires and interviews aimed at highlighting the perception of climate change risks. The trend analysis of air temperature and precipitation data detailed an overall temperature increase in all seasons and rainfall decreases in Winter, Spring and Summer with Autumn increases, influencing river flow changes. Marine data showed a relevant warming of the water column in the period after 1990 in comparison with the previous period, particularly in the cold season. Surface salinity increased in Spring and Summer and strongly decreased in Autumn and Winter (according with the precipitation and river flow changes). These last mentioned changes, combined with anthropogenic effects, also influenced the marine ecosystems, with changes of nutrient salts, chlorophyll and dissolved oxygen. Changes in nutrient discharge from rivers influenced the average marine chlorophyll concentration reduction and the consequent average reduction of warm season hypoxic conditions. Indeed, all these changes influence several other aspects of the North Adriatic marine environment, such as coastal erosion, ecosystems, biological productivity, mucilage phenomena, harmful algal blooms, etc.. These impacts in the coastal areas are also evident inland. For example, the analysis of agro-meteorological extreme indices (aridity index, potential water deficit) suggests negative impacts in terms of soil deterioration and agricultural productivity, particularly evident in the area close to the coast. Finally, the analysis of social data revealed awareness among local residents of these impacts and associated risks connected to climate change. Yet, this awareness does not appear translated into long term adaptation plans. Apparently, the inability to define shared collective strategies is the result of a feeble sense of individual and institutional responsibility about climate matters, and ineffective information exchange among citizens, public administrators and the scientific community.

  7. Improving the Ginkgo CO2 barometer: Implications for the early Cenozoic atmosphere

    NASA Astrophysics Data System (ADS)

    Barclay, Richard S.; Wing, Scott L.

    2016-04-01

    Stomatal properties of fossil Ginkgo have been used widely to infer the atmospheric concentration of CO2 in the geological past (paleo-pCO2). Many of these estimates of paleo-pCO2 have relied on the inverse correlation between pCO2 and stomatal index (SI - the proportion of epidermal cells that are stomata) observed in recent Ginkgo biloba, and therefore depend on the accuracy of this relationship. The SI - pCO2 relationship in G. biloba has not been well documented, however. Here we present new measurements of SI for leaves of G. biloba that grew under pCO2 from 290 to 430 ppm. We prepared and imaged all specimens using a consistent procedure and photo-documented each count. As in prior studies, we found a significant inverse relationship between SI and pCO2, however, the relationship is more linear, has a shallower slope, and a lower correlation coefficient than previously reported. We examined leaves of G. biloba grown under pCO2 of 1500 ppm, but found they had highly variable SI and a large proportion of malformed stomata. We also measured stomatal dimensions, stomatal density, and the carbon isotope composition of G. biloba leaves in order to test a mechanistic model for inferring pCO2. This model overestimated observed pCO2, performing less well than the SI method between 290 and 430 ppm. We used our revised SI-pCO2 response curve, and new observations of selected fossils, to estimate late Cretaceous and Cenozoic pCO2 from fossil Ginkgo adiantoides. All but one of the new estimates is below 800 ppm, and together they show little long-term change in pCO2 or relation to global temperature. The low Paleogene pCO2 levels indicated by the Ginkgo SI proxy are not consistent with the high pCO2 inferred by some climate and carbon cycle models. We cannot currently resolve the discrepancy, but greater agreement between proxy data and models may come from a better understanding of the stomatal response of G. biloba to elevated pCO2, better counts and measurements of fossil Ginkgo, or models that can simulate greenhouse climates at lower pCO2.

  8. Terrestrial Planet Geophysics

    NASA Astrophysics Data System (ADS)

    Phillips, R. J.

    2008-12-01

    Terrestrial planet geophysics beyond our home sphere had its start arguably in the early 1960s, with Keith Runcorn contending that the second-degree shape of the Moon is due to convection and Mariner 2 flying past Venus and detecting no planetary magnetic field. Within a decade, in situ surface geophysical measurements were carried out on the Moon with the Apollo program, portions of the lunar magnetic and gravity fields were mapped, and Jack Lorell and his colleagues at JPL were producing spherical harmonic gravity field models for Mars using tracking data from Mariner 9, the first spacecraft to orbit another planet. Moreover, Mariner 10 discovered a planetary magnetic field at Mercury, and a young Sean Solomon was using geological evidence of surface contraction to constrain the thermal evolution of the innermost planet. In situ geophysical experiments (such as seismic networks) were essentially never carried out after Apollo, although they were sometimes planned just beyond the believability horizon in planetary mission queues. Over the last three decades, the discipline of terrestrial planet geophysics has matured, making the most out of orbital magnetic and gravity field data, altimetric measurements of surface topography, and the integration of geochemical information. Powerful constraints are provided by tectonic and volcanic information gleaned from surface images, and the engagement of geologists in geophysical exercises is actually quite useful. Accompanying these endeavors, modeling techniques, largely adopted from the Earth Science community, have become increasingly sophisticated and have been greatly enhanced by the dramatic increase in computing power over the last two decades. The future looks bright with exciting new data sets emerging from the MESSENGER mission to Mercury, the promise of the GRAIL gravity mission to the Moon, and the re-emergence of Venus as a worthy target for exploration. Who knows? With the unflagging optimism and persistence of a few diehards, we may eventually have a seismic and heat flow network on Mars.

  9. Observations of Middle Atmosphere CO from the UARS ISAMS during the Early Northern Winter 1991/92

    NASA Technical Reports Server (NTRS)

    Allen, D. R.; Stanford, J. L.; Lopez-Valverde, M. A.; Nakamura, N.; Lary, D. J.; Douglass, A. R.; Cerniglia, M. C.; Remedios, J. J.; Taylor, F. W.

    1999-01-01

    Structure and kinematics of carbon monoxide in the upper stratosphere and lower mesosphere (10-0.03 hPa) are studied for the early northern winter 1991/92 using the Upper Atmosphere Research Satellite Improved Stratospheric and Mesospheric Sounder (ISAMS) measurements. The study is aided by data from a 6-week parameterized-chemistry run of the Goddard Space Flight Center 3D Chemistry and Transport Model (CTM), initialized on 8 December 1991. Generally, CO mixing ratios increase with height due to the increasing source contribution from CO, photolysis. In the tropical upper stratosphere. however, a local maximum in CO mixing ratio occurs. A simple photochemical model is used to show that this feature results largely from methane oxidation. In the extratropics the photochemical lifetime of CO is long, and therefore its evolution is dictated by large-scale motion of air. evidenced by strong correlation with Ertel potential vorticity. This makes CO one of the few useful observable tracers at the stratopause level and above. Thus CO maps are used to study the synoptic evolution of the polar vortex in early January 1992. Modified Lagrangian mean mixing diagnostics are applied to ISAMS and CTM data to examine the strength of the mixing barrier at the polar vortex edge. It is demonstrated that planetary wave activity weakens the barrier. promoting vortex erosion. The vortex erosion first appears in the lower mesosphere and subsequently descends through the upper stratosphere. and is attributed to effects of planetary wave dissipation. Agreement between ISAMS and CTM is good in the horizontal distribution of CO throughout the examined period, but vertical CO gradients in the CTM weaken with time relative to the ISAMS observations.

  10. Expansion of Voltage-dependent Na+ Channel Gene Family in Early Tetrapods Coincided with the Emergence of Terrestriality and Increased Brain Complexity

    PubMed Central

    Zakon, Harold H.; Jost, Manda C.; Lu, Ying

    2011-01-01

    Mammals have ten voltage-dependent sodium (Nav) channel genes. Nav channels are expressed in different cell types with different subcellular distributions and are critical for many aspects of neuronal processing. The last common ancestor of teleosts and tetrapods had four Nav channel genes, presumably on four different chromosomes. In the lineage leading to mammals, a series of tandem duplications on two of these chromosomes more than doubled the number of Nav channel genes. It is unknown when these duplications occurred and whether they occurred against a backdrop of duplication of flanking genes on their chromosomes or as an expansion of ion channel genes in general. We estimated key dates of the Nav channel gene family expansion by phylogenetic analysis using teleost, elasmobranch, lungfish, amphibian, avian, lizard, and mammalian Nav channel sequences, as well as chromosomal synteny for tetrapod genes. We tested, and exclude, the null hypothesis that Nav channel genes reside in regions of chromosomes prone to duplication by demonstrating the lack of duplication or duplicate retention of surrounding genes. We also find no comparable expansion in other voltage-dependent ion channel gene families of tetrapods following the teleost–tetrapod divergence. We posit a specific expansion of the Nav channel gene family in the Devonian and Carboniferous periods when tetrapods evolved, diversified, and invaded the terrestrial habitat. During this time, the amniote forebrain evolved greater anatomical complexity and novel tactile sensory receptors appeared. The duplication of Nav channel genes allowed for greater regional specialization in Nav channel expression, variation in subcellular localization, and enhanced processing of somatosensory input. PMID:21148285

  11. Nanophase Iron Oxides as an Ultraviolet Sunscreen for Ancient Photosynthetic Microbes: A Possible Link Between Early Organisms, Banded-Iron Formations, and the Oxygenation of the Atmosphere

    NASA Technical Reports Server (NTRS)

    Bishop, Janice L.; Rothschild, Lynn J.; Rothschild, Lynn J.; Rogoff, Dana A.

    2006-01-01

    We propose that nanophase iron oxide-bearing materials provided important niches for ancient photosynthetic microbes on the early Earth that ultimately led to the oxygenation of the Earth s atmosphere and the formation of iron oxide deposits. Atmospheric oxygen and ozone attenuate UV radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose then and played a critical role in subsequent evolution. Of primary importance was protection at approx.250-290 nm, where peak nucleic acid (approx.260 nm) and protein (approx.280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal UV radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Further, they were available in early environments, and are synthesized by many organisms. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the photosynthetic organisms, Euglena sp. and Chlumydomonus reinhardtii, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides. The results of this study are also applicable to other potentially habitable iron-bearing planetary bodies because of the evolutionary pressure to utilize solar radiation when available as an energy source.

  12. Terrestrial Environment (Climatic) Criteria Handbook For Use in Aerospace Vehicle Development

    NASA Technical Reports Server (NTRS)

    Johnson, Dale; Vaughan, William W.

    2004-01-01

    An update of the NASA 'Terrestrial Environment (Climatic) Criteria Handbook for Use in Aerospace Vehicle Development' (NASA-HDBK-1001) is currently in the final process of completion for release in late-2004 or early 2005. The current version of the Handbook was approved by the NASA Chief Engineer in 2000 as a NASA Preferred Technical Standard. However, it was based on natural environment criteria developed mostly in the early 1990's. Therefore, a task was approved to completely update the Handbook in order to reflect the current state-of-the-art in the various terrestrial environmental climatic criteria areas. The technical areas include: Winds, atmospheric constituents, thermodynamic parameters/models/extremes, humidity, electricity, precipitation/fog/icing, cloud phenomena/cover, diffusion/toxic release, severe weather/tornado/hurricane, solar/thermal radiation, geologic hazards, and sea state. A summary of this extensive update will be presented along with some key examples of the new contents. Earlier versions of this publication have been extensively used by the aerospace community, especially program managers and design engineers for required natural terrestrial environment inputs to use in mission planning, development studies and trades, plus by those concerned with terrestrial environment descriptions for the major test ranges within the United States.

  13. Identification of Terrestrial Reflectance From Remote Sensing

    NASA Technical Reports Server (NTRS)

    Alter-Gartenberg, Rachel; Nolf, Scott R.; Stacy, Kathryn (Technical Monitor)

    2000-01-01

    Correcting for atmospheric effects is an essential part of surface-reflectance recovery from radiance measurements. Model-based atmospheric correction techniques enable an accurate identification and classification of terrestrial reflectances from multi-spectral imagery. Successful and efficient removal of atmospheric effects from remote-sensing data is a key factor in the success of Earth observation missions. This report assesses the performance, robustness and sensitivity of two atmospheric-correction and reflectance-recovery techniques as part of an end-to-end simulation of hyper-spectral acquisition, identification and classification.

  14. Terrestrial photovoltaic collector technology trend

    SciTech Connect

    Shimada, K.; Costogue, E.

    1984-08-01

    Following the path of space PV collector development in its early stages, terrestrial PV technologies based upon single-crystal silicon have matured rapidly. Currently, terrestrial PV cells with efficiencies approaching space cell efficiencies are being fabricated into modules at a fraction of the space PV module cost. New materials, including CuInSe/sub 2/ and amorphous silicon, are being developed for lowering the cost, and multijunction materials for achieving higher efficiency. Large grid-interactive, tracking flat-plate power systems and concentrator PV systems totaling about 10 MW, are already in operation. Collector technology development both flat-plate and concentrator, will continue under an extensive government and private industry partnership.

  15. Groundwater and Terrestrial Water Storage

    NASA Technical Reports Server (NTRS)

    Rodell, Matthew; Chambers, Don P.; Famiglietti, James S.

    2014-01-01

    Terrestrial water storage (TWS) comprises groundwater, soil moisture, surface water, snow,and ice. Groundwater typically varies more slowly than the other TWS components because itis not in direct contact with the atmosphere, but often it has a larger range of variability onmultiannual timescales (Rodell and Famiglietti, 2001; Alley et al., 2002). In situ groundwaterdata are only archived and made available by a few countries. However, monthly TWSvariations observed by the Gravity Recovery and Climate Experiment (GRACE; Tapley et al.,2004) satellite mission, which launched in 2002, are a reasonable proxy for unconfinedgroundwater at climatic scales.

  16. Atmosphere Mitigation in Precise Point Positioning Ambiguity Resolution for Earthquake Early Warning in the Western U.S.

    NASA Astrophysics Data System (ADS)

    Geng, J.; Bock, Y.; Reuveni, Y.

    2014-12-01

    Earthquake early warning (EEW) is a time-critical system and typically relies on seismic instruments in the area around the source to detect P waves (or S waves) and rapidly issue alerts. Thanks to the rapid development of real-time Global Navigation Satellite Systems (GNSS), a good number of sensors have been deployed in seismic zones, such as the western U.S. where over 600 GPS stations are collecting 1-Hz high-rate data along the Cascadia subduction zone, San Francisco Bay area, San Andreas fault, etc. GNSS sensors complement the seismic sensors by recording the static offsets while seismic data provide highly-precise higher frequency motions. An optimal combination of GNSS and accelerometer data (seismogeodesy) has advantages compared to GNSS-only or seismic-only methods and provides seismic velocity and displacement waveforms that are precise enough to detect P wave arrivals, in particular in the near source region. Robust real-time GNSS and seismogeodetic analysis is challenging because it requires a period of initialization and continuous phase ambiguity resolution. One of the limiting factors is unmodeled atmospheric effects, both of tropospheric and ionospheric origin. One mitigation approach is to introduce atmospheric corrections into precise point positioning with ambiguity resolution (PPP-AR) of clients/stations within the monitored regions. NOAA generates hourly predictions of zenith troposphere delays at an accuracy of a few centimeters, and 15-minute slant ionospheric delays of a few TECU (Total Electron Content Unit) accuracy from both geodetic and meteorological data collected at hundreds of stations across the U.S. The Scripps Orbit and Permanent Array Center (SOPAC) is experimenting with a regional ionosphere grid using a few hundred stations in southern California, and the International GNSS Service (IGS) routinely estimates a Global Ionosphere Map using over 100 GNSS stations. With these troposphere and ionosphere data as additional observations, we can shorten the initialization period and improve the ambiguity resolution efficiency of PPP-AR. We demonstrate this with data collected by a cluster of Real-Time Earthquake Analysis for Disaster mItigation (READI) network stations in southern California operated by UNAVCO/PBO and SOPAC.

  17. Solar/terrestrial physics

    NASA Astrophysics Data System (ADS)

    Ivanov-Kholodnyi, G. S.; Lotova, N. A.; Obridko, V. N.; Fel'Dshtein, Ia. I.; Fomichev, V. V.

    The history of the development of solar/terrestrial physics research at IZMIRAN (the Soviet Institute for the Study of Terrestrial Magnetism, the Ionosphere, and the Propagation of Radio Waves) is reviewed, and the activity of the Institute in organizing international solar/terrestrial physics research is examined. Particular attention is given to investigations of solar corpuscular radiation and its effect on the ionosphere; and to studies of auroras and the interplanetary medium.

  18. The impact of early Holocene Arctic shelf flooding on climate in an atmosphere-ocean-sea-ice model

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2013-11-01

    Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian Shelf became flooded before 7.5 ka BP and the coastline reached modern-day high stands at 5 ka BP. This area is currently known as a sea-ice production area and contributes significantly to the sea-ice exported from the Arctic through the Fram Strait. This leads to the following hypothesis: during times of rising sea levels, shelves become flooded, increasing sea-ice production on these shelves, increasing sea-ice volume and export through the Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an atmosphere-ocean-sea-ice coupled model of intermediate complexity (LOVECLIM). Our experiment on early Holocene Siberian Shelf flooding shows that in our model sea-ice production in the Northern Hemisphere increases (15%) and that sea-ice extent in the Northern Hemisphere increases (14%) but sea-ice export decreases (-15%) contrary to our hypothesis. The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land-ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the South, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic meridional overturning circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic Seas by up to -4 °C. We find that the flooding of the Siberian shelf resulting from an orbitally induced warming and related glacioeustatic sea level rise causes a Nordic Seas cooling feedback opposed to this warming.

  19. The impact of early Holocene Arctic Shelf flooding on climate in an atmosphere-ocean-sea-ice model

    NASA Astrophysics Data System (ADS)

    Blaschek, M.; Renssen, H.

    2013-07-01

    Glacial terminations are characterized by a strong rise in sea level related to melting ice sheets. This rise in sea level is not uniform all over the world, because regional effects (uplift and subsidence of coastal zones) are superimposed on global trends. During the early Holocene the Siberian Shelf became flooded before 7.5 ka BP and the coastline reached modern-day high stands at 5 ka BP. This area is currently known as a sea-ice production area and contributes significantly to the sea-ice exported from the Arctic through the Fram Strait. This leads to the following hypothesis: during times of rising sea levels, shelves become flooded, increasing sea-ice production on these shelves, increasing sea-ice volume and export through Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an ocean-sea-ice-atmosphere coupled model of intermediate complexity (LOVECLIM). Our results of an early Holocene Siberian Shelf flooding show that in our model the Northern Hemisphere sea-ice production is increased (15%) and that the Northern Hemisphere sea-ice extent increases (14%) contrary to our hypothesis with lower sea-ice export through Fram Strait (-15%). The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land-ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the south, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic Meridional Overturning Circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic Seas by up to -4 °C. We find that the flooding of the Siberian shelf as a result of an orbital induced warming, causing Northern Hemisphere ice sheets to melt and global sea level to rise, causes a Nordic Seas cooling feedback opposed to this warming.

  20. Application of 34S analysis for elucidating terrestrial, marine and freshwater ecosystems: Evidence of animal movement/husbandry practices in an early Viking community around Lake Mývatn, Iceland

    NASA Astrophysics Data System (ADS)

    Sayle, Kerry L.; Cook, Gordon T.; Ascough, Philippa L.; Hastie, Helen R.; Einarsson, Árni; McGovern, Thomas H.; Hicks, Megan T.; Edwald, Ágústa; Friðriksson, Adolf

    2013-11-01

    Carbon and nitrogen stable isotope ratios (δ13C and δ15N) have been used widely in archaeology to investigate palaeodiet. Sulphur stable isotope ratios (δ34S) have shown great promise in this regard but the potential of this technique within archaeological science has yet to be fully explored. Here we report δ34S, δ13C and δ15N values for 129 samples of animal bone collagen from Skútustaðir, an early Viking age (landnám) settlement in north-east Iceland. This dataset represents the most comprehensive study to date of its kind on archaeological material and the results show a clear offset in δ34S values between animals deriving their dietary resources from terrestrial (mean = +5.6 ± 2.8‰), freshwater (mean = -2.7 ± 1.4‰) or marine (mean = +15.9 ± 1.5‰) reservoirs (with the three food groups being significantly different at 2σ). This offset allows reconstruction of the dietary history of domesticated herbivores and demonstrates differences in husbandry practices and animal movement/trade, which would be otherwise impossible using only δ13C and δ15N values. For example, several terrestrial herbivores displayed enriched bone collagen δ34S values compared to the geology of the Lake Mývatn region, indicating they may have been affected by sea-spray whilst being pastured closer to the coast, before being traded inland. Additionally, the combination of heavy δ15N values coupled with light δ34S values within pig bone collagen suggests that these omnivores were consuming freshwater fish as a significant portion of their diet. Arctic foxes were also found to be consuming large quantities of freshwater resources and radiocarbon dating of both the pigs and foxes confirmed previous studies showing that a large freshwater radiocarbon (14C) reservoir effect exists within the lake. Overall, these stable isotope and 14C data have important implications for obtaining a fuller reconstruction of the diets of the early Viking settlers in Iceland, and may allow a clearer identification of the marine and/or freshwater 14C reservoir effects that are known to exist in human bone collagen.