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1

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

NASA Astrophysics Data System (ADS)

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.

Shaw, G. H.

2009-12-01

2

Introduction: On the Early Evolution of the Atmosphere of Terrestrial Planets: COST Action CM#0805  

NASA Astrophysics Data System (ADS)

The early setting and evolution of planetary atmospheres of rocky planets is a hot, but still immature research topic. A better understanding of the processes at work at that early epoch in the history of our solar system is certainly required, particularly at this historical juncture when we are just discovering the first exoplanets similar to Earth. These new worlds need to be put in their astrophysical and cosmochemical context, as we understand stars in the Cosmos as physical entities similar to the Sun, but with different masses, composition, and distinctive evolutionary stages. Exoplanets discovered so far exhibit large diversity as a direct consequence of having experienced differing births, evolutionary stages, and being subjected to stochastic processes in the early stages of their growth and evolution. To understand what is going on in the first stages of planetary evolution we must promote interdisciplinary research. That should yield better answers about the role played in planetary setting and evolution by processes such as accretion, chemical differentiation, outgassing, impacts, and the different energy fluxes from their host stars. Our current knowledge regarding the initial atmospheric evolution of the Earth is scarce. State-of-the-art analyses of primitive meteorites, together with returned asteroidal and cometary materials will be able to offer us more realistic starting chemical compositions for the primordial building blocks of terrestrial planets. Searching for chemical signatures in Earth-like exoplanets could be an interesting future field of research, and the matches found will provide new points to be compared with increasingly sophisticated atmospheric models. Then, new evidence in other worlds can contribute to a better understanding of the transition point from a hostile to a habitable world. To define the role of N in such context was one of the main goals to promote this COST CM0805 workshop.

Trigo-Rodríguez, Josep M.; Muller, Christian; Nixon, Conor; Raulin, François

3

Primitive Terrestrial Atmospheres  

NASA Astrophysics Data System (ADS)

A 23.3 year periodicity preserved in a 2500 million year old banded iron-formation is interpreted as reflecting the climatic influence of the lunar nodal tide, the signature of which has been detected in the modern climate. The lunar distance is deduced to have been 52 Earth radii. The influence of the lunar nodal tide is also detected in varves dating to 680 million years B.P. The implied history of Precambrian tidal friction is in excellent agreement with both more recent paleontological evidence and the long -term stability of the lunar orbit. The solar semidiurnal thermal tide was resonant with the natural period of the atmosphere when the day was (TURN)21.3 hours. This took place at the end of the Precambrian. The resonant atmospheric tide would have been large enough (.01 bar at the surface) to have influenced the weather. In contrast to lunar oceanic tides, the gravitational torque on the thermal tide accelerates the Earth's rotation rate; near resonance the opposing torques were comparable, so that the day may have been stabilized near 21.3 hours for much of the Precambrian. A sustained resonance does not conflict with the available evidence. Methane photochemistry in the primitive terrestrial atmosphere is studied using a detailed numerical model. Methane is oxidized cleanly and efficiently provided CO(,2) is more abundant than CH(,4). If CH(,4) and CO(,2) abundances are comparable, a large fraction of the methane present is polymerized, forming alkanes in the troposphere and polyacetylenes and nitriles in the upper atmosphere. Production of HCN from CH(,4) and N(,2) in the anaerobic atmosphere and its subsequent removal in rainwater could have been efficient; net production varying from .01% to 10% of the methane consumed. In the absence of a magnetic field, high ancient solar EUV and X-ray fluxes would have permitted an ocean of hydrogen to escape as a transsonic wind from a primordial accretionary greenhouse atmosphere in as little as 25 million years. The terrestrial magnetic field would have been strong enough to have prevented a freely flowing wind, reducing escape by one or two orders of magnitude with respect to an otherwise identical Venus.

Zahnle, Kevin John

1985-12-01

4

On the origin and early evolution of terrestrial planet atmospheres and meteoritic volatiles  

Microsoft Academic Search

A model is presented which attempts to synthesize previous efforts to place the origin of planetary atmosphere and meteorite volatiles in a context more fully integrated with concepts concerning the early (and evolving) astrophysical environment of the solar system. While the model combines familiar primordial components and theories, it differs from earlier approaches in that (1) the full ranges of

R. O. Pepin

1991-01-01

5

Terrestrial Planet Atmospheres and Biosignatures  

NASA Astrophysics Data System (ADS)

The search for terrestrial exoplanets - rocky worlds in orbit around stars other than the Sun - is one of humanity's most exciting science goals. The discovery of super Earths, terrestrial planets more massive than Earth, has opened a new era in exoplanet science, confirming the basic idea that our solar system is not the only planetary system to harbor terrestrial planets. Terrestrial exoplanets will expand planetary diversity, with masses and compositions likely very different from those found in our solar system. Most significantly, terrestrial exoplanets have the potential to host habitable environments on or below their solid surfaces, and are the most likely places beyond our solar system to search for signs of life. In the coming decades, instrumentation will be developed to expand our census of terrestrial exoplanets and directly characterize the atmospheres and biosignatures of these worlds. In the meantime, scientific progress in this field is made via extensive photochemical, climate, and radiative transfer modeling of terrestrial planetary environments together with remote sensing studies of solar system terrestrial planets, including Earth. This chapter provides an overview of terrestrial exoplanet atmosphere modeling techniques, a review of the scientific advances to date, and a discussion of outstanding questions and future directions.

Meadows, V.; Seager, S.

6

Very large plant and root traces from the Early to Middle Devonian: Implications for early terrestrial ecosystems and atmospheric p(CO2)  

NASA Astrophysics Data System (ADS)

Plant and root traces from the Fort Prével Member of the Battery Point Formation (late Early Devonian, Emsian), Gaspé Bay, Québec (Canada), are larger and more complex than previously postulated for land plants of this time. The traces are preserved as clay- and silt-lined casts in or near growth position and provide evidence that early vascular land plants achieved substantial stature (2 3 m) and were capable of deep rooting (to nearly 1 m). The root traces and alluvial deposits in which they occur suggest increased landscape stabilization and root system and paleosol morphologies that were influenced by a water-stressed, episodically energetic environment. Early Devonian plants of such large stature may have been partly responsible for initiation of a steep decline in atmospheric p(CO2), through organic carbon burial and accelerated terrestrial weathering.

Elick, Jennifer M.; Driese, Steven G.; Mora, Claudia I.

1998-02-01

7

Early Formation of Terrestrial Crust  

NASA Astrophysics Data System (ADS)

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 ?repsilonHf(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 ?repsilonHf(T) throughout the Hadean, although no positive ?repsilonHf(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, ?repsilono, 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. ?18O 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.

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

2007-12-01

8

Sulfuric acid aerosols in the atmospheres of the terrestrial planets  

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

9

Terrestrial sources and distribution of atmospheric sulphur  

PubMed Central

The general circulation model ECHAM has been coupled to a chemistry and sulphur cycle model to study the impact of terrestrial, i.e. mostly anthropogenic sulphur dioxide (SO2), sources on global distributions of sulphur species in the atmosphere. We briefly address currently available source inventories. It appears that global estimates of natural emissions are associated with uncertainties up to a factor of 2, while anthropogenic emissions have uncertainty ranges of about +/- 30 per cent. Further, some recent improvements in the model descriptions of multiphase chemistry and deposition processes are presented. Dry deposition is modelled consistently with meteorological processes and surface properties. The results indicate that surface removal of SO2 is less efficient than previously assumed, and that the SO2 lifetime is thus longer. Coupling of the photochemistry and sulphur chemistry schemes in the model improves the treatment of multiphase processes such as oxidant (hydrogen peroxide) supply in aqueous phase SO2 oxidation. The results suggest that SO2 oxidation by ozone (O3) in the aqueous phase is more important than indicated in earlier work. However, it appears that we still overestimate atmospheric SO2 concentrations near the surface in the relatively polluted Northern Hemisphere. On the other hand, we somewhat underestimate sulphate levels in these regions, which suggests that additional heterogeneous reaction mechanisms, e.g. on aerosols, enhance SO2 oxidation.

Lelieveld, J.; Roelofs, G.-J.; Ganzeveld, L.; Feichter, J.; Rodhe, H.

1997-01-01

10

Synthetic Spectra of Simulated Terrestrial Atmospheres Containing Possible Biomarker Gases  

Microsoft Academic Search

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

Trent L. Schindler; James F. Kasting

2000-01-01

11

ATMOSPHERIC CHANNEL EFFECTS ON TERRESTRIAL FREE SPACE OPTICAL COMMUNICATION LINKS  

Microsoft Academic Search

This paper illustrates the challenges imposed by the atmospheric channel on the design of a terrestrial laser communication link. The power loss due to scattering effect is described using the Kim\\/Kruse scattering model while the effect and the penalty imposed by atmospheric turbulence is highlighted by considering the bit error rate (BER) of an On- Off Keying modulated link in

W. Popoola; Z. Ghassemlooy; M. S. Awan; E. Leitgeb

12

Cosmic Rays and Terrestrial Planetary Atmospheres  

NASA Astrophysics Data System (ADS)

Planetary atmospheres are constantly irradiated by both photon and particle radiation sources. These high-energy particles strike the Earth's atmosphere, initiating an extensive air shower. As the air shower propagates deeper, it ionizes the atmosphere by producing charged secondary particles and photons. Increased ionization leads to changes in atmospheric chemistry, resulting in ozone depletion. This increases the flux of solar UVB radiation at the surface, which is potentially harmful to living organisms. Increased ionization affects the global electrical circuit, which could enhance the low-altitude cloud formation rate. Secondary particles such as muons and thermal neutrons produced as a result of hadronic interactions of the primary cosmic rays with the atmosphere are able to reach the ground, enhancing the biological radiation dose. I will present results obtained from a massive computer simulation using a Monte Carlo code CORSIKA to quantify these effects. Results are available in form of look-up tables for use by the scientific community.

Atri, D.

2011-12-01

13

Transport of ionizing radiation in terrestrial-like exoplanet atmospheres  

Microsoft Academic Search

The propagation of ionizing radiation through model atmospheres of terrestrial-like exoplanets is studied for a large range of column densities and incident photon energies using a Monte Carlo code we have developed to treat Compton scattering and photoabsorption. Incident spectra from parent star flares, supernovae, and gamma-ray bursts are modeled and compared to energetic particles in importance. Large irradiation events

David S. Smith; John Scalo; J. Craig Wheeler

2004-01-01

14

Space, atmospheric, and terrestrial radiation environments  

Microsoft Academic Search

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

J. L. Barth; C. S. Dyer; E. G. Stassinopoulos

2003-01-01

15

The Atmospheric and Terrestrial Mobile Laboratory (ATML).  

SciTech Connect

The ionospheric disturbance dynamo signature in geomagnetic variations is investigated using the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model. The model results are tested against reference magnetically quiet time observations on 21 June 1993, and disturbance effects were observed on 11 June 1993. The model qualitatively reproduces the observed diurnal and latitude variations of the geomagnetic horizontal intensity and declination for the reference quiet day in midlatitude and low-latitude regions but underestimates their amplitudes. The patterns of the disturbance dynamo signature and its source 'anti-Sq' current system are well reproduced in the Northern Hemisphere. However, the model significantly underestimates the amplitude of disturbance dynamo effects when compared with observations. Furthermore, the largest simulated disturbances occur at different local times than the observations. The discrepancies suggest that the assumed high-latitude storm time energy inputs in the model were not quantitatively accurate for this storm.

Zak, Bernard Daniel; Rahn, Thom (Los Alamos National Laboratory); Nitschke, Kim (Los Alamos National Laboratory); Ivey, Mark D.; Mora, Claudia (Los Alamos National Laboratory); McDowell, Nate (Los Alamos National Laboratory); Love, Steve (Los Alamos National Laboratory); Dubey, M. (Los Alamos National Laboratory); Michelsen, Hope A.; Guilderson, Tom (Lawrence Livermore National Laboratory); Schubert, William Kent; Costigan, Keeley (Los Alamos National Laboratory); Chylek, Petr (Los Alamos National Laboratory); Bambha, Ray P.; Roskovensky, John K.

2010-04-01

16

Early Terrestrial Arthropods: A Fragmentary Record  

Microsoft Academic Search

The earliest unequivocal terrestrial fossils are uppermost Silurian (Pridoli) myriapods, presumed to be pioneer decomposers. Descendants of their marine ancestors may be discernible in the Cambrian lobopod Aysheaia (recently challenged). Known euthycarcinoids are too late except as survivors from such a lobopod ancestry. Unique arthropods are also known from Cambrian and Ordovician lake deposits, but shed no light on origin

W. D. I. Rolfe

1985-01-01

17

Photochemistry of methane in the earth's early atmosphere  

Microsoft Academic Search

The photochemical behavior of methane in the early terrestrial atmosphere is investigated with a detailed model in order to determine how much CH4 might have been present and what types of higher hydroocarbons could have been formed. It is found that any primordial methane accumulated during the course of earth accretion would have been dissipated by photochemical reactions in the

J. F. Kasting; K. J. Zahnle; J. C. G. Walker

1983-01-01

18

Photochemistry in Terrestrial Exoplanet Atmospheres. II. H2S and SO2 Photochemistry in Anoxic Atmospheres  

NASA Astrophysics Data System (ADS)

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., H2S and SO2) 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 H2S and SO2 are chemically short-lived in virtually all types of atmospheres on terrestrial exoplanets, based on models of H2, N2, and CO2 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 H2-dominated atmospheres for a wide range of particle diameters (0.1-1 ?m), which is assumed as a free parameter in our simulations. In oxidized atmospheres composed of N2 and CO2, optically thick haze, composed of elemental sulfur aerosols (S8) or sulfuric acid aerosols (H2SO4), will form if the surface sulfur emission is two orders of magnitude more than the volcanic sulfur emission of Earth. Although direct detection of H2S and SO2 by their spectral features is unlikely, their emission might be inferred by observing aerosol-related features in reflected light with future generation space telescopes.

Hu, Renyu; Seager, Sara; Bains, William

2013-05-01

19

Atmospheres of early Noachian Mars  

NASA Astrophysics Data System (ADS)

We investigate the response of CO2-rich upper atmospheres of early Mars and Venus to the extreme solar EUV radiation from the young Sun by using a newly developed 1-D, multi-component, hydrodynamic thermosphere-ionosphere model (Tian et al. 2008a,b). It is shown that the weak gravity field of Mars, in combination with the strong solar EUV radiation from a young Sun, makes the thermal escape of atomic carbon and oxygen efficient. As a result, it would have been unlikely for the planet to have maintained a dense CO2 atmosphere during the early Noachian - prior to 4.1 billion years ago (Tian et al. 2008c). Without a dense CO2 atmosphere early Mars would have remained cold, until mid or late Noachian. In contrast, a CO2-rich atmosphere of early Venus was much more stable. Table of Contents References Tian, F., J.F. Kasting, H. Liu, R.G. Roble, Hydrodynamic planetary thermosphere model:. 1. The response of the Earth's thermosphere to extreme solar EUV conditions and the significance of adiabatic cooling, J. Geophys. Res., 113, E05008 doi:10.1029/2007JE002946 (2008a) Tian, F., S.C. Solomon, L. Qian, J. Lei, R.G. Roble, Hydrodynamic planetary thermosphere model: 2. coupling of an electron transport/energy deposition model, J. Geophys. Res., 113, E07005, doi:10.1029/2007JE003043 (2008b). Tian, F., J.F. Kasting, S.C. Solomon, Fast thermal escape of carbon and oxygen from a dense, CO2-ruch early Martian atmosphere. Science (2008c), under review.

Tian, Feng

2008-09-01

20

Habitability of Terrestrial Planets in the Early Solar System  

NASA Astrophysics Data System (ADS)

The Protoearth, Mars, Venus, and the Moon-forming impactor were potentially habitable in the early solar system. The interiors of larger asteroids had habitable circulating water. To see when the inner solar system became continuously habitable, one needs to consider the most dangerous events and the safest refugia from them. Early geochemical and accretionary processes set the subsequent silicate planet reservoirs and hence hydrospheric and atmospheric masses. The moon-forming impact made the Moon and the Earth sterile bodies. Following the impact, the Earth passed through a rock-vapor atmosphere on the scale of 1000s of years and an internally heated steam greenhouse on the scale of 2 m.y. Minerals bearing the principle volatiles (water, Cl, and CO2) were stable at the Earth's surface by the time it cooled to 800K. The mass of reactable shallow material was insufficient to contain the available water and CO2. Habitable conditions were established after CO2 could be deeply subducted into the mantle. Vast quantities of H2 were vented during accretion and after the moon-forming impact and eventually lost to space. It is unknown whether significant amounts of this gas were present when the Earth's surface cooled into the habitable range. The moon remained sterile because its interior is essentially devoid of water. The mantle of the Earth, in contrast, cannot hold the available water, leaving the excess to form oceans. Nitrogen may behave similarly with the excess going into the air. Impacts of large asteroids (and comets) were an ever-present danger on otherwise habitable planets. The safest niche on planets was kilometer or deeper crustal rocks habitable by thermophiles. It is inevitable that several objects, which would have left only thermophile survivors, struck the Earth. Such events were so infrequent that the conditions of such a bottleneck should not be confused with conditions for the origin of life. An alternative refugium involves ejection of life within rock fragments and return of such fragments to the surface of the home planet or transfer to another habitable planet. Mars and the larger asteroids were habitable first and provide likely sources of seed and also testable places to look for preserved evidence. Extant terrestrial life appears to have passed through thermophile bottlenecks. There are subtle hints of space transfer. The need of extant life for Ni may be a vestige of life on a young planet covered with ultramafic rocks.

SLEEP, N. H.

2001-12-01

21

Contribution of natural terrestrial sources to the atmospheric chloroform budget  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

22

Simulating the carbon flux between the terrestrial environment and the atmosphere  

Microsoft Academic Search

A Terrestrial C Cycle model that is incorporated in the Integrated Model to Assess the Greenhouse Effect (IMAGE 2.0) is described. The model is a geographically explicit implementation of a model that simulates the major C fluxes in different compartments of the terrestrial biosphere and between the biosphere and the atmosphere. Climatic parameters, land cover and atmospheric C concentrations determine

K. Klein Goldewijk; J. G. Minnen; G. J. J. Kreileman; M. Vloedbeld; R. Leemans

1994-01-01

23

Terrestrial biogeochemical cycles: global interactions with the atmosphere and hydrology  

NASA Astrophysics Data System (ADS)

Ecosystem scientists have developed a body of theory to predict the behaviour of biogeochemical cycles when exchanges with other ecosystems are small or prescribed. Recent environmental changes make it clear that linkages between ecosystems via atmospheric and hydrological transport have large effects on ecosystem dynamics when considered over time periods of a decade to a century, time scales relevant to contemporary humankind. Our ability to predict behaviour of ecosystems coupled by transport is limited by our ability (1) to extrapolate biotic function to large spatial scales and (2) to measure and model transport. We review developments in ecosystem theory, remote sensing, and geographical information systems (GIS) that support new efforts in spatial modeling. A paradigm has emerged to predict behaviour of ecosystems based on understanding responses to multiple resources (e.g., water, nutrients, light). Several ecosystem models couple primary production to decomposition and nutrient availability using the above paradigm. These models require a fairly small set of environmental variables to simulate spatial and temporal variation in rates of biogeochemical cycling. Simultaneously, techniques for inferring ecosystem behaviour from remotely measured canopy light interception are improving our ability to infer plant activity from satellite observations. Efforts have begun to couple models of transport in air and water to models of ecosystem function. Preliminary work indicates that coupling of transport and ecosystem processes alters the behaviour of earth system components (hydrology, terrestrial ecosystems, and the atmosphere) from that of an uncoupled mode.

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

1991-08-01

24

Early martian environments: the Antarctic and other terrestrial analogs.  

PubMed

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. PMID:11537365

Wharton, R A; McKay, C P; Mancinelli, R L; Simmons, G M

1989-01-01

25

Morphological Biosignatures in Early Terrestrial and Extraterrestrial Materials  

NASA Astrophysics Data System (ADS)

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.

Westall, Frances

26

Morphological Biosignatures in Early Terrestrial and Extraterrestrial Materials  

NASA Astrophysics Data System (ADS)

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.

Westall, Frances

2008-03-01

27

Exchange of condensed matter among the outer and terrestrial protoplanets and the effect on surface impact and atmospheric accretion  

SciTech Connect

The potential contribution of volatile material to planetary atmospheres from comet impact is presently estimated on the basis of a scenario of extensive gravitational scattering of icy planetesimals from the other planets and cometary nuclei in the early and late phase of the bombardment process. In the earth's case, the cometary water is sufficient to compete with the water contained in the nonvolatile planetesimals condensed in the region of the terrestrial planets; the same consideration could be applied to Mars and Venus, although it is not yet clear how the cometary chemical compositions may have affected the evolution of early planetary atmospheres. 52 references.

Ip, W.H.; Fernandez, J.A.

1988-04-01

28

Terrestrial record of methane hydrate dissociation in the Early Cretaceous  

Microsoft Academic Search

Reconstruction of changing C isotopic composition of Early Cretaceous atmospheric CO2 from fossilized C3 vascular land-plant tissue revealed a brief and striking negative excursion (Delta ≈ -50\\/00) in atmospheric delta13C, followed by a rapid positive compensation (Delta ≈ +50\\/00) during the Aptian (ca. 117 Ma). Mass-balance calculations show that dissociation of a small amount of methane gas hydrate is the

A. Hope Jahren; Nan Crystal Arens; Gustavo Sarmiento; Javier Guerrero; Ronald Amundson

2001-01-01

29

Photochemistry in Terrestrial Exoplanet Atmospheres. I. Photochemistry Model and Benchmark Cases  

NASA Astrophysics Data System (ADS)

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., CH4 and CO2) 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 CO2-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.

Hu, Renyu; Seager, Sara; Bains, William

2012-12-01

30

Evolution of the Atmospheres of Terrestrial Planets : Focus on Mars and Venus.  

NASA Astrophysics Data System (ADS)

A simple atmosphere-interior coupling has been implemented for Venus under stagnant lid convection regime; the atmosphere gains water from the degassing, through a parameterized model of mantle convection, including volatile exchanges between the mantle and the atmosphere (additionally, the mean depth of partial melting is taken into account), and a radiative-convective atmosphere model computes the temperature at the planet's surface. This coupling suggests that a strong links exist between inner (the solid part) and outer layers of the planets. It also seems essential to study the atmospheric escape which could be a major parameter constraining the surface conditions during the early evolution of terrestrial planets. The initial model of the escape we used is very basic, so we develop this aspect to try and see if realistic results may be obtained with a more complete approach. Thus we use an energy-limited approach to model the escape of hydrogen out of the primitive atmosphere and its entrainment of rare gazes. We compare the evolution of rare gaze depletion and the final (after 4.6 Gy) isotopic ratios to those measured by Venera missions. Results show that depending on the extent of the exosphere and the temperature it reaches, it is possible to explain the present isotopic ratios with only the hydrodynamic escape, especially with hot (such as 500 K to 1500 K) and extended (4 to 8 times the size of the planet) exospheres. Since hydrodynamic escape mostly takes place during the first hundreds of million years, other processes for atmospheric escape have been considered in order to quantify the loss of volatiles during later periods. Using data from Mars Express and several models such as ones created by Leblanc (2001) or Chassefière, Leblanc and Langlais (2006), a model for the evolution of Martian atmosphere and volatiles has been set up. Crust production rates from a model by Breuer et al. (2006) are taken as input for the mantle degassing and the evolution of the content in water, CO2 and SO2 of the atmosphere is studied through different scenarios. We first focused on the present situation as described by available data such as ones from Mars Express in order to study the late evolution of the Martian atmosphere. It appears that a production of at least 0.05 to 0.1 km3/year is needed for the atmosphere to be at steady state. Our second interest is to have a view of possible evolutions of the Martian environment over the whole history of the planet and to try to relate it to specific features discovered, and especially with sulfate formations detected by the OMEGA spectrometer.

Gillmann, C.; Lognonné, P.; Chassefière, E.

2006-12-01

31

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

SciTech Connect

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}.

King, A.W.; Post, W.M.; Wullschleger, S.D. [Oak Ridge National Lab., TN (United States)

1995-06-01

32

Effects of atmospheric ammonia (NH 3) on terrestrial vegetation: a review  

Microsoft Academic Search

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

S. V Krupa

2003-01-01

33

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

Microsoft Academic Search

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,

Julianna Eileen Fessenden

1999-01-01

34

Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake  

NASA Astrophysics Data System (ADS)

The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. The smaller efficiency of the oceanic carbon uptake under an interactive atmosphere is due to the back flux of CO2 that occurs when atmospheric CO2 is reduced. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively, for pCO2 sensitivities of the terrestrial carbon storage in the middle range of the C4MIP models (Friedlingstein et al., 2006). For such sensitivities, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization originates, on timescales longer than decades, not from the atmosphere but from the terrestrial biosphere.

Oschlies, A.

2009-08-01

35

A Hydrogen-Rich Early Earth Atmosphere  

Microsoft Academic Search

We show that the escape of hydrogen from early Earth's atmosphere likely occurred at rates slower by two orders of magnitude than previously thought. The balance between slow hydrogen escape and volcanic outgassing could have maintained a hydrogen mixing ratio of more than 30%. The production of prebiotic organic compounds in such an atmosphere would have been more efficient than

Feng Tian; Owen B. Toon; Alexander A. Pavlov; H. De Sterck

2005-01-01

36

Atmospheric mercury pollution due to losses of terrestrial carbon pools?  

Microsoft Academic Search

Plants accumulate significant amounts of atmospheric mercury (Hg) in aboveground biomass, likely sequestering over 1,000 Mg\\u000a of atmospheric Hg every year. This large mercury uptake could be strong enough to affect tropospheric Hg levels and might\\u000a be partially responsible for seasonal variations in atmospheric Hg observed at Mace Head, Ireland. The fluctuations of Hg\\u000a concentrations coincide temporally with the annual oscillation

Daniel Obrist

2007-01-01

37

Comment on Rayleigh-Scattering Calculations for the Terrestrial Atmosphere  

NASA Astrophysics Data System (ADS)

It is shown that, for a given surface pressure, the atmospheric vertical temperature profile has a negligible influence on the Rayleigh optical depth. This contradicts the Bucholtz recommendation for the use of values that vary with air mass type. The influence of atmospheric water vapor amount on the Rayleigh optical depth is also investigated.

On, Ois-Marie

1998-01-01

38

Proposed Reference Models for Atomic Oxygen in the Terrestrial Atmosphere.  

National Technical Information Service (NTIS)

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.

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

1989-01-01

39

The Early Origins of Terrestrial C4 Photosynthesis  

NASA Astrophysics Data System (ADS)

The C4 photosynthetic pathway is a series of structural and biochemical modifications around the more primitive C3 pathway that improve the photosynthetic efficiency under specific climatic conditions. Hence, the origin and subsequent geographical expansion of the C4 plants likely reflects a record of climate change. Multiple paleoatmospheric pCO2 proxies indicate a critical CO2 threshold was breached 30 Ma, that potentially selected for CO2-concentrating mechanisms to overcome photorespiratory stresses imposed on the basic C3 pathway. Details of the C4 pathway's earliest origins remain enigmatic given the paucity of the geologic record. Nonetheless, ?13C proxy records from paleosol carbonates, ungulate teeth, and plant-derived compounds indicate C4 plants likely represented an important component of plant biomass by the Early Miocene. Low CO2 levels appear to be a precondition for the development of the C4 photosynthetic pathway; however, comparisons of ?13C proxy records indicate that the timing of C4 geographical expansion was not globally synchronous, and thus point toward more regional controls on the development of C4-dominated ecosystems. Terrestrial and marine records indicate that continental aridity and wind strength increased during the Late Miocene. These conditions would have likely increased fire occurrence and fire intensity leading to the clearing of large tree stands and the expansion of C4 grasses in warm-season precipitation regimes.

Tipple, Brett J.; Pagani, Mark

2007-05-01

40

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

SciTech Connect

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.

Hu Renyu; Seager, Sara; Bains, William, E-mail: hury@mit.edu [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)] [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2012-12-20

41

The Terrestrial Fossil Organic Matter Record of Global Carbon Cycling: A Late Paleozoic through Early Mesozoic Perspective  

NASA Astrophysics Data System (ADS)

The carbon isotope composition of terrestrial fossil organic matter (?13Corg) has been widely used as a proxy of global carbon cycling and to reconstruct perturbations to the ocean-atmosphere carbon budget. The degree to which terrestrial ?13Corg records local to regional environmental conditions versus the evolution of the global carbon cycle has been highly debated. The high-resolution (104 to 106 m.y.) terrestrial ?13Corg record presented here defines a long-term trend through the latest Devonian to Late Triassic that reveals significant and systematic variations that track independently inferred changes in climate, paleo-atmospheric pCO2, and major restructuring in paleotropical flora. This newly derived record is based on 350 carbon isotope analyses of compressed and permineralized plants, cuticle, charcoal and coal (including vitrinite and fusinite) collected from paleo-wetland mudstones and claystones, claystone-filled abandoned fluvial channels, floodplain mudstones, and ephemeral lacustrine deposits at paleo-tropical to paleo-temperate latitudes. Morphologic and geochemical analysis of contemporaneous paleosols and fluvial-alluvial deposits allow for correlation of terrestrial ?13Corg values to reconstructed paleo-environmental conditions. Terrestrial ?13Corg values of contemporaneous fossil organic matter exhibit systematic inter- and intra-basinal variation of up to 2‰ associated with differences in paleo-precipitation and burial history, and geomorphic position within depositional basins and paleo-fluvial systems. Variation in ?13Corg by organic matter type is minimal to less than 1.5‰; specifically, charcoal ?13Corg values overlap to are slightly less negative than those of thermally less mature organic components analyzed. Overall, variation within contemporaneous populations is significantly less than defined by the long-term terrestrial ?13Corg record. Moreover, paleo-floral pi/pa ratios, an established proxy of water-use efficiency of plant growth, estimated from measured terrestrial ?13Corg values and contemporaneous marine carbonate ?13C values define a relatively consistent and narrow range (0.45 to 0.6) throughout the 150 million year interval within each depositional basin, regardless of landscape or stratigraphic position. Their narrow range in conjunction with the statistically significant long-term ?13Corg trend indicates that local to regional environmental effects on ?13Corg were secondary to extrabasinal influences such as the carbon isotopic composition of the paleo-atmosphere. This suggests that the long-term terrestrial ?13Corgrecord archives first-order variations in atmospheric ?13C throughout the Late Paleozoic and Early Mesozoic.

Montanez, I. P.

2006-12-01

42

Vegetated terrestrial ecosystems are large sources of Hg to the atmosphere  

NASA Astrophysics Data System (ADS)

Industrial processes, especially coal combustion and metal refining, have led to significant releases of Hg to the atmosphere during the last century. It has been hypothesized that a large percentage of this Hg has been deposited to terrestrial ecosystems via wet and dry deposition. Recent measurements of net Hg exchange between soils and the atmosphere indicate that terrestrial ecosystems are a source of Hg to the atmosphere, rather than the hypothesized sink, but very few measurements have been performed over vegetated terrestrial ecosystems. The objective of this study was to continuously measure net Hg exchange between a grassland ecosystem and the atmosphere during an entire year using the Ecologically Controlled Enclosed Lysimeter Laboratory (EcoCELLs) at Desert Research Institute. The EcoCELLs are unique open flow gas exchange systems that allow for the measurement of whole-ecosystem gas fluxes from large soil-plant monoliths under precisely controlled environmental conditions. Our results indicate that daily net ecosystem Hg exchange was positive (i.e., net Hg loss from the ecosystem to the atmosphere) during most of the year with the exception of the winter months when we observed net deposition of Hg to the ecosystem. Soil Hg fluxes only contributed between 10 % and 25 % of measured ecosystem Hg emissions. Ecosystem Hg fluxes showed pronounced diel patterns with higher daytime Hg emissions compared to nighttime Hg fluxes indicating that solar radiation, temperature, and evapotranspiration are important factors controlling Hg emissions. The cumulative annual Hg budget over one year indicated that the grassland ecosystem in our study was a relatively large Hg source to the atmosphere, ranging from 20 to 100 ? g Hg m-2. Based on this study it appears that grassland ecosystems are sources of Hg to the atmosphere during most of the year, with vegetation greatly enhancing total emissions, possibly through transpiration, and that vegetated terrestrial ecosystems are large, yet still poorly quantified, sources of Hg to the atmosphere.

Obrist, D.; Gustin, M. S.; Arnone, J. A.; Schorran, D. E.; Verburg, P. S.; Johnson, D. W.

2003-12-01

43

Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake  

NASA Astrophysics Data System (ADS)

The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively. On longer than decadal timescales, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization may not come from the atmosphere but from the terrestrial biosphere.

Oschlies, A.

2009-04-01

44

In situ observations of the atmospheres of terrestrial planetary bodies  

NASA Astrophysics Data System (ADS)

Direct observations of planetary atmospheres are scarce and significantly more data are needed for the understanding of their behavior. The principal theme of this dissertation is the exploration of planetary atmospheres by means of in situ observations, focusing on investigations performed by payloads operating on the planetary surface. The contextual frame includes the whole palette of planetary exploration including definition of scientific objectives, observational strategies, scientific payload and data analysis, as well as development of technological solutions and simulation models for planetary missions. Thus approach also led to the initiation of the planetary missions MetNet and NetLander to Mars. This work contributes to both in situ atmospheric observations and atmospheric modeling, which are strongly intertwined. Modeling efforts require observations to give solid background and foundation for the simulations, and on the other hand, definition of observational strategies and instrumentation gets guidance from modeling efforts to optimize the use of mission resources, as is successfully demonstrated in this dissertation. The dissertation consists of Summary and nine original scientific publications. Publications 1 to 7 and Summary address the development of new atmospheric science payloads for exploration missions to Mars and Titan, a Saturnian moon. Actual and planned missions included are the Mars-96 Program and its Small Surface Stations and Penetrators during the years 1988-1996, PPI/HASI onboard the Cassini/Huygens spacecraft to Saturn and its moon Titan in 1989-2005, the MET-P payload onboard the Mars Polar Lander in 1997-1999, the BAROBIT instrument for the Beagle 2 lander in 2001-2003, the NetLander Mars Mission in 1997-2001 and the ongoing Mars MetNet Mission, started in 2000. Specifically, Publication 4 reviews the sensor qualification process that facilitated the use of new type of atmospheric sensors at Mars, while Publications 2 and 7, as well as Summary, address the highly successful determination of the Titan atmospheric pressure profile. Publication 8 combines in situ observations and simulations by analyzing Mars Pathfinder measurements with the help of a Martian mesoscale atmospheric model. Finally, in Publication 9 the effect of airborne dust and CO 2 on the radiative transfer in the Martian atmosphere is assessed and a new radiative transfer paramerization scheme for the mesoscale model is introduced.

Harri, Ari-Matti

2005-11-01

45

Sensitivity of terrestrial ecosystems to elevated atmospheric COâ: Comparisons of model simulation studies to COâ effect  

Microsoft Academic Search

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 COâ. 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

1995-01-01

46

Absorption and photodissociation in the Schumann-Runge bands of molecular oxygen in the terrestrial atmosphere  

Microsoft Academic Search

The penetration in the terrestrial atmosphere of solar radiation corresponding to the spectral range of the Schumann-Runge bands of molecular oxygen was analyzed between 1750 and 2050. The variation of the absorption cross section with temperature was taken into account and it is shown that average O2 absorption cross sections cannot lead to the computation of the molecular oxygen photodissociation

G. Kockarts

1976-01-01

47

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

National Technical Information Service (NTIS)

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 ...

R. A. Houghton

1998-01-01

48

The ?182W composition of early Archaean terrestrial rocks (Invited)  

NASA Astrophysics Data System (ADS)

The contrasting lithophile and siderophile behaviours of its daughter and short-lived (t1/2 ~9Ma) parent has made the 182Hf-182W isotope system invaluable in determining the timescales of planetary core formation. However, Hf is also considerably less incompatible than W in many melting and crystallisation scenarios in purely silicate systems. Thus the 182Hf-182W pair has also been used with success in examining the evolution of the silicate portion of planetesimals. Recent ?142Nd data demonstrate that very early fractionation events are recorded in the isotopic signatures of samples from Isua, Greenland. This observation suggests that W isotopic measurements could also be used to yield insights into the Earth’s earliest silicate differentiation. Notably one interpretation of terrestrial 142Nd-143Nd isotope systematics invokes the formation of an enriched, deep reservoir within the first 30Ma of Earth’s history. It has further been suggested that the contrast between ?142Nd in the most ancient Greenland samples and present day mantle (~20ppm) is a result of partial remixing between this hidden reservoir and convecting mantle at ~3.5Ga. If so, the Greenland samples derived from mantle that pre-dates this event would be expected to show a difference in ?182W relative to modern mantle. Thus we have made high precision ?182W measurements on some Isua samples with clear 142Nd excesses. Notably, we document significant differences between these samples and modern mantle values. We have not been alone in exploring potential ?182W anomalies in Greenland samples [1, 2] but our analyses are considerably more precise than previous studies and we are the first to document significant differences. However, the magnitude of the difference in our ?182W is smaller than predicted for a remixing scenario of early enriched reservoir with the convecting mantle that can account for the difference in ?142Nd between Isua and present mantle. We thus reemphasise the conclusions of [1], that this change in ?142Nd with time does not provide good evidence for the existence of an early enriched reservoir. We further note that the addition of small amounts of primitive chondritic material after core formation, as suggested by the late veneer model, is sufficient to account for the lowering of ?182W from values we report in the Isua samples to present day. [1] T. Iizuka et al. (2010), EPSL 291, 189-200. [2] F. Moynier et al. (2010), PNAS 107, 10810-10814.

Willbold, M.; Elliott, T.; Moorbath, S.

2010-12-01

49

Atmospheres on the terrestrial planets: Clues to origin and evolution  

Microsoft Academic Search

Earth, Venus and Mars reached their final sizes in the first 100 Myr or so of solar system history. For part of that time the growing planets and the materials forming them were immersed in the Sun-like gases of the solar nebula, and so one would expect that their early volatile inventories were acquired from the nebula. But the compositions of

Robert O. Pepin

2006-01-01

50

Radiative transfer code SHARM for atmospheric and terrestrial applications  

NASA Astrophysics Data System (ADS)

An overview of the publicly available radiative transfer Spherical Harmonics code (SHARM) is presented. SHARM is a rigorous code, as accurate as the Discrete Ordinate Radiative Transfer (DISORT) code, yet faster. It performs simultaneous calculations for different solar zenith angles, view zenith angles, and view azimuths and allows the user to make multiwavelength calculations in one run. The ?-M method is implemented for calculations with highly anisotropic phase functions. Rayleigh scattering is automatically included as a function of wavelength, surface elevation, and the selected vertical profile of one of the standard atmospheric models. The current version of the SHARM code does not explicitly include atmospheric gaseous absorption, which should be provided by the user. The SHARM code has several built-in models of the bidirectional reflectance of land and wind-ruffled water surfaces that are most widely used in research and satellite data processing. A modification of the SHARM code with the built-in Mie algorithm designed for calculations with spherical aerosols is also described.

Lyapustin, A. I.

2005-12-01

51

Synchronized Terrestrial-Atmospheric Deglacial Records Around the North Atlantic  

Microsoft Academic Search

On the basis of synchronization of three carbon-14 (14C)-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 ± 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising delta14C values, is evident in all records and

Svante Bjorck; Bernd Kromer; Sigfus Johnsen; Ole Bennike; Dan Hammarlund; Geoffrey Lemdahl; Goran Possnert; Tine Lander Rasmussen; Barbara Wohlfarth; Claus Uffe Hammer; Marco Spurk

1996-01-01

52

Carbon Fluxes Between the Atmosphere, Terrestrial, and River Systems Across a Glacier-Dominated Landscape in Southcentral Alaska  

NASA Astrophysics Data System (ADS)

The coastal Gulf of Alaska region is experiencing rapid and accelerating changes due to local and regional warming. Predicted high latitude warming may result in rapid recession of glaciers with subsequent changes in river discharge, nutrient fluxes into the rivers, shifts in landscape vegetation cover, and altered CO2 fluxes affecting the regional carbon balance. As glaciers recede an increase in glacier-dominated river discharge and a change in seasonality of the river discharge are expected. Recently deglaciated landscapes will, over time, be occupied by a succession of vegetation cover that are likely to alter the fluxes of carbon both between the atmosphere and terrestrial ecosystems, and between terrestrial ecosystems and stream and river systems. As the landscape evolves from deglaciated forelands it is expected that there is low to no CO2 fluxes between the atmosphere and the recently deglaciated landscape, as well as dissolved organic and inorganic carbon inputs into rivers and streams. These recently deglaciated landscapes will transition to early successional plant species and on towards mature spruce forests. Each transitional terrestrial ecosystem will have different carbon cycling between the atmosphere, terrestrial, and aquatic systems until the mature spruce forests which is expected to have high carbon uptake and sequestration as well as increased inputs of dissolved organic and inorganic carbon into the rivers and streams. A new research project was initiated in the summer of 2011 focusing on glacier-dominated landscapes within the Wrangell-St. Elias National Park and Preserve in southcentral Alaska with the objective to quantify how the transition from deglaciated forelands to mature spruce forests (a successional sequence) alters the patterns and magnitudes of CO2 exchange, the dissolved carbon inputs from terrestrial to aquatic systems and the extent to which these are manifested due to changes in glacier coverage. We seek to examine present-day carbon cycling along a vegetation successional sequence and plan to use a space-for-time substitution to make predictions about the future evolution of carbon cycling between the atmosphere, terrestrial landscape, and the river and stream systems This year we have established a 30m eddy covariance tower in a mature spruce forest to investigate the magnitude and patterns of carbon exchange between the atmosphere and terrestrial ecosystem as well as water sampling from adjacent rivers and streams to analyze for dissolved organic and inorganic carbon fluxes from the forested ecosystem into the river and stream systems. High rates of carbon sequestration into the mature spruce forests indicate that these forests along the glacier-dominated Copper River watershed are important sinks for carbon and may be contributing large amounts of inorganic carbon to the rivers which are transported downstream to and eventually into the marine ecosystem of the Gulf of Alaska.

Zulueta, R. C.; Welker, J. M.; Tomco, P. L.

2011-12-01

53

Synchronized terrestrial-atmospheric deglacial records around the North Atlantic  

SciTech Connect

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.

Bjoerck, S.; Rasmussen, T.L. [Univ. of Copenhagen (Denmark); Kromer, B. [Heidelberg Academy of Sciences (Germany)] [and others

1996-11-15

54

Synchronized Terrestrial-Atmospheric Deglacial Records Around the North Atlantic  

NASA Astrophysics Data System (ADS)

On the basis of synchronization of three carbon-14 (14C)-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 ± 80 years before the present. A 150-year-long cooling in the early Preboreal, associated with rising ?14C 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 the inhibited the strength of the North Atlantic heat conveyor, although the Younger Dryas may have begun as an anomalous meltwater event.

Bjorck, Svante; Kromer, Bernd; Johnsen, Sigfus; Bennike, Ole; Hammarlund, Dan; Lemdahl, Geoffrey; Possnert, Goran; Lander Rasmussen, Tine; Wohlfarth, Barbara; Uffe Hammer, Claus; Spurk, Marco

1996-11-01

55

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

NASA Astrophysics Data System (ADS)

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.

Sicre, M.; Ezat, U.

2006-12-01

56

Variations in the predicted spatial distribution of atmospheric nitrogen deposition and their impact on carbon uptake by terrestrial ecosystems  

Microsoft Academic Search

Widespread mobilization of nitrogen into the atmosphere from industry, agriculture, and biomass burning and its subsequent deposition have the potential to alleviate nitrogen limitation of productivity in terrestrial ecosystems, and may contribute to enhanced terrestrial carbon uptake. To evaluate the importance of the spatial distribution of nitrogen deposition for carbon uptake and to better quantify its magnitude and uncertainty NOy-N

Elisabeth A. Holland; B. H. Braswell; Jean-François Lamarque; Alan Townsend; James Sulzman; Jean-François Müller; Frank Dentener; Guy Brasseur; H. Levy; Joyce E. Penner; Geert-Jan Roelofs

1997-01-01

57

In search of the missing carbon sink: a model of terrestrial biospheric response to land-use change and atmospheric CO2  

Microsoft Academic Search

Estimates of the net exchange of carbon between the terrestrial biosphere and the atmosphere may be too large because the models of carbon release from changes in land use do not allow for enhanced carbon assimilation by the terrestrial biosphere in response to increasing atmospheric CO2. We address this deficiency with a model of terrestrial biosphere that includes both ecosystem

Anthony W. King; William R. Emanuel; Stan D. Wullschleger; Wilfred M. Post

1995-01-01

58

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

PubMed

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

Summers, David P; Khare, Bishun

2007-04-01

59

Nested atmospheric inversion for the terrestrial carbon sources and sinks in China  

NASA Astrophysics Data System (ADS)

In this study, we establish a nested atmospheric inversion system with a focus on China using the Bayesian method. The global surface is separated into 43 regions based on the 22 TransCom large regions, with 13 small regions in China. Monthly CO2 concentrations from 130 GlobalView sites and 3 additional China sites are used in this system. The core component of this system is an atmospheric transport matrix, which is created using the TM5 model with a horizontal resolution of 3° × 2°. The net carbon fluxes over the 43 global land and ocean regions are inverted for the period from 2002 to 2008. The inverted global terrestrial carbon sinks mainly occur in boreal Asia, South and Southeast Asia, eastern America and southern South America. Most China areas appear to be carbon sinks, with strongest carbon sinks located in Northeast China. From 2002 to 2008, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2002. The inter-annual variation (IAV) of the land sinks shows remarkable correlation with the El Niño Southern Oscillation (ENSO). The terrestrial carbon sinks in China also show an increasing trend. However, the IAV in China is not the same as that of the globe. There is relatively stronger land sink in 2002, lowest sink in 2006, and strongest sink in 2007 in China. This IAV could be reasonably explained with the IAVs of temperature and precipitation in China. The mean global and China terrestrial carbon sinks over the period 2002-2008 are -3.20 ± 0.63 and -0.28 ± 0.18 PgC yr-1, respectively. Considering the carbon emissions in the form of reactive biogenic volatile organic compounds (BVOCs) and from the import of wood and food, we further estimate that China's land sink is about -0.31 PgC yr-1.

Jiang, F.; Wang, H. W.; Chen, J. M.; Zhou, L. X.; Ju, W. M.; Ding, A. J.; Liu, L. X.; Peters, W.

2013-08-01

60

Nested atmospheric inversion for the terrestrial carbon sources and sinks in China  

NASA Astrophysics Data System (ADS)

In this study, we establish a~nested atmospheric inversion system with a focus on China using the Bayes theory. The global surface is separated into 43 regions based on the 22 TransCom large regions, with 13 small regions in China. Monthly CO2 concentrations from 130 GlobalView sites and a Hong Kong site are used in this system. The core component of this system is atmospheric transport matrix, which is created using the TM5 model with a horizontal resolution of 3° × 2°. The net carbon fluxes over the 43 global land and ocean regions are inverted for the period from 2002 to 2009. The inverted global terrestrial carbon sinks mainly occur in Boreal Asia, South and Southeast Asia, eastern US and southern South America (SA). Most China areas appear to be carbon sinks, with strongest carbon sinks located in Northeast China. From 2002 to 2009, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2002. The inter-annual variation (IAV) of the land sinks shows remarkable correlation with the El Niño Southern Oscillation (ENSO). However, no obvious trend is found for the terrestrial carbon sinks in China. The IAVs of carbon sinks in China show strong relationship with drought and temperature. The mean global and China terrestrial carbon sinks over the period 2002-2009 are -3.15 ± 1.48 and -0.21 ± 0.23 Pg C yr-1, respectively. The uncertainties in the posterior carbon flux of China are still very large, mostly due to the lack of CO2 measurement data in China.

Jiang, F.; Wang, H.; Chen, J. M.; Ju, W.; Ding, A.

2013-01-01

61

A proxy for the SEP incoming in the high-latitude terrestrial atmosphere  

NASA Astrophysics Data System (ADS)

Solar Energetic Particle (SEP) events are able to increase NOX and HOX species inside the terrestrial polar cap regions. The low background values of OH molecules during the winter Polar mesosphere makes the atmospheric response to the external forcing easier to single out (Storini and Damiani, ICRC'07 - Merida - Mexico). More precisely, the short life of HOx species allows the hydrogen radicals to follow the SEP incoming in the terrestrial atmosphere, being their variability only linked to the atmospheric chemistry (i.e. not to both chemical and transport phenomena, such as for other minor species). The proxy sensibility up to few hundreds of pfu (with proton flux at energies > 10 MeV) makes clear not only extreme particle events but also those with low flux peak and fluence. The OH data are available since November 2004, from the Microwave Limb Sounder (MLS) instrument on the nearly polar orbit of EOS AURA satellite (the vertical data resolution ranges from the stratosphere up to the mesopause region). This work shows the behaviour of MLS OH data at different altitudes, locations and seasons and the identified changes induced by some SEP events.

Damiani, Alessandro; Marisa, Storini; Claudio, Rafanelli

62

Separating Terrestrial, Oceanic and Stratospheric Signals in Atmospheric N2O: Seasonal Cycles and Isotopic Signatures  

NASA Astrophysics Data System (ADS)

Seasonal cycles in atmospheric N2O provide potentially important information about surface source distributions. Previous attempts to reproduce observed N2O seasonal cycles in atmospheric transport models (ATMs) were largely unsuccessful, for reasons that may include the following: 1) The observed cycles are very small. 2) The influence of the backflux of N2O-depleted air from the stratosphere was neglected. Here, an interpretation of the observed atmospheric N2O seasonal cycle at Cape Grim, Tasmania is presented and successfully compared to the results of an ATM run with prescribed surface sources. The exercise suggests that the observed N2O seasonal cycle can be partitioned into distinct oceanic and stratospheric components, and offers a model for future exercises at northern hemisphere monitoring stations, where terrestrial sources are also likely to influence observed seasonal cycles. Like seasonal cycles, the observed isotopic signature of tropospheric N2O represents a combination of terrestrial, oceanic, and stratospheric influences, all of which have distinct isotopic characteristics. A simple box model is used to predict the effect of seasonality on the isotopic signature of tropospheric N2O and to examine how isotopic data might complement mixing ratio measurements. Some speculations on the oceanic influence on the isotopic signature of tropospheric N2O will also be presented.

Nevison, C. D.

2004-12-01

63

Modeling the atmospheric limb emission of CO 2 at 4.3 ?m in the terrestrial planets  

Microsoft Academic Search

The MIPAS instrument on board Envisat, in Earth orbit, the PFS and OMEGA instruments on Mars Express, and VIRTIS on board Venus Express are currently providing a dataset of limb measurements of the CO2 atmospheric fluorescence emission at 4.3??m from the upper atmosphere of the three planets. These measurements represent an excellent dataset to perform comparative studies between the terrestrial

M. A. López-Valverde; M. López-Puertas; B. Funke; G. Gilli; M. Garcia-Comas; P. Drossart; G. Piccioni; V. Formisano

2011-01-01

64

Modeling the atmospheric limb emission of CO2 at 4.3 mum in the terrestrial planets  

Microsoft Academic Search

The MIPAS instrument on board Envisat, in Earth orbit, the PFS and OMEGA instruments on Mars Express, and VIRTIS on board Venus Express are currently providing a dataset of limb measurements of the CO2 atmospheric fluorescence emission at 4.3-mum from the upper atmosphere of the three planets. These measurements represent an excellent dataset to perform comparative studies between the terrestrial

M. A. López-Valverde; M. López-Puertas; B. Funke; G. Gilli; M. Garcia-Comas; P. Drossart; G. Piccioni; V. Formisano

2011-01-01

65

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

National Technical Information Service (NTIS)

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....

A. R. Townsend G. P. Asner P. P. Tans J. W. C. White

2000-01-01

66

Retention of an atmosphere on early Mars  

USGS Publications Warehouse

The presence of valley networks and indications of high erosion rates in ancient terrains on Mars suggest that Mars was warm and wet during heavy bombardment. Various processes that could occur on early Mars were integrated into a self-consistent model to determine what circumstances might lead to warm temperatures during and at the end of heavy bombardment. Included were weathering and burial of CO2 as carbonates, impact erosion, sputtering, and recycling of CO2 back into the atmosphere by burial and heating. The models suggest that despite losses from the atmosphere by weathering and impact erosion, Mars could retain a 0.5 to 1 bar atmosphere at the end of heavy bombardment partly because weathering temporarily sequesters CO2 in the ground and protects it from impact erosion while the impact rate is declining and impact erosion is becoming less effective. Because of the low output of the early Sun, surface temperatures can be above freezing only for a very efficient greenhouse, such as that suggested by Forget and Pierrehumbert [1997]. With weak greenhouse models, temperatures are below freezing throughout heavy bombardment, and such a large amount of CO2 is left in the atmosphere at the end of heavy bombardment that it is difficult to eliminate subsequently to arrive at the present surface inventory. With strong greenhouse models, temperatures are well above freezing during heavy bombardment and drop to close to freezing at the end of heavy bombardment, at which time the atmosphere contains 0.5 to 1 bar of CO2. This can be largely eliminated subsequently by sputtering and low-temperature weathering. Such a model is consistent with the change in erosion rate and the declining rate of valley formation at the end of heavy bombardment. Conditions that favor warm temperatures at the end of heavy bombardment are an efficient greenhouse, low weathering rates, low impact erosion rates, and a smaller fraction of heat lost by conduction as opposed to transport of lava to the surface.

Carr, M. H.

1999-01-01

67

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies.  

PubMed

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3. PMID:23982822

Behera, Sailesh N; Sharma, Mukesh; Aneja, Viney P; Balasubramanian, Rajasekhar

2013-08-28

68

Updating the SPARC/MITgcm to model the atmospheric circulation of super Earths and terrestrial exoplanets  

NASA Astrophysics Data System (ADS)

While many of the exoplanets detected thus far have been hot Jupiters and hot Neptunes (Jovian- and Neptunian-sized planets within 0.1 AU of their host stars), ground- and space-based surveys will continue to see a growth in the detection of so-called super Earths, that is, exoplanets with masses less than 10 times that of Earth. This class of objects will include not only planets with thick fluid envelopes but also traditional terrestrial planets with solid surfaces and thinner atmospheres. To that end, we present results from studies investigating the atmospheric circulation of these latter classes of planets using the SPARC/MITgcm, a state-of-the-art model which couples the MIT General Circulation Model with a plane-parallel, two-stream, non-gray radiative transfer model. We will describe the many updates that have been included to investigate these classes of planets. We will also present select results from these studies, focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth survey, and on general terrestrial exoplanets orbiting M-dwarfs.

Kataria, Tiffany; Showman, A. P.; Haberle, R. M.; Marley, M. S.; Fortney, J. J.; Freedman, R. S.

2013-10-01

69

Nested Atmospheric Inversion for the Terrestrial Carbon Sources and Sinks in China  

NASA Astrophysics Data System (ADS)

In this study, we establish a nested atmospheric inversion system with focus on East Asia using the Bayes theory. The global surface is separated into 39 regions based on the 22 TransCom large regions, with 17 small regions in East Asia. Monthly CO2 concentrations from 238 GlobalView sites are used in this system. The core component of this system is atmospheric transport matrix, which is created by using the TM5 model. The net carbon flux over the 39 global land and ocean regions is inverted for the period from 2001 to 2007. The inverted global terrestrial carbon sinks mainly occur in North American, most Asia, and Europe. Except for east Inner Mongolia and southern China, most areas in China appear to be carbon sinks. From 2001 to 2007, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2001, which is related to the strong El Nino event in the same year. For the same reason, China also has a lowest carbon sink in 2001. In 2005, the carbon sink in China is very small as well, due to the severe springtime drought in southern and southwest China. The mean global and China terrestrial carbon sinks over the period 2001-2007 are -2.98±1.0 and -0.28±0.28 Gt C yr-1, respectively. The uncertainties in the posterior carbon flux of China are still very large, mostly due to the lack of CO2 measurement data in China. In order to reduce these uncertainties, we plan to include the CONTRAIL data of Japan in this system.

Jiang, F.; Wang, H.; Chen, J.; Ju, W.

2011-12-01

70

Lichen metabolism identified in Early Devonian terrestrial organisms  

Microsoft Academic Search

We used delta13C values to identify lichen metabolism in the globally distributed Early Devonian (409 386 Ma) macrofossil Spongiophyton minutissimum, which had been alternatively interpreted as a green plant of bryophyte grade or as a lichen, based on its morphology. Extant mosses and hornworts exhibited a range of delta13Ctissue values that was discrete from that of extant lichens. The delta13Ctissue

A. Hope Jahren; Steven Porter; Jeffrey J. Kuglitsch

2003-01-01

71

Terrestrial Gamma-ray Flashes Observed on BATSE/CGRO and ELF/VLF Radio Atmospherics  

NASA Astrophysics Data System (ADS)

During its nine year lifetime in orbit, the Burst and Transient Source Experiment (BATSE) detector, aboard the Compton Gamma Ray Observatory (CGRO) spacecraft observed a total of 74 Terrestrial Gamma-ray Flashes (TGFs). Of these, simultaneous broadband ELF/VLF data from Palmer Station, Antarctica, were found to be available for six new TGF cases in addition to two previously reported cases [Inan et al., 1996]. Analysis of temporal and directional association between radio atmospherics and TGFs reveal solid evidence of an associated radio atmospheric in three of the six events, while a fourth case exhibits evidence of magnetically conjugate source lightning. In all three cases, and with the propagation time of both gamma-rays and radio atmospherics fully accounted for, the associated sferics are found to occur 1-3 ms prior to the production of TGFs. In one of three cases with associated radio atmospherics, three consecutive gamma-ray peaks in the BATSE data are apparently linked to three consecutive radio atmospherics. In two of the six BATSE TGF cases with Palmer data, no evidence is found for any associated radio atmospherics occurring within 10-ms of the TGF event, although the presence of an active storm center in the region underneath BATSE/CGRO is confirmed by sferic activity during the 30-min period surrounding the event. For the remaining one of the six cases, no associated sferics is found to be arriving from a direction consistent with the location of the CGRO. However, an associated sferic is observed to be arriving from approximately the geomagnetically conjugate region, suggesting that this particular TGF might have been produced by a lightning flash in the conjugate region. Overall, the analysis of all six BATSE cases with Palmer data points to the possibility of different physical mechanisms generating TGFs under different conditions.

Cohen, M. B.; Inan, U. S.; Fishman, G.

2005-12-01

72

Trophic network models explain instability of Early Triassic terrestrial communities  

PubMed Central

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

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

2007-01-01

73

Trophic network models explain instability of Early Triassic terrestrial communities.  

PubMed

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

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

2007-09-01

74

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

NASA Astrophysics Data System (ADS)

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. ?13C plant values fluctuate around - 23‰ to - 22‰ for the Valanginian-Hauterivian, except during the Upper Valanginian where ?13C plant values record a positive excursion to ˜- 18‰. Based upon ammonite biostratigraphy from Crimea, and in conjunction with a composite Tethyan marine ?13C carb curve, several conclusions can be drawn: (1) the ?13C 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 ?13C 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.

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

2005-12-01

75

Climate and atmospheric drivers of historical terrestrial carbon uptake in the province of British Columbia, Canada  

NASA Astrophysics Data System (ADS)

The impacts of climate change and increasing atmospheric CO2 concentration on the terrestrial uptake of carbon dioxide since 1900 in the Canadian province of British Columbia are estimated using the process-based Canadian Terrestrial Ecosystem Model (CTEM). Model simulations show that these two factors yield a carbon uptake of around 44 g C m-2 yr-1, during the 1980s and 1990s, and continuing into 2000s, compared to pre-industrial conditions. The increased carbon uptake translates into an increased sink of 41 Tg C yr-1, when multiplied with the 944 700 km2 area of the province. About three-quarters of the simulated sink enhancement in our study is attributed to changing climate, and the rest is attributed to increase in CO2 concentration. The model response to changing climate and increasing CO2 is corroborated by comparing simulated stem wood growth rates with ground-based measurements from inventory plots in coastal British Columbia. The simulated sink is not an estimate of the net carbon balance because the effect of harvesting and insect disturbances is not considered.

Peng, Y.; Arora, V. K.; Kurz, W. A.; Hember, R. A.; Hawkins, B.; Fyfe, J. C.; Werner, A. T.

2013-08-01

76

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

USGS Publications Warehouse

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.

Griffin, D. W.

2004-01-01

77

Possible use of terrestrial mosses in detection of atmospheric deposition of 7Be over large areas.  

PubMed

The activities of naturally occurring radionuclides (7)Be, (214)Bi and (210)Pb were measured in samples of terrestrial mosses collected in Serbia (42 degrees 26'19''N-45 degrees 23'12''N). The objective of this work was to establish if detectable amounts of (7)Be and (210)Pb can be found in mosses and investigate their possible variabilities over some area. These are the first steps in introducing mosses as a medium in possible monitoring of spatial distribution of (7)Be atmospheric deposition. The mean value of 360 Bq/kg of (7)Be activity was found in collected moss samples and some nonuniformity in spatial distribution (a 2.8-fold range in measured values) was observed. PMID:17382436

Krmar, M; Radnovi?, D; Rakic, S; Matavuly, M

2007-03-26

78

Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses  

Microsoft Academic Search

Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow\\/ice-albedo feedback (where area changes in snow and\\/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow\\/ice); and

Trudy M. H. Wohlleben

2009-01-01

79

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

Microsoft Academic Search

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.

1993-01-01

80

Influences of Forest Tree Species and Early Spring Temperature on Surface-Atmosphere Transfers of Water and Carbon in the Northeastern U.S  

Microsoft Academic Search

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

J. L. Hadley; P. Kuzeja; T. Mulcahy; S. Singh

2008-01-01

81

The hydroxyl radical as an indicator of SEP fluxes in the high-latitude terrestrial atmosphere  

NASA Astrophysics Data System (ADS)

The low background values at nighttime of the mesospheric hydroxyl (OH) radical make it easier to single out the atmospheric response to the external solar forcing in Polar Regions. Because of the short lifetime of HOx, it is possible to follow the trails of Solar Energetic Particle (SEP) events in the terrestrial atmosphere, as shown by Storini and Damiani (2008). The sensitivity of this indicator makes discernible not only extreme particle events with a flux peak of several thousand pfu [1 pfu = 1 particle/(cm2 s sr)] at energies >10 MeV, but also those with lower flux up to about 300 pfu. Using data from the Microwave Limb Sounder (MLS) on board the EOS AURA satellite, we examined the correlation of OH abundance vs. solar proton flux for almost all the identified SEP events spanning from November 2004 to December 2006 (later on no more SEP events occurred during Solar Cycle no. 23). The channels at energies greater than 5 MeV and 10 MeV showed the best correlation values (r ˜ 0.90-0.95) at altitudes around 65-75 km whereas, as expected, the most energetic channels were most highly correlated at lower altitudes. Therefore, it is reasonably possible to estimate the solar proton flux from values of mesospheric OH (and viceversa) and it could be useful in studying periods with gaps in the records of solar particles. In addition, the SEP events of September 2005, characterized by an evident hemispheric asymmetry of the SEP-induced OH formation, have been examined separately. The impact of the SEPs on the hydroxyl radical was appreciably stronger in the Northern Hemisphere than in the Southern at altitudes above roughly 60 km and also the nighttime OH layer was involved. Preliminary analyses performed with other MLS data (i.e., O3, H2O, T) suggest that atmospheric in situ conditions could play a relevant role in explaining the hemispheric asymmetry of OH.

Damiani, A.; Storini, M.; Rafanelli, C.; Diego, P.

2010-11-01

82

The Terrestrial Fossil Organic Matter Record of Global Carbon Cycling: A Late Paleozoic through Early Mesozoic Perspective  

Microsoft Academic Search

The carbon isotope composition of terrestrial fossil organic matter (delta13Corg) has been widely used as a proxy of global carbon cycling and to reconstruct perturbations to the ocean-atmosphere carbon budget. The degree to which terrestrial delta13Corg records local to regional environmental conditions versus the evolution of the global carbon cycle has been highly debated. The high-resolution (104 to 106 m.y.)

I. P. Montanez

2006-01-01

83

Sulfur Volatiles in the Early Martian Atmosphere  

NASA Astrophysics Data System (ADS)

Our modeling indicates a high sulfur solubility in martian mantle melts and suggests that sulfur volatile pulses associated with large, discreet volcanic events during the late Noachian may have significantly warmed the atmosphere.

Johnson, S. S.; Zuber, M. T.; Grove, T. L.; Pavlov, A. A.; Mischna, M. A.

2007-03-01

84

The photochemistry of the early atmosphere  

NASA Astrophysics Data System (ADS)

The composition of the earth's present atmosphere is described. The formation of the earth from the coalescence and accretion of the refractory elements of the solar nebula is examined. Two possible compositions of the prebiological paleoatmosphere, which are a reducing atmosphere of CH4, NH3, and H2 or a mildly reducing atmosphere of H2O, CO2, and N2, and their photochemistry are analyzed. General photochemical and chemical processes are reviewed. The use of the coupled continuity-transport equation to calculate the vertical distribution of each species is discussed. A study of the photochemical process of CH4 and NH3 reveals that the reducing atmosphere could not possibly exist. An analysis of the photochemistry and chemistry of the H2O, CO2, and N2 atmosphere reveals that the photodissociation of H2O and CO2 results in a prebiotic source of O2, H2CO, and HCN, which are the components for the evolution of photosynthetic organisms and a strongly oxidizing atmosphere. The reactions which produce O2 and H2CO from H2O and CO2, and the relation between H2O and CO2 concentrations and O2 levels are investigated. The formation of O3 photochemically from O2 is explained.

Levine, J. S.

85

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

PubMed

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

Krupa, S V

2003-01-01

86

Increasing retention of early career female atmospheric scientists  

Microsoft Academic Search

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

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

2010-01-01

87

Impact of atmospheric aerosol light scattering and absorption on terrestrial net primary productivity  

NASA Astrophysics Data System (ADS)

Scattering and absorption of sunlight by anthropogenic aerosols reduce the photosynthetically active radiation (PAR) incident upon the Earth's surface, but increase the fraction of the PAR that is diffuse. These alterations to irradiance may elicit conflicting responses in terrestrial plants: photosynthesis and net primary productivity (NPP) are slowed by reductions in total PAR, but enhanced by increases in diffuse PAR. In this paper, we use two canopy photosynthesis models to estimate the net effect of aerosols on carbon assimilation by green plants during summertime at midlatitudes. The model calculations indicate that the net effect of PAR scattering and absorption by atmospheric aerosols on NPP can be positive, neutral, or negative. Two parameters that strongly influence the net effect are the aerosol optical depth (integral of light extinction with height) and the cloud cover. On cloudless days NPP peaks under moderately thick aerosol loadings. On overcast days, aerosols slow NPP. The implications of these results for various regions of the globe and possible directions for future studies on the effect of aerosols on plant growth are discussed.

Cohan, Daniel S.; Xu, Jin; Greenwald, Roby; Bergin, Michael H.; Chameides, William L.

2002-12-01

88

A terrestrial vegetation turnover in the middle of the Early Triassic  

NASA Astrophysics Data System (ADS)

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 ?13C 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.

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

2013-06-01

89

Identification of Lichen Metabolism in an Early Devonian Terrestrial Fossil using Carbon Stable Isotope Signature  

NASA Astrophysics Data System (ADS)

The fossil organismSpongiophyton minutissimum is commonly found in early terrestrial assemblages (Devonian age, 430-340 Ma). Suites of morphological descriptions of this fossil have been published, starting in 1954, and have led to two competing hypotheses: 1.) that this early colonizer of land was a primitive bryophyte, and therefore a precursor to modern plant organisms, and 2.) thatS. minutissimum was a lichen: a close association between an alga and a fungus. Because the ultimate mechanisms for carbon supply to the carboxylating enzyme in bryophytes and lichens differ fundamentally, we expect these two types of organisms to exhibit separate ranges of ? 13Ctissue value. In bryophytes, gaseous carbon dioxide diffuses through perforations in cuticle (resulting in ? 13Catmosphere - ? 13Cbryophyte = ~20 ‰ ). Within the lichen, carbon is supplied to the carboxylating enzyme of the photobiont as carbon dioxide dissolved in fungal cell fluids (resulting in ? 13Catmosphere - ? 13Clichen = ~15 ‰ ). By comparing the ? 13Ctissue value ofS. minutissimum (mean = -23 ‰ ;n = 75) with ? 13Ctissue values in twenty-five lichens, representative of the four different phylogenetic clades (mean = -23 ‰ ;n = 25) and thirty different genera of bryophytes including mosses, liverworts, and hornworts (mean = -28 ‰ ;n = 30), we conclude thatS. minutissimum was cycling carbon via processes that much more closely resembled those of lichens, and not bryophytes. We discuss the general strategies associated with lichen biology, such as the ability to withstand dessication during reproduction, and how they may have contributed to the successful colonization of terrestrial environments.

Porter, S.; Jahren, H.

2002-05-01

90

The Role of Nitrogen Dynamics in the Responses of Terrestrial Carbon Dynamics to Changes in Atmospheric Carbon Dioxide, Climate, and Land Use  

Microsoft Academic Search

While it has long been appreciated that alterations of the nitrogen cycle can substantially affect the carbon dynamics of terrestrial ecosystems, most large-scale models of terrestrial carbon dynamics have ignored carbon-nitrogen interactions in making projections of how carbon dynamics will respond to changes in atmospheric carbon dioxide, climate, and land use. Numerous experimental studies have documented that the uptake of

A. D. McGuire; J. Melillo; D. Kicklighter; L. Joyce

2007-01-01

91

Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses  

NASA Astrophysics Data System (ADS)

Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/ice-albedo feedback (where area changes in snow and/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/ice); and (2) The elevation - mass balance feedback (where thickness changes in terrestrial ice masses cause changes to atmospheric circulation and precipitation patterns, leading to further ice thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial ice masses; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for ice flow, mass flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/ice-albedo feedback can locally exceed that of sea ice on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and ice cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon Ice Cap, observed mass gains in the northwest sector of the ice cap would be smaller without orographic precipitation and the mass balance---elevation feedback, supporting the hypothesis that this feedback is playing a role in the evolution of the ice cap.

Wohlleben, Trudy M. H.

92

Retention of an atmosphere on early Mars  

Microsoft Academic Search

The presence of valley networks and indications of high erosion rates in ancient terrains on Mars suggest that Mars was warm and wet during heavy bombardment. Various processes that could occur on early Mars were integrated into a self-consistent model to determine what circumstances might lead to warm temperatures during and at the end of heavy bombardment. Included were weathering

Michael H. Carr

1999-01-01

93

Thermal escape of carbon from the early Martian atmosphere  

NASA Astrophysics Data System (ADS)

Observations suggest that Mars was wet and warm during the late Noachian, which probably requires a dense CO2 atmosphere. But would a dense CO2 early Martian atmosphere have been stable under the strong EUV flux from the young Sun? Here we show that thermal escape of carbon was so efficient during the early Noachian, 4.1 billion years ago (Ga), that a CO2-dominated Martian atmosphere could not have been maintained, and Mars should have begun its life cold. By the mid to late Noachian, however, the solar EUV flux would have become weak enough to allow a dense CO2 atmosphere to accumulate. Hence, a sustainable warm and wet period only appeared several hundred million years (Myrs) after Mars formed.

Tian, Feng; Kasting, James F.; Solomon, Stanley C.

2009-01-01

94

Short-lived radionuclides as monitors of early crust-mantle differentiation on the terrestrial planets  

NASA Astrophysics Data System (ADS)

The kinetic energy from large impacts, the gravitational energy released by core formation, and the heat provided by the decay of short-lived radioactive isotopes all drive extensive melting and chemical differentiation of silicate planets/planetesimals during and shortly after their formation. This early differentiation is best preserved on small objects such as the parent bodies of the eucrite and angrite meteorites where silicate melts were produced within 3 million years of solar system formation. The W isotopic composition of some iron meteorites testifies to core segregation on small planetesimals within as little as one million years or less of solar system formation. On larger objects, such as the Moon, Mars and Earth, the evidence for early differentiation provided by long-lived radioisotope systems has been variably overprinted by the continuing differentiation of these objects, but a clear signature of extensive early planet-scale differentiation is preserved in a variety of short-lived radioisotope systems, particularly, I-Pu-Xe, Hf-W and 146Sm- 142Nd. All these systems suggest that global differentiation of planetesimals and the terrestrial planets occurred during the first hundred million years of solar system history. This early processing of the Moon, Mars and Earth, may have fundamentally affected the evolution of these planets and their current internal compositional structure.

Carlson, Richard W.; Boyet, Maud

2009-03-01

95

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

PubMed Central

The evolution of Earth’s 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. 550–560 million year ago (Ma), reinforcing previous geochemical indications that Earth surface oxygenation facilitated this radiation. The second, perhaps larger, oxygenation took place around 400 Ma, 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.

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

96

Simultaneous Assimilation of FAPAR and Atmospheric CO2 into a Terrestrial Vegetation Model  

NASA Astrophysics Data System (ADS)

Tackling the possible severe impacts of climate change on the carbon cycle and land water resources requires further development of simulation models and monitoring capabilities. Carbon cycle impacts can lead to further climate change through releases of CO2, and impacts on water resources are critical for human survival. A rapidly increasing monitoring capability is Earth Observation (EO) by satellites. Usually, EO by its very nature focuses on diagnosing the current state of the planet. However, it is possible to use EO products in data assimilation systems to improve not only the diagnostics of the current state, but also the accuracy of future predictions. This study investigates the simultaneous assimilation of ground-based atmospheric CO2 concentration data and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) derived from measurements made by the MERIS sensor on-board ENVISAT and to what extent these data can be used to improve models of terrestrial ecosystems, carbon cycling and hydrology. Further development of the Carbon Cycle Data Assimilation System (CCDAS, see http://CCDAS.org) for the purpose of simultaneous assimilation of FAPAR and atmospheric carbon dioxide measurements showed that the design of the ecosystem model is critical for successful implementation of highly efficient variational data assimilation schemes. This is important, because each newly added data stream will typically require a separate observational operator. In the case of this study, it was the leaf development (phenology) sub-model that needed to be developed. As a variational data assimilation scheme, CCDAS relies on first and second derivatives of the underlying model for estimating process parameters with uncertainty ranges. In a subsequent step these parameter uncertainties are mapped forward onto uncertainty ranges for predicted carbon and water fluxes. We present assimilation experiments of MERIS FAPAR at the global scale together with in situ observations of atmospheric CO2 in a coarse-resolution setup of CCDAS. We also present a set of mission benefit analyses, which explore design options for future space mission through quantitative network design (QND) techniques. The benefit is quantified by the reduction in uncertainty on simulated carbon and water fluxes. We analyse the effects of FAPAR and carbon dioxide observations individually as well as the effects of mission length and sensor resolution. The reduction of uncertainties from assimilating FAPAR is modest for carbon fluxes, but considerable for hydrological quantities, in particular evapotranspiration. Sensor resolution is less critical for successful data assimilation, and with even relatively short time series of only a few years, significant uncertainty reduction can be achieved. Regionally, the highest constraint for both carbon fluxes and hydrological quantities is found for Australia and Africa (in that order). This can be explained by the fact that most of the vegetation on these continents grows in tropical or sub-tropical semi-arid environments, where observation conditions are especially favourable, as already noted. Here, vegetation is water limited, which underlines the usefulness of FAPAR assimilation for hydrological studies. The study demonstrates how QND techniques can be applied to assess the complementarity of multiple data streams and the value of multi-data synergies.

Kaminski, T.; Knorr, W.; Scholze, M.; Gobron, N.; Pinty, B.; Giering, R.; Mathieu, P. P.

2012-04-01

97

Evolution of the Atmospheres of Terrestrial Planets : Focus on Mars and Venus  

Microsoft Academic Search

A simple atmosphere-interior coupling has been implemented for Venus under stagnant lid convection regime; the atmosphere gains water from the degassing, through a parameterized model of mantle convection, including volatile exchanges between the mantle and the atmosphere (additionally, the mean depth of partial melting is taken into account), and a radiative-convective atmosphere model computes the temperature at the planet's surface.

C. Gillmann; P. Lognonné; E. Chassefière

2006-01-01

98

New detections of O III lines in the UV and visible ranges in the terrestrial upper atmosphere  

NASA Astrophysics Data System (ADS)

Doubly-charged ions are peculiar atmospheric species interesting to study due to their exotic or unexpected photo-chemistry and their high reactivity. We focus here on the O++ doubly-charged ion, which was detected in the terrestrial atmosphere in 1967 by mass spectrometry. Its photochemistry has been characterized in a number of studies. Excited state fluorescence of this ion is well known, since its doublet centered around 500 nm has been used as a tracer of electron densities and temperatures in gaseous nebulae since the 1940's. O III emissions have been observed in the terrestrial atmosphere in the extreme ultraviolet region. We report here the new and unambiguous detection of two emission lines of O III at 495.8911 and 500.6843 nm, with the Ultraviolet and Visible Echelle Spectrograph (UVES) mounted on UT2 of the Very Large Telescope (VLT) in Chile. The measurements were performed after sunset, October 30, 2003 during the so-called "Halloween" storm. The intensities of these emissions are ~70 mRayleigh, and ~260 mRayleigh, respectively. We discuss the possible methods of production of the ion. We also discuss the potential identification of O III emission near 166 nm in a spectrum acquired with the Hopkins Ultraviolet Telescope (HUT) telescope on the dayside, in December 1990. These emissions constitute a new diagnostic of the state of the ionosphere, with potentially interesting applications to Venus and Mars.

Witasse, O. G.; Slanger, T. G.; Thissen, R.

2011-12-01

99

Carbon Dioxide/Methane Greenhouse Atmosphere on Early Mars.  

National Technical Information Service (NTIS)

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 sho...

L. L. Brown J. F. Kasting

1993-01-01

100

A possible global covariance between terrestrial gross primary production and 13C discrimination: Consequences for the atmospheric 13C budget and its response to ENSO  

Microsoft Academic Search

It is well known that terrestrial photosynthesis and 13C discrimination vary in response to a number of environmental and biological factors such as atmospheric humidity and genotypic differences in stomatal regulation. Small changes in the global balance between diffusive conductances to CO2 and photosynthesis in C3 vegetation have the potential to influence the 13C budget of the atmosphere because these

J. T. Randerson; G. J. Collatz; J. E. Fessenden; A. D. Munoz; C. J. Still; J. A. Berry; I. Y. Fung; N. Suits; A. S. Denning

2002-01-01

101

Satellite observations of terrestrial water storage provide early warning information about drought and fire season severity in the Amazon  

NASA Astrophysics Data System (ADS)

risk in the Amazon can be predicted several months before the onset of the dry season using sea surface temperatures in the tropical north Atlantic and tropical Pacific. The lead times between ocean state and the period of maximum burning (4-11 months) may enable the development of forecasts with benefits for forest conservation, yet the underlying physical and biological mechanisms responsible for these temporal offsets are not well known. Here, we examined the hypothesis that year-to-year variations in soil water recharge during the wet season modify atmospheric water vapor and fire behavior during the following dry season. We tested this hypothesis by analyzing terrestrial water storage observations from the Gravity Recovery and Climate Experiment (GRACE), active fires from the Moderate Resolution Imaging Spectroradiometer (MODIS), and several other satellite and atmospheric reanalysis datasets during 2002-2011. We found that terrestrial water storage deficits preceded severe fire seasons across the southern Amazon. The most significant relationships between monthly terrestrial water storage and the sum of active fires during the dry season occurred during April-August (p < 0.02), corresponding to 1-5 month lead times before the peak month of burning (September). Analysis of other datasets provided evidence for a cascade of processes during drought events, with lower cumulative precipitation (and higher cumulative evapotranspiration) in the wet season substantially reducing terrestrial water storage, and subsequently, surface and column atmospheric water vapor. Our results suggest that terrestrial water storage observations from GRACE have the potential to improve fire season forecasts for the southern Amazon.

Chen, Yang; Velicogna, Isabella; Famiglietti, James S.; Randerson, James T.

2013-06-01

102

Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Ceh? Quarry, South Carpathians, Romania  

NASA Astrophysics Data System (ADS)

K?dzior, A. and Popa, E.M. 2013. Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Ceh? Quarry, South Carpathians, Romania. Acta Geologica Polonica, 63 (2), 175-199. Warszawa. The continental, coal bearing Steierdorf Formation, Hettangian - Sinemurian in age, is included in the Mesozoic cover of the Re?i?a Basin, Getic Nappe, South Carpathians, Romania. The Steierdorf Formation can be studied in Anina, a coal mining center and an exceptional locality for Early Jurassic flora and fauna, occurring in the middle of the Re?i?a Basin. This paper presents the results of sedimentological, stratigraphical and paleobotanical researches undertaken in Colonia Ceh? open cast mine in Anina, where the Steierdorf Formation outcrops widely. Several sedimentary facies associations have been described, these associations permitting the reconstruction of various depositional systems such as alluvial fans, braided and meandering river systems, as well as lacustrine and coal generating marsh systems of the Steierdorf Formation. The sedimentary associations recorded within the Steierdorf Formation show a gradual fining upward trend, pointing to a rising marine water table and a decreasing relief within the source area.

K?dzior, Artur; Popa, Mihai E.

2013-06-01

103

A carbon dioxide/methane greenhouse atmosphere on early Mars  

NASA Astrophysics Data System (ADS)

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 -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 10-4 requires a flux of NH3 on the order of 1012 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.

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

104

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

105

Hydrogen-Nitrogen Greenhouse Warming in Earth's Early Atmosphere  

NASA Astrophysics Data System (ADS)

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 H2-N2 collision-induced absorption. With two to three times the present-day atmospheric mass of N2 and a H2 mixing ratio of 0.1, H2-N2 warming would be sufficient to raise global mean surface temperatures above 0°C under 75% of present-day solar flux, with CO2 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 H2 and CO2 to CH4, with potentially observable consequences in the geological record.

Wordsworth, Robin; Pierrehumbert, Raymond

2013-01-01

106

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

PubMed

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

Wordsworth, Robin; Pierrehumbert, Raymond

2013-01-01

107

Atmospheric composition and climate on the early Earth  

PubMed Central

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.

Kasting, James F; Howard, M. Tazewell

2006-01-01

108

Hot atom populations in the terrestrial atmosphere. A comparison of the nonlinear and linearized Boltzmann equations  

NASA Astrophysics Data System (ADS)

We use a finite difference discretization method to solve the space homogeneous, isotropic nonlinear Boltzmann equation. We study the time evolution of the distribution function in relation to the solution of the linearized Boltzmann equation for three different initial conditions. The relaxation process is described in terms of the Laguerre moments and the spectral properties of the linearized collision operator. The motivation is the need to include self-collisions in the study of suprathermal oxygen atoms in the terrestrial exosphere.

Sospedra-Alfonso, Reinel; Shizgal, Bernie D.

2012-11-01

109

Possible use of terrestrial mosses in detection of atmospheric deposition of 7Be over large areas  

Microsoft Academic Search

The activities of naturally occurring radionuclides 7Be, 214Bi and 210Pb were measured in samples of terrestrial mosses collected in Serbia (42°26?19?N–45°23?12?N). The objective of this work was to establish if detectable amounts of 7Be and 210Pb can be found in mosses and investigate their possible variabilities over some area. These are the first steps in introducing mosses as a medium

M. Krmar; D. Radnovi?; S. Rakic; M. Matavuly

2007-01-01

110

Correlation of Early Tertiary Terrestrial Deposits of the Amaga Basin, Cauca Depression, Colombian Andes  

NASA Astrophysics Data System (ADS)

The Amaga Formation of the Amaga Basin preserves early Tertiary terrestrial deposits of many facies: channel, crevasse splay, paludal, flood plain, point bar, etc. These deposits lie between two major strike-slip fault zones, the Cauca and the Romeral in the Cauca Valley of the northern Andes of Colombia. Coal deposits characterize the lower part of the stratigraphic section; fine to medium clastic sediments otherwise dominate the sections. Within the basin, correlation between sections is difficult because various discontinuities interrupt the continuity of the strata. These include Tertiary intrusives, folding and faulting. Rapid lateral facies changes further complicate the correlations. Detailed studies on five stratigraphic sections are underway. Multiple methods of correlating sections are being used, including fluvial sequence stratigraphy in outcrops, architectural facies analysis, heavy mineral separates, grain-size and grain-ratio variations, paleocurrent directions, and magnetic property variations. Distinctive regional variations in magnetic anisotropic susceptibility indicate areas in which tectonic effects overprint sedimentary fabrics. The presence of secondary hematite and siderite is related to that overprinting. A major compositional break (identified by grain-ratio variations) has been found in the middle of the section. The integrated correlation results are summarized.

Sierra, G. M.; Sierra, G. M.; MacDonald, W. D.

2001-05-01

111

Modeling the atmospheric limb emission of CO 2 at 4.3 ?m in the terrestrial planets  

NASA Astrophysics Data System (ADS)

The MIPAS instrument on board Envisat, in Earth orbit, the PFS and OMEGA instruments on Mars Express, and VIRTIS on board Venus Express are currently providing a dataset of limb measurements of the CO 2 atmospheric fluorescence emission at 4.3-?m from the upper atmosphere of the three planets. These measurements represent an excellent dataset to perform comparative studies between the terrestrial planets' upper atmospheres, and also to test our theoretical understanding of these emissions. In order to exploit these datasets, we apply a set of non-local thermodynamic equilibrium (non-LTE) models developed at the IAA/CSIC, in Granada, Spain, to a selection of data. In general, the models can explain the main spectral features of the measurements, and also the altitude and solar zenith angle variations. However, the simulations for Mars and Venus give an incorrect ratio of the emissions at two wavelengths, 4.4 and 4.32?m. In order to explain this deficiency, a revision of the most uncertain non-LTE energy transfer parameters has been performed. The quenching rate of ?3 quanta of high-energy CO 2 states by CO 2 itself could reduce the model-data discrepancy if increased by a factor 2-4, still within its current uncertainty range. This factor, however, is subject to the uncertainty in the thermal structure. A number of simulations with the non-LTE models were also used to study and compare the role of radiative transfer in this spectral region in the three terrestrial planets. Sensitivity studies of density and temperature are also presented, and they permit an analysis of how the differences between the planets and between the three instruments affect their sounding capabilities.

López-Valverde, M. A.; López-Puertas, M.; Funke, B.; Gilli, G.; Garcia-Comas, M.; Drossart, P.; Piccioni, G.; Formisano, V.

2011-08-01

112

Fractionation of Terrestrial Neon by Hydrodynamic Hydrogen Escape from Ancient Steam Atmospheres (Abstract Only).  

National Technical Information Service (NTIS)

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 to...

K. Zahnle

1991-01-01

113

Solar wind induced atmospheric erosion from a EUV heated and expanded early Earth atmosphere  

NASA Astrophysics Data System (ADS)

Abstract Higher EUV fluxes of the young Sun led to a warmer and expanded thermosphere at early Earth than today. Under conditions, depending on the thermospheric composition and the amount of IR-coolers, hydrostatic equilibrium was not always maintained and hydrodynamic flow and expansion of the upper atmosphere resulting in adiabatic cooling of the exobase temperature could develop. Depending on the atmospheric protection by the Earth's magnetosphere, the current atmospheric composition was determined by atmospheric escape processes, volcanic outgassing and the appearance of life. Recent model results indicate that depending on the higher solar EUV flux of the young Sun, the exosphere could expand beyond the magnetopause. The constituents above the magnetopause could be ionized and picked up by the solar wind plasma flow. By applying a numerical test particle model and expected magnetosphere configurations, we study the non-thermal loss rates of nitrogen, oxygen and hydrogen ions which are eroded from extended exospheres by the solar wind of the young Sun during the period where life appeared on Earth. Thermal and non-thermal loss rates are compared and the relevance of the results related to early Earth atmosphere studies will be discussed. [1] Lammer, H., Kasting, J. F., Chassefíere, E., Johnson, R. E., Kulikov, Yu. N., Tian, F., (2008) Space Sci. Rev., submitted.

Lichtenegger, Herbert I. M.; Lammer, Helmut; Grießmeier, Jean-Mathias; Tian, Feng; Kulikov, Yuri N.; Kasting, James F.

2008-09-01

114

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

NASA Astrophysics Data System (ADS)

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.

King, A. W.

2008-12-01

115

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

116

The seasonal exchange of carbon dioxide between the atmosphere and the terrestrial biosphere: Extrapolation from site-specific models to regional models  

SciTech Connect

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. 142 refs., 59 figs., 47 tabs

King, A.W.; DeAngelis, D.L.; Post, W.M.

1987-12-01

117

Net primary production of terrestrial ecosystems in China and its equilibrium responses to changes in climate and atmospheric CO2 concentration  

Microsoft Academic Search

We used the Terrestrial Ecosystem Model (TEM, version 4.0) to estimate net primary production (NPP) in China for contemporary climate and NPP responses to elevated CO 2 and climate changes projected by three atmospheric general circulation models (GCMs): Goddard Institute for Space Studies (GISS), Geophysical Fluid Dynamic Laboratory (GFDL) and Oregon State University (OSU). For contemporary climate at 312.5 ppmv

X. Xiao; J. M. Melillo; D. W. Kicklighter; Y. Pan; A. D. McGuire; J. Helfrich

118

Modeling the Solar Terrestrial Environment from the Corona to the Atmosphere  

NASA Astrophysics Data System (ADS)

Traditionally, numerical modeling has focused on distinct regions of the Solar Terrestrial Environment such as the corona, magnetosphere, or ionosphere/thermosphere (ITM). More recently several efforts have begun to model this closely coupled system through linking the regional codes together. We discuss here from the perspective of our project the characteristics of the individual codes, which are well known and respected in the SPA community: the SAIC corona code, the NCAR solar wind code, the LFM magnetosphere code, the Rice RCM, and NCAR ITM code (TING). We further discuss the issues important for coupling of these codes, and explore briefly the methods from the computational and computer sciences that may help address them.

Goodrich, C.; Drake, J.; Sussman, A.; Linker, J.; Lyon, J.; Odstrcil, D.; Toffoletto, F.; Wang, W.

2002-05-01

119

Feeling the cold: atmospheric CO 2 enrichment and the frost sensitivity of terrestrial plant foliage  

Microsoft Academic Search

Quantitative palaeoclimate reconstructions from plant fossils using the nearest living relative (NLR) approach axiomatically assume that the climatic limits of plant distributions have largely remained unchanged over at least the past 250 Myr. However, throughout much of the Mesozoic the atmospheric CO2 concentration is predicted to have been several times greater than the present day, and long-term (?5 yr) experimental

D. J Beerling; A. C Terry; C Hopwood; C. P Osborne

2002-01-01

120

Muon diagnostics of the Earth's atmosphere, near-terrestrial space and heliosphere: first results and perspectives  

Microsoft Academic Search

Muon diagnostics is a new technique of remote monitoring and forecasting of the development of various dynamic processes in the heliosphere and in the atmosphere and magnetosphere of the Earth based on the analysis of spatial- angular and temporal variations of muon flux simultaneously detected from all directions of upper hemisphere. For practical realization of the technique multi- directional muon

D. A. Timashkov; N. S. Barbashina; V. V. Borog

2008-01-01

121

Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere  

PubMed Central

Lovelock and Whitfield suggested in 1982 that, as the luminosity of the Sun increases over its life cycle, biologically enhanced silicate weathering is able to reduce the concentration of atmospheric carbon dioxide (CO2) so that the Earth's surface temperature is maintained within an inhabitable range. As this process continues, however, between 100 and 900 million years (Ma) from now the CO2 concentration will reach levels too low for C3 and C4 photosynthesis, signaling the end of the solar-powered biosphere. Here, we show that atmospheric pressure is another factor that adjusts the global temperature by broadening infrared absorption lines of greenhouse gases. A simple model including the reduction of atmospheric pressure suggests that the life span of the biosphere can be extended at least 2.3 Ga into the future, more than doubling previous estimates. This has important implications for seeking extraterrestrial life in the Universe. Space observations in the infrared region could test the hypothesis that atmospheric pressure regulates the surface temperature on extrasolar planets.

Li, King-Fai; Pahlevan, Kaveh; Kirschvink, Joseph L.; Yung, Yuk L.

2009-01-01

122

Increasing retention of early career female atmospheric scientists  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

123

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

SciTech Connect

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.

Davis, P.A.; Kim, S.B.; Chouhan, S.L.; Workman, W.J.G. [Atomic Energy of Canada Limited (Canada)

2005-07-15

124

Oxygen Isotopic Anomaly in Terrestrial Atmospheric Carbonates and its Implications to Understand the Role of Water on Mars  

NASA Astrophysics Data System (ADS)

Mineral aerosols produced from wind-blown soils are an important component of the earth system and comprise about 1000-3000 Tg.yr-1 compared to 400 Tg.yr-1 of secondary aerosols (e.g. carbonaceous substances, organics, sulfate and nitrates). Aerosols have important consequences for health, visibility and the hydrological cycle as they provide reactive surfaces for heterogeneous chemical transformation that may influence gas phase chemistry in the atmosphere. Tropospheric ozone produced in a cascade of chemical reactions involving NOx and VOC’s, can interact with aerosol surfaces to produce new compounds. Oxygen triple isotopic compositions of atmospheric carbonates have been used for the first time to track heterogeneous chemistry at the aerosol surfaces and to resolve a chemical mechanism that only occurs on particle surfaces. Fine and coarse aerosol samples were collected on filter papers in La Jolla, CA for one week. Aerosol samples were digested with phosphoric acid and released CO2 was purified chromatographically and analyzed for O isotopes after fluorination. Data indicated oxygen isotopic anomaly (?17O = ?17O - 0.524 ?18O) ranging from 0.9 to 3.9 per mill. Laboratory experiments revealed that adsorbed water on particle surfaces facilitates the interaction of the gaseous CO2 and O3 with formation of anomalous hydrogen peroxide and carbonates. This newly identified chemical reaction scenario provides a new explanation for production of the isotopically anomalous carbonates found in the SNC Martian meteorites and terrestrial atmospheric carbonates and it also amplifies understanding of water related processes on the surface of Mars. The formation of peroxide via this heterogeneous reaction on aerosols surface suggests a new oxidative process of utility in understanding ozone and oxygen chemistry both at Mars and Earth.

Thiemens, M. H.; Shaheen, R.

2010-12-01

125

A preliminary study of the application of some predictive modeling techniques to assess atmospheric mercury emissions from terrestrial surfaces.  

PubMed

Predictive modeling techniques are applied to investigate their potential usefulness in providing first order estimates on atmospheric emission flux of gaseous soil mercury and in identifying those parameters most critical in controlling such emissions. Predicted data by simulation and statistical techniques are compared to previously published observational data. Results showed that simulation techniques using air/soil coupling may provide a plausible description of mercury flux trends with a RMSE of 24.4ngm(-2)h(-1) and a mean absolute error of 10.2ngm(-2)h(-1) or 11.9%. From the statistical models, two linear models showed the lowest predictive abilities (R2=0.76 and 0.84, respectively) while the Generalized Additive model showed the closest agreement between estimated and observational data (R2=0.93). Predicted values from a Neural Network model and the Locally Weighted Smoother model showed also very good agreement to measured values of mercury flux (R2=0.92). A Regression Tree model demonstrated also a satisfactory predictability with a value of R2=0.90. Sensitivities and statistical analyses showed that surface soil mercury concentrations, solar radiation and, to a lesser degree, temperature are important parameters in predicting airborne Hg flux from terrestrial soils. These findings are compatible with results from recent experimental studies. Considering the uncertainties associated with mercury cycling and natural emissions, it is concluded, that predictions based on simple modeling techniques seem quite appropriate at present; they can be useful tools in evaluating the role of terrestrial emission sources as part of mercury modeling in local and regional airsheds. PMID:14533918

Tsiros, Ioannis X; Dimopoulos, Ioannis F

2003-01-01

126

Variations in Solar Activity and Irradiance and Their Implications for Energy Input Into the Terrestrial Atmosphere  

NASA Astrophysics Data System (ADS)

This dissertation presents research into the question of how variations in the physical properties of resolved solar magnetic surface features combine to produce variations in the physical properties of the integrated Sun and the possible impacts of those variations on the terrestrial climate system. The core approach to the research was development of techniques to apply automated Bayesian statistical pattern recognition methods as implemented in the AutoClass software to magnetic and intensity-like solar images from the Mount Wilson Solar Observatory (MWO) 150 Foot Solar Telescope. The goals were to: (1) identify in an objective and quantifiable manner the solar surface features responsible for changes in solar irradiance, (2) enhance understanding of the evolution of these features and the resultant solar irradiance variations over the most recent solar cycles, (3) develop methods to identify the specific features responsible for variations in specific wavelengths, (4) use global observations of global solar irradiance indices to identify the spatially resolved features which contribute to them, (5) attempt to apply these results to specific topics of current interest in solar-stellar astronomy. Using these techniques, a method was developed to identify classes of features from thousands of MWO solar images based on the per pixel values of absolute magnetic field strength and an intensity measure known as a "ratio-gram" in MWO images. Using these classes along with observations from independent, usually satellite based, sources in different wavelengths, models were constructed of total solar irradiance (TSI) and solar UV indices. These models were able to reproduce with high correlations solar observations in a number of different solar wavelengths. These classes were also used to construct images mapping different wavelength emissions to the areas to the solar surface features from which they originated. These techniques proved able to reproduce with high accuracy many of the different wavelengths comprising solar irradiance and to identify the features producing them on the solar surface. The results of this research imply constraints on the fraction of variations in solar TSI and other wavelength emissions which can be accounted for by magnetic field variations without resort to other explanatory mechanisms. These findings in turn imply constraints on the extent to which variations in solar irradiance may be a factor contributing to observed global warming. These findings include: (1) constraining possible non-magnetic sources of TSI variations to a range of 5--6% versus 10--20% in earlier research, suggesting a limitation on solar TSI forcing of terrestrial climate to the 0.1% solar cycle variations in magnetic activity and (2) a failure to find an upward minimum to minimum trend in TSI from Cycle 21/22 to 22/23 such as reported by others and the detection of a downward trend from the Cycle 22/23 to 23/24 minimum. The results are also useful diagnostics for the inference of the surface properties study of solar-type stars for which resolved spatial images are not available.

Parker, Daryl Gray

127

The early development of Gastrotheca riobambae and Colostethus machalilla, frogs with terrestrial reproductive modes  

NSDL National Science Digital Library

A Lecture (in English) on using two local (Equador) terrestrial frogs to learn about development; from the Model Organisms and Innovative Approaches in Developmental Biology Short Course in Sao Paolo, Brazil, April 2005. These are the PPT slides only, no associated audio or text is available.

Eugenia del Pino (Pontificia Universidad Catolica del Ecuador Biology)

2005-04-27

128

Measurements of biosphere-atmosphere exchange of CH? in terrestrial ecosystems.  

PubMed

This chapter focuses on methods for measuring CH(4) exchange between the biosphere and the atmosphere. In the context of the global importance of the biosphere as a source and a sink of atmospheric CH(4,) special emphasis is given to details of gas flux measurements. Due to their widespread use and suitability for targeted process studies, chamber techniques as a means for measuring CH(4) fluxes are highlighted. Besides detailed recommendations for measurements of fluxes with chambers, potential problems of the chamber technique are also discussed, such as changes in environmental conditions due to chamber installations. Further, a short overview is provided of how different pathways of CH(4) exchange, specifically plant-mediated transport, ebullition or diffusion, can be separated and quantified under field conditions. Finally, a short summary of micrometeorological CH(4) measuring techniques such as the eddy covariance method is provided. This technique relies on fast-response sonic anemometers and CH(4) analyzers (~10Hz) to make direct measurements of the vertical CH(4) flux at a point above the vegetation surface. PMID:21419928

Butterbach-Bahl, Klaus; Kiese, Ralf; Liu, Chunyan

2011-01-01

129

Early Giant Planet Migration in the Solar System: Geochemical and Cosmochemical Implications for Terrestrial Planet Formation  

NASA Astrophysics Data System (ADS)

A new terrestrial planet formation model (Walsh et al., this meeting) explores the effects of a two-stage, inward-then-outward migration of Jupiter and Saturn, as found in numerous hydrodynamical simulations of giant planet formation (Masset & Snellgrove 2001, Morbidelli & Crida 2007, Pierens & Nelson 2008). Walsh et al. show that the inward migration of Jupiter truncates the disk of planetesimals and embryos in the terrestrial planet region. Subsequent accretion in that region then forms a realistic system of terrestrial planets, in particular giving a low-mass Mars, which has been difficult to reproduce in simulations with a self-consistent set of initial conditions (see, eg. Raymond et al. 2009). Additionally, the outward migration of the giant planets populates the asteroid belt with distinct populations of bodies, with the inner belt filled by bodies originating inside of 3 AU, and the outer belt filled with bodies originating from beyond the giant planets. From a geochemical and cosmochemical point of view, this scenario differs significantly from the "standard model" in which essentially all of the material in the inner Solar System initially formed there. Specifically, the assumption that the current radial distribution of material in the inner Solar System is reflective of the primordial distribution of material in that region is no longer necessary. This is important for understanding the chemical and isotopic diversity of the inner Solar System as inferred from studies of the terrestrial planets, asteroids, and meteorites, as well as for understanding the origin of Earth's water. We will discuss the geochemical and cosmochemical implications of this model in relation to available constraints, as well as to previous models of terrestrial planet formation. Masset & Snellgrove (2001), MNRAS 320, L55. Morbidelli & Crida (2007), Icarus 191, 158. Pierens & Nelson (2008), A&A 482, 333. Raymond et al. (2009), Icarus 203, 644.

O'Brien, David P.; Walsh, K. J.; Morbidelli, A.; Raymond, S. N.; Mandell, A. M.; Bond, J. C.

2010-10-01

130

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

NASA Astrophysics Data System (ADS)

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.

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

131

Ancient Relatives of Algae Yield New Insights into Role of CO2 in Earth's Early Atmosphere  

NSF Publications Database

... Newsroom | Speeches | Priority Areas | What's Cool | Publications | Partners | History | About Us ... Yield New Insights into Role of CO2 in Earth's Early Atmosphere The microfossil that indicates ...

132

Calculation of infrared limb emission by ozone in the terrestrial middle atmosphere. 1. Source functions  

SciTech Connect

Two statistical equilibrium models are compared to analyze the departure from local thermodynamic equilibrium (LTE) in the vibration-rotation bands of ozone in the middle atmosphere. The bands that emit in the 9-11 {mu}m spectral interval depart from LTE due to chemical pumping, spontaneous emission, radiative absorption, and photochemical reaction. The diurnal variation in the {nu}{sub 1} and {nu}{sub 3} fundamental band source functions is determined by the diurnal changes in the rate of photolysis of ozone by solar radiation. The hot band source functions ({nu} > 2) are invariant above 85 km due to the diurnal invariance in the chemical pumping process. The magnitude of the hot-band source functions is uncertain because of the lack of understanding of the chemical pumping process. Collisional quenching of vibrationally excited ozone by atomic oxygen may reduce the magnitude of the {nu}{sub 3} and {nu}{sub 1} fundamental source functions by 10% near 100 km.

Milynczak, M.G. (NASA Langley Research Center, Hampton, VA (USA)); Drayson, S.R. (Univ. of Michigan, Ann Arbor (USA))

1990-09-20

133

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

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.

Stephen C. Piper

2005-10-15

134

The calculation of infrared limb emission by ozone in the terrestrial middle atmosphere  

SciTech Connect

The calculation of infrared limb emission from the middle atmosphere to space by ozone in the 9{mu}m to 11 {mu}m spectral region discussed. The departure from local thermodynamic equilibrium (LTE) in the vibration-rotation bands of ozone is investigated, considering the processes of collisional excitation, collisional quenching, chemical pumping, photochemical reaction loss, radiative emission and radiative absorption. As the database of kinetic and spectroscopic rates necessary to construct statistical equilibrium models is very sparse, three different models are developed and their results are compared. The source functions for the {nu}{sub 3} hot bands and combination bands are calculated from the surface to 110 km in altitude for noon and midnight conditions during mid-latitude winter. Source function enhancements relative to LTE are a result of the chemical pumping and radiative absorption processes. Diurnal variations in the source functions are a result of diurnally varying photochemical processes. The radiance emitted by ozone is calculated for six bands for two of the three statistical equilibrium models considered using a high-resolution, line-by-line infrared emission model. A maximum 32% difference in the spectrally integrated radiance between 925 cm{sup {minus}1} and 1,141 cm{sup {minus}1} exists between the two sets of model radiances for tangent paths in the upper mesosphere. The contribution to the total radiance due to emission from two combination bands of carbon dioxide (CO{sub 2}) that emit in the 9{mu}m to 11{mu}m spectral region is also calculated.

Mlynczak, M.G.

1989-01-01

135

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

136

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

Microsoft Academic Search

A simple climate model has been developed to investigate the existence of the small ice cap instability in the Southern Hemisphere.\\u000a The model consists of four coupled components: an atmospheric energy balance model, a thermodynamic snow-sea ice model, an\\u000a oceanic mixed layer model and a terrestrial ice model. Results from a series of experiments involving different degrees of\\u000a coupling in

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

1998-01-01

137

Photodissociation of molecular oxygen in the terrestrial atmosphere - Simplified numerical relations for the spectral range of the Schumann-Runge bands  

Microsoft Academic Search

A numerical method is presented for modeling the photodissociation of molecular oxygen in the spectral range 175-200 nm of the Schumann-Runge bands (19-0) to (2-0) in the terrestrial atmosphere. It is possible to obtain realistic photodissociation rates that are in good agreement with detailed and complete calculations by using the following simple increases of 20%, 15%, 10%, and 5% for

Marcel Nicolet

1984-01-01

138

Pronounced climate warming during early Middle Pleistocene interglacials: investigating the mid-Brunhes event in the British terrestrial sequence  

NASA Astrophysics Data System (ADS)

The mid-Brunhes event is a climatic transition that occurs between MIS 13 and 11 (ca 450,000 yrs B.P.) and is primarily characterised by an increase in the amount of warming received by interglacial episodes over the last 450,000 yrs relative to that experienced during interglacials of the early Middle Pleistocene (780,000 - 450,000 yrs B.P.). This event is observable within a range of long climate records (e.g. SPECMAP, EPICA etc) but its effect on terrestrial systems is poorly understood. The impact of this event in northwest Europe is tested through the British terrestrial sequence by the comparison of multi-proxy climate reconstructions for interglacials of the early Middle Pleistocene with climate reconstructions from the late Middle and Late Pleistocene (<500,000 B.P.). This comparison reveals that interglacial climates during the early Middle Pleistocene in Britain were, in fact, as warm as, and in some cases warmer than, those that occurred during the late Middle and Late Pleistocene. This suggestion is supported by sea surface temperature records in the North Atlantic which show that temperatures during the early Middle Pleistocene interglacials were at least as warm as the Holocene. There is therefore no evidence, in climate records of northwest Europe and the North Atlantic, for a mid-Brunhes event. This suggests that the mid-Brunhes event is not a global climatic transition but only impacts certain regions of the world, however, further work is needed to understand the extent of this significant transition and the reason for this regional variation.

Candy, I.; Rose, J.; Silva, B.; Lee, J.

2009-04-01

139

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

SciTech Connect

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.

King, A.W.

1986-01-01

140

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

PubMed

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

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

2011-11-30

141

Terrestrial Production vs. Extraterrestrial Delivery of Prebiotic Organics to the Early Earth (Abstract Only).  

National Technical Information Service (NTIS)

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 actuall...

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

1991-01-01

142

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

NASA Astrophysics Data System (ADS)

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.

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

2004-12-01

143

A consistent picture of early hydrodynamic escape of Venus atmosphere explaining present Ne and Ar isotopic ratios and low oxygen atmospheric content  

NASA Astrophysics Data System (ADS)

A time dependent model of hydrogen hydrodynamic escape powered by solar EUV flux and solar wind, and accounting for oxygen frictional escape, has been implemented in primitive Venus conditions. The model is constrained by the present 20Ne/ 22Ne and 36Ar/ 38Ar ratios in Venus atmosphere. It suggests that the net total amount of water delivered to the planet during accretion (? 10-100 Myr) is not in excess of the content of ? 5 Terrestrial Oceans (5 TO). In our preferred scenario, 60% of the oxygen (3 TO) is left behind the hydrogen during the first 100 Myr. From a comparison with Earth's case, we suggest that hydrodynamic escape has dried up Venus atmosphere early in its history (? 70 Myr), triggering the crystallization of the magma ocean, and leaving no available water in the atmosphere to condense out and form an Earth-size water ocean. On the contrary, Earth, possibly endowed with more water, and subject to a weaker hydrodynamic escape, would have remained wet after the crystallization of its magma ocean. We suggest that the oxygen left behind the escaping hydrogen during the main hydrodynamic phase on Venus has been dissolved in the magma ocean, and lost through oxidation. In the proposed scenario, the dense Venus CO 2 atmosphere doesn't result from an initial episode of runaway (or moist) greenhouse, but has been formed during the crystallization of the magma ocean, by progressive exsolution of carbon dioxide, at a time when the atmospheric partial pressure of water was of a few hundred bar. In the subsequent period, from ? 100 to ? 500 Myr, the hydrogen of the water delivered by comets may have been removed by continuing thermal escape, resulting at 500 Myr in a water global equivalent layer (GEL) of a few meters depth (or less), probably under the form of water vapor in the atmosphere, and a molecular oxygen atmosphere of ? 10 bar or so. At later times, pick-up ion escape may have removed most of the remaining water, and led to the present D/ H atmospheric enhancement factor of 150. The ? 10 bar of oxygen may have been absorbed by crustal oxidation.

Gillmann, Cédric; Chassefière, Eric; Lognonné, Philippe

2009-09-01

144

The recent shift in early summer Arctic atmospheric circulation  

NASA Astrophysics Data System (ADS)

The last six years (2007-2012) show a persistent change in early summer Arctic wind patterns relative to previous decades. The persistent pattern, which has been previously recognized as the Arctic Dipole (AD), is characterized by relatively low sea-level pressure over the Siberian Arctic with high pressure over the Beaufort Sea, extending across northern North America and over Greenland. Pressure differences peak in June. In a search for a proximate cause for the newly persistent AD pattern, we note that the composite 700 hPa geopotential height field during June 2007-2012 exhibits a positive anomaly only on the North American side of the Arctic, thus creating the enhanced mean meridional flow across the Arctic. Coupled impacts of the new persistent pattern are increased sea ice loss in summer, long-lived positive temperature anomalies and ice sheet loss in west Greenland, and a possible increase in Arctic-subarctic weather linkages through higher-amplitude upper-level flow. The North American location of increased 700 hPa positive anomalies suggests that a regional atmospheric blocking mechanism is responsible for the presence of the AD pattern, consistent with observations of unprecedented high pressure anomalies over Greenland since 2007.

Overland, James E.; Francis, Jennifer A.; Hanna, Edward; Wang, Muyin

2012-10-01

145

Parallel Computing for Terrestrial Ecosystem Carbon Modeling  

SciTech Connect

Terrestrial ecosystems are a primary component of research on global environmental change. Observational and modeling research on terrestrial ecosystems at the global scale, however, has lagged behind their counterparts for oceanic and atmospheric systems, largely because the unique challenges associated with the tremendous diversity and complexity of terrestrial ecosystems. There are 8 major types of terrestrial ecosystem: tropical rain forest, savannas, deserts, temperate grassland, deciduous forest, coniferous forest, tundra, and chaparral. The carbon cycle is an important mechanism in the coupling of terrestrial ecosystems with climate through biological fluxes of CO{sub 2}. The influence of terrestrial ecosystems on atmospheric CO{sub 2} can be modeled via several means at different timescales. Important processes include plant dynamics, change in land use, as well as ecosystem biogeography. Over the past several decades, many terrestrial ecosystem models (see the 'Model developments' section) have been developed to understand the interactions between terrestrial carbon storage and CO{sub 2} concentration in the atmosphere, as well as the consequences of these interactions. Early TECMs generally adapted simple box-flow exchange models, in which photosynthetic CO{sub 2} uptake and respiratory CO{sub 2} release are simulated in an empirical manner with a small number of vegetation and soil carbon pools. Demands on kinds and amount of information required from global TECMs have grown. Recently, along with the rapid development of parallel computing, spatially explicit TECMs with detailed process based representations of carbon dynamics become attractive, because those models can readily incorporate a variety of additional ecosystem processes (such as dispersal, establishment, growth, mortality etc.) and environmental factors (such as landscape position, pest populations, disturbances, resource manipulations, etc.), and provide information to frame policy options for climate change impact analysis.

Wang, Dali [ORNL; Post, Wilfred M [ORNL; Ricciuto, Daniel M [ORNL; Berry, Michael [University of Tennessee, Knoxville (UTK)

2011-01-01

146

Astrobiological Implications Of Differences In The Early Evolution Of The Terrestrial Planets (Earth, Mars, Venus)  

Microsoft Academic Search

The appearance of life on early Mars and Venus has been postulated on the grounds that the environmental conditions on these planets were similar. However, apart from the presence of water, an indigenous and exogenous source of organics, as well as various potential sources of energy (i.e. the vital ingredients for life), there are considerable differences in the early geological

F. Westall; A. Brack

2001-01-01

147

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)

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.

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

148

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

Microsoft Academic Search

The photochemistries of methane and HCN are discussed in the context of the primitive terrestrial atmosphere, using a detailed numerical model. In the absence of abundant O2, absorption of solar EUV (lambda<1023Å) by N2 provides a large thermospheric source of atomic nitrogen. Methane is oxidized cleanly and efficiently, provided CO2 is more abundant than CH4. Otherwise, a large fraction of

Kevin J. Zahnle

1986-01-01

149

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

NASA Astrophysics Data System (ADS)

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.

Hesselbo, Stephen P.; Pie?kowski, Grzegorz

2011-01-01

150

Early results from a terrestrial-marine BGC coupling study in Southeast Alaska  

NASA Astrophysics Data System (ADS)

In 2010 we began a long-term comparative study of watershed contributions to coastal marine nutrients in the northeast Pacific from a modest deployment of sensors combined with sample analysis. The preliminary results presented here establish a baseline for defining and subsequently tracking physical system parameters relevant to marine productivity over two decades, in two contexts: First in the context of research by Hood and others: Comparing glacier-covered to un-glaciated watershed output in a Lagrangian sense of particle and parcel transport. Second, in a more Eulerian sense: How will impact on coastal marine ecosystems from changing terrestrial freshwater input compare over decades to that of changes in physical parameters like pH, upwelling nutrient supply along the continental shelf and temperature? In our initial efforts we trolled two estuary plumes pulling samples for laboratory analysis and operating in situ sensors in tandem with GPS while other in situ sensors collected data from within source rivers (Eagle River and Peterson Creek near Juneau, AK, in respectively glaciated and forested watersheds). The strategy is to produce comparable synoptic datasets across the freshwater-marine mixing regime of the plume using salinity as a mixing proxy. Initial datasets include CDOM, dissolved oxygen, turbidity, chlorophyll-A, and (from samples) total organic carbon, total nitrogen, absorption spectra and excitation-emission matrices. Future work will expand this list to include mass spectrometer and NMR data. In working with this synoptic dataset we are faced with both curation and interpretation challenges; hence a primary objective of the project is to use the trans-disciplinary and data-intensive nature of the research problem set to motivate technology adoption. We have in mind here the notion of electronic publication (exemplified in this AGU poster) that permits collaborators and readers to reach back into source data and trace the origins and processes—normally obscured—that lead to the paper’s conclusions.

Fatland, D. R.; Vermilyea, A.; Spencer, R. G.; Hood, E. W.; Stubbins, A.

2010-12-01

151

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

USGS Publications Warehouse

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.

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

2007-01-01

152

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

SciTech Connect

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.

King, A.W.

1986-01-01

153

Faunal reorganisation in terrestrial mammalian communities: evidence from France during the Lateglacial-Early Holocene transition  

NASA Astrophysics Data System (ADS)

The Lateglacial-Early Holocene transition is characterized by rapid oscillations between warm and cold episodes. Their impact on ecosystem dynamics was particularly pronounced in north-western Europe where hunter-gatherer societies experienced a succession of environmental transformations, including the expansion and dispersal of biotic communities and changing herbivore habitats. Recent archaeozoological studies and AMS direct dating on mammalian bones/or bone collagen allow to map and precise this process at a supra-regional scale (France). At regional scales (i.e. Paris Basin & Jura-Northern French Alps), results indicate a rapid faunal reorganisation at the end of Lateglacial that will be presented in detail. Composition of faunal assemblages remains then unchanged during the Early Holocene. By contrast, significant herbivore habitat changes are recorded during the Early Holocene by other proxies (pollen data and isotopic data) and a decrease in Red Deer size through time is evidenced by osteometrical analyses. Hypotheses regarding the kind of adaptation process experienced by the faunal communities through time will be presented. Factors that may have controlled the observed changes will be discussed.

Bridault, Anne

2010-05-01

154

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...

155

Response of Early Cretaceous carbonate platforms to changes in atmospheric carbon dioxide levels  

Microsoft Academic Search

During the Late Barremian and Early Aptian (about 120 million years ago) intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere, and resulted most probably in rising atmospheric carbon dioxide pressure. In order to document the response of the shallow water carbonate-producing communities to this

Lukas Wissler; Hanspeter Funk; Helmut Weissert

2003-01-01

156

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

USGS Publications Warehouse

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.

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

2006-01-01

157

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

NASA Astrophysics Data System (ADS)

The photochemistries of methane and HCN are discussed in the context of the primitive terrestrial atmosphere, using a detailed numerical model. In the absence of abundant O2, absorption of solar EUV (? < 1023Å) by N2 provides a large thermospheric source of atomic nitrogen. Methane is oxidized cleanly and efficiently, provided CO2 is more abundant than CH4. Otherwise, a large fraction of the methane present is polymerized, forming alkanes in the troposphere and polyacetylenes and nitriles in the upper atmosphere. The combination of low O2, high N2, and moderately high levels of CO2 would have made the ancient terrestrial atmosphere a favorable environment for the production of HCN from CH4. Once formed, HCN is rather long-lived; it is removed from the atmosphere either by direct photodissociation at Ly ? (˜100 years) or by rainfall (˜10 years). Chemical loss would have been unimportant. Owing to its stability, transport of HCN from the top to the bottom of the atmosphere can be efficient; nevertheless, our results are sensitive to the assumed eddy diffusion profile. For small amounts of methane a small constant fraction of order 0.1% to 1% of the carbon in the methane is returned to the surface as hydrocyanic acid rain. For larger methane sources exceeding a critical value of order 1011 molecules cm-2 s-1 (corresponding to ƒ(CH4) of order 10-4-10-3), rainout of HCN increases abruptly to more than 10% of the carbon supplied as methane, limited by the primary production of N. Under favorable conditions, hydrolysis of HCN could have supported atmospheric NH3 mixing ratios approaching 1 ppm.

Zahnle, Kevin J.

1986-02-01

158

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)

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 C15 to C35n-alkanes, C8 to C34n-alkanoic acids, C12 to C30n-alkanols) and compound-specific stable isotopes (?13C of C29 and C31n-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 C29 (-25.6‰ to -34.5‰) and C31n-alkanes (-28.3‰ to -37‰) revealed heavier ?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.

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

2007-12-01

159

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

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.

Stephen C. Piper; Ralph F. Keeling

2012-01-03

160

Early results from improved limb atmospheric spectrometer (ILAS) measurements  

Microsoft Academic Search

Improved Limb Atmospheric Spectrometer (ILAS), which was developed by Environment Agency of Japan, was a satellite?borne sensor to observe chemical and dynamical environment of the stratospheric ozone layer from space. ILAS had been normally operating on board the Advanced Earth Observing Satellite (ADEOS) from the beginning of November 1996 to the end of June 1997 when the sudden failure of

Yasuhiro Sasano; Makoto Suzuki; Tatsuya Yokota; Hiroshi Kanzawa

1997-01-01

161

Biological modulation of planetary atmospheres: The early Earth scenario  

NASA Astrophysics Data System (ADS)

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.

Schidlowski, M.

162

Investigating Earth's Atmospheric Electricity: a Role Model for Planetary Studies  

Microsoft Academic Search

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as ``central tenets'',

K. L. Aplin; R. G. Harrison; M. J. Rycroft

2008-01-01

163

Investigating Earth's Atmospheric Electricity: a Role Model for Planetary Studies  

Microsoft Academic Search

The historical development of terrestrial atmospheric electricity is described, from its beginnings with the first observations of the potential gradient to the global electric circuit model proposed by C.T.R. Wilson in the early 20th century. The properties of the terrestrial global circuit are summarised. Concepts originally needed to develop the idea of a global circuit are identified as \\

K. L. Aplin; R. G. Harrison; M. J. Rycroft

2008-01-01

164

Model Atmospheres for the Early Stages of Novae in Outburst.  

National Technical Information Service (NTIS)

For the photospheres of classical novae during the early stages of their outbursts, continuum and line blanketed models are presented. The expanding envelopes are characterized by small density gradients that lead to very large geometrical extensions and ...

R. Wehrse P. H. Hauschildt G. Shaviv S. G. Starrfield

1990-01-01

165

GPS radio holography as a tool for remote sensing of the atmosphere, mesosphere, and terrestrial surface from space  

Microsoft Academic Search

.   GPS radio occultation (RO) signals are highly coherent and precise, and thus sufficient for holographic investigation of\\u000a the atmosphere, ionosphere, and the Earth's surface from space. In principle, three-dimensional radio-holographic remote sensing\\u000a is possible by using new radio holographic equations to retrieve the radio field within the atmosphere from a radio field\\u000a known at some interface outside the atmosphere.

Alexander Pavelyev; Yuei-An Liou; Christoph Reigber; Jens Wickert; Kiyoshi Igarashi; Klemens Hocke; Cheng-Yung Huang

2002-01-01

166

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

PubMed

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

Owen, T C; Bar-Nun, A

167

Fair weather atmospheric electricity  

NASA Astrophysics Data System (ADS)

Not long after Franklin's iconic studies, an atmospheric electric field was discovered in "fair weather" regions, well away from thunderstorms. The origin of the fair weather field was sought by Lord Kelvin, through development of electrostatic instrumentation and early data logging techniques, but was ultimately explained through the global circuit model of C.T.R. Wilson. In Wilson's model, charge exchanged by disturbed weather electrifies the ionosphere, and returns via a small vertical current density in fair weather regions. New insights into the relevance of fair weather atmospheric electricity to terrestrial and planetary atmospheres are now emerging. For example, there is a possible role of the global circuit current density in atmospheric processes, such as cloud formation. Beyond natural atmospheric processes, a novel practical application is the use of early atmospheric electrostatic investigations to provide quantitative information on past urban air pollution.

Harrison, R. G.

2011-06-01

168

Atmospheric composition and climate on the early Earth  

Microsoft Academic Search

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 858C. 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

James F. Kasting; M. Tazewell Howard

2006-01-01

169

Greenhouse warming by CH4 in the atmosphere of early Earth  

NASA Astrophysics Data System (ADS)

Earth appears to have been warm during its early history despite the faintness of the young Sun. Greenhouse warming by gaseous CO2 and H2O by itself is in conflict with constraints on atmospheric CO2 levels derived from paleosols for early Earth. Here we explore whether greenhouse warming by methane could have been important. We find that a CH4 mixing ratio of 10-4 (100 ppmv) or more in Earth's early atmosphere would provide agreement with the paleosol data from 2.8 Ga. Such a CH4 concentration could have been readily maintained by methanogenic bacteria, which are thought to have been an important component of the biota at that time. Elimination of the methane component of the greenhouse by oxidation of the atmosphere at about 2.3-2.4 Ga could have triggered the Earth's first widespread glaciation.

Pavlov, Alexander A.; Kasting, James F.; Brown, Lisa L.; Rages, Kathy A.; Freedman, Richard

2000-05-01

170

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)

A Dynamic Global Vegetation model is used as part of a simplified Earth system model to simulate the impact of human land use on Holocene atmospheric CO2 and the contemporary carbon cycle. We show that suggested upward revisions of Holocene land use reconstructions imply a smaller contemporary terrestrial carbon sink and that early agricultural activities did only marginally contribute to the late Holocene CO2 rise of 20 ppm measured on ice cores. Scenarios are used to test the robustness of the results. Simulated changes in atmospheric CO2 due to land use are less than 1 ppm before 0 AD and 22 ppm by 2004 AD when prescribing the HYDE 3.1 land use reconstruction over the past 12 000 years. Cumulative emissions are with 50 GtC by 1850 and 177 GtC by 2004 AD comparable to earlier estimates. In scenario H2, agricultural area from HYDE 3.1 is scaled by a factor of two before 1700 AD, thereby taking into account evidence that land area used per person was higher before than during early industrialisation. Then, the contemporary terrestrial carbon sink, required to close the atmospheric CO2 budget, is reduced by 0.5 GtC yr-1. CO2 changes due to land use change exceed natural interannual variability only after 1000 AD and are less than 4 ppmv until 1850 AD. Simulated CO2 change remains small even in scenarios where average land use per person is unrealistically increased by a factor of 4 to 8 above published estimates. Our results falsify the hypothesis that humans are responsible for the late Holocene CO2 increase and that anthropogenic land use prevented a new ice age.

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

2010-02-01

171

Terrestrial carbon sink in the Northern Hemisphere estimated from the atmospheric CO2 difference between Mauna Loa and the South Pole since 1959  

NASA Astrophysics Data System (ADS)

The diVerence between Mauna Loa and South Pole atmospheric CO2 concentrations from 1959 to the present scales linearly with CO2 emissions from fossil fuel burning and cement production (together called fossil CO2). An extrapolation to zero fossil CO2 emission has been used to suggest that the atmospheric CO2 concentration at Mauna Loa was 0.8ppm less than that at the South Pole before the industrial revolution, associated with a northward atmospheric transport of about 1 Gt C yr-1 (Keeling etal. 1989a). Mass conservation requires an equal southward transport in the ocean. However, our ocean general circulation and biogeochemistry model predicts a much smaller pre-industrial carbon transport. Here, we present a new analysis of the Mauna Loa and South Pole CO2 data, using a general circulation model and a 2-box model of the atmosphere. It is suggested that the present CO2 diVerence between Mauna Loa and the South Pole is caused by, in addition to fossil CO2 sources and sinks, a pre-industrial interhemispheric flux of 0.5 0.7 Gt C yr-1, and a terrestrial sink of 0.8 1.2 Gt C yr-1 in the mid-latitude Northern Hemisphere, balanced by a tropical deforestation source that has been operating continuously in the period from 1959 to the present.

Fan, Song-Miao.; Blaine, Tegan L.; Sarmiento, Jorge L.

1999-11-01

172

Greenhouse warming by CH4 in the atmosphere of early Earth  

Microsoft Academic Search

Earth appears to have been warm during its early history despite the faintness of the young Sun. Greenhouse warming by gaseous CO2 and H2O by itself is in conflict with constraints on atmospheric CO2 levels derived from paleosols for early Earth. Here we explore whether greenhouse warming by methane could have been important. We find that a CH4 mixing ratio

Alexander A. Pavlov; James F. Kasting; Lisa L. Brown; Kathy A. Rages; Richard Freedman

2000-01-01

173

Production of nitrogen oxides by lightning in a methane-rich early atmosphere  

NASA Astrophysics Data System (ADS)

The composition of the early Earth's atmosphere is not known. Assuming that rapid weathering of fragments from impacts took placed and efficient sequestration of carbon occurred in the Earth's mantle, the early atmosphere would have been mostly composed of molecular nitrogen with low concentrations of carbon dioxide (less than percent). In order preserve the existence of oceans, it is required to warm up the atmosphere almost exclusively with methane [1]. Predicted methane concentrations in the distant past range from few ppm to several thousand ppm. Photochemical models predict a production rate of hydrogen cyanide of the order of 6 Tg/yr in a 3 percent carbon dioxide atmosphere with 1000 ppm of methane [2]. When the atmospheric levels of carbon dioxide dropped to 0.3 percent but with the methane levels of 1000 ppm, the production rate of hydrogen cyanide increased up to 20 Tg/yr [2]. The nitrogen fixation rate by lightning in atmospheres dominated bymolecula nitrogen, less than 10 percent carbon dioxide, and the absence of methane has been reported by Navarro-Gonzalez et al. [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 0.5percent of carbon dioxide with methane concentrations from 0 to 10,000 ppm in molecular nitrogen. Our results show that the main nitrogen fixation products by lightning are nitric oxide, nitrous oxide and methyl nitrite. Preliminary estimates indicate that the production of nitric oxide is not dependent on the initial concentration of methane and that its production rate decreases from about 0.02 Tg/yr to about 0.003 Tg/yr in atmospheres ranging from 10 to 0.5 percent of carbon dioxide, respectively. Nitrous oxide is produced by lightning is the contemporaneous oxygenated Earth's atmosphere [4], but has not been detected in nitrogen-carbon dioxide mixtures in the absence of oxygen [5]. This is the first report for the production of methylnitrate by lightning in the early atmosphere. Further analyses are underway to accurately determine the production rates of these nitrogen oxides by lightning, and to understand their role for chemical evolution and early Earth's climate. Zahnle, K. J. Photochemistry of methane and the formation of hydrocyanic acid (HCN) in the Earths early atmosphere. J. Geophys. Res. 91, 2819-2834 (1986); [2] Tian, F., Kasting, J.F., and Zahnle, K. Revisiting HCN formation in Earth's early atmosphere. Earth Planet. Sci. Lett. 308, 417-423 (2011); [3] Navarro-González, R., McKay, C.P. and Nna Mvondo, D. A possible nitrogen crisis for archaean life due to reduced nitrogen fixation by lightning, Nature 412, 61-64 (2001); [4] Levine, J.S., Hughes, R.E., Chameides, W.L., and Howell, W.E. N20 and CO Production by Electrical Discharges: Atmospheric Implications, Geophys. Res. Lett.,6, 557-559 (1979); [5] Nna Mvondo, D. Navarro-González, R, McKay, C.P., Coll, P. and Raulin, F. Production of nitrogen oxides by lightning and coronae discharges in simulated early Earth, Venus and Mars environments. Adv Space Res. 27(2), 217-223 (2001).

Navarro, Karina; Navarro-Gonzalez, Rafael; McKay, Christopher

2013-04-01

174

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...

175

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

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.

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

176

Simulations of the Atmospheres of Synchronously Rotating Terrestrial Planets Orbiting M Dwarfs: Conditions for Atmospheric Collapse and the Implications for Habitability  

Microsoft Academic Search

Planets within the habitable zones of M dwarfs are likely to be synchronous rotators; in other words, one side is permanently illuminated while the other side is in perpetual darkness. We present results of three-dimensional simulations of the atmospheres of such planets, and comment on their possible habitability. Near the ground, a thermally direct longitudinal cell exists, transporting heat from

M. M. Joshi; R. M. Haberle; R. T. Reynolds

1997-01-01

177

The inception of the oceans and CO2-atmosphere in the early history of the Earth  

NASA Astrophysics Data System (ADS)

After accretion and solidification of a “magma ocean”, the proto-atmosphere of the Earth is modeled to compose of 560 bar of H2O and 100 bar of CO2. The existence of a CO2-rich atmosphere in the early history of the Earth has been envisaged and supported by earlier studies. The results of the present study suggest that the oceans started to grow when the surface temperature of the Earth cooled to below approximately 300 450 °C. This study further suggests that CO2 was removed away from the early atmosphere as a dense supercritical H2O CO2 mixture during condensation (or the growing ocean), and then formed carbonate rocks in early geological history. The scenario of early growth of the oceans is in line with the geochemical evidence revealed recently from detrital zircons 4.4 Gyr old. A large-scale hydrosphere probably never existed on Venus, and not for long, on Mars. Thus, the atmospheres of these latter planets are composed mainly of carbon dioxide.

Liu, Lin-Gun

2004-11-01

178

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

Microsoft Academic Search

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

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

2007-01-01

179

Investigating the Early Atmospheres of Earth and Mars through Rivers, Raindrops, and Lava Flows  

NASA Astrophysics Data System (ADS)

The discovery of a habitable Earth-like planet beyond our solar-system will be remembered as one of the major breakthroughs of 21st century science, and of the same magnitude as Copernicus' heliocentric model dating from the mid 16th century. The real astrobiological breakthrough will be the added results from atmospheric remote sensing of such planets to determine habitability. Atmospheres, in both concentration and composition are suggestive of processes occurring at the planetary surface and upper crust. Unfortunately, only the modern Earth's atmosphere is known to be habitable. I investigate the density and pressure of our planet's early atmosphere before the rise of oxygen 2.5 billion years ago, because our planet was very much alive microbially. Such knowledge gives us another example of a habitable atmosphere. I also investigates the atmosphere of early Mars, as geomorphic signatures on its surface are suggestive of a past where liquid water may have present in a warmer climate, conditions suitable for the emergence of life, compared with today's 6 mbar CO2-dominated atmosphere. Using tools of fluvial geomorphology, I find that the largest river-valleys on Mars do not record a signature of a sustained hydrological cycle, in which precipitation onto a drainage basin induces many cycles of water flow, substrate incision, water ponding, and return to the atmosphere via evaporation. Rather, I conclude that while episodes of flow did occur in perhaps warmer environments, those periods were short-lived and overprinted onto a dominantly cold and dry planet. For Earth, I develop a new method of investigating atmospheric density and pressure using the size of raindrop imprints, and find that raindrop imprints preserved in the 2.7 billion year old Ventersdorp Supergroup of South Africa are consistent with precipitation falling in an atmosphere of near-surface density < 2 kg/m3 and probably > 0.1 kg/m3, compared to a modern value of 1.2 kg/m3, further suggesting a nitrogen level of at most twice present levels and perhaps well below present levels. To constrain this further, I re-evaluate a published paleobarometry technique using the vesicle size-distribution in simply emplaced lava flows and apply it to sea-level erupted lava flows from the 2.7 billion year old Fortescue group of Western Australia. Results from three flows suggest a range for atmospheric pressure 0.07 < Patm < 0.64 atm, which has profound consequences for our interpretation of the history of the nitrogen cycle by implying that the development of the nitrogenase enzyme necessary for nitrogen fixation happened very early on in the development of life.

Som, Sanjoy M.

2010-11-01

180

Atmospheric Phosphorus Deposition in Ashiu, Central Japan – Source Apportionment for the Estimation of True Input to a Terrestrial Ecosystem  

Microsoft Academic Search

Atmospheric bulk depositions of soluble reactive phosphorus (SRP), soluble unreactive phosphorus (SUP), particulate inorganic\\u000a phosphorus (PIP), particulate organic phosphorus (POP), total phosphorus (TP) and some other dissolved and particulate components\\u000a were monitored for 3 years in Ashiu, Central Japan. The mean bulk depositions of SRP, SUP, PIP, POP, TP, dissolved components\\u000a (Na, Mg, nss-Ca, K, V, Mo, nss-SO4) and particulate components

Seigen Tsukuda; Masahito Sugiyama; Yunosuke Harita; Kazuo Nishimura

2006-01-01

181

Plate Tectonics and Terrestrial Carbon Isotope Records  

NASA Astrophysics Data System (ADS)

In 2001, we reported a negative excursion in early-Aptian atmospheric ?13CO2 (? = -3.6 to -6.5‰), based on ?13C analyses of organic matter and land-plant isolates from coarsely-sampled Colombian estuarine and near-shore sediments. Here we present similar results for an Aptian section of the Arundel Clay (Potomac Group, central Maryland), which is well-known for its exceptional preservation of terrestrial plant materials. Sampling across 13 meters of sediment at ~10-cm intervals revealed a clear shift in the ?13C of terrestrial organic matter (n=153) and land-plant isolates (n=33) of ? = -2.3 and -2.9 ‰, respectively. The shift was observed within palynological Zone I, which is temporally well-correlated with our previous work. Using an empirical relationship between ?13Cplant and ?13Catm, we calculated ??13Catm = -2.1 to -2.6 ‰ during the early Aptian from the Arundel Clay shift. Given the probable composition of the early Cretaceous atmosphere, mass balance calculations favor a methane hydrate release as the cause of this excursion. In consideration of a mechanism for methane release, we calculated changes in global subduction indicated by the well-established and rapid 2-fold increase in seafloor production that was unique within the early Aptian compared to the last 144 million years. We show that increased frictional interaction between overriding and subducting plates caused uplift and compression sufficient to continuously destabilize a portion of the probable methane hydrate reservoir, thus creating a perturbation in the C-isotope record of the Aptian atmosphere, as reflected in the ?13C of terrestrial photosynthesizers. The Aptian methane release is a new example of mechanistic coupling between major tectonic events and the global biosphere.

Jahren, H.; Conrad, C.; Arens, N.

2005-12-01

182

Isotopic Composition of Lu in Terrestrial Samples and Achondrites: Implications for Lu-Hf Systematics in the Early Solar System  

NASA Astrophysics Data System (ADS)

The isotopic composition of Lu in terrestrial samples and achondrites is invariant to a precision of ~0.1‰. This is inconsistent with accelerated decay of ^176Lu as a mechanism for observed ^176Hf excess in meteorites older than 4556 Ma.

Wimpenny, J. B.; Amelin, Y.; Yin, Q.-Z.

2013-09-01

183

Two high resolution terrestrial records of atmospheric Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland.  

PubMed

Environmental archives like peat deposits allow for the reconstruction of both naturally and anthropogenically forced changes in the biogeochemical cycle of Pb as well as the quantification of past and present atmospheric Pb pollution. However, records of atmospheric Pb deposition from pre-industrial times are lacking. In a publication by Weiss et al. [Weiss, D., Shotyk, W., Boyle, E.A., Kramers, J.D., Appleby, P.G., Cheburkin, A.K., Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs. Sci Total Environ 2002;292:7-18]. Pb isotopes data measured by Q-ICP-MS and TIMS, concentration and enrichment data was presented for sites in eastern Canada (PeW1) and northwestern Scotland (LL7c), dating to 1586 A.D and 715 A.D., respectively. Here these same cores are re-analysed for Pb isotopes by MC-ICP-MS thereby acquiring 204Pb data and improving on the original data in terms of resolution and temporal coverage. Significant differences were found between the Q-ICP-MS/TIMS and MC-ICP-MS measurements, particularly at PeW1. These discrepancies are attributed to the problematic presence of organic matter during sample preparation and analysis complicated by the heterogeneity of the organic compounds that survived sample preparation steps. The precision and accuracy of Pb isotopes in complex matrices like peat is not always well estimated by industrial standards like NIST-SRM 981 Pb. Lead pollution histories at each site were constructed using the MC-ICP-MS data. The entire LL7c record is likely subject to anthropogenic additions. Contributions from local mining were detected in Medieval times. Later, coal use and mining in Scotland, Wales and England became important. After industrialization (ca. 1885 A.D.) contributions from Broken Hill type ores and hence, leaded petrol, dominate atmospheric Pb signatures right up to modern times. At PeW1 anthropogenic impacts are first distinguishable in the late 17th century with the mining and use of local coal. After industrialization (ca. 1810 A.D.), coal and petrol are the main Pb sources. A comprehensive estimate of the natural atmospheric background 206Pb/207Pb signature in eastern Canadian aerosols is made with a value of approximately 1.19. PMID:19062075

Kylander, Malin E; Weiss, Domink J; Kober, Bernd

2008-12-04

184

Terrestrial carbon sequestration potential  

Microsoft Academic Search

Fossil fuel use and land use change that began over 200 years ago are driving the rapid increase in atmospheric content of CO2 and other greenhouse gases that may be impacting on climatic change. Enhanced terrestrial uptake of CO2 over the next 50 to 100 years has been suggested as a way to reclaim the 150 or more Pg carbon

METTING Blaine

185

Modelling of Meteoroid Fragments Motion in the Atmosphere. A Method of Calculation of a Terrestrial Crater Field  

NASA Astrophysics Data System (ADS)

A meteoric body has great loading during its passage through the atmosphere. A meteoroid collapses when aerodynamic pressure on front surface reaches the critical value equals to durability of a body material. Its fragments separate in a transverse direction as a result of interaction of shock waves. Besides, smaller fragments decelerate more than large ones. Thus, there is a separation in a longitudinal direction also. Modelling of two fragments movement in the atmosphere is carried out in this work. Two cases are considered: scattering of two identical fragments in transverse direction and scattering of two fragments of different radii simultaneously in a longitudinal and transverse direction. Bodies capable to form a crater on the surface of the earth are considered in this work, i.e. large bodies with the big initial velocities are considered. A quite simple analytical expression of transverse velocity of fragment through parameters of the body material (strength and density) and repulsive force coefficient for two identical fragments is obtained. In the case of fragments of different mass a smaller fragment decelerate more in comparison with large one and a smaller fragment more separates from the trajectory of a main body in transverse direction. In the case of different fragments a transverse velocity depends on a quotient of fragments radii. A numerical solution of combined equations of deceleration and ablation is used for description of a longitudinal movement of a parent body and its fragments. Calculations according to proposed models and an estimation of separation distance of fragments in the atmosphere are carried out in the work. A calculation method of a size of an elliptic crater field is offered and calculation on example of Sikhote-Alin crater field is carried out in the work. This work was supported by the Russian Foundation for Basic Research, project no. 07-01-00009

Barri, Natalia

2008-09-01

186

Evolution of High Temperature Early Atmosphere Under the Interaction of H2O-CO2 Supercritical Fluid With Minerals  

Microsoft Academic Search

The evolution of atmosphere-lithosphere system of the early Earth is controlled by mutual interaction of high temperature atmosphere with rocks and minerals. It is assumed that the total pressure of the early atmosphere and the surface temperature above initial magma ocean are 26MPa (H2O 20MPa, CO2 6MPa) and 130-330° C, respectively. This composition, temperature and pressure are very close to

H. Isobe; T. Tomita; K. Ikeda

2004-01-01

187

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

USGS Publications Warehouse

Channels on the Martian surface suggest that Mars had an early, relatively thick atmosphere. If the atmosphere was thick enough for water to be stable at the surface, CO2 in the atmosphere would have been fixed as carbonates on a relatively short time scale, previously estimated to be 1 bar every 107 years. This loss must have been offset by some replenishment mechanism to account for the numerous valley networks in the oldest surviving terrains. Impacts could have released CO2 into the atmosphere by burial, by shock-induced release during impact events, and by addition of carbon to Mars from the impacting bolides. Depending on the relationship between the transient cavity diameter and the diameter of the resulting crater, burial rates as a result of impact gardening at the end of heavy bombardment are estimated to range from 20 to 45 m/106 years, on the assumption that cratering rates in Mars were similar to those of the Nectarian Period on the Moon. At these rates 0.1-0.2 bar of CO2 could have been released every 107 years as a result of burial to depths where dissociation temperatures of carbonates were reached. Modeling of large impacts suggests that an additional 0.01 to 0.02 bar of CO2 could have been released every 107 years during the actual impacts. In the unlikely event that all the impacting material was composed of carbonaceous chondrites, a further 0.3 bar of CO2 could have been added to the atmosphere every 107 years by oxidation of meteoritic carbon. Even when supplemented by the volcanically induced release of CO2, these release rates are barely sufficient to sustain an early atmosphere if water were continuously present at the surface. The results suggest that water may have been only intermittently present on the surface early in the planet's history. ?? 1989.

Carr, M. H.

1989-01-01

188

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

NASA Astrophysics Data System (ADS)

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.

Stothers, R. B.

1989-09-01

189

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)

Global mapping of terrestrial vegetation fluorescence from space has recently been accomplished with high spectral resolution (?/??>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 (?/?? ∼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.

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

2012-01-01

190

Early reproduction and increased reproductive allocation in metal-adapted populations of the terrestrial isopod Porcellio scaber  

Microsoft Academic Search

Organisms inhabiting metal-contaminated areas can be stressed by metal exposure and are possibly subject to selection, resulting\\u000a in increased metal tolerance and changes in growth and\\/or reproduction characteristics. In a previous study it was found that\\u000a in the terrestrial isopod Porcellio scaber, sampled from the vicinity of a zine smelter, the body size was small and the brood size was

M. H. Donker; C. Zonneveld; N. M. van Straalen

1993-01-01

191

Waves and weathering at 3.7 Ga: Geological evidence for an equitable terrestrial climate under the faint early Sun  

Microsoft Academic Search

Chemical sedimentary rocks such as banded iron formation (BIF) and pillow basalts are persistent features of the oldest volcanic and sedimentary record by 3.8–3.7 Ga, and are direct evidence for oceans by the start of the Archean. However, their presence does not dictate an equitable 3.8–3.7 Ga terrestrial climate. This is because they could have formed in oceans below global

A. P. Nutman; V. C. Bennett; C. R. L. Friend

2011-01-01

192

Waves and weathering at 3.7 Ga: Geological evidence for an equitable terrestrial climate under the faint early Sun  

Microsoft Academic Search

Chemical sedimentary rocks such as banded iron formation (BIF) and pillow basalts are persistent features of the oldest volcanic and sedimentary record by 3.8–3.7 Ga, and are direct evidence for oceans by the start of the Archean. However, their presence does not dictate an equitable 3.8–3.7 Ga terrestrial climate. This is because they could have formed in oceans below global

A. P. Nutman; V. C. Bennett; C. R. L. Friend

2012-01-01

193

Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change  

NASA Astrophysics Data System (ADS)

The relationship between atmospheric carbon dioxide (CO2) and climate in the Quaternary period has been extensively investigated, but the role of CO2 in temperature changes during the rest of Earth's history is less clear. The range of geological evidence for cool periods during the high CO2 Mesozoic `greenhouse world' of high atmospheric CO2 concentrations, indicated by models and fossil soils, has been particularly difficult to interpret. Here, we present high-resolution records of Mesozoic and early Cenozoic atmospheric CO2 concentrations from a combination of carbon-isotope analyses of non-vascular plant (bryophyte) fossils and theoretical modelling. These records indicate that atmospheric CO2 rose from ~420p.p.m.v. in the Triassic period (about 200 million years ago) to a peak of ~1,130p.p.m.v. in the Middle Cretaceous (about 100 million years ago). Atmospheric CO2 levels then declined to ~680p.p.m.v. by 60 million years ago. Time-series comparisons show that these variations coincide with large Mesozoic climate shifts, in contrast to earlier suggestions of climate-CO2 decoupling during this interval. These reconstructed atmospheric CO2 concentrations drop below the simulated threshold for the initiation of glaciations on several occasions and therefore help explain the occurrence of cold intervals in a `greenhouse world'.

Fletcher, Benjamin J.; Brentnall, Stuart J.; Anderson, Clive W.; Berner, Robert A.; Beerling, David J.

2008-01-01

194

Early multiplatform results from the International Solar Terrestrial Physics/Global Geospace Science (ISTP/GGS) Program  

NASA Astrophysics Data System (ADS)

This issue of the Geophysical Research Letters is the third† to contain a special section devoted to science results from the Global Geospace Science (GGS) Program [Acuna et al, 1995], a key component of the International Solar Terrestrial Physics Program. Designed to provide coverage of key regions of geospace, the GGS suite of spacecraft (WIND, POLAR, and GEOTAIL), along with other currently operational spacecraft, and related groundbased and theoretical support assets are intended to make a significant improvement in our understanding of the flow of energy, mass, and momentum in the solar-terrestrial environment.With the WIND spacecraft monitoring the upstream interplanetary medium and providing the solar wind input to the magnetosphere, with POLAR measuring plasma input into the magnetosphere and monitoring the Earth's auroral signature, and GEOTAIL observing the geomagnetic tail response, the principal regions of geospace where energy is transported and stored are sampled by an advanced array of instruments. Simultaneous groundbased investigations and theoretical and global modelling round out the synergistic approach to answering key questions concerning how individual parts of this closely-coupled system work together. The papers in this special section of GRL emphasize this multi-spacecraft, multi-discipline approach to solar-terrestrial observations. The ISTP/GGS program works best when all the elements are working together, and in this issue the value of coordinated, simultaneous observations with multiple platforms is amply demonstrated.

Desch, M.; Ogilvie, K.; Acuna, M.; Fairfield, D.; Hoffman, R.

195

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

SciTech Connect

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.

Thomas, P.A.

2000-06-01

196

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)

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.

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

197

Global Terrestrial Observing System  

NSDL National Science Digital Library

The Global Terrestrial Observing System (GTOS) is used to facilitate communication regarding world ecological research networks. There are also tools on this website to describe the three regional observation programs in Southern Africa and Central and Eastern Europe. The shared information includes data on Net Primary Production (NPP), Terrestrial Carbon Observation (TCO), Terrestrial Panel on Climate (TOPC), and Global Observation of Landcover Dynamics. Users can also access Terrestrial Ecosystem Monitoring Sites (TEMS), which concentrate on remote sensing data collection from over 500 individual sites located in primarily mountain or coastal regions. The TEMS program began in the early 1990's and is the international equivalent of Long Term Ecological Research sites found primarily in North America. TEMS are used to link ground and remotely sensed observations as well as to provide temporal assessment of ecological conditions. Other general data collected includes land quality, water resources, climate change, biodiversity, pollution and toxicity, global/ regional/ national environments, and international conventions.

2002-01-17

198

Early Holocene M~6 explosive eruption from Plosky volcanic massif (Kamchatka) and its tephra as a link between terrestrial and marine paleoenvironmental records  

NASA Astrophysics Data System (ADS)

We report tephrochronological and geochemical data on early Holocene activity from Plosky volcanic massif in the Kliuchevskoi volcanic group, Kamchatka Peninsula. Explosive activity of this volcano lasted for ~1.5 kyr, produced a series of widely dispersed tephra layers, and was followed by profuse low-viscosity lava flows. This eruptive episode started a major reorganization of the volcanic structures in the western part of the Kliuchevskoi volcanic group. An explosive eruption from Plosky (M~6), previously unstudied, produced tephra (coded PL2) of a volume of 10-12 km3 (11-13 Gt), being one of the largest Holocene explosive eruptions in Kamchatka. Characteristic diagnostic features of the PL2 tephra are predominantly vitric sponge-shaped fragments with rare phenocrysts and microlites of plagioclase, olivine and pyroxenes, medium- to high-K basaltic andesitic bulk composition, high-K, high-Al and high-P trachyandesitic glass composition with SiO2 = 57.5-59.5 wt%, K2O = 2.3-2.7 wt%, Al2O3 = 15.8-16.5 wt%, and P2O5 = 0.5-0.7 wt%. Other diagnostic features include a typical subduction-related pattern of incompatible elements, high concentrations of all REE (>10× mantle values), moderate enrichment in LREE (La/Yb ~ 5.3), and non-fractionated mantle-like pattern of LILE. Geochemical fingerprinting of the PL2 tephra with the help of EMP and LA-ICP-MS analyses allowed us to map its occurrence in terrestrial sections across Kamchatka and to identify this layer in Bering Sea sediment cores at a distance of >600 km from the source. New high-precision 14C dates suggest that the PL2 eruption occurred ~10,200 cal BP, which makes it a valuable isochrone for early Holocene climate fluctuations and permits direct links between terrestrial and marine paleoenvironmental records. The terrestrial and marine 14C dates related to the PL2 tephra have allowed us to estimate an early Holocene reservoir age for the western Bering Sea at 1,410 ± 64 14C years. Another important tephra from the early Holocene eruptive episode of Plosky volcano, coded PL1, was dated at 11,650 cal BP. This marker is the oldest geochemically characterized and dated tephra marker layer in Kamchatka to date and is an important local marker for the Younger Dryas—early Holocene transition. One more tephra from Plosky, coded PL3, can be used as a marker northeast of the source at a distance of ~110 km.

Ponomareva, Vera; Portnyagin, Maxim; Derkachev, Alexander; Pendea, I. Florin; Bourgeois, Joanne; Reimer, Paula J.; Garbe-Schönberg, Dieter; Krasheninnikov, Stepan; Nürnberg, Dirk

2013-04-01

199

Early Holocene M~6 explosive eruption from Plosky volcanic massif (Kamchatka) and its tephra as a link between terrestrial and marine paleoenvironmental records  

NASA Astrophysics Data System (ADS)

We report tephrochronological and geochemical data on early Holocene activity from Plosky volcanic massif in the Kliuchevskoi volcanic group, Kamchatka Peninsula. Explosive activity of this volcano lasted for ~1.5 kyr, produced a series of widely dispersed tephra layers, and was followed by profuse low-viscosity lava flows. This eruptive episode started a major reorganization of the volcanic structures in the western part of the Kliuchevskoi volcanic group. An explosive eruption from Plosky (M~6), previously unstudied, produced tephra (coded PL2) of a volume of 10-12 km3 (11-13 Gt), being one of the largest Holocene explosive eruptions in Kamchatka. Characteristic diagnostic features of the PL2 tephra are predominantly vitric sponge-shaped fragments with rare phenocrysts and microlites of plagioclase, olivine and pyroxenes, medium- to high-K basaltic andesitic bulk composition, high-K, high-Al and high-P trachyandesitic glass composition with SiO2 = 57.5-59.5 wt%, K2O = 2.3-2.7 wt%, Al2O3 = 15.8-16.5 wt%, and P2O5 = 0.5-0.7 wt%. Other diagnostic features include a typical subduction-related pattern of incompatible elements, high concentrations of all REE (>10× mantle values), moderate enrichment in LREE (La/Yb ~ 5.3), and non-fractionated mantle-like pattern of LILE. Geochemical fingerprinting of the PL2 tephra with the help of EMP and LA-ICP-MS analyses allowed us to map its occurrence in terrestrial sections across Kamchatka and to identify this layer in Bering Sea sediment cores at a distance of >600 km from the source. New high-precision 14C dates suggest that the PL2 eruption occurred ~10,200 cal BP, which makes it a valuable isochrone for early Holocene climate fluctuations and permits direct links between terrestrial and marine paleoenvironmental records. The terrestrial and marine 14C dates related to the PL2 tephra have allowed us to estimate an early Holocene reservoir age for the western Bering Sea at 1,410 ± 64 14C years. Another important tephra from the early Holocene eruptive episode of Plosky volcano, coded PL1, was dated at 11,650 cal BP. This marker is the oldest geochemically characterized and dated tephra marker layer in Kamchatka to date and is an important local marker for the Younger Dryas—early Holocene transition. One more tephra from Plosky, coded PL3, can be used as a marker northeast of the source at a distance of ~110 km.

Ponomareva, Vera; Portnyagin, Maxim; Derkachev, Alexander; Pendea, I. Florin; Bourgeois, Joanne; Reimer, Paula J.; Garbe-Schönberg, Dieter; Krasheninnikov, Stepan; Nürnberg, Dirk

2013-09-01

200

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

SciTech Connect

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.

Pan, Y. [Marine Biological Lab., Woods Hole, MA (United States)

1995-06-01

201

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

PubMed

Declining CO(2) over the Cretaceous has been suggested as an evolutionary driver of the high leaf vein densities (7-28 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-CO(2) regime would be lost as CO(2) concentrations increased but also implied that plants with very low vein densities (less than 3 mm mm(-2)) should experience substantial disadvantages with high CO(2). Thus, the hypothesized relationship between CO(2) and plant evolution can be tested through analysis of the concurrent histories of alternative lineages, because an extrinsic driver like atmospheric CO(2) should affect all plants and not just the flowering plants. No such relationship is seen. Regardless of CO(2) 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 CO(2), productivity changes are likely to have been limited before a substantial increase accompanying the evolution of flowering plants. PMID:22689947

Boyce, C Kevin; Zwieniecki, Maciej A

2012-06-11

202

Haze aerosols in the atmosphere of early Earth: manna from heaven.  

PubMed

An organic haze layer in the upper atmosphere of Titan plays a crucial role in the atmospheric composition and climate of that moon. Such a haze layer may also have existed on the early Earth, providing an ultraviolet shield for greenhouse gases needed to warm the planet enough for life to arise and evolve. Despite the implications of such a haze layer, little is known about the organic material produced under early Earth conditions when both CO(2) and CH(4) may have been abundant in the atmosphere. For the first time, we experimentally demonstrate that organic haze can be generated in different CH(4)/CO(2) ratios. Here, we show that haze aerosols are able to form at CH(4) mixing ratios of 1,000 ppmv, a level likely to be present on early Earth. In addition, we find that organic hazes will form at C/O ratios as low as 0.6, which is lower than the predicted value of unity. We also show that as the C/O ratio decreases, the organic particles produced are more oxidized and contain biologically labile compounds. After life arose, the haze may thus have provided food for biota. PMID:15684721

Trainer, Melissa G; Pavlov, Alexander A; Curtis, Daniel B; McKay, Christopher P; Worsnop, Douglas R; Delia, Alice E; Toohey, Darin W; Toon, Owen B; Tolbert, Margaret A

2004-01-01

203

New Ni and Co metal-silicate partitioning data and their relevance for an early terrestrial magma ocean  

NASA Astrophysics Data System (ADS)

It is generally assumed that the abundances of the siderophile (metal-loving) elements in the Earth's mantle are the result of core formation in the early Earth. In the most popular model the low contents of siderophile elements in the Earth's mantle are the result of metal-silicate equilibration followed by metal accumulation at the base of a magma ocean. This model is primarily based on the pressure dependence of Ni and Co metal-silicate partition coefficients first determined by Li and Agee [Li, J., Agee, C.B., 1996. Geochemistry of mantle core differentiation at high pressures. Nature 381, 686 689]. We have undertaken a further test of this hypothesis by performing a large number of additional partition experiments with the two key elements Ni and Co at a variety of temperatures and a pressure range extending from ambient pressure to 25 GPa (~ 750 km depth in the Earth). The unexpected result of the new experiments is the recognition of two pressure regimes in the temperature and pressure dependences of Ni Fe and to a lesser extent of Co Fe exchange metal-silicate partition coefficients, KDNi Fe and KDCo Fe. The strong pressure and temperature dependences of KD*Ni Fe and KD*Co Fe at atmospheric pressure change below about 5 GPa to much weaker dependences at higher pressures. As a consequence the pressure dependences of KDNi Fe and KDCo Fe cannot be regressed with a single fit over the entire pressure range. Fits based on partition data obtained in this work and from the literature between 5 GPa and 25 GPa were extrapolated to pressures and temperatures to lower mantle liquidus conditions. The Co Fe partition coefficients required to satisfy the present mantle composition is reached at about 35 GPa, whereas the proper Ni Fe ratio requires 45 to 50 GPa. At 55 GPa Ni and Co partition coefficients would be identical but the Ni- and Co-contents imposed on the Earth's mantle by metal-silicate equilibration would be too low. This would exclude single stage magma ocean models for producing approximately chondritic Ni/Co ratio in the Earth's mantle. However, the accuracy of the experimental data obtained here and from the literature is not sufficient to unambiguously exclude single stage equilibration. The results of this and other recent studies exclude that Fe-, Ni-, and Co-contents of the present upper mantle were established by metal-silicate equilibration at upper mantle conditions (< 25 GPa).

Kegler, Ph.; Holzheid, A.; Frost, D. J.; Rubie, D. C.; Dohmen, R.; Palme, H.

2008-04-01

204

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)

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.

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

205

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

PubMed

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

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

206

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

NASA Astrophysics Data System (ADS)

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 ä13C and ä18O values from selected species and bare ground.

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

2001-12-01

207

A methodology for estimating seasonal cycles of atmospheric CO2 resulting from terrestrial net ecosystem exchange (NEE) fluxes using the Transcom T3L2 pulse-response functions  

NASA Astrophysics Data System (ADS)

We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding seasonal cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 Level 2 (T3L2) atmospheric tracer transport model (ATM) intercomparison. The new pulse-response method is considerably faster than a full forward ATM simulation, allowing CO2 seasonal cycles to be computed in seconds, rather than the days or weeks required for a forward simulation. Further, the results provide an estimate of the range of transport uncertainty across 13 different ATMs associated with the translation of surface NEE fluxes into an atmospheric signal. We evaluate the method against the results of archived forward ATM simulations from T3L2. The latter are also used to estimate the uncertainties associated with oceanic and fossil fuel influences. We present a regional breakdown at selected monitoring sites of the contribution to the atmospheric CO2 cycle from the 11 different T3L2 land regions. A test case of the pulse-response code, forced by NEE fluxes from the Community Land Model, suggests that for many terrestrial models, discrepancies between model results and observed atmospheric CO2 cycles will be large enough to clearly transcend ATM uncertainties.

Nevison, C. D.; Baker, D. F.; Gurney, K. R.

2012-09-01

208

Evaluation of terrestrial carbon cycle models through simulations of the seasonal cycle of atmospheric CO2: First results of a model intercomparison study  

Microsoft Academic Search

Results of an intercomparison among terrestrial biogeochemical models (TBMs) are reported, in which one diagnostic and five prognostic models have been run with the same long-term climate forcing. Monthly fields of net ecosystem production (NEP), which is the difference between net primary production (NPP) and heterotrophic respiration RH, at 0.5° resolution have been generated for the terrestrial biosphere. The monthly

M. Heimann; R. D. Otto; I. C. Prentice; W. Sauf; A. Schloss; S. Sitch; U. Wittenberg; G. Würth; J. Melillo; B. Moore

1998-01-01

209

Modeling soil climate controls on the exchange of trace gases between the terrestrial biosphere and the atmosphere. Ph.D. Thesis  

SciTech Connect

Soil temperature and moisture profiles (soil climate) have a strong influence on the rate of trace gas exchange between the terrestrial biosphere and the atmosphere through the controls exerted on microbial processes and the physical exchange of gases. Principal controls of biological denitrification in mineral soils are the availability of carbon and nitrogen substrates and the soil anaerobic status. A process-oriented model of decomposition and denitrification in soils (DNDC) was modified to have a more detailed portrayal of these controls. In particular, a diffusive soil gas phase was added, along with a method for determining anaerobic and aerobic fractional volume within a soil profile. The model generally overestimated N2O fluxes when compared to field data from a sandy soil in Costa Rica, but captured the timing and shape of the brief flux episodes. Several modelling shortcomings are discussed, including the nature of the carbon substrates and the nature and dynamics of soil anaerobic fractional volume. Methane flux from wetland soils is generally correlated with soil temperature and depth to water table. A model of peat soil climate was developed and applied to a small, poor fen in southern New Hampshire. Temperature profiles and ice depth are in good agreement with field data, but depth to water table is more problematic. Field-based flux correlations to soil temperature, depth to water table, and weighted recent precipitation were developed. When used with the wetland soil climate model, much of the seasonal and shorter period flux variability was captured. The model was then driven by local weather data for 1926-1986; flux variability was dependent on both summer season temperatures and summer precipitation patterns. It is estimated that a five-year field study would capture most of the inter-annual variability.

Frolking, S.E.

1993-12-31

210

A model atmosphere analysis of the faint early-type halo star PHL 346  

NASA Astrophysics Data System (ADS)

Stellar equivalent widths and hydrogen line profiles, measured from high-resolution optical spectra obtained with the 2.5 m Issac Newton Telescope, are used in conjunction with model atmosphere calculations to determine the atmospheric parameters and chemical composition of the faint, high galactic latitude early-type star PHL 346. The effective temperature (Teff = 22,600 + or - 1000 K) and surface gravity (log g = 3.6 + or - 0.2), as well as the chemical composition, are found to be similar to those of normal OB stars. Therefore, it is concluded that PHL 346 is an ordinary Population I object, at a z distance of 8.7 + or - 1.5 kpc. The relatively small stellar velocity in the z-direction (Vz = +56 + or - 10 km/s) then implies that PHL 346 must have been formed in the halo, possibly from galactic fountain material at a z distance of about 6 kpc.

Keenan, F. P.; Lennon, D. J.; Brown, P. J. F.; Dufton, P. L.

1986-08-01

211

A Reducing Atmosphere From Out-gassing of the Early Earth  

NASA Astrophysics Data System (ADS)

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}

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

2005-08-01

212

Atmosphere  

NSDL National Science Digital Library

What is this atmosphere that surrounds the Earth? This instructional tutorial, part of an interactive laboratory series for grades 8-12, introduces students to the structure, effects, and components of the atmosphere. Here students investigate the composition of the atmosphere; effects of temperature, pressure, and ozone; the greenhouse effect; and how Earth compares with other planets. Interactive activities present students with opportunities to explore ideas and answer questions about the atmosphere, including its structure, the making of ozone, rocket launching, and measuring the atmosphere. Pop-up boxes provide additional information on topics such as dust, rain, and atmospheric composition. Students complete a final written review of six questions about the atmosphere. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

213

Escape of protoatmospheres and their role in atmosphere evolution  

NASA Astrophysics Data System (ADS)

We discuss the origin and evolution of the atmosphere of early Venus, Earth, Mars and super- Earths. It will be shown that the formation age of a terrestrial planet, its mass and size, as well as the planet's lifetime in the EUV-saturated early phase of its host star play a significant role in the escape of the planet's protoatmosphere and related atmosphere evolution.

Lammer, H.; Kislyakova, K. G.; Erkaev, N. V.; Odert, P.; Kulikov, Y. N.; Hanslmeier, A.

2012-09-01

214

Atmospheric chemistry: Natural atmospheric acidity  

NASA Astrophysics Data System (ADS)

Formic acid exerts a significant influence on atmospheric chemistry and rainwater acidity. Satellite observations and model simulations suggest that terrestrial vegetation accounts for around 90% of the formic acid produced annually.

Millet, Dylan B.

2012-01-01

215

Fragmentation of metal diapirs in terrestrial magma oceans  

NASA Astrophysics Data System (ADS)

Due to mechanisms such as impact heating, early atmospheric thermal blanketing or radioactive heating, the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable. In such a context, a key question is whether (and how much) iron diapirs provided by differentiated impactors have emulsified during their sinking towards the bottom of an early magma ocean. Addressing this problem allows one to put strong constraints on metal-silicate equilibration processes as well as heat distribution within a young terrestrial planet. Previous theoretical studies have focused on this question, however no dynamic studies have conducted a systematic exploration of the relevant parameter space corresponding to terrestrial magma oceans. We therefore perform a series of numerical experiments where we follow the sinking of iron diapirs until they fragment (or not) into smaller bodies. Metal-silicate thermal and chemical exchanges are also monitored during the sinking process. Our models include an accurate treatment of surface tension, inertial effects, as well as viscous heating and we investigate systematically the effect of rheological properties and diapir sizes on the conditions and on the consequences of metal diapir fragmentation in terrestrial magma oceans.

Samuel, H.; Rubie, D. C.; Melosh, H. J.

2010-12-01

216

The early Martian atmosphere: Investigating the role of the dust cycle in the possible maintenance of two stable climate states  

NASA Astrophysics Data System (ADS)

Leovy (personal communication, 2007) speculated that two stable climate states on early Mars could have resulted from interactions between the dust and CO2 cycles. In one state, a highly active dust cycle would prevent atmospheric collapse, and in the second, the collapsed atmosphere would not maintain an active dust cycle. An initial assessment of this idea is presented based on a Mars general circulation model parameter study. A range of global dust loadings, CO2 ice albedos, and obliquities are investigated to explore conditions in which increasing the atmospheric dust content stabilizes an otherwise unstable atmosphere. We find that dust only stabilizes the atmosphere at high obliquity and when the CO2 ice albedo is high. Although results suggest that two stable states could have existed on early Mars under limited conditions, further work is needed to know if the conditions necessary are physically plausible.

Kahre, Melinda A.; Vines, Sarah K.; Haberle, Robert M.; Hollingsworth, Jeffery L.

2013-06-01

217

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

National Technical Information Service (NTIS)

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 potentia...

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

2011-01-01

218

Evidence for elevated emissions from high-latitude wetlands contributing to high atmospheric CH4 concentration in the early Holocene  

NASA Astrophysics Data System (ADS)

The major increase in atmospheric methane (CH4) concentration during the last glacial-interglacial transition provides a useful example for understanding the interactions and feedbacks among Earth's climate, biosphere carbon cycling, and atmospheric chemistry. However, the causes of CH4 doubling during the last deglaciation are still uncertain and debated. Although the ice-core data consistently suggest a dominant contribution from northern high-latitude wetlands in the early Holocene, identifying the actual sources from the ground-based data has been elusive. Here we present data syntheses and a case study from Alaska to demonstrate the importance of northern wetlands in contributing to high atmospheric CH4 concentration in the early Holocene. Our data indicate that new peatland formation as well as peat accumulation in northern high-latitude regions increased more than threefold in the early Holocene in response to climate warming and the availability of new habitat as a result of deglaciation. Furthermore, we show that marshes and wet fens that represent early stages of wetland succession were likely more widespread in the early Holocene. These wetlands are associated with high CH4 emissions due to high primary productivity and the presence of emergent plant species that facilitate CH4 transport to the atmosphere. We argue that early wetland succession and rapid peat accumulation and expansion (not simply initiation) contributed to high CH4 emissions from northern regions, potentially contributing to the sharp rise in atmospheric CH4 at the onset of the Holocene.

Yu, Zicheng; Loisel, Julie; Turetsky, Merritt R.; Cai, Shanshan; Zhao, Yan; Frolking, Steve; MacDonald, Glen M.; Bubier, Jill L.

2013-01-01

219

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)

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.

Hadley, J. L.; Kuzeja, P.; Mulcahy, T.; Singh, S.

2008-12-01

220

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

PubMed Central

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.

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

2008-01-01

221

Evolution of ore deposits on terrestrial planets  

NASA Astrophysics Data System (ADS)

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.

Burns, R. G.

222

The lifetime of excess atmospheric carbon dioxide  

NASA Astrophysics Data System (ADS)

We explore the effects of a changing terrestrial biosphere on the atmospheric residence time of CO2 using three simple ocean carbon cycle models and a model of global terrestrial carbon cycling. We find differences in model behavior associated with the assumption of an active terrestrial biosphere (forest regrowth) and significant differences if we assume a donor-dependent flux from the atmosphere to the terrestrial component (e.g., a hypothetical terrestrial fertilization flux). To avoid numerical difficulties associated with treating the atmospheric CO2 decay (relaxation) curve as being well approximated by a weighted sum of exponential functions, we define the single half-life as the time it takes for a model atmosphere to relax from its present-day value half way to its equilibrium pCO2 value. This scenario-based approach also avoids the use of unit pulse (Dirac Delta) functions which can prove troublesome or unrealistic in the context of a terrestrial fertilization assumption. We also discuss some of the numerical problems associated with a conventional lifetime calculation which is based on an exponential model. We connect our analysis of the residence time of CO2 and the concept of single half-life to the residence time calculations which are based on using weighted sums of exponentials. We note that the single half-life concept focuses upon the early decline of CO2 under a cutoff/decay scenario. If one assumes a terrestrial biosphere with a fertilization flux, then our best estimate is that the single half-life for excess CO2 lies within the range of 19 to 49 years, with a reasonable average being 31 years. If we assume only regrowth, then the average value for the single half-life for excess CO2 increases to 72 years, and if we remove the terrestrial component completely, then it increases further to 92 years.

Moore, Berrien; Braswell, B. H.

1994-03-01

223

Terrestrial nest-building by wild chimpanzees (Pan troglodytes): implications for the tree-to-ground sleep transition in early hominins.  

PubMed

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

Koops, Kathelijne; McGrew, William C; Matsuzawa, Tetsuro; Knapp, Leslie A

2012-03-28

224

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)

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.

Kim, Y.; Kimball, J. S.; McDonald, K. C.; Glassy, J. M.

2010-12-01

225

Feldspar palaeo-isochrons from early Archaean TTGs: Pb-isotope evidence for a high U/Pb terrestrial Hadean crust  

NASA Astrophysics Data System (ADS)

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.

Kamber, B. S.; Whitehouse, M. J.; Moorbath, S.; Collerson, K. D.

2001-12-01

226

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...

227

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)

Carbon and nitrogen stable isotope ratios (?13C and ?15N) have been used widely in archaeology to investigate palaeodiet. Sulphur stable isotope ratios (?34S) 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 ?34S, ?13C and ?15N 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 ?34S 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 2?). 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 ?13C and ?15N values. For example, several terrestrial herbivores displayed enriched bone collagen ?34S 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 ?15N values coupled with light ?34S 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.

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

228

Comparing early twentieth century and present-day atmospheric pollution in SW France: A story of lichens.  

PubMed

Lichens have long been known to be good indicators of air quality and atmospheric deposition. Xanthoria parietina was selected to investigate past (sourced from a herbarium) and present-day trace metal pollution in four sites from South-West France (close to Albi). Enrichment factors, relationships between elements and hierarchical classification indicated that the atmosphere was mainly impacted by coal combustion (as shown by As, Pb or Cd contamination) during the early twentieth century, whereas more recently, another mixture of pollutants (e.g. Sb, Sn, Pb and Cu) from local factories and car traffic has emerged. The Rare Earth Elements (REE) and other lithogenic elements indicated a higher dust content in the atmosphere in the early twentieth century and a specific lithological local signature. In addition to long-range atmospheric transport, local urban emissions had a strong impact on trace element contamination registered in lichens, particularly for contemporary data. PMID:23063614

Agnan, Y; Séjalon-Delmas, N; Probst, A

2012-10-09

229

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)

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.

McDonald, K. C.; Kimball, J. S.

2006-12-01

230

Stochastic Clump Model: a clue to understanding the mixing in the early-type star atmospheres  

NASA Astrophysics Data System (ADS)

The Stochastic Clump Model (SCM) of the winds of early-type stars is proposed. In this model the formation of dense inhomogeneities (clumps) in the line driven winds is considered as being a stochastic process. It is supposed that the emission due to clumps mainly contributes to the intensities of emission lines in the stellar spectra. It is shown that in the framework of the SCM it is possible to reproduce both the mean line profiles and a common pattern of the line profile variability, and that chemical abundances in clumps and interclump medium can be different. The propagation of the clumps through the atmosphere leads to the elements mixing in the wind. The effect of the mixing is discussed.

Kholtygin, A. F.

231

Estimating Seasonal Cycles of Atmospheric CO2 and APO Resulting from Terrestrial NEE and Air-Sea O2 Fluxes using the Transcom T3L2 Pulse-Response Functions  

NASA Astrophysics Data System (ADS)

We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding annual mean cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 atmospheric tracer transport model (ATM) intercomparison. An oceanic version of the method is applied to air-sea O2 fluxes to estimate the corresponding annual mean cycles in atmospheric potential oxygen (APO). The estimated atmospheric seasonal cycles can be evaluated against observed atmospheric CO2 and APO data, which are measured at high precision at a wide range of monitoring sites and reflect the integrated impact of surface CO2 and O2 fluxes, respectively, across broad regions. The pulse-response function method is considerably faster than a full forward ATM simulation, allowing seasonal cycles from 13 different ATMS to be computed in minutes, rather than the days or weeks required for a single forward simulation. We evaluate the method against the results of full forward ATM simulations and examine the uncertainties associated with neglecting additional surface fluxes, e.g., from fossil fuel combustion, that may contribute to the observed seasonal cycles of CO2 and APO.

Nevison, C. D.

2011-12-01

232

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

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).

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

233

Terrestrial planet formation  

PubMed Central

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.

Righter, K.; O'Brien, D. P.

2011-01-01

234

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a ?-cyclodextrin capillary column coupled with thermal desorption and mass spectrometry  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A ?-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

2001-01-01

235

Trace level determination of enantiomeric monoterpenes in terrestrial plant emission and in the atmosphere using a b-cyclodextrin capillary column coupled with thermal desorption  

Microsoft Academic Search

For the first time, enrichment on solid sorbents followed by thermal desorption has been used for the determination of the enantiomeric signature of monoterpenes in the gaseous emission of terrestrial plants. A b-cyclodextrin capillary column has been used for the separation of critical pairs. The temperature program and column loading were optimized for making the accurate quantification of individual enantiomers

Noureddine Yassaa; Enzo Brancaleoni; Massimiliano Frattoni; Paolo Ciccioli

236

Terrestrial ecosystems and climatic change  

SciTech Connect

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.

Emanuel, W.R. (Oak Ridge National Lab., TN (USA)); Schimel, D.S. (Colorado State Univ., Fort Collins, CO (USA). Natural Resources Ecology Lab.)

1990-01-01

237

Phosphorus Redox on the Early Earth: First Identification of Low-Oxidation State Phosphorus Compounds in Terrestrial Samples  

NASA Astrophysics Data System (ADS)

Phosphorus is one of the key elements in biochemical systems, playing an important role in metabolism as ATP and other coenzymes, in replication as DNA and RNA, and in cellular structure as phospholipids. The geochemical cycling of phosphorus on the Earth is usually confined to the rock cycle- redox reactions of phosphorus are never considered. However, it has been proposed that redox reactions of phosphorus were important on the early Earth (Pasek, PNAS 2008). Indeed, such a suggestion is buttressed by the discovery of condensed phosphate formation linked to the oxidation of reduced P compounds. However, prior to the present work, there has been no report of these P compounds in geologic samples. Here we report the first occurrence of reduced P in samples of fulgurites, the glassy material resulting from the fusion of sand, soil, or rock during a lightning strike. On average, lightning strikes the Earth's surface at a rate of approximately 65 times per second (Krider et al., J. Geophys. Res.,1968) exposing target areas to extreme energy dissipation and temperatures. Through electron microprobe analyses and NMR we have identified naturally formed metal droplets containing Fe and P within several fulgurite samples and Ca-phosphite compounds. These droplets are highly reduced compared to the original material and are not naturally present in the target area, rather they were formed through the rapid, intense heating and quenching experienced during fulgurite formation. This process provides a natural means to create localized environments with greater than normal abundances of reduced Fe and P, less commonly found on Earth's surface than their oxidized counterparts. In particular, small areas that receive repeated lightning strikes due to topography or local weather patterns (e.g. hilltops) could potentially house unique microhabitats with reduced elements available for biological use.

Block, K. M.; Pasek, M. A.

2008-12-01

238

Pathways to Earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres.  

PubMed

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

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

239

Terrestrial multi-proxy late Miocene to early Pliocene climate reconstruction of Cook Inlet forearc basin, southern Alaska  

NASA Astrophysics Data System (ADS)

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.

Mongrain, J. R.; Wooller, M.; Fowell, S. J.; Mccarthy, P. J.; LePain, D.

2011-12-01

240

Testing 87Sr\\/ 86Sr as a paleosalinity indicator on mixed marine, brackish-water and terrestrial vertebrate skeletal apatite in late Paleocene-early Eocene near-coastal sediments, Mississippi  

Microsoft Academic Search

Mixed marine, brackish-water and terrestrial vertebrate skeletal apatite is found in the late Paleocene-early Eocene Tuscahoma and Bashi Formations of Mississippi. The co-Occurrence in these near-coastal marine deposits of skeletal apatite with different provenances offers a unique opportunity for unraveling the effects of diagenesis on apatite 87Sr\\/86Sr composition, with bearings on the use of this isotope pair as paleosalinity indicator.

Birger Schmitz; Stephen L. Ingram; David T. Dockery; Göran Åberg

1997-01-01

241

Terrestrial carbon sink in the Northern Hemisphere estimated from the atmospheric CO 2 diVerence between Mauna Loa and the South Pole since 1959  

Microsoft Academic Search

The diVerence between Mauna Loa and South Pole atmospheric CO 2 concentrations from 1959 to the present scales linearly with CO 2 emissions from fossil fuel burning and cement production (together called fossil CO 2 ). An extrapolation to zero fossil CO 2 emission has been used to suggest that the atmospheric CO 2 concentration at Mauna Loa was 0.8

SONG-MIAO FAN; TEGAN L. BLAINE; JORGE L. SARMIENTO

242

Terrestrial carbon storage during the past 200 years: A Monte Carlo Analysis of CO2 data from ice core and atmospheric measurements  

Microsoft Academic Search

We have updated earlier deconvolution analyses using most recent high-precision ice core data for the last millennium [Etheridge et al., 1996] and direct atmospheric CO2 observations starting in 1958 [Keeling and Whorf, 1994]. We interpreted nonfossil emissions, that is, the difference between the increase in observed atmospheric plus modeled oceanic carbon inventory and fossil emissions, as biospheric carbon storage (release).

Michele Bruno; Fortunat Joos

1997-01-01

243

Pluto: Global Modeling of 3-D Atmosphere-Surface Interactions  

NASA Astrophysics Data System (ADS)

Atmosphere-surface interactions on Pluto are of great importance to creating and maintaining the atmosphere variations and heterogeneous surface that have been observed in the past two decades. This work investigates these processes in a multidisciplinary fashion, using a new global climate model (GCM) for Pluto based on the terrestrial OLAM model (University of Miami). Early results from this Pluto GCM, using relatively simple configurations/initializations, will be presented. Detailed shorter-timescale interactions will be emphasized.

Michaels, Timothy I.

2013-10-01

244

Biomonitoring the environmental impact of atmospheric emissions from the Avonmouth zinc smelter, United Kingdom  

Microsoft Academic Search

This paper examines the impact of an industrial point-source atmospheric emission on the feeding of early life stages of a\\u000a terrestrial invertebrate. Larvae of a bagworm moth, Luffia ferchaultella [Stephens], were fed terrestrial epiphytic algae (Desmococcus viridis [Menegh]) collected from five sites located along a 16 km transect around the Avonmouth zinc smelter. After 10 days of exposure\\u000a symptoms of lethal and

Ian Sims; Mark Crane; Ian Johnson; Peter Credland

2009-01-01

245

Climate control of terrestrial carbon exchange across biomes and continents  

Microsoft Academic Search

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net

Chuixiang Yi; Daniel Ricciuto; Runze Li; John Wolbeck; Xiyan Xu; Mats Nilsson; Luis Aires; John D. Albertson; Christof Ammann; M. Altaf Arain; Alessandro C. de Araujo; Marc Aubinet; Mika Aurela; Zoltán Barcza; Alan Barr; Paul Berbigier; Jason Beringer; Christian Bernhofer; Andrew T. Black; Paul V. Bolstad; Fred C. Bosveld; Mark S. J. Broadmeadow; Nina Buchmann; Sean P. Burns; Pierre Cellier; Jingming Chen; Jiquan Chen; Philippe Ciais; Robert Clement; Bruce D. Cook; Peter S. Curtis; D. Bryan Dail; Ebba Dellwik; Nicolas Delpierre; Ankur R. Desai; Sabina Dore; Danilo Dragoni; Bert G. Drake; Eric Dufrêne; Allison Dunn; Jan Elbers; Werner Eugster; Matthias Falk; Christian Feigenwinter; Lawrence B. Flanagan; Thomas Foken; John Frank; Juerg Fuhrer; Damiano Gianelle; Allen Goldstein; Mike Goulden; Andre Granier; Thomas Grünwald; Lianhong Gu; Haiqiang Guo; Albin Hammerle; Shijie Han; Niall P. Hanan; László Haszpra; Bernard Heinesch; Carole Helfter; Dimmie Hendriks; Lindsay B. Hutley; Andreas Ibrom; Cor Jacobs; Torbjörn Johansson; Marjan Jongen; Gabriel Katul; Gerard Kiely; Katja Klumpp; Alexander Knohl; Thomas Kolb; Werner L. Kutsch; Peter Lafleur; Tuomas Laurila; Ray Leuning; Anders Lindroth; Heping Liu; Benjamin Loubet; Giovanni Manca; Michal Marek; Hank A. Margolis; Timothy A. Martin; William J. Massman; Roser Matamala; Giorgio Matteucci; Harry McCaughey; Lutz Merbold; Tilden Meyers; Mirco Migliavacca; Franco Miglietta; Laurent Misson; Meelis Mölder; John Moncrieff; Russell K Monson; Leonardo Montagnani; Mario Montes-Helu; Eddy Moors; Christine Moureaux; Mukufute M Mukelabai; J William Munger; May Myklebust; Zoltán Nagy; Asko Noormets; Walter Oechel; Ram Oren; Stephen G Pallardy; Kyaw Tha Paw U; João S Pereira; Kim Pilegaard; Krisztina Pintér; Casimiro Pio; Gabriel Pita; Thomas L Powell; Serge Rambal; James T Randerson; Corinna Rebmann; Janne Rinne; Federica Rossi; Nigel Roulet; Ronald J Ryel; Jorgen Sagerfors; Nobuko Saigusa; María José Sanz; Giuseppe-Scarascia Mugnozza; Hans Peter Schmid; Guenther Seufert; Mario Siqueira; Jean-François Soussana; Gregory Starr; Mark A Sutton; John Tenhunen; Juha-Pekka Tuovinen; Riccardo Valentini; Christoph S Vogel; Jingxin Wang; Shaoqiang Wang; Weiguo Wang; Lisa R Welp; Xuefa Wen; Sonia Wharton; Matthew Wilkinson; Christopher A Williams; Georg Wohlfahrt; Susumu Yamamoto; Guirui Yu; Roberto Zampedri; Bin Zhao; Xinquan Zhao

2010-01-01

246

Terrestrial carbon sink in the Northern Hemisphere estimated from the atmospheric CO2 difference between Mauna Loa and the South Pole since 1959  

Microsoft Academic Search

The diVerence between Mauna Loa and South Pole atmospheric CO2 concentrations from 1959 to the present scales linearly with CO2 emissions from fossil fuel burning and cement production (together called fossil CO2). An extrapolation to zero fossil CO2 emission has been used to suggest that the atmospheric CO2 concentration at Mauna Loa was 0.8ppm less than that at the South

Song-Miao. Fan; Tegan L. Blaine; Jorge L. Sarmiento

1999-01-01

247

Evolution of High Temperature Early Atmosphere Under the Interaction of H2O-CO2 Super-critical Fluid With Minerals  

NASA Astrophysics Data System (ADS)

The evolution of atmosphere-lithosphere system of the early Earth is controlled by mutual interaction of high temperature atmosphere with rocks and minerals. It is assumed that the total pressure of the early atmosphere and the surface temperature above initial magma ocean are 26MPa (H2O 20MPa, CO2 6MPa) and 130-330° C, respectively. This composition, temperature and pressure are very close to an azeotropic critical point of the H2O-CO2 system. Cooling of the hot H2O-CO2 atmosphere brings the first precipitation of liquid phase at above 300° C. During the early period, hot rain of the Earth should be a supercritical acid rain. Cooling rate of the hot atmosphere is regulated by energy transportation capacity among the surface, atmosphere and radiation of the early Earth. In this study, we discuss evolution of the early atmosphere-lithosphere system based on the results of the alteration experiments of minerals simulated early crust with the H2O-CO2 fluid and the cooling rate estimation of the high temperature atmosphere. The H2O-CO2 fluid easily reacts with silicate minerals at around critical point of the fluid to produce carbonate and hydrous minerals. Consumption of CO2 increases up to approximately 80% at around 250° C for olivine starting material. This means that most of Mg and Fe in the olivine starting material react with CO2. The Formation of carbonate minerals reduces the CO2 composition of fluid in the capsule to approximately one fifth. The fixation of CO2 by carbonate formation should be very effective to reduce CO2 pressure from the early atmosphere in cooling through 250° C. The first sediment of the primitive ocean should contain dolomite and hydrous silicate. The CO2 and H2O fixed in the first sediment should take an important role in the evolution of the early crust. Composition of the early atmosphere, or partial pressures of CO2 and H2O and temperature gradient of the atmosphere are essential factors controlling cooling history of the high temperature early atmosphere. We discuss evolution of the early atmosphere including effects of precipitation of super-critical H2O-CO2 fluid and atmosphere-rock interaction.

Isobe, H.; Tomita, T.; Ikeda, K.

2004-12-01

248

Geochemical and biologic constraints on the Archaean atmosphere and climate - A possible solution to the faint early Sun paradox.  

NASA Astrophysics Data System (ADS)

There is ample geological evidence that Earth's climate resembled the present during the Archaean, despite a much lower solar luminosity. This was cast as a paradox by Sagan and Mullen in 1972. Several solutions to the paradox have been suggested, mostly focusing on adjustments of the radiative properties of Earth's atmosphere e.g. Kasting (1993), by increasing the mixing ratio of CO2 and/or adding various other greenhouse gasses. We have used banded iron formation (BIF), which are chemical sediments precipitated out of the Archaean ocean to characterize the composition of the atmosphere. The stability relations of magnetite, which is ubiquitous in Archaean BIFs, preclude CO2 mixing ratios much higher than the present atmospheric level. Likewise, magnetite stability is consistent with atmospheric H2 controlled at the lower limit for H2 metabolism by methanogenic phototrophic organisms. In the absence of substantial compensation for the lower solar irradiance by greenhouse gasses in the atmosphere, we have examined the factors that controlled Earth's albedo. These are primarily the surface albedo of Earth and the abundance and properties of clouds. We have applied a model that takes into account the apparent growth of Earth continents (Collerson and Kamber 1999) and the absence of land vegetation during the Precambrian for the evolution of the surface albedo, and a model for the abundance and properties of clouds that takes into account the lower abundance of biogenic cloud condensation nuclei in a less productive prokaryotic world. The higher transparency of the atmosphere for short wave incoming solar radiation and the lower surface albedo on an early Earth dominated by oceans, provided sufficient compensation for the lower solar irradiance to allow the presence of liquid oceans, even at greenhouse gas concentrations broadly similar to the present day values. We therefore suggest that the thermostasis during Earth geologic record, is not paradoxical, but is the combined effect of many factors, which are to a large part biologically controlled. References Collerson, K. D. and B. S. Kamber (1999). "Evolution of the continents and the atmosphere inferred from Th-U-Nb systematics of the depleted mantle." Science 283(5407): 1519-1522. Kasting, J. F. (1993). "Earths Early Atmosphere." Science 259(5097): 920-926. Sagan, C. and G. Mullen (1972). "Earth and Mars - Evolution of Atmospheres and Surface Temperatures." Science 177(4043): 52-&.

Rosing, Minik T.; Bird, Dennis K.; Sleep, Norman H.; Bjerrum, Christian J.

2010-05-01

249

Atmospheric collapse and transport of carbon dioxide into the subsurface on early Mars  

Microsoft Academic Search

The present climate of Mars is extremely cold and dry, and is characterized by a very thin CO2 atmosphere. On the other hand, geological evidence suggests that the Martian climate in the past might have been warm and wet, suggesting that the atmospheric CO2 pressure would have been several bars higher. However, the fate of the abundant CO2 is still

Takasumi Kurahashi-Nakamura; Eiichi Tajika

2006-01-01

250

Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change  

Microsoft Academic Search

The relationship between atmospheric carbon dioxide (CO2) and climate in the Quaternary period has been extensively investigated, but the role of CO2 in temperature changes during the rest of Earth's history is less clear. The range of geological evidence for cool periods during the high CO2 Mesozoic `greenhouse world' of high atmospheric CO2 concentrations, indicated by models and fossil soils,

Benjamin J. Fletcher; Stuart J. Brentnall; Clive W. Anderson; Robert A. Berner; David J. Beerling

2008-01-01

251

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

National Technical Information Service (NTIS)

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 projec...

R. F. Keeling S. C. Piper

2012-01-01

252

Dependence of the upward terrestrial radiance within the (3.5 + 4.0) spectral range on thermodynamic and composition parameters of the atmosphere  

NASA Astrophysics Data System (ADS)

Calculations of the upward infrared radiance reaching outer space within the (3.5-4.0) ?m wavelength range were carried out to define the dependence features of the signals measured by radiometers onboard satellites on the temperature, moisture and composition parameters of the atmosphere. In particular, simulations of upwelling radiance were performed for application to the measurements taken by the AVHRR radiometers mounted aboard the NOAA-7 to NOAA-16 satellites and the SEVIRI instrument mounted aboard the Second Generation Meteosat (MSG-1) satellite launched in 2002. The calculations were made using a modified version of computer code LOWTRAN 7 for a large set of atmospheric vertical profiles of temperature and humidity parameters, each one represented with a set of 324 isothermal layers from sea-level to 100 km height and derived from one of 23 atmospheric models relative to different latitudes and seasons. For all these atmospheric configurations, we determined the temperature deficit ?T, as given by the difference between the surface temperature and apparent emission temperature of the surface, the latter quantity being obtained in terms of black-body emission theory from the satellite measurement of upward radiance. Parameter ?T was found to depend mainly on the total atmospheric content of water vapour and the shape of the vertical profile of temperature within the ground layer: it was found to vary considerably passing from cases of marked thermal inversions to cases of adiabatic or superadiabatic temperature gradients. Considering sets of atmospheric models where precipitable water was assumed to remain constant, ?T was found to decrease appreciably as the temperature gradient increases from negative values (in the presence of thermal inversions) to positive ones (for adiabatic and superadiabatic lapse rates at the ground), presenting negative slopes that become gradually more marked as the ground layer depth increases. Considering sets of atmospheric models where the moisture parameters were assumed to vary widely, ?T was found to change linearly as a function of precipitable water, with slope coefficients varying slowly from positive to negative values, as the temperature gradient increases from negative to positive values. As a consequence of these dependence features, the ratio between ?T and precipitable water was found to increase as a function of surface temperature, following patterns closely best-fitted by second-order polynomial curves. Dependence features of ?T on the mean atmospheric concentrations of methane and nitrous oxide were also determined. Similarly, ?T was found to vary linearly as a function of aerosol optical thickness in the visible for polydispersions of maritime, rural, urban and tropospheric aerosols, presenting the most marked slope in the case of maritime aerosols. An overall procedure is proposed for calculating ?T, taking into account i) the latitudinal and seasonal conditions of the atmosphere, ii) estimates of ground-level temperature and precipitable water, as derived from satellite and/or ground-based measurements of meteorological parameters, iii) aerosol optical thickness at visible wavelengths, and iv) CH4 and N2O atmospheric concentrations.

Tomasi, C.; Vitale, V.; Ricci, R.; Lupi, A.; Cacciari, A.

2003-03-01

253

Feasibility study for early commercialization of a modular-unit dual fluidized-bed system for converting terrestrial biomass into alternate fuels. Final report  

Microsoft Academic Search

The economic and technical feasibility for commercialization of a dual-fluidized bed system for converting terrestrial biomass into alternative fuels was investigated. The preliminary facility produced medium-Btu gas from wood chips. Another task investigated possible uses for synthesis gas as well. A detailed analysis was carried out for the generation of synthesis gas and its conversion to methanol. An analysis of

R. C. Bailie; R. J. Anderson; M. Carmack; D. E. Doner; J. A. Wagner; Naoyoshi Ando; N. W. Frank; Chikao Goke; Yoshio Hirayama; Kanichi Ito

1981-01-01

254

Early diagenetic remineralization of sedimentary organic C in the Gulf of Papua deltaic complex (Papua New Guinea): Net loss of terrestrial C and diagenetic fractionation of C isotopes  

Microsoft Academic Search

Oceania supplies ?40% of the global riverine flux of organic carbon, approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems. The Gulf of Papua, on the south coast of the large island of New Guinea, is one such deltaic clinoform complex. It receives ?4 Mt yr?1 particulate terrestrial organic carbon with initial particle

Robert C Aller; Neal E Blair

2004-01-01

255

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

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.

Xiao, X.; Kicklighter, D.W.; Melillo, J.M. [Marine Biological Laboratory, Woods Hole, MA (United States)] [and others

1995-09-01

256

Global modelling of the early martian climate under a denser CO2 atmosphere: Water cycle and ice evolution  

NASA Astrophysics Data System (ADS)

We discuss 3D global simulations of the early martian climate that we have performed assuming a faint young Sun and denser CO2 atmosphere. We include a self-consistent representation of the water cycle, with atmosphere-surface interactions, atmospheric transport, and the radiative effects of CO2 and H2O gas and clouds taken into account. We find that for atmospheric pressures greater than a fraction of a bar, the adiabatic cooling effect causes temperatures in the southern highland valley network regions to fall significantly below the global average. Long-term climate evolution simulations indicate that in these circumstances, water ice is transported to the highlands from low-lying regions for a wide range of orbital obliquities, regardless of the extent of the Tharsis bulge. In addition, an extended water ice cap forms on the southern pole, approximately corresponding to the location of the Noachian/Hesperian era Dorsa Argentea Formation. Even for a multiple-bar CO2 atmosphere, conditions are too cold to allow long-term surface liquid water. Limited melting occurs on warm summer days in some locations, but only for surface albedo and thermal inertia conditions that may be unrealistic for water ice. Nonetheless, meteorite impacts and volcanism could potentially cause intense episodic melting under such conditions. Because ice migration to higher altitudes is a robust mechanism for recharging highland water sources after such events, we suggest that this globally sub-zero, 'icy highlands' scenario for the late Noachian climate may be sufficient to explain most of the fluvial geology without the need to invoke additional long-term warming mechanisms or an early warm, wet Mars.

Wordsworth, R.; Forget, F.; Millour, E.; Head, J. W.; Madeleine, J.-B.; Charnay, B.

2013-01-01

257

Modeled responses of terrestrial ecosystems to elevated atmospheric CO 2 : a comparison of simulations by the biogeochemistry models of the Vegetation\\/Ecosystem Modeling and Analysis Project (VEMAP)  

Microsoft Academic Search

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\\u000a the context of integrated carbon, water, and nutrient cycles. Because our understanding of ecosystem responses to elevated\\u000a CO2 is incomplete, modeling is a tool that can be used

Yude Pan; Jerry M. Melillo; A. David McGuire; David W. Kicklighter; Louis F. Pitelka; Kathy Hibbard; Lars L. Pierce; Steven W. Running; Dennis S. Ojima; William J. Parton; David S. Schimel

1998-01-01

258

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

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.

Keeling, R. F.; Piper, S. C.

2008-12-23

259

Investigating the Early Atmospheres of Earth and Mars through Rivers, Raindrops, and Lava Flows  

Microsoft Academic Search

The discovery of a habitable Earth-like planet beyond our solar-system will be remembered as one of the major breakthroughs of 21st century science, and of the same magnitude as Copernicus' heliocentric model dating from the mid 16th century. The real astrobiological breakthrough will be the added results from atmospheric remote sensing of such planets to determine habitability. Atmospheres, in both

Sanjoy M. Som

2010-01-01

260

The 2007 sea ice minimum: Impacts on the Northern Hemisphere atmosphere in late autumn and early winter  

NASA Astrophysics Data System (ADS)

Over the past several decades, the minimum Northern Hemisphere summer sea ice extent has decreased substantially. We present an analysis of the influence of declining Arctic sea ice cover on the atmosphere, specifically during the autumn/early winter following an extreme summer minimum event. Using ensemble simulations from the Weather Research and Forecast model (v 3.0.1), we compare the atmospheric response for the case of the extreme sea ice minimum of 2007 to the corresponding response for the more typical ice conditions of 1984, the year with median ice extent for the 1979-2008 satellite era. Increased open water enhances heat and moisture flux from the Arctic Ocean to the atmosphere during autumn. We characterize the fluxes both horizontally and vertically and determine the spatial breadth of their influence. The atmospheric response is characterized by a strong increase in 2 m temperature and decrease in sea level pressure locally and by remote responses in the atmospheric circulation throughout the troposphere characterized by a quasi-barotropic ridge/trough signal in North America. The circulation anomalies drive remote anomalies of temperature and precipitation over eastern North America and the North Atlantic. Advectively driven temperature anomalies, in turn, cause surface flux anomalies over remote regions such as the Great Lakes and the Gulf Stream. The maximum response, as measured by difference in 2 m temperatures over the polar cap from 70°N, occurs between 10 September and approximately 15 November. The persistence of the signal over a 2 month period implies the potential for seasonal predictability of the stronger atmospheric response features. In addition, we determine the significance of prominent features, finding 95% significance in some remote features as far away as the North Atlantic.

Strey, Sara T.; Chapman, William L.; Walsh, John E.

2010-12-01

261

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)

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-Janji?), 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.

Fersch, Benjamin; Kunstmann, Harald

2013-09-01

262

Prospective Extra-Atmospheric Astronomical Investigations.  

National Technical Information Service (NTIS)

The advantages of extra-atmospheric telescopes over terrestrial telescopes are outlined. An enumeration of the requirements of extra-atmospheric telescopes is given and the significance of extra-atmospheric astronomy with respect to the future of astronom...

V. G. Kurt

1973-01-01

263

THE EARLY HISTORY OF ATMOSPHERIC OXYGEN: Homage to Robert M. Garrels  

NASA Astrophysics Data System (ADS)

This paper reviews the Precambrian history of atmospheric oxygen, beginning with a brief discussion of the possible nature and magnitude of life before the evolution of oxygenic photosynthesis. This is followed by a summary of the various lines of evidence constraining oxygen levels through time, resulting in a suggested history of atmospheric oxygen concentrations. Also reviewed are the various processes regulating oxygen concentrations, and several models of Precambrian oxygen evolution are presented. A sparse geologic record, combined with uncertainties as to its interpretation, yields only a fragmentary and imprecise reading of atmospheric oxygen evolution. Nevertheless, oxygen levels have increased through time, but not monotonically, with major and fascinating swings to both lower and higher levels.

Canfield, D. E.

2005-01-01

264

Lifetime of Excess Atmospheric Carbon Dioxide.  

National Technical Information Service (NTIS)

The authors explore the effects of a changing terrestrial biosphere on the atmospheric residence time of carbon dioxide using three simple ocean carbon cycling models and a model of global terrestrial carbon cycling. We find differences in model behavior ...

B. Moore B. H. Braswell

1994-01-01

265

Changes in terrestrial carbon storage in China induced by multiple environmental stresses  

NASA Astrophysics Data System (ADS)

China, with a land area about equal to the United States and home to 1.3 billion people, is one of the less well understood regions of the world with respect to the global carbon cycle. Much uncertainty exists in the magnitudes, spatial and temporal patterns of terrestrial carbon sources and sinks in China and the underlying mechanisms. In the past decades, China's terrestrial ecosystems have experienced a complex set of multiple environmental stresses including changes in land-cover and land use, climate, chemistry of the atmosphere and precipitation, and magnitude of disturbances. However, little is known about how these multiple environmental stresses have affected terrestrial carbon dynamics in this region. Here we have developed a partnership between Chinese and US scientists to combine remote-sensing data and a set of ecosystem simulation models to examine how ecosystem carbon storage has changed as a result of multiple stresses and interactions among those stresses including land-cover change, climate variability, atmospheric composition (carbon dioxide and tropospheric ozone), precipitation chemistry (nitrogen composition), and fire disturbance using estimates of gross primary production (GPP), net primary production (NPP) and carbon storage from factorial simulation experiments with three terrestrial ecosystem models (Biome-BGC, DLEM and TEM). Model estimates along with spatial and temporal patterns of GPP, NPP and carbon storage have been compared to satellite-derived estimates of these carbon fluxes and pools. We have also evaluated our simulated results against data from field studies and forest and soil inventories in China. Our simulated results indicate that China's terrestrial ecosystems have acted as a small carbon sink since early 1980s, which largely results from contribution of elevated N deposition, CO2 fertilization, land management and afforestation. Carbon accumulation from above factors substantially exceeds carbon release due to extreme climate events, increasing O3, deforestation and urbanization. Our study implies that the capacity of carbon sequestration by China's terrestrial ecosystems could be enhanced by managing the air and land.

Tian, H.; Melillo, J.; Running, S.; Liu, J.; Liu, M.; Kicklighter, D.; Mu, Q.; Ren, W.; Lu, C.; Chen, G.; Xu, X.; Zhang, C.; Pan, S.; Zhao, M.; Myneni, R.; Song, X.

2008-12-01

266

Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution.  

National Technical Information Service (NTIS)

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 ...

D. C. Catling

2004-01-01

267

Atmospheric Responses to Changes in Boreal Lake Distribution and to Idealized Extratropical Terrestrial Surface Forcing Propagate to the Tropics and the Southern Hemisphere  

NASA Astrophysics Data System (ADS)

We used a lake thermal physics model recently coupled into CESM1 to study the effects of lake distribution on climate. In offline simulations, high-latitude lakes decreased sensible and longwave energy fluxes to the atmosphere during the spring and summer, while all energy fluxes increased in the fall. Correcting the large under-estimation of lake area in CESM1 caused 1-2°C decreases in spring and summer daily maximum surface air temperatures and 1-2°C increases in summer and fall minimum temperatures throughout large areas of Canada and the U.S. These changes brought CESM1 diurnal temperature range predictions in Canada closer to observations. Significant remote changes were also simulated, most notably decreases in the strength of fall Southern Ocean westerlies. We investigated the effects of the summer and fall surface energy budget changes using idealized aqua-planet experiments with prescribed sea-surface temperatures (SSTs), which showed that changes as small as 2°C in the Northern Hemisphere (NH) extra-tropics could cause substantial changes in precipitation and winds in the tropics and Southern Hemisphere (SH). Shifts in the Inter-Tropical Convergence Zone (ITCZ) were opposite in sign to those predicted by previous studies, indicating that the direction of tropical responses to high-latitude cooling may depend on the character of the imposed cooling and the remote ocean response. Zonal mean circulation changes were generally consistent in sign in the coupled experiments and aqua-planet experiments. Previous studies simulating southward shifts in the ITCZ when imposing a high-latitude NH sea-surface cooling have either imposed a compensating cross-equatorial heat flux that caused increases in SH SSTs, or have allowed the NH tropical SSTs to respond directly to the high-latitude forcing (or both). In contrast, with fixed SSTs, we found that the increased mid-latitude temperature gradient reinforced the NH dominant zonal mean circulation. Increasing low-level divergence in the NH sub-tropics increased moisture flux to the NH tropics, causing a northward shift in the ITCZ. Changes in the top-of-atmosphere radiation balance reinforced these changes. We conclude that general circulation models would benefit from improved representations of lake area, particularly for the simulation of diurnal temperature range. Further research should investigate the mechanisms responsible for shifts in the ITCZ.

Subin, Z. M.; Li, F.; Murphy, L. N.; Bonfils, C.; Riley, W. J.; Lee, S.; Kang, S.; Collins, W.

2011-12-01

268

Sources of atmospheric CH{sub 4} in early postglacial time  

SciTech Connect

This paper looks the the dramatic changes in methane levels in the atmosphere following the end of the last glacial period, and during the Oldest and Younger Dryas. Levels are inferred from measurements made on ice core samples. The rate of changes required to account for the dramatic increase seems unlikely to be explainable based on biologic sources. The author argues that releases from fossil sources may have been a major contributor to the dramatic shifts recorded in the ice core records.

Nisbet, E.G. [Univ. of Saskatchewan, Saskatoon (Canada)

1992-08-20

269

Model atmosphere and kinematical analyses of early-type stars from the Edinburgh-Cape Survey  

Microsoft Academic Search

ABSTRACT We present high-resolution spectroscopic observations of 21 B-type stars, selected from the Edinburgh ?Cape Blue Object Survey. Model atmosphere,analyses confirm that 14 of these stars are young, main-sequence B-type objects with Population I chemical compositions. The remaining seven are found to be evolved objects, including subdwarfs, horizontal branch and post-AGB objects. A kinematical analysis shows that all 14 young

H. R. M. Magee; P P. L. Dufton; F. P. Keenan; W. R. J. Rolleston; D. Kilkenny; D. O'Donoghue; C. Koen; R. S. Stobie

2001-01-01

270

A Reducing Atmosphere From Out-gassing of the Early Earth  

Microsoft Academic Search

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%

L. Schaefer; B. Fegley Jr.

2005-01-01

271

Early Holocene Change in Atmospheric Circulation in the North-Central USA  

NASA Astrophysics Data System (ADS)

Numerous proxies in cores from Elk Lake, northwestern Minnesota, have provided a record of climatic and environmental change with annual resolution for the last 10,000 years. The proxies that allow reconstruction of the lake's physical and chemical paleolimnology (diatoms, redox-sensitive trace metals, and 18O values) show that that prior to about 8.2 cal ka the lake was a stable, dimictic lake that was strongly stratified. The same proxies show that after 8.2 cal. ka the lake was turbulent, well-mixed and shallower. The proxies that are related to climate factors external to the lake (dust as % Al and % Si, varve thickness, and pollen) show that prior to 8.2 cal. ka the lake was receiving relatively little dust, implying little wind activity. After 8.2 cal ka, there was a marked increase in the influx of dust indicating an increase in westerly winds. Lastly, the ostracode faunal assemblages, which provide information about the limnology and watershed characteristics, indicate that, for 1000 years prior to 8.2 cal. ka, the lake was stable and dilute with characteristics typical of lakes in boreal forests. At 8.2 cal. ka, the ostracode assemblage abruptly shifted to an assemblage typical of Canadian prairie lakes that exhibit large seasonal variability in physical characteristics. This marks the northward displacement of the polar front and beginning of westerlies. The Elk Lake record further shows that the so-called 8.2 cal. yr cold event, recognized in ice-core and other records from the circum-North Atlantic, and thought by some to be caused by catastrophic drainage of freshwater from proglacial lakes Agassiz and Ojibway, was but a brief manifestation of a more fundamental and lasting change in the climate of North America. This fundamental climate change was the result of changes in atmospheric circulation in response to marked changes in the relative proportions of land, water, and, especially, glacial ice in North America during the early Holocene, the beginning of the altithermal or prairie period in Minnesota. Substantial changes in salinity also occurred at many lacustrine sites in the Northern Great Plains around 8.2 cal. ka so that such changes are not unique to Elk Lake, and thus the driver of these changes must be regional or global in extent. Bear Lake, Utah and Idaho, is a mesosaline-alkaline lake that historically was bipassed by the Bear River to the east of the lake. However, during the last glacial interval the lake and river were connected until about 16 cal. ka. As the salinity of the lake increased without Bear River influx, carbonate began to precipitate, first as calcite and then as aragonite, the dominant carbonate mineral deposited during most of the Holocene. C- O- and Sr-isotope data indicate that at about 9.5 cal ka the lake abruptly freshened suggesting that Bear River was again reconnected to the lake. The cause of the reconnection of Bear River with Bear Lake may have been tectonic, geomorphic, or climatic. However, the dominance of a boreal ostracode assemblage prior to 8.2 cal ka in Elk Lake, indicating that the polar front was far south of its present position, may have permitted the temporary establishment of a polar low over Utah, Idaho, and Wyoming in winter, increasing the snow pack in the Uinta Mountains and the Bear River Range to the west of the lake thereby increasing the surface- and ground-water flow to the lake. By 8.5 cal ka the salinity of the lake had decreased sufficiently to trigger another pulse of calcite precipitation that lasted about 1000 years. At 8.2 cal ka, when the Elk Lake ostracode record indicates that the polar front had retreated to the north, the Bear River was disconnected from the lake, and by 7.5 cal ka aragonite was again forming.

Dean, W. E.

2005-12-01

272

Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction  

PubMed Central

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.

Chin, Karen; Pearson, Dean; Ekdale, A. A.

2013-01-01

273

Formation of the terrestrial planets  

NASA Astrophysics Data System (ADS)

The early phases of formation in the inner solar system were dominated by collisions and short-range dynamical interactions among planetesimals. But the later phases, which account for most of the differences among planets, are unsure because the dynamics are more subtle. Jupiter's influence became more important, leading to drastic clearing out of the asteroid belt and the stunting of Mars's growth. Further in, the effect of Jupiter-- both directly and indirectly, through ejection of mass in the outer solar system-- was probably to speed up the process without greatly affecting the outcome. The great variety in bulk properties of the terrestrial bodies indicate a terminal phase of great collisions, so that the outcome is the result of small-N statistics. Mercury, 65 percent iron, appears to be a residual core from a high-velocity collision. All planets appear to require a late phase of high energy impacts to erode their atmospheres: including the Earth, to remove CO2 so that its ocean could form by condensation of water. Consistent with this model is that the largest collision, about 0.2 Earth masses, was into the proto-Earth, although the only property that appears to require it is the great lack of iron in the Moon. The other large differences between the Earth and Venus, angular momentum (spin plus satellite) and inert gas abundances, must arise from origin circumstances, but neither require nor forbid the giant impact. Venus's higher ratio of light to heavy inert gases argues for it receiving a large icy impactor, about 10-6 Earth masses from far out, requiring some improbable dynamics to get a low enough approach velocity. Core formation in both planets probably started rather early during accretion. Some geochemical evidences argue for the Moon coming from the Earth's mantle, but are inconclusive. Large scale melting of the mantle by the giant impact would plausibly have led to stratification. But the "lock-up" at the end of turbulent mantle convection is a trade-off between rates: crystallization of constituents of small density difference versus overall freezing. Also, factors such as differences in melting temperatures and densities, melt compressibilities, and phase transitions may have had homogenizing effects in the subsequent mantle convection.

Kaula, William M.

1994-01-01

274

Impact of geoengineering schemes on the terrestrial biosphere  

Microsoft Academic Search

Climate stabilization via “Geoengineering” schemes seek to mitigate climate change due to increased greenhouse gases by compensating reduction in solar radiation incident on earth's surface. In this paper, we address the impact of these climate stabilization schemes on terrestrial biosphere using equilibrium simulations from a coupled atmosphere-terrestrial biosphere model. Climate stabilization would tend to limit changes in vegetation distribution brought

B. Govindasamy; S. Thompson; P. B. Duffy; K. Caldeira; C. Delire

2002-01-01

275

Impact of geoengineering schemes on the terrestrial biosphere  

Microsoft Academic Search

Climate stabilization via ``Geoengineering'' schemes seek to mitigate climate change due to increased greenhouse gases by compensating reduction in solar radiation incident on earth's surface. In this paper, we address the impact of these climate stabilization schemes on terrestrial biosphere using equilibrium simulations from a coupled atmosphere-terrestrial biosphere model. Climate stabilization would tend to limit changes in vegetation distribution brought

B. Govindasamy; S. Thompson; P. B. Duffy; K. Caldeira; C. Delire

2002-01-01

276

Interannual variation of carbon exchange fluxes in terrestrial ecosystems  

Microsoft Academic Search

A global prognostic physiologically based model of the carbon budget in terrestrial ecosystems, the Frankfurt Biosphere Model (FBM), is applied to simulate the interannual variation of carbon exchange fluxes between the atmosphere and the terrestrial biosphere. The data on climatic forcing are based on Cramer and Leemans climate maps; the interannual variation is introduced according to records of temperature anomalies

Jürgen Kindermann; Gudrun Würth; Gundolf H. Kohlmaier; Franz-W. Badeck

1996-01-01

277

Terrestrial Carbon Cycle Feedback to Climate Warming: Experimental Evidence  

Microsoft Academic Search

Global climate modeling has demonstrated that climate warming would stimulate respiratory CO2 release from the terrestrial ecosystems to the atmosphere, which in turn leads to more warming in the climate system. This positive feedback between the climate change and the terrestrial carbon cycle can form a vicious cycle that potentially leads to a dangerous threat to ecosystem functioning and service.

Y. Luo; X. Zhou; R. Sherry

2006-01-01

278

The Emergence of Terrestrial Hydrometeorology  

NASA Astrophysics Data System (ADS)

In the Encyclopaedia of Atmospheric Sciences and Astrogeology Langbein (1967) defined hydroclimatology as "the study of the influence of climate upon the waters of the land", and hydrometeorology is study of short term processes and phenomena within this climatology. But this definition is now outdated because it implies too passive a role for land surface influences on the overlying atmosphere. Over the subsequent decades research has demonstrated that proper understanding of land surface hydrology requires investigations of the hydrometeorological processes that couple terrestrial surfaces and the atmosphere. These investigations include the development and calibration of land surface models; mesoscale field experiments, that considered heterogeneity in land surface cover and investigated their aggregate representation; studies of how coupling processes relate to the concept of potential evaporation, and how estimates of irrigated crop water requirement can be updated; application of remotely sensed data and the simplifying benefits of in-plant linkages between water vapor and carbon exchange mechanisms; and the potential benefits of now-feasible area-average soil moisture measurement. This lecture reviews such investigations in the area of terrestrial hydrometeorology with some emphasis on those that have involved the speaker's participation, and argues for the creation for a new branch of scientific education focused on the subject area that lies at the interface between hydrology and meteorology.

Shuttleworth, W. J.

2011-12-01

279

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)

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.

Appiotti, F.; Krzelj, M.; Marincioni, F.; Russo, A.

2012-04-01

280

Evolution of Ore Deposits on Terrestrial Planets (Abstract Only).  

National Technical Information Service (NTIS)

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. Co...

R. G. Burns

1991-01-01

281

Late Archean to Early Paleoproterozoic global tectonics, environmental change and the rise of atmospheric oxygen  

Microsoft Academic Search

Analysis of the tectonostratigraphic records of Late Archean to Early Paleoproterozoic terranes indicates linkage between global tectonics, changing sea levels and environmental conditions. A Late Archean tectonic cycle started at ?2.78 Ga involving the breakup of a pre-existing continent (Vaalbara) and the most prodigious period of generation and preservation of juvenile continental crust recorded in Earth history during a period

Mark E. Barley; Andrey Bekker; Bryan Krapez

2005-01-01

282

Terrestrial Planet Finder: technology development plans  

Microsoft Academic Search

One of humanity's oldest questions is whether life exists elsewhere in the universe. The Terrestrial Planet Finder (TPF) mission will survey stars in our stellar neighborhood to search for planets and perform spectroscopic measurements to identify potential biomarkers in their atmospheres. In response to the recently published President's Plan for Space Exploration, TPF has plans to launch a visible-light coronagraph

Christian A. Lindensmith

2004-01-01

283

Terrestrial Planet Finder: Technology Development Plans  

Microsoft Academic Search

One of humanity's oldest questions is whether life exists elsewhere in the universe. The Terrestrial Planet Finder (TPF) mission will survey stars in our stellar neighborhood to search for planets and perform spectroscopic measurements to identify potential biomarkers in their atmospheres. In response to the recently published President's Plan for Space Exploration, TPF has plans to launch a visible-light coronagraph

Chris Lindensmith

284

ADEOS-II/GLI ocean-color atmospheric correction: early phase result  

NASA Astrophysics Data System (ADS)

The paper presents initial results of atmospherically corrected ocean color data from the Global Imager (GLI), a moderate resolution spectrometer launched in December 2002 aboard ADEOS-II satellite. The standard GLI atmospheric correction algorithm, which includes an iterative procedure based on in-water optical modeling is first described, followed by brief description of standard in-water algorithms for output geophysical parameters. Ship/buoy-observed and satellite-derived marine reflectances, or normalized water-leaving radiance, are then compared, under vicarious calibration correction factors based on global GLI-SeaWiFS data comparison. The results, over 15 water-leaving radiance match-up data collected mostly off California and off Baja California, show standard errors in GLI estimate of 0.1 to 0.36 ?W/cm2/nm/sr for 412, 443, 490, and 565 nm bands, with improved standard errors of 0.09 to 0.14 ?W/cm2/nm/sr if in situ data set is limited to those obtained by in-water radiance measurement. Under provisional de-striping procedure, satellite-derived chlorophyll a estimates compares well with 35 ship-measured data collected off California within one day difference from the satellite observation, showing standard error factor of 1.73 (+73% or 43% error).

Fukushima, Hajime; Toratani, Mitsuhiro; Tanaka, Akihiko; Chen, Wen-Zhong; Murakami, Hiroshi; Frouin, Robert J.; Mitchell, B. G.; Kahru, Mati

2003-11-01

285

Identification of nitrogenous organic species in Titan aerosols analogs: Nitrogen fixation routes in early atmospheres  

NASA Astrophysics Data System (ADS)

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.

He, Chao; Smith, Mark A.

2013-09-01

286

Terrestrial Planet Geophysics  

NASA Astrophysics Data System (ADS)

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.

Phillips, R. J.

2008-12-01

287

Experimental Inhibition of Carbonate Mineral Precipitation by Sulfur Dioxide: Implications for Early Mars  

Microsoft Academic Search

Sulfur dioxide (SO2) is abundant in terrestrial volcanic emissions and was likely at least as abundant in early martian emissions. Recent photochemical studies indicate that during episodes of vigorous volcanic activity, the atmospheric lifetime of SO2 may have been sufficiently long for it to have helped maintain liquid water on the surface of Mars and perhaps to have regulated the

I. Halevy; D. P. Schrag

2009-01-01

288

The Boreal Ecosystem-Atmosphere Study (BOREAS): An Overview and Early Results from the 1994 Field Year.  

NASA Astrophysics Data System (ADS)

The Boreal Ecosystem Atmosphere Study (BOREAS) is large-scale international field experiment that has the goal of improving our understanding of the exchanges of radiative energy, heat water, CO2, and trace gases between the boreal forest and the lower atmosphere. An important objective of BORES is collect the data needed to improve computer simulation models of the processes controlling these exchanges so that scientists can anticipate the effects of global change.From August 1993 through September 1994, a continuous set of monitoring measurements-meteorology, hydrology, and satellite remote sensing-were gathered over the 1000 × 1000 km BOREAS study region that covers most of Saskatchewan and Manitoba, Canada. This monitoring program was punctuated by six campaigns that saw the deployment of some 300 scientists and aircrew into the field, supported by 11 research aircraft. The participants were drawn primarily from U.S. and Canadian agencies and universities, although there were also important contributions from France, the United Kingdom, and Russia. The field campaigns lasted for a total of 123 days and saw the compilation of a comprehensive surface-atmosphere flux dataset supported by ecological, trace gas, hydrological, and dataset sensing science observations. The surface-atmosphere fluxes of sensible heat, latent heat, CO2, and momentum were measured using eddy correlation equipment mounted on a surface network of 10 towers complemented by four flux-measurement aircraft. All in all, over 350 airborne missions (remote sensing and eddy correlation) were flown during the 1994 field year.Preliminary analyses of the data indicate that the area-averaged photosynthetic capacity of the boreal forest is much less than that of the temperate forests to the south. This is reflected in very low photosynthetic and carbon drawdown rates, which in turn are associated with low transpiration rates (less than 2 mm day1 over the growing season for the coniferous species in the area). The strong sensible fluxes generated as a result of this often lead to the development of a deep dry planetary boundary layer over the forest, particularly during the spring and early summer. The effects of frozen soils and the strong physiological control of evapotranspiration in the biome do not seem to be well represented in most operational general circulation models of the atmosphere.Analyses of the data will continue through 1995 and 1996. Some limited revisits to the field are anticipated.

Sellers, Piers; Hall, Forrest; Ranson, K. Jon; Margolis, Hank; Kelly, Bob; Baldocchi, Dennis; den Hartog, Gerry; Cihlar, Josef; Ryan, Michael G.; Goodison, Barry; Crill, Patrick; Lettenmaier, Dennis; Wickland, Diane E.

1995-09-01

289

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

Microsoft Academic Search

During the Mesozoic (250–64Ma) intervals of about 0.5Myr 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 ~182Ma is characterized

Stephen P. Hesselbo; Grzegorz Pienkowski

2011-01-01

290

Links between tectonics, the atmosphere and life in the Archean to early Paleoproterozoic  

NASA Astrophysics Data System (ADS)

Earth is the only planet in our Solar System with a bimodal topographic distribution, crucial for the evolution of complex life. The oldest preserved evidence of volcanic islands and land surface islands from 4.0 to 3.35 Ga is very limited. The tectonic records of the Archean to Paleoproterozoic (4.0 to 2.3 Ga) terranes indicates a link between evolving global tectonics with the formation of stable continents, increased subaerial volcanism and increased orogenic mountain building and the rise of atmospheric oxygen on Earth ~2.4 billion years ago. The first 2 stable cratons formed between 3.0 and 2.9 Ga after the first unambiguous evidence for plate tectonics. The Neoarchean record started at 2.8 Ga involving the possible break of a single pre-existing continent and the most prodigious period of generation and preservation of juvenile continental crust during a period of mantle plume breakout (2.72 to 2.65 Ga). During this period of high sea levels many cratons formed and aggregated into larger cratons and continents. Lower sea levels between 2.65 and 2.55 Ga were followed by a second (~2.51 to 2.45 Ga) period of plume breakout. This resulted in a peak in magmatism and was associated with evidence for orogenic belts (mountain belts) in cratons in South Australia, Antarctica, India, China and North America between 2.5 and 2.3 Ga. Continued aggregation of continental fragments during this period may have resulted in Earth's first supercontinent and a return to low sea levels and relative tectonic quiescence. Although oxygenic photosynthetic bacteria are thought to have evolved by 2.7 Ga or 2.5 Ga, the irreversible rise of atmospheric oxygen appears to have occurred between 2.45 and 2.32 Ga suggesting a dynamic linkage and both sources and sinks of oxygen. This suggests that both and increase in the oxidation state of volcanic gasses (due to increased subaerial volcanism) during this event coupled with an increase in weathering of exposed continental crust due to the formation of mountain belts helped the rise of atmospheric oxygen leading to the Great Oxidation Event a key event to help Earth's complex life evolve.

Barley, M. E.

2011-12-01

291

Atmospheric Processes  

Microsoft Academic Search

\\u000a Atmosphere is the most dynamic part of the terrestrial environment. It is driven by the energy received from the sun. Almost\\u000a all weather phenomena mentioned in Chapter 2 result from the differences in the amount of solar energy received and utilization\\u000a thereof. It is, therefore, necessary to understand as to how the energy from the sun is converted into heat

Pukh Raj Rakhecha; Vijay P. Singh

292

Atmospheric CO2 from the late Oligocene to early Miocene reconstructed from photosynthesis data and leaf characteristics of fossil plants  

NASA Astrophysics Data System (ADS)

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.

Grein, Michaela; Oehm, Christoph; Konrad, Wilfried; Utescher, Torsten; Kunzmann, Lutz; Roth-Nebelsick, Anita

2013-04-01

293

North American Carbon Program (NACP) Regional Interim Synthesis: Terrestrial Biospheric Model Intercomparision  

Microsoft Academic Search

Understanding of carbon exchange between terrestrial ecosystems and the atmosphere can be improved through direct observations and experiments, as well as through modeling activities. Terrestrial biosphere models (TBMs) have become an integral tool for extrapolating local observations and understanding to much larger terrestrial regions. Although models vary in their specific goals and approaches, their central role within carbon cycle science

Deborah Huntzinger; Wilfred M Post; Anna Michalak; Tristram O. West; Andrew Jacobson; Ian Baker; Jing M. Chen; Kenneth Davis; Forrest M Hoffman; Atul Jain; Shuguang Liu; David Mcguire; Ronald Neilson; Ben Poulter; Hanqin Tian; Peter E Thornton; Enrico Tomelleri; Nicolas Viovy; Jingfeng Xiao; Robert B Cook

2012-01-01

294

North American Carbon Project (NACP) Regional Interim Synthesis: Terrestrial Biospheric Model Intercomparison  

Microsoft Academic Search

Understanding of carbon exchange between terrestrial ecosystems and the atmosphere can be improved through direct observations and experiments, as well as through modeling activities. Terrestrial biosphere models (TBMs) have become an integral tool for extrapolating local observations and understanding to much larger terrestrial regions. Although models vary in their specific goals and approaches, their central role within carbon cycle science

Deborah Huntzinger; W. M. Post; Yaxing Wei; A. M. Michalak; Tristram O. West; Andy Jacobson; Ian Baker; Jing Ming Chen; K. J. Davis; D. J. Hayes; F. M. Hoffman; Atul K. Jain; S. Liu; A. David McGuire; R. P. Neilson; Christopher Potter; Benjamin Poulter; David Price; B. M. Raczka; Hanqin Tian; P. Thornton; E. Tomelleri; N. Viovy; J. Xiao; Wenping Yuan; Ning Zeng; M. Zhao; R. B. Cook

2012-01-01

295

Atmospheric escape, redox evolution, and planetary habitability  

NASA Astrophysics Data System (ADS)

Through the greenhouse effect, the presence and composition of an atmosphere is critical for defining a (conventional) circumstellar habitable zone in terms of planetary surface temperatures suitable for liquid water. Lack of knowledge of planetary atmospheres is likely to frustrate attempts to say with any certainty whether detected terrestrial-sized exoplanets may or may not be habitable. Perhaps an underappreciated role in such considerations is the evolutionary effect of atmospheric escape for determining atmospheric composition or whether an atmosphere exists in the first place. Whether atmospheres exist at all on planets is demonstrably connected to the effect of integrated atmospheric escape. When we observe our own Solar System and transiting exoplanets, the existence of an atmosphere is clearly delineated by a relative vulnerability to thermal escape and impact erosion. The prevalence of thermal escape as a key evolutionary determinant for the presence of planetary atmosphere is shown by a relationship between the relative solar (or stellar) heating and the escape velocity. Those bodies with too much stellar heating and too smaller escape velocity end up devoid of atmospheres. Impact erosion is evident in the relationship between impact velocity and escape velocity. Escape due to impacts is particularly important for understanding the large differences in the atmospheres of giant planet moons, such as Ganymede versus Titan. It is also significant for Mars-sized planets. The oxidation state of atmospheres is important for some theories of the origin of life (where an early reducing atmosphere is helpful for organic synthesis) and the evolution of advanced life (where free molecular oxygen is the best source of high energy metabolism). Surfaces on some relatively small planets and moons are observed to have evolved to an oxidized state, which theory and observation can explain through atmospheric escape. There are several examples in the Solar System where a net escape of hydrogen relative to heavier oxygen is the generally accepted explanation for the present oxidation state: Venus and Mars amongst the planets, and Ganymede, Europa, and Rhea amongst bodies with extremely tenuous atmospheres. We also argue that hydrogen escape was the key factor for oxidizing the Earth and facilitating the increase of photosynthetically-produced oxygen in the Proterozoic atmosphere. Our view about the primacy of hydrogen escape with regard to the Earth's atmospheric oxygenation is perhaps less widely accepted. However, it was inevitable that hydrogen escaped from Earth's early anoxic atmosphere at a significant rate. The result was a very big integrated oxidation consistent with what is observed in the Earth's crust in addition to some export to the mantle. In conclusion, a better understanding of atmospheric escape processes appears critical for understanding the suitability of planets for harboring life from simple to advanced forms.

Catling, D. C.; Zahnle, K. J.

2011-12-01

296

Early plume expansion in atmospheric pressure midinfrared laser ablation of water-rich targets  

NASA Astrophysics Data System (ADS)

We have developed a one-dimensional fluid dynamics model for the ablation of water-rich targets by nanosecond infrared laser pulses at atmospheric pressure. To describe the laser-target interaction and the plume expansion dynamics, in light of recent experimental results the model incorporates phase explosion due to superheating and the nonlinear light absorption properties of water. In the model, the phase explosion is treated as a prolonged process that lasts for a finite time. Once a thin layer beneath the target surface exceeds the phase explosion temperature, this layer is transformed from target material into a mixture of water vapor and droplets and become part of the plume. This process is sustained for some time until the laser energy cannot maintain it. The simulation results show that as a result of two different phase transition mechanisms, i.e., surface evaporation and phase explosion, a first, slower plume expansion phase is followed by a more vigorous accelerated expansion phase. The calculated time evolution of the shock front at various fluence levels agrees well with the experimental observations of Apitz and Vogel [I. Apitz and A. Vogel, Appl. Phys. A. 81, 329 (2005)]. This model sheds light on the effect of phase explosion in laser ablation dynamics and its results are relevant for material synthesis, surface analysis, and medical (surgery) applications.

Chen, Zhaoyang; Vertes, Akos

2008-03-01

297

The Compositional Diversity of Extrasolar Terrestrial Planets  

NASA Astrophysics Data System (ADS)

The details of the formation of the terrestrial planets are long-standing questions in the geological, planetary and astronomical sciences, with the discovery of extrasolar planetary systems placing even greater emphasis on these questions. Here we present simulations of the bulk compositions of simulated terrestrial planets in extrasolar planetary systems. These simulations incorporate both giant planet migration into the dynamical simulations and a variety of ices, clathrates and hydrates into the chemical modeling, providing us with a more inclusive view of extrasolar terrestrial planet formation. We find that a diverse range of extrasolar terrestrial planets are produced, ranging from bulk elemental compositions similar to that of Earth to those that are enriched in elements such as C and Si, producing planets with compositions unlike anything we have previously observed. Giant planet migration significantly alters the composition of the final terrestrial planet by redistributing material throughout the system. Simulated terrestrial planets produced within the migration simulations are found to contain larger amounts of Mg-silicate species and hydrous material. These variations in composition will greatly influence planetary processes such as plate tectonics, planetary interior structure and the primary atmospheric composition.

Carter-Bond, J. C.; O'Brien, D. P.

2011-12-01

298

Observation of Terrestrial Gamma-ray Flashes with Fermi LAT  

NASA Astrophysics Data System (ADS)

Terrestrial Gamma-Ray Flashes (TGFs) are millisecond bursts of high energy photons, electrons, and positrons originating in Earth's atmosphere and associated with powerful thunderstorms. The Fermi GBM has detected hundreds of TGFs, some with energies up to 40 MeV. Recent AGILE observations of photons up to 100 MeV in TGFs pose a significant challenge to the relativistic runaway electron avalanche mechanism that is generally believed to be responsible for these bremsstrahlung gamma rays. With its large area, high segmentation, and low deadtime, the Fermi Large Area Telescope (LAT) is a powerful instrument for measuring the high energy emission of these short, intense transients. Here we present early results of a program of observing TGFs with the LAT.

Grove, J. Eric; Chekhtman, A.; Fermi LAT Collaboration; Fishman, G.; Briggs, M.; Connaughton, V.; Fermi GBM Collaboration

2012-01-01

299

Expansion of Voltage-dependent Na+ Channel Gene Family in Early Tetrapods Coincided with the Emergence of Terrestriality and Increased Brain Complexity  

PubMed Central

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.

Zakon, Harold H.; Jost, Manda C.; Lu, Ying

2011-01-01

300

Abiotic Nitrogen Fixation on Terrestrial Planets  

NASA Astrophysics Data System (ADS)

The abiotic fixation of nitrogen is critical to planetary evolution and the potential for life on terrestrial planets. A non-biological source of nitrogen, in a biochemically accessible form, is necessary for the origin and early evolution of life. Loss of nitrogen can result in atmospheric pressures too low for liquid water and will impact planetary habitability and hydrological processes. Shock heating of a non-reducing atmosphere produces NO and this has been well studied. Our understanding of the subsequent reactions was, in the past, theoretical. It was postulated that NO was photochemically converted to HNO which then, in surface waters, reacts to form nitrate and nitrite. This chemistry, including reactions in both the gas phase and the liquid phase, has now been studied experimentally. Our work has observed that there are multiple pathways for the fixation. One pathway observed is consistent with the theoretically predicted route via the formation of HNO. Interestingly, this pathway is coupled to photochemical formation of formaldehyde from CO through the formation of HCO. In the presence of liquid water, this pathway leads to the formation of nitrate and nitrite. In the presence of water vapor, but no liquid water, HNO appears to mostly dimerize to form N2O. A second pathway involves the formation of NO2 from CO2 and NO. This pathway becomes more dominant without water, but the reaction of NO2 with even adsorbed water can lead to the formation of nitric acid. Finally, with FeS suspended in liquid water, the direct reduction of NO to ammonia is observed. This last pathway represents the most efficient way to reduced nitrogen, with product yields well above 20% (nitrite/nitrate, from the first two pathways can also be reduced to ammonia thought the overall efficiency suffers). We wish to thank the NASA Astrobiology Institute for support.

Summers, David P.; Khare, B.; Basa, R. C. B.; Rodoni, D.

2009-09-01

301

Terrestrial Ages of Meteorites  

NASA Astrophysics Data System (ADS)

The terrestrial age, or the terrestrial residence time of a meteorite, together with its exposure history provides us with useful insight into the history of the meteorite. It is easy to observe that stony meteorites can weather quickly in humid environments. However, we find that large numbers of meteorites found in semiarid and arid environments can survive for much longer times. Meteorites in desert environments can survive for at least 50,000 yr, and there are some meteorites over 250,000 yr old from these locations. The cold and dry conditions of polar regions such as Antarctica are also good for the storage of meteorites. A considerable number of meteorites survive there for hundreds of thousands of years. Some meteorites have been found in Antarctica with ages of up to 2 m.y. In this paper, we discuss the terrestrial residence times or terrestrial ages of these meteorites. We will show the wide range of terrestrial ages from different environments.

Jull, A. J. T.

302

Transpiration and Assimilation of Early Devonian Land Plants with Axially Symmetric Telomes—Simulations on the Tissue Level  

Microsoft Academic Search

Early terrestrial ancestors of the land flora are characterized by a simple, axially symmetric habit and evolved in an atmosphere with much higher CO2concentrations than today. In order to gain information about the ecophysiological interrelationships of these plants, a model dealing with their gaseous exchange, which is basic to transpiration and photosynthesis, is introduced. The model is based on gas

W. KONRAD; A. R OTH-NEBELSICK; H KERP; H. HASS

2000-01-01

303

High-resolution correlation of the late Triassic (Raetian) to the early Jurassic (Toarcian) between Pelagic sequence of Panthalassa and terrestrial sequence of Pangea using Milankovitch cycles  

NASA Astrophysics Data System (ADS)

Milankovitch forcing is one of the main drivers of cyclic climate changes, and cyclicities of Milankovitch cycles recorded in sedimentary rhythms would give a clue to establish the astronomically calibrated age model. Bedded cherts consist of rhythmical alternations of a chert bed and a shale bed, which are considered to have been formed as a result of cyclic changes in accumulation rate of biogenic SiO2 under extremely slow and continuous accumulation of pelagic clay. Although Milankovitch cycle origin of bedded chert was suggested by several arthors (e.g. Hori et al., 1993), such an origin has been still unproved. Ikeda et al. (2008) demonstrated the Milankovitch cycle origin of the middle Triassic bedded chert based on the similarities in the hierarchy of dominant cyclicities and the nature of amplitude modulation between Milankovitch cycles and the chert bed thickness cycles. However, because the errors of age determinations in the middle Triassic bedded chert are too large, we could not orbitally tune the bedded chert sequence to the astronomical time scale. In this study, we extend our research to the upper Triassic (Raetian) to lower Jurassic (Toarcian) bedded chert sequence and demonstrate its Milankovitch cycle origin. The Triassic/Jurassic (T/J) boundary was recognized as a radiolarian faunal turnover (Carter & Hori, 2005). Because the astronomically calibrated cyclostratigraphy was already established using the upper Triassic (Carnian) to lower Jurassic (Hettangian) lacustrine sequences of Pangea including the T/J boundary horizon (e.g. Olsen & Kent, 1999; Whiteside et al., 2007), we could compare our bedded chert sequence with them. We conducted geologic survey at Katsuyama section (e.g. Carter & Hori, 2005), in Inuyama area, central Japan. The average duration of ca. 20 ky for a chert-shale couplet based on radiolarian biostratigraphy is consistent with the assumption that a chert-shale couplet represents a precession cycle. Spectral analysis of bed number series of chert bed thickness revealed ca. 5, 20, and 200beds cycles that correspond to ca. 100, 400, and ca. 3500 ky eccentricity cycles, respectively. The similarity in the hierarchy of dominant periodicities between Milankovitch cycles and chert bed thickness cycles strongly support the idea that the cyclicities in thickness of a chert bed of upper Triassic to lower Jurassic bedded chert sequence were paced by Milankovitch cycles. We try to import the astronomically calibrated cyclostratigraphy for the lacustrine sequence in Newark basin (Olsen & Kent, 1999; Whiteside et al., 2007) into the bedded chert sequence in Inuyama by using the T/J boundary as a datum level. This correlation suggests that the radiolarian faunal turnover in Panthalassa is almost synchronous (~ ca. 100 ky) with the faunal and floral turnover in Pangea. Such a cyclostratigraphic correlation between pelagic bedded chert sequence and terrestrial lacustrine sequence will also provide useful information on the detailed process and mechanism of environmental changes at the T/J boundary and its relation with mass extinction.

Ikeda, M.; Tada, R.; Sakuma, H.

2009-12-01

304

Where did Terrestrial Life Begin?  

Microsoft Academic Search

IN reference to Mr. Dines's letter in NATURE of February 16, if the diurnal variations in temperature and humidity on a mountain summit in the early earth would have been smaller than at sea-level, my objection to Dr. Macfie's theory would certainly not hold. But Mr. Dines remarks that, assuming some stratification of the atmosphere, the stirring up of the

J. W. Gregory

1922-01-01

305

Where did Terrestrial Life Begin?  

Microsoft Academic Search

DR. MACFIE'S suggestion that life originated on the mountain summits is new, and entitled to careful consideration. If the early earth, when its atmosphere was laden with carbon dioxide and steam, had been windless, then the mountain summits would have stood like islands above a sea of hot mist, and they would have been the only situations possible for the

J. W. Gregory

1922-01-01

306

Carbon dioxide exchange and early old-field succession  

Microsoft Academic Search

Old-field succession is a widespread process active in shaping landscapes in the eastern United States, contributing significantly to the terrestrial sink of atmospheric carbon dioxide, particularly at midlatitudes. However, few studies document ecosystem-scale carbon dioxide exchange during the early years of old-field succession, particularly during the temporal transition from cultivation to abandonment. Rates of carbon dioxide exchange were measured for

Ryan E. Emanuel; John D. Albertson; Howard E. Epstein; Christopher A. Williams

2006-01-01

307

Interaction of acid rain and global changes: Effects on terrestrial and aquatic ecosystems  

Microsoft Academic Search

Both acid deposition and changes in the global atmosphere and climate affect terrestrial and aquatic ecosystems. In the atmosphere sulphate aerosols tend to increase haze, altering the global radiation balance. Increased nitrogen deposition to N-limited systems such as boreal forests results in increased growth and increased sequestration of atmospheric CO2, slowing the increase in CO2 levels in the atmosphere. Future

R. F. Wright; D. W. Schindler

1995-01-01

308

Terrestrial and Extraterrestrial Fullerenes  

Microsoft Academic Search

This paper reviews reports of occurrences of fullerenes in circumstellar media, interstellar media, meteorites, interplanetary dust particles (IDPs), lunar rocks, hard terrestrial rocks from Shunga (Russia), Sudbury (Canada) and Mitov (Czech Republic), coal, terrestrial sediments from the Cretaceous?Tertiary?Boundary and Permian?Triassic?Boundary, fulgurite, ink sticks, dinosaur eggs, and a tree char. The occurrences are discussed in the context of known and postulated

D. Heymann; L. W. Jenneskens; J. Jehli?ka; Carola Koper; E. J. Vlietstra

2003-01-01

309

The Nitrogen Cycle in Terrestrial Ecosystems  

Microsoft Academic Search

The terrestrial nitrogen (N) cycle comprises soil, plant and animal pools that contain relatively small quantities of biologically\\u000a active N, in comparison to the large pools of relatively inert N in the lithosphere and atmosphere, but that nevertheless\\u000a exert a substantial influence on the dynamics of the global biogeochemical N cycle. After carbon (ca. 400 g kg?1) and oxygen (ca.

Ann McNeill; Murray Unkovich

310

Methane production in terrestrial arthropods  

SciTech Connect

The authors have screened more than 110 representatives of the different taxa of terrestrial arthropods for methane production in order to obtain additional information about the origins of biogenic methane. Methanogenic bacteria occur in the hindguts of nearly all tropical representatives of millipedes (Diplopoda), cockroaches (Blattaria), termites (Isoptera), and scarab beetles (Scarabaeidae), while such methanogens are absent from 66 other arthropod species investigated. Three types of symbiosis were found: in the first type, the arthropod's hindgut is colonized by free methanogenic bacteria; in the second type, methanogens are closely associated with chitinous structures formed by the host's hindgut; the third type is mediated by intestinal anaerobic protists with intracellular methanogens. Such symbiotic associations are likely to be a characteristic property of the particular taxon. Since these taxa represent many families with thousands of species, the world populations of methane-producing arthropods constitute an enormous biomass. The authors show that arthropod symbionts can contribute substantially to atmospheric methane.

Hackstein, J.H.P.; Stumm, C.K. (Catholic Univ. of Nijmegen (Netherlands))

1994-06-07

311

The impact of early Holocene Arctic Shelf flooding on climate in an atmosphere-ocean-sea-ice model  

NASA Astrophysics Data System (ADS)

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.

Blaschek, M.; Renssen, H.

2013-07-01

312

Terrestrial Carbon Cycle Dynamics under Recent and Future Climate Change  

Microsoft Academic Search

The behavior of the terrestrial carbon cycle under historical and future climate change is examined using the University of Victoria Earth System Climate Model, now coupled to a dynamic terrestrial vegetation and global carbon cycle model. When forced by historical emissions of CO2 from fossil fuels and land-use change, the coupled climate-carbon cycle model accurately reproduces historical atmospheric CO2 trends,

H. Damon Matthews; Andrew J. Weaver; Katrin J. Meissner

2005-01-01

313

Responses of early, mid and late season apple cultivars to postharvest application of 1-methylcyclopropene (1-MCP) under air and controlled atmosphere storage conditions  

Microsoft Academic Search

The potential for commercial application of 1-methylcyclopropene (1-MCP) to maintain quality of ‘McIntosh’, ‘Empire’, ‘Delicious’ and ‘Law Rome’ apples under air and controlled atmosphere (CA) storage conditions was investigated. These cultivars represent early, mid and late season apples with ripening rates ranging from fast to slow. 1-MCP gas concentrations used were 0.5, 1 and 2 ?l l?1, generated from measured

Christopher B Watkins; Jacqueline F Nock; Bruce D Whitaker

2000-01-01

314

Stable Carbon and Nitrogen Isotopes in a Peat Profile Are Influenced by Early Stage Diagenesis and Changes in Atmospheric CO(2) and N Deposition.  

PubMed

In this study, we test whether the ?(13)C and ?(15)N in a peat profile are, respectively, linked to the recent dilution of atmospheric ?(13)CO(2) caused by increased fossil fuel combustion and changes in atmospheric ?(15)N deposition. We analysed bulk peat and Sphagnum fuscum branch C and N concentrations and bulk peat, S. fuscum branch and Andromeda polifolia leaf ?(13)C and ?(15)N from a 30-cm hummock-like peat profile from an Aapa mire in northern Finland. Statistically significant correlations were found between the dilution of atmospheric ?(13)CO(2) and bulk peat ?(13)C, as well as between historically increasing wet N deposition and bulk peat ?(15)N. However, these correlations may be affected by early stage kinetic fractionation during decomposition and possibly other processes. We conclude that bulk peat stable carbon and nitrogen isotope ratios may reflect the dilution of atmospheric ?(13)CO(2) and the changes in ?(15)N deposition, but probably also reflect the effects of early stage kinetic fractionation during diagenesis. This needs to be taken into account when interpreting palaeodata. There is a need for further studies of ?(15)N profiles in sufficiently old dated cores from sites with different rates of decomposition: These would facilitate more reliable separation of depositional ?(15)N from patterns caused by other processes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11270-011-1001-8) contains supplementary material, which is available to authorized users. PMID:22707802

Esmeijer-Liu, Alice J; Kürschner, Wolfram M; Lotter, André F; Verhoeven, Jos T A; Goslar, Tomasz

2012-01-25

315

Numerical Modelling of the GCM of the Martian Atmosphere  

NASA Astrophysics Data System (ADS)

Numerical modelling of atmospheric flows, originally developed for the needs of terrestrial meteorology and climatology, is now more and more frequently applied to the study of planetary atmospheres. General Circulation Models (GCM's) similar to the models which have been developed for the terrestrial atmosphere can be adapted without major difficulties to the conditions of the other telluric planets (see the accompanying paper by Hourdin et al., 'Numerical Modelling of the Circulation of Superrotating Atmospheres: Venus and Titan'). The first attempts at numerical simulation of the circulation of the Martian atmosphere were made as early as the late sixties by Leovy and collaborators. They provided strong evidence for the fact, still disputed at that time, that the Martian polar caps mostly consisted of CO2 ice. Since then, several groups have developed Martian GCM's, which produce results in general remarkable agreement with the available observations. One recent finding obtained from GCM's is that the seasonal cycle of surface pressure is not only due to the condensation-sublimation cycle of the atmospheric CO2. It is also modulated by a seasonal mass transfer between the two hemispheres (itself due to the mean difference in altitude between the hemispheres) and by geostrophic adjustment of the mass field to the seasonally varying circulation. The Laboratoire de Meteorologie Dynamique, CNRS and Atmospheric, Oceanic and Planetary Physics, Oxford University are currently engaged in a joint project, sponsored by ESA, to produce a database of atmospheric statistics of the Martian atmosphere (see the accompanying paper by Read et al., 'A Climate Database for the Martian Atmosphere'). The database will be produced from runs performed with the GCM's developed by the two groups, which are fairly representative of the variability existing in the methods for simulation of atmospheric circulation. In addition to its own scientific interest, and to providing estimates of the physical conditions that a probe can encounter in the Martian atmosphere, numerical simulation can be extremely useful for the exploitation of the data transmitted by planetary probes. Assimilation techniques, similar to those which are used for terrestrial meteorology, are developed by both groups in order to exploit observations of the Martian atmosphere.

Talagrand, O.; Forget, F.; Fournier, R.; Hourdin, F.

1996-12-01

316

The Boreal Ecosystem-Atmosphere Study (BOREAS): An Overview and Early Results from the 1994 Field Year  

Microsoft Academic Search

The Boreal Ecosystem Atmosphere Study (BOREAS) is large-scale international field experiment that has the goal of improving our understanding of the exchanges of radiative energy, heat water, CO2, and trace gases between the boreal forest and the lower atmosphere. An important objective of BORES is collect the data needed to improve computer simulation models of the processes controlling these exchanges

Piers Sellers; Forrest Hall; K. Jon Ranson; Hank Margolis; Bob Kelly; Dennis Baldocchi; Gerry den Hartog; Josef Cihlar; Michael G. Ryan; Barry Goodison; Patrick Crill; Dennis Lettenmaier; Diane E. Wickland

1995-01-01

317

Terrestrial FeO Continuum Emission Observed in Sky Spectra  

NASA Astrophysics Data System (ADS)

The terrestrial continuum emission in the visible spectral region has often been studied by both astronomers and aeronomers, in order to clarify backgrounds and the nature of the emissions. New observations from the ESI spectrograph on the Keck II telescope, as well as from the OSIRIS/Odin spectrograph and orbiter, have established that a major component of the emission originates with the FeO molecule [Evans et al., 2010]. This quasi-continuum peaks at 5950 A and extends from 5000 A well into the infrared. The identity has been demonstrated by comparison with meteor trains and laboratory measurements [Jenniskens et al., 2000]. Early studies of the continuum show consistency with the FeO emission as presently observed [Gadsden and Marovich, 1973]. Analysis of spectra from Kitt Peak [Neugent and Massey, 2010] demonstrates the great similarity between FeO emission in a clean atmosphere and high pressure sodium lamp emission in a polluted atmosphere. This research was supported by NSF Aeronomy under Grant ATM-0637433 . Evans, W.F.J., et al., Geophys. Res. Lett. [in press, 2010] Gadsden, M. and E. Marovich, J. Atm. Terr. Phys., 35, 1601-1614 [1973] Jenniskens, P., et al., Earth, Moon and Planets, 82-83, 429-434 [2000] Neugent, K.F. and P. Massey, PASP [in press, 2010

Slanger, Tom G.; Melchiorri, R.; Saran, D. V.

2011-01-01

318

Carbon stabilization on terrestrial landscapes  

NASA Astrophysics Data System (ADS)

While terrestrial climate models view C budgets through time-slices of environmental reconstructions, yet during climate transitions, pervasive geomorphic response to climate likely dictate the direction and magnitude of C exchange. Geomorphic processes therefore act as disturbance events that have the potential to create large feedbacks to climate regulation through carbon burial or carbon release. Quantifying the rates of carbon accumulation in various types of deposits allows us to assess intensities of C burial, whereas the spatial extent and timing of geomorphic processes allows us to quantify the net impact on atmospheric CO2 budgets. Mechanisms and forms of C that are buried or stored lend insights into the longevity of these geomorphic events that dictate land-atmosphere C exchange. Chronosequences of fluvial, loess, and coastal deposits dated by various chronologic tools were used to calculate carbon intensities, or accumulation rates, into soil and deep sediment. Vertical cores of peat and permafrost provide such rates through direct aging of organic carbon preserved in the cores. Rates of input to soil and surface sediment varied by 4 orders of magnitude, which reflects variations in both plant production and decomposition over various timescales of decades to millennia. In general, shallow and shorterm rates are higher than deep, longterm rates. Based on the soil property that best predicts C storage and turnover, we hypothesize different mechanisms of stabilization for selected soil profiles: For example clay content, free iron oxides, freezing temperatures were key in C stabilization within the upper meter of Alfisols, Ultisols, and Cryosols, respectively.

Harden, Jennifer W.; Lawrence, Corey; Trumbore, Susan; O'Donnell, Jonathan; Vanoost, Kristof

2010-05-01

319

Stability of Earth-Like N2 Atmospheres: Implications for Habitability  

NASA Astrophysics Data System (ADS)

According to recent studies related to the EUV heating by the young Sun of Earth's nitrogen atmosphere, upper atmosphere temperatures could rise up to several thousand Kelvin. For fluxes larger ? 7 times that of today's Sun the thermosphere changes from a hydrostatic to a dynamically expanding non-hydrostatic regime, adiabatically cools but expands beyond the magnetopause so that the magnetosphere is not able to protect the upper atmosphere from solar wind erosion. A N2-rich terrestrial atmosphere would have been lost within a few million years during the EUV active period of the young Sun ? 4 Ga ago. These results indicate that a hydrogen-rich gaseous envelope, which could have remained from Earths protoatmosphere and/or higher atmospheric CO2 amounts may have protected Earth's atmospheric nitrogen inventory against efficient escape to space. An alternative scenario would be that the nitrogen in Earth's early atmosphere was degassed or delivered during the late heavy bombardment period, where the solar EUV flux decreased to values < 7 times of the modern value. Finally, we discuss how EUV heated and extended upper atmospheres and their interaction with the host star's plasma environment could be observed around transiting Earth-like exoplanets at dwarf stars by space observatories such as the WSO-UV. Such future observations could be used to test the discussed atmospheric evolution scenarios and would enhance our understanding on the impact on the activity of the young Sun/star on the early atmospheres of Venus, Earth, Mars and exoplanets.

Lammer, Helmut; Kislyakova, Kristina G.; Güdel, Manuel; Holmström, Mats; Erkaev, Nikolai V.; Odert, Petra; Khodachenko, Maxim L.

320

Diterpenoids of terrestrial origin.  

PubMed

Covering January to December 2012. Previous review, Nat.Prod.Rep., 2012, 29, 890-898.This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, abietanes, pimaranes, kauranes, cembranes and their cyclization products. There are 169 references. PMID:23942594

Hanson, James R

2013-08-13

321

Upwelling Terrestrial Radiation  

NSDL National Science Digital Library

The Stefan-Boltzmann Law is a fundamental law of physics. In this lesson, students will use this law and the near-ground air temperature to compute the hourly irradiance emitted by the surface of Earth. Then comparisons will be made with actual observations of this variable, called upwelling terrestrial radiation.

322

Altitudinal terrestrial isopod diversity  

Microsoft Academic Search

We have assessed the diversity of terrestrial isopods across an elevational and habitat gradient on Mt. Panachaiko (NW Peloponnisos, Greece). Previous knowledge on the biodiversity of this mountain was restricted to very few records of individual species, and no systematic sampling had ever been applied for any animal taxon. We selected the most representative habitat types within an altitudinal range

Spyros Sfenthourakis; Ioannis Anastasiou; Theodora Strutenschi

2005-01-01

323

Cometary origin of carbon and water on the terrestrial planets.  

PubMed

An early high-temperature phase of the protosolar accretion disk is implied by at least three different telltales in chondrites and confirmed by peculiarities in the dust grains of comet Halley. The existence this high-temperature phase implies a large accretion rate hence a massive early disk. This clarifies the origin of the Kuiper Belt and of the Oort cloud, those two cometary populations of different symmetry that subsist today. Later, when the dust sedimented and was removed from the thermal equilibrium with the gas phase, a somewhat lower temperature of the disk explains the future planets' densities as well as the location beyond 2.6 AU of the carbonaceous chondrite chemistry. This lower temperature remains however large enough to require an exogenous origin for all carbon and all water now present in the Earth. The later orbital diffusion of planetesimals, which is required by protoplanelary growth, is needed to explain the origin of the terrestrial biosphere (atmosphere, oceans, carbonates and organic compounds) by a veneer mostly made of comets. PMID:11538154

Delsemme, A H

1992-01-01

324

Optical SETI with NASA's Terrestrial Planet Finder  

Microsoft Academic Search

NASA's space-borne nulling interferometer (the Terrestrial Planet Finder—TPF) will look for the traces of early life in the infrared spectra of extrasolar planets, beginning in roughly 2010. We point out that this instrument, as currently envisioned, will also be sensitive to deliberate laser transmissions from a technologically advanced civilization. A kilowatt-class infrared laser with a 10-m beam director would produce

Andrew Howard; Paul Horowitz

2001-01-01

325

The Paleozoic to Mesozoic carbon cycle revisited: The carbon isotopic composition of terrestrial organic matter  

Microsoft Academic Search

Two thousand one hundred forty-eight carbon isotope values for terrestrial organic matter (plant fossils, coal, bulk terrestrial organic matter) provide a proxy record for temporal changes in the global carbon cycle. ?13CTOM, ?13Ccarb, and ?13CCO2 allow a full evaluation of carbon transfer in the atmosphere-ocean system as well as between the marine and the terrestrial realm. The temporal evolution of

Harald Strauss; Wolfgang Peters-Kottig

2003-01-01

326

The Paleozoic to Mesozoic carbon cycle revisited: The carbon isotopic composition of terrestrial organic matter  

Microsoft Academic Search

Two thousand one hundred forty-eight carbon isotope values for terrestrial organic matter (plant fossils, coal, bulk terrestrial organic matter) provide a proxy record for temporal changes in the global carbon cycle. delta13CTOM, delta13Ccarb, and delta13CCO2 allow a full evaluation of carbon transfer in the atmosphere-ocean system as well as between the marine and the terrestrial realm. The temporal evolution of

Harald Strauss; Wolfgang Peters-Kottig

2003-01-01

327

Arsenic Speciation of Terrestrial Invertebrates  

Microsoft Academic Search

The distribution and chemical form (speciation) of arsenic in terrestrial food chains determines both the amount of arsenic available to higher organisms, and the toxicity of this metalloid in affected ecosystems. Invertebrates are part of complex terrestrial food webs. This paper provides arsenic concentrations and arsenic speciation profiles for eight orders of terrestrial invertebrates collected at three historical gold mine

Maeve M. Moriarty; Iris Koch; Robert A. Gordon; Kenneth J. Reimer

2009-01-01

328

Solar-Terrestrial Data Integration using Ontologies  

NASA Astrophysics Data System (ADS)

Data-integration across a number of disciplines is a key requirement to be facilitated by virtual observatories and in particular the Virtual Solar-Terrestrial Observatory(VSTO). Our experience to date indicates that semantic interoperability is a viable and robust approach. We have encodings for the VSTO ontology in OWL - the Web Ontology Language - using both open-source and commercial tools and have implemented a number of use-cases. We aim to demonstrate data-integration between solar atmospheric data (e.g. coronal mass ejections), and the resulting impacts on the terrestrial ionosphere (e.g.aurora). In this presentation, we outline the methodologies, the developed use-cases, ontologies and their current implementation.

Cinquini, L.; McGuinness, D.; Fox, P.; Benedict, J.; Darnell, T.; Middleton, D.; Garcia, J.; West, P.

2006-05-01

329

Method for identifying anomalous terrestrial heat flows  

DOEpatents

A method for locating and mapping the magnitude and extent of terrestrial heat-flow anomalies from 5 to 50 times average with a tenfold improved sensitivity over orthodox applications of aerial temperature-sensing surveys as used for geothermal reconnaissance. The method remotely senses surface temperature anomalies such as occur from geothermal resources or oxidizing ore bodies by: measuring the spectral, spatial, statistical, thermal, and temporal features characterizing infrared radiation emitted by natural terrestrial surfaces; deriving from these measurements the true surface temperature with uncertainties as small as 0.05 to 0.5 K; removing effects related to natural temperature variations of topographic, hydrologic, or meteoric origin, the surface composition, detector noise, and atmospheric conditions; factoring out the ambient normal-surface temperature for non-thermally enhanced areas surveyed under otherwise identical environmental conditions; distinguishing significant residual temperature enhancements characteristic of anomalous heat flows and mapping the extent and magnitude of anomalous heat flows where they occur.

Del Grande, Nancy Kerr (San Leandro, CA)

1977-01-25

330

The Natural Terrestrial Carbon Sequestration Potential of Rocky Mountain Soils Derived From Volcanic Bedrock  

Microsoft Academic Search

The possible economic and environmental ramifications of climate change have stimulated a range of atmospheric carbon mitigation actions, as well as, studies to understand and quantify potential carbon sinks. However, current carbon management strategies for reducing atmospheric emissions underestimate a critical component. Soils represent between 18 - 30% of the terrestrial carbon sink needed to prevent atmospheric doubling of CO2

D. B. Yager; A. Burchell; R. H. Johnson

2008-01-01

331

Gaseous ammonia fluxes and background concentrations in terrestrial ecosystems of the United States  

Microsoft Academic Search

Ammonia (NH[sub 3]) is the dominant gaseous base in the atmosphere and the principal neutralizing agent for atmospheric acids, yet remains one of the least well characterized atmospheric trace compounds. In particular, the spactial and temporal distribution of the background concentrations in terrestrial ecosystems and the importance of natural emissions from undisturbed soils and vegetation is poorly understood. This situation

A. O. Langford; F. C. Fehsenfeld; J. Zachariassen; D. S. Schimel

1992-01-01

332

Abiotic nitrogen fixation on terrestrial planets: reduction of NO to ammonia by FeS.  

PubMed

Understanding the abiotic fixation of nitrogen and how such fixation can be a supply of prebiotic nitrogen is critical for understanding both the planetary evolution of, and the potential origin of life on, terrestrial planets. As nitrogen is a biochemically essential element, sources of biochemically accessible nitrogen, especially reduced nitrogen, are critical to prebiotic chemistry and the origin of life. Loss of atmospheric nitrogen can result in loss of the ability to sustain liquid water on a planetary surface, which would impact planetary habitability and hydrological processes that shape the surface. It is known that NO can be photochemically converted through a chain of reactions to form nitrate and nitrite, which can be subsequently reduced to ammonia. Here, we show that NO can also be directly reduced, by FeS, to ammonia. In addition to removing nitrogen from the atmosphere, this reaction is particularly important as a source of reduced nitrogen on an early terrestrial planet. By converting NO directly to ammonia in a single step, ammonia is formed with a higher product yield (~50%) than would be possible through the formation of nitrate/nitrite and subsequent conversion to ammonia. In conjunction with the reduction of NO, there is also a catalytic disproportionation at the mineral surface that converts NO to NO? and N?O. The NO? is then converted to ammonia, while the N?O is released back in the gas phase, which provides an abiotic source of nitrous oxide. PMID:22283408

Summers, David P; Basa, Ranor C B; Khare, Bishun; Rodoni, David

2012-01-27

333

Reconciling apparent inconsistencies in estimates of terrestrial CO2 sources and sinks  

Microsoft Academic Search

The magnitude and location of terrestrial carbon sources and sinks remains subject to large uncertainties. Estimates of terrestrial CO2 fluxes from ground-based inventory measurements typically find less carbon uptake than inverse model calculations based on atmospheric CO2 measurements, while a wide range of results have been obtained using models of different types. However, when full account is taken of the

J. I. House; I. C. Prentice; N. Ramankutty; R. A. Houghton; M. Heimann

2003-01-01

334

EVALUATION OF SITE AND CONTINENTAL TERRESTRIAL CARBON CYCLE SIMULATIONS WITH NORTH AMERICAN FLUX TOWER OBSERVATIONS  

Microsoft Academic Search

Terrestrial carbon models are widely used to diagnose past ecosystem-atmosphere carbon fluxes in response to climate variability, and are a critical component of coupled climate-carbon model used to predict global climate change. The North American Carbon Program (NACP) Interim Regional and Site Interim Synthesis activities collected a broad sampling of terrestrial carbon model results run at both regional and site

B. M. Raczka; K. J. Davis

2009-01-01

335

Evaluation of Site and Continental Terrestrial Carbon Cycle Simulations with North American Flux Tower Observations  

Microsoft Academic Search

Terrestrial carbon models are widely used to diagnose past ecosystem-atmosphere carbon flux responses to climate variability, and are a critical component of coupled climate-carbon model used to predict global climate change. The North American Carbon Program (NACP) Interim Regional and Site Interim Synthesis activities collected a broad sampling of terrestrial carbon model results run at both regional and site level.

B. M. Raczka; K. J. Davis

2010-01-01

336

Carbon Sequestration in Terrestrial Ecosystems: A Status Report on R and D Progress.  

National Technical Information Service (NTIS)

Sequestration of carbon in terrestrial ecosystems is a low-cost option that may be available in the near-term to mitigate increasing atmospheric CO(sub 2) concentrations, while providing additional benefits. Storing carbon in terrestrial ecosystems can be...

G. K. Jacobs

2001-01-01

337

Volatile organic compound emissions in relation to plant carbon fixation and the terrestrial carbon budget  

Microsoft Academic Search

A substantial amount of carbon is emitted by terrestrial vegetation as biogenic volatile organic compounds (VOC), which contributes to the oxidative capacity of the atmosphere, to particle production and to the carbon cycle. With regard to the carbon budget of the terrestrial biosphere, a release of these carbon compounds is regarded as a loss of photosynthetically fixed carbon. The significance

Jürgen Kesselmeier; Paolo Ciccioli; Uwe Kuhn; Paolo Stefani; Thomas Biesenthal; Stefanie Rottenberger; Annette Wolf; Marina Vitullo; Ricardo Valentini; Antonio Nobre; Pavel Kabat; Meinrat O. Andreae

2002-01-01

338

Mass dragged from Mars's atmosphere by the solar wind  

NASA Astrophysics Data System (ADS)

In the past Mars had a denser atmosphere, but it lacks a magnetic field to protect the ionosphere and exosphere from the solar wind. A model describing the loss of atmosphere by the erosion of the solar wind in geologic time is presented. Recent results shows that the Martian dynamo existed in Early and Middle Noachian. Then solar wind erosion would have started at the end of Middle Noachian or the beginning of Late Noachian. With this assumption the amount of volatiles dragged by the solar wind, if the chronology developed by Neukum and Wise is correct, is in the range of 0.472 to 1.89 Terrestrial Atmospheric Masses (TAM). If the chronology developed by Hartmann et al. is correct, the loss remains in the range of 0.0624 to 0.25 TAM.

Durand-Manterola, H. J.

2003-12-01

339

Polar terrestrial ecosystems, permafrost, and extreme warm paleoclimate dynamics (Invited)  

NASA Astrophysics Data System (ADS)

Coupled Global Climate Model (GCM)-vegetation simulations of Mesozoic and early Cenozoic “greenhouse” paleoclimates show the importance of terrestrial ecosystems in maintaining warm continental interiors and ice-free polar land areas. Such simulations also offer excellent potential for model-data comparison, because simulated distributions of vegetation reflect a more complete seasonal picture of regional climates than the mean annual conditions reflected in most geochemical proxies. Terrestrial ecosystems may have also played a critical role in extreme climate events, such as the Palaeocene-Eocene Thermal Maximum (PETM) hyperthermal event (~55 Ma). Hitherto, most explanations of this event point to a release of isotopically light (-60 ‰) marine gas hydrate (methane) as the most likely cause of the ~3 ‰ carbon isotope shift and sudden 5-9 deg C global warming that characterize the event. However, mass balance arguments suggest the mass of carbon from this reservoir is insufficient to cause the presumed warming, leaving the source of the carbon and/or the strength of amplifying warming feedbacks an open question. Here we use results from a GCM to show that Antarctica was a suitable location for massive carbon sequestration in peat and permafrost-dominated environments during the Palaeocene leading up the PETM event. Levels of assumed atmospheric CO2 and CH4 concentrations around the time of the event are shown to cross the threshold for melting vast areas of frozen soil on an unglaciated Antarctic continent, which had a subaerial surface area ~25% larger than today. This previously underappreciated potential source of carbon would have been large enough to account for a significant fraction of the total warming at the PETM once a warming threshold was reached, whereby permafrost began to melt and methane and relict soil carbon were suddenly released. If this mechanism did play a role in abrupt and extreme global warming events such as the PETM, it implies serious consequences for the thawing of similar environments in the modern boreal high latitudes.

Deconto, R.; Pagani, M.; Pollard, D.; Beerling, D. J.

2009-12-01

340

The role of declining Arctic sea ice in recent decreasing terrestrial Arctic snow depths  

NASA Astrophysics Data System (ADS)

The dramatic decline in Arctic sea ice cover is anticipated to influence atmospheric temperatures and circulation patterns. These changes will affect the terrestrial climate beyond the boundary of the Arctic, consequently modulating terrestrial snow cover. Therefore, an improved understanding of the relationship between Arctic sea ice and snow depth over the terrestrial Arctic is warranted. We examined responses of snow depth to the declining Arctic sea ice extent in September, during the period of 1979-2006. The major reason for a focus on snow depth, rather than snow cover, is because its variability has a climatic memory that impacts hydrothermal processes during the following summer season. Analyses of combined data sets of satellite measurements of sea ice extent and snow depth, simulated by a land surface model (CHANGE), suggested that an anomalously larger snow depth over northeastern Siberia during autumn and winter was significantly correlated to the declining September Arctic sea ice extent, which has resulted in cooling temperatures, along with an increase in precipitation. Meanwhile, the reduction of Arctic sea ice has amplified warming temperatures in North America, which has readily offset the input of precipitation to snow cover, consequently further decreasing snow depth. However, a part of the Canadian Arctic recorded an increase in snow depth driven locally by the diminishing September Arctic sea ice extent. Decreasing snow depth at the hemispheric scale, outside the northernmost regions (i.e., northeastern Siberia and Canadian Arctic), indicated that Arctic amplification related to the diminishing Arctic sea ice has already impacted the terrestrial Arctic snow depth. The strong reduction in Arctic sea ice anticipated in the future also suggests a potential long-range impact on Arctic snow cover. Moreover, the snow depth during the early snow season tends to contribute to the warming of soil temperatures in the following summer, at least in the northernmost regions.

Park, Hotaek; Walsh, John E.; Kim, Yongwon; Nakai, Taro; Ohata, Tetsuo

2013-06-01

341

Decadal patterns in ?18O of atmospheric CO2  

NASA Astrophysics Data System (ADS)

The stable oxygen isotope 18O is unique to isotope ecology in that it links the hydrosphere to the carbon cycle. Since land biosphere fluxes are the dominant influences on 18O of atmospheric CO2, particularly on shorter times scales, analysis of atmospheric ?18O trends can provide useful insight into the terrestrial carbon cycle. The isotopic values imprinted by leaf water and soil water exchanges with CO2 out-compete those from ocean exchange, fossil fuel and biomass burning, and stratospheric reactions. The opposing isotopic imprints of photosynthesis and ecosystem respiration therefore control the majority of atmospheric 18O concentration. The resulting seasonal cycle in ?18O data of peaks during early summer, when photosynthesis dominates, and lows during early winter, when respiration dominates, has been clearly established. However, the reasons for the interannual variability of atmospheric 18O remain unknown. Studies have shown that the size and isotopic value of the “retrodiffusion” flux- the CO2 that enters and exits leaves without being fixed by photosynthesis- is a function of stomatal conductance, which is affected by the relative humidity in the surrounding atmosphere. We observe that data from numerous global sites shows a global decadal oscillation in ?18O, suggesting a climatological forcing. We compare decadal trends in ?18O with climate oscillations and the 11-year solar cycle, as well as relative humidity records, examining correlations and proposing associated mechanisms. Understanding the decadal patterns in atmospheric 18O of CO2 will shed light on global terrestrial carbon fluxes and the carbon-water interaction on decadal time scales, potentially helping to scale human versus natural impacts on this coupled system.

Zakem, E.; White, J. W.

2010-12-01

342

Hypoxia, Global Warming, and Terrestrial Late Permian Extinctions  

Microsoft Academic Search

A catastrophic extinction occurred at the end of the Permian Period. However, baseline extinction rates appear to have been elevated even before the final catastrophe, suggesting sustained environmental degradation. For terrestrial vertebrates during the Late Permian, the combination of a drop in atmospheric oxygen plus climate warming would have induced hypoxic stress and consequently compressed altitudinal ranges to near sea

Raymond B. Huey; Peter D. Ward

2005-01-01

343

Influence of Geoengineered Climate on the Terrestrial Biosphere  

Microsoft Academic Search

Various geoengineering schemes have been proposed to counteract anthropogenically induced climate change. In a previous study, it was suggested that a 1.8% reduction in solar radiation incident on the Earth’s surface could noticeably reduce regional and seasonal climate change from increased atmospheric carbon dioxide (CO 2). However, the response of the terrestrial biosphere to reduced solar radiation in a CO

Vaishali Naik; Donald J. Wuebbles; Evan H. DeLucia; Jonathan A. Foley

2003-01-01

344

The extra-terrestrial vacuum-ultraviolet wavelength range  

Microsoft Academic Search

Electromagnetic radiation in the vacuum-ultraviolet (VUV) and extra-terrestrial range at wavelengths from 10 nm to 300 nm is absorbed in the upper atmosphere by ozone, molecular and atomic oxygen, and molecular nitrogen. Observations at wavelengths down to ≈ 200 nm can be carried out from stratospheric balloons, and observations below 200 nm require space platforms operating at altitudes above 250

J. Gethyn Timothy; Klaus Wilhelm; Lidong Xia

2010-01-01

345

Terrestrial Planet Finder: technology development plans and progress  

Microsoft Academic Search

One of humanity's oldest questions is whether life exists elsewhere in the Universe. The Terrestrial Planet Finder (TPF) mission can survey stars in our stellar neighborhood to search for planets and perform spectroscopic measurements to identify potential biomarkers in their atmospheres. TPF is planned for launch around 2015. Two major classes of mission have been identified as likely to meet

Chris Lindensmith

2004-01-01

346

Solar-Terrestrial Connection  

NASA Astrophysics Data System (ADS)

Radiation from the Sun and the energy from the SOLAR WIND that crosses the magnetopause have a profound influence on the Earth and its surrounding atmosphere (see also MAGNETOSPHERE OF EARTH: MAGNETOPAUSE). The consequences range from the formation of ozone to the flickering aurorae in both polar regions. The most significant solar variations cause long-term changes in the Earth's atmosphere and...

Rodger, A.; Murdin, P.

2000-11-01

347

Terrestrial nitrogen-carbon cycle interactions at the global scale.  

PubMed

Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen-carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001-2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr(-1) (1.9 Pg C yr(-1)), of which 10 Tg N yr(-1) (0.2 Pg C yr(-1)) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen-carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr(-1) per 1°C degree climate warming) will add an important long-term climate forcing. PMID:23713123

Zaehle, S

2013-05-27

348

Atmospheric circulation in the early Holocene: Sensitivity of the North Atlantic winter climate to moderate changes in the ice-sheet configuration  

NASA Astrophysics Data System (ADS)

A prominent feature of interglacials, such as the Holocene, is the reduced size of the continental ice sheets. At present-day, only two ice-sheets (namely Greenland and Antarctica) exist which themselves are likely to retreat in the future due to global warming. Changes in the global ice-sheet distribution have distinct consequences for the surface climate and the atmospheric circulation since ice-masses shape the topography and define the local surface characteristics. Past interglacial periods offer the potential to study the climate dynamics and stability of warm periods, also concerning the impact of changes in the ice-sheet distribution. For this purpose, we use a comprehensive climate model to perform a set of time-slice simulations for the present, the early-Holocene and the Eemian warm period. In particular, we perform sensitivity experiments to assess the atmosphere's reaction to modest changes in the global ice-sheet distribution. In a first attempt, we focus on a set of four early-Holocene simulations which include the paleo-topographies from 9000BP, 8000BP, 7000BP and the present orography as lower boundary conditions, respectively. The early Holocene orography differs from the present-day state by the presence of remnants of the Laurentide ice-sheet and newly ice-free regions in Scandinavia and North America with a higher altitude due to the post-glacial rebound effect. For all simulations, the orbital forcing is set to the state of 8000BP, whereas the solar constant and greenhouse gas concentrations are fixed on pre-industrial levels. The Northern Hemisphere (NH) winter surface climate shows moderate and mostly non-significant changes due to the different lower boundaries. Significant differences in surface temperature are limited to areas which experience a local change in orography. However, there is a clear impact on the mid-level troposphere downstream of the Laurentide ice sheet remnants leading to a cooling over the North Atlantic and a warming over Southern Europe. These changes are likely associated with a change in the North Atlantic winter jet. The analysis shows that the sub-tropical branch of the jet is intensified whereas the eddy-driven jet is slightly weakened. Nevertheless, the induced changes in the jet do not lead to a change in the main NH modes of atmospheric variability (e.g., the North Atlantic Oscillation or the East Atlantic Pattern). This analysis illustrates that although the impact of the lower boundaries is significant, the magnitude is too small to lead to a significant reorganization of the mean atmospheric flow in the NH.

Merz, N.; Raible, C. C.; Stocker, T. F.

2012-04-01

349

LIFETIME OF EXCESS ATMOSPHERIC CARBON DIOXIDE  

EPA Science Inventory

We explore the effects of a changing terrestrial biosphere on the atmospheric residende time of carbon dioxide using three simple ocean carbon cycling models and a model of global terrestrial carbon cycling. e find differences in model behavior associated with the assumption of a...

350

Terrestrial Fe-oxide Concretions and Mars Blueberries: Comparisons of Similar Advective and Diffusive Chemical Infiltration Reaction Mechanisms  

NASA Astrophysics Data System (ADS)

Abundant iron oxide concretions occurring in Navajo Sandstone of southern Utah and those discovered at Meridiani Planum, Mars share many common observable physical traits such as their spheriodal shapes, occurrence, and distribution patterns in sediments. Terrestrial concretions are products of interaction between oxygen-rich aquifer water and basin-derived reducing (iron-rich) water. Water-rock interaction simulations show that diffusion of oxygen and iron supplied by slow-moving water is a reasonable mechanism for producing observed concretion patterns. In short, southern Utah iron oxide concretions are results of Liesegang-type diffusive infiltration reactions in sediments. We propose that the formation of blueberry hematite concretions in Mars sediments followed a similar diagenetic mechanism where iron was derived from the alteration of volcanic substrate and oxygen was provided by the early Martian atmosphere. Although the terrestrial analog differs in the original host rock composition, both the terrestrial and Mars iron-oxide precipitation mechanisms utilize iron and oxygen interactions in sedimentary host rock with diffusive infiltration of solutes from two opposite sources. For the terrestrial model, slow advection of iron-rich water is an important factor that allowed pervasive and in places massive precipitation of iron-oxide concretions. In Mars, evaporative flux of water at the top of the sediment column may have produced a slow advective mass-transfer mechanism that provided a steady source and the right quantity of iron. The similarities of the terrestrial and Martian systems are demonstrated using a water-rock interaction simulator Sym.8, initially in one-dimensional systems. Boundary conditions such as oxygen content of water, partial pressure of oxygen, and supply rate of iron were varied. The results demonstrate the importance of slow advection of water and diffusive processes for producing diagenetic iron oxide concretions.

Park, A. J.; Chan, M. A.

2006-12-01

351

Wet surface and dense atmosphere on early Mars suggested by the bomb sag at Home Plate, Mars  

NASA Astrophysics Data System (ADS)

We use the Mars Exploration Rover Spirit observation of a bomb sag produced by an explosive volcanic eruption to infer the atmospheric density at the time of eruption. We performed analogue experiments to determine the relationship between the wetness of the substrate and the velocity and density of impacting clasts and 1) the formation (or not) of bomb sags, 2) the morphology of the impact crater, and 3) the penetration depth of the clast. The downward deflection of beds seen on Mars is consistent with water-saturated sediment in the laboratory experiments. Collision angles <20 degrees from vertical are needed to produce bomb sags. From the experiments we infer an impact velocity up to 4 × 101 m/s, lower than ejection velocities during phreatic and phreatomagmatic eruptions on Earth. If this velocity represents the terminal subaerial impact velocity, atmospheric density exceeded 0.4 kg/m3 at the time of eruption, much higher than at present.

Manga, Michael; Patel, Ameeta; Dufek, Josef; Kite, Edwin S.

2012-01-01

352

ARAC (Atmospheric Release Advisory Capability): Early phase dose assessment for Department of Energy's Federal Radiological Monitoring and Assessment Program  

Microsoft Academic Search

The Atmospheric Release Advisory Capability (ARAC) is a U.S. Government Department of Energy (DOE)-sponsored emergency-response service designed, developed, and established at Lawrence Livermore National Laboratory to provide real-time predictions of the radiation dose levels resulting from the release of airborne radioactive material. Under the auspices of the U.S. Federal Radiological Emergency Response Plan (FRERP), all major U.S. federal agencies now

T. J. Sullivan; J. S. Nasstrom; G. D. Greenly

1989-01-01

353

Atmospheric Spread of Foot-and-mouth Disease During The Early Phase of The Uk Epidemic 2001  

NASA Astrophysics Data System (ADS)

Foot-and-mouth disease (FMD) is a highly contagious viral disease in cloven-hoofed domesticated and wild animals. The highly contagious nature of FMD is a reflection of the wide range of species which are susceptible, the enormous quantities of virus liberated by infected animals, the range of excretions and secretions which can be infectious, the stability of the virus in the environment, the multiplicity of routes of infection and the very small doses of virus that can initiate infection in susceptible hosts. One of the routes for the spread of the disease is the atmospheric dispersion of virus exhaled by infected animals. Such spread can be rapid and extensive, and it is known in certain circumstances to have occurred over a distance of several hundred kilometres. For the FMD epidemic in UK in 2001, atmospheric dispersion models were applied in real time in order to describe the atmospheric dispersion of virus for the larger outbreaks of the disease. The operational value of such modelling is first of all to identify risk zones, which is helpful to the emergency management. The paper addresses the modelling techniques and presents results related with the epidemic in UK in 2001.

Sørensen, J. H.; Mikkelsen, T.; Astrup, P.; Alexandersen, S.; Donaldson, A. I.

354

The precambrian evolution of terrestrial life.  

NASA Astrophysics Data System (ADS)

The early appearance of life on Earth suggests that under appropriate environmental conditions the probability of chemical evolution proceeding to the point of biogenesis may be reasonably high. Most of biological history has been the history of microorganisms, with tissue-grade plants and animals characterizing only the most recent 15% or so of the fossil record. Intelligent life has occupied only the latest instant in geological time. The time table of terrestrial evolution is governed more by the particulars of our planet's physical and biological history than by some universal tempo of evolutionary change. One aspect of terrestrial life that is likely to be universal is the organization of populations into efficient biogeochemical systems.

Knoll, A. H.

355

Space and Terrestrial Photovoltaics: Synergy and Diversity  

NASA Astrophysics Data System (ADS)

A historical view of the research and development in photovoltaics from the perspective of both the terrestrial and the space communities is presented from the early days through the '70s and '80s and the '90s and beyond. The synergy of both communities in the beginning and once again in the present and hopefully future are highlighted, with examples of the important features in each program. The space community which was impressed by the light-weight and reliability of photovoltaics drove much of the early development. Even up to today, nearly every satellites and other scientific space probe that has been launched has included some solar power. However, since the cost of these power systems were only a small fraction of the satellite and launch cost, the use of much of this technology for the terrestrial marketplace was not feasible. It was clear that the focus of the terrestrial community would be best served by reducing costs. This would include addressing a variety of manufacturing issues and raising the rate of production. Success in these programs and a resulting globalization of effort resulted in major strides in the reduction of PV module costs and increased production. Although, the space community derived benefit from some of these advancements, its focus was on pushing the envelope with regard to cell efficiency. The gap between theoretical efficiencies and experimental efficiencies for silicon, gallium arsenide and indium phosphide became almost non-existent. Recent work by both communities have focused on the development thin film cells of amorphous silicon, CuInSe2 and CdTe. These cells hold the promise of lower costs for the terrestrial community as well as possible flexible substrates, better radiation resistance, and higher specific power for the space community. It is predicted that future trends in both communities will be directed toward advances through the application of nanotechnology. A picture is emerging in which the space and terrestrial solar cell communities shall once again share many common goals and, in fact, companies may manufacture both space and terrestrial solar cells in III-V materials and thin film materials. Basic photovoltaics research including these current trends in nanotechnology provides a valuable service for both worlds in that fundamental understanding of cell processes is still vitally important, particularly with new materials or new cell structures. It is entirely possible that one day we might have one solar array design that will meet the criteria for success in both space and on the Earth or perhaps the Moon or Mars.

Bailey, Sheila; Raffaelle, Ryne; Emery, Keith

2002-10-01

356

Atmospheric discharge and dispersion of radionuclides during the Fukushima Dai-ichi Nuclear Power Plant accident. Part I: Source term estimation and local-scale atmospheric dispersion in early phase of the accident.  

PubMed

The atmospheric release of (131)I and (137)Cs in the early phase of the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident from March 12 to 14, 2011 was estimated by combining environmental data with atmospheric dispersion simulations under the assumption of a unit release rate (1 Bq h(-1)). For the simulation, WSPEEDI-II computer-based nuclear emergency response system was used. Major releases of (131)I (>10(15) Bq h(-1)) were estimated when air dose rates increased in FNPP1 during the afternoon on March 12 after the hydrogen explosion of Unit 1 and late at night on March 14. The high-concentration plumes discharged during these periods flowed to the northwest and south-southwest directions of FNPP1, respectively. These plumes caused a large amount of dry deposition on the ground surface along their routes. Overall, the spatial pattern of (137)Cs and the increases in the air dose rates observed at the monitoring posts around FNPP1 were reproduced by WSPEEDI-II using estimated release rates. The simulation indicated that air dose rates significantly increased in the south-southwest region of FNPP1 by dry deposition of the high-concentration plume discharged from the night of March 14 to the morning of March 15. PMID:22406754

Katata, Genki; Ota, Masakazu; Terada, Hiroaki; Chino, Masamichi; Nagai, Haruyasu

2012-03-08

357

Accelerated Sequestration of Terrestrial Plant Biomass in the Deep Ocean  

NASA Astrophysics Data System (ADS)

One of the most efficient uses of aboveground agricultural residues to reduce atmospheric CO2 is burial in sites removed from contact with the atmosphere and in which degradation of lignocellulose is inhibited (Strand and Benford 2009). Similarly by burying forest residues greater benefits for atmospheric carbon accrue compared to incineration or bioethanol production. Accessible planetary sites that are most removed from contact with the atmosphere are primarily the deep ocean sediments. Many deep ocean sediment ecologies are acclimated to massive inputs of terrestrial plant biomass. Nonetheless, marine degradation rates of lignocellulose are slower than terrestrial rates (Keil et al. 2010). Additionally, anaerobic conditions are easily achieved in many deep ocean sediments, inhibiting lignocellulose degradation further, while the dominance of sulfate in the water column as electron acceptor prevents the release of methane from methanogenesis to the atmosphere. The potential benefit of massive removal of excess terrestrial biomass to the deep ocean will be estimated and compared to other uses including biochar and BECS. The impact of the biomass on the marine environment will be discussed and potential sequestration sites in the Gulf of Mexico and the Atlantic compared. Keil, R. G., J. M. Nuwer, et al. (2010). "Burial of agricultural byproducts in the deep sea as a form of carbon sequestration: A preliminary experiment." Marine Chemistry (In Press, online 6 August 2010). Strand, S. E. and G. Benford (2009). "Ocean sequestration of crop residue carbon: recycling fossil fuel carbon back to deep sediments." Environ. Sci. Technol. 43(4): 1000-1007.

Strand, S. E.

2010-12-01

358

Global methane emissions from terrestrial plants.  

PubMed

Recent measurements suggest that the terrestrial plant community may be an important source of methane with global contributions between 62 and 236 Tg CH4 y(-1). If true, terrestrial plants could rival wetlands as being the largest global source of methane forcing us to rethink the methane budget. While further measurements are needed to confirm the methane release rates from this source and their dependencies, in this work we use the preliminary measurements to assess the potential impact of the methane release from this source globally. Using novel techniques we extrapolate the initially reported chamber measurements to the global scale and calculate the global methane emissions from the terrestrial plant community to be in the range 20 to 69 Tg CH4 y(-1). The spread in emissions is largely due to the sensitivity of the global flux to the prescribed temperature dependence of the plant emission rate, which is largely unknown. The spread of calculated emissions is in good agreement with the upper limit imposed on the source during the late pre-industrial period, which we estimate to range from 25 to 54 Tg CH4 y(-1) during the years 0 to 1700 A.D. using the published atmospheric delta13CH4 record. In addition, if we assume that plant emissions have been constant at the mean value of 45 Tg CH4 y(-1), we find that the methane release from wildfires and biomass burning during the pre-industrial span 0-1000 A.D. must be near 12 Tg CH4 y(-1), which would be in better agreement with previous estimates of the pyrogenic source during this time than a methane budget missing the plant source. We conclude that methane release from the terrestrial plant community as presently understood does not require major innovations to the global methane budget. PMID:17612186

Butenhoff, Christopher L; Khalil, M Aslam Khan

2007-06-01

359

Wet surface and dense atmosphere on early Mars inferred from the bomb sag at Home Plate, Mars  

NASA Astrophysics Data System (ADS)

We use the observation by the Mars Exploration Rover Spirit of a bomb sag produced by an explosive volcanic eruption to infer the atmospheric density at the time of eruption. Bomb sags are formed when large ballistically-transported clasts deflect the laminae in the substrates on which the clasts land. We performed analogue experiments to determine the relationship between the wetness of the substrate and the velocity and density of impacting clasts and 1) whether bomb sags will form, 2) the morphology of the impact crater, and 3) the penetration depth of the clast. The downward deflection of beds seen on Mars requires water-saturated sediment in the laboratory experiments. Collision angles < 20 degrees from vertical are needed to produce bomb sags. The analogue experiments show a relationship between penetration depth and specific energy density of the impacting clast. From the experiments we infer an impact velocity of ~10-50 m/s. These are lower than ejection velocities during phreatic and phreatomagmatic eruptions on Earth. Assuming ejection velocities similar to those at maars on Earth, and impact at the terminal velocity, the atmospheric density was > 0.8 kg/m3 (>0.4 bar).

Manga, M.; Patel, A.; Dufek, J.; Kite, E. S.

2011-12-01

360

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  

Microsoft Academic Search

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 CO, while accounting for lateral transfers of forest

Daniel J Hayes; David P Turner; Graham Stinson; David Mcguire; Yaxing Wei; Tristram O. West; Linda S. Heath; Bernardus De Jong; Brian G. McConkey; Richard A. Birdsey; Werner Kurz; Andrew Jacobson; Deborah Huntzinger; Yude Pan; Wilfred M Post; Robert B Cook

2012-01-01

361

Nannofossil carbonate fluxes during the Early Cretaceous: Phytoplankton response to nutrification episodes, atmospheric CO2, and anoxia  

Microsoft Academic Search

Greenhouse episodes during the Valanginian and Aptian correlate with major perturbations in the C cycle and in marine ecosystems, carbonate crises, and widespread deposition of Corg-rich black shales. Quantitative analyses of nannofossil micrite were conducted on continuous pelagic sections from the Southern Alps (northern Italy), where high-resolution integrated stratigraphy allows precise dating of Early Cretaceous geological events. Rock-forming calcareous nannofloras

Elisabetta Erba; Fabrizio Tremolada

2004-01-01

362

Frontal genesis of moisture atmosphere during the early 2008 persistent freezing-rain event in southern China  

Microsoft Academic Search

From January 10 to February 2, 2008, a severe and persistent freezing-rain event occurred in southern and southwestern China.\\u000a Here we use an observational analysis to compare the persistent freezing-rain event in the early 2008 with the winter precipitation\\u000a in the late 2007 over south of the Yangtze River (Jiangnan). The persistent freezing-rain event was directly linked to the\\u000a activity

WeiHong Qian; JiaoLan Fu

2010-01-01

363

Atmospheric CO 2 simulated by the National Center for Atmospheric Research Community Climate Model 1. Mean fields and seasonal cycles  

Microsoft Academic Search

Atmospheric CO 2 has been simulated on-line in a coupled model of the atmosphere and terrestrial land surface. The atmospheric model is a precursor to version 3 of the Commu- nity Climate Model developed at the National Center for Atmospheric Research. It interacts with a mechanistic parameterization of the land surface at each time step. Photosynthesis and respiration fluxes are

S. G. Craig; K. J. Holmén; G. B. Bonan; P. J. Rasch

1998-01-01

364

Early plume and shock wave dynamics in atmospheric-pressure ultraviolet-laser ablation of different matrix-assisted laser ablation matrices  

NASA Astrophysics Data System (ADS)

Pulsed laser ablation of molecular solids is important for identification and quantification in (bio-)organic mass spectrometry, for example using matrix-assisted laser desorption/ionization (MALDI). Recently, there has been a major shift to using MALDI and related laser ablation/post-ionization methods at atmospheric pressure. However, the underlying laser ablation processes, in particular early plume formation and expansion, are still poorly understood. Here, we present a study of the early ablation processes on the ns-time scale in atmospheric pressure UV-laser ablation of anthracene as well as of different common MALDI matrices such as 2,5-dihydroxybenzoic acid (2,5-DHB), ?-cyano-4-hydroxycinnamic acid and sinapinic acid. Material release as well as the formation and expansion of hemi-spherical shock waves were studied by shadowgraphy with high temporal resolution (~5 ns). The applicability of the classical Taylor-Sedov model for expansion of strong shock waves (``point-blast model''), as well as the drag force model, were evaluated to mathematically describe the observed shock wave propagation. The time- and energy-dependent expansion of the shock waves could be described using a Taylor-Sedov scaling law of the form R ~ tq, when a q-exponent of ~0.5 instead of the theoretical value of q = 0.4 was found, indicating a faster expansion than expected. The deviations from the ideal value of q were attributed to the non-negligible influence of ambient pressure, a weak versus strong shock regime, and additional acceleration processes present in laser ablation that surpass the limit of the point-blast model. The onset of shock wave formation at a fluence of ~15-30 mJ/cm2 for the compounds investigated coincides with the onset of bulk material release, whereas, pure desorption below this fluence threshold did not lead to features visible in shadowgraphy.

Schmitz, Thomas A.; Koch, Joachim; Günther, Detlef; Zenobi, Renato

2011-06-01

365

Carbon cycling in extratropical terrestrial ecosystems of the Northern Hemisphere during the 20th century: a modeling analysis of the influences of soil thermal dynamics  

Microsoft Academic Search

There is substantial evidence that soil thermal dynamics are changing in terrestrial ecosystems of the Northern Hemisphere and that these dynamics have implications for the exchange of carbon between terrestrial ecosystems and the atmosphere. To date, large-scale biogeochemical models have been slow to incorporate the effects of soil thermal dynamics on processes that affect carbon exchange with the atmosphere. In

Q. Zhuang; A. D. McGuire; J. M. Melillo; J. S. Clein; R. J. Dargaville; D. W. Kicklighter; R. B. Myneni; J. Dong; V. E. Romanovsky; J. Harden; J. E. Hobbie

2003-01-01

366

Microbial life in terrestrial permafrost: methanogenesis and nitrification in Gelisols as potentials for exobiological processes  

Microsoft Academic Search

The comparability of environmental and climatic conditions of the early Mars and Earth is of special interest for the actual research in astrobiology. Martian surface and terrestrial permafrost areas show similar morphological structures, which suggests that their development is based on comparable processes. Soil microbial investigations of adaptation strategies of microorganisms from terrestrial permafrost in combination with environmental, geochemical and

Dirk Wagner; Eva Spieck; Eberhard Bock; Eva-Maria Pfeiffer

2002-01-01

367

Terrestrial Planets Accreted Dry  

NASA Astrophysics Data System (ADS)

Plate tectonics shaped the Earth, whereas the Moon is a dry and inactive desert. Mars probably came to rest within the first billion years of its history, and Venus, although internally very active, has a dry inferno for its surface. The strong gravity field of a large planet allows for an enormous amount of gravitational energy to be released, causing the outer part of the planetary body to melt (magma ocean), helps retain water on the planet, and increases the pressure gradient. The weak gravity field and anhydrous conditions prevailing on the Moon stabilized, on top of its magma ocean, a thick buoyant plagioclase lithosphere, which insulated the molten interior. On Earth, the buoyant hydrous phases (serpentines) produced by reactions between the terrestrial magma ocean and the wet impactors received from the outer Solar System isolated the magma and kept it molten for some few tens of million years. The elemental distributions and the range of condensation temperatures show that the planets from the inner Solar System accreted dry. The interior of planets that lost up to 95% of their K cannot contain much water. Foundering of their wet surface material softened the terrestrial mantle and set the scene for the onset of plate tectonics. This very same process may have removed all the water from the surface of Venus 500 My ago and added enough water to its mantle to make its internal dynamics very strong and keep the surface very young. Because of a radius smaller than that of the Earth, not enough water could be drawn into the Martian mantle before it was lost to space and Martian plate tectonics never began. The radius of a planet therefore is the key parameter controlling most of its evolutional features.

Albarede, F.; Blichert-Toft, J.

2007-12-01

368

Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations  

Microsoft Academic Search

More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a carbon sink, the size, distribution, and interannual variability of this sink remain uncertain. Here we report a terrestrial carbon sink in the conterminous U.S. at 0.63pg

Jingfeng Xiao; Qianlai Zhuang; Beverly E. Law; Dennis D. Baldocchi; Jiquan Chen; Andrew D. Richardson; Jerry M. Melillo; Kenneth J. Davis; David Y. Hollinger; Sonia Wharton; Ram Oren; Asko Noormets; Marc L. Fischer; Shashi B. Verma; David R. Cook; Ge Sun; Steve McNulty; Steven C. Wofsy; Paul V. Bolstad; Sean P. Burns; Peter S. Curtis; Bert G. Drake; Matthias Falk; David R. Foster; Lianhong Gu; Julian L. Hadley; Gabriel G. Katul; Marcy Litvak; Siyan Ma; Timothy A. Martin; Roser Matamala; Tilden P. Meyers; Russell K. Monson; J. William Munger; Walter C. Oechel; U. Kyaw Tha Paw; Hans Peter Schmid; Russell L. Scott; Gregory Starr; Andrew E. Suyker; Margaret S. Torn

2011-01-01

369

Terrestrial solar spectra, solar simulation and solar cell efficiency measurement  

NASA Astrophysics Data System (ADS)

Fundamentals of light transmittance and, both measured and modeled atmospheric effects (i.e., air mass, molecular and aerosal scattering, and absorption) on terrestrial solar spectra are discussed. Geometric effects, such as global rather than direct beam measurements, and detector orientation are also reviewed. The SERI proposed ASTM global and direct beam terrestrial solar spectra are also presented. A detailed review/evaluation of the spectral characteristics of a number of solar simulators is given. Methods of calibrating the short circuit current of a solar cell with respect to a given irradiance spectrum are discussed. In conclusion, the need for a sophisticated solar simulator is proportional to the spectral mismatch betwen the spectral response of the reference cell used to set the solar simulator and that of the test cell. The ASTM terrestrial solar irradiance spectrum is recommended as a reference, spectrum and, the used either filtered xenon arc or dichroic filtered tungsten halogen lamps for solar simulation is also recommended.

Matson, R.; Bird, R.; Emery, K.

1981-09-01

370

Sequestering Atmospheric Carbon Dioxide  

Microsoft Academic Search

The abrupt climate change, attributed to increase in atmospheric concentration of CO2 and other greenhouse gases, has necessitated identification of technological options to sequester CO2 into other long-lived pools. Other viable pools for C sequestration include geologic, oceanic, and the terrestrial. There is also a potential to convert CO2 into stable minerals. There are geoengineering techniques of CO2 capture and

R. Lal

2009-01-01

371

Origins of Non-mass-dependent Fractionation of Extra-terrestrial Oxygen  

NASA Astrophysics Data System (ADS)

The distribution of oxygen isotopes in meteorites and within the earliest solids that formed in the solar system hints that the precursors of these materials must have undergone a mass-independent process. The mass-independent process is specifically one that fractionates 16O from 17O and 18O. This chemical signature is indicative of non-equilibrium processing, which bear resemblance to some unusual terrestrial phenomenon such as fractionation of ozone in the upper Earth atmosphere. That the mass-independent fractionation of oxygen isotopes is preserved within petrological records presents planetary scientists interesting clues to the events that may have occurred during the formation of the solar system. Currently, there are several hypotheses on the origins of the oxygen isotope distribution within primitive planetary materials, which include both thermal and photochemical models. We present a new model based on a physico-chemical hypothesis for the origin of non-mass-dependent O-isotope distribution in oxygen-bearing extra-terrestrial materials, which originated from the disproportionation of CO in dark molecular clouds to create CO2 reservoirs. The disproportionation created a reservoir of heavy oxygen isotopes and could have occurred throughout the evolution of the disk. The CO2 was a carrier of the isotope anomaly in the solar nebula and we propose that non-steady-state mixing of these reservoirs with the early rock-forming materials during their formation corresponds with the birth and evolution of the solar system.

Barcena, Homar; Connolly, Harold C.

2012-08-01

372

Decadal Variability in the Terrestrial Carbon Budget Caused by the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation  

Microsoft Academic Search

The terrestrial carbon dioxide (CO2) budget interacts with the Earth's climate system on diurnal to centennial and longer time scales, making it critical for climatic prediction and stabilization. Atmospheric observations and global syntheses of CO2 data indicate that the terrestrial biosphere is one the major sources of interannual variability, but the underlying mechanisms operating on different time-scales and the potential

Akihiko Ito

2011-01-01

373

Ozone generation by rock fracture: Earthquake early warning?  

SciTech Connect

We report the production of up to 10 ppm ozone during crushing and grinding of typical terrestrial crust rocks in air, O{sub 2} and CO{sub 2} at atmospheric pressure, but not in helium or nitrogen. Ozone is formed by exoelectrons emitted by high electric fields, resulting from charge separation during fracture. The results suggest that ground level ozone produced by rock fracture, besides its potential health hazard, can be used for early warning in earthquakes and other catastrophes, such as landslides or land shifts in excavation tunnels and underground mines.

Baragiola, Raul A.; Dukes, Catherine A.; Hedges, Dawn [Engineering Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2011-11-14

374

Terrestrial locomotion in arachnids.  

PubMed

In this review, we assess the current state of knowledge on terrestrial locomotion in Arachnida. Arachnids represent a single diverse (>100,000 species) clade containing well-defined subgroups (at both the order and subordinal levels) that vary morphologically around a basic body plan, yet exhibit highly disparate limb usage, running performance, and tarsal attachment mechanisms. Spiders (Araneae), scorpions (Scorpiones), and harvestmen (Opiliones) have received the most attention in the literature, while some orders have never been subject to rigorous mechanical characterization. Most well-characterized taxa move with gaits analogous to the alternating tripod gaits that characterize fast-moving Insecta - alternating tetrapods or alternating tripods (when one pair of legs is lifted from the ground for some other function). However, between taxa, there is considerable variation in the regularity of phasing between legs. Both large and small spiders appear to show a large amount of variation in the distribution of foot-ground contact, even between consecutive step-cycles of a single run. Mechanisms for attachment to vertical surfaces also vary, and may depend on tufts of adhesive hairs, fluid adhesives, silks, or a combination of these. We conclude that Arachnida, particularly with improvements in microelectronic force sensing technology, can serve as a powerful study system for understanding the kinematics, dynamics, and ecological correlates of sprawled-posture locomotion. PMID:22326455

Spagna, Joseph C; Peattie, Anne M

2012-02-08

375

Utility terrestrial biodiversity issues  

NASA Astrophysics Data System (ADS)

Results from a survey of power utility biologists indicate that terrestrial biodiversity is considered a major issue by only a few utilities; however, a majority believe it may be a future issue. Over half of the respondents indicated that their company is involved in some management for biodiversity, and nearly all feel that it should be a goal for resource management. Only a few utilities are funding biodiversity research, but a majority felt more research was needed. Generally, larger utilities with extensive land holdings had greater opportunities and resources for biodiversity management. Biodiversity will most likely be a concern with transmission rights-of-way construction and maintenance, endangered species issues and general land resource management, including mining reclamation and hydro relicensing commitments. Over half of the companies surveyed have established voluntary partnerships with management groups, and biodiversity is a goal in nearly all the joint projects. Endangered species management and protection, prevention of forest fragmentation, wetland protection, and habitat creation and protection are the most common partnerships involving utility companies. Common management practices and unique approaches are presented, along with details of the survey.

Breece, Gary Allen; Ward, Bobby J.

1996-11-01

376

Utility terrestrial biodiversity issues  

SciTech Connect

Results from a survey of power utility biologists indicate that terrestrial biodiversity is considered a major issued by only a few utilities; however, a majority believe it may be a future issue. Over half of the respondents indicated that their company is involved in some management for biodiversity, and nearly all feel that it should be a goal for resource management. Only a few utilities are funding biodiversity research, but a majority felt more research was needed. Generally, larger utilities with extensive land holdings had greater opportunities and resources for biodiversity management. Biodiversity will most likely be a concern with transmission rights-of-way construction and maintenance, endangered species issues and general land resource management, including mining reclamation and hydro relicensing commitments. Over half of the companies surveyed have established voluntary partnerships with management groups, and biodiversity is a goal in nearly all the joint projects. Endangered species management and protection, prevention of forest fragmentation, wetland protection, and habitat creation and protection are the most common partnerships involving utility companies. Common management practices and unique approaches are presented, along with details of the survey. 4 refs.

Breece, G.A. [Southern Company, Atlanta, GA (United States); Ward, B.J. [Carolina Power and Light Company, Raleigh, NC (United States)

1996-11-01

377

TERENO - A new Network of Terrestrial Observatories for Environmental Research  

NASA Astrophysics Data System (ADS)

In order to address the challenges of global change, interdisciplinary research in terrestrial environmental science is of great importance. Several environmental research networks have already been established in order to monitor, analyse and predict the impact of global change on different compartments and/or matter cycles of the environment. Typically these environmental research networks have focused on specific research questions, and compartments, such as CarboEurope, FLUXNET and ILTER. The infrastructure activity TERENO (Terrestrial Environmental Observatories) aims the establishment of a network of terrestrial observatories, defined as a system consisting of the subsurface environment, the land surface including the biosphere, the lower atmosphere and the anthroposphere. Hydrological units will be used as the basic scaling units in a hierarchy of evolving scales and structures ranging from the local scale to the regional scale for multi-disciplinary process studies. Although terrestrial systems are extremely complex, the terrestrial component in most process-based climate and biosphere models is typically represented in a very conceptual and often rudimentary way. Remedying this deficiency is therefore one of the most important challenges in environmental and terrestrial research, and we suggest that terrestrial observatories could be an important step towards a new quality in environmental and terrestrial research. For the first phase three terrestrial observatories in Germany have been identified: the Lower Rhine Basin, the metropolitan area Leipzig-Halle, and the Northern pre-Alps including the long-term research stations Hoeglwald and Scheyern. A fourth Observatory is planned in the German Lowland region. The concept of TERENO is illustrated by the Lower Rhine Basin. A monitoring concept for the Rur catchment -the largest catchment in the observatory- will be described that is capable of measuring the spatial-temporal variability of the main hydrological processes and interactions as well as the varying residence times of the terrestrial water stores. More detailed measurements and characterisation of smaller, focal catchments will be embedded within progressively larger catchments, allowing the critical evaluation and development of hydrologic scaling strategies. Specific attention will be given to install novel wireless sensor technology and hydrogeophysical measurement techniques combined with remote sensing methods (e.g. precipitation radars and airborne remote sensing platforms).

Bogena, H. R.; Haschberger, P.; Hajnsek, I.; Dietrich, P.; Priesack, E.; Munch, J.; Schmid, H.; Zacharias, S.; Vereecken, H.

2008-12-01

378

TERENO - A new Network of Terrestrial Observatories for Environmental Research  

NASA Astrophysics Data System (ADS)

In order to address the challenges of global change, interdisciplinary research in terrestrial environmental science is of great importance. Several environmental research networks have already been established in order to monitor, analyse and predict the impact of global change on different compartments and/or matter cycles of the environment. Typically these environmental research networks have focused on specific research questions, and compartments, such as CarboEurope, FLUXNET and ILTER. The infrastructure activity TERENO (Terrestrial Environmental Observatoria) aims the establishment of a network of terrestrial observatories, defined as a system consisting of the subsurface environment, the land surface including the biosphere, the lower atmosphere and the anthroposphere. Hydrological units will be used as the basic scaling units in a hierarchy of evolving scales and structures ranging from the local scale to the regional scale for multi-disciplinary process studies. Although terrestrial systems are extremely complex, the terrestrial component in most process-based climate and biosphere models is typically represented in a very conceptual and often rudimentary way. Remedying this deficiency is therefore one of the most important challenges in environmental and terrestrial research, and we suggest that terrestrial observatories could be an important step towards a new quality in environmental and terrestrial research. For the first phase three terrestrial observatories in Germany have been identified: the Lower Rhine Basin, the metropolitan area Leipzig-Halle, and the Northern pre-Alps including the long-term research stations Hoeglwald and Scheyern. The concept of TERENO is illustrated by the Lower Rhine Basin. A monitoring concept for the Rur catchment -the largest catchment in the observatory- will be described that is capable of measuring the spatial-temporal variability of the main hydrological processes and interactions as well as the varying residence times of the terrestrial water stores. More detailed measurements and characterisation of smaller, focal catchments will be embedded within progressively larger catchments, allowing the critical evaluation and development of hydrologic scaling strategies. Specific attention will be given to install novel wireless sensor technology and hydrogeophysical measurement techniques combined with remote sensing methods (e.g. precipitation radars and airborne remote sensing platforms). juelich.de/icg/icg-4/index.php?index=768

Priesack, E.; Bogena, H. R.; Haschberger, P.; Dietrich, P.; Schmid, H. P.; Schulz, K.; Vereecken, H.

2007-12-01

379

Bacteria Mediate Methylation of Iodine in Marine and Terrestrial Environments  

PubMed Central

Methyl iodide (CH3I) plays an important role in the natural iodine cycle and participates in atmospheric ozone destruction. However, the main source of this compound in nature is still unclear. Here we report that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 ?M). Of the strains tested, Rhizobium sp. strain MRCD 19 was chosen for further analysis, and it was found that the cell extract catalyzed the methylation of iodide with S-adenosyl-l-methionine as the methyl donor. These results strongly indicate that bacteria contribute to iodine transfer from the terrestrial and marine ecosystems into the atmosphere.

Amachi, Seigo; Kamagata, Yoichi; Kanagawa, Takahiro; Muramatsu, Yasuyuki

2001-01-01

380

Eukaryote-dominated Microbial Communities That Build Iron-Stromatolites in Acid Mine Drainage, Western Indiana: An Analog for Proterozoic Banded Iron Formations and Oxygenation of the Early Atmosphere?  

NASA Astrophysics Data System (ADS)

Eukaryote-dominated microbial communities build iron-rich stromatolites in acid mine drainage at several reclaimed coal mine sites in western Indiana, which can serve as an analog for Proterozoic iron-rich deposits and the oxygenation of the early atmosphere.

Hasiotis, S. T.; Brake, S. S.; Dannelly, H. K.; Duncan, A.

2001-03-01

381

Glaciopanspermia: Seeding the terrestrial planets with life?  

NASA Astrophysics Data System (ADS)

The question whether life originated on Earth or elsewhere in the solar system has no obvious answer, since Earth was sterilized by the Moon-forming impact and possibly also during the LHB, about 700 Ma after the formation of the solar system. Seeding by lithopanspermia has to be considered. Possible sources of life include Earth itself, Mars, Venus (if it had a more benign climate than today) and icy bodies of the solar system. The first step of lithopanspermia is the ejection of fragments of the surface into space, which requires achieving at least escape velocity. As the velocity distribution of impact ejecta falls off steeply, attention is drawn to bodies with lower escape velocities. Ceres has had, or still has, an ocean more than 100 km deep, with hydrothermal activity at its rocky core. The possible presence of life, its relative closeness to the terrestrial planets and Ceres' low escape velocity of 510 m/s suggest that Ceres could well be a parent body for life in the solar system.Icy impact ejecta - hence glaciopanspermia - from Ceres will be subject to evaporation of volatiles. Spores may be loosened by evaporation and enter the atmospheres of the terrestrial planets as micrometeorites.The seeding of the terrestrial planets from Ceres would result in (1) detection of life in the crustal layers of Ceres; (2) a commonality of Cerean life with Terran and possible Martian and Venusian life and (3) biomarkers of Cerean life, which might be found in the ice at the Moon's poles and on the surface of other main belt asteroids.

Houtkooper, Joop M.

2011-08-01

382

GEOLogic: Terrestrial and Jovian Planets  

NSDL National Science Digital Library

In this two-part example, students are given clues about properties about the terrestrial and Jovian planets respectively and asked to match up the planet with the correct equatorial radius, mean orbital velocity, and period of rotation.

Guertin, Laura

383

Contaminant Exposure in Terrestrial Vertebrates  

EPA Science Inventory

Manuscript is a critical review of the state of the science for quantifying exposures of terrestrial wildlife species to chemical contamination. It describes the unique aspects of birds, mammals, reptiles, amphibians and threatened and endangered species. Fate and transport of ...

384

USING TERRESTRIAL PLANTS IN BIOMONITORING  

EPA Science Inventory

Terrestrial plants have been used as monitors of environmental pollutants since at least the beginning of this century & have recently received attention in response to the need for ecological assessments at hazardous waste sites & monitoring pesticide damage to nontarget plants....

385

The upper atmosphere. Data analysis and interpretation.  

NASA Astrophysics Data System (ADS)

The following topics were dealt with: thermosphere, mesosphere, ionosphere, tides, gravity waves, turbulence, atmospheric chemistry, pollution, humidity, radiowave propagation, acoustic methods, remote sensing, electromagnetic waves, investigation methods, hydrodynamics, plasma measurements, refractive index, atmospheric radiation, reference models, ion density, electron density, collision frequencies, ionospheric disturbances, ion precipitation, ozone hole, mesospheric clouds, nightglow, aurorae, solar-terrestrial relations, and data analysis.

Dieminger, W.; Hartmann, G. K.; Leitinger, R.

386

Carbon Sequestration in Terrestrial Ecosystems  

Microsoft Academic Search

CSiTE, the Department of Energy's research consortium performs fundamental research in support of new methods to enhance carbon sequestration in terrestrial ecosystems in an environmentally acceptable manner. The goal of CSiTE is to discover and characterize links between critical pathways and mechanisms across scales from the molecular to the landscape for creating larger, longer-lasting carbon pools in terrestrial ecosystems. This

G. K. Jacobs; W. M. Post; J. D. Jastrow; R. C. Izaurralde

2002-01-01

387

Bio-char Sequestration in Terrestrial Ecosystems – A Review  

Microsoft Academic Search

The application of bio-char (charcoal or biomass-derived black carbon (C)) to soil is proposed as a novel approach to establish\\u000a a significant, long-term, sink for atmospheric carbon dioxide in terrestrial ecosystems. Apart from positive effects in both\\u000a reducing emissions and increasing the sequestration of greenhouse gases, the production of bio-char and its application to\\u000a soil will deliver immediate benefits through

Johannes Lehmann; John Gaunt; Marco Rondon

2006-01-01

388

Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes  

Microsoft Academic Search

Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by

M. Marisaldi; C. Labanti; F. Fuschino; A. Bulgarelli; M. Trifoglio; G. Di Cocco; F. Gianotti; A. Argan; G. De Paris; A. Trois; E. Del Monte; E. Costa; G. Di Persio; I. Donnarumma; Y. Evangelista; M. Feroci; F. Lazzarotto; L. Pacciani; A. Rubini; S. Sabatini

2010-01-01

389

Terrestrial Planet Finder Coronagraph (TPF-C) Flight Baseline Concept  

Microsoft Academic Search

The Terrestrial Planet Finder Coronagraph (TPF-C) mission presented here is an existence proof for a flagship-class internal coronagraph space mission capable of detecting and characterizing Earth-like planets and planetary systems at visible wavelengths around nearby stars, using an existing launch vehicle. TPF-C will use spectroscopy to measure key properties of exoplanets including the presence of atmospheric water or oxygen, powerful

Marie Levine; D. Lisman; S. Shaklan; J. Kasting; W. Traub; J. Alexander; R. Angel; C. Blaurock; M. Brown; R. Brown; C. Burrows; M. Clampin; E. Cohen; L. Dewell; P. Dumont; R. Egerman; H. Ferguson; V. Ford; J. Greene; O. Guyon; H. Hammel; S. Heap; T. Ho; S. Horner; S. Hunyadi; S. Irish; C. Jackson; J. Kasdin; A. Kissil; M. Krim; M. Kuchner; E. Kwack; C. Lillie; D. Lin; A. Liu; L. Marchen; M. Marley; V. Meadows; G. Mosier; P. Mouroulis; M. Noecker; R. Ohl; B. Oppenheimer; J. Pitman; S. Ridgway; E. Sabatke; S. Seager; M. Shao; A. Smith; R. Soummer; K. Stapelfeldt; D. Tenerell; J. Trauger; R. Vanderbei

2009-01-01

390

Source mechanisms of terrestrial gamma-ray flashes  

Microsoft Academic Search

The source of terrestrial gamma-ray flashes (TGFs) has remained a mystery since their discovery in 1994. Recent Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) observations show that these intense bursts of MeV gamma rays likely originate much deeper in the atmosphere than previously inferred from Burst and Transient Source Experiment (BATSE) data, with the source altitude <21 km. Using existing

J. R. Dwyer

2008-01-01

391

Studies of the terrestrial O{sub 2} and carbon cycles in sand dune gases and in biosphere 2  

SciTech Connect

Molecular oxygen in the atmosphere is coupled tightly to the terrestrial carbon cycle by the processes of photosynthesis, respiration, and bur