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1

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

2

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

NASA Technical Reports Server (NTRS)

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

Repin, Robert O.

1989-01-01

3

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

4

The development of early terrestrial ecosystems  

E-print Network

of subaerial diagenesis in the 1.2-b.y. Mescal Limestone, central Arizona: implications for the timing and development of a terrestrial plant cover. Geological Society of America, Bulletin 96,737-745. THE DEVELOPMENT OF EARLY TERRESTRIAL ECOSYSTEMS 355 Bell..., P.R. (1989). 'Heterospory' in Sphagnum: fifty years of error. Journal of Bryology 15, 679-682. Berkner, L.V. & Marshall, L.C. (1965). On the origin and rise of oxygen concentration in the Earth's atmosphere. Journal of Atmospheric Science 22...

Selden, Paul A.; Edwards, Dianne

1993-01-01

5

Impact erosion of terrestrial planetary atmospheres  

NASA Technical Reports Server (NTRS)

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

Ahrens, Thomas J.

1992-01-01

6

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

7

Linkages between terrestrial ecosystems and the atmosphere  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

8

Atmospheric evolution of the terrestrial planets  

SciTech Connect

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

Hunten, D.M. (Univ. of Arizona, Tucson (United States))

1993-02-12

9

Atmospheric Circulation of Terrestrial Exoplanets Adam P. Showman  

E-print Network

Atmospheric Circulation of Terrestrial Exoplanets Adam P. Showman University of Arizona Robin D of terrestrial exoplanets, and discuss the interaction of their circulation with the hydrological cycle and global-scale climate feedbacks. Terrestrial exoplanets occupy a wide range of physical and dynamical

10

Planetary Atmospheres Earth and the Other Terrestrial Worlds  

E-print Network

per sq. inch ­ 1 bar Where does an atmosphere end? · There is no clear upper boundary · Most of Earth1 Chapter 10 Planetary Atmospheres Earth and the Other Terrestrial Worlds What is an atmosphere? An atmosphere is a layer of gas that surrounds a world Earth s Atmosphere · About 10 km thick · Consists mostly

Crenshaw, Michael

11

Rare earth element systematics of the chemically precipitated component in Early Precambrian iron formations and the evolution of the terrestrial atmosphere-hydrosphere-lithosphere system  

Microsoft Academic Search

Regardless of age and metamorphic grade, the chemically precipitated component in Early Precambrian (greater than 2.3 Ga) iron formations (IFs) shows (Sm\\/Yb)CN less than 1 and (Eu\\/Sm)SN greater than 1, reflecting the corresponding ratios of contemporaneous sea water. This REE signature reveals that the REE distribution in Early Precambrian IFs must be explained by mixing between a marine bottom and

Michael Bau; Peter Moeller

1993-01-01

12

Rare earth element systematics of the chemically precipitated component in Early Precambrian iron formations and the evolution of the terrestrial atmosphere-hydrosphere-lithosphere system  

SciTech Connect

The chemically precipitated component in Early Precambrian (> 2.3 Ga) iron formations (IFs) displays (Sm/Yb)[sub CN] < 1 and (Eu/Sm)[sub SN] > 1 which reflects the corresponding ratios of contemporaneous seawater. In conjunction with [epsilon][sub Nd-IF] > [epsilon][sub Nd-shale] this rare earth element (REE) signature reveals that the REE distribution in Early Precambrian IFs must be explained by mixing between a marine bottom and a surface water component, and that the REEs (and by analogy the Fe) cannot be derived from weathering of a continental source. Mixing calculations reveal that (Sm/Yb)[sub CN] in Early Precambrian marine surface waters was significantly lower than it is today. To explain this difference, two mechanisms are discussed on the basis of higher P[sub CO[sub 2

Bau, M.; Moeller, P. (Hahn-Meitner-Institut, Berlin (Germany))

1993-05-01

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

Terrestrial nitrous oxide cycles and atmospheric effects  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

15

Investigating the Effects of Meteor Showers on Terrestrial Atmospheres  

NASA Astrophysics Data System (ADS)

Meteor showers can change the atmospheric composition and ionization of the terrestrial planets, but their influence on the thermal state and dynamics of the middle atmospheres have not been studied in depth. The progress in Earth observation and atmospheric modelling of the past decades allows us to revisit the question of atmospheric heating by meteor showers. As an initial test, we performed a simulation with the Whole Atmosphere Community Climate model (WACCM). We assumed that the kinetic energy of the meteor shower heats up the mesosphere by 10 K at the start of the simulation. This perturbation caused significant differences in the evolution of the wind and temperature distribution of the lower and middle atmosphere even after 31 days. Particularly a Sudden Stratospheric Warming was suppressed by the change of the initial conditions in the mesosphere.

Proedrou, E.; Hocke, K.; Kämpfer, N.; Wurz, P.; Lammer, H.

2013-09-01

16

Space, Atmospheric, and Terrestrial Radiation Environments  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

17

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

NASA Astrophysics Data System (ADS)

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

Wordsworth, R.

2013-12-01

18

Sulphur cycling between terrestrial agroecosystem and atmosphere.  

PubMed

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

Zgorelec, Zeljka; Pehnec, Gordana; Baši?, Ferdo; Kisi?, Ivica; Mesi?, Milan; Zužul, Silva; Juriši?, Aleksandra; Sestak, Ivana; Va?i?, Vladimira; Ca?kovi?, Mirjana

2012-09-01

19

On the early global melting of the terrestrial planets  

NASA Technical Reports Server (NTRS)

Attention is given to all the mechanisms currently known which might have been responsible for the melting of the moon. A comparison is conducted of the terrestrial planets and the moon, taking into account the conditions in the early solar system as a function of time. The assumption is made that the terrestrial planets and the moon all reached sizes comparable to their present sizes at the same time, so that the same heating mechanisms were operating on all of the bodies when their early crusts were formed. A chronology of the early solar system is established in order to evaluate the time periods during which each of the mechanisms might have been active. If the moon and planets formed within 2,000,000 years after the formation of the protosun, the conclusion appears inescapable that all of the terrestrial planets melted.

Hostetler, C. J.; Drake, M. J.

1980-01-01

20

Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

21

Abiotic oxygen-dominated atmospheres on terrestrial habitable zone planets  

E-print Network

Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is an atmosphere where oxygen is a major constituent. Here we show that lifeless habitable zone terrestrial planets around any star type may develop oxygen-dominated atmospheres as a result of water photolysis, because the cold trap mechanism that protects H2O on Earth is ineffective when the atmospheric inventory of non-condensing gases (e.g., N2, Ar) is low. Hence the spectral features of O2 and O3 alone cannot be regarded as robust signs of extraterrestrial life.

Wordsworth, Robin

2014-01-01

22

Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere  

NASA Technical Reports Server (NTRS)

We have investigated the impact of hot metastable oxygen atoms on the product yields and rate coefficients of atmospheric reactions involving O( (sup 1)D). The contribution of the metastable oxygen atoms to the thermal balance of the terrestrial atmosphere between 50 and 200 km has been determined. We found that the presence of hot O((sup l)D) atoms in the mesosphere and lower thermosphere significantly increases the production rate of the rotationally-vibrationally excited NO molecules. The computed yield of the NO molecules in N2O+ O((sup 1)D) atmospheric collisions, involving non-Maxwellian distributions of the metastable oxygen atoms, is more than two times larger than the NO-yield at a thermal equilibrium. The calculated non-equilibrium rate and yield functions are important for ozone and nitrous oxide modeling in the stratosphere, mesosphere and lower thermosphere.

Kharchenko, Vasili

2004-01-01

23

Energetic Metastable Oxygen and Nitrogen Atoms in the Terrestrial Atmosphere  

NASA Technical Reports Server (NTRS)

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

Kharchenko, Vasili; Dalgarno, A.

2005-01-01

24

Transport of Ionizing Radiation in Terrestrial-like Exoplanet Atmospheres  

E-print Network

(Abridged) Propagation of ionizing radiation, as from parent star flares, supernovae, or gamma-ray bursts, is studied for a suite of simple model atmospheres of terrestrial-like exoplanets covering a large range of column densities and incident photon energies. We developed a Monte Carlo code to treat the Compton scattering and photoabsorption. Atmospheres thinner than about 100 g cm^-2 transmit a significant fraction of incident gamma-rays, but even the thinnest atmospheres are essentially opaque to X-rays below about 30 keV. For thicker atmospheres, the incident ionizing radiation is efficiently blocked, but most of the incident energy is redistributed via secondary electron excitation into diffuse UV and visible aurora-like emission, increasing the atmospheric transmission by many orders of magnitude; in some cases the transmission can be up to 10%, depending on the intervening UV opacity. For Earth, between 2 x 10^-3 and 4 x 10^-2 of the incident flux reaches the ground in the 200-320 nm range, depending ...

Smith, D S; Wheeler, J C; Smith, David S.; Scalo, John

2003-01-01

25

Early Martian environments - The antarctic and other terrestrial analogs  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

26

Coupling Terrestrial and Atmospheric Water Dynamics to Improve Prediction in a Changing Environment  

E-print Network

Fluxes across the land surface directly influence predictions of ecological processes, atmospheric dynamics, and terrestrial hydrology. However, many simplifications are made in numerical models when considering ...

Lyon, Steve W.; Dominguez, Francina; Gochis, David J.; Brunsell, Nathaniel A.; Castro, Christopher; Chow, Fotini K.; Fan, Ying; Fuka, Daniel; Hong, Yang; Kucera, Paul A.; Nesbitt, Stephen W.; Salzmann, Nadine; Schmidli, Juerg; Snyder, Peter K.; Teuling, Adriaam J.; Twine, Tracy E.; Levis, Samuel; Lundquist, Jessica D.; Salvucci, Guido D.; Sealy, Andrea M.; Walter, M. Todd

2008-09-01

27

Atmospheric Escape and Climate Evolution of Terrestrial Planets  

NASA Astrophysics Data System (ADS)

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

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

28

Are terrestrial mosses good biomonitors of atmospheric deposition of Mn?  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

29

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

30

Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters  

E-print Network

The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters suggests that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone---including transitions to Snowball-like states and runaway-greenhouse feedbacks---depend on the equator-to-pole temperature differences, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass,...

Kaspi, Yohai

2014-01-01

31

Origin of the atmosphere and hydrosphere of the terrestrial planets  

NASA Technical Reports Server (NTRS)

An early thermal evolution of a planet growing by planetesimal impacts was studied. An evolution of an impact induced atmosphere was considered. It is known that the surface of a growing planet is heated due to the blanketing effect of the atmosphere and exceeds the melting temperature, which means that the surface of a growing planet was entirely covered by a magma ocean. The amount of water in a proto-atmosphere is influenced by the formation of a magma ocean. It is suggested the solubility of water in silicate melt controls the water content in a proto-atmsphere. It is noted that irrespective of difference in initial water content of planetesimals the final water content in the atmosphere becomes almost constant and is about 10 to the 21st power kg which is almost identical with the present amount of the ocean. It is also shown that the water in a proto-atmosphere can be liquid for the Earth and becomes to be an ocean but this does not happen on Venus.

Matsui, T.; Abe, Y.

1985-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

33

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

E-print Network

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 red...

Hu, Renyu; Bains, William

2012-01-01

34

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

NASA Astrophysics Data System (ADS)

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

Kaspi, Yohai; Showman, Adam P.

2014-11-01

35

Atmospheric photochemistry, surface features, and potential biosignature gases of terrestrial exoplanets .  

E-print Network

??The endeavor to characterize terrestrial exoplanets warrants the study of chemistry in their atmospheres. Here I present a comprehensive one-dimensional photochemistry-thermochemistry model developed from the… (more)

Hu, Renyu, Ph. D. Massachusetts Institute of Technology

2013-01-01

36

Atmospheric photochemistry, surface features, and potential biosignature gases of terrestrial exoplanets  

E-print Network

The endeavor to characterize terrestrial exoplanets warrants the study of chemistry in their atmospheres. Here I present a comprehensive one-dimensional photochemistry-thermochemistry model developed from the ground up for ...

Hu, Renyu, Ph. D. Massachusetts Institute of Technology

2013-01-01

37

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

E-print Network

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 ...

Hu, Renyu

38

Photochemistry of methane in the earth's early atmosphere  

NASA Astrophysics Data System (ADS)

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 atmosphere in a geologically short period of time after the segregation of the core. Abiotic sources of methane are not likely to have been large enough to sustain CH4 mixing ratios as high as 10 to the -6th, the threshold for a possible methane greenhouse, with a CO-rich atmosphere being a possible exception. After the origin of life an increasing biogenic source of methane may have driven CH4 mixing ratios well above 10 to the 6th. The rise of atmospheric oxygen in the early Proterozoic may have led to a more rapid photochemical destruction of methane, lowering the mixing ratio to its present value.

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

39

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

40

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

USGS Publications Warehouse

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

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

2002-01-01

41

On the (anticipated) diversity of terrestrial planet atmospheres  

NASA Astrophysics Data System (ADS)

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

Leconte, Jérémy; Forget, François; Lammer, Helmut

2014-07-01

42

Earth's atmosphere – Hadean to early Proterozoic  

Microsoft Academic Search

The chemistry of Earth's atmosphere during its first 2–2.5Ga bears on several branches of geoscience including the origin of prebiotic molecules and life itself, early surface processes, the “faint young sun” problem, carbon isotope systematics, and the transition to an oxidized surface. The geologic record, as sparse as it is for this era, presents several difficulties for attempts to model

George H. Shaw

2008-01-01

43

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

44

Detectability of biosignature gases in the atmospheres of terrestrial exoplanets  

E-print Network

Biosignature gases in the atmosphere of an exoplanet provide a means by which we can deduce the possible existence of life on that planet. As the list of possible biosignature gases is ever growing, the need to determine ...

Messenger, Stephen Joseph

2013-01-01

45

Historical space psychology: Early terrestrial explorations as Mars analogues  

Microsoft Academic Search

The simulation and analogue environments used by psychologists to circumvent the difficulties of conducting research in space lack many of the unique characteristics of future explorations, especially the mission to Mars. This paper suggests that appropriate additional analogues would be the multi-year maritime and terrestrial explorations that mapped the surface of the Earth in previous centuries. These, like Mars, often

Peter Suedfeld

2010-01-01

46

Atmospheric Nitrogen Deposition and Habitat Alteration in Terrestrial and Aquatic  

E-print Network

California have emphasized the strong linkage between levels of air pollution-related atmospheric nitrogen (N Meixner2 Key words: air pollution, amphibians, montane forests, N-enrichment, nitrate, runoff Extended in Southern California: Implications for Threatened and Endangered Species1 Mark Fenn, Mark Poth, and Thomas

Standiford, Richard B.

47

Interactions in Terrestrial Ecosystems in Response to Rising Atmospheric Carbon Dioxide  

Microsoft Academic Search

Interactions involving carbon (C) and nitrogen (N) likely modu- late terrestrial ecosystem responses to elevated atmospheric carbon dioxide (CO2) levels at scales from the leaf to the globe and from the second to the century. In particular, response to elevated CO2 may generally be smaller at low relative to high soil N supply and, in turn, elevated CO2 may influence

Peter B. Reich; Bruce A. Hungate; Yiqi Luo

48

Stability of ammonia in the primitive terrestrial atmosphere  

NASA Astrophysics Data System (ADS)

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

Kasting, J. F.

1982-04-01

49

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

PubMed

The release of carbon dioxide from fossil-fuel combustion and land-use change has caused a significant perturbation in the natural cycling of carbon between land, atmosphere and oceans. Understanding and managing the effects of this disruption on atmospheric composition and global climate are likely to be amongst the most pressing issues of the 21st century. However, the present-day carbon cycle is still poorly understood. One remarkable feature is that an increasing amount of atmospheric carbon dioxide appears to be being absorbed by terrestrial vegetation. I review the recent evidence for the magnitude and spatial distribution of this 'terrestrial carbon sink', drawing on current research on the global atmospheric distribution and transport of carbon dioxide, oxygen and their isotopes; direct measurement of CO(2) fluxes above various biomes; and inventories of forest biomass and composition. I review the likely causes of these carbon sinks and sources and their implications for the ecology and stability of these biomes. Finally, I examine prospects and key issues over coming decades. Within a few years, satellite measurements of atmospheric CO(2) and forest biomass, coupled with 'real-time' biosphere-atmosphere models, will revolutionize our understanding of the terrestrial carbon cycle. Controlling deforestation and managing forests has the potential to play a significant but limited part in reaching the goal of stabilizing atmospheric CO(2) concentrations. However, there are likely to be limits to the amount of carbon storage possible in natural vegetation, and, in the long term, terrestrial carbon storage may be unstable, with the potential to accelerate rather than brake global warming. PMID:12626274

Malhi, Yadvinder

2002-12-15

50

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

51

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

NASA Astrophysics Data System (ADS)

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

Stoekl, Alexander; Dorfi, Ernst

2014-05-01

52

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

PubMed Central

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

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

2013-01-01

53

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

PubMed Central

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

Kürschner, Wolfram M.; Kva?ek, Zlatko; Dilcher, David L.

2008-01-01

54

Nitrogen Fixation on Early Mars and Other Terrestrial Planets: Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate  

NASA Astrophysics Data System (ADS)

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 NO2. 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 NO2 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 NO2 reaction with ice, adsorbed water, etc.).

Summers, David P.; Khare, Bishun

2007-05-01

55

An experimental approach to production of peptide-like compounds in the early terrestrial planets  

NASA Astrophysics Data System (ADS)

A mixture of six DL-amino acids in prebiotic proportions were immersed in heavy mineral oil, warmed up to 240°C and exposed to the action of spark discharges on a mixture of H 2O and CO 2 gases. Water soluble products were analyzed by Fourier transformed infrared spectroscopy (FTIR) showing yields of peptide-like compounds characterized by amidine linkages and other molecules consisting of aromatic and non-aromatic alcohols and nitrogenous aromatics. Non-soluble products analyzed by scanning electron microscopy (SEM) revealed the presence of a material comparable to tholins whereas the products soluble in water showed the presence of an amphiphilic component. The recovered amounts and the FTIR spectra corresponding to heavy mineral oil exposed to simulated experimental conditions including UVC-radiations, clearly show no difference relative to initial sample indicating that the decomposition rate of these molecules should be very slow at the time. Therefore, we consider plausible that alkane environments ? n-C 18 occurring on the early terrestrial planets could offer several advantages for the synthesis and survival of nitrogenous molecules, particularly towards the end or after the age of the large impacts, such as protection against oxidizing atmospheres, high temperatures generated by greenhouse effects or shock waves and protection against decomposition effects caused by high UVC-radiations, corona discharges and lightning. Currently, these facts could be happening in other regions of our solar system and in extrasolar planets allowing the formation and accumulation of complex nitrogenous molecules.

Marcano, Vicente; Benitez, Pedro; Palacios-Pru, Ernesto

2001-05-01

56

Greening the terrestrial biosphere: simulated feedbacks on atmospheric heat and energy circulation  

Microsoft Academic Search

Much research focuses on how the terrestrial biosphere influences climate through changes in surface albedo (reflectivity),\\u000a stomatal conductance and leaf area index (LAI). By using a fully-coupled GCM (HadCM3LC), our research objective was to induce\\u000a an increase in the growth of global vegetation to isolate the effect of increased LAI on atmospheric exchange of heat and\\u000a moisture. Our Control simulation

S. A. Cowling; C. D. Jones; P. M. Cox

2009-01-01

57

Atmospheric circulation modeling of super Earths and terrestrial extrasolar planets using the SPARC/MITgcm  

NASA Astrophysics Data System (ADS)

The field of exoplanets continues to be a booming field of research in astronomy and planetary science, with numerous ground-based (e.g., SuperWASP, HARPS-N and S) and space-based surveys (e.g., Kepler) that detect and characterize planets ranging from hot Jupiters, Jovian-sized planets orbiting less than 0.1 AU from their star, to super Earths and terrestrial exoplanets, planets that have masses equal to or less than 10 times that of Earth with a range of orbital distances. Atmospheric circulation modeling plays an important role in the characterization of these planets, helping to constrain observations that probe their atmospheres. These models have proven successful in understanding observations of transiting exoplanets (when the planet passes in front of the star along our line of sight) particularly when the planet is passing through secondary eclipse (when the planet's dayside is visible). In modeling super Earths and terrestrial exoplanets, we must consider 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 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 present results from two studies, the first focusing on the circulation of GJ 1214b, a super-Earth detected by the MEarth ground-based survey, and a second study which explores the circulation of terrestrial exoplanets orbiting M-dwarfs.

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

2013-12-01

58

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

59

Historical space psychology: Early terrestrial explorations as Mars analogues  

NASA Astrophysics Data System (ADS)

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

Suedfeld, Peter

2010-03-01

60

Static opaque chamber-based technique for determination of net exchange of CO2 between terrestrial ecosystem and atmosphere  

Microsoft Academic Search

Terrestrial carbon cycling is one of the hotspots in global change issues. In this paper, we presented the ra- tionale for determination of net exchange of CO2 between terrestrial and the atmosphere (NEE) and the methods for measuring several relevant components. Three key processes for determination of NEE were addressed, including the separation of shoot autotrophic respiration from total CO2

Jianwen ZOU; Yao Huang; Xunhua Zheng; Yuesi Wang; Yuquan Chen

2004-01-01

61

Net primary production of terrestrial ecosystems in China and its equilibrium response to changes in climate and atmospheric CO? concentration  

E-print Network

The Terrestrial Ecosystem Model (TEM, version 4.0) was used to estimate net primary production (NPP) in China for contemporary climate and NPP responses to elevated CO? and climate changes projected by three atmospheric ...

Xiao, Xiangming.; Melillo, Jerry M.; Kicklighter, David W.; Pan, Yude.; McGuire, A. David.; Helfrich III, J.V.K.

62

Reconciling atmospheric temperatures in the early Archean  

NASA Astrophysics Data System (ADS)

Average surface temperatures of Earth in the Archean remain unresolved despite decades of diverse approaches to the problem. As in the present, early Earth climates were complex systems dependent on many variables. With few constraints on such variables, climate models must be relatively simplistic, and consider only one or two factors that drive Archean climate (e.g. a fainter young sun, a low albedo, the extent and effect of cloud cover, or the presence and abundance of a wide array of greenhouse and icehouse gasses). Compounded on the limitations of modeling is the sparse and often ambiguous Archean rock record. The goal of this study is to compile and reconcile Archean geologic and geochemical features that are in some way controlled by surface temperature and/or atmospheric composition, so that at the very least paleoclimate models can be checked by physical limits. Data used to this end include the oxygen isotope record of chemical sediments and ancient ocean crust, chemical equilibria amongst primary phases in banded iron formations (BIFs), sedimentary features indicative of temperate or glacial environments, and paleosol indicators of atmospheric CO2. Further, we explore the extent to which hydrogen isotopes contribute to the geologic record as a signal for glaciations, continental growth and atmospheric methane levels. Oceanic serpentinites and subduction-related volcanic and hydrothermal environments obtain their hydrogen isotope signature from seawater, and thus may be used to calculate secular variation in ?DSEAWATER which may fluctuate significantly due to hydrogen escape, continental growth and large-scale glaciation events. Further, ancient records of low-?D meteoric fluids signal both cooler temperatures and the emergence of large continents (increasing the effects of continental weathering on climate). Selective alteration of ?D in Isua rocks to values of -130 to -100‰ post-dates ca. 3.55Ga Ameralik dikes, but may be associated with a poorly defined 2.6-2.8Ga metamorphic event that is coincident with the amalgamation of the "Kenorland supercontinent."

Pope, E. C.; Rosing, M.; Bird, D. K.; Albarede, F.

2012-12-01

63

Terrestrial ecosystems response to future changes in climate and atmospheric CO2 concentration  

NASA Astrophysics Data System (ADS)

The response of the terrestrial carbon cycle to future changes in climate and atmospheric CO2 is assessed by analyzing simulations, for the 2006-2100 period, made with the second generation Canadian Earth system model (CanESM2) for the RCP 2.6, RCP 4.5 and RCP 8.5 climate change scenarios. Our interest is in the extent to which global terrestrial carbon pools and sinks, in particular those of the Amazonian region, are vulnerable to the adverse effects of climate change. CanESM2 results indicate that land remains an overall sink of atmospheric carbon for the 2006-2100 period. The net carbon uptake by land in response to changes in climate and atmospheric CO2 is close to 20, 80 and 140 Pg C for the RCP 2.6, 4.5 and 8.5 scenarios, respectively. The latitudinal structure of future atmosphere-land CO2 flux remains similar to that observed for the historical period with northern mid- to high-latitude regions gaining carbon from the atmosphere while the tropics remain either carbon neutral or a modest source of atmospheric carbon depending on scenario. These changes occur in conjunction with simulated precipitation and soil moisture increases over northern mid- and high-latitude land regions and precipitation and soil moisture decreases over the South American continent in all scenarios. Compared to other regions of the globe, which are either carbon sinks or near neutral, the Amazonian region is simulated to be a net source of carbon during the 21st century. Moreover, and unexpectedly, the rate of carbon loss to the atmosphere from the Amazonian region is largely independent of the differences between the three scenarios considered.

Arora, V. K.; Boer, G. J.

2014-03-01

64

Terrestrial ecosystems response to future changes in climate and atmospheric CO2 concentration  

NASA Astrophysics Data System (ADS)

The response of the terrestrial carbon cycle to future changes in climate and atmospheric CO2 is assessed by analysing simulation results for the 2006-2100 period made with the second generation Canadian Earth system model (CanESM2) for the RCP 2.6, RCP 4.5 and RCP 8.5 climate change scenarios. Our interest is in the extent to which global terrestrial carbon pools and sinks, in particular those of the Amazonian region, are vulnerable to the adverse effects of climate change. CanESM2 results indicate that land remains an overall sink of atmospheric carbon for the 2006-2100 period. The net carbon uptake by land in response to changes in climate and atmospheric CO2 is close to 20, 80 and 140 Pg C for the RCP 2.6, 4.5 and 8.5 scenarios, respectively. The latitudinal structure of future atmosphere-land CO2 flux remains similar to that observed for the historical period with northern mid- to high-latitude regions gaining carbon from the atmosphere while the tropics remain either carbon neutral or a modest source of atmospheric carbon depending on scenario. These changes occur in conjunction with simulated precipitation and soil moisture increases over northern mid- and high-latitude land regions and precipitation and soil moisture decreases over the South American continent in all scenarios. Compared to other regions of the globe, which are either carbon sinks or near neutral, the Amazonian region is simulated to be a net source of carbon during the 21st century. Moreover, and unexpectedly, the rate of carbon loss to the atmosphere from the Amazonian region is largely independent of the differences between the three scenarios considered.

Arora, V. K.; Boer, G. J.

2014-08-01

65

Optimization of a prognostic biosphere model in atmospheric CO2 variability and terrestrial biomass  

NASA Astrophysics Data System (ADS)

This study investigated the capacity of a prognostic biosphere model to simulate global vegetation carbon dynamics and the variability in atmospheric CO2 concentrations under the current environmental conditions. Global data sets of atmospheric CO2 concentrations and terrestrial vegetation compositions of the aboveground biomass and net primary productivity (NPP) were assimilated into the biosphere model using an inverse modeling method combined with an atmospheric transport model. In this process, the optimal physiological parameters of the biosphere model were estimated by minimizing the misfit between the observed and modeled values, and acceptable parameters with various values were generated among the biome types. The model with the optimized parameters corresponded to the observed seasonal variations in the CO2 concentration, especially in the Northern Hemisphere where there are abundant observation stations, although the annual amplitudes were overestimated at a few stations. In simulating the mean annual aboveground biomass and NPP, the model also produced moderate estimates of the mean magnitudes and probability distributions for each biome. However, the model worked less efficiently in simulating the terrestrial vegetation compositions in some grids. These misfits suggest that some additional information about the disturbance and seasonal variability of the physiological parameters is required to improve the performance of the simulation model.

Saito, M.; Ito, A.; Maksyutov, S.

2013-08-01

66

The origins and early histories of planetary atmospheres  

Microsoft Academic Search

Ancient dry river beds detected on Mars by the Viking spacecraft suggest that the early Martian atmosphere may have been much more massive than at present. Degassing of a late-accreting, volatile-rich veneer may account for the primitive atmosphere of both Mars and earth. The primitive earth atmosphere could have produced a greenhouse effect sufficient to maintain temperatures above 273 K

T. Owen

1979-01-01

67

Flux of water vapor in the terrestrial stratosphere and in the Martian atmosphere  

NASA Technical Reports Server (NTRS)

A summary of the terrestrial satellite data is presented. The observations indicate that at equatorial latitudes, relatively dry air is introduced at the tropopause and carried to the upper stratosphere. At that altitude, any methane present in the ascending air mass is oxidized photochemically into water vapor. This vapor is eventually transported to high latitudes, where it is carried to the lower stratosphere by the descending leg of the diabatic circulation. The Pressure Modulator Infrared Radiometer instrument aboard the Mars Observer should provide a comparable picture of vapor transport in the martian atmosphere.

Leovy, Conway; Hitchman, Matthew; Mccleese, Daniel J.

1988-01-01

68

Chernobyl radionuclides in the environment: Tracers for the tight coupling of atmospheric, terrestrial, and aquatic geochemical processes  

Microsoft Academic Search

Observations of the temporal trend in concentrations of Chernobyl radionuclides in atmospheric, terrestrial, and aquatic reservoirs near Duebendorf (Zurich) aided in quantifying fluxes and transfer velocities from one reservoir to another. Radionuclide dry and wet deposition rates and velocities from the atmosphere, washout from the catchment basins into surface waters, and deposition rates and mechanisms in lakes were determined. The

P. H. Santschl; Silvia Bollhalder; Klaus Farrenkothen; Alfred Lueck; Stefan Zingg; Michael Sturm

1988-01-01

69

Summary Rising atmospheric carbon dioxide (CO2) con-centration ([CO2]) could alter terrestrial carbon (C) cycling by  

E-print Network

Summary Rising atmospheric carbon dioxide (CO2) con- centration ([CO2]) could alter terrestrial increase in tropospheric ozone (O3) con- centration ([O3]) will interact with rising atmospheric [CO2 of CBSCs were rarely signifi- cantly affected by the CO2 and O3 treatments in decomposing fine roots. Rates

70

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

71

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

72

CO2 greenhouse in the early martian atmosphere: SO2 inhibits condensation  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

73

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

PubMed

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

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

2010-11-23

74

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

75

Constraining terrestrial ecosystem CO2 fluxes by integrating models of biogeochemistry and atmospheric transport and data of surface carbon fluxes and atmospheric CO2 concentrations  

NASA Astrophysics Data System (ADS)

Regional net carbon fluxes of terrestrial ecosystems could be estimated with either biogeochemistry models by assimilating surface carbon flux measurements or atmospheric CO2 inversions by assimilating observations of atmospheric CO2 concentrations. Here we combine the ecosystem biogeochemistry modeling and atmospheric CO2 inverse modeling to investigate the magnitude and spatial distribution of the terrestrial ecosystem CO2 sources and sinks. First, we constrain a terrestrial ecosystem model (TEM) at site level by assimilating the observed net ecosystem production (NEP) for various plant functional types. We find that the uncertainties of model parameters are reduced up to 90% and model predictability is greatly improved for all the plant functional types (coefficients of determination are enhanced up to 0.73). We then extrapolate the model to a global scale at a 0.5° × 0.5° resolution to estimate the large-scale terrestrial ecosystem CO2 fluxes, which serve as prior for atmospheric CO2 inversion. Second, we constrain the large-scale terrestrial CO2 fluxes by assimilating the GLOBALVIEW-CO2 and mid-tropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) into an atmospheric transport model (GEOS-Chem). The transport inversion estimates that: (1) the annual terrestrial ecosystem carbon sink in 2003 is -2.47 Pg C yr-1, which agrees reasonably well with the most recent inter-comparison studies of CO2 inversions (-2.82 Pg C yr-1); (2) North America temperate, Europe and Eurasia temperate regions act as major terrestrial carbon sinks; and (3) The posterior transport model is able to reasonably reproduce the atmospheric CO2 concentrations, which are validated against Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) CO2 concentration data. This study indicates that biogeochemistry modeling or atmospheric transport and inverse modeling alone might not be able to well quantify regional terrestrial carbon fluxes. However, combining the two modeling approaches and assimilating data of surface carbon flux as well as atmospheric CO2 mixing ratios might significantly improve the quantification of terrestrial carbon fluxes.

Zhu, Q.; Zhuang, Q.; Henze, D.; Bowman, K.; Chen, M.; Liu, Y.; He, Y.; Matsueda, H.; Machida, T.; Sawa, Y.; Oechel, W.

2014-09-01

76

Static opaque chamber-based technique for determination of net exchange of CO 2 between terrestrial ecosystem and atmosphere  

Microsoft Academic Search

Terrestrial carbon cycling is one of the hotspots in global change issues. In this paper, we presented the rationale for determination\\u000a of net exchange of CO2 between terrestrial and the atmosphere (NEE) and the methods for measuring several relevant components. Three key processes\\u000a for determination of NEE were addressed, including the separation of shoot autotrophic respiration from total CO2 emissions

Jianwen Zou; Yao Huang; Xunhua Zheng; Yuesi Wang; Yuquan Chen

2004-01-01

77

Evidence for and implications of an Early Archean terrestrial impact record  

NASA Technical Reports Server (NTRS)

Early Archean, 3.5 to 3.2 Ga, greenstone sequences in South Africa and Western Australia contain a well-preserved record of early terrestrial meteorite impacts. The main impact-produced deposits are layers, 10 cm to over 1 m thick, composed largely of sand-sized spherules, 0.1 to 4 mm in diameter. The beds studied to date show an assemblage of features indicating formation by the fall of debris from impact-generated ejecta clouds. Some presented data effectively rule out normal magmatic or sedimentary processes in the origin of these units and provide substantial support for an origin by large impacts on the early earth. The presence of at least four, remarkably thick, nearly pure spherule layers suggests that smaller-scale impact deposits may be even more abundant in these sequences. The existence of a well-preserved Archean terrestrial impact record suggests that a direct source of evidence is available regarding a number of important aspects of early earth history.

Lowe, Donald R.; Byerly, Gary R.

1988-01-01

78

Optimization of a prognostic biosphere model for terrestrial biomass and atmospheric CO2 variability  

NASA Astrophysics Data System (ADS)

This study investigates the capacity of a prognostic biosphere model to simulate global variability in atmospheric CO2 concentrations and vegetation carbon dynamics under current environmental conditions. Global data sets of atmospheric CO2 concentrations, above-ground biomass (AGB), and net primary productivity (NPP) in terrestrial vegetation were assimilated into the biosphere model using an inverse modeling method combined with an atmospheric transport model. In this process, the optimal physiological parameters of the biosphere model were estimated by minimizing the misfit between observed and modeled values, and parameters were generated to characterize various biome types. Results obtained using the model with the optimized parameters correspond to the observed seasonal variations in CO2 concentration and their annual amplitudes in both the Northern and Southern Hemispheres. In simulating the mean annual AGB and NPP, the model shows improvements in estimating the mean magnitudes and probability distributions for each biome, as compared with results obtained using prior simulation parameters. However, the model is less efficient in its simulation of AGB for forest type biomes. This misfit suggests that more accurate values of input parameters, specifically, grid mean AGB values and seasonal variabilities in physiological parameters, are required to improve the performance of the simulation model.

Saito, M.; Ito, A.; Maksyutov, S.

2014-08-01

79

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 1860 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 an enhanced carbon uptake of around 44 gC m-2 yr-1 (or equivalently 63 gC m-2 yr-1 over the province's forested area), during the 1980s and 1990s, and continuing into the 2000s. About three-quarters of the simulated sink enhancement in our study compared to pre-industrial conditions 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 effects of harvesting, insect disturbances and land-use change are not considered.

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

2014-02-01

80

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

81

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

82

A terrestrial biosphere model optimized to atmospheric CO2 concentration and above ground woody biomass  

NASA Astrophysics Data System (ADS)

This study documents an optimization of a prognostic biosphere model (VISIT; Vegetation Integrative Similator for Trace gases) to observations of atmospheric CO2 concentration and above ground woody biomass by using a Bayesian inversion method combined with an atmospheric tracer transport model (NIES-TM; National Institute for Environmental Studies / Frontier Research Center for Global Change (NIES/FRCGC) off-line global atmospheric tracer transport model). The assimilated observations include 74 station records of surface atmospheric CO2 concentration and aggregated grid data sets of above ground woody biomass (AGB) and net primary productivity (NPP) over the globe. Both the biosphere model and the atmospheric transport model are used at a horizontal resolution of 2.5 deg x 2.5 deg grid with temporal resolutions of a day and an hour, respectively. The atmospheric transport model simulates atmospheric CO2 concentration with nine vertical levels using daily net ecosystem CO2 exchange rate (NEE) from the biosphere model, oceanic CO2 flux, and fossil fuel emission inventory. The models are driven by meteorological data from JRA-25 (Japanese 25-year ReAnalysis) and JCDAS (JMA Climate Data Assimilation System). Statistically optimum physiological parameters in the biosphere model are found by iterative minimization of the corresponding Bayesian cost function. We select thirteen physiological parameter with high sensitivity to NEE, NPP, and AGB for the minimization. Given the optimized physiological parameters, the model shows error reductions in seasonal variation of the CO2 concentrations especially in the northern hemisphere due to abundant observation stations, while errors remain at a few stations that are located in coastal coastal area and stations in the southern hemisphere. The model also produces moderate estimates of the mean magnitudes and probability distributions in AGB and NPP for each biome. However, the model fails in the simulation of the terrestrial vegetation compositions in some grids. These misfits are assumed to derive from simplified representation in the biosphere model without the impact of land use change and dire disturbance and the seasonal variability in the physiological parameters.

Saito, M.; Ito, A.; Maksyutov, S. S.

2013-12-01

83

Does atmospheric scattering increase or decrease terrestrial photosynthesis? Strong constraints from sunlight observations  

NASA Astrophysics Data System (ADS)

Diffuse light tends to be more efficient than direct shortwave radiation in driving photosynthesis in closed canopy environments because it will penetrate more evenly into the forest canopy illuminating a greater effective surface area of leaves. Increased atmospheric column scattering will tend to both decrease the total light reaching the surface, and to convert direct light to diffuse light. These two mechanisms have opposing effects on the sensitivity of terrestrial photosynthesis to changes in atmospheric scattering. A debate exists in the literature as to which effect generally dominates on planetary scales, particularly in the context of interpretation of the anomalously large northern hemisphere summer draw-down in atmospheric carbon dioxide in 1991 -- the year of the Mount Pinatubo eruption. Here we take a fresh approach to this problem and directly examine a broad spatial network of surface observations of direct and diffuse solar radiation. We estimate the sensitivity of direct, diffuse and photosynthetically effective radiation (PER), which we define as direct + ?*diffuse, to changes in scattering on a site-by-site basis from over 100 spatially distributed time series of radiation. We find that PER generally decreases with increasing intensity of diffusive light, even when assuming the upper range of published ? values, from which we infer that increased scattering generally decreases PER. Positive sensitivity of PER to increases in scattering, again using high values for ?, are primarily confined to relatively cloud-free arid regions -- regions which do not support a closed canopy and almost certainly actually have a lower ?. This supports conclusions that other mechanisms than Pinatubo's direct influence on diffuse fractions likely accounted for the 1991 CO2 drawdown anomaly. We examine the implication of this result for modeling the response of the carbon cycle to atmospheric scattering in the context of a global carbon cycle model.

Stine, A.; Huybers, P. J.; Swann, A. L.

2013-12-01

84

Is it possible to estimate atmospheric deposition of heavy metals by analysis of terrestrial mosses?  

PubMed

Here we present a critical review of diverse research studies involving estimation of atmospheric deposition of heavy metals from the concentrations of the contaminants in terrestrial moss. The findings can be summarized as follows: i) significant correlations between the concentrations of contaminants in moss and bulk deposition were observed in only 40.1% of the cases in which the relationship was studied and in only 14.1% of the cases, the coefficient of correlation was >0.7; ii) some method-related problems were identified (i.e. small sample sizes, elimination of some data from the regression analyses, large distances between the moss sampling sites and the bulk precipitation collectors, differences in times of exposure of the moss samples and collection times for the bulk precipitation), so that the results of the studies may not be completely valid, and iii) evidence was found in the relevant literature that moss does not actually integrate the atmospheric deposition received. We also discuss the reason why, in accordance with the published data, bulk deposition cannot be correctly estimated by determination of the final concentrations of contaminants in the organism, such as the existence of different sources of contamination, the physicochemical characteristics of the sources of deposition, physicochemical processes to which the organism is subjected and the biological processes that take place in the moss. Taking into account the above findings, it was concluded that, except for certain elements and specific cases (i.e. Pb and Cd), atmospheric deposition of elements cannot be accurately estimated from the concentrations of metals and metalloids in moss tissues. However, the analysis of moss does provide information about the presence of contaminants in the atmosphere, their spatial and temporal patterns of distribution and how they are taken up by live organisms. Use of mosses is therefore recommended as a complementary (rather than an alternative) technique in the conventional analysis of bulk deposition of contaminants. PMID:20889189

Aboal, J R; Fernández, J A; Boquete, T; Carballeira, A

2010-11-15

85

Journal of Atmospheric and Solar-Terrestrial Physics 65 (2003) 499508 www.elsevier.com/locate/jastp  

E-print Network

that are related to the bandwidth of the measurement system. The lightning charge moment change requiredJournal of Atmospheric and Solar-Terrestrial Physics 65 (2003) 499­508 www.elsevier.com/locate/jastp Current moment in sprite-producing lightning Steven A. Cummer Electrical and Computer Engineering

Cummer, Steven A.

86

History of GPS Sounding : Special issue of Terrestrial, Atmospheric and Oceanic Science, 11(1), 1-20, March 2000  

E-print Network

History of GPS Sounding : Special issue of Terrestrial, Atmospheric and Oceanic Science, 11(1), 1-20, March 2000 Yunck et al. 1 1/24/00 A History of GPS Sounding Thomas P. Yunck1 , Chao-Han Liu2 and Randolph Ware3 Abstract The roots of GPS sounding go back to the first days of interplanetary flight

87

Journal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 159171 www.elsevier.com/locate/jastp  

E-print Network

by the solar wind. Indeed, the most recent statistical models essentially prescribe the pattern of convection imposed by the solar wind encounters the geomagnetic ÿeld in a favorable orientation, energy and momentumJournal of Atmospheric and Solar-Terrestrial Physics 64 (2002) 159­171 www

Shepherd, Simon

88

Dermal bone in early tetrapods: a palaeophysiological hypothesis of adaptation for terrestrial acidosis  

PubMed Central

The dermal bone sculpture of early, basal tetrapods of the Permo-Carboniferous is unlike the bone surface of any living vertebrate, and its function has long been obscure. Drawing from physiological studies of extant tetrapods, where dermal bone or other calcified tissues aid in regulating acid–base balance relating to hypercapnia (excess blood carbon dioxide) and/or lactate acidosis, we propose a similar function for these sculptured dermal bones in early tetrapods. Unlike the condition in modern reptiles, which experience hypercapnia when submerged in water, these animals would have experienced hypercapnia on land, owing to likely inefficient means of eliminating carbon dioxide. The different patterns of dermal bone sculpture in these tetrapods largely correlates with levels of terrestriality: sculpture is reduced or lost in stem amniotes that likely had the more efficient lung ventilation mode of costal aspiration, and in small-sized stem amphibians that would have been able to use the skin for gas exchange. PMID:22535781

Janis, Christine M.; Devlin, Kelly; Warren, Daniel E.; Witzmann, Florian

2012-01-01

89

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

SciTech Connect

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

Beerbower, J.R. (State Univ., Binghamton, NY (United States). Dept. of Geological Science); Olson, E.C. (Univ. of California, Los Angeles, CA (United States). Dept. of Biology); Hotton, N. III (Smithsonian, Washington, DC (United States). Dept. of Paleobiology)

1992-01-01

90

Atmospheric sulphuric acid and aerosol formation: implications from atmospheric measurements for nucleation and early growth mechanisms  

Microsoft Academic Search

We have investigated the formation and early growth of atmospheric secondary aerosol particles building on atmospheric measurements. The measurements were part of the QUEST 2 campaign which took place in spring 2003 in Hyytiälä (Finland). During the campaign numerous new aerosol particle formation events occurred of which 15 were accompanied by gaseous sulphuric acid measurements. Our detailed analysis of these

S.-L. Sihto; M. Kulmala; V.-M. Kerminen; M. Dal Maso; T. Petäjä; I. Riipinen; H. Korhonen; F. Arnold; R. Janson; M. Boy; A. Laaksonen; K. E. J. Lehtinen

2006-01-01

91

The rise of oxygen in Earth's early ocean and atmosphere  

NASA Astrophysics Data System (ADS)

The rapid increase of carbon dioxide concentration in Earth's modern atmosphere is a matter of major concern. But for the atmosphere of roughly two-and-half billion years ago, interest centres on a different gas: free oxygen (O2) spawned by early biological production. The initial increase of O2 in the atmosphere, its delayed build-up in the ocean, its increase to near-modern levels in the sea and air two billion years later, and its cause-and-effect relationship with life are among the most compelling stories in Earth's history.

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

2014-02-01

92

Nitrogen Fixation on Early Mars and Other Terrestrial Planets: Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate  

Microsoft Academic Search

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

David P. Summers; Bishun Khare

2007-01-01

93

Mobile sampler for use in acquiring samples of terrestrial atmospheric gases  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

94

EARTH HISTORY: Sulfate Clues for the Early History of Atmospheric  

E-print Network

oxygen in the Archean atmosphere range from as early as 3500 Ma (5, 6) to 2000 Ma (7). Although of information has proved frustrating: Rock sequences of Archean age are rare, of limited extent, poorly of Archean sulfur deposits turn out to be fairly consistent between different sites, indicating that global

Paytan, Adina

95

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

NASA Astrophysics Data System (ADS)

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

Losiak, Anna

2014-05-01

96

Requirements for the early atmosphere of Mars from nitrogen isotope ratios  

NASA Technical Reports Server (NTRS)

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

Fox, J. L.

1993-01-01

97

Nitrogen Fixation on Early Mars and Other Terrestrial Planets. Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate  

Microsoft Academic Search

The abiotic fixation of nitrogen on early terrestrial planets, such as Mars and the Earth, is important for number of reasons. Nitrogen is an essential biochemical element and the prebiotic fixation of nitrogen into a form suitable for the formation of nitrogen containing prebiotic organic compounds is important for the origin of life. Since loss of nitrogen can result in

D. P. Summers; B. Khare

2005-01-01

98

Early (4.5 Ga) formation of terrestrial crust: LuHf, 18 thermometry results for Hadean zircons  

E-print Network

Early (4.5 Ga) formation of terrestrial crust: Lu­Hf, 18 O, and Ti thermometry results for Hadean the characterization of 176 Hf/177 Hf initial ratios (Hf ) in Hadean zircons by acquiring a further 116 laser ablation(T) throughout the Hadean, although no positive Hf(T) values were documented in this study. Monte Carlo modelling

Harrison, Mark

99

A carbon dioxide/methane greenhouse atmosphere on early Mars  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

100

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

102

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

103

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

104

A Process-based Analysis of Methane Exchanges Between Alaskan Terrestrial Ecosystems and the Atmosphere  

E-print Network

We developed and used a new version of the Terrestrial Ecosystem Model (TEM) to study how rates of methane (CH4) emissions and consumption in Alaskan soils have changed over the past century in response to observed changes ...

Zhuang, Qianlai.

105

Photochemistry in Terrestrial Exoplanet Atmospheres. III. Photochemistry and Thermochemistry in Thick Atmospheres on Super Earths and Mini Neptunes  

NASA Astrophysics Data System (ADS)

Some super Earths and mini Neptunes will likely have thick atmospheres that are not H2-dominated. We have developed a photochemistry-thermochemistry kinetic-transport model for exploring the compositions of thick atmospheres on super Earths and mini Neptunes, applicable for both H2-dominated atmospheres and non-H2-dominated atmospheres. Using this model to study thick atmospheres for wide ranges of temperatures and elemental abundances, we classify them into hydrogen-rich atmospheres, water-rich atmospheres, oxygen-rich atmospheres, and hydrocarbon-rich atmospheres. We find that carbon has to be in the form of CO2 rather than CH4 or CO in a H2-depleted water-dominated thick atmosphere and that the preferred loss of light elements from an oxygen-poor carbon-rich atmosphere leads to the formation of unsaturated hydrocarbons (C2H2 and C2H4). We apply our self-consistent atmosphere models to compute spectra and diagnostic features for known transiting low-mass exoplanets GJ 1214 b, HD 97658 b, and 55 Cnc e. For GJ 1214 b, we find that (1) C2H2 features at 1.0 and 1.5 ?m in transmission and C2H2 and C2H4 features at 9-14 ?m in thermal emission are diagnostic for hydrocarbon-rich atmospheres; (2) a detection of water-vapor features and a confirmation of the nonexistence of methane features would provide sufficient evidence for a water-dominated atmosphere. In general, our simulations show that chemical stability has to be taken into account when interpreting the spectrum of a super Earth/mini Neptune. Water-dominated atmospheres only exist for carbon to oxygen ratios much lower than the solar ratio, suggesting that this kind of atmospheres could be rare.

Hu, Renyu; Seager, Sara

2014-03-01

106

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

USGS Publications Warehouse

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

Weems, R.E.

1992-01-01

107

Terrestrial carbon sink observed from space: Sensitivity of atmospheric CO2 growth rates and seasonal cycle amplitudes to surface temperature  

NASA Astrophysics Data System (ADS)

The terrestrial biosphere is currently acting as a net carbon sink on the global scale, exhibiting significant interannual variability in strength. To reliably predict the future strength of the land sink and its role in atmospheric CO2 growth, the underlying biogeochemical processes and their response to a changing climate need to be well understood. In particular, better knowledge of the impact of key climate variables such as temperature on the biospheric carbon reservoir is essential. Global satellite measurements of column-averaged mole fractions of atmospheric CO2, which offer complementary information to the accurate and precise but inevitably sparse ground-based measurements, can contribute to determine characteristics of the terrestrial carbon sink. It is demonstrated using nearly a decade of SCIAMACHY nadir measurements that years with higher temperatures during the growing season can be robustly associated with larger growth rates in atmospheric CO2 and smaller seasonal cycle amplitudes for northern mid-latitudes. We find linear relationships between warming and CO2 growth as well as seasonal cycle amplitude at the 98 % significance level. The quantitative estimates of the corresponding covariations are consistent with those from the CarbonTracker data assimilated CO2 product, indicating that the temperature dependence of the model surface fluxes is realistic. The derived results suggest that the terrestrial carbon sink is less efficient at higher temperatures during the analysed time period. Unless the biosphere has the ability to adapt its carbon storage under warming conditions in the longer term, such a temperature response entails the risk of potential future sink saturation via a positive carbon-climate feedback.

Schneising, Oliver; Reuter, Maximilian; Buchwitz, Michael; Heymann, Jens; Bovensmann, Heinrich; Burrows, John P.

2014-05-01

108

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

109

Heat flow vs. atmospheric greenhouse on early Mars  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

110

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

111

Terrestrial biosphere model performance for inter-annual variability of land-atmosphere CO2 exchange  

E-print Network

variability in climate, they are rarely tested explicitly against inter-annual variability in observations of biotic and abiotic factors. Replicating this variability thus represents the `acid test' for terrestrial. Herein, using standardized data from the North American Carbon Program, we assess the performance of 16

Montana, University of

112

Atmospheric Water Absorption and the Water Budget of Terrestrial Isopods (Crustacea, Isopoda, Oniscidea)  

Microsoft Academic Search

Studies of terrestrial isopods (Crustacea, Iso- poda, Oniscidea) have revealed a capacity for active water vapor absorption (WVA) in the taxonomic sections Cri- nocheta and Diplocheta but not in Synocheta. Uptake thresholds in Crinocheta are modest by comparison with other vapor absorbers, but standardized uptake fluxes are among the highest recorded and are probably an adaptive requirement to counter the

JONATHAN C. WRIGHT; JOHN MACHIN

1993-01-01

113

Integration of ice core, marine and terrestrial records: new insights into Holocene atmospheric circulation dynamics over NW Europe  

NASA Astrophysics Data System (ADS)

We analyzed the oxygen (?18O) and carbon (?13C) isotope composition of lacustrine carbonates (Chara sp. and Bithynia tentaculata) from a lake sediment sequence (Lake Bjärsträsk) on the island of Gotland, southern Sweden. Our new isotopic records show a significant consistency with existing regional climatic reconstructions, as well as with paleorecords reflecting large-scale circulation dynamics. By comparing our data to ice core records from Greenland and to regional- and global-scale terrestrial and marine climate records, we explore potential couplings of Mid- and Late Holocene extreme summer climate conditions in northwestern Europe to orbital forcing and low-latitude atmospheric circulation dynamics. Specifically, we discuss the relationship between long-term changes in the position of the North Atlantic subtropical front and the frequency of summer blocking anticyclones over southern Sweden. Furthermore, we tentatively outline the spatial structure of predominant modes of atmospheric variability over the North Atlantic sector throughout the Holocene.

Muschitiello, F.; Hammarlund, D.; Wohlfarth, B.

2012-12-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

115

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

PubMed

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

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

2013-11-01

116

Hydraulics of Asteroxylon mackei, an early Devonian vascular plant, and the early evolution of water transport tissue in terrestrial plants.  

PubMed

The core of plant physiology is a set of functional solutions to a tradeoff between CO(2) acquisition and water loss. To provide an important evolutionary perspective on how the earliest land plants met this tradeoff, we constructed a mathematical model (constrained geometrically with measurements of fossils) of the hydraulic resistance of Asteroxylon, an Early Devonian plant. The model results illuminate the water transport physiology of one of the earliest vascular plants. Results show that Asteroxylon's vascular system contains cells with low hydraulic resistances; these resistances are low because cells were covered by scalariform pits, elliptical structures that permit individual cells to have large areas for water to pass from one cell to another. Asteroxylon could move a large amount of water quickly given its large pit areas; however, this would have left these plants particularly vulnerable to damage from excessive evapotranspiration. These results highlight a repeated pattern in plant evolution, wherein the evolution of highly conductive vascular tissue precedes the appearance of adaptations to increase water transport safety. Quantitative insight into the vascular transport of Asteroxylon also allows us to reflect on the quality of CO(2) proxy estimates based on early land plant fossils. Because Asteroxylon's vascular tissue lacked any safety features to prevent permanent damage, it probably used stomatal abundance and behavior to prevent desiccation. If correct, low stomatal frequencies in Asteroxylon reflect the need to limit evapotranspiration, rather than adaptation to high CO(2) concentrations in the atmosphere. More broadly, methods to reveal and understand water transport in extinct plants have a clear use in testing and bolstering fossil plant-based paleoclimate proxies. PMID:21244621

Wilson, J P; Fischer, W W

2011-03-01

117

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

118

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

NASA Technical Reports Server (NTRS)

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

Zahnle, K.

1991-01-01

119

Challenges and opportunities to reduce uncertainty in projections of future atmospheric CO2: a combined marine and terrestrial biosphere perspective  

NASA Astrophysics Data System (ADS)

Atmospheric CO2 and climate projections for the next century vary widely across current Earth system models (ESMs), owing to different representations of the interactions between the marine and land carbon cycle on the one hand, and climate change and increasing atmospheric CO2 on the other hand. Several efforts have been made in the last years to analyse these differences in detail in order to suggest model improvements. Here we review these efforts and analyse their successes, but also the associated uncertainties that hamper the best use of the available observations to constrain and improve the ESMs models. The aim of this paper is to highlight challenges in improving the ESMs that result from: (i) uncertainty about important processes in terrestrial and marine ecosystems and their response to climate change and increasing atmospheric CO2; (ii) structural and parameter-related uncertainties in current land and marine models; (iii) uncertainties related to observations and the formulations of model performance metrics. We discuss the implications of these uncertainties for reducing the spread in future projections of ESMs and suggest future directions of work to overcome these uncertainties.

Dalmonech, D.; Foley, A. M.; Anav, A.; Friedlingstein, P.; Friend, A. D.; Kidston, M.; Willeit, M.; Zaehle, S.

2014-02-01

120

Project EARTH-13-MF1: A reassessment of the early terrestrial ecosystems: perspectives from arthropods  

E-print Network

arthropods Supervisors: Matt Friedman, Russell Garwood (University of Manchester) Fossils of the earliest of an invertebrate group called the arthropods; vertebrates, by contrast, made the move onto land over 40 million years later. By the Devonian period the three major terrestrial arthropod clades were established

Henderson, Gideon

121

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

122

The role of marine biota in the evolution of terrestrial biota: Gases and genes  

Microsoft Academic Search

There is greater biodiversity (in the senseof genetic distance among higher taxa) ofextant marine than of terrestrialO2-evolvers. In addition tocontributing the genes from one group ofalgae (Class Charophyceae, DivisionChlorophyta) to produce by evolution thedominant terrestrial plants (Embryophyta),the early marine O2-evolvers greatlymodified the atmosphere and hence the landsurface when the early terrestrialO2-evolvers grew. The earliestterrestrial phototrophs (from geochemicalevidence) occurred 1.2 Ga

JOHN A. RAVEN

1997-01-01

123

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

124

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

125

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. PMID:19487662

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

2009-01-01

126

Areas where solar-terrestrial coupling may influence or be influenced by the middle atmosphere  

NASA Technical Reports Server (NTRS)

The nature of the wave interactions, particularly those induced by transient solar and geomagnetic phenomena is discussed. Solar activity which includes modulations of galactic cosmic ray flux reaching Earth is discussed. Coupling processes involving charged particles and atmospheric electric structure are presented.

Goldberg, R. A.

1979-01-01

127

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

128

Evidence for propagation of aerobic bacteria in particles suspended in gaseous atmospheres. [Terrestrial microorganism contamination of Jupiter atmosphere  

NASA Technical Reports Server (NTRS)

One factor involved in the possibility that airborne microbes might contaminate the Jovian atmosphere is whether microbes have the capacity to propagate in air. Prior to these studies, the evidence was that the airborne state was lethal to microbes. An aerosol of aerobic bacteria was mixed with another containing C-14-glucose, and the presence of C-14-CO2 was subsequently detected, which indicates that the airborne cells were metabolically active. In the same type of experiment, it was shown that thymidine was incorporated into the acid-insoluble fraction of samples, indicating the formation of DNA. It was also shown, both by an increase in the numbers of viable cells and a parallel increase in particle numbers, that at least two new generations of cells could occur. Evidence for propagation of anaerobic bacteria has so far been negative.

Dimmick, R. L.; Chatigny, M. A.; Wolochow, H.; Straat, P.

1977-01-01

129

Impact of Aquatic and Terrestrial Emissions on Atmospheric N2O Variability  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

130

Global N/sub 2/O cycles - Terrestrial emissions, atmospheric accumulation and biospheric effects  

SciTech Connect

Recent findings concerning the budget and cycles of nitrous oxide on earth are summarized, and the sources and sinks for N/sub 2/O on land, in the ocean, and in the atmosphere are examined in view of the N/sub 2/O concentration increase of 0.2-0.4 percent per year, observed over the period of 1975-1982. Possible atmospheric and biospheric consequences of the N/sub 2/O concentration increase are evaluated. N/sub 2/O emission values are given for several major ecosystem types, such as forest, desert, cultivated land; values from different sources are compared and discussed. Analysis shows an excess of documented sources over sinks by 0-51 Tg N/sub 2/O-N/yr. 63 references.

Banin, A.; Lawless, J.G.; Whitten, R.C.; Oser, H.; Oro, J.; Macelroy, R.D.; Klein, H.P.; Devincenzi, D.L.; Young, R.S.

1984-01-01

131

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

NASA Technical Reports Server (NTRS)

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

Rubashev, B. M.

1978-01-01

132

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

2011-12-01

133

Studies of Constraints from the Terrestrial Planets, Asteroid Belt and Giant Planet Obliquities on the Early Solar System Instability  

NASA Astrophysics Data System (ADS)

The planetary instability has been invoked as a convenient way to explain several observables in the present Solar System. This theory, frequently referred to under a broad and somewhat ill-defined umbrella as the ‘Nice model’, postulates that at least one of the ice giants suffered scattering encounters with Jupiter and Saturn. This could explain several things, including the excitation of the proper eccentric mode in Jupiter's orbit, survival of the terrestrial planets during giant planet migration, and, if the instability was conveniently delayed, also the Late Heavy Bombardment of the Moon. These properties/events would be unexpected if the migration histories of the outer planets were ideally smooth (at least no comprehensive model has yet been fully developed to collectively explain them). Additional support for the planetary instability comes from the dynamical properties of the asteroid and Kuiper belts, Trojans, and planetary satellites. We created a large database of dynamical evolutions of the outer planets through and 100 Myr past the instability (Nesvorny and Morbidelli 2012. Many of these dynamical histories have been found to match constraints from the orbits of the outer planets themselves. We now propose to test these different scenarios using constraints from the terrestrial planets, asteroid belt and giant planet obliquities. As we explain in the proposal narrative, we will bring all these constraints together in an attempt to develop a comprehensive model of early Solar System's evolution. This will be a significant improvement over the past work, where different constraints were considered piecewise and in various approximations. Our work has the potential to generate support for the Nice-type instability, or to rule it out, which could help in sparking interest in developing better models. RELEVANCE The proposed research is fundamental to understanding the formation and early evolution of the Solar System. This is a central theme of NASA's Strategic Goals and the OSS program. Specifically, the NRA for the OSS program states that the program solicits basic research proposals to conduct scientific investigations related to understanding the formation and early evolution of planetary systems, and that the OSS objectives include ‘theoretical investigations related to the formation and evolution of planetary systems.’ Here we propose to study the effects of early Solar System's instability on the terrestrial planets, asteroid belt, and giant planet obliquities. Our goal is to constrain planetary formation processes and the events that have taken place in the Solar System over its history.

Nesvorny, David

134

Abiotic formation of O2 and O3 in high-CO2 terrestrial atmospheres  

E-print Network

Previous research has indicated that high amounts of ozone (O3) and oxygen (O2) may be produced abiotically in atmospheres with high concentrations of CO2. The abiotic production of these two gases, which are also characteristic of photosynthetic life processes, could pose a potential "false-positive" for remote-sensing detection of life on planets around other stars.We show here that such false positives are unlikely on any planet that possesses abundant liquid water, as rainout of oxidized species onto a reduced planetary surface should ensure that atmospheric H2 concentrations remain relatively high, and that O2 and O3 remain low. Our aim is to determine the amount of O3 and O2 formed in a high CO2 atmosphere for a habitable planet without life. We use a photochemical model that considers hydrogen (H2) escape and a detailed hydrogen balance to calculate the O2 and O3 formed on planets with 0.2 of CO2 around the Sun, and 0.02, 0.2 and 2 bars of CO2 around a young Sun-like star with higher UV radiation. The concentrations obtained by the photochemical model were used as input in a radiative transfer model that calculated the spectra of the modeled planets. The O3 and O2 concentrations in the simulated planets are extremely small, and unlikely to produce a detectable signature in the spectra of those planets. We conclude that with a balanced hydrogen budget, and for planets with an active hydrological cycle, abiotic formation of O2 and O3 is unlikely to create a possible false positive for life detection in either the visible/near-infrared or mid-infrared wavelength regimes.

A. Segura; V. S. Meadows; J. F. Kasting; D. Crisp; M. Cohen

2007-07-11

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

136

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

PubMed

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

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

2014-03-01

137

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

NASA Astrophysics Data System (ADS)

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

McPherron, R. L.

2011-12-01

138

Impacts and atmospheric erosion on the early Earth  

NASA Technical Reports Server (NTRS)

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

Vickery, A. M.

1991-01-01

139

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

140

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

141

Arctic Climate and Terrestrial Vegetation Responses During the Middle to Late Eocene and Early Oligocene: Colder Winters Preceded Cool-Down  

Microsoft Academic Search

The late Eocene to early Oligocene is recognized as an interval of substantial change in the global climate, with isotopic proxies of climate indicating a significant drop in sea surface temperatures. Other studies have shown, however that at middle latitudes that terrestrial mean annual temperature did not change significantly over this interval, and that the major change was likely a

D. R. Greenwood; J. Eldrett

2006-01-01

142

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

143

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

NASA Astrophysics Data System (ADS)

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

Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu

2011-07-01

144

Net terrestrial CO2 exchange over China during 2001-2010 estimated with an ensemble data assimilation system for atmospheric CO2  

NASA Astrophysics Data System (ADS)

this paper we present an estimate of net ecosystem CO2 exchange over China for the years 2001-2010 using the CarbonTracker Data Assimilation System for CO2 (CTDAS). Additional Chinese and Asian CO2 observations are used in CTDAS to improve our estimate. We found that the combined terrestrial ecosystems in China absorbed about -0.33 Pg C yr-1 during 2001-2010. The uncertainty on Chinese terrestrial carbon exchange estimates as derived from a set of sensitivity experiments suggests a range of -0.29 to -0.64 Pg C yr-1. This total Chinese terrestrial CO2 sink is attributed to the three major biomes (forests, croplands, and grass/shrublands) with estimated CO2 fluxes of -0.12 Pg C yr-1 (range from -0.09 to -0.19 Pg C yr-1), -0.12 Pg C yr-1 (range from -0.09 to -0.26 Pg C yr-1), and -0.09 Pg C yr-1 (range from -0.09 to -0.17 Pg C yr-1), respectively. The peak-to-peak amplitude of interannual variability of the Chinese terrestrial ecosystem carbon flux is 0.21 Pg C yr-1 (~64% of mean annual average), with the smallest CO2 sink (-0.19 Pg C yr-1) in 2003 and the largest CO2 sink (-0.40 Pg C yr-1) in 2007. We stress that our estimate of terrestrial ecosystem CO2 uptake based on inverse modeling strongly depends on a limited number of atmospheric CO2 observations used. More observations in China specifically and in Asia in general are needed to improve the accuracy of terrestrial carbon budgeting for this region.

Zhang, H. F.; Chen, B. Z.; Laan-Luijkx, I. T.; Chen, J.; Xu, G.; Yan, J. W.; Zhou, L. X.; Fukuyama, Y.; Tans, P. P.; Peters, W.

2014-03-01

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

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

PubMed

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

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

2012-07-01

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

Beyond the atmosphere: Early years of space science  

NASA Technical Reports Server (NTRS)

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

Newell, H. E.

1980-01-01

149

Terrestrial impact of abrupt changes in the North Atlantic thermohaline circulation: Early Holocene, UK  

NASA Astrophysics Data System (ADS)

Abrupt cooling events are features of Holocene climate and may recur in the future. We use lake records from Hawes Water, NW England, to quantify the impact of two prominent early Holocene climatic events. Subdecadal oxygen isotope records from sedimentary carbonate (18?Oc), dated using thermal ionization mass spectrometry (TIMS) U-series analyses, provide evidence for abrupt cold events, lasting ˜50 and ˜150 yr at 9350 and 8380 yr ago, which correlate with the 9.3 ka and 8.2 ka events recognized in Greenland ice cores. At Hawes Water, mean July air temperatures, inferred from chirono-mid assemblages, decreased by ˜1.6 °C during each event. Calculations show that the isotopic excursions were dominantly caused by decreases in the isotopic composition of meteoric precipitation (18?Op) by ˜1.3‰; this is interpreted as a direct downstream response to cooling and freshening of northeast Atlantic surface water by melting ice sheets. Intermediate in magnitude between events observed in Greenland and central Europe, the effects are consistent with a partial shutdown of the North Atlantic thermohaline circulation.

Marshall, Jim D.; Lang, Barbara; Crowley, Stephen F.; Weedon, Graham P.; van Calsteren, Peter; Fisher, Elizabeth H.; Holme, Richard; Holmes, Jonathan A.; Jones, Richard T.; Bedford, Alan; Brooks, Steven J.; Bloemendal, Jan; Kiriakoulakis, Kostas; Ball, James D.

2007-07-01

150

Comparative Climatology of Terrestrial Planets  

NASA Astrophysics Data System (ADS)

Public awareness of climate change on Earth is currently very high, promoting significant interest in atmospheric processes. We are fortunate to live in an era where it is possible to study the climates of many planets, including our own, using spacecraft and groundbased observations as well as advanced computational power that allows detailed modeling. Planetary atmospheric dynamics and structure are all governed by the same basic physics. Thus differences in the input variables (such as composition, internal structure, and solar radiation) among the known planets provide a broad suite of natural laboratory settings for gaining new understanding of these physical processes and their outcomes. Diverse planetary settings provide insightful comparisons to atmospheric processes and feedbacks on Earth, allowing a greater understanding of the driving forces and external influences on our own planetary climate. They also inform us in our search for habitable environments on planets orbiting distant stars, a topic that was a focus of Exoplanets, the preceding book in the University of Arizona Press Space Sciences Series. Quite naturally, and perhaps inevitably, our fascination with climate is largely driven toward investigating the interplay between the early development of life and the presence of a suitable planetary climate. Our understanding of how habitable planets come to be begins with the worlds closest to home. Venus, Earth, and Mars differ only modestly in their mass and distance from the Sun, yet their current climates could scarcely be more divergent. Our purpose for this book is to set forth the foundations for this emerging science and to bring to the forefront our current understanding of atmospheric formation and climate evolution. Although there is significant comparison to be made to atmospheric processes on nonterrestrial planets in our solar system — the gas and ice giants — here we focus on the terrestrial planets, leaving even broader comparisons to a future volume. Our authors have taken on the task to look at climate on the terrestrial planets in the broadest sense possible — by comparing the atmospheric processes at work on the four terrestrial bodies, Earth, Venus, Mars, and Titan (Titan is included because it hosts many of the common processes), and on terrestrial planets around other stars. These processes include the interactions of shortwave and thermal radiation with the atmosphere, condensation and vaporization of volatiles, atmospheric dynamics, chemistry and aerosol formation, and the role of the surface and interior in the long-term evolution of climate. Chapters herein compare the scientific questions, analysis methods, numerical models, and spacecraft remote sensing experiments of Earth and the other terrestrial planets, emphasizing the underlying commonality of physical processes. We look to the future by identifying objectives for ongoing research and new missions. Through these pages we challenge practicing planetary scientists, and most importantly new students of any age, to find pathways and synergies for advancing the field. In Part I, Foundations, we introduce the fundamental physics of climate on terrestrial planets. Starting with the best studied planet by far, Earth, the first chapters discuss what is known and what is not known about the atmospheres and climates of the terrestrial planets of the solar system and beyond. In Part II, Greenhouse Effect and Atmospheric Dynamics, we focus on the processes that govern atmospheric motion and the role that general circulation models play in our current understanding. In Part III, Clouds and Hazes, we provide an in-depth look at the many effects of clouds and aerosols on planetary climate. Although this is a vigorous area of research in the Earth sciences, and very strongly influences climate modeling, the important role that aerosols and clouds play in the climate of all planets is not yet well constrained. This section is intended to stimulate further research on this critical subject. The study of climate involves much more than

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

151

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

152

MODIS-Derived Terrestrial Primary Production  

NASA Astrophysics Data System (ADS)

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

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

153

Model atmospheres for the early stages of novae in outburst  

NASA Technical Reports Server (NTRS)

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 large temperature differences between inner and outer parts. The spectra show large excesses in the IR and small Balmer jumps which may either be in absorption or emission. For the parameters considered most lines are in absorption if powerlaw density distributions and radiative equilibrium are assumed. The effects of modifications in the temperature structure (e.g., heating from shock fronts) and in the density stratifications as well as changes in the abundances are discussed.

Wehrse, R.; Hauschildt, P. H.; Shaviv, G.; Starrfield, Sumner G.

1990-01-01

154

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

155

Influence of aerosol source regions and transport pathway on ?D of terrestrial biomarkers in atmospheric aerosols from the East China Sea  

NASA Astrophysics Data System (ADS)

We measured stable hydrogen isotope ratios (?D) of terrestrial biomarkers (n-alkanes and n-fatty acids) in atmospheric total suspended particles collected at Jeju Island in the East China Sea, from April 2001 to March 2002, to better understand the influence of long-range atmospheric transport on their seasonal variations. The ?D values of the C27, C29 and C31n-alkanes (?DALK) show a significant negative correlation with the CPI values of n-alkanes (r2 = 0.26, p < 0.01), suggesting that the ?DALK variations are partly attributed to a superimposed contribution from fossil fuel hydrocarbons. Seasonal variations in the concentrations of the C22-C28 even-carbon numbered n-fatty acids revealed relatively high concentrations in spring, autumn and winter seasons, in which the air masses are transported from northeast Asia. In contrast, the concentrations are low in summer when the air masses are transported from Southeast Asia and the Pacific. Relatively high C26/FA and low C24/FA ratios in spring, autumn and winter samples suggest that the C26n-fatty acids are more abundantly transported from the Asian continent during these seasons. Seasonal variations in the ?D of the C22-C26 even-carbon numbered n-fatty acids exhibit significant enrichment with D (by ˜40‰) in May and June to August samples, whereas the ?D of the C28n-fatty acids gradually decrease during summer. The magnitude of the ?D offsets (˜45‰) between the C28n-fatty acid and the other homologues are much larger than those observed in East Asia spanning 18°N-50°N latitude (ca. 30‰), suggesting that the decoupling is likely attributed to the mixing of distinct source vegetation with different ?D ratios. Comparison of the weighted-mean ?D values of n-fatty acids (?DFA) between air mass source categories revealed relatively low values (˜-170‰) in samples with trajectories from the northeastern part of the Asian continent, supporting that the ?D analyses may be a powerful tool in deciphering the source regions of terrestrial biomarkers in atmospheric aerosols from the Asian continent. The results of this study provides important implications for paleoclimate studies that the ?D variations of long-range transported terrestrial biomarkers in remote ocean sediments may have recorded past changes in source strengths of the biomarkers and therefore have a potential to reconstruct paleo-wind patterns and transport of terrestrial carbon over the Pacific.

Yamamoto, Shinya; Kawamura, Kimitaka; Seki, Osamu; Kariya, Tadashi; Lee, Meehye

2013-04-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

157

Implications of present-day abiogenic methane fluxes for the early Archean atmosphere  

E-print Network

Implications of present-day abiogenic methane fluxes for the early Archean atmosphere Simon prebiotic Archean. Based on estimates of the rate of seafloor spreading and the degree of serpentinization to maintain above-freezing surface temperatures during the Archean. The very high temperatures ($70°C

Simon, Emmanuel

158

A relatively reduced Hadean continental crust and implications for the early atmosphere and crustal rheology  

E-print Network

1 A relatively reduced Hadean continental crust and implications for the early atmosphere-elements data of igneous zircons of crustal origin, we show that the Hadean continental crust was significantly ago. We suggest that the increase in the oxidation state of the Hadean continental crust is related

Paris-Sud XI, Université de

159

Photochemical consequences of enhanced CO2 levels in earth's early atmosphere  

NASA Technical Reports Server (NTRS)

Greatly enhanced atmospheric CO2 concentrations are the most likely mechanism for offsetting the effects of reduced solar luminosity early in the earth's history. CO2 levels of 80 to 600 times the present value could have maintained a mean surface temperature of 0 C to 15 C, given a 25 percent decrease in solar output. Such high CO2 levels are at least qualitatively consistent with the present understanding of the carbonate-silicate geochemical cycle. The presence of large amounts of CO2 has important implications for the composition of the earth's prebiotic atmosphere. The hydrogen budget of a high-CO2 primitive atmosphere would have been strongly influenced by rainout of H2O2 and H2CO. The reaction of H2O2 with dissolved ferrous iron in the early oceans could have been a major sink for atmospheric oxygen. The requirement that this loss of oxygen be balanced by a corresponding loss of hydrogen (by escape to space and rainout of H2CO) implies that the atmospheric H2 mixing ratio was greater than 2 x 10 to the -5th and the ground level O2 mixing ratio was below 10 to the -12th, even if other surface sources of H2 were small. These results are only weakly dependent on changes in solar UV flux, rainout rates, and vertical mixing rates in the primitive atmosphere.

Kasting, J. F.

1985-01-01

160

Long-range atmospheric transport and deposition of anthropogenic contaminants and their potential effects on terrestrial ecosystems. Book chapter  

Microsoft Academic Search

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. Due to the phenomenon of long-range atmospheric transport, even the most remote areas of the plant are not out of range of contaminants emitted from distant anthropogenic sources. Many of these airborne contaminants are

T. J. Moser; J. R. Barker; D. T. Tingey

1991-01-01

161

Complex Propagation of Large Sound Sources in Terrestrial-like Atmospheres and its Application to Bolide Detection  

Microsoft Academic Search

We have developed an advanced generalized, acoustic ray-tracing model to capture the behavior of sound (i.e. its radiation pattern and range of detectability) in the complex dynamical systems of the Venus, Earth, Mars, and Titan atmospheres. Sound propagation is affected by the composition, structure, and dynamics of a planet's atmosphere; therefore we have adopted a modular approach so that any

Jean-pierre Williams; I. McEwan

2006-01-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

163

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

PubMed

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

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

2014-01-01

164

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

PubMed Central

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

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

2014-01-01

165

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

167

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

168

Fractal and Multifractal Analysis of the Rise of Oxygen in Earth's Early Atmosphere  

E-print Network

The rise of oxygen in Earth's atmosphere that occurred 2.4 to 2.2 billion years ago is known as the Earth's Great Oxidation, and its impact on the development of life on Earth was profound. The proposed underlying mathematical models are based on physical parameters whose values are currently not well-established owing to uncertainties in geological and biological data. In this paper, a previously developed model of Earth's atmosphere is modified by adding different strengths of noise to account for the parameters' uncertainties. The effects of the noise on time variations of oxygen, carbon and methane in Earth's early atmosphere are investigated by using fractal and multifractal analysis. We show that these time variations cannot properly be described by a single fractal dimension because they exhibit multifractal characteristics. The obtained results also demonstrate that our time series exhibit the multifractality caused by the long-range time correlations.

Satish Kumar; Zdzislaw E. Musielak; Manfred Cuntz

2014-02-13

169

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

170

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

171

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

NASA Technical Reports Server (NTRS)

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

Zipf, E. C., Jr.

1974-01-01

172

The role of terrestrial plants in limiting atmospheric CO2 decline over the past 24 million years  

E-print Network

changes in spreading rates dur- ing the Eocene or the Oligocene. In contrast, physical weathering rates), and low but variable CO2 values based on the stomatal indices of fossil leaves14 . The drop in atmospheric/or enhanced chemical weathering of silicate rocks15 . Although there is no consensus regarding Cenozoic CO2

173

A Preliminary Study of the Application of Some Predictive Modeling Techniques to Assess Atmospheric Mercury Emissions from Terrestrial Surfaces  

Microsoft Academic Search

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

Ioannis X. Tsiros; Ioannis F. Dimopoulos

2003-01-01

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

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

176

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

177

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

PubMed

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

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

2014-04-01

178

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

2009-01-01

179

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

180

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

181

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

USGS Publications Warehouse

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

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

1998-01-01

182

Arctic Climate and Terrestrial Vegetation Responses During the Middle to Late Eocene and Early Oligocene: Colder Winters Preceded Cool-Down.  

NASA Astrophysics Data System (ADS)

The late Eocene to early Oligocene is recognized as an interval of substantial change in the global climate, with isotopic proxies of climate indicating a significant drop in sea surface temperatures. Other studies have shown, however that at middle latitudes that terrestrial mean annual temperature did not change significantly over this interval, and that the major change was likely a shift towards a greater range of seasonal temperatures; colder winters and warmer summers. Previous analyses of high latitude (Arctic) middle Eocene climate using both leaf physiognomic analysis and qualitative analysis of identified nearest living relatives of terrestrial floras indicated upper microthermal environments (mean annual temp. or MAT ca 10°C but perhaps as high as 15°C, coldest month mean temp. or CMMT ca 0°C) for Axel Heiberg Island in the Arctic Archipelago, but did not address precipitation nor provide data on the Eocene-Oligocene transition in the Arctic. Presented here are new estimates of temperature and precipitation (annual and season amounts) for the Arctic based on NLR analysis of terrestrial plant palynomorphs (spores and pollen) from the ODP 913B and 985 cores from near Greenland. The record of climate for the Greenland cores show a similar climate in the middle Eocene to that previously estimated for Axel Heiberg Island further to the west, with MAT 10- 15°C but with CMMT >5°C. Precipitation was high (mean annual precip. or MAP >180 cm/yr), although with large uncertainties attached to the estimate. The climate proxy record for the late Eocene to early Oligocene shows a lack of change in MAT and MAP over the time interval. Consistent with other published records at middle latitudes, however, winter temperatures (as CMMT) show greater variability leading up to the E-O boundary, and consistently cooler values in the early Oligocene (CMMT <5°C) than recorded for most of the middle to late Eocene record (CMMT >5°C). Plant groups sensitive to freezing such as palms and the floating water fern Azolla were present in the warm parts of the record, but are absent from the latest Eocene and early Oligocene record. These data provide further evidence that the primary change in the global climate system in the E-O transition was a shift towards more extreme seasonal temperature ranges, rather than a drop in the mean temperature.

Greenwood, D. R.; Eldrett, J.

2006-12-01

183

Modeling early Paleogene climate: From the top of the atmosphere to the bottom of the ocean  

NASA Astrophysics Data System (ADS)

This dissertation addresses critical issues in early Paleogene paleoclimatology. This study's goal is to develop a more general and deeper understanding of climate by focusing on a time interval for which climate proxies and models have consistently disagreed. Climate proxies provide intriguing evidence of a ``greenhouse'' early Paleogene world: greenhouse gas (GHG) concentrations were higher than modern, midlatitude continental interiors were above freezing year-round, crocodiles lived at high latitudes, and vertical and meridional oceanic thermal gradients were small. The geologic record indicates that the climate system's response to increased GHG concentrations is to warm the poles and deep oceans and increase winter temperatures without raising tropical sea surface temperatures (SSTs), counter to every existing theory and model. Results from the uncoupled atmospheric general circulation model (GCM) experiments described in Part I demonstrate that (1)changes to land surface characteristics have important consequences at regional but not larger scales; (2)specification of warm polar SSTs implies approximately double modern ocean heat transport and does little to warm continental interiors during winter; (3)midlatitude continental interior temperatures are at least as sensitive-if not more-to changes in tropical SSTs as to extratropical SSTs; (4)testable predictions for past wind-driven ocean currents can be made from existing atmospheric GCM output. Results from Part II demonstrate that (1)a fully coupled GCM can be efficiently integrated to equilibrium for both a ``degraded'' modern case and an early Paleogene case; (2)the early Paleogene simulation produces temperature gradients very similar to modern, suggesting that it is unlikely that increased meridional heat transport caused early Paleogene small temperature gradients; (3)this simulation produces unrealistically cold continental interior temperatures, showing that a complete treatment of the ocean does not solve the equable climate ``problem'' (4)atmospheric transport statistics, residual heat budgets, radiation budgets, and precipitation patterns remain virtually unchanged between the modern and early Paleogene case. The degree to which the early Paleogene simulation produces climate statistics that are very similar to modern, despite drastically changed initial and boundary conditions, raises serious questions about climate models' ability to reproduce climates demonstrably different than modern.

Huber, Matthew

184

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

185

Comets and Terrestrial Magnetic Storms  

Microsoft Academic Search

A recent theory of the authors attributed terrestrial magnetic storms and auroral displays to the effect of unusual flares of ultra-violet light from the sun falling upon the terrestrial atmosphere. Such flares would be expected to cause changes in comets, and therefore comet changes should be closely connected with magnetic storms. This connection is supported by the evidence brought out

H. B. Maris; E. O. Hulburt

1929-01-01

186

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

187

Middle atmosphere electrodynamics: Report of the Workshop on the Role of the Electrodynamics of the Middle Atmosphere on Solar Terrestrial Coupling  

NASA Technical Reports Server (NTRS)

The middle atmosphere (MA), which is defined as the region bounded below by the tropopause near 10 km and above by the mesopause near 90 to 100 km, is regarded as a passive medium through which electric fields and currents are transmitted from sources above and below. A scientific background is given for: sources of MA electric fields; MA conductivity and currents; and MA plasma characteristics. Recommendations are given for research in MA electrodynamics in the following areas: (1) MA electrodynamical parameters; (2) models and supportive laboratory measurements; and (3) investigation of specific problems in the coupled systems.

1979-01-01

188

Terrestrials Dwarf Planets  

E-print Network

Terrestrials Gas Giants Ice Giants Dwarf Planets The Solar System #12;Neptune Uranus Saturn Jupiter & Helium atmospheres. #12;The Dwarf Planets are a new class of Solar System objects defined by the IAU Dwarf planets can have eccentric and highly inclined orbits. #12;The Solar System has 7 Giant Moons

Gaudi, B. Scott

189

GLOBAL TERRESTRIAL CARBON CYCLE  

EPA Science Inventory

There is great uncertainty with regard to the future role of the terrestrial biosphere in the global carbon cycle, arising from both an inadequate understanding of current pools and fluxes as well as the potential effects of rising atmospheric concentrations of CO, on natural eco...

190

Climatic consequences of very high CO2 levels in Earth's early atmosphere  

NASA Technical Reports Server (NTRS)

Earth has approximately 60 bars of carbon dioxide tied up in carbonate rocks, or roughly 2/3 the amount of CO2 of the atmosphere of Venus. Two different lines of evidence, one based on thermodynamics and the other on geochemical cycles, indicate that a substantial fraction of thes CO2 may have resided in the atmosphere during the first few hundred million years of the Earth's history. A natural question which arises is whether this much CO2 would have resulted in a runaway greenhouse effect. One dimensional radiative/convective model calculations presented showed that the surface temperature of a hypothetical primitive atmosphere containing 20 bars of CO2 was less than 100 C; thus no runaway greenhouse effect would have occurred. The climatic stability of the early atmosphere is a consequence of three factors: reduced solar luminosity at that time, an increase in planetary albedo caused by Rayleigh scattering by CO2, and the stabilizing effects of a moist convection. The latter two factors are sufficient to prevent a CO2 induced runaway greenhouse effect on the present Earth as well, for CO2 levels up to 100 bars. Further studies are being undertaken to determine whether a runaway greenhouse effect could have occurred during the latter stages of the accretion process and, if so, whether it would have collapsed one the influx of material slowed down.

Katsing, J. F.

1986-01-01

191

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

E-print Network

Wet surface and dense atmosphere on early Mars suggested by the bomb sag at Home Plate, Mars Spirit observation of a bomb sag produced by an explosive volcanic eruption to infer the atmospheric) of bomb sags, 2) the morphology of the impact crater, and 3) the penetration depth of the clast

Kite, Edwin

192

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

NASA Technical Reports Server (NTRS)

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

Carr, Michael H.

1989-01-01

193

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

NASA Astrophysics Data System (ADS)

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

Carr, M. H.

1989-06-01

194

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

195

A New Source Model of Non-Tidal Mass Variability in Atmosphere, Oceans, Terrestrial Hydrosphere, and the Solid Earth for Simulation Studies of Future Satellite Gravity Missions  

NASA Astrophysics Data System (ADS)

The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of various simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series. Basic requirement for all these simulations are realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth, as a source model for the orbit computations and assess the performance of the gravity field retrieval. For such simulations, a suitable source model is required to represent (i) high-frequency (~ daily) redistribution, for example, in the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. In parallel, (ii) low-frequency (weekly to monthly) variability needs to be modelled with realistic amplitudes, particularly at small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes currently not observable. The new source model presented in this study attempts to fulfil both requirements: Based on ECMWF's recent atmospheric reanalysis ERA Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic (SH) coefficients of the mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers,as well as the solid Earth. Simulated features range from high temporal (6 hours) to long-term (inter-annual) with a spatial resolution of SH degree and order 180, encompassing a a period of 12 years. Associated with the source model, a de-aliasing model for atmospheric and oceanic high-frequency variability is available with augmented errors for a more realistic description of the process of the gravity field retrieval. Several features of this new dataset will be highlighted in this presentation in order to provide guidance for its application in upcoming future mission simulation studies.

Dobslaw, Henryk; Bergmann-Wolf, Inga; Dill, Robert; Klemann, Volker; Kusche, Jürgen; Sasgen, Ingo; Thomas, Maik

2014-05-01

196

Direct evidence of late Archean to early Proterozoic anoxic atmosphere from a product of 2.5 Ga old weathering  

E-print Network

Direct evidence of late Archean to early Proterozoic anoxic atmosphere from a product of 2.5 Ga old paleosol developed on Archean granite near Pronto mine, Canada, we found that Ce-rich rhabdophane formed report the ¢rst ¢nding of a direct product of late Archean to early Proterozoic weathering, and dis- cuss

Utsunomiya, Satoshi

197

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

PubMed Central

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

Boyce, C. Kevin; Zwieniecki, Maciej A.

2012-01-01

198

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

2012-06-26

199

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

200

Coincident High Radiocarbon Reservoir Age of North Atlantic Surface Ocean and Atmospheric ?14C Increase During Early Younger Dryas Cold Period  

NASA Astrophysics Data System (ADS)

The radiocarbon reservoir age of high latitude North Atlantic Ocean surface water is expected to vary according to changes in North Atlantic Deep Water (NADW) production. Here, we present a surface water radiocarbon reservoir age record of the high latitude western North Atlantic for the deglacial period via the use of fossil cold- water corals, and combine these results with published coexisting marine and terrestrial dated deposits, and Vedde ash radiocarbon dates. The reservoir age of high latitude North Atlantic surface waters was computed from the radiocarbon age difference between our atmospheric radiocarbon record (http://radiocarbon.LDEO.columbia.edu) and marine radiocarbon data. The reconstructed high North Atlantic Ocean surface reservoir age record shows modern values (400 ± 150 year, n = 17) during the Bolling and Allerod warm period, but increased reservoir ages (630 ± 80 year, n = 7) during the entire Younger Dryas (YD) cold episode. The reservoir age then decreased to 270 ± 20 year (n = 2) at the Preboreal/YD transition, although the dates are too sparse to be confident in this estimate. We are not able to resolve the timing of the transition in increased reservoir age from the mid-Allerod to the YD due to relatively small change and correspondingly large uncertainty in the estimates. The atmospheric ?14C record derived from our atmospheric radiocarbon record displays a 40 per mil increase from 12800 to 12700 cal year BP, coincident with the high reservoir age in the early YD cold event. Intrusion of 14C depleted Antarctic Intermediate Water (AAIW) to the high latitude North Atlantic and reduction of North Atlantic Deep Water (NADW) formation are possible causes for coincidental shifts to high reservoir ages in the North Atlantic surface ocean and increased atmospheric ?14C during the beginning of the YD event.

Cao, L.; Fairbanks, R. G.; Mortlock, R. A.

2006-12-01

201

Impact of improved atmospheric forcing data and soil-vegetation parameters in terrestrial hydrologic modeling over West Africa  

NASA Astrophysics Data System (ADS)

Several recent studies have shown the importance of land surface-atmosphere coupling in the monsoon system of the West Africa. The African Monsoon Multidisciplinary Analysis (AMMA) has provided an opportunity to investigate model deficiencies in land surface processes by providing high-resolution datasets. In participation with the AMMA Land Surface Model Intercomparison Project (ALMIP2), a global land surface model, the Minimal Advanced Treatments of Surface Interaction and Runoff (MATSIRO), is regionalized for conducting a high space-time resolution experiment (0.05°, 30 minutes). Multi-year offline simulations using improved rainfall datasets derived from local rain gauges and radar-based products are compared with relative coarse resolution satellite precipitation products, such as Tropical Rainfall Measuring Mission (TRMM; 0.25°, 3 hourly) and Global Satellite Mapping of Precipitation (GSMaP; 0.1°, hourly) to better understand the effect of precipitation on simulated hydrological responses. Sensitivity experiments are also conducted by incorporating more refined distributions of soil-vegetation parameters accounting for natural grid variability to identify how soil properties and interannual vegetation variability are significantly related to water and energy balances in West Africa. Further examination of individual soil parameter and vegetation type is also performed to identify their proper specification in land surface parameterization schemes. Simulations of surface fluxes, soil temperature and soil moisture in dry months and wet months are verified separately by using observations from the AMMA-CATCH observing system as well as several satellite-based products. In general, this study demonstrates that improved forcing and representation of soil-vegetation parameters can improve land surface model simulations from seasonal to interannual time scale.

HE, X.; Kim, H.; Yeh, P. J.; Oki, T.

2012-12-01

202

Workshop on Oxygen in the Terrestrial Planets  

NASA Technical Reports Server (NTRS)

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using

2004-01-01

203

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

204

Terrestrial sequestration  

ScienceCinema

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

Charlie Byrer

2010-01-08

205

Terrestrial sequestration  

SciTech Connect

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

Charlie Byrer

2008-03-10

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

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

Microsoft Academic Search

Macrofossil wood in two European sections representing the Toarcian (Early Jurassic) Oceanic Anoxic Event (OAE) have previously been shown to exhibit a large (~ -6 to -7 %) shift in d13C values which has been interpreted as a massive and geologically short-lived perturbation to the global carbon cycle. This interpretation has recently been challenged on the basis of a compilation

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

2005-01-01

208

Combined 147,146Sm-143,142Nd constraints on the longevity and residence time of early terrestrial crust  

E-print Network

). The AGC does not have the same decoupled Nd-Hf isotope systematics as these other two terranes, which have been attributed to the crystallization of an early magma ocean. The Acasta signature rather is ascribed to the formation of Hadean crust...

Roth, Antoine S.G; Bourdon, Bernard; Mojzsis, Stephen J.; Rudge, John F.; Guitreau, Martin; Blichert-Toft, Janne

2014-06-10

209

The (146,147)Sm-(142,143)Nd systematics of early terrestrial differentiation and the lost continents of the early Earth  

NASA Technical Reports Server (NTRS)

The very early history of the Earth has been one of the great enduring puzzles in the history of geology. We report evidence which clearly can be described as a vestige of a beginning, because the evidence that we report cannot be interpreted in any other way except as a geochemical signal of processes active in the very early history of the Earth. The evidence itself is a very small anomaly in the abundance of SM-146. The primary aims of this study were to: (1) verify the existence of the 'lost continents' of the Hadean era; and (2) determine their mean age.

Harper, Charles L., Jr.; Jacobsen, Stein B.

1992-01-01

210

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

211

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

212

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

213

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

214

The terrestrial silica pump.  

PubMed

Silicon (Si) cycling controls atmospheric CO(2) concentrations and thus, the global climate, through three well-recognized means: chemical weathering of mineral silicates, occlusion of carbon (C) to soil phytoliths, and the oceanic biological Si pump. In the latter, oceanic diatoms directly sequester 25.8 Gton C yr(-1), accounting for 43% of the total oceanic net primary production (NPP). However, another important link between C and Si cycling remains largely ignored, specifically the role of Si in terrestrial NPP. Here we show that 55% of terrestrial NPP (33 Gton C yr(-1)) is due to active Si-accumulating vegetation, on par with the amount of C sequestered annually via marine diatoms. Our results suggest that similar to oceanic diatoms, the biological Si cycle of land plants also controls atmospheric CO(2) levels. In addition, we provide the first estimates of Si fixed in terrestrial vegetation by major global biome type, highlighting the ecosystems of most dynamic Si fixation. Projected global land use change will convert forests to agricultural lands, increasing the fixation of Si by land plants, and the magnitude of the terrestrial Si pump. PMID:23300825

Carey, Joanna C; Fulweiler, Robinson W

2012-01-01

215

The Terrestrial Silica Pump  

PubMed Central

Silicon (Si) cycling controls atmospheric CO2 concentrations and thus, the global climate, through three well-recognized means: chemical weathering of mineral silicates, occlusion of carbon (C) to soil phytoliths, and the oceanic biological Si pump. In the latter, oceanic diatoms directly sequester 25.8 Gton C yr?1, accounting for 43% of the total oceanic net primary production (NPP). However, another important link between C and Si cycling remains largely ignored, specifically the role of Si in terrestrial NPP. Here we show that 55% of terrestrial NPP (33 Gton C yr?1) is due to active Si-accumulating vegetation, on par with the amount of C sequestered annually via marine diatoms. Our results suggest that similar to oceanic diatoms, the biological Si cycle of land plants also controls atmospheric CO2 levels. In addition, we provide the first estimates of Si fixed in terrestrial vegetation by major global biome type, highlighting the ecosystems of most dynamic Si fixation. Projected global land use change will convert forests to agricultural lands, increasing the fixation of Si by land plants, and the magnitude of the terrestrial Si pump. PMID:23300825

Carey, Joanna C.; Fulweiler, Robinson W.

2012-01-01

216

XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape  

PubMed Central

Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ?0.24?AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ?1.0×1025 s?1 to ?5.3×1030 s?1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ?0.4 Earth ocean equivalent amounts of hydrogen (EOH) to <3 EOH and usually is several times smaller in comparison to the thermal atmospheric escape rates. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1030–1048. PMID:24283926

Lammer, Helmut; Holmstrom, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Gudel, Manuel; Hanslmeier, Arnold

2013-01-01

217

Earth's early atmosphere as seen from carbon and nitrogen isotopic analysis of Archean sediments  

NASA Technical Reports Server (NTRS)

The origin and evolution of the Earth's early atmosphere has long been a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of stromatolite deposits (Precambrian Paleobiology Research Group) has extended our knowledge of Archean ecosystems. It has been shown that many stromatolite deposits have undergone negligible alteration since their time of formation. The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archiean sediments and the observation that the 3.3 b.y. old Barberton cherts have remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of the volatile constituents present at their time of formation. Of primary interest to this study was the possibility that the stromatolites and other Archean sediments might retain a vestige of the atmosphere and thus afford an indication of the variations in carbon dioxide and nitrogen isotopic compositions with time. A suite of essentially unaltered Archean stromatolites and the cherts of different ages and geologic sites have been analyzed for their trapped carbon dioxide and nitrogen compositions by the stepped combustion extraction tech nique utilizing static mass spectrometers for the isotope measurements.

Gibson, E. K., Jr.; Carr, L. P.; Gilmour, I.; Pillinger, C. T.

1986-01-01

218

Climate forced atmospheric CO 2 variability in the early Holocene: A stomatal frequency reconstruction  

NASA Astrophysics Data System (ADS)

The dynamic climate in the Northern Hemisphere during the early Holocene could be expected to have impacted on the global carbon cycle. Ice core studies however, show little variability in atmospheric CO 2. Resolving any possible centennial to decadal CO 2 changes is limited by gas diffusion through the firn layer during bubble enclosure. Here we apply the inverse relationship between stomatal index (measured on sub-fossil leaves) and atmospheric CO 2 to complement ice core records between 11,230 and 10,330 cal. yr BP. High-resolution sampling and radiocarbon dating of lake sediments from the Faroe Islands reconstruct a distinct CO 2 decrease centred on ca. 11,050 cal. yr BP, a consistent and steady decline between ca. 10,900 and 10,600 cal. yr BP and an increased instability after ca. 10,550 cal. yr BP. The earliest decline lasting ca. 150 yr is probably associated with the Preboreal Oscillation, an abrupt climatic cooling affecting much of the Northern Hemisphere a few hundred years after the end of the Younger Dryas. In the absence of known global climatic instability, the decline to ca. 10,600 cal. yr BP is possibly due to expanding vegetation in the Northern Hemisphere. The increasing instability in CO 2 after 10,600 cal. yr BP occurs during a period of increasing cooling of surface waters in the North Atlantic and some increased variability in proxy climate indicators in the region. The reconstructed CO 2 changes also show a distinct similarity to indicators of changing solar activity. This may suggest that at least the Northern Hemisphere was particularly sensitive to changes in solar activity during this time and that atmospheric CO 2 concentrations fluctuated via rapid responses in climate.

Jessen, C. A.; Rundgren, M.; Björck, S.; Muscheler, R.

2007-06-01

219

Combined147,146Sm-143,142Nd constraints on the longevity and residence time of early terrestrial crust  

NASA Astrophysics Data System (ADS)

silicate differentiation controlled the composition of Earth's oldest crust. Inherited 142Nd anomalies in Archean rocks are vestiges of the mantle-crust differentiation before ca. 4300 Ma. Here we report new whole-rock 147,146Sm-143,142Nd data for the Acasta Gneiss Complex (AGC; Northwest Territories, Canada). Our 147Sm-143Nd data combined with literature data define an age of 3371 ± 141 Ma (2 SD) and yield an initial ?143Nd of -5.6 ± 2.1. These results are at odds with the Acasta zircon U-Pb record, which comprises emplacement ages of 3920-3960 Ma. Ten of our thirteen samples show 142Nd deficits of -9.6 ± 4.8 ppm (2 SD) relative to the modern Earth. The discrepancy between 142Nd anomalies and a mid-Archean 147Sm-143Nd age can be reconciled with Nd isotope reequilibration of the AGC during metamorphic perturbations at ca. 3400 Ma. A model age of ca. 4310 Ma is derived for the early enrichment of the Acasta source. Two compositional end-members can be identified: a felsic component with 142Nd/144Nd identical to the modern Earth and a mafic component with 142Nd/144Nd as low as -14.1 ppm. The ca. 4310 Ma AGC source is ˜200 Myr younger than those estimated for Nuvvuagittuq (northern Québec) and Isua (Itsaq Gneiss Complex, West Greenland). The AGC does not have the same decoupled Nd-Hf isotope systematics as these other two terranes, which have been attributed to the crystallization of an early magma ocean. The Acasta signature rather is ascribed to the formation of Hadean crust that was preserved for several hundred Myr. Its longevity can be linked to 142Nd evolution in the mantle and does not require slow mantle stirring times nor modification of its convective mode.

Roth, Antoine S. G.; Bourdon, Bernard; Mojzsis, Stephen J.; Rudge, John F.; Guitreau, Martin; Blichert-Toft, Janne

2014-06-01

220

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

221

Terrestrial Exoplanet Light Curves  

E-print Network

The phase or orbital light curves of extrasolar terrestrial planets in reflected or emitted light will contain information about their atmospheres and surfaces complementary to data obtained by other techniques such as spectrosopy. We show calculated light curves at optical and thermal infrared wavelengths for a variety of Earth-like and Earth-unlike planets. We also show that large satellites of Earth-sized planets are detectable, but may cause aliasing effects if the lightcurve is insufficiently sampled.

Eric Gaidos; Nicholas Moskovitz; Darren M. Williams

2005-11-23

222

A simplified model for calculating atmospheric radionuclide transport and early health effects from nuclear reactor accidents  

SciTech Connect

During certain hypothetical severe accidents in a nuclear power plant, radionuclides could be released to the environment as a plume. Prediction of the atmospheric dispersion and transport of these radionuclides is important for assessment of the risk to the public from such accidents. A simplified PC-based model was developed that predicts time-integrated air concentration of each radionuclide at any location from release as a function of time integrated source strength using the Gaussian plume model. The solution procedure involves direct analytic integration of air concentration equations over time and position, using simplified meteorology. The formulation allows for dry and wet deposition, radioactive decay and daughter buildup, reactor building wake effects, the inversion lid effect, plume rise due to buoyancy or momentum, release duration, and grass height. Based on air and ground concentrations of the radionuclides, the early dose to an individual is calculated via cloudshine, groundshine, and inhalation. The model also calculates early health effects based on the doses. This paper presents aspects of the model that would be of interest to the prediction of environmental flows and their public consequences.

Madni, I.K. [Brookhaven National Lab., Upton, NY (United States); Cazzoli, E.G.; Khatib-Rahbar, M. [Energy Research, Inc., Rockville, MD (United States)

1995-11-01

223

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  

E-print Network

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 ...

Zhuang, Qianlai.

224

Carbon dioxide on the early earth  

Microsoft Academic Search

This paper uses arguments of geochemical mass balance to arrive at an estimate of the partial pressure of carbon dioxide in the terrestrial atmosphere very early in earth history. It appears that this partial pressure could have been as large as 10 bars. This large estimate depends on two key considerations. First, volatiles were driven out of the interior of

J. C. G. Walker

1985-01-01

225

Depositional styles of Early Ediacaran terrestrial volcanosedimentary succession in Gebel El Urf area, North Eastern Desert, Egypt  

NASA Astrophysics Data System (ADS)

Located 100 km northwest of Hurghada, the volcanosedimentary successions of Gebel El Urf is exposed between latitude 27° 45' 30? and 27° 51' 00? N and longitude 32° 49' 00? and 32° 59' 00? E. The volcanosedimentary successions of Gebel El Urf crop out in an area dominated by different Late Proterozoic plutonic complexes. Both, erosional and intrusive contacts with different granitoid units have been identified. Two SHRIMP ages have been obtained from crystal-rich and lithic-poor ignimbrites yielding 615 ± 4 and 616.0 ± 5.4 Ma placing the evolution of the inter-montane basins, described here, into the Early Ediacaran. In the Gebel El Urf area, a southeastward dipping succession (Gebel El Urf Succession, GUS) of ca. 2000 m thickness rests on coarse-grained granite with an erosional unconformity. Another succession present in the area (Wadi Kefri Succession, WKS) represents volcanogenic sediments which exhibit degrees of metamorphic overprint. In places, it is presumed to be older than GUS. For the GUS, 14 lithofacies types have been differentiated and grouped to seven lithofacies associations. Subdivided into four depositional phases, GUS starts with a thick, massive and clast-supported conglomerate of alluvial fan facies (well-rounded clasts up to 100 cm). GUS continues with pelitic to sandy-turbiditic lacustrine and sandy braided river deposits with occasional volcanic glassy fragments (now illite) (Phase 2). The upper half of the GUS is dominated by volcanic deposits, starting with a 50 m thick package of alternating ignimbrites and synvolcanic sedimentary mass flow deposits, the latter related to phreatomagmatic vents (Phase 3). A thick succession of welded to non-welded ignimbrites follows, with one 20 m intercalation of coarse well-rounded conglomerates (Phase 4). Numerous SiO 2-rich and - poor dykes and sills emplaced into GUS. The GUS development displays a cycle from high to low energy sedimentation and back, under humid climatic conditions. Phase 2 was characterized by extension and down faulting of basin shoulders. Tectonic activity presumably also led to damming of the river creating a sweat water lake. Volcanism commenced with small vents during Phase 2 and terminated with voluminous eruptions in Phase 4.

Eliwa, Hassan; Breitkreuz, Christoph; Khalaf, Ibrahim; Gameel, Khaled El

2010-06-01

226

Paleoclimatic and paleoecological reconstruction of early Miocene terrestrial equatorial deposits, Rusinga and Mfangano Islands, Lake Victoria, Kenya  

NASA Astrophysics Data System (ADS)

Biological responses to climatic shifts are often studied to inform us on future anthropogenic-driven climate change. However, few of these climatic shifts occur over time scales appropriate to modern change and few occur with biota similar to modern. The Miocene Climatic Optimum is an ideal interval to study because of its rapid duration and because it occurred during the rise and proliferation of apes. The sediments on Rusinga and Mfangano Islands, Lake Victoria, Kenya were deposited between 18 and 20 Ma and record a changing equatorial climate just prior to the Miocene Climate Optimum. This location also offers an opportunity to use multiple proxies to constrain climate and landscape, including paleosol geochemistry, paleobotany and paleontology. Additionally, due to the rich fossil preservation on the islands, climatic shifts are framed within the context of early caterrhine evolution. Here, we report a climate shift recorded through three time slices spanning two formations over ~2 myr. The oldest unit, the Wayando Formation, records an arid, probably open ecosystem with pedogenic calcite rhizoliths, a high groundwater table, poorly-formed paleosols and permineralized sedges. The middle time slice, the Grit Member-Fossil Bed Member contact of the Hiwegi Formation, shows evidence of a local saline lake, with desiccation features, satin-spar after gypsum deposits and salt hoppers. Paleobotanical and sedimentological data from roughly contemporaneous strata indicate a warm, highly seasonal environment that supported a mixture of woodland and forested elements across the landscape. The youngest unit, which is within the Kibanga Member of the Hiwegi Formation, displays demonstrable evidence for a closed-canopy multistoried forest with the presence of tree-stump casts and permineralized root systems within a red-brown paleosol. Within the same paleosol horizon, the dental remains of the catarrhines Proconsul and Dendropithecus have been discovered in situ. This stratum is overlain by a sandstone with preserved leaves. Bulk soil geochemistry and paleobotanical proxies suggest the climate was warm (MAT estimates range = 22.6 - 34.5 °C) and relatively wet (MAP estimates range = 700 - 2,620 mm). This study suggests that tropical Africa may have had a much more dynamic climate leading up to the Miocene Climatic Optimum than previously suggested, and underwent considerable ecosystem reorganization both before and after the Miocene Climatic Optimum.

Michel, L. A.; Peppe, D. J.; McNulty, K. P.; Driese, S. G.; Lutz, J.; Nightingale, S.; Maxbauer, D. P.; Horner, W. H.; DiPietro, L. M.; Lehmann, T.; Dunsworth, H. M.; Harcourt-Smith, W. E.; Ogondo, J.

2012-12-01

227

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

228

A comparison of lyman alpha and He lambda 10830 line structures and variations in early-type star atmospheres  

NASA Technical Reports Server (NTRS)

Line profiles were first obtained at maximum velocity separation of the spectroscopic binary Spica (alpha Vir), and then high resolution spectrophotometric images of selected features in the 1.1 micron spectrum of Comet Kohoutek were obtained in order to gain insight into the structures and variations in early-type star atmospheres.

Meisel, D. D.

1974-01-01

229

Evolution of ore deposits on terrestrial planets  

NASA Technical Reports Server (NTRS)

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.

1991-01-01

230

Filling-in of Far-Red and Near-Infrared Solar Lines by Terrestrial and Atmospheric Effects: Simulations and Space-Based Observations from SCIAMACHY and GOSAT  

NASA Technical Reports Server (NTRS)

Mapping of terrestrial vegetation fluorescence from space is of interest because it can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Space-based measurement of solar-induced chlorophyll fluorescence is challenging, because its signal is small as compared with the much larger reflectance signal. Ground- and aircraft-based approaches have made use of the dark and spectrally-wide O2-A ( approx 760 nm) and O2-B (approx 690 nm) atmospheric features to detect the weak fluorescence signal. More recently, Joiner et al. and Frankenberg et al. focused on longer-wavelength solar Fraunhofer lines that can be observed with space-based instruments such as the currently operational GOSAT. They showed that fluorescence can be detected using Fraunhofer lines away from the far-red chlorophyll-a fluorescence peak even when the surface is relatively bright. Here, we build on that work by developing methodology to correct for instrumental artifacts that produce false filling-in signals that can bias fluorescence retrievals. We also examine other potential sources of filling-in at far-red and NIR wavelengths. Another objective is to explore the possibility of making fluorescence measurements from space with lower spectral resolution instrumentation than the GOSAT interferometer. We focus on the 866nm Ca II solar Fraunhofer line. Very few laboratory and ground-based measurements of vegetation fluorescence have been reported at wavelengths longer than 800 nm. Some results of fluorescence measurements of corn leaves acquired in the laboratory using polychromatic excitation at wavelengths shorter than 665nm show that at 866 nm, the measured signal is of the order of 0.1-0.2 mW/sq m/nm/sr. In this work, we use the following satellite observations: We use SCIAMACHY channel 5 in nadir mode that covers wavelengths between 773 and 1063nm at a spectral resolution of 0.54 nm. GOSAT has two instrument packages: the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) and the Cloud and Aerosol Imager (CAI). We use TANSO-FTS band 1, which extends from approximately 758 to 775nm and we use cloud fraction derived from the CAI. We compare satellite-derived fluorescence with the Enhanced Vegetation Index (EVI), an Aqua/MODIS-derived vegetation reflectance-based index that indicates relative greenness and is used to infer photosynthetic function.

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

2012-01-01

231

Filling-in of Far-Red and Near-Infrared Solar Lines by Terrestrial and Atmospheric Effects: Simulations and Space-Based Observations from SCHIAMACHY and GOSAT  

NASA Technical Reports Server (NTRS)

Mapping of terrestrial vegetation fluorescence from space is of interest because it can potentially provide global information on the functional status of vegetation including light use efficiency and global primary productivity that can be used for global carbon cycle modeling. Space-based measurement of solar-induced chlorophyll fluorescence is challenging, because its signal is small as compared with the much larger reflectance signal. Ground- and aircraft-based approaches have made use of the dark and spectrally-wide 02-A (approx 760 nm) and O2-B (approx 690 nm) atmospheric features to detect the weak fluorescence signal. More recently, Joiner et a1. and Frankenberg et a1. focused on longer-wavelength solar Fraunhofer lines that can be observed with space-based instruments such as the currently operational GOSAT. They showed that fluorescence can be detected using Fraunhofer lines away from the far-red chlorophyll-a fluorescence peak even when the surface is relatively bright. Here, we build on that work by developing methodology to correct for instrumental artifacts that produce false filling-in signals that can bias fluorescence retrievals. We also examine other potential sources of filling-in at far-red and NIR wavelengths. Another objective is to explore the possibility of making fluorescence measurements from space with lower spectral resolution instrumentation than the GOSAT interferometer. We focus on the 866 nm Ca II solar Fraunhofer line. Very few laboratory and ground-based measurements of vegetation fluorescence have been reported at wavelengths longer than 800 mn. Some results of fluorescence measurements of corn leaves acquired in the laboratory using polychromatic excitation at wavelengths shorter than 665 nm show that at 866 nm, the measured signal is of the order of 0.1-0.2 mw/sq m/nm/sr. In this work we use the following satellite observations: We use SCIAMACHY channel 5 in nadir mode that covers wavelengths between 773 and 1063 nm at a spectral resolution of 0.54 nm. GOSAT has two instrument packages: the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS) and the Cloud and Aerosol Imager (CAI). We use TANSO-FTS band 1, which extends from approximately 758 to 775 mn and we use cloud fraction derived from the CAL We compare satellite-derived fluorescence with the Enhanced Vegetation Index (EVI), an Aqua/MODIS-derived vegetation reflectance-based index that indicates relative greenness and is used to infer photosynthetic function.

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

2012-01-01

232

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

233

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

SciTech Connect

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 feedstock availability and market potential for woody biomass was also performed. Environmental, health, safety, and socioeconomic aspects were also considered. Feasibility work included application of the Japanese technology to a site-specific biomass application in the US. The plant would use 500 tons/day of wood. The early commercialization of the dual-fluidized bed system depends on a number of factors. Two of the most important considerations are (1) bringing the technology demonstrated at Star Dust '80 to the United States market place and the economic attractiveness of the fuel gas produced as an alternative to the conventional fuels. It has been demonstrated that the dual-fluidized bed system is technically and environmentally suited to the Plattsburgh plant site application. Hence, the obstacle of a commercially demonstrated plant has been overcome. On the other hand, the cost of the fuel gas, $8.24/million Btus (10% ROI) and $12.04/million Btus (20% ROI) is not economically attractive. In order to make this plant economically attractive, several alternatives are available including: (1) building multiple facilities, (2) increasing operating efficiencies, and (3) packaged plants. 91 references, 84 figures, 77 tables. (DMC)

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

1981-01-01

234

Feasibility Study for Early Commercialization of a Modular-Unit Dual Fluidized-Bed System for Converting Terrestrial Biomass into Alternate Fuels. Final Report.  

National Technical Information Service (NTIS)

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 investig...

D. E. Doner, J. A. Wagner, M. Carmack, R. C. Bailie, R. J. Anderson

1981-01-01

235

The Martian atmosphere above great volcanoes: Early planetary Fourier spectrometer observations  

NASA Astrophysics Data System (ADS)

This work reports the first observations of the Martian atmosphere returned by the planetary Fourier spectrometer (PFS) on board of Mars express (MEX) satellite in the vicinity of the greatest volcanic domes of the planet. Two of the early MEX orbits have already covered the region of Olympus Mons and Ascraeus Mons. These measurements are very similar in terms of local time (14LT) and season ( L=337 and 342, respectively). The long wavelength channel (LWC) of the instrument works in the thermal IR (300-1500 cm -1); its data allow the simultaneous retrieval of surface temperature, integrated content of water ice and dust suspended in the atmosphere and air thermal field up to an altitude of about 50 km. Results of the code described in the companion paper by Grassi et al. for the two orbits are presented and compared with the state expected by the European Martian climate dataset v3.1. The parent global circulation model LMD-Oxford-AAS is able to take into account a wide number of physical phenomena, but the results included in EMCD are affected by a relatively coarse spatial resolution, that does not properly describe the great volcanic domes. The comparison demonstrated that observed data follow quite strictly the trends foreseen by the model in low altitude regions, while the behavior shows remarkable differences above the relief, where orography likely plays an important role. Namely, extended mid-altitude minima in air temperature fields above the summit of volcanic domes are observed. The integrated content of dust shows a minima above Olympus, as expected for a dust particle concentration that decays with height. Measurements are consistent with an exponential decay characterized by a scale height of ˜10 km. Consistently, the surface temperature presents a maxima over the dome, as expected for conditions of clearer sky. Water ice clouds are clearly detected around Ascreus Mons, with a strong asymmetry in latitude. Further comparison with the results of the thermal emission spectrometer (TES) on board of Mars global surveyor (MGS) is also provided, partially supporting our observations of air temperature fields. Possible explanation of these trends is represented by thermal circulation, driven by air heating close to the surface. If confirmed by future observations, these data can represent important constraint by PFS data to mesospheric simulation, with possible implications on the Global Circulation Models.

Grassi, D.; Fiorenza, C.; Zasova, L. V.; Ignatiev, N. I.; Maturilli, A.; Formisano, V.; Giuranna, M.

2005-08-01

236

Early evolution of the continental crust, the oxygenated atmosphere and oceans, and the heterogeneous mantle  

NASA Astrophysics Data System (ADS)

The current paradigm for the evolution of early Earth is that, only since ~2.5 Ga ago, the Earth began to: (a) form a large granitic continental crust; (b) form an oxygenated atmosphere; (c) operate oxidative weathering of rocks on land; (d) form Fe-poor, but S-, U- and Mo-rich, oceans; (e) operate large-scale transfers of elements between oceans and oceanic crust at MORs; (f) subduct the altered oceanic crust; (g) create the mantle heterogeneity, especially in the concentrations and isotopic compositions of Fe(III), Fe(II), U, Pb, alkali elements, C, S, REEs, and many other elements; (h) create chemical and isotopic variations among OIB-, OPB-, and MORB magmas, and between I- and S-type granitoid magmas; and (i) create variations in the chemical and isotopic compositions of volcanic gas. Submarine hydrothermal fluids have typically developed from seawater-rock interactions during deep (>2 km) circulation of seawater through underlying hot volcanic rocks. When the heated hydrothermal fluids ascend toward the seafloor, they mix with local bottom seawater to precipitate a variety of minerals on and beneath the seafloor. Thus, the mineralogy and geochemistry of submarine hydrothermal deposits and associated volcanic rocks can be used to decipher the chemistry of the contemporaneous seawater, which in turn indicate the chemistry of the atmosphere and the compositions and size of the continental crust. The results of mineralogical and geochemical investigations by our and other research groups on submarine hydrothermal deposits (VMS and BIF) and hydrothermally-altered submarine volcanic rocks in Australia, South Africa, and Canada, ~3.5-2.5 Ga in ages, suggest that the above processes (a)-(i) had began by ~3.5 Ga ago. Supportive evidence includes, but not restricted to, the similarities between Archean submarine rocks and modern ones in: (1) the abundance of ferric oxides; (2) the Fe(III)/Fe(I) ratios; (3) the abundance of barite; (4) the increased Li contents; (5) the increased U contents and U/Th ratios; (6) the increased Mo contents and Mo/Th ratios; (7) the presence of Ce anomalies (both positive and negative); and (8) the depletions/enrichments of sulfide-S contents. The anomalous enrichments of radiogenic Pb isotopes, found in many Archean-aged submarine volcanic rocks, also indicate that the Archean oceans were U- and O2-rich, and that a large scale transfer of U and other elements from the oceans to the oceanic crust, and to the mantle was already occurring in the Archean. Thus, through the creation of an oxygenated atmosphere, oxygenic photoautotrophs (e.g., cyanobacteria) have been influencing the geochemistry of the deep Earth and nature of volcanism since at least ~3,5 Ga ago.

Ohmoto, H.

2011-12-01

237

Effects of high CO 2 levels on surface temperature and atmospheric oxidation state of the early Earth  

Microsoft Academic Search

One-dimensional radiative-convective and photochemical models are used to examine the effects of enhanced CO2 concentrations on the surface temperature of the early Earth and the composition of the prebiotic atmosphere. Carbon dioxide concentrations of the order of 100–1000 times the present level are required to compensate for an expected solar luminosity decrease of 25–30%, if CO2 and H2O were the

James F. Kasting; James B. Pollack; David Crisp

1984-01-01

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

Pathways to Earth-Like Atmospheres. Extreme Ultraviolet (EUV)-Powered Escape of Hydrogen-Rich Protoatmospheres  

NASA Astrophysics Data System (ADS)

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.

Lammer, Helmut; Kislyakova, K. G.; Odert, P.; Leitzinger, M.; Schwarz, R.; Pilat-Lohinger, E.; Kulikov, Yu. N.; Khodachenko, M. L.; Güdel, M.; Hanslmeier, A.

2011-12-01

240

The Geology of the Terrestrial Planets  

NASA Technical Reports Server (NTRS)

The geologic history of the terrestrial planets is outlined in light of recent exploration and the revolution in geologic thinking. Among the topics considered are planet formation; planetary craters, basins, and general surface characteristics; tectonics; planetary atmospheres; and volcanism.

Carr, M. H. (editor); Saunders, R. S.; Strom, R. G.; Wilhelms, D. E.

1984-01-01

241

Climatic consequences of very high CO2 levels in Earth's early atmosphere  

Microsoft Academic Search

Earth has approximately 60 bars of carbon dioxide tied up in carbonate rocks, or roughly 2\\/3 the amount of CO2 of Venus' atmosphere. Two different lines of evidence, one based on thermodynamics and the other on geochemical cycles, indicate that a substantial fraction of this CO2 may have resulted in the atmosphere during the first few hundred million years of

J. F. Kasting

1985-01-01

242

Cooperative research in terrestrial planetary geology and geophysics  

NASA Technical Reports Server (NTRS)

This final report for the period of July 1991 to August 1994 covered a variety of topics concerning the study of Earth and Mars. The Earth studies stressed the interpretation of the MAGSAT crustal magnetic anomalies in order to determine the geological structure, mineralogical composition, magnetic nature, and the historical background of submarine features, and also featured work in the area of terrestrial remote sensing. Mars research included the early evolution of the Martian atmosphere and hydrosphere and the investigations of the large Martian impact basins. Detailed summaries of the research is included, along with lists of the publications resulting from this research.

1994-01-01

243

The abiotic fixation of nitrogen on mars and other terrestrial planets: conversion of nitrogen, through NO, into nitrate, nitrite, ammonia, and nitrous oxide  

Microsoft Academic Search

The abiotic fixation of nitrogen is critical to understanding habitability, planetary evolution and the potential origin of life on terrestrial planets such as Mars. A non-biological source of biochemically accessible nitrogen is necessary for the origin and early evolution of life. The Martian surface has become uninhabitable, in part due to loss of atmospheric gases, such as nitrogen, resulting in

David Summers; Ranor Basa; Bishun Khare; David Rodoni

2010-01-01

244

Venus: A search for clues to early biological possibilities  

NASA Technical Reports Server (NTRS)

The extensive evidence that there is no extant life on Venus is summarized. The current atmospheric environment, which is far too hostile by terrestrial standards to support life, is described. However, exobiologists are interested in the possibility of extinct life on Venus. The early history of Venus is discussed in terms of its ability to sustain life that may now be extinct.

Colin, Larry; Kasting, James F.

1992-01-01

245

3D modelling of the early martian climate under a denser CO2 atmosphere: Temperatures and CO2 ice clouds  

NASA Astrophysics Data System (ADS)

On the basis of geological evidence, it is often stated that the early martian climate was warm enough for liquid water to flow on the surface thanks to the greenhouse effect of a thick atmosphere. We present 3D global climate simulations of the early martian climate performed assuming a faint young Sun and a CO2 atmosphere with surface pressure between 0.1 and 7 bars. The model includes a detailed radiative transfer model using revised CO2 gas collision induced absorption properties, and a parameterisation of the CO2 ice cloud microphysical and radiative properties. A wide range of possible climates is explored using various values of obliquities, orbital parameters, cloud microphysic parameters, atmospheric dust loading, and surface properties. Unlike on present day Mars, for pressures higher than a fraction of a bar, surface temperatures vary with altitude because of the adiabatic cooling and warming of the atmosphere when it moves vertically. In most simulations, CO2 ice clouds cover a major part of the planet. Previous studies had suggested that they could have warmed the planet thanks to their scattering greenhouse effect. However, even assuming parameters that maximize this effect, it does not exceed +15 K. Combined with the revised CO2 spectroscopy and the impact of surface CO2 ice on the planetary albedo, we find that a CO2 atmosphere could not have raised the annual mean temperature above 0 °C anywhere on the planet. The collapse of the atmosphere into permanent CO2 ice caps is predicted for pressures higher than 3 bar, or conversely at pressure lower than 1 bar if the obliquity is low enough. Summertime diurnal mean surface temperatures above 0 °C (a condition which could have allowed rivers and lakes to form) are predicted for obliquity larger than 40° at high latitudes but not in locations where most valley networks or layered sedimentary units are observed. In the absence of other warming mechanisms, our climate model results are thus consistent with a cold early Mars scenario in which nonclimatic mechanisms must occur to explain the evidence for liquid water. In a companion paper by Wordsworth et al. we simulate the hydrological cycle on such a planet and discuss how this could have happened in more detail.

Forget, F.; Wordsworth, R.; Millour, E.; Madeleine, J.-B.; Kerber, L.; Leconte, J.; Marcq, E.; Haberle, R. M.

2013-01-01

246

The effects of zonal atmospheric currents on the spectra of rotating early-type stars  

NASA Technical Reports Server (NTRS)

We suggest the existence of zonal currents in the atmospheres of rapidly rotating stars analogous to those found in planetary atmospheres. The zonal flow is assumed to be characterized by 'thin' atmospheric, nearly geostrophic flow which does not change the gravity darkening and stellar shape determined by the underlying uniformly rotating model. The contribution that such flows make to the continuum spectra of such stars is investigated. The additional rotationally induced Doppler displacement resulting from such zonal wind belts can distort the rotationally broadened stellar lines leading to significant departures from the line profiles predicted by the classical model of rotating stars. Our estimates of the zonal flow velocity stem from the assumption of a relation between it and the latitudinal wavenumber of the zonal velocity field. It is thus possible to create barotropic atmosphere models which, in turn, enable the modeling of the stellar spectrum including important spectral lines. In addition, the radiative transfer equations for the Stokes parameters I and Q are solved for the locally plane-parallel atmospheres so that the polarization structure of the radiation field is determined. We find that the presence of zonal wind belts leads to significant changes in the photospheric polarization from those characteristic of a uniformly rotating model.

Cranmer, Steven R.; Collins, George W., II

1993-01-01

247

Thermal evolution of an early magma ocean in interaction with the atmosphere  

NASA Astrophysics Data System (ADS)

Thermal evolution of magma oceans produced by collision with giant impactors late in accretion is expected to depend on the composition and structure of the atmosphere through the greenhouse effect of CO2 and H2O released from the magma during its crystallization. In order to constrain the various cooling timescales of the system, we developed a 1D parameterized convection model of the thermal evolution of a magma ocean coupled with a 1D radiative-convective model of a primitive atmosphere. We conducted a parametric study and depicted the influence of various parameters such as the initial volatile inventories, the initial depth of the magma ocean or the radiogenic heat production rate on the cooling sequence. Our results show that the presence of a convective-radiative steam atmosphere has a strong influence on the duration of the magma ocean phase varying from a few thousand years without atmosphere to typically 1 Myr when a steam atmosphere is present. The time required for the formation of a water ocean is respectively 0.1 Myr, 1.5 Myr and 10 Myr for Mars, Earth and Venus. This time would be virtually infinite for an Earth-sized planet located closer than 0.66 AU from the Sun. Because for Mars and Earth, these times are definitely shorter than the average time between major impacts, successive water oceans could have developed on Earth and Mars during accretion, making easier the loss of their atmospheres by impact erosion. On the contrary, Venus could have remained in the magma ocean stage for most of its accretion.

Lebrun, T.; Massol, H.; Chassefiere, E.; Davaille, A. B.; Marcq, E.; Sarda, P.; Leblanc, F.; Brandeis, G.

2012-12-01

248

Carbon Dioxide Clouds at High Altitude in the Tropics and in an Early Dense Martian Atmosphere  

NASA Technical Reports Server (NTRS)

We use a time dependent, microphysical cloud model to study the formation of carbon dioxide clouds in the Martian atmosphere. Laboratory studies by Glandor et al. show that high critical supersaturations are required for cloud particle nucleation and that surface kinetic growth is not limited. These conditions, which are similar to those for cirrus clouds on Earth, lead to the formation of carbon dioxide ice particles with radii greater than 500 micrometers and concentrations of less than 0.1 cm(exp -3) for typical atmospheric conditions. Within the current Martian atmosphere, CO2 cloud formation is possible at the poles during winter and at high altitudes in the tropics during periods of increased atmospheric dust loading. In both cases, temperature perturbations of several degrees below the CO2 saturation temperature are required to nucleate new cloud particles suggesting that dynamical processes are the most common initiators of carbon dioxide clouds rather than diabatic cooling. The microphysical cloud model, coupled to a two-stream radiative transfer model, is used to reexamine the impact of CO2 clouds on the surface temperature within a dense CO2 atmosphere. The formation of carbon dioxide clouds leads to a warmer surface than what would be expected for clear sky conditions. The amount of warming is sensitive to the presence of dust and water vapor in the atmosphere, both of which act to dampen cloud effects. The radiative warming associated with cloud formation, as well as latent heating, work to dissipate the clouds when present. Thus, clouds never last for periods much longer than several days, limiting their overall effectiveness for warming the surface. The time average cloud optical depth is approximately unity leading to a 5-10 K warming, depending on the surface pressure. However, the surface temperature does not rise about the freezing point of liquid water even for pressures as high as 5 bars, at a solar luminosity of 75% the current value.

Colaprete, Anthony; Toon, Owen B.

2001-01-01

249

Nature and evolution of the early Martian atmosphere: Evidence from highland crater populations  

NASA Technical Reports Server (NTRS)

Release of water in a CO2 rich atmosphere by precipitation and channel forming processes has led to speculation on the creation of Martian carbonate deposits. On Mars water probably was not on the surface long enough to allow eroded material to concentrate, raise the pH, and induce the formation of carbonates. This suggests that the Martian primordial atmosphere could be thinner (approximately 5 bars) and still allow highland degradation to occur over a long period of time (.45 to 1.2 billion years).

Craddock, Robert A.; Maxwell, Ted A.

1992-01-01

250

The least radiogenic terrestrial leads; implications for the early Archean crustal evolution and hydrothermal–metasomatic processes in the Isua Supracrustal Belt (West Greenland)  

Microsoft Academic Search

Vein-type galenas from within metasomatized tonalitic gneiss sheets in a metamorphosed oceanic crustal sequence of the arc-outbound Isua Supracrustal Belt (ISB), West Greenland reveal the hitherto least radiogenic terrestrial lead isotope compositions. These leads deviate from commonly applied average continental crust evolution curves for lead and can be modeled by a single stage growth with starting parameters ? (238U\\/204Pb=7.70) and

Robert Frei; Minik T. Rosing

2001-01-01

251

Early evolution of the earth - Accretion, atmosphere formation, and thermal history  

NASA Technical Reports Server (NTRS)

The thermal and atmospheric evolution of the earth growing planetesimal impacts are studied. The generation of an H2O protoatmosphere is examined, and the surface temperatures are estimated. The evolution of an impact-induced H2O atmosphere is analyzed. Consideration is given to the formation time of a 'magma ocean'and internal water budgets. The thermal history of an accreting earth is reviewed. The wet convection and greenhouse effects are discussed, and the role of Fe oxidation on the evolution of an impact-induced H2O atmopshere is described. The relationship between differentiation processes and core segregation, the H2O and FeO content of the mantle, and the origin of the hydrosphere is also examined.

Abe, Yutaka; Matsui, Takafumi

1986-01-01

252

The composition of the primitive atmosphere and the synthesis of organic compounds on the early Earth  

NASA Technical Reports Server (NTRS)

The generally accepted theory for the origin of life on the Earth requires that a large variety of organic compounds be present to form the first living organisms and to provide the energy sources for primitive life either directly or through various fermentation reactions. This can provide a strong constraint on discussions of the formation of the Earth and on the composition of the primitive atmosphere. In order for substantial amounts of organic compounds to have been present on the prebiological Earth, certain conditions must have existed. There is a large body of literature on the prebiotic synthesis of organic compounds in various postulated atmospheres. In this mixture of abiotically synthesized organic compounds, the amino acids are of special interest since they are utilized by modern organisms to synthesize structural materials and a large array of catalytic peptides.

Bada, J. L.; Miller, S. L.

1985-01-01

253

Thermal evolution of an early magma ocean in interaction with the atmosphere  

NASA Astrophysics Data System (ADS)

The thermal evolution of magma oceans produced by collision with giant impactors late in accretion is expected to depend on the composition and structure of the atmosphere through the greenhouse effect of CO2 and H2O released from the magma during its crystallization. In order to constrain the various cooling timescales of the system, we developed a 1-D parameterized convection model of a magma ocean coupled with a 1-D radiative-convective model of the atmosphere. We conducted a parametric study and described the influences of the initial volatile inventories, the initial depth of the magma ocean, and the Sun-planet distance. Our results suggest that a steam atmosphere delays the end of the magma ocean phase by typically 1 Myr. Water vapor condenses to an ocean after 0.1, 1.5, and 10 Myr for, respectively, Mars, Earth, and Venus. This time would be virtually infinite for an Earth-sized planet located at less than 0.66 AU from the Sun. Using a more accurate calculation of opacities, we show that Venus is much closer to this threshold distance than in previous models. So there are conditions such as no water ocean is formed on Venus. Moreover, for Mars and Earth, water ocean formation timescales are shorter than typical time gaps between major impacts. This implies that successive water oceans may have developed during accretion, making easier the loss of their atmospheres by impact erosion. On the other hand, Venus could have remained in the magma ocean stage for most of its accretion.

Lebrun, T.; Massol, H.; ChassefièRe, E.; Davaille, A.; Marcq, E.; Sarda, P.; Leblanc, F.; Brandeis, G.

2013-06-01

254

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

255

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

E-print Network

Late Archean to Early Paleoproterozoic global tectonics, environmental change and the rise August 2005 Editor: E. Boyle Abstract Analysis of the tectonostratigraphic records of Late Archean and environmental conditions. A Late Archean tectonic cycle started at ~2.78 Ga involving the breakup of a pre

Bekker, Andrey

256

Fossil worm burrows reveal very early terrestrial animal activity and shed light on trophic resources after the end-cretaceous mass extinction.  

PubMed

The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms. PMID:23951041

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

2013-01-01

257

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. PMID:23951041

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

2013-01-01

258

Terrestrial soil pH and MAAT records based on the MBT/CBT in the southern South China Sea: implications for the atmospheric CO2 evolution in Southeast Asia  

NASA Astrophysics Data System (ADS)

Liang Dong1, Li Li1, Qianyu Li1,2, Chuanlun L. Zhang1,3 1State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China 2School of Earth and Environment Sciences, University of Adelaide, SA 5005, Australia 3Department of Marine Sciences, University of Georgia, Athens, GA 30602, USA The methylation index of branched tetraethers (MBT) and/or the cyclization ratio of branched tetraethers (CBT) are derived from the branched glycerol dialkyl Glycerol tetraethers (GDGTs) of bacterial origin and are widely used to reconstruct the terrestrial soil pH and mean annual air temperature (MAAT); however, these proxies are less frequently used in the oceanic settings. Here we provide the first high resolution records of soil pH and MAAT since the last glacial maximum based on the sedimentary core of MD05-2896 in the southern South China Sea. The MAAT record exhibited typical glacial and interglacial cycles and was consistent with the winter insolation variation. The pH values were lower (6.4-7) in the glacial time and higher (7-8.4) in the interglacial time. Changes in soil pH allowed the evaluation of changes in soil CO2 based on the atmosphere-soil CO2 balance. The results imply that the lower winter MAAT variation with a lower winter atmospheric CO2 concentration might have resulted in a higher pH in the interglacial period. Our records provide a new insight into the evolution of atmospheric CO2 between glacial and interglacial cycles in East Asia. Key words: South China Sea, MBT/CBT, b-GDGTs, MAAT, pH

Dong, L.; Li, L.; Li, Q.; Zhang, C.

2013-12-01

259

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

260

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

261

Measurements of the CO_2 15 ?m Band System Broadened by Air, N_2 and CO_2 at Terrestrial Atmospheric Temperatures  

NASA Astrophysics Data System (ADS)

In earth remote sensing, retrievals of atmospheric temperature profiles are often based on observed radiances in infrared spectral regions where emission from atmospheric CO_2 predominates. To achieve improved retrieval accuracy, systematic errors in the forward model must be reduced, especially those associated with errors in the spectroscopic line calculation. We have recorded more than 110 new high-resolution infrared spectra of the 15-?m band system of CO_2 to accurately determine line intensities, self-, air- and N_2-broadened widths and pressure-induced line shifts, along with their temperature dependences. The spectra were recorded with the Bruker IFS 120 HR Fourier transform spectrometer at Pacific Northwest National Laboratory (PNNL) and temperature-controlled sample cells. Sample temperatures were between 206K and 298K. Maximum total pressures were 15 Torr for self-broadening and 613 Torr for air- and N_2-broadening. Analysis is done using a multispectrum fitting technique to retrieve the spectroscopic parameters. Line mixing and other non-Lorentz, non-Voigt line shapes are also assessed. The resulting line parameters are compared with the HITRAN database and with other measurements. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer 96, 139-204 (2005) L.S. Rothman et al., J. Quant. Spectrosc. Radiat. Transfer, in press (2009)

Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Blake, T. A.; Sams, R. L.

2009-06-01

262

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

2014-05-01

263

A relatively reduced Hadean continental crust and implications for the early atmosphere and crustal rheology  

NASA Astrophysics Data System (ADS)

It is widely believed that the Earth was strongly reduced during its early accretion, however, the transition from the reduced state that prevailed during Earth's early period to the modern oxidized crust and mantle has never been captured by geochemical surveys on Earth materials as old as ?4.0 billion years ago. By combining available trace-elements data of igneous zircons of crustal origin, we show that the Hadean continental crust was significantly more reduced than its modern counterpart and experienced progressive oxidation till ?3.6 billions years ago. We suggest that the increase in the oxidation state of the Hadean continental crust is related to the progressive decline in the intensity of chondritic addition during the late veneer. Inputs of carbon- and hydrogen-rich chondritic materials during the formation of Hadean granitic crust must have favored strongly reduced magmatism. The conjunction of cold, wet and reduced granitic magmatism during the Hadean implies the production of methane-rich fluids, in addition to the CO- and H2-rich volcanic species produced by degassing of hot reduced basaltic melts as modified by delivered materials during the late veneer. When the late veneer events ended, magma produced by normal decompression melting of the mantle imparted more oxidizing conditions to erupted lavas and the related crust, emitting CO2- and H2O-rich gases. Our model suggests that the Hadean continental crust was possibly much weaker than present-day, facilitating intrusion of underplating magma and thus allowing faster crustal growth in the early Earth.

Yang, Xiaozhi; Gaillard, Fabrice; Scaillet, Bruno

2014-05-01

264

Polar front shift and atmospheric CO2 during the glacial maximum of the Early Paleozoic Icehouse  

PubMed Central

Our new data address the paradox of Late Ordovician glaciation under supposedly high pCO2 (8 to 22× PAL: preindustrial atmospheric level). The paleobiogeographical distribution of chitinozoan (“mixed layer”) marine zooplankton biotopes for the Hirnantian glacial maximum (440 Ma) are reconstructed and compared to those from the Sandbian (460 Ma): They demonstrate a steeper latitudinal temperature gradient and an equatorwards shift of the Polar Front through time from 55°–70° S to ?40° S. These changes are comparable to those during Pleistocene interglacial-glacial cycles. In comparison with the Pleistocene, we hypothesize a significant decline in mean global temperature from the Sandbian to Hirnantian, proportional with a fall in pCO2 from a modeled Sandbian level of ?8× PAL to ?5× PAL during the Hirnantian. Our data suggest that a compression of midlatitudinal biotopes and ecospace in response to the developing glaciation was a likely cause of the end-Ordovician mass extinction. PMID:20696937

Vandenbroucke, Thijs R. A.; Armstrong, Howard A.; Williams, Mark; Paris, Florentin; Zalasiewicz, Jan A.; Sabbe, Koen; Nolvak, Jaak; Challands, Thomas J.; Verniers, Jacques; Servais, Thomas

2010-01-01

265

Statistical equilibrium calculations for silicon in early-type model stellar atmospheres  

NASA Technical Reports Server (NTRS)

Line profiles of 36 multiplets of silicon (Si) II, III, and IV were computed for a grid of model atmospheres covering the range from 15,000 to 35,000 K in effective temperature and 2.5 to 4.5 in log (gravity). The computations involved simultaneous solution of the steady-state statistical equilibrium equations for the populations and of the equation of radiative transfer in the lines. The variables were linearized, and successive corrections were computed until a minimal accuracy of 1/1000 in the line intensities was reached. The common assumption of local thermodynamic equilibrium (LTE) was dropped. The model atmospheres used also were computed by non-LTE methods. Some effects that were incorporated into the calculations were the depression of the continuum by free electrons, hydrogen and ionized helium line blocking, and auto-ionization and dielectronic recombination, which later were found to be insignificant. Use of radiation damping and detailed electron (quadratic Stark) damping constants had small but significant effects on the strong resonance lines of Si III and IV. For weak and intermediate-strength lines, large differences with respect to LTE computations, the results of which are also presented, were found in line shapes and strengths. For the strong lines the differences are generally small, except for the models at the hot, low-gravity extreme of our range. These computations should be useful in the interpretation of the spectra of stars in the spectral range B0-B5, luminosity classes III, IV, and V.

Kamp, L. W.

1976-01-01

266

Transient climate change and net ecosystem production of the terrestrial biosphere  

E-print Network

The Terrestrial Ecosystem Model (TEM version 4.1) is applied to assess the sensitivity of net ecosystem production (NEP) of the terrestrial biosphere to transient changes in atmospheric CO2 concentration and climate in the ...

Xiao, Xiangming.; Melillo, Jerry M.; Kicklighter, David W.; McGuire, A. David.; Prinn, Ronald G.; Wang, Chien.; Stone, Peter H.; Sokolov, Andrei P.

267

Unusually strong nitric oxide descent in the Arctic middle atmosphere in early 2013 as observed by Odin/SMR  

NASA Astrophysics Data System (ADS)

The middle atmosphere was affected by an exceptionally strong midwinter stratospheric sudden warming (SSW) during the Arctic winter 2012/2013. These unusual meteorological conditions led to a breakdown of the polar vortex, followed by the reformation of a strong upper stratospheric vortex associated with particularly efficient descent of air. Measurements by the submillimetre radiometer (SMR), on board the Odin satellite, show that very large amounts of nitric oxide (NO), produced by energetic particle precipitation (EPP) in the mesosphere/lower thermosphere (MLT), could thus enter the polar stratosphere in early 2013. The mechanism referring to the downward transport of EPP-generated NOx during winter is generally called the EPP indirect effect. SMR observed up to 20 times more NO in the upper stratosphere than the average NO measured at the same latitude, pressure and time during three previous winters where no mixing between mesospheric and stratospheric air was noticeable. This event turned out to be the strongest in the aeronomy-only period of SMR (2007-present). Our study is based on a comparison with the Arctic winter 2008/2009, when a similar situation was observed. This outstanding situation is the result of the combination of a relatively high geomagnetic activity and an unusually high dynamical activity, which makes this case a prime example to study the EPP impacts on the atmospheric composition.

Pérot, K.; Urban, J.; Murtagh, D. P.

2014-08-01

268

Terrestrial Ecosystem Adaptation  

E-print Network

Terrestrial Ecosystem Adaptation Steven W. Running and L. Scott Mills RFF REPORT ............................... 16 Expected Future Ecosystem Trends ................................................................................................................................................................ 27 #12; RUNNING AND MILLS 1 Terrestrial Ecosystem Adaptation Steven W. Running and L. Scott

Mills, L. Scott

269

Terrestrial Environment (Climatic) Criteria Handbook For Use in Aerospace Vehicle Development  

NASA Technical Reports Server (NTRS)

An update of the NASA 'Terrestrial Environment (Climatic) Criteria Handbook for Use in Aerospace Vehicle Development' (NASA-HDBK-1001) is currently in the final process of completion for release in late-2004 or early 2005. The current version of the Handbook was approved by the NASA Chief Engineer in 2000 as a NASA Preferred Technical Standard. However, it was based on natural environment criteria developed mostly in the early 1990's. Therefore, a task was approved to completely update the Handbook in order to reflect the current state-of-the-art in the various terrestrial environmental climatic criteria areas. The technical areas include: Winds, atmospheric constituents, thermodynamic parameters/models/extremes, humidity, electricity, precipitation/fog/icing, cloud phenomena/cover, diffusion/toxic release, severe weather/tornado/hurricane, solar/thermal radiation, geologic hazards, and sea state. A summary of this extensive update will be presented along with some key examples of the new contents. Earlier versions of this publication have been extensively used by the aerospace community, especially program managers and design engineers for required natural terrestrial environment inputs to use in mission planning, development studies and trades, plus by those concerned with terrestrial environment descriptions for the major test ranges within the United States.

Johnson, Dale; Vaughan, William W.

2004-01-01

270

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

271

Reconstruction of atmospheric CO 2 during the early middle Eocene by application of a gas exchange model to fossil plants from the Messel Formation, Germany  

Microsoft Academic Search

In this study, atmospheric CO2 during the early middle Eocene (~ 47Ma) is reconstructed using fossil plants from the Messel Formation close to Darmstadt, Germany. CO2 concentration is calculated using a mechanistic model of gas exchange which optimizes CO2 uptake by photosynthesis against water vapor loss by transpiration, a strategy that is commonly realized in land plants. Input data for

M. Grein; W. Konrad; V. Wilde; T. Utescher; A. Roth-Nebelsick

2011-01-01

272

Identification of Terrestrial Reflectance From Remote Sensing  

NASA Technical Reports Server (NTRS)

Correcting for atmospheric effects is an essential part of surface-reflectance recovery from radiance measurements. Model-based atmospheric correction techniques enable an accurate identification and classification of terrestrial reflectances from multi-spectral imagery. Successful and efficient removal of atmospheric effects from remote-sensing data is a key factor in the success of Earth observation missions. This report assesses the performance, robustness and sensitivity of two atmospheric-correction and reflectance-recovery techniques as part of an end-to-end simulation of hyper-spectral acquisition, identification and classification.

Alter-Gartenberg, Rachel; Nolf, Scott R.; Stacy, Kathryn (Technical Monitor)

2000-01-01

273

Origin of the Ocean on the Earth: Early Evolution of Water D/H in a Hydrogen-rich Atmosphere  

E-print Network

The origin of the Earth's ocean has been discussed on the basis of deuterium/hydrogen ratios (D/H) of several sources of water in the solar system. The average D/H of carbonaceous chondrites (CC's) is known to be close to the current D/H of the Earth's ocean, while those of comets and the solar nebula are larger by about a factor of two and smaller by about a factor of seven, respectively, than that of the Earth's ocean. Thus, the main source of the Earth's ocean has been thought to be CC's or adequate mixing of comets and the solar nebula. However, those conclusions are correct only if D/H of water on the Earth has remained unchanged for the past 4.5 Gyr. In this paper, we investigate evolution of D/H in the ocean in the case that the early Earth had a hydrogen-rich atmosphere, the existence of which is predicted by recent theories of planet formation no matter whether the nebula remains or not. Then we show that D/H in the ocean increases by a factor of 2-9, which is caused by the mass fractionation during atmospheric hydrogen loss, followed by deuterium exchange between hydrogen gas and water vapor during ocean formation. This result suggests that the apparent similarity in D/H of water between CC's and the current Earth's ocean does not necessarily support the CC's origin of water and that the apparent discrepancy in D/H is not a good reason for excluding the nebular origin of water.

Hidenori Genda; Masahiro Ikoma

2007-09-13

274

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

275

Early Paleogene Arctic terrestrial ecosystems affected by the change of polar hydrology under global warming: Implications for modern climate change at high latitudes  

Microsoft Academic Search

Our understanding of both the role and impact of Arctic environmental changes under the current global warming climate is\\u000a rather limited despite efforts of improved monitoring and wider assessment through remote sensing technology. Changes of Arctic\\u000a ecosystems under early Paleogene warming climate provide an analogue to evaluate long-term responses of Arctic environmental\\u000a alteration to global warming. This study reviews Arctic

Qin Leng; Gaytha A. Langlois; Hong Yang

2010-01-01

276

Long-term solar-terrestrial observations  

NASA Astrophysics Data System (ADS)

In the fall of 1985, the Committee on Solar-Terrestrial Research (CSTR) created a panel to study the requirements for long-term monitoring and archiving of solar-terrestrial data. The panel comprised specialists in all four areas that constitute solar-terrestrial science: the sun, interplanetary medium, magnetosphere-thermosphere-ionosphere, and upper atmosphere. It interviewed many individuals from the solar-terrestrial monitoring and data archiving communities, along with administrators and directors from appropriate government agencies. It circulated nearly 500 questionnaires to obtain information and opinions from the broader community to learn which observational data should be considered essential over the long term to support the operational and research needs of solar-terrestrial science. This report summarizes the panel's principal findings, and the panel's recommendations follow. A separate section listing the critical observational needs by area is presented together with the scientific rationale for each area. The recommendations are defended in terms of this explicit scientific rationale and the multifold uses of current and long-term solar-terrestrial observations for continued operational solar-terrestrial forecasts and services.

277

Soil-atmosphere fluxes of carbon monoxide during early stages of postfire succession in upland Canadian boreal forests  

NASA Astrophysics Data System (ADS)

Soil-atmosphere fluxes of carbon monoxide (CO) were investigated during BOREAS 1994 (June to September 1994) in forest sites near the northern study area (NSA) of the Boreal Ecosystem-Atmosphere Study (BOREAS). Fluxes and related ancillary data were measured for both upland black spruce (located on poorly drained clay-textured soils) and jack pine sites (well-drained sandy soils) that were in early stages of succession following stand replacement fires that occurred within 7 years of BOREAS 1994. Nearby control stands that had not burned in the past 80 years were studied for comparison. Net fluxes measured by using transparent closed chambers were generally positive at the warmer, sunlit burn sites but negative (sink activity) in the shaded, cooler control sites. Carbon monoxide uptake in controls, which was first order with respect to CO concentration, was little affected by covering the sampling chambers to exclude light. Median deposition velocities calculated from the uptake fluxes were 0.015 cm s-1 at the black spruce control site and 0.0085 cm s-1 at the jack pine control site, at the lower end of the range of values observed by others in tropical and temperate ecosystems. Daytime CO fluxes at the burn sites were generally positive (1011-1012 molecules cm-2 s-1) and were lowered when solar irradiance was excluded from the chambers by covering or when cloudiness or smoke reduced the light intensity. Net fluxes at the burn sites were controlled by competition between abiotic production, mainly at the surface, and by oxidation deeper in the soil. Abiotic production, which was attributable to photoproduction and thermal decomposition of the surface organic layer and charcoal, strongly correlated with incident solar irradiance, and thus the greatest fluxes were observed during midday. Results of these studies indicate that the locally dependent changes in boreal fire return intervals that are linked to global climate change represent an important biospheric/physical feedback that is likely to alter the biosphere-atmosphere exchange of CO.

Zepp, Richard G.; Miller, William L.; Tarr, Matthew A.; Burke, Roger A.; Stocks, Brian J.

1997-12-01

278

A Spherical Non-LTE Line-blanketed Stellar Atmosphere Model of the Early B Giant {epsilon} Canis Majoris  

SciTech Connect

We use a spherical non-LTE fully line-blanketed model atmosphere to fit the full multiwavelength spectrum, including the extreme-ultraviolet (EUV) continuum observed by the {ital Extreme} {ital Ultraviolet} {ital Explorer}, of the B2 II star {epsilon} Canis Majoris (CMa). The available spectrophotometry of {epsilon} CMa from 350 {Angstrom} to 25 {mu}m is best fitted with model parameters {ital T}{sub eff} = 21,750 K, log {ital g} = 3.5, and an angular diameter of 0.77 mas. Our best-fit model predicts a hydrogen ionizing flux, {ital q}{sub 0}, of 1.59 {times} 10{sup 21} photons cm{sup {minus}2} s{sup {minus}1} at the star`s surface and 2290 photons cm{sup {minus}2} s{sup {minus}1} at the surface of the Local Cloud. The close agreement between the model and the measured EUV flux from {epsilon} CMa is a result of the higher temperatures at the formation depths of the H i and He i Lyman continua compared with other models. The realistic model treatment of early B giants with spherical geometry and non-LTE metal line{endash}blanketing results in the prediction of significantly larger EUV fluxes compared with plane-parallel models. We find that our metal line{endash}blanketed spherical models show significantly warmer temperature structures, 1{endash}3 kK at the formation depth of the Lyman continua, and predict stronger EUV fluxes, up to a factor of 5 in the H i Lyman continuum, compared with plane-parallel atmospheres that have identical model parameters. In contrast, we find that spherical and plane-parallel models that do not include metal line blanketing are nearly identical. Our {ital T}{sub eff} = 21,000 K, log {ital g} = 3.2, spherical non-LTE model predicts more than twice as many hydrogen ionizing photons and over 200 times more neutral helium ionizing photons than a standard hydrostatic plane-parallel LTE model with the same stellar parameters. Our synthetic spectra are in reasonably good agreement with observed continuum and line fluxes from echelle spectra obtained with the Goddard High Resolution Spectrograph. While we find agreement between the absolute UV flux of {epsilon} CMa as measured by GHRS and our model atmosphere, these fluxes are {approximately}30{percent} higher in the UV than those measured by {ital IUE}, {ital OAO} {ital 2}, and {ital TD}-{ital 1}, in excess of the published errors in the absolute calibration of these data. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}

Aufdenberg, J.P. [Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85271-1504 (United States)] [Department of Physics and Astronomy, Arizona State University, Tempe, Arizona 85271-1504 (United States); Hauschildt, P.H. [Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, Georgia 30602-2451 (United States)] [Department of Physics and Astronomy and Center for Simulational Physics, University of Georgia, Athens, Georgia 30602-2451 (United States); Shore, S.N. [Department of Physics and Astronomy, Indiana University South Bend, South Bend, Indiana 46634-7111 (United States)] [Department of Physics and Astronomy, Indiana University South Bend, South Bend, Indiana 46634-7111 (United States); Baron, E. [Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019-0225 (United States)] [Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019-0225 (United States)

1998-05-01

279

A Spherical Non-LTE Line-blanketed Stellar Atmosphere Model of the Early B Giant epsilon Canis Majoris  

NASA Astrophysics Data System (ADS)

We use a spherical non-LTE fully line-blanketed model atmosphere to fit the full multiwavelength spectrum, including the extreme-ultraviolet (EUV) continuum observed by the Extreme Ultraviolet Explorer, of the B2 II star ? Canis Majoris (CMa). The available spectrophotometry of ? CMa from 350 Å to 25 ?m is best fitted with model parameters Teff = 21,750 K, log g = 3.5, and an angular diameter of 0.77 mas. Our best-fit model predicts a hydrogen ionizing flux, q0, of 1.59 × 1021 photons cm-2 s-1 at the star's surface and 2290 photons cm-2 s-1 at the surface of the Local Cloud. The close agreement between the model and the measured EUV flux from ? CMa is a result of the higher temperatures at the formation depths of the H I and He I Lyman continua compared with other models. The realistic model treatment of early B giants with spherical geometry and non-LTE metal line-blanketing results in the prediction of significantly larger EUV fluxes compared with plane-parallel models. We find that our metal line-blanketed spherical models show significantly warmer temperature structures, 1-3 kK at the formation depth of the Lyman continua, and predict stronger EUV fluxes, up to a factor of 5 in the H I Lyman continuum, compared with plane-parallel atmospheres that have identical model parameters. In contrast, we find that spherical and plane-parallel models that do not include metal line blanketing are nearly identical. Our Teff = 21,000 K, log g = 3.2, spherical non-LTE model predicts more than twice as many hydrogen ionizing photons and over 200 times more neutral helium ionizing photons than a standard hydrostatic plane-parallel LTE model with the same stellar parameters. Our synthetic spectra are in reasonably good agreement with observed continuum and line fluxes from echelle spectra obtained with the Goddard High Resolution Spectrograph. While we find agreement between the absolute UV flux of ? CMa as measured by GHRS and our model atmosphere, these fluxes are ~30% higher in the UV than those measured by IUE, OAO 2, and TD-1, in excess of the published errors in the absolute calibration of these data.

Aufdenberg, J. P.; Hauschildt, P. H.; Shore, S. N.; Baron, E.

1998-05-01

280

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

281

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

282

Terrestrial photovoltaic collector technology trends  

NASA Technical Reports Server (NTRS)

Following the path of space PV collector development in its early stages, terrestrial PV technologies based upon single-crystal silicon have matured rapidly. Currently, terrestrial PV cells with efficiencies approaching space cell efficiencies are being fabricated into modules at a fraction of the space PV module cost. New materials, including CuInSe2 and amorphous silicon, are being developed for lowering the cost, and multijunction materials for achieving higher efficiency. Large grid-interactive, tracking flat-plate power systems and concentrator PV systems totaling about 10 MW, are already in operation. Collector technology development both flat-plate and concentrator, will continue under an extensive government and private industry partnership.

Shimada, K.; Costogue, E.

1984-01-01

283

Numerical modeling of impact erosion of atmospheres: Preliminary results  

NASA Technical Reports Server (NTRS)

It is clear from the great diversity of atmospheres among the terrestrial planets that their formation and evolution must have depended on a balance among a number of different processes. One of these processes is atmospheric erosion by impacts, which may have been particularly effective on Mars. The reason is that geomorphic evidence on Mars suggests that this planet had, early in its history, dense enough atmosphere to sustain active precipitation over geologically significant periods of time. Analytic calculations indicate that neither the projectile entering the atmosphere nor the main crater ejecta can cause the lose of significant amounts of atmosphere. The vapor plume that is formed, however, expands rapidly as its internal energy is converted into kinetic energy, and may blow off the overlying atmosphere. A model of this part of the impact/atmosphere interaction predicts Mars could have lost a substantial early atmosphere by impact erosion alone. Although our more detailed calculations, which took into account the anisotropy of the atmosphere with respect to zenith angle, show that the process isn't quite as effective, they still indicate the probability of substantial atmospheric loss from Mars. The first results from 2-D hydrocode runs are discussed. These include two runs which make most of the same simplifying approximations as the analytic models, in order to compare the analytic and numerical results directly, and one run (as yet incomplete) that models the full impact.

Vickery, A. M.

1993-01-01

284

Detecting the Dusty Debris of Terrestrial Planet Formation  

E-print Network

We use a multiannulus accretion code to investigate debris disks in the terrestrial zone, at 0.7-1.3 AU around a 1 solar mass star. Terrestrial planet formation produces a bright dusty ring of debris with a lifetime of at least 1 Myr. The early phases of terrestrial planet formation are observable with current facilities; the late stages require more advanced instruments with adaptive optics.

Scott J Kenyon; Benjamin C Bromley

2004-01-16

285

Experimental investigation of anaerobic nitrogen fixation rates with varying pressure, temperature and metal concentration with application to the atmospheric evolution of early Earth and Mars.  

NASA Astrophysics Data System (ADS)

The atmosphere of the early Earth is thought to have been significantly different than the modern composition of 21% O2 and 78% N2, yet the planet has been clearly established as hosting microbial life as far back as 3.8 billion years ago. As such, constraining the atmospheric composition of the early Earth is fundamental to establishing a database of habitable atmospheric compositions. A similar argument can be made for the planet Mars, where nitrates have been hypothesized to exist in the subsurface. During the early period on Mars when liquid water was likely more abundant, life may have developed to take advantage of available nitrates and a biologically-driven Martian nitrogen cycle could have evolved. Early Earth atmospheric composition has been investigated numerically, but only recently has the common assumption of a pN2 different than modern been investigated. Nonetheless, these latest attempts fail to take into account a key atmospheric parameter: life. On modern Earth, nitrogen is cycled vigorously by biology. The nitrogen cycle likely operated on the early Earth, but probably differed in the metabolic processes responsible, dominantly due to the lack of abundant oxygen which stabilizes oxidized forms of N that drive de-nitrification today. Recent advances in evolutionary genomics suggest that microbial pathways that are relatively uncommon today (i.e. vanadium and iron-based nitrogen fixation) probably played important roles in the early N cycle. We quantitatively investigate in the laboratory the effects of variable pressure, temperature and metal concentration on the rates of anoxic nitrogen fixation, as possible inputs for future models investigating atmospheric evolution, and better understand the evolution of the nitrogen cycle on Earth. A common anaerobic methanogenic archaeal species with i) a fully sequenced genome, ii) all three nitrogenases (molybdenum, vanadium and iron-based) and iii) the ability to be genetically manipulated will be used as a model species. This species will be genetically modified to create knock-out mutants lacking one or more nitrogenase genes. These mutants will be used in variable pressure, temperature and metal-concentration experiments. Nitrogen fixation rate and nitrogenase gene expression will be measured using isotope dilution and quantitative polymerase chain reaction, respectively.

Gupta, Prateek

2012-07-01

286

Terrestrial Environment (Climatic) Criteria Handbook for Use in Aerospace Vehicle Development  

NASA Technical Reports Server (NTRS)

Aerospace Meteorology provides the identification of that aspect of meteorology that is concerned with the definition and modeling of atmospheric parameters for use in aerospace vehicle development, mission planning and operational capability assessments. One of the principal sources of this information is the NASA-HDBK-1001 "Terrestrial Environment (Climatic) Criteria Handbook for Use in Aerospace Vehicle Development'. This handbook was approved by the NASA Chief Engineer in 2000 as a NASA Preferred Technical Standard . Its technical contents were based on natural environment statistics/models and criteria developed mostly in the early 1990's. A task was approved to completely update the handbook to reflect the current state-of-the-art in the various terrestrial environment climatic areas.

Johnson, Dale L.; Vaughan, William W.

2004-01-01

287

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

288

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 the Fram Strait and causing the sea-ice extent to advance in the Nordic Seas, yielding cooler and fresher sea surface conditions. We have tested this hypothesis in an atmosphere-ocean-sea-ice coupled model of intermediate complexity (LOVECLIM). Our experiment on early Holocene Siberian Shelf flooding shows that in our model sea-ice production in the Northern Hemisphere increases (15%) and that sea-ice extent in the Northern Hemisphere increases (14%) but sea-ice export decreases (-15%) contrary to our hypothesis. The reason of this unexpected behaviour has its origin in a weakened polar vortex, induced by the land-ocean changes due to the shelf flooding, and a resulting decrease of zonality in the Nordic Seas pressure regime. Hence the winter Greenland high and the Icelandic low strengthen, yielding stronger winds on both sides of the Nordic Seas. Increased winds along the East Greenland Current support local sea-ice production and transport towards the South, resulting in a wider sea-ice cover and a southward shift of convection areas. The overall strength of the Atlantic meridional overturning circulation is reduced by 4% and the heat transport in the Atlantic basin by 7%, resulting in an annual cooling pattern over the Nordic Seas by up to -4 °C. We find that the flooding of the Siberian shelf resulting from an orbitally induced warming and related glacioeustatic sea level rise causes a Nordic Seas cooling feedback opposed to this warming.

Blaschek, M.; Renssen, H.

2013-11-01

289

Formation of early water oceans on rocky planets  

Microsoft Academic Search

Terrestrial planets, with silicate mantles and metallic cores, are likely to obtain water and carbon compounds during accretion.\\u000a Here I examine the conditions that allow early formation of a surface water ocean (simultaneous with cooling to clement surface\\u000a conditions), and the timeline of degassing the planetary interior into the atmosphere. The greatest fraction of a planet’s\\u000a initial volatile budget is

Linda T. Elkins-Tanton

2011-01-01

290

TERRESTRIAL ECOSYSTEM SIMULATOR  

EPA Science Inventory

The Terrestrial Habitats Project at the Western Ecology Division (Corvallis, OR) is developing tools and databases to meet the needs of Program Office clients for assessing risks to wildlife and terrestrial ecosystems. Because habitat is a dynamic condition in real-world environm...

291

Clouds in Planetary Atmospheres  

NASA Technical Reports Server (NTRS)

In the terrestrial atmosphere clouds are familiar as vast collections of small water drops or ice cyrstals suspended in the air. The study of clouds touches on many facets of armospheric science. The chemistry of clouds is tied to the chemistry of the surrounding atmosphere.

West, R.

1999-01-01

292

Testing the opacity and equation of state of LTE and non-LTE model atmospheres with OPAL and OP data for early-type stars  

NASA Astrophysics Data System (ADS)

Context. Complex investigations of stars are made by studying their atmospheres, evolutionary states and oscillation properties, but the opacities and equation of state are still uncertain. Aims: Compatibility of model atmospheres with internal structure of early-type stars are investigated at photospheric and sub-photospheric regions. Methods: The problem was studied quantitatively by means of diagrams that involve the Rosseland-mean opacities, temperatures, densities, and gradients of radiation pressure as functions of depth using stellar atmosphere and envelope models. Results: Two new grids of radiative-equilibrium models of atmospheres were calculated assuming the local thermodynamic equilibrium (LTE). The first one is based on Kurucz's ATLAS12 computer code implemented with the occupation probability formalism, which accounts for the destruction of loosely bound states of atoms by interactions with particles in the plasma. The second grid of models is based on monochromatic opacities and equations of state taken from the well-known international opacity project (OP). Non-LTE model atmospheres are also calculated and some aspects of the modeling are pointed out to improve agreement with ATLAS12, OP data, as well as with results of the Rogers & Iglesias OPAL opacity computing code (OPAL). The model atmospheres are also discussed by analyzing emerging fluxes of radiation. Conclusions: Commonly used LTE and non-LTE models of stellar atmospheres of early-type stars differ markedly from each other and do not fit OPAL or OP stellar envelope models at great optical depths. The results of the OP project distributed as the OPCD v 3.3 base are useful for calculating not only stellar envelopes but also fully line-blanketed LTE model atmospheres. These models have diagnostic values for studying the atomic physics used for modeling of photospheric and sub-photospheric regions of stars. The OPAL and OP opacities are markedly underestimated in comparison with the Rosseland-mean opacities taken from the Castelli & Kurucz (2003, IAU Symp., 210, 10) atmosphere models in which a new opacity bump appears at lgT ? 5.06. This additional opacity bump affects the OPAL- and OP-driving zone for stellar pulsations and therefore the new envelope models may markedly change predicted spectra of unstable oscillation modes. Differences between current non-LTE and LTE models based on the TLUSTY200 and ATLAS codes, respectively, cannot be assigned entirely to non-LTE effects, but for B stars they reflect mainly opacity effects.

Cugier, H.

2012-11-01

293

Modern Microbial Ecosystems are a Key to Understanding Our Biosphere's Early Evolution and its Contributions To The Atmosphere and Rock Record  

NASA Technical Reports Server (NTRS)

The survival of our early biosphere depended upon efficient coordination anion- diverse microbial populations. Microbial mats exhibit a 3.46-billion-year fossil record, thus they are the oldest known ecosystems. Photosynthetic microbial mats were key because, today, sunlight powers more than 99 percent of global primary productivity. Thus photosynthetic ecosystems have affected the atmosphere profoundly and have created the most pervasive, easily-detected fossils. Photosynthetic biospheres elsewhere will be most detectible via telescopes or spacecraft. As a part of the Astrobiology Institute, our Ames Microbial Ecosystems group examines the roles played by ecological processes in the early evolution of our biosphere, as recorded in geologic fossils and in the macromolecules of living cells: (1) We are defining the microbial mat microenvironment, which was an important milieu for early evolution. (2) We are comparing mats in contrasting environments to discern strategies of adaptation and diversification, traits that were key for long-term survival. (3) We have selected sites that mimic key environmental attributes of early Earth and thereby focus upon evolutionary adaptations to long-term changes in the global environment. (4) Our studies of gas exchange contribute to better estimates of biogenic gases in Earth's early atmosphere. This group therefore directly addresses the question: How have the Earth and its biosphere influenced each other over time Our studies strengthen the systematics for interpreting the microbial fossil record and thereby enhance astrobiological studies of martian samples. Our models of biogenic gas emissions will enhance models of atmospheres that might be detected on inhabited extrasolar planets. This work therefore also addresses the question: How can other biospheres be recogniZed" Our choice of field sites helps us explore Earth's evolving early environment. For example, modern mats that occupy thermal springs and certain freshwater environments experience conditions such as low O2 and sulfate and high inorganic carbon and sulfide levels that resemble those of ancient marine environments. Later in history, both biologically-induced carbonate precipitation and the trapping and binding of suspended grains of carbonate became a dominant mechanism for carbonate deposition. Modern marine carbonate platforms and alkaline offer good examples of microbiologically-induced calcification. Both marine platforms and solar salterns illustrate microbially-driven trapping and binding. We are also exploring the effects of water composition upon the exchange of biogenic gases with the atmosphere.

DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

294

Limitations of terrestrial life.  

NASA Technical Reports Server (NTRS)

Questions of the suitability of other planets in the solar system for terrestrial organisms are discussed. It is found that life forms similar to terrestrial organisms but modified to fit the prevailing conditions could exist on Venus, Mars, and Jupiter. Of these, only in the case of Jupiter is there any evidence that life would have been able to evolve. Life on Jupiter would be restricted to the clouds. It is pointed out that life may have developed on other celestial bodies in forms which are quite dissimilar to terrestrial organisms with regard to their biochemistry.

Molton, P.

1973-01-01

295

Responses of terrestrial aridity to global warming  

NASA Astrophysics Data System (ADS)

dryness of terrestrial climate can be measured by the ratio of annual precipitation (P) to potential evapotranspiration (PET), where the latter represents the evaporative demand of the atmosphere, which depends on the surface air temperature, relative humidity, wind speed, and available energy. This study examines how the terrestrial mean aridity responds to global warming in terms of P/PET using the Coupled Model Intercomparison Project phase 5 transient CO2 increase to 2 × CO2 simulations. We show that the (percentage) increase (rate) in P averaged over land is ~1.7%/°C ocean mean surface air temperature increase, while the increase in PET is 5.3%/°C, leading to a decrease in P/PET (i.e., a drier terrestrial climate) by ~3.4%/°C. Noting a similar rate of percentage increase in P over land to that in evaporation (E) over ocean, we propose a framework for examining the change in P/PET, in which we compare the change in PET over land and E over ocean, both expressed using the Penman-Monteith formula. We show that a drier terrestrial climate is caused by (i) enhanced land warming relative to the ocean, (ii) a decrease in relative humidity over land but an increase over ocean, (iii) part of increase in net downward surface radiation going into the deep ocean, and (iv) different responses of PET over land and E over ocean for given changes in atmospheric conditions (largely associated with changes in temperatures). The relative contributions to the change in terrestrial mean aridity from these four factors are about 35%, 35%, 15%, and 15%, respectively. The slight slowdown of the surface wind over both land and ocean has little impact on the terrestrial mean aridity.

Fu, Qiang; Feng, Song

2014-07-01

296

[Effects of land use change on carbon storage in terrestrial ecosystem].  

PubMed

Terrestrial ecosystem is an important carbon pool, which plays a crucial role in carbon biogeochemical cycle. Human activities such as fossil fuel combustion and land use change have resulted in carbon fluxes from terrestrial ecosystem to the atmosphere, which increased the atmospheric CO2 concentration, and reinforced the greenhouse effect. Land use change affects the structure and function of the terrestrial ecosystem, which causes its change of carbon storage. To a great extent, the change of carbon storage lies in the type of ecosystem and the change of land use patterns. The conversion of forest to agricultural land and pasture causes a large reduction of carbon storage in vegetation and soil, and the decrease of soil carbon concentration is mainly caused by the reduction of detritus, the acceleration of soil organic matter decomposition, and the destroy of physical protection to organic matter due to agricultural practices. The loss of soil organic matter appears at the early stage after deforestation, and the loss rate is influenced by many factors and soil physical, chemical and biological processes. The conversion of agricultural land and pasture to forest and many conservative agricultural practices can sequester atmospheric carbon in vegetation and soil. Vegetation can sequester large amounts of carbon from atmosphere, while carbon accumulation in soil varies greatly because of farming history and soil spatial heterogeneity. Conservative agricultural practices such as no-tillage, reasonable cropping system, and fertilization can influence soil physical and chemical characters, plant growth, quality and quantity of stubble, and soil microbial biomass and its activity, and hence, maintain and increase soil carbon concentration. PMID:14655381

Yang, Jingcheng; Han, Xingguo; Huang, Jianhui; Pan, Qingmin

2003-08-01

297

How Mars lost its atmosphere  

NASA Technical Reports Server (NTRS)

There is a widespread suspicion that Mars thin atmosphere is in some way attributable to the planet's size. Another possibility is that the atmosphere was never degassed or outgassed in the first place. I prefer escape. Hydrodynamic escape (vigorous thermal escape) and impact erosion (expulsion of atmosphere by impacts) are two processes that should have been operative early. Although in principle hydrodynamic escape could have shrunk Mars atmosphere a hundredfold while leaving the composition of the remnant atmosphere nearly unaltered, very high escape fluxes are required. The implicated escape mechanism must have been efficient, nearly non-fractionating, and vastly more potent for Mars than for Earth or Venus. Impact erosion is an appealing candidate. Noble gases are the obvious first test. Noble gases are the most volatile elements and so are the most likely to have been affected by impact erosion and the easiest to address quantitatively. Xenon in particular imposes three constraints on how Mars lost its atmosphere: (1) the very low abundance of nonradiogenic Xe abundance of nonradiogenic Xe compared to Earth, Venus, and likely meteoritic sources; (2) its nonradiogenic isotopes distinct from likely meteoritic sources; and (3) the relatively high absolute abundance of radiogenic daughter of the extinct radionuclide I-129 (half-life 17 Myr). In impact erosion, the first two become constraints on the composition, mass distribution, and orbital elements of the impactors. The third requires that Mars lost its nonradiogenic Xe early, probably before it was 100 Myr old. Impact erosion can explain Mars by any of three stories. (1) Mars in unlikely. In a sort of planetary brinkmanship, impact erosion almost removed the entire atmosphere but was arrested just in time. (2) Martian noble gases are cometary and cometary Xe is as isotopically mass fractionated as Martian and terrestrial Xe. This is most easily accomplished if a relatively thick geochemically controlled CO2 atmosphere protected trace atmophiles against escape. (3) Mars was indeed stripped of its early atmosphere but a small remnant was safely stored in the regolith, later released as a byproduct of water mobilization.

Zahnle, Kevin

1992-01-01

298

Terrestrial Impact Structures  

NASA Astrophysics Data System (ADS)

Emphasis is placed on the nature of terrestrial impact structures, the criteria for their identification, and their contribution to constraining formational processes and cratering rate estimates. The relationship of large-scale impact to Earth history is also considered.

Grieve, R. A. F.

299

Terrestrial photovoltaic measurements, 2  

NASA Technical Reports Server (NTRS)

The following major topics are discussed; (1) Terrestrial solar irradiance; (2) Solar simulation and reference cell calibration; and (3) Cell and array measurement procedures. Numerous related subtopics are also discussed within each major topic area.

1976-01-01

300

Effect of Non-local Thermodynamic Equilibrium Model Atmospheres on Photometric Amplitudes and Phases of Early B-type Pulsating Stars  

NASA Astrophysics Data System (ADS)

Amplitudes and phases of the light variation of a pulsating star in various photometric passbands contain information about the geometry of observed modes. Because oscillation spectra of early B-type main-sequence stars do not exhibit regular patterns, these observables are very often the only ones from which mode identification can be derived. Moreover, these data can yield valuable constraints on mean stellar parameters, subphotospheric convection, microphysics, and atmospheres. We study all possible sources of inaccuracy in theoretical values of the photometric observables, i.e., amplitude ratios and phase differences, of early B-type main-sequence pulsators. Here, we discuss the effects of parameters coming from both model atmospheres and linear nonadiabatic theory of stellar pulsation. In particular, we evaluate for the first time the effect of the departure from the local thermodynamic equilibrium (LTE) approximation. To this end, for non-LTE model atmospheres, we compute tables with the passband fluxes, flux derivatives over effective temperature and gravity, as well as the nonlinear limb-darkening coefficients in 12 passbands most often used. We make these tables publicly available at the Wroc?aw HELAS Web site.

Daszy?ska-Daszkiewicz, J.; Szewczuk, W.

2011-02-01

301

The Laboratory for Terrestrial Physics  

NASA Technical Reports Server (NTRS)

The Laboratory for Terrestrial Physics is dedicated to the advancement of knowledge in Earth and planetary science, by conducting innovative research using space technology. The Laboratory's mission and activities support the work and new initiatives at NASA's Goddard Space Flight Center (GSFC). The Laboratory's success contributes to the Earth Science Directorate as a national resource for studies of Earth from Space. The Laboratory is part of the Earth Science Directorate based at the GSFC in Greenbelt, MD. The Directorate itself is comprised of the Global Change Data Center (GCDC), the Space Data and Computing Division (SDCD), and four science Laboratories, including Laboratory for Terrestrial Physics, Laboratory for Atmospheres, and Laboratory for Hydrospheric Processes all in Greenbelt, MD. The fourth research organization, Goddard Institute for Space Studies (GISS), is in New York, NY. Relevant to NASA's Strategic Plan, the Laboratory ensures that all work undertaken and completed is within the vision of GSFC. The philosophy of the Laboratory is to balance the completion of near term goals, while building on the Laboratory's achievements as a foundation for the scientific challenges in the future.

2003-01-01

302

Guiding future research on terrestrial ecosystem disturbance  

NASA Astrophysics Data System (ADS)

With North American ecosystems responsible for drawing hundreds of teragrams of carbon from the atmosphere each year, the tenuous balance of the terrestrial carbon budget can be upset for decades by disturbances such as fires, storms, disease outbreaks, insect infestations, and logging. Research cataloging the effects of such disturbances on regional carbon cycling tends to be sporadic or of limited scope. Most research has focused on forests but is less extensive for other important ecosystems such as grasslands or permafrost peatlands.

Schultz, Colin

2013-04-01

303

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

304

Methane production in terrestrial arthropods.  

PubMed Central

We 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. We show that arthropod symbionts can contribute substantially to atmospheric methane. Images PMID:8202505

Hackstein, J H; Stumm, C K

1994-01-01

305

Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions for the condensation of a water ocean  

NASA Astrophysics Data System (ADS)

The thermal evolution of magma oceans produced by collision with giant impactors late in planetary accretion is expected to depend on the composition and structure of the atmosphere through the greenhouse effect of CO2 and H2O released from the magma during its crystallization. In order to constrain the various cooling timescales of the system, we developed a 1D parameterized convection model of the thermal evolution of a magma ocean coupled with a 1D radiative-convective model of a primitive atmosphere. We conducted a parametric study to investigate the influence of the initial volatile inventories, the initial depth of the magma ocean and the radiogenic heat production rate on the cooling sequence. Our results show that the presence of a convective-radiative steam atmosphere has a strong influence on the duration of the magma ocean phase, which varies from a few thousand years without atmosphere to typically 1 Myr when a steam atmosphere is present. Moreover, the time required for the formation of a water ocean on the planet surface is respectively 0.1 Myr, 1.5 Myr and 10 Myr for Mars, Earth and Venus. This time would be virtually infinite for an Earth-sized planet located closer than 0.66 AU from the Sun. For Mars and the Earth, these times are definitely shorter than the average time between major impacts, so that successive water oceans could have developed during accretion, facilitating the loss of their atmospheres by impact erosion. On the contrary, Venus could have remained in the magma ocean stage for most of its accretion.

Lebrun, Thomas; Massol, Helene; Chassefiere, Eric; Davaille, Anne; Marcq, Emmanuel; Sarda, Philippe; Leblanc, François; Brandeis, Geneviève

2013-04-01

306

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

307

Remote sensing of the terrestrial environment using middle infrared radiation (3.0-5.0 µm)  

Microsoft Academic Search

The middle infrared (MIR) spectral region, between 3.0 and 5.0?µm in the electromagnetic spectrum, features a myriad of atmospheric windows. The favourable atmospheric penetration of electromagnetic radiation at MIR wavelengths has been readily noted. To exploit this atmospheric window, there have been several remote sensing instruments acquiring radiation from the terrestrial environment. However, these data remain under-utilized for terrestrial environmental

Doreen S. Boyd; Francois Petitcolin

2004-01-01

308

Coreless Terrestrial Exoplanets  

E-print Network

Differentiation in terrestrial planets is expected to include the formation of a metallic iron core. We predict the existence of terrestrial planets that have differentiated but have no metallic core--planets that are effectively a giant silicate mantle. We discuss two paths to forming a coreless terrestrial planet, whereby the oxidation state during planetary accretion and solidification will determine the size or existence of any metallic core. Under this hypothesis, any metallic iron in the bulk accreting material is oxidized by water, binding the iron in the form of iron oxide into the silicate minerals of the planetary mantle. The existence of such silicate planets has consequences for interpreting the compositions and interior density structures of exoplanets based on their mass and radius measurements.

L. Elkins-Tanton; S. Seager

2008-08-13

309

Atmospheric Chemistry of Venus-like Exoplanets Laura Schaefer  

E-print Network

- 1 - Atmospheric Chemistry of Venus-like Exoplanets by Laura Schaefer and Bruce Fegley, Jr thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough observations of the atmospheres of terrestrial-sized exoplanets by current and proposed space observatories

Fegley Jr., Bruce

310

Terrestrial versus giant planet formation  

NASA Technical Reports Server (NTRS)

Given a solar nebular surrounding the early protosun, containing dust grains that have already undergone growth through collisions to about centimeter-size, the question of the formation of the terrestrial and giant planets is considered. In contrast to the usual approach of emphasizing how well a problem is understood, the uncertainties and areas where more work needs to be done will be accentuated. Also, the emphasis will be on the dynamics of planetary formation, because profound problems still exist in this area, and because it seems most logical to concentrate first on the dynamical questions involved with assembling the planets before putting too much effort into the detailed chemical and geological consequences of certain formation mechanisms.

Boss, Alan P.

1988-01-01

311

Atmospheric aerosols as prebiotic chemical reactors  

PubMed Central

Aerosol particles in the atmosphere have recently been found to contain a large number of chemical elements and a high content of organic material. The latter property is explicable by an inverted micelle model. The aerosol sizes with significant atmospheric lifetimes are the same as those of single-celled organisms, and they are predicted by the interplay of aerodynamic drag, surface tension, and gravity. We propose that large populations of such aerosols could have afforded an environment, by means of their ability to concentrate molecules in a wide variety of physical conditions, for key chemical transformations in the prebiotic world. We also suggest that aerosols could have been precursors to life, since it is generally agreed that the common ancestor of terrestrial life was a single-celled organism. The early steps in some of these initial transformations should be accessible to experimental investigation. PMID:11035775

Dobson, Christopher M.; Ellison, G. Barney; Tuck, Adrian F.; Vaida, Veronica

2000-01-01

312

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

313

Terrestrial Planet Finder: science overview  

NASA Technical Reports Server (NTRS)

The Terrestrial Planet Finder (TPF) seeks to revolutionize our understanding of humanity's place in the universe - by searching for Earth-like planets using reflected light, or thermal emission in the mid-infrared. Direct detection implies that TPF must separate planet light from glare of the nearby star, a technical challenge which has only in recent years been recognized as surmountable. TPF will obtain a low-resolution spectra of each planets it detects, providing some of its basic physical characteristics and its main atmospheric constituents, thereby allowing us to assess the likelihood that habitable conditions exist there. NASA has decided the scientific importance of this research is so high that TPF will be pursued as two complementary space observatories: a visible-light coronagraph and a mid-infrared formation flying interferometer. The combination of spectra from both wavebands is much more valuable than either taken separately, and it will allow a much fuller understanding of the wide diversity of planetary atmospheres that may be expected to exist. Measurements across a broad wavelength range will yield not only physical properties such as size and albedo, but will also serve as the foundations of a reliable and robust assessment of habitability and the presence of life.

Unwin, Stephen C.; Beichman, C. A.

2004-01-01

314

A Spherical Non-LTE Line-blanketed Stellar Atmosphere Model of the Early B Giant epsilon Canis Majoris  

Microsoft Academic Search

We use a spherical non-LTE fully line-blanketed model atmosphere to fit the full multiwavelength spectrum, including the extreme-ultraviolet (EUV) continuum observed by the Extreme Ultraviolet Explorer, of the B2 II star epsilon Canis Majoris (CMa). The available spectrophotometry of epsilon CMa from 350 Angstroms to 25 mu m is best fitted with model parameters Teff = 21,750 K, log g

J. P. Aufdenberg; P. H. Hauschildt; S. N. Shore; E. Baron

1998-01-01

315

Solar Terrestrial Observatory Space Station Workshop Report  

NASA Technical Reports Server (NTRS)

In response to a need to develop and document requirements of the Solar Terrestrial Observatory at an early time, a mini-workshop was organized and held on June 6, 1985. The participants at this workshop set as their goal the preliminary definition of the following areas: (1) instrument descriptions; (2) placement of instrumentation on the IOC Space Station; (3) servicing and repair assessment; and (4) operational scenarios. This report provides a synopsis of the results of that workshop.

Roberts, W. T. (editor)

1986-01-01

316

Batteries for terrestrial applications  

SciTech Connect

Extensive research has been conducted in the design and manufacture of very long life vented and sealed maintenance free nickel-cadmium aircraft batteries. These batteries have also been used in a number of terrestrial applications with good success. This study presents an overview of the Ni-Cd chemistry and technology as well as detailed analysis of the advantages and disadvantages of the Ni-Cd couple for terrestrial applications. The performance characteristics of both sealed and vented Ni-Cd's are presented. Various charge algorithms are examined and evaluated for effectiveness and ease of implementation. Hardware requirements for charging are also presented and evaluated. The discharge characteristics of vented and sealed Ni-Cd's are presented and compared to other battery chemistries. The performance of Ni-Cd's under extreme environmental conditions is also compared to other battery chemistries. The history of various terrestrial applications is reviewed and some of the lessons learned are presented. Applications discussed include the NASA Middeck Payload Battery, Raytheon Aegis Missile System Battery, THAAD Launcher battery, and the Titan IV battery. The suitability of the Ni-Cd chemistry for other terrestrial applications such as electric vehicles and Uninterruptible Power Supply is discussed.

Kulin, T.M.

1998-07-01

317

Terrestrial cosmic rays  

Microsoft Academic Search

This paper reviews the basic physics of those cosmic rays which can affect terrestrial electronics. Cosmic rays at sea level consist mostly of neutrons, protons, pions, muons, electrons, and photons. The particles which cause significant soft fails in electronics are those particles with the strong interaction: neutrons, protons, and pions. At sea level, about 95% of these particles are neutrons.

James F. Ziegler

1996-01-01

318

INTRODUCED TERRESTRIAL SPECIES (FUTURE)  

EPA Science Inventory

These data represent predicted future potential distributions of terrestrial plants, animals, and pathogens non-native to the Middle-Atlantic region. These data are available for 8-digit HUCs. The data are a weighted proportion of appropriate habitat overlapped by the potential...

319

Abstracts for the International Workshop on Meteorite Impact on the Early Earth  

NASA Technical Reports Server (NTRS)

This volume contains abstracts that were accepted for presentation at the International Workshop on Meteorite Impact on the Early Earth, September 21-22, 1990, in Perth, Western Australia. The effects these impacts had on the young Earth are emphasized and a few of the topics covered are as follows: impact induced hot atmosphere, crater size and distribution, late heavy bombardment, terrestrial mantle and crust, impact damage, continental growth, volcanism, climate catastrophes, shocked quartz, and others.

1990-01-01

320

Abstracts for the International Workshop on Meteorite Impact on the Early Earth  

NASA Astrophysics Data System (ADS)

This volume contains abstracts that were accepted for presentation at the International Workshop on Meteorite Impact on the Early Earth, September 21-22, 1990, in Perth, Western Australia. The effects these impacts had on the young Earth are emphasized and a few of the topics covered are as follows: impact induced hot atmosphere, crater size and distribution, late heavy bombardment, terrestrial mantle and crust, impact damage, continental growth, volcanism, climate catastrophes, shocked quartz, and others.

1990-09-01

321

Terrestrial water fluxes dominated by transpiration.  

PubMed

Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes. PMID:23552893

Jasechko, Scott; Sharp, Zachary D; Gibson, John J; Birks, S Jean; Yi, Yi; Fawcett, Peter J

2013-04-18

322

Interworking evolution of mobile satellite and terrestrial networks  

NASA Astrophysics Data System (ADS)

There is considerable interest among mobile satellite service providers in interworking with terrestrial networks to provide a universal global network. With such interworking, subscribers may be provided a common set of services such as those planned for the Public Switched Telephone Network (PSTN), the Integrated Services Digital Network (ISDN), and future Intelligent Networks (IN's). This paper first reviews issues in satellite interworking. Next the status and interworking plans of terrestrial mobile communications service providers are examined with early examples of mobile satellite interworking including a discussion of the anticipated evolution towards full interworking between mobile satellite and both fixed and mobile terrestrial networks.

Matyas, R.; Kelleher, P.; Moller, P.; Jones, T.

323

Interworking evolution of mobile satellite and terrestrial networks  

NASA Technical Reports Server (NTRS)

There is considerable interest among mobile satellite service providers in interworking with terrestrial networks to provide a universal global network. With such interworking, subscribers may be provided a common set of services such as those planned for the Public Switched Telephone Network (PSTN), the Integrated Services Digital Network (ISDN), and future Intelligent Networks (IN's). This paper first reviews issues in satellite interworking. Next the status and interworking plans of terrestrial mobile communications service providers are examined with early examples of mobile satellite interworking including a discussion of the anticipated evolution towards full interworking between mobile satellite and both fixed and mobile terrestrial networks.

Matyas, R.; Kelleher, P.; Moller, P.; Jones, T.

1993-01-01

324

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

325

Volcanic ash - Terrestrial versus extraterrestrial  

NASA Technical Reports Server (NTRS)

A principal difference between terrestrial and extraterrestrial lavas may consist in the greater ability of terrestrial lavas to form thin films (like those of soap bubbles) and hence foams. It would follow that, in place of the pumice and spiny shards found in terrestrial volcanic ash, an extraterrestrial ash should contain minute spherules. This hypothesis may help to explain lunar microspherules.

Okeefe, J. A.

1976-01-01

326

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

2012-02-01

327

Terrestrial cooling in Northern Europe during the eocene-oligocene transition.  

PubMed

Geochemical and modeling studies suggest that the transition from the "greenhouse" state of the Late Eocene to the "icehouse" conditions of the Oligocene 34-33.5 Ma was triggered by a reduction of atmospheric pCO2 that enabled the rapid buildup of a permanent ice sheet on the Antarctic continent. Marine records show that the drop in pCO2 during this interval was accompanied by a significant decline in high-latitude sea surface and deep ocean temperature and enhanced seasonality in middle and high latitudes. However, terrestrial records of this climate transition show heterogeneous responses to changing pCO2 and ocean temperatures, with some records showing a significant time lag in the temperature response to declining pCO2. We measured the ?47 of aragonite shells of the freshwater gastropod Viviparus lentus from the Solent Group, Hampshire Basin, United Kingdom, to reconstruct terrestrial temperature and hydrologic change in the North Atlantic region during the Eocene-Oligocene transition. Our data show a decrease in growing-season surface water temperatures (~10 °C) during the Eocene-Oligocene transition, corresponding to an average decrease in mean annual air temperature of ~4-6 °C from the Late Eocene to Early Oligocene. The magnitude of cooling is similar to observed decreases in North Atlantic sea surface temperature over this interval and occurs during major glacial expansion. This suggests a close linkage between atmospheric carbon dioxide concentrations, Northern Hemisphere temperature, and expansion of the Antarctic ice sheets. PMID:23610424

Hren, Michael T; Sheldon, Nathan D; Grimes, Stephen T; Collinson, Margaret E; Hooker, Jerry J; Bugler, Melanie; Lohmann, Kyger C

2013-05-01

328

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

329

The sensitivity of terrestrial carbon storage to climate change  

NASA Technical Reports Server (NTRS)

The role of the terrestrial biosphere in controlling atmospheric CO2 levels during climate perturbations is estimated. Simulations are used to calculate the local geographical distribution of vegetation during the last glacial maximum. The known changes in sea level at this time, together with the simulated climate-driven spatial arrangement of vegetation, result in a mass transfer of carbon from the terrestrial biosphere to the atmosphere ranging from 30 Gt (corresponding to 15 ppm CO2) to -50 Gt (25 ppm). Thus, although the biosphere may have contributed to the decrease in atmospheric CO2 at 80 ppm, known to have occurred at 18 kyr, it does not seem to have been a dominant factor. For simulations run with twice the present-day CO2 levels, strong negative feedbacks appear which remove 235 Gt of carbon from the atmosphere.

Prentice, Katharine C.; Fung, Inez Y.

1990-01-01

330

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

331

Interactions between the carbon cycle and the nitrogen cycle are critical to predicting terrestrial carbon sequestration  

Microsoft Academic Search

The extent to which terrestrial ecosystems mitigate rising concentrations of atmospheric CO2 depends on the coupled interactions between climate the carbon cycle and nutrient cycling. In nearly terrestrial ecosystems the availability of nitrogen poses a fundamental constraint on carbon sequestration, yet the incorporation of nitrogen cycle feedbacks into global-scale models is often simplistic and sometimes completely ignored. This is in

A. C. Finzi

2008-01-01

332

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

333

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

334

Assessment of Present-Day vs. Lateglacial/Early Holocene climate variability and atmospheric CO2 changes from tree-ring stable isotope time series  

NASA Astrophysics Data System (ADS)

The Younger Dryas interval during the Last Glacial Termination was an abrupt return to glacial-like conditions punctuating the transition to a warmer, interglacial climate. Despite recent advances in the layer counting of ice-core records of the termination, the timing and length of the Younger Dryas remain controversial. Late Glacial and early Holocene tree-ring chronologies are rare, however, they contain valuable information about past environmental conditions at annual time resolution. Changes in tree-ring growth rates can be related to past climate anomalies and changes in the carbon and oxygen isotope composition of tree-ring cellulose reflect atmospheric and hydrospheric changes. We are investigating a 600-year (13100 - 12500 cal BP) absolutely dated dendrochronological record of Late Glacial and Early Holocene chronologies of scots pine (Pinus sylvestris L.) from subfossil tree remnants from Barbiers River (Moyenne Durance, Southern French Alps), as well as from Swiss (Dättnau, Landikon and Gänziloh) and German (Cottbus) sites. Dendro-ecological parameters, such as ring width and stable isotope variations (? 13C und ? 18O) are used to infer past environmental conditions. We will present our first oxygen isotope records from tree rings reflecting the environmental changes of a ca. 300 year period between 12790 - 12478 cal BP.

Pieper, H.; Helle, G.; Brauer, A.; Kaiser, K. F.; Miramont, C.

2012-12-01

335

THE DEFINITION AND INTERPRETATION OF TERRESTRIAL ENVIRONMENT DESIGN INPUTS FOR VEHICLE DESIGN CONSIDERATIONS  

NASA Technical Reports Server (NTRS)

The description and interpretation of the terrestrial environment (0-90 km altitude) is an important driver of aerospace vehicle structural, control, and thermal system design. NASA is currently in the process of reviewing the meteorological information acquired over the past decade and producing an update to the 1993 Terrestrial Environment Guidelines for Aerospace Vehicle Design and Development handbook. This paper addresses the contents of this updated handbook, with special emphasis on new material being included in the areas of atmospheric thermodynamic models, wind dynamics, atmospheric composition, atmospheric electricity, cloud phenomena, atmospheric extremes, sea state, etc. In addition, the respective engineering design elements will be discussed relative to the importance and influence of terrestrial environment inputs that require consideration and interpretation for design applications. Specific lessons learned that have contributed to the advancements made in the acquisition, interpretation, application and awareness of terrestrial environment inputs for aerospace engineering applications are discussed.

Johnson, Dale L.; Keller, Vernon W.; Vaughan, William W.

2005-01-01

336

75 FR 57263 - New Policy Announcing That Traditional Horizontal Survey Projects Performed With Terrestrial...  

Federal Register 2010, 2011, 2012, 2013

...Survey Projects Performed With Terrestrial Survey Techniques Will No Longer Be Accepted for Processing or Loading Into NGS Databases AGENCY: National Geodetic Survey (NGS), National Ocean Service (NOS), National Oceanic and Atmospheric...

2010-09-20

337

Terrestrial Planet Finder Coronagraph overview of technology development & system design  

NASA Technical Reports Server (NTRS)

Astronomers have discovered over 150 planets orbiting other stars. NASA mission; Find and characterize terrestrial (or rocky) exo-planets that might harbor life (like Earth)liquid water on the planet (habitable zone). An atmosphere that indicates the presence of life water, oxygen, ozone, carbon dioxide, chlorophyll, and methane. Two missions under development: A coronagraph and an interferometer.

Balasubramanian, Kunjuthapatham; Ford, Virginia; Mouroulis, Pantazis; Hoppe, Daniel; Shaklan, Stuart

2004-01-01

338

Modelling a global biogeochemical nitrogen cycle in terrestrial ecosystems  

Microsoft Academic Search

An integrated global model developed mechanistically based on nitrogen transformation processes and nitrogen fluxes between the terrestrial biosphere and the atmosphere is described in this paper. This model was designed in conjunction with our previous global carbon model on the compartments of vegetation and organic-soil, a third compartment, inorganic-soil, comprising ammonium and nitrate was also incorporated. We divided the global

Bin-Le Lin; Akiyoshi Sakoda; Ryosuke Shibasaki; Naohiro Goto; Motoyuki Suzuki

2000-01-01

339

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

340

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.

341

Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events  

PubMed Central

The Devonian Period was characterized by major changes in both the terrestrial biosphere, e.g. the evolution of trees and seed plants and the appearance of multi-storied forests, and in the marine biosphere, e.g. an extended biotic crisis that decimated tropical marine benthos, especially the stromatoporoid-tabulate coral reef community. Teleconnections between these terrestrial and marine events are poorly understood, but a key may lie in the role of soils as a geochemical interface between the lithosphere and atmosphere/hydrosphere, and the role of land plants in mediating weathering processes at this interface. The effectiveness of terrestrial floras in weathering was significantly enhanced as a consequence of increases in the size and geographic extent of vascular land plants during the Devonian. In this regard, the most important palaeobotanical innovations were (1) arborescence (tree stature), which increased maximum depths of root penetration and rhizoturbation, and (2) the seed habit, which freed land plants from reproductive dependence on moist lowland habitats and allowed colonization of drier upland and primary successional areas. These developments resulted in a transient intensification of pedogenesis (soil formation) and to large increases in the thickness and areal extent of soils. Enhanced chemical weathering may have led to increased riverine nutrient fluxes that promoted development of eutrophic conditions in epicontinental seaways, resulting in algal blooms, widespread bottomwater anoxia, and high sedimentary organic carbon fluxes. Long-term effects included drawdown of atmospheric pCO2 and global cooling, leading to a brief Late Devonian glaciation, which set the stage for icehouse conditions during the Permo-Carboniferous. This model provides a framework for understanding links between early land plant evolution and coeval marine anoxic and biotic events, but further testing of Devonian terrestrial-marine teleconnections is needed.

Algeo, T. J.

1998-01-01

342

Atmospheric Aerosols  

NASA Technical Reports Server (NTRS)

Aerosols, defined as particles and droplets suspended in air, are always present in the atmosphere. They are part of the earth-atmosphere climate system, because they interact with both incoming solar and outgoing terrestrial radiation. They do this directly through scattering and absorption, and indirectly through effects on clouds. Submicrometer aerosols usually predominate in terms of number of particles per unit volume of air. They have dimensions close to the wavelengths of visible light, and thus scatter radiation from the sun very effectively. They are produced in the atmosphere by chemical reactions of sulfur-, nitrogen- and carbon-containing gases of both natural and anthropogenic origins. Light absorption is dominated by particles containing elemental carbon (soot), produced by incomplete combustion of fossil fuels and by biomass burning. Light-scattering dominates globally, although absorption can be significant at high latitudes, particularly over highly reflective snow- or ice-covered surfaces. Other aerosol substances that may be locally important are those from volcanic eruptions, wildfires and windblown dust.

Pueschel, R. F.; Lawless, James G. (Technical Monitor)

1994-01-01

343

Terrestrial nitrogen-carbon cycle interactions at the global scale  

PubMed Central

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.

2013-01-01

344

On the chaotic nature of solar-terrestrial environment: Interplanetary Alfvén intermittency  

Microsoft Academic Search

We present an overview of observational and theoretical evidence of chaos and intermittency in the solar-terrestrial environment including solar dynamo, solar atmosphere, solar wind, and terrestrial magnetosphere-ionosphere-atmosphere. The chaotic nature of space plasmas is studied by a nonlinear model of Alfvén waves described by the low-dimensional limit of the derivative nonlinear Schrödinger equation given by its stationary solutions in the

A. C.-L. Chian; Y. Kamide; E. L. Rempel; W. M. Santana

2006-01-01

345

Atmospheric Circulation of Exoplanets Adam P. Showman  

E-print Network

Atmospheric Circulation of Exoplanets Adam P. Showman University of Arizona James Y-K. Cho Queen of atmospheric dynamics relevant to explaining existing and future observations of exoplanets, both gas giant and terrestrial. Given the paucity of data on exoplanet atmospheres, our approach is to emphasize fundamental

346

Mercury bioaccumulation and trophic transfer in the terrestrial food web of a montane forest.  

PubMed

We investigated mercury (Hg) concentrations in a terrestrial food web in high elevation forests in Vermont. Hg concentrations increased from autotrophic organisms to herbivores < detritivores < omnivores < carnivores. Within the carnivores studied, raptors had higher blood Hg concentrations than their songbird prey. The Hg concentration in the blood of the focal study species, Bicknell's thrush (Catharus bicknelli), varied over the course of the summer in response to a diet shift related to changing availability of arthropod prey. The Bicknell's thrush food web is more detrital-based (with higher Hg concentrations) in early summer and more foliage-based (with lower Hg concentrations) during late summer. There were significant year effects in different ecosystem compartments indicating a possible connection between atmospheric Hg deposition, detrital-layer Hg concentrations, arthropod Hg concentrations, and passerine blood Hg concentrations. PMID:19960247

Rimmer, Christopher C; Miller, Eric K; McFarland, Kent P; Taylor, Robert J; Faccio, Steven D

2010-04-01

347

A Characterization of the Terrestrial Environment of Kodiak Island, Alaska for the Design, Development and Operation of Launch Vehicles  

NASA Technical Reports Server (NTRS)

A quantitative characterization of the terrestrial environment is an important component in the success of a launch vehicle program. Environmental factors such as winds, atmospheric thermodynamics, precipitation, fog, and cloud characteristics are among many parameters that must be accurately defined for flight success. The National Aeronautics and Space Administration (NASA) is currently coordinating weather support and performing analysis for the launch of a NASA payload from a new facility located at Kodiak Island, Alaska in late 2001 (NASA, 1999). Following the first launch from the Kodiak Launch Complex, an Air Force intercontinental ballistic missile on November 5, 1999, the site's developer, the Alaska Aerospace Development Corporation (AADC), is hoping to acquire a sizable share of the many launches that will occur over the next decade. One such customer is NASA, which is planning to launch the Vegetation Canopy Lidar satellite aboard an Athena I rocket, the first planned mission to low earth orbit from the new facility. To support this launch, a statistical model of the atmospheric and surface environment for Kodiak Island, AK has been produced from rawinsonde and surface-based meteorological observations for use as an input to future launch vehicle design and/or operations. In this study, the creation of a "reference atmosphere" from rawinsonde observations is described along with comparisons between the reference atmosphere and existing model representations for Kodiak. Meteorological conditions that might result in a delay on launch day (cloud cover, visibility, precipitation, etc.) are also explored and described through probabilities of launch by month and hour of day. This atmospheric "mission analysis" is also useful during the early stages of a vehicle program, when consideration of the climatic characteristics of a location can be factored into vehicle designs. To be most beneficial, terrestrial environment definitions should a) be available at the inception of the program and based on the desired operational performance of the launch vehicle, b) be issued under the signature of the program manager and be part of the controlled program definition and requirements documentation, and c) specify the terrestrial environment for all phases of activity including prelaunch, launch, ascent, on-orbit, decent, and landing. Since the beginning of the space era, NASA has utilized some of the most detailed assessments of the terrestrial climatic environment in design, development, and operations of both expendable and reusable launch vehicles.

Rawlins, Michael A.; Johnson, Dale L.; Batts, Glen W.

2000-01-01

348

Tropical African vegetation change during the early Pliocene  

NASA Astrophysics Data System (ADS)

The early Pliocene is the most recent period to experience sustained global warmth with similar to modern atmospheric CO2 concentrations (~400ppmV), but the response of terrestrial ecosystems in the tropics to these conditions is poorly understood. Here we explore vegetation change in northeast Africa during the early Pliocene using terrestrial biomarkers in marine sediments from the Gulf of Aden. Plant leaf wax C30 n-alkanoic acid carbon isotopic composition (?13Cwax) spanning 5.3 to 3.8 Ma indicate a trend towards dominance of plants using the C3 (Calvin cycle), reversing the earlier expansion of C4 (Hatch-Slack) biomass in the Miocene. The return to C3 dominance by the mid Pliocene reflects a combination of the possible drivers including more humid conditions controlled by rising western Indian Ocean SSTs and globally elevated atmospheric CO2 levels as well as the direct effects of higher atmospheric CO2 on quantum yields favoring the competitiveness of C3 plants. Intriguingly, high variability is also observed during this period with shifts in ?13Cwax of up to 7‰ on 105 year timescales, presumably linked to local orbital forcing. Taken together, these trends indicate dynamic changes in vegetation that oscillate between more forested and more open grasslands with increasingly more woody cover by the mid Pliocene.

Liddy, H.; Sieracki, A.; Feakins, S. J.

2013-12-01

349

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

350

Ozone generation by rock fracture: Earthquake early warning?  

NASA Astrophysics Data System (ADS)

We report the production of up to 10 ppm ozone during crushing and grinding of typical terrestrial crust rocks in air, O2 and CO2 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, Raúl A.; Dukes, Catherine A.; Hedges, Dawn

2011-11-01

351

Temporal variations in atmospheric CO2 on Rishiri Island in 2006-2013: responses of the interannual variation in amplitude to climate and the terrestrial sink in East Asia  

NASA Astrophysics Data System (ADS)

Surface observation of the atmospheric CO2 mixing ratio implies the combined influences of both natural fluctuations and anthropogenic activities on the carbon cycle. Atmospheric CO2 has been measured on Rishiri Island in the outflow region of Eurasia since May 2006. We report the first 7 year temporal atmospheric CO2 variations from diurnal to interannual scales. In the diurnal scale, an obvious cycle appeared as a minimum in the afternoon and maximum at midnight in the summer months. Seasonally, the maximum CO2 concentration appeared around the beginning of April, while the minimum appeared around the middle of August. A mean growing season length of ~126 days was estimated. In the period from 2007 to 2012, the peak-to-peak amplitude increased until 2009 and decreased thereafter, with a mean value of 19.7 ppm. In the long term, atmospheric CO2 is increasing by a mean growth rate of 2.1 ppm year-1. Investigations on the driving climatic factors on the interannual variation in amplitude indicated that temperature in East Asia (40-60° N, 90-150° E) affected the CO2 amplitude by affecting the seasonal maximum, with a time lag of 1-2 years. On the contrary, precipitation did not likely affect CO2 amplitudes. The amplitude also responded to a natural carbon source/sink variation in East Asia. We suggest that temperature in the first year would affect carbon sinks in the second year in the fetch regions, which further affect CO2 amplitude mainly through ecosystem respiration. Circulation changes also likely contributed to the decreasing amplitude since 2009, as indicated by the simultaneous decrease in the 222Rn concentration in spring and summer.

Zhu, C.; Yoshikawa-Inoue, H.

2014-06-01

352

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

353

Cumulus convection and the terrestrial water-vapor distribution  

NASA Technical Reports Server (NTRS)

Cumulus convection plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus convection acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus convection influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus convection works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.

Donner, Leo J.

1988-01-01

354

Chapter 8 Terrestrial Biological Resources  

E-print Network

This chapter describes the environmental setting for terrestrial biological resources and the regulatory setting associated with these resources. It also evaluates environmental impacts on terrestrial biological resources that could result from the Lower San Joaquin River (LSJR) and southern Delta water quality (SDWQ) alternatives and, if applicable, offers mitigation measures that

unknown authors

355

A review of noble gas geochemistry in relation to early Earth history  

NASA Technical Reports Server (NTRS)

One of the most fundamental noble gas constraints on early Earth history is derived from isotopic differences in (129)Xe/(130)Xe between various terrestrial materials. The short half life (17 m.y.) of extinct (129I, parent of (129)Xe, means that these differences must have been produced within the first 100 m.y. after terrestrial accretion. The identification of large anomalies in (129)Xe/(130)Xe in mid ocean ridge basalts (MORB), with respect to atmospheric xenon, suggests that the atmosphere and upper mantle have remained separate since that time. This alone is a very strong argument for early catastrophic degassing, which would be consistent with an early fractionation resulting in core formation. However, noble gas isotopic systematics of oceanic basalts show that the mantle cannot necessarily be regarded as a homogeneous system, since there are significant variations in (3)He/(4)He, (40)Ar/(36)Ar, and (129)Xe/(130)Xe. Therefore, the early degassing cannot be considered to have acted on the whole mantle. The specific mechanisms of degassing, in particular the thickness and growth of the early crust, is an important variable in understanding present day noble gas inventories. Another constraint can be obtained from rocks that are thought to be derived from near the lithosphere asthenosphere boundary: ultramafic xenoliths.

Kurz, M. D.

1985-01-01

356

Plant Nitrogen Uptake in Terrestrial Biogeochemical Models  

NASA Astrophysics Data System (ADS)

Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be two to three times smaller than previously predicted. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares alternative models of plant N uptake as found in different terrestrial biogeochemical models against field measurements, and introduces a new N-uptake model to the Joint UK Land Environment Simulator (JULES).. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"

Marti, Alejandro; Cox, Peter; Sitch, Stephen; Jones, Chris; Liddicoat, spencer

2013-04-01

357

Plant Nitrogen Uptake in Terrestrial Biogeochemical Models  

NASA Astrophysics Data System (ADS)

Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be significantly smaller than previously predicted. However, models exhibit wide differences in their predictive accuracy and lead to widely diverging and inconsistent projections accounting for an uncertain Carbon sequestration decrease due to Nitrogen limitation ranging from 7 to 64%. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and higher atmospheric CO2 concentrations than originally expected. This study compares the differences in the predictions of alternative models of plant N uptake found in different terrestrial biogeochemical models with the predictions from a new N-uptake model developed under the Joint UK Land Environment Simulator (JULES) framework. We implement a methodology for the construction, parameterization and evaluation of N uptake models to fully decompose all the N uptake component processes in terms of their parameter uncertainty and the accuracy of their predictions with respect to different empirical data sets. Acknowledgements This work has been funded by the European Commission FP7-PEOPLE-ITN-2008 Marie Curie Action: "Greencycles II: FP7-PEOPLE-ITN-2008 Marie Curie Action: "Networks for Initial Training"

Marti Donati, A.; Cox, P.; Smith, M. J.; Purves, D.; Sitch, S.; Jones, C. D.

2013-12-01

358

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

359

The dynamics of Titan's atmosphere  

NASA Astrophysics Data System (ADS)

Titan is a slow rotator, and its atmospheric zonal winds are cyclostrophic. The most convincing evidence of this comes from temperatures retrieved from Voyager spacecraft infrared observations, and pressure fields inferred from stellar occultations observed from Earth. Titan has a moderate obliquity, comparable to Earth's, and the radiative relaxation times in its stratosphere are sufficiently short that large seasonal modulations of the temperatures and winds are expected. This is in contrast to Venus, the only other body in the solar system that has global cyclostrophic winds. There, seasonal effects are secondary, because its rotation axis is nearly normal to its orbit. Zonal-mean meridional winds on Titan have been inferred from the retrieved atmospheric temperatures and the observed distribution of stratospheric hazes. The winds are sluggish, on the order of centimeters per second in the stratosphere, in part because of the long radiative time constants. The stratospheric temperatures suggest that the meridional circulation may be thermally indirect. On Earth, this often results from circulations being driven and/or modulated by vertically propagating waves. However, atmospheric waves on Titan are as yet poorly characterized. Titan may have an analog to the terrestrial Antarctic ozone hole: Voyager spacecraft observations of Titan indicated cold temperatures, strong circumpolar winds, anomalous concentrations of some gases (hydrocarbons and nitriles), and ices in the north polar region during early northern spring. Thus, the interplay of photochemical processes, surface microphysics, and dynamical transport may be as complex as they are on Earth. Titan may also be similar to Earth in having a ``hydrological'' cycle, but involving methane instead of water. Recent ground-based near-infrared observations have indicated activity in the southern summer near Titan's south pole that is suggestive of convective clouds. The observations expected shortly from the battery of instruments on the Cassini orbiter and Huygens probe will be summarized. These will provide the first detailed, global characterization of Titan's dynamic meteorology.

Flasar, F. M.

360

Formation of early water oceans on rocky planets  

NASA Astrophysics Data System (ADS)

Terrestrial planets, with silicate mantles and metallic cores, are likely to obtain water and carbon compounds during accretion. Here I examine the conditions that allow early formation of a surface water ocean (simultaneous with cooling to clement surface conditions), and the timeline of degassing the planetary interior into the atmosphere. The greatest fraction of a planet's initial volatile budget is degassed into the atmosphere during the end of magma ocean solidification, leaving only a small fraction of the original volatiles to be released into the atmosphere through later volcanism. Rocky planets that accrete with water in their bulk mantle have two mechanisms for producing an early water ocean: First, if they accrete with at least 1 to 3 mass% of water in their bulk composition, liquid water may be extruded onto the planetary surface at the end of magma ocean solidification. Second, at initial water contents as low as 0.01 mass% or lower, during solidification a massive supercritical fluid and steam atmosphere is produced that collapses into a water ocean upon cooling. The low water contents required for this process indicate that rocky super-Earth exoplanets may be expected to commonly produce water oceans within tens to hundreds of millions of years of their last major accretionary impact, through collapse of their atmosphere.

Elkins-Tanton, Linda T.

2011-04-01

361

Benchmarking terrestrial biospheric models against CO2 observations from GOSAT  

NASA Astrophysics Data System (ADS)

There is a large degree of uncertainty in terrestrial biospheric model (TBM) representation of both the magnitude and spatial distribution of carbon sources and sinks on the land surface. The lack of direct observations of land-atmosphere carbon exchange at the resolution of model estimates makes it difficult to assess the strengths and weaknesses of various modeling approaches in terms of their ability to represent the terrestrial carbon cycle. Atmospheric CO2 observations, however, provide an integrated view of surface sources and sinks of carbon, thus providing a potential powerful observational constraint for TBMs. Using the model results from the North American Carbon Program (NACP) Multi-scale synthesis and Terrestrial Model Intercomparison Project (MsTMIP) and the framework of NASA's Carbon Monitoring System (CMS) we assess the consistency of TBMs with satellite-based observations of atmospheric CO2. The MsTMIP TBM surface flux estimates, together with fossil fuel, air-sea fluxes, and biomass burning inventories, are coupled with the GEOS-Chem atmospheric transport model within CMS to generate the corresponding atmospheric CO2 signals. These signals are then pressure-averaged and directly compared with dry air column-averaged mole fractions of CO2 (?CO2) from the Greenhouse Gases Observing Satellite (GOSAT). Using model selection and multi-linear regression, we assess which model, or ensemble of models, best explain the ?CO2 observations. By weighting each model based on its consistency with GOSAT ?CO2 we identify the optimal weight for each individual model in a weighted multi-model ensemble. The inferred weights derived from the regression can help inform understanding of the relationship between surface flux representations and atmospheric CO2 measurements and can be linked back to process representation within the models themselves. Thus, comparing TBM estimates to atmospheric CO2 observations not only serves as an additional benchmark of model performance, but the results from these comparisons can also be used to aid in model development and improvement.

Swetish, J. B.; Huntzinger, D. N.; Michalak, A. M.; Schwalm, C. R.; Fisher, J. B.; Liu, J.; Bowman, K. W.

2013-12-01

362

Major Disturbance Events in Terrestrial Ecosystems Detected using Global Satellite Data Sets  

E-print Network

contribute to the current rise of carbon dioxide (CO2) levels in the atmosphere (Potter, 1999; Schimel et al., 2001). Because major `pulses' of CO2 from terrestrial biomass loss can be emitted to the atmosphere biogenic sources of CO2 have global implications for climatic change, which can in turn affect a vast

Kumar, Vipin

363

Spatiotemporal patterns of terrestrial carbon cycle during the 20th century  

Microsoft Academic Search

We evaluated how climate change, rising atmospheric CO2 concentration, and land use change influenced the terrestrial carbon (C) cycle for the last century using a process-based ecosystem model. Over the last century, the modeled land use change emitted about 129 Pg of C to the atmosphere. About 76% (or 98 Pg C) of this emission, however, was offset by net

Shilong Piao; Philippe Ciais; Pierre Friedlingstein; Nathalie de Noblet-Ducoudré; Patricia Cadule; Nicolas Viovy; Tao Wang

2009-01-01

364

Polar Record 44 (228): 1523 (2008). Printed in the United Kingdom. doi:10.1017/S0032247407006778 15 The status of two exotic terrestrial Crustacea on  

E-print Network

discovered on Macquarie Island in the early 1990s. The first, a terrestrial isopod, Styloniscus otakensis 15 The status of two exotic terrestrial Crustacea on sub-Antarctic Macquarie Island Penelope terrestrial Crustacea, Puhuruhuru patersoni (Amphipoda: Talitridae) and Styloniscus otakensis (Isopoda

Melbourne, Brett

365

Early Eocene's climate and ocean circulation from coupled model simulations  

NASA Astrophysics Data System (ADS)

While proxy data provide a snapshot of climate conditions at a specific location, coupled atmosphere-ocean models are able to expand this knowledge over the globe. Therefore, they are indispensable tools for understanding past climate conditions. We model the dynamical state of atmosphere and ocean during the Early Eocene and pre-industrial times, using the coupled atmosphere-ocean model ECHAM5/MPIOM with realistic reconstructions of vegetation and CO2. The resulting simulated climate variables are compared to terrestrial and oceanic proxies. The Early Eocene climate is in the global mean warmer (~13°C) and wetter (~1 mm/d) than in pre-industrial times. Especially temperatures in the Southern Ocean, the Greenland Sea and Arctic Ocean raise by up to 25K, being in accordance with surface temperature estimates from terrestrial and marine proxy data. The oceans are hereby rendered ice-free, leading to a decrease of polar albedo and thereby facilitating polar warming. This leads to a by 5K diminished equator-to-pole temperature gradient. Warmer temperatures as well as changed bathymetry have an effect on ocean dynamics in the Early Eocene. Although deep-water formation can be found in the Greenland Sea, Weddell Sea, and Tethys Sea, it is weaker than in the pre-industrial run and the resulting circulation is shallower. This is not only visible in water transport through sea gates but also in the Atlantic Meridional Overturning Circulation (AMOC), adopting its maximum at 700m depths in the Early Eocene, while maximum transport is reached in the pre-industrial control run at 1200m. Albeit a shallow and weak thermohaline circulation, a global ocean conveyor belt is being triggered, causing a transport from the areas of subduction through the Atlantic and Southern Oceans into the Indian and Pacific Oceans.

Weber, Tobias; Thomas, Maik

2014-05-01

366

Combined terrestrial and marine biomarker records from an Icelandic fjord: insights into Holocene climate drivers and marine/ terrestrial responses  

NASA Astrophysics Data System (ADS)

Holocene climate change has affected human cultures throughout at least the last 4000 years (D'Andrea et al., 2011). Today, studying Holocene climate variability is important, both to constrain the influence of climate change on ancient cultures and to place contemporary climate change in a historic context. Organic geochemical biomarkers are an ideal tool to study how climatic changes have affected terrestrial and marine ecosystems, as a host of different biomarker based climate proxies have emerged over recent years. Applying the available biomarker proxies on sediment cores from fjordic environments facilitates the study of how climate has affected terrestrial and marine ecosystems, and how these ecosystems have interacted. Ìsafjardardjúp fjord in Northwest Iceland is an ideal location to study North Atlantic Holocene climate change because the area is very sensitive to changes in the oceanic and atmospheric current systems (Hurrell, 1995; Quillmann et al., 2010). In this study we present high resolution (1 sample/30 calibrated years) terrestrial and marine biomarker records from a 38 m sediment core from Ìsafjardardjúp fjord covering the Holocene. We reconstruct sea surface temperature variations using the alkenone derived UK'37 proxy. Air temperature changes are reconstructed using the GDGT derived MBT/CBT palaeothermometer. We use the average chain length (ACL) variability of n-alkanes derived from terrestrial higher plant leaf waxes to reconstruct changing precipitation regimes. The relationship between ACL and precipitation is confirmed by comparing it with the ?D signature of the C29 n-alkane and soil pH changes inferred by the CBT proxy. The combined sea surface and air temperature and precipitation records indicate that different climate changing drivers were dominant at different stages of the Holocene. Sea surface temperatures were strongly influenced by the melting of the remaining glaciers from the last glacial maximum throughout the early Holocene, while air temperatures were influenced by high solar insolation. The central Holocene climate is mainly driven by decreasing northern hemisphere insolation, while the lateral transport of energy from the equator into the North Atlantic region drives climate change in the late Holocene. D'Andrea, W.J., Huang, Y., Fritz, S.C., Anderson, N.J., (2011) Abrupt Holocene climate change as an important factor for human migration in West Greenland. Proceedings of the National Academy of Sciences of the United States of America, 108(24), 9765-9769. Hurrell, J.W., (1995) Decadal trends in the North Atlantic Oscillation - Regional temperatures and precipitation. Science, 269(5224), 676-679. Quillmann, U., Jennings, A., Andrews, J., (2010) Reconstructing Holocene palaeoclimate and palaeoceanography in Isafjaroardjup, northwest Iceland, from two fjord records overprinted by relative sea-level and local hydrographic changes. Journal of Quaternary Science, 25(7), 1144-1159.

Moossen, H. M.; Seki, O.; Quillmann, U.; Andrews, J. T.; Bendle, J. A.

2012-12-01

367

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....

368

Radiocarbon dating of terrestrial carbonates  

USGS Publications Warehouse

Terrestrial carbonates encompass a wide range of materials that potentially could be used for radiocarbon (14C) dating. Biogenic carbonates, including shells and tests of terrestrial and aquatic gastropods, bivalves, ostracodes, and foraminifera, are preserved in a variety of late Quaternary deposits and may be suitable for 14C dating. Primary calcareous deposits (marls, tufa, speleothems) and secondary carbonates (rhizoliths, fracture fill, soil carbonate) may also be targeted for dating when conditions are favorable. This chapter discusses issues that are commonly encountered in 14C dating of terrestrial carbonates, including isotopic disequilibrium and open-system behavior, as well as methods used to determine the reliability of ages derived from these materials. Recent methodological advancements that may improve the accuracy and precision of 14C ages of terrestrial carbonates are also highlighted.

Pigati, Jeffrey S.

2014-01-01

369

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

370

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

371

Global response of the terrestrial biosphere to CO2 and climate change using a coupled climate-carbon cycle model  

E-print Network

feedback in the climate-carbon cycle system. INDEX TERMS: 0315 Atmospheric Composition and Structure: Impact phenomena; KEYWORDS: climate change impact, terrestrial carbon cycle Citation: Berthelot, M., P of the terrestrial biosphere to CO2 and climate change using a coupled climate-carbon cycle model, Global Biogeochem

Dufresne, Jean-Louis

372

Enhanced terrestrial carbon uptake in the Northern High Latitudes in the 21st century from the Coupled Carbon  

E-print Network

(NHL; poleward of 601N) may lead to dramatic changes in the terrestrial carbon cycle. On the one hand into the atmosphere. Here, the NHL terrestrial carbon storage is investigated based on 10 models from the Coupled Carbon Cycle Climate Model Intercomparison Project. Our analysis suggests that the NHL will be a carbon

Zeng, Ning

373

Space Science I: Planetary Atmospheres  

E-print Network

and evolution of atmospheres #12;Outline Overview of Solar System* Basic Properties of Atmospheres Composition Uranus* 14.5 2.3 56 Neptune* 17.0 2.8 57 Terrestrial-like Venus 0.81 0.56 90 750 Earth 1 0.65 1 280 Mars.0002 N 0.0004 Giant Planets (because of size U,N differ from J,S) Jupiter Saturn Uranus Neptune H2 0

Johnson, Robert E.

374

Feedback of atmospheric chemistry, via CH4, on the Eocene climate  

NASA Astrophysics Data System (ADS)

Atmospheric CH4 is a potent greenhouse gas, but it lacks a geochemical or paleobiological proxy for the pre-Quaternary. So the concentrations of CH4 prescribed in Mesozoic and early Tertiary paleoclimate modelling studies have tended to depend on simple approximations and assumptions. To move towards more realistic attempts at setting the global CH4 levels in paleoclimate models, we developed a new process-orientated approach to defining them. Our approach is based on modelling terrestrial ecosystem distributions and productivity, and the emissions of trace gases, particularly the volatile organic carbon (VOCs) compounds isoprene and monoterpene, for a given paleoclimate. The effects of the trace gas emissions on the chemistry of the atmosphere are assessed using a three-dimensional atmospheric chemical transport model coupled to the UK Meterological office (UKMO) ocean-atmosphere general circulation model of global climate. Results for simulations in the early Eocene indicate atmospheric CH4 concentrations in excess of 3000ppb, with VOC and climate reaction feedbacks being especially important. The feedback of this level of CH4 on climate in the early Eocene was assessed in separate sensitivity experiments with the UKMO GCM. The results indicate strong seasonal warming (up to 5oC), particularly of continental interiors in the Northern hemisphere during the winter months.

Beerling, D.; Valdes, P.

2002-12-01

375

Pre-terrestrial origin of rust in the Nakhla meteorite  

NASA Technical Reports Server (NTRS)

The authors present quantative elemental compositions and summarize textural evidence for the pre-terrestrial origin of rust on the Nakhla meteorite. The material in question is called 'rust' because its phase composition remains unknown. Compelling evidence for the pre-terrestrial origin of the rust is found in rust veins truncated by fusion crust and preserved as faults in sutured igneous crystals. Rust veins that approach the meteorite's fusion crust become discontinuous and exhibit vugs that suggest partial decrepitation; no veins that penetrate the fusion crust have been found. Because the rust probably contains volatile compounds, it is reasonable to expect that heating near the ablation surface (formed during atmospheric entry to Earth) would encourage devolatilization of the rust. Hence, the absence of rust veins in fusion crust and vugs in rust veins near fusion crust clearly imply that the rust existed in the meteorite before atmospheric entry.

Wentworth, Susan J.; Gooding, James L.

1990-01-01

376

Conditions for Organic Haze Formation in Planetary Atmospheres - A Case Study in Archean Earth  

NASA Astrophysics Data System (ADS)

Atmospheric haze can serve as a vital component in the prebiotic synthesis of organic compounds. In many planetary atmospheres, haze is a product of complex organic chemistry, initiated by the deposition of ultraviolet photons, forming compounds that can serve as key components in the propagation of prebiotic chemistry. Saturn’s moon, Titan, provides the prime example of the significance of haze in a planetary atmosphere in our present-day Solar System due to its intricate chemical interaction between aromatic hydrocarbons, nitrogen-bearing species, and complex ions. Titan has long been considered as an analogue for the environment possibly experienced by Archean Earth, and recent studies demonstrate that, like Titan, early Earth may have had an organically-furnished haze layer, facilitated by an enhanced ultraviolet solar flux during this period, protecting greenhouse gases and biota early in their development from harmful ultraviolet radiationi1 and allowing the Earth to maintain temperatures necessary for their development during the faint young Sun period. This primordial haze may have had a different composition than present-day Titan due to the CO2 content and possibly large amounts of H2 in prebiotic Earthi2. Furthermore, the amount of CO2 and H2 in the early terrestrial atmosphere would have had large implications in the efficiency of organic haze formation. A photochemical model employing complex neutral and ion chemistry is used to examine the mechanisms and efficiency of haze formation in a variety of conditions, focusing on sensitivity to factors such as atmospheric composition, and atmospheric temperature profile, and vertical mixing. These results can be used to assess the impact of atmospheric haze on the evolution of planetary atmospheres in our Solar System as well as viability of organic haze formation in the atmospheres of exoplanets. 1 Trainer et al., GRL, 31, L17S08, 2004. 2 Tian et al., Science 308, 1014-1017, 2005.

Wilson, Eric; Atreya, S.

2012-10-01

377

An Imaging Interferometer for Terrestrial Remote Sensing  

NASA Technical Reports Server (NTRS)

A prototype imaging interferometer called DASI (digital array scanned interferometer) is under development at our laboratories. Our objective is to design an instrument for remote sensing of Earth's atmosphere and surface. This paper describes the unusual characteristics of DASIs which make them promising candidates for ground and aircraft-based terrestrial measurements. These characteristics include superior signal-to-noise, design simplicity and compactness, relative to dispersion based imaging spectrometers. Perhaps one of the most notable features of DASIs is their ability to acquire an entire interferogram simultaneously without any moving optical elements. We also describe selected laboratory and ground based field measurements using the prototype DASI. A CCD detector array was placed at the DASI detector plane for wavelength coverage from 0.4 to 1.0 micron. A NICMOS MCT detector was used for coverage from 1.1 to 2.2 micron. The DASI was configured to have a spectral resolution of about 300 1/cm, a spatial field of view of 5 degrees, and a constant number of transverse spatial elements (detector dependent) for each exposure frame. Frame exposure rates were up to 0.6 Hz with the potential to achieve 5 Hz. Image cube measurements of laboratory targets and terrestrial scenes were obtained by multiple frame scanning over the field of view. These data sets reveal the potential science yields from obtaining simultaneous high resolution spatial and spectral information.

Hammer, Philip D.; Valero, Francisco P. J.; Peterson, David L.; Smith, William Hayden

1993-01-01

378

Consequences of Considering Carbon/Nitrogen Interactions on the Feedbacks between Climate and the Terrestrial Carbon Cycle  

E-print Network

A number of observational studies indicate that carbon sequestration by terrestrial ecosystems in a world with an atmosphere richer in carbon dioxide and a warmer climate depends on the interactions between the carbon and ...

Sokolov, Andrei P.

379

Impact of flares on the solar terrestrial environment  

SciTech Connect

The current knowledge of the flare process and its particle and photon emissions is summarized. The impact of flares on the different regions of the solar-terrestrial environment, in order of their distance from the Sun to Earth: the heliosphere, the magnetosphere, the ionosphere, and atmosphere are considered. The effect of flares on modern technology and manned spaceflight is described. In all cases, an attempt is made to distinguish clearly what is known, what is suspected, and is unknown.

Not Available

1984-06-01

380

Terrestrial Planet Finder: Technology Development Plans  

NASA Technical Reports Server (NTRS)

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 in 2014, and a separated-spacecraft infrared interferometer in 2016. Substantial funding has been committed to the development of the key technologies that are required to meet these goals for launch in the next decade. Efforts underway through industry and university contracts and at JPL include a number of system and subsystem testbeds, as well as components and numerical modeling capabilities. The science, technology, and design efforts are closely coupled to ensure that requirements and capabilities will be consistent and meet the science goals.

Lindensmith, Chris

2004-01-01

381

Guntersville Workshop on Solar-Terrestrial Studies  

NASA Technical Reports Server (NTRS)

The separation of purely solar physics from magnetospheric physics, and the effects of solar activity on geomagnetic activity are investigations which can be accomplished using the shuttle orbiter in an extended sortie mode, or an unmanned solar terrestrial observatory powered by the power module in an extended duration mode. When the power module is used with the shuttle in a sortie support mode, both the instrument capacity and the time in orbit of the orbiter can be increased several fold. In the free-flyer mode, the power module would be capable of providing power, basic attitude control, basic thermal control and housekeeping communications for unmanned, large, independent mission payloads in low earth orbit for periods of 6 months or longer. Instrument requirements for interdisciplinary joint observational programs are discussed for studies of the magnetosphere, the atmosphere, sun-weather relationships. Description summary charts of the power module are included.

1977-01-01

382

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates  

NASA Astrophysics Data System (ADS)

Xenon-isotopic ratios, step-heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from the Martian and terrestrial atmospheres among minerals in any one sample are similar, suggesting similarities in the processes by which they were acquired. However, in opaque and maskelynite fractions, Martian atmospheric xenon is released at higher temperatures than terrestrial atmospheric xenon. It is suggested that both Martian and terrestrial atmospheric xenon were initially introduced by weathering (low temperature alteration processes). However, the Martian component was redistributed by shock, accounting for its current residence in more retentive sites. The presence or absence of detectable 129Xe from the Martian atmosphere in mafic minerals may correspond to the extent of crustal contamination of the rock's parent melt. Variable contents of excess 129Xe contrast with previously reported consistent concentrations of excess 40Ar, suggesting distinct sources contributed these gases to the parent magma.

Cartwright, J. A.; Ocker, K. D.; Crowther, S. A.; Burgess, R.; Gilmour, J. D.

2010-08-01

383

Proterozoic oxygen rise linked to shifting balance between seafloor and terrestrial weathering  

PubMed Central

A shift toward higher atmospheric oxygen concentration during the late Proterozoic has been inferred from multiple indirect proxies and is seen by many as a prerequisite for the emergence of complex animal life. However, the mechanisms controlling the level of oxygen throughout the Proterozoic and its eventual rise remain uncertain. Here we use a simple biogeochemical model to show that the balance between long-term carbon removal fluxes via terrestrial silicate weathering and ocean crust alteration plays a key role in determining atmospheric oxygen concentration. This balance may be shifted by changes in terrestrial weatherability or in the generation rate of oceanic crust. As a result, the terrestrial chemical weathering flux may be permanently altered—contrasting with the conventional view that the global silicate weathering flux must adjust to equal the volcanic CO2 degassing flux. Changes in chemical weathering flux in turn alter the long-term supply of phosphorus to the ocean, and therefore the flux of organic carbon burial, which is the long-term source of atmospheric oxygen. Hence we propose that increasing solar luminosity and a decrease in seafloor spreading rate over 1,500–500 Ma drove a gradual shift from seafloor weathering to terrestrial weathering, and a corresponding steady rise in atmospheric oxygen. Furthermore, increased terrestrial weatherability during the late Neoproterozoic may explain low temperature, increases in ocean phosphate, ocean sulfate, and atmospheric oxygen concentration at this time. PMID:24927553

Mills, Benjamin; Lenton, Timothy M.; Watson, Andrew J.

2014-01-01

384

Intermittent Astrophysical Radiation Sources and Terrestrial Life  

NASA Astrophysics Data System (ADS)

Terrestrial life is exposed to a variety of radiation sources. Astrophysical observations suggest that strong excursions in cosmic ray flux and spectral hardness are expected. Gamma-ray bursts and supernovae are expected to irradiate the atmosphere with keV to GeV photons at irregular intervals. Supernovae will produce large cosmic ray excursions, with time development varying with distance from the event. Large fluxes of keV to MeV protons from the Sun pose a strong threat to electromagnetic technology. The terrestrial record shows cosmogenic isotope excursions which are consistent with major solar proton events, and there are observations of G-stars suggesting that the rate of such events may be much higher than previously assumed. In addition there are unknown and unexplained astronomical transients which may indicate new classes of events. The Sun, supernovae, and gamma-ray bursts are all capable of producing lethal fluences, and some are expected on intervals of 10^8 years or so. The history of life on Earth is filled with mass extinctions at a variety of levels of intensity. Most are not understood. Astrophysical radiation may play a role, particularly from large increases in muon irradiation on the ground, and changes in atmospheric chemistry which deplete ozone, admitting increased solar UVB. UVB is strongly absorbed by DNA and proteins, and breaks the chemical bonds---it is a known carcinogen. High muon fluxes will also be damaging to such molecules, but experiments are needed to pin down the rate. Solar proton events which are not directly dangerous for the biota may nevertheless pose a major threat to modern electromagnetic technology through direct impact on satellites and magnetic induction of large currents in power grids, disabling transformers. We will look at the kind of events that are expected on timescales from human to geological, and their likely consequences.

Melott, Adrian

2013-04-01

385

Stop hitting yourself: did most terrestrial impactors originate from the terrestrial planets?  

NASA Astrophysics Data System (ADS)

Although the asteroid belt is the main source of impactors in the inner solar system today, it contains only 0.0006 Earth mass, or 0.05 Lunar mass. While the asteroid belt would have been more massive when it formed, it is unlikely to have had greater than 0.5 Lunar mass since the formation of Jupiter and the dissipation of the solar nebula. By comparison, giant impacts onto the terrestrial planets typically release debris equal to several per cent of the planets mass. The Moon-forming impact on Earth and the dichotomy forming impact on Mars, to consider but two of these major events, released 1.3 and 0.3 Lunar mass in debris respectively, many times the mass of the present day asteroid belt. This escaping impact debris is less long lived than the main asteroid belt, as it is injected on unstable, planet-crossing orbits, but this same factor also increases the impact probability with the terrestrial planets and asteroids. We show that as a result terrestrial ejecta played a major role in the impact history of the early inner solar system, and we expect the same is also likely to be true in other planetary systems.

Jackson, Alan; Asphaug, Erik; Elkins-Tanton, Linda

2014-11-01

386

Climbing, brachiation, and terrestrial quadrupedalism: historical precursors of hominid bipedalism.  

PubMed

The vertical-climbing account of the evolution of locomotor behavior and morphology in hominid ancestry is reexamined in light of recent behavioral, anatomical, and paleontological findings and a more firmly established phylogeny for the living apes. The behavioral record shows that African apes, when arboreal, are good vertical climbers, and that locomotion during traveling best separates the living apes into brachiators (gibbons), scrambling/ climbing/brachiators (orangutans), and terrestrial quadrupeds (gorillas and chimpanzees). The paleontological record documents frequent climbing as an ancestral catarrhine ability, while a reassessment of the morphology of the torso and forelimb in living apes and Atelini suggests that their shared unique morphological pattern is best explained by brachiation and forelimb suspensory positional behavior. Further, evidence from the hand and foot points to a terrestrial quadrupedal phase in hominoid evolution prior to the adoption of bipedalism. The evolution of positional behavior from early hominoids to hominids appears to have begun with an arboreal quadrupedal-climbing phase and proceeded though an orthograde, brachiating, forelimb-suspensory phase, which was in turn followed by arboreal and terrestrial quadrupedal phases prior to the advent of hominid bipedality. The thesis that protohominids climbed down from the trees to become terrestrial bipeds needs to be reexamined in light of a potentially long history of terrestriality in the ancestral protohominid. PMID:8876814

Gebo, D L

1996-09-01

387

Evaluation of a terrestrial carbon cycle submodel in an Earth system model using networks of eddy covariance observations  

NASA Astrophysics Data System (ADS)

ABSTRACT Improvement of terrestrial submodels in Earth system models (ESMs) is important to reduce uncertainties in future projections of global carbon cycle and climate. Since these submodels lack detailed validation, evaluation of terrestrial submodels using networks of field observations is necessary. The purpose of this study is to improve an ESM by refining a terrestrial submodel using eddy covariance observations. We evaluated the terrestrial submodel (MOSES2/TRIFFID) included in the UVic Earth System Climate Model (UVic-ESCM) and tested the effects of terrestrial submodel improvements on future projection of carbon cycle and climate. First, we evaluated the terrestrial submodel as an off-line mode at point scales using 48 eddy covariance observation data, and improved it through fixing model parameters and structures. The terrestrial submodel was improved with the reduction of the root mean square error and the closer simulation of the seasonal carbon fluxes. Second, using the UVic-ESCM with the improved terrestrial submodel, we confirmed model improvement at most observation sites. The terrestrial submodel refinement also affected future projections; the UVic-ESCM with the improved terrestrial submodel simulated 100 ppmv lower atmospheric CO2 concentration in 2100 compared with the default UVic-ESCM. Our study underscores the importance of refinement of terrestrial submodels in ESM simulations.