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Sample records for continental thermal regime

  1. CSDP: The seismology of continental thermal regimes

    SciTech Connect

    Aki, K.

    1990-05-01

    This is a progress report for the past one year of research (year 3 of 5-year project) under the project titled CSDP: Seismology of Continental Thermal Regime'', in which we proposed to develop seismological interpretation theory and methods applicable to complex structures encountered in continental geothermal areas and apply them to several candidate sites for the Continental Scientific Drilling Project. The past year has been extremely productive especially in the area of interpretation theory, including the following two major break-throughs. One is the derivation of an integral equation for time-dependent power spectra, which unified all the existing theories on seismic scattering (including the radiative transfer theory for total energy and single and multiple scattering theories based on the ray approach) and offers more complete and economical solutions to the problems of seismic scattering and attenuation. The other is the new formula for synthetic seismograms for layered media with irregular interfaces, combining the T-matrix method for an arbitrary shaped inclusion and the method of global generalized reflection/transmission coefficients for layered media. Both breakthroughs will enable us to deal with seismic observations in complex earth structures more efficiently and accurately. In the area of experimental studies, we discovered seismic guided waves trapped in the San Andreas fault near Parkfield, California. 54 refs., 14 figs.

  2. CSDP: Seismology of continental thermal regime

    SciTech Connect

    Aki, K.

    1989-04-01

    This is a progress report for the past one year of research (year 2 of 5-year project) under the project titled CSDP: Seismology of Continental Thermal Regime'', in which we proposed to develop seismological interpretation theory and methods applicable to complex structures encountered in continental geothermal areas and apply them to several candidate sites for the Continental Scientific Drilling Project. During the past year, two Ph.D. thesis works were completed under the present project. One is a USC thesis on seismic wave propagation in anisotropic media with application to defining fractures in the earth. The other is a MIT thesis on seismic Q and velocity structure for the magma-hydrothermal system of the Valles Caldera, New Mexico. The P.I. co-organized the first International Workshop on Volcanic Seismology at Capri, Italy in October 1988, and presented the keynote paper on the state-of-art of volcanic seismology''. We presented another paper at the workshop on Assorted Seismic Signals from Kilauea Volcano, Hawaii. Another international meeting, namely, the Chapman Conference on seismic anisotropy in the earth's crust at Berkeley, California in May 1988, was co-organized by the co-P.I. (P.C.L), and we presented our work on seismic waves in heterogeneous and anisotropic media. Adding the publications and presentations made in the past year to the list for the preceding year, the following table lists 21 papers published, submitted or presented in the past two years of the present project. 65 refs., 334 figs., 1 tab.

  3. Continental Scientific Drilling (CSD): Technology Barriers to Deep Drilling Studies in Thermal Regimes

    SciTech Connect

    Kolstad, George A.; Rowley, John C.

    1987-01-16

    This report is the proceedings of a workshop. The primary thrust of these discussion was to identify the major key technology barriers to the Department of Energy (DOE) supported Thermal Regimes CSD projects and to set priorities for research and development. The major technological challenge is the high temperature to be encountered at depth. Specific problems derived from this issue were widely recognized among the participants and are reflected in this summary. A major concern for the projected Thermal Regimes CSD boreholes was the technology required for continuous coring, in contrast to that required for drilling without core or spot coring. Current commercial technology bases for these two techniques are quite different. The DOE has successfully fielded projects that used both technologies, i.e, shallow continuous coring (Inyo Domes and Valles Caldera) and deeper drilling with spot cores (Imperial Valley-SSSDP). It was concluded that future scientific objectives may still require both approaches, but continuous coring is the most likely requirement in the near term. (DJE-2005)

  4. First CSDP (Continental Scientific Drilling Program)/thermal regimes core hole project at Valles Caldera, New Mexico (VC-1): Drilling report

    SciTech Connect

    Rowley, J.; Hawkins, W.; Gardner, J.

    1987-02-01

    This report is a review and summary of the core drilling operations of the first Valles Caldera research borehole (VC-1) under the Thermal Regimes element of the Continental Scientific Drilling Program (CSDP). The project is a portion of a broader program that seeks to answer fundamental scientific questions about magma, rock/water interactions, and volcanology through shallow (<1-km) core holes at Long Valley, California; Salton Sea, California; and the Valles Caldera, New Mexico. The report emphasizes coring operations with reference to the stratigraphy of the core hole, core quality description, core rig specifications, and performance. It is intended to guide future research on the core and in the borehole, as well as have applications to other areas and scientific problems in the Valles Caldera. The primary objectives of this Valles Caldera coring effort were (1) to study the hydrogeochemistry of a subsurface geothermal outflow zone of the caldera near the source of convective upflow, (2) to obtain structural and stratigraphic information from intracaldera rock formations in the southern ring-fracture zone, and (3) to obtain continuous core samples through the youngest volcanic unit in Valles Caldera, the Banco Bonito rhyolite (approximately 0.1 Ma). All objectives were met. The high percentage of core recovery and the excellent quality of the samples are especially notable. New field sample (core) handling and documentation procedures were successfully utilized. The procedures were designed to provide consistent field handling of the samples and logs obtained through the national CSDP.

  5. Thermal models pertaining to continental growth

    NASA Technical Reports Server (NTRS)

    Morgan, Paul; Ashwal, Lew

    1988-01-01

    Thermal models are important to understanding continental growth as the genesis, stabilization, and possible recycling of continental crust are closely related to the tectonic processes of the earth which are driven primarily by heat. The thermal energy budget of the earth was slowly decreasing since core formation, and thus the energy driving the terrestrial tectonic engine was decreasing. This fundamental observation was used to develop a logic tree defining the options for continental growth throughout earth history.

  6. The thermal regime of Venus

    SciTech Connect

    Solomatov, V.S.; Zharkov, V.N. )

    1990-04-01

    In the present numerical modeling study of the thermal evolution of Venus, the mantle is taken to be composed of independently convecting upper and lower mantles. A novel parameterization is used which takes into account recent numerical investigations in media with complex rheology. The parameters of the convecting planet in the asymptotic regime do not depend on initial conditions, and are ascertained analytically. Convection in the lower part of the crust is demonstrated to be involved in regions having specific crustal composition; heat transfer to the surface is primarily via advection by magmas that are produced by melting of the lower layers of the crust. 50 refs.

  7. Coupled and decoupled regimes of continental collision: Numerical modeling

    NASA Astrophysics Data System (ADS)

    Faccenda, M.; Minelli, G.; Gerya, T. V.

    2009-02-01

    Useful geodynamic distinction of continental collision zones can be based on the degree of rheological coupling of colliding plates. Coupled active collision zones (which can be either retreating or advancing) are characterized by a thick crustal wedge and compressive stresses (i.e. Himalaya and Western Alps), while decoupled end-members (which are always retreating) are defined by a thin crustal wedge and bi-modal distribution of stresses (i.e., compressional in the foreland and extensional in the inner part of the orogen, Northern Apennines). In order to understand physical controls defining these different geodynamic regimes we conducted a 2D numerical study based on finite-differences and marker-in-cell techniques. In our experiments we systematically varied several major parameters responsible for the degree of rheological coupling between plates during collision such as convergence rate, crustal rheology and effective velocity of upward propagation of aqueous fluids and melts in the mantle wedge. Low convergence rates and fluids/melts propagation velocities favor continuous coupling and convergence between the plates. Coupled collision zones are characterized by continuous accretion of the weak upper continental crust resulting in the development of a thick and broad crustal wedge, by hot temperature in the inner parts of the orogen due to radiogenic heating of the thickened crust, by compressive orogenic stresses and appearance of a double seismogenic (brittle) layer involving upper crust and sub-Moho mantle. In contrast high convergence rates and fluid/melt percolation velocities produce efficient weakening of the mantle wedge and of the subduction channel triggering complete decoupling of two plates, mantle wedging into the crustal wedge and retreating style of collision. The evolution of fully decoupled collision zones are characterized by the disruption of the accretionary wedge, formation of an extensional basin in the inner part of the orogen and

  8. The Thermal Regime Around Buried Submarine High-Voltage Cables

    NASA Astrophysics Data System (ADS)

    Emeana, C. J.; Dix, J.; Henstock, T.; Gernon, T.; Thompson, C.; Pilgrim, J.

    2015-12-01

    The expansion of offshore renewable energy infrastructure and the desire for "trans-continental shelf" power transmission, all require the use of submarine High Voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70oC and are typically buried at depths of 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the thermal properties of near surface shelf sediments are poorly understood and this increases the uncertainty in determining the required cable current ratings, cable reliability and the potential effects on the sedimentary environments. We present temperature measurements from a 2D laboratory experiment, designed to represent a buried, submarine HV cable. We used a large (2.5 m-high) tank, filled with water-saturated ballotini and instrumented with 120 thermocouples, which measured the time-dependent 2D temperature distributions around the heat source. The experiments use a buried heat source to represent a series of realistic cable surface temperatures with the aim for identifying the thermal regimes generated within typical non-cohesive shelf sediments: coarse silt, fine sand and very coarse sand. The steady state heat flow regimes, and normalised and radial temperature distributions were assessed. Our results show that at temperatures up to 60°C above ambient, the thermal regimes are conductive for the coarse silt sediments and convective for the very coarse sand sediments even at 7°C above ambient. However, the heat flow pattern through the fine sand sediment shows a transition from conductive to convective heat flow at a temperature of approximately 20°C above ambient. These findings offer an important new understanding of the thermal regimes associated with submarine HV cables buried in different substrates and has huge impacts on cable ratings as the IEC 60287 standard only considers conductive heat flow as well as other potential near surface impacts.

  9. Mercury's thermal evolution and core crystallization regime

    NASA Astrophysics Data System (ADS)

    Rivoldini, A.; Van Hoolst, T.; Dumberry, M.; Steinle-Neumann, G.

    2015-10-01

    Unlike the Earth, where the liquid core isentrope is shallower than the core liquidus, at the lower pressures inside Mercury's core the isentrope can be steeper than the melting temperature. As a consequence, upon cooling, the isentrope may first enter a solid stability field near the core mantle boundary and produce ironrich snow that sinks under gravity and produces buoyant upwellings of iron depleted fluid. Similar to bottom up crystallization, crystallization initiated near the top might generate sufficient buoyancy flux to drive magnetic field generation by compositional convection.In this study we model Mercury's thermal evolution by taking into account the formation of iron-rich snow to assess when the conditions for an internally magnetic field can be satisfied. We employ a thermodynamic consistent description of the iron high-pressure phase diagram and thermoelastic properties of iron alloys as well as the most recent data about the thermal conductivity of core materials. We use a 1-dimensional parametrized thermal evolution model in the stagnant lid regime for the mantle (e.g. [1]) that is coupled to the core. The model for the mantle takes into account the formation of the crust due to melting at depth. Mantle convection is driven by heat producing radioactive elements, heat loss from secular cooling and from the heat supplied by the core. The heat generated inside the core is mainly provided from secular cooling, from the latent heat released at iron freezing, and from gravitational energy resulting form the release of light elements at the inner core-outer core boundary as well as from the sinking of iron-rich snow and subsequent upwellings of light elements in the snow zone. If the heat flow out of the core is smaller than the heat transported along the core isentrope a thermal boundary will from at the top of the outer core. To determine the extension of the convecting region inside the liquid core we calculate the convective power [2]. Finally, we

  10. Thermal regime of permafrost at Prudhoe Bay, Alaska

    USGS Publications Warehouse

    Lachenbruch, A.H.; Sass, J.H.; Marshall, B.V.; Moses, T.H.

    1982-01-01

    Temperature measurements through permafrost in the oil field at Prudhoe Bay, Alaska, combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime. A sharp contrast in temperature gradient at ~600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady-state conditions. Interpretation of the gradient contrast in terms of a simple model for the conductivity of an aggregate yields the mean ice content and thermal conductivities for the frozen and thawed sections (8.1 and 4.7 mcal/cm sec ?C, respectively). These results yield a heat flow of ~1.3 HFU which is similar to other values on the Alaskan Arctic Coast; the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice-rich sediments. Curvature in the upper 160 m of the temperature profiles represents a warming of ~1.8?C of the mean surface temperature, and a net accumulation of 5-6 kcal/cm 2 by the solid earth surface during the last 100 years or so. Rising sea level and thawing sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20,000 years, inundating a portion of the continental shelf that is presently the target of intensive oil exploration. A simple conduction model suggests that this recently inundated region is underlain by near-melting ice-rich permafrost to depths of 300-500 m; its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production. With confirmation of the permafrost configuration by offshore drilling, heat-conduction models can yield reliable new information on the chronology of arctic shorelines.

  11. The thermal regime around buried submarine high-voltage cables

    NASA Astrophysics Data System (ADS)

    Emeana, C. J.; Hughes, T. J.; Dix, J. K.; Gernon, T. M.; Henstock, T. J.; Thompson, C. E. L.; Pilgrim, J. A.

    2016-08-01

    The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine high-voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70 °C and are typically buried 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near-surface sediments are poorly understood. We present temperature measurements from a 2-D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments-coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m2) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples to measure the time-dependent 2-D temperature distributions. The observed and corresponding Finite Element Method simulations of the steady state heat flow regimes and normalized radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10 °C up to 40 cm from the source of 60 °C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between cf. 20 and 36 °C above ambient, with >10 °C heat increases occurring over a metre from the source of 55 °C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (cf. 7 °C) operating temperatures and reaching temperatures of up to 18 °C above ambient at a metre from the source at surface temperatures of only 18 °C. These findings are important for the surrounding near

  12. The thermal regime around buried submarine high-voltage cables

    NASA Astrophysics Data System (ADS)

    Emeana, C. J.; Hughes, T. J.; Dix, J. K.; Gernon, T. M.; Henstock, T. J.; Thompson, C. E. L.; Pilgrim, J. A.

    2016-08-01

    The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine high-voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70 °C and are typically buried 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near-surface sediments are poorly understood. We present temperature measurements from a 2-D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments—coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m2) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples to measure the time-dependent 2-D temperature distributions. The observed and corresponding Finite Element Method simulations of the steady state heat flow regimes and normalized radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10 °C up to 40 cm from the source of 60 °C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between cf. 20 and 36 °C above ambient, with >10 °C heat increases occurring over a metre from the source of 55 °C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (cf. 7 °C) operating temperatures and reaching temperatures of up to 18 °C above ambient at a metre from the source at surface temperatures of only 18 °C. These findings are important for the surrounding near

  13. Mercury's thermal evolution and core crystallization regime

    NASA Astrophysics Data System (ADS)

    Rivoldini, Attilio; Dumberry, Mathieu; Van Hoolst, Tim; Steinle-Neumann, Gerd

    2015-04-01

    Unlike the Earth, where the liquid core isentrope is less steep than the core melting temperature, at the lower pressures inside Mercury's core the isentrope can be steepper than the melting temperature. As a consequence, upon cooling, the isentrope may first cross the melting temperature near the core mantle boundary and produce iron-rich snow that sinks under gravity and produces buoyant upwellings of iron depleted fluid. Similar to bottom up crystallization, top down crystallization is expected to generate sufficient buoyancy flux to drive magnetic field generation by compositional convection. In this study we model Mercury's thermal evolution by taking into account the formation of iron-rich snow to assess when the conditions for internally magnetic field can be satisfied. We employ a thermodynamic consistent description of the iron high pressure phase diagram and thermoelastic properties of iron alloys as well as the most recent data about the thermal conductivity of core materials.

  14. Vegetation management with fire modifies peatland soil thermal regime.

    PubMed

    Brown, Lee E; Palmer, Sheila M; Johnston, Kerrylyn; Holden, Joseph

    2015-05-01

    Vegetation removal with fire can alter the thermal regime of the land surface, leading to significant changes in biogeochemistry (e.g. carbon cycling) and soil hydrology. In the UK, large expanses of carbon-rich upland environments are managed to encourage increased abundance of red grouse (Lagopus lagopus scotica) by rotational burning of shrub vegetation. To date, though, there has not been any consideration of whether prescribed vegetation burning on peatlands modifies the thermal regime of the soil mass in the years after fire. In this study thermal regime was monitored across 12 burned peatland soil plots over an 18-month period, with the aim of (i) quantifying thermal dynamics between burned plots of different ages (from <2 to 15 + years post burning), and (ii) developing statistical models to determine the magnitude of thermal change caused by vegetation management. Compared to plots burned 15 + years previously, plots recently burned (<2-4 years) showed higher mean, maximum and range of soil temperatures, and lower minima. Statistical models (generalised least square regression) were developed to predict daily mean and maximum soil temperature in plots burned 15 + years prior to the study. These models were then applied to predict temperatures of plots burned 2, 4 and 7 years previously, with significant deviations from predicted temperatures illustrating the magnitude of burn management effects. Temperatures measured in soil plots burned <2 years previously showed significant statistical disturbances from model predictions, reaching +6.2 °C for daily mean temperatures and +19.6 °C for daily maxima. Soil temperatures in plots burnt 7 years previously were most similar to plots burned 15 + years ago indicating the potential for soil temperatures to recover as vegetation regrows. Our findings that prescribed peatland vegetation burning alters soil thermal regime should provide an impetus for further research to understand the consequences of thermal regime

  15. Continental warming preceding the Palaeocene-Eocene thermal maximum.

    PubMed

    Secord, Ross; Gingerich, Philip D; Lohmann, Kyger C; Macleod, Kenneth G

    2010-10-21

    Marine and continental records show an abrupt negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene-Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to earlier warming with different origins. Yet pre-CIE warming is still uncertain. Disentangling the sequence of events before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, abrupt climate change. Here we show that continental warming of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE warming is also supported by a negative amplification of δ(13)C values in soil carbonates below the CIE. Our results suggest that at least two sources of warming-the earlier of which is unlikely to have been methane-contributed to the PETM.

  16. The continental lithosphere: Reconciling thermal, seismic, and petrologic data

    NASA Astrophysics Data System (ADS)

    Artemieva, Irina M.

    2009-04-01

    The goal of the present study is to extract non-thermal signal from seismic tomography models in order to distinguish compositional variations in the continental lithosphere and to examine if geochemical and petrologic constraints on global-scale compositional variations in the mantle are consistent with modern geophysical data. In the lithospheric mantle of the continents, seismic velocity variations of a non-thermal origin (calculated from global Vs seismic tomography data [Grand S.P., 2002. Mantle shear-wave tomography and the fate of subducted slabs. Philosophical Transactions of the Royal Society of London. Series A, 360, 2475-2491.; Shapiro N.M., Ritzwoller M.H. 2002. Monte-Carlo inversion for a global shear velocity model of the crust and upper mantle. Geophysical Journal International 151, 1-18.] and lithospheric temperatures [Artemieva I.M., Mooney W.D., 2001. Thermal structure and evolution of Precambrian lithosphere: A global study. Journal of Geophysical Research 106, 16387-16414.] show strong correlation with tectono-thermal ages and with regional variations in lithospheric thickness constrained by surface heat flow data and seismic velocities. In agreement with xenolith data, strong positive velocity anomalies of non-thermal origin (attributed to mantle depletion) are clearly seen for all of the cratons; their amplitude, however, varies laterally and decreases with depth, reflecting either a peripheral growth of the cratons in Proterozoic or their peripheral reworking. These cratonic regions where kimberlite magmas erupted show only weakly positive compositional velocity anomalies, atypical for the "intact" cratonic mantle. A reduction in the amplitude of compositional velocity anomalies in kimberlite provinces is interpreted to result from metasomatic enrichment (prior or during kimberlite emplacement) of the cratonic mantle, implying that xenolith data maybe non-representative of the "intact" cratonic mantle.

  17. The DOE Thermal Regimes Drilling Program through 1987

    SciTech Connect

    Not Available

    1988-07-01

    In response to strong endorsement from the scientific community, in the form of a report by the Continental Scientific Drilling Committee of the National Academy of Sciences (CSDC, 1984), the Office of Basic Energy Sciences of the DOE undertook a program of investigations of young magmatic intrusions and their associated thermal systems. To date, the effort has encompassed the first phases of a program to investigate the roots of active hydrothermal systems and has also investigated the thermal, chemical, and mechanical behavior of geologically recent (less than 600 years) magmatic extrusions. Shallow to intermediate-depth holes have been drilled and cored into hydrothermal systems in the silicic Valles and Long Valley calderas and at the crustal spreading center of the Salton Trough. These projects are briefly summarized here and are covered in greater detail in the accompanying appendices.

  18. Deep thermal structure and thickness of the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Jaupart, C.; Mareschal, J.; Kaminski, E.

    2002-12-01

    There is no doubt that cratonic lithosphere is much thicker than oceanic lithosphere, but large uncertainties remain on its thickness, deep thermal structure, physical properties (density, rheology) and composition. Heat flow and crustal heat production data in North America demonstrate that, in steady-state conditions, heat flow variations are essentially due to changes of crustal heat production. Crustal models in several different geological provinces and considerations on the thermal stability of the crust through geological time constrain the mantle heat flow to be in the range 11-16 mWm-2. For such low values, heat flow data are not sensitive to small, but significant, lateral variations of the mantle heat flow (≈ 20%). Downward extrapolation of temperature profiles requires knowledge of thermal conductivity and heat production in the lithospheric mantle. For a thick lithosphere, surface heat flow is not in equilibrium with the instantaneous heat production and basal heat flow, and surface measurements record a time-average. With current estimates of heat production in the lithospheric mantle (≈ 0.02 mWm-3), thermal models rule out that lithospheric thickness is greater than 330 km. Using heat flow data and other constraints on lithospheric temperatures, such as xenolith (P,T) equilibration conditions, one can only construct geotherms in a stable conductive layer. Thus, comparison with seismic constraints cannot be made without considering the dynamical interactions with the convective mantle. A small-scale convection model shows that temperatures at the base of the continental lithosphere may not be equal to those of the well-mixed (isentropic) oceanic convecting mantle. Constraints on deep lithospheric structure can also be obtained using thermal transients, as recorded for example by sedimentary accumulations in intracratonic basins. The stability of thick roots requires the lithospheric mantle to be compositionally buoyant. Localized thinning results

  19. Persistent Nature of Secondary Diurnal Modes of Precipitation over Oceanic and Continental Regimes

    NASA Technical Reports Server (NTRS)

    Yang, S.; Kuo, K.-S.; Smith, E.

    2007-01-01

    This investigation seeks a better understanding of the assorted mechanisms controlling the global distribution of precipitation diurnal variability based on the use of Tropical Rainfall Measuring Mission (TRMM) microwave radiometer and radar data. The horizontal distributions of precipitation's diurnal cycle are derived from eight years of TRMM Microwave Imager (TMI) and Precipitation Radar (PR) measurements involving three TRMM standard rain rate retrieval algorithms -- the resultant distributions analyzed at various spatiotemporal scales. The results reveal the prominent and expected late-evening to early-morning (LE-EM) precipitation maxima over oceans and the counterpart prominent and expected mid- to late-afternoon (MLA) maxima over continents. Moreover, and not generally recognized, the results reveal a widespread distribution of secondary maxima occurring over both oceans and continents -- maxima which generally mirror their counterpart regime's behavior. That is, many ocean regions exhibit clearcut secondary MLA precipitation maxima while many continental regions exhibit just as evident secondary LE-EM maxima. This investigation is the first comprehensive study of these globally prevalent secondary maxima and their widespread nature, a type of study only made possible when the analysis procedure is applied to a high-quality global-scale precipitation dataset. The characteristics of the secondary maxima are mapped and described on global grids using an innovative clock-face format, while a current study to be published at a later date provides physically-based explanations of the seasonal-regional distributions of the secondary maxima. In addition to an "explicit" maxima identification scheme, a "Fourier decomposition" maxima identification scheme is used to examine the amplitude and phase properties of the primary and secondary maxima -- as well as tertiary and quaternary maxima. Accordingly, the advantages, ambiguities, and pitfalls resulting from use of

  20. Laser ablation dynamics in metals: The thermal regime

    SciTech Connect

    Mezzapesa, F. P.; Brambilla, M.; Dabbicco, M.; Scamarcio, G.; Columbo, L. L.; Ancona, A.; Sibillano, T.

    2012-07-02

    We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

  1. Historical thermal regimes define limits to coral acclimatization.

    PubMed

    Howells, Emily J; Berkelmans, Ray; van Oppen, Madeleine J H; Willis, Bette L; Bay, Line K

    2013-05-01

    Knowledge of the degree to which corals undergo physiological acclimatization or genetic adaptation in response to changes in their thermal environment is crucial to the success of coral reef conservation strategies. The potential of corals to acclimatize to temperatures exceeding historical thermal regimes was investigated by reciprocal transplantation of Acropora millepora colonies between the warm central and cool southern regions of the Great Barrier Reef (GBR) for a duration of 14 months. Colony fragments retained at native sites remained healthy, whereas transplanted fragments, although healthy over initial months when temperatures remained within native thermal regimes, subsequently bleached and suffered mortality during seasonal temperature extremes. Corals hosting Symbiodinium D transplanted to the southern GBR bleached in winter and the majority suffered whole (40%; n=20 colonies) or partial (50%) mortality at temperatures 1.1 degrees C below their 15-year native minimum. In contrast, corals hosting Symbiodinium C2 transplanted to the central GBR bleached in summer and suffered whole (50%; n=10 colonies) or partial (42%) mortality at temperatures 2.5 degrees C above their 15-year native maximum. During summer bleaching, the dominant Symbiodinium type changed from C2 to D within corals transplanted to the central GBR. Corals transplanted to the cooler, southern GBR grew 74-80% slower than corals at their native site, and only 50% of surviving colonies reproduced, at least partially because of cold water bleaching of transplants. Despite the absence of any visual signs of stress, corals transplanted to the warmer, central GBR grew 52-59% more slowly than corals at their native site before the summer bleaching (i.e., from autumn to spring). Allocation of energy to initial acclimatization or reproduction may explain this pattern, as the majority (65%) of transplants reproduced one month earlier than portions of the same colonies retained at the southern

  2. Monitoring of thermal regime of permafrost in the coastal zone of Western Yamal

    NASA Astrophysics Data System (ADS)

    Vasiliev, A.

    2009-04-01

    Data on thermal regime of permafrost are required for estimation of the climate change influence on permafrost dynamics. Monitoring of thermal regime of permafrost was arranged in the area of weather station "Marre-Sale", western Yamal. In terms of geomorphology, the area of our observations belongs to the second and third marine terraces; the surface of these terraces has been partly modified by recent cryogenic processes. The elevation varies from 10 to 30 m a.s.l. Marine clays lie at the base of the geological section of the coastal deposits. Their upper part was eroded and uneven surface of marine sediments is overlain by continental sandy sediments. Marine clays are saline. In the southern part of study area, low accumulative islands are forming. Their heights above sea level do not exceed 0.5 meters, and during high tides their surface is covered by sea water. The sediments accumulating at these islands are saline silty clays. Western Yamal region is located within continuous permafrost zone with thickness of 150 to 200 meters. Study of thermal regime in the on-shore zone has been performed since 1979 using the 10-12-m-deep boreholes. In 2007, five boreholes were included in the work program of the Thermal State of Permafrost (TSP) project developed as a part of IPY scientific activities. According to TSP program, temperature sensors were installed at depths 2, 3, 5, and 10 meters; measurements have been performed every six hours. In this presentation, results of our observations related to climate change are discussed. For different terrain units, increase of mean annual permafrost temperature during the last 30 years has reached 0.6 to 1.5 deg. C. In the transit zone, monitoring of thermal regime have been performed since 2006. Sensors were installed at depths 0, 0.25, 0.6, 0.75, 1.25, 1.75, and 2.25 meters. The active layer depth here reaches 1.9 meters, thus the 2.25-m-sensor is located within permafrost. Monitoring data show the sharp increase in mean

  3. Thermal regimes of major volcanic centers: magnetotelluric constraints

    SciTech Connect

    Hermance, J.F.

    1987-11-13

    The focus of activity at this laboratory is on applying natural electromagnetic methods along with other geophysical techniques to studying the dynamical processes and thermal regimes associated with centers of major volcanic activity. We are presently emphasizing studies of the Long Valley/Mono Craters Volcanic Complex, the Cascades Volcanic Belt, and the Valles Caldera. This work addresses questions regarding geothermal energy, chemical transport of minerals in the crust, emplacement of economic ore deposits, and optimal siting of drill-holes for scientific purposes. In addition, since much of our work is performed in the intermontane sedimentary basins of the western US (along with testing our field-system in some of the graben structures in the Northeast), there is an application of these studies to developing exploration and interpretational strategies for detecting and delineating structures associated with hydrocarbon reserves.

  4. Thermal Evolution and Crystallisation Regimes of the Martian Core

    NASA Astrophysics Data System (ADS)

    Davies, C. J.; Pommier, A.

    2015-12-01

    Though it is accepted that Mars has a sulfur-rich metallic core, its chemical and physical state as well as its time-evolution are still unconstrained and debated. Several lines of evidence indicate that an internal magnetic field was once generated on Mars and that this field decayed around 3.7-4.0 Gyrs ago. The standard model assumes that this field was produced by a thermal (and perhaps chemical) dynamo operating in the Martian core. We use this information to construct parameterized models of the Martian dynamo in order to place constraints on the thermochemical evolution of the Martian core, with particular focus on its crystallization regime. Considered compositions are in the FeS system, with S content ranging from ~10 and 16 wt%. Core radius, density and CMB pressure are varied within the errors provided by recent internal structure models that satisfy the available geodetic constraints (planetary mass, moment of inertia and tidal Love number). We also vary the melting curve and adiabat, CMB heat flow and thermal conductivity. Successful models are those that match the dynamo cessation time and fall within the bounds on present-day CMB temperature. The resulting suite of over 500 models suggest three possible crystallization regimes: growth of a solid inner core starting at the center of the planet; freezing and precipitation of solid iron (Fe- snow) from the core-mantle boundary (CMB); and freezing that begins midway through the core. Our analysis focuses on the effects of core properties that are expected to be constrained during the forthcoming Insight mission.

  5. Minimal change of thermal continentality in Slovakia within the period 1961-2013

    NASA Astrophysics Data System (ADS)

    Vilček, Jozef; Škvarenina, Jaroslav; Vido, Jaroslav; Nalevanková, Paulína; Kandrík, Radoslav; Škvareninová, Jana

    2016-08-01

    Thermal continentality plays an important role not only in the basic characterisation of the climate in particular regions but also in the phytogeographic distribution of plants and ecosystem formation. Due to ongoing climate change, questions surrounding the changes of thermal continentality are very relevant. Therefore, the aim of this study is to investigate the characteristics of thermal continentality and its temporal changes in the Slovak Republic between the years of 1961 and 2013. The study was carried out on several meteorological stations selected in respect to the geographical and geomorphological heterogeneity of Slovakia. Our results show that the continentality of Slovakia increased in the period 1961 to 2013; however, this trend is not significant. These non-significant trends are confirmed at all the stations. Nevertheless, it is necessary to be aware of this signal, especially because these changes could cause changes in ecosystem formation in future.

  6. Continental accretion: contrasting Mesozoic and Early Proterozoic tectonic regimes in North America

    NASA Astrophysics Data System (ADS)

    Condie, Kent C.; Chomiak, Beverly

    1996-11-01

    Juvenile continental crust was accreted to southern and western North America during the Early Proterozoic and Mesozoic, respectively. Graywacke, granite, granodiorite, and basalt comprise most of the accreted Early Proterozoic crust, whereas graywacke, andesite, basalt, and granodiorite comprise most of the Mesozoic crust. In addition, carbonates, ultramafics, pelagic sediments, and tonalite/diorite are minor but important components in the juvenile Mesozoic crust, whereas rhyolites are important in the Early Proterozoic crust. Mesozoic supracrustal rocks vary significantly in chemical composition, while Early Proterozoic supracrustals have a limited compositional range and exhibit a linear relation between many element concentrations suggesting a genetic linkage between accreted terranes. Although SiO 2, Al 2O 3, FeO, and incompatible elements are more enriched in Early Proterozoic than in Mesozoic supracrustal rocks, negative Eu anomalies are typical of rocks of both ages. Early Proterozoic granitoids are enriched in LILE (large ion lithophile elements) compared to Mesozoic granitoids, and granitoids of both ages of are enriched in LILE and have larger Eu anomalies than associated supracrustal rocks. Accreted Mesozoic upper crust is similar to andesite in chemical composition, and the bulk crust is similar to basaltic andesite. In contrast, accreted Early Proterozoic upper crust and bulk crust are similar to granodiorite and andesite, respectively. Incompatible elements are depleted in the Mesozoic compared to the Early Proterozoic crust, but both crustal types have negative NbTa anomalies. Depending on the composition assumed for the lower crust, both ages of crust have either very small or negligible Eu anomalies. Lifespans of the Early Proterozoic terranes (time interval between oldest rocks in a terrane and its collision with North America) are 20-80 My, whereas lifespans of Mesozoic terranes are 50-500 My, with most falling between 50 and 200 My. Within

  7. Thermal and mechanical structure of the upper mantle: A comparison between continental and oceanic models

    NASA Technical Reports Server (NTRS)

    Froidevaux, C.; Schubert, G.; Yuen, D. A.

    1976-01-01

    Temperature, velocity, and viscosity profiles for coupled thermal and mechanical models of the upper mantle beneath continental shields and old ocean basins show that under the continents, both tectonic plates and the asthenosphere, are thicker than they are beneath the oceans. The minimum value of viscosity in the continental asthenosphere is about an order of magnitude larger than in the shear zone beneath oceans. The shear stress or drag underneath continental plates is also approximately an order of magnitude larger than the drag on oceanic plates. Effects of shear heating may account for flattening of ocean floor topography and heat flux in old ocean basins.

  8. Thermal regimes of major volcanic centers: Magnetotelluric constraints

    SciTech Connect

    Hermance, J.F.

    1989-10-02

    The interpretation of geophysical/electromagnetic field data has been used to study dynamical processes in the crust beneath three of the major tectono-volcanic features in North America: the Long Valley/Mono Craters Volcanic Complex in eastern California, the Cascades Volcanic Belt in Oregon, and the Rio Grande Rift in the area of Socorro, New Mexico. Primary accomplishments have been in the area of creating and implementing a variety of 2-D generalized inverse computer codes, and the application of these codes to fields studies on the basin structures and he deep thermal regimes of the above areas. In order to more fully explore the space of allowable models (i.e. those inverse solutions that fit the data equally well), several distinctly different approaches to the 2-D inverse problem have been developed: (1) an overdetermined block inversion; (2) an overdetermined spline inverstion; (3) a generalized underdetermined total inverse which allows one to tradeoff certain attributes of their model, such as minimum structure (flat models), roughness (smooth models), or length (small models). Moreover, we are exploring various approaches for evaluating the resolution model parameters for the above algorithms. 33 refs.

  9. The Argentine Continental Margin: Rift Basins, Crustal Architecture, and Sedimentation Regime

    NASA Astrophysics Data System (ADS)

    Neben, S.; Franke, D.; Hinz, K.; Meyer, H.; Roeser, H. A.; Schreckenberger, B.; Nevistic, V. A.; Mancilla, O.

    2001-12-01

    With the objective to contribute to a better understanding of the processes of rifting and magmatism/volcanism during the Early Cretaceous breakup of Gondwana, the Federal Institute for Geosciences and Natural Resources (BGR) acquired 12,000 km of MCS data and two wide-angle reflection/refraction lines on the Argentine continental margin between 38° S and 44° S in 1998/1999. The new seismic data document the presence of a narrow, north-east striking half-graben system beneath the present upper slope. This buried half-graben system developed during the final stage of rifting in Early Cretaceous time, whereas the east-west trending Colorado-Basin probably formed earlier. However, this wide sedimentary basin was superimposed by the rifting process that led to the opening of the South Atlantic. Continental breakup and initial sea-floor spreading were accompanied by large-scale magmatism and volcanism manifested in the seismic data by a huge wedge of seaward dipping reflectors (SDRS), and a distinct high-velocity (average value 7.3 km/s) lower crustal body beneath the SDRS. Emplacement of the deeply buried, 60-120km wide SDRS was episodic documented by at least three superimposed SDRS units. The drift deposits, locally more than 6,000m thick, and subdivided by five seismic unconformities, were mapped along the shelf, slope, and deep sea.

  10. Numerical simulation of thermal-hydraulic generators running in a single regime

    NASA Astrophysics Data System (ADS)

    Chioreanu, Nicolae; Mitran, Tudor; Rus, Alexandru; Beles, Horia

    2014-06-01

    The paper presents the basis for the design of thermal-hydraulic generators running in a single regime. The thermal-hydraulic generators in a single regime running represent an absolute novelty worldwide (a pioneer invention). Based on the methodology concerning this subject, the design calculus for an experimental model was developed.

  11. An objective and parsimonious approach for classifying natural flow regimes at a continental scale

    USGS Publications Warehouse

    Archfield, Stacey A.; Kennen, Jonathan G.; Carlisle, Daren M.; Wolock, David M.

    2014-01-01

    Hydro-ecological stream classification-the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat-has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to understand similarity in ecological streamflow response. This novel classification approach uses seven fundamental daily streamflow statistics (FDSS) rather than winnowing down an uncorrelated subset from 200 or more ecologically relevant streamflow statistics (ERSS) commonly used in hydro-ecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classification groups derived from the seven FDSS. It is further shown that classification based solely on the 33 ERSS generally does a poorer job in grouping similar streamgauges than the classification based on the seven FDSS. This new classification approach has the additional advantages of overcoming some of the subjectivity associated with the selection of the classification variables and provides a set of robust continental-scale classes of US streamgauges. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  12. Power signatures of electric field and thermal switching regimes in memristive SET transitions

    NASA Astrophysics Data System (ADS)

    Mickel, Patrick R.; Hughart, David; Lohn, Andrew J.; Gao, Xujiao; Mamaluy, Denis; Marinella, Matthew J.

    2016-06-01

    We present a study of the ‘snap-back’ regime of resistive switching hysteresis in bipolar TaO x memristors, identifying power signatures in the electronic transport. Using a simple model based on the thermal and electric field acceleration of ionic mobilities, we provide evidence that the ‘snap-back’ transition represents a crossover from a coupled thermal and electric-field regime to a primarily thermal regime, and is dictated by the reconnection of a ruptured conducting filament. We discuss how these power signatures can be used to limit filament radius growth, which is important for operational properties such as power, speed, and retention.

  13. The mantle wedge's transient 3-D flow regime and thermal structure

    NASA Astrophysics Data System (ADS)

    Davies, D. R.; Le Voci, G.; Goes, S.; Kramer, S. C.; Wilson, C. R.

    2016-01-01

    Arc volcanism, volatile cycling, mineralization, and continental crust formation are likely regulated by the mantle wedge's flow regime and thermal structure. Wedge flow is often assumed to follow a regular corner-flow pattern. However, studies that incorporate a hydrated rheology and thermal buoyancy predict internal small-scale-convection (SSC). Here, we systematically explore mantle-wedge dynamics in 3-D simulations. We find that longitudinal "Richter-rolls" of SSC (with trench-perpendicular axes) commonly occur if wedge hydration reduces viscosities to Pa s, although transient transverse rolls (with trench-parallel axes) can dominate at viscosities of Pa s. Rolls below the arc and back arc differ. Subarc rolls have similar trench-parallel and trench-perpendicular dimensions of 100-150 km and evolve on a 1-5 Myr time-scale. Subback-arc instabilities, on the other hand, coalesce into elongated sheets, usually with a preferential trench-perpendicular alignment, display a wavelength of 150-400 km and vary on a 5-10 Myr time scale. The modulating influence of subback-arc ridges on the subarc system increases with stronger wedge hydration, higher subduction velocity, and thicker upper plates. We find that trench-parallel averages of wedge velocities and temperature are consistent with those predicted in 2-D models. However, lithospheric thinning through SSC is somewhat enhanced in 3-D, thus expanding hydrous melting regions and shifting dehydration boundaries. Subarc Richter-rolls generate time-dependent trench-parallel temperature variations of up to K, which exceed the transient 50-100 K variations predicted in 2-D and may contribute to arc-volcano spacing and the variable seismic velocity structures imaged beneath some arcs.

  14. Continental growth and mantle hydration as intertwined feedback cycles in the thermal evolution of Earth

    NASA Astrophysics Data System (ADS)

    Höning, Dennis; Spohn, Tilman

    2016-06-01

    A model of Earth's continental coverage and mantle water budget is discussed along with its thermal evolution. The model links a thermal evolution model based on parameterized mantle convection with a model of a generic subduction zone that includes the oceanic crust and a sedimentary layer as carriers of water. Part of the subducted water is used to produce continental crust while the remainder is subducted into the mantle. The total length of the subduction zones is calculated from the total surface area of continental crust assuming randomly distributed continents. The mantle viscosity is dependent of temperature and the water concentration. Sediments are generated by continental crust erosion, and water outgassing at mid-oceanic ridges closes the water cycle. We discuss the strongly coupled, non-linear model using a phase plane defined by the continental coverage and mantle water concentration. Fixed points are found in the phase plane at which the rates of change of both variables are zero. These fixed points evolve with time, but in many cases, three fixed points emerge of which two are stable and an intermediate point is unstable with respect to continental coverage. With initial conditions from a Monte-Carlo scheme we calculate evolution paths in the phase plane and find a large spread of final states that all have a mostly balanced water budget. The present day observed 40% continental surface coverage is found near the unstable fixed point. Our evolution model suggests that Earth's continental coverage formed early and has been stable for at least 1.5 Gyr. The effect of mantle water regassing (and mantle viscosity depending on water concentration) is found to lower the present day mantle temperature by about 120 K, but the present day mantle viscosity is affected little. The water cycle thus complements the well-known thermostat effect of viscosity and mantle temperature. Our results further suggest that the biosphere could impact the feedback cycles by

  15. Density of the continental roots: Compositional and thermal contributions

    USGS Publications Warehouse

    Kaban, M.K.; Schwintzer, P.; Artemieva, I.M.; Mooney, W.D.

    2003-01-01

    The origin and evolution of cratonic roots has been debated for many years. Precambrian cratons are underlain by cold lithospheric roots that are chemically depleted. Thermal and petrologic data indicate that Archean roots are colder and more chemically depleted than Proterozoic roots. This observation has led to the hypothesis that the degree of depletion in a lithospheric root depends mostly on its age. Here we test this hypothesis using gravity, thermal, petrologic, and seismic data to quantify differences in the density of cratonic roots globally. In the first step in our analysis we use a global crustal model to remove the crustal contribution to the observed gravity. The result is the mantle gravity anomaly field, which varies over cratonic areas from -100 to +100 mGal. Positive mantle gravity anomalies are observed for cratons in the northern hemisphere: the Baltic shield, East European Platform, and the Siberian Platform. Negative anomalies are observed over cratons in the southern hemisphere: Western Australia, South America, the Indian shield, and Southern Africa. This indicates that there are significant differences in the density of cratonic roots, even for those of similar age. Root density depends on temperature and chemical depletion. In order to separate these effects we apply a lithospheric temperature correction using thermal estimates from a combination of geothermal modeling and global seismic tomography models. Gravity anomalies induced by temperature variations in the uppermost mantle range from -200 to +300 mGal, with the strongest negative anomalies associated with mid-ocean ridges and the strongest positive anomalies associated with cratons. After correcting for thermal effects, we obtain a map of density variations due to lithospheric compositional variations. These maps indicate that the average density decrease due to the chemical depletion within cratonic roots varies from 1.1% to 1.5%, assuming the chemical boundary layer has the same

  16. Thermal Regime of High-power Laser Diodes

    NASA Astrophysics Data System (ADS)

    Bezotosnyi, V. V.; Krokhin, O. N.; Oleshchenko, V. A.; Pevtsov, V. F.; Popov, Yu. M.; Cheshev, E. A.

    We discuss the design and application perspectives of different crystal, ceramic and composite-type submounts with thermo-compensating properties as well as submounts from materials with high thermal conductivity for overcoming thermal problem in high-power laser diodes (LD) and improving thermal management of other high-power optoelectronic and electronic semiconductor devices. Thermal fields in high-power laser diodes were calculated in 3 D thermal model at CW operation for some heatsink designs taking into account the experimental dependence of laser total efficiency against pumping current in order to extend the range of reliable operation up to thermal loads 20-30 W and corresponding output optical power up to 15-20 W for 100 μm stripe laser diodes.

  17. The effects of thick sediment upon continental breakup: seismic imaging and thermal modeling of the Salton Trough, southern California

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Lowell, R. P.; Stock, J. M.; Fuis, G. S.; Driscoll, N. W.; Kell, A. M.; Kent, G. M.; Harding, A. J.; Gonzalez-Fernandez, A.; Lázaro-Mancilla, O.

    2015-12-01

    Continental rifting ultimately creates a deep accommodation space for sediment. When a major river flows into a late-stage rift, thick deltaic sediment can change the thermal regime and alter the mechanisms of extension and continental breakup. The Salton Trough, the northernmost rift segment of the Gulf of California plate boundary, has experienced the same extension as the rest of the Gulf, but is filled to sea level by sediment from the Colorado River. Unlike the southern Gulf, seafloor spreading has not initiated. Instead, seismicity, high heat flow, and minor volcanoes attest to ongoing rifting of thin, transitional crust. Recently acquired controlled-source seismic refraction and wide-angle reflection data in the Salton Trough provide constraints upon crustal architecture and active rift processes. The crust in the central Salton Trough is only 17-18 km thick, with a strongly layered but relatively one-dimensional structure for ~100 km in the direction of plate motion. The upper crust includes 2-4 km of Colorado River sediment. Crystalline rock below the sediment is interpreted to be similar sediment metamorphosed by the high heat flow and geothermal activity. Meta-sediment extends to at least 9 km depth. A 4-5 km thick layer in the middle crust is either additional meta-sediment or stretched pre-existing continental crust. The lowermost 4-5 km of the crust is rift-related mafic magmatic intrusion or underplating from partial melting in the hot upper mantle. North American lithosphere in the Salton Trough has been almost or completely rifted apart. The gap has been filled by ~100 km of new transitional crust created by magmatism from below and sedimentation from above. These processes create strong lithologic, thermal, and rheologic layering. While heat flow in the rift is very high, rapid sedimentation cools the upper crust as compared to a linear geotherm. Brittle extension occurs within new meta-sedimentary rock. The lower crust, in comparison, is

  18. Tectonic controls on hydrothermal mineralisation in hot continental crust: Thermal modelling and spatial analysis

    NASA Astrophysics Data System (ADS)

    Gessner, K.; Porwal, A.

    2009-04-01

    Hydrothermal ore deposits provide a record of excess energy flux and mass transfer in the Earth's lithosphere. The heterogeneous distribution of ore deposits in space and time provides a challenge to uniformitarian geodynamic and tectonic concepts, but unusual thermal and structural events often coincide with high mineral endowment. In the Australian Proterozoic continental backarcs and intracratonic rifts host large resources of base metals, gold, and uranium. We present thermal models and spatial analyses of mineral occurrences within the Mount Isa Inlier, an inverted Mesoproterozoic rift in northwest Queensland, Australia, to demonstrate how thermal structure, tectonic style and crustal scale fluid flow are related. In the Mount Isa Inlier, radiogenic heat production contributes significantly to present day surface heat flow, and Mesoproterozoic geotherms of 40°C km-1 in the upper crust can be inferred from lithosphere-scale conductive models. The combination of thick continental crust and high temperatures implies that localization of deformation was limited to a thin upper crustal layer. During rifting mid-crustal rocks intruded by syn-extensional granites were exhumed as metamorphic core complexes in strike-parallel linear basement belts. The resulting horizontal strength contrast between sedimentary basins and shallow basement domains became a focus for deformation during subsequent crustal shortening. Our spatial analysis of mineral occurrences demonstrates that epigenetic copper mineralization at Mount Isa correlates positively with steep fault zones bounding linear basement domains, and granites within these domains. Mineralization potential is greatly increased, because high permeability along steep fault zones enables hydrothermal fluid flow between magmatic, metamorphic and sedimentary reservoirs. We argue that the deformation behavior of hot continental lithosphere generates a favorable environment for hydrothermal mineralization by linking shallow

  19. The expanding thermal arc plasma: the low-flow regime

    NASA Astrophysics Data System (ADS)

    van de Sanden, M. C. M.; Tobin, J. A.

    1998-02-01

    This paper reports on experiments on an expanding thermal arc plasma using pure argon flows in the 50 to 500 sccm range. From pressure and voltage measurements on the arc it is verified that the arc plasma is still a thermal plasma at these low flows. Langmuir probe measurements of the radial profiles downstream using different flows and chamber pressures are presented and discussed. These measurements indicate an enhanced ion loss for low flows at constant pressure. The enhanced loss is explained by the increase in residence time and due to this a relatively large volumetric recombination. The sputter etch rate of PECVD deposited silicon oxide at 100 mTorr and 400 V DC bias is measured and compared with the results of the Langmuir probe.

  20. Long-term trends and regime shifts in sea surface temperature on the continental shelf of the northeast United States

    NASA Astrophysics Data System (ADS)

    Friedland, Kevin D.; Hare, Jonathan A.

    2007-11-01

    We investigated sea surface temperature (SST) variability over large spatial and temporal scales for the continental shelf region located off the northeast coast of the United States between Cape Hatteras, North Carolina, and the Gulf of Maine using the extended reconstruction sea surface temperature (ERSST) dataset. The ERSST dataset consists of 2°×2° (latitude and longitude) monthly mean values computed from in situ data derived from the International Comprehensive Ocean Atmosphere Data Set (ICOADS). Nineteen 2°×2° bins were chosen that cover the shelf region of interest between the years of 1854 and 2005. Mean annual and range of SST were examined using dynamic factor analysis to estimate trends in both parameters, while chronological clustering was used to determine temporal SST patterns and breakpoints in the time series that are believed to signal regime shifts in SST. Both SST and SST trend analysis show that interannual variability of SST fluctuations shows strong coherence between bins, with declining SST at the beginning of the last century, followed by increasing SST through 1950, and then rapidly decreasing between 1950 and mid-1960s, with somewhat warmer SST thereafter to present. Annual SST range decreases in a seaward direction for all bins, with strong coherence for interannual variability of range fluctuations between bins. The trend in SST range shows a decreasing range at the beginning of the last century followed by an increase in range from 1920 to the late-1980s, remaining high through present with some spatial variability. A more detailed spatial analysis was conducted by grouping the data into 7 regions using principal component analysis. We analyzed regional trends in mean annual SST, seasonal SST range (summer SST-winter SST), and normalized SST minima and maxima. Both the summer and winter seasons were also analyzed using the length of each season and amplitude of the warming and cooling season, respectively, along with the spring

  1. Thermal implications of metamorphism in greenstone belts and the hot asthenosphere-thick continental lithoshere paradox

    NASA Technical Reports Server (NTRS)

    Morgan, P.

    1986-01-01

    From considerations of secular cooling of the Earth and the slow decay of radiogenic heat sources in the Earth with time, the conclusion that global heat loss must have been higher in the Archean than at present seems inescapable. The mechanism by which this additional heat was lost and the implications of higher heat low for crustal temperatures are fundamental unknowns in our current understanding of Archean tectonics and geological processes. Higher heat loss implies that the average global geothermal gradient was higher in the Archean than at present, and the restriction of ultramafic komatiites to the Archean and other considerations suggests that the average temperature of the mantle was several hundred degrees hotter during the Archean than today. In contrast, there is little petrologic evidence that the conditions of metamorphism or crustal thickness (including maximum crustal thickness under mountains) were different in archean continental crust from the Phanerozoic record. Additionally, Archean ages have recently been determined for inclusions in diamonds from Cretaceous kimeberlites in South Africa, indicating temperatures of 900 to 1300 at depths of 150 to 215 km (45 to 65 kbar) in the Archean mantle, again implying relatively low geothermal gradients at least locally in the Archean. The thermal implications of metamorphism are examined, with special reference to greenstone belts, and a new thermal model of the continental lithosphere is suggested which is consistent with thick continental lithosphere and high asthenosphere temperatures in the Archean.

  2. Heat flow in eastern Egypt - The thermal signature of a continental breakup

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

    1985-01-01

    It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

  3. The cryptoendolithic microbial environment in the Ross Desert of Antarctica: mathematical models of the thermal regime

    NASA Technical Reports Server (NTRS)

    Nienow, J. A.; McKay, C. P.; Friedmann, E. I.

    1988-01-01

    Microbial activity in the Antarctic cryptoendolithic habitat is regulated primarily by temperature. Previous field studies have provided some information on the thermal regime in this habitat, but this type of information is limited by the remoteness of the site and the harsh climatic conditions. Therefore, a mathematical model of the endolithic thermal regime was constructed to augment the field data. This model enabled the parameters affecting the horizontal and altitudinal distribution of the community to be examined. The model predicts that colonization should be possible on surfaces with zenith angle less than 15 degrees. At greater zenith angles, colonization should be restricted to surfaces with azimuth angles less than 135 degrees or greater than 225 degrees. The upper elevational limit of the community should be less than 2,500 m. The thermal regime probably does not influence the zonation of the community within a rock.

  4. The cryptoendolithic microbial environment in the Ross Desert of Antarctica: mathematical models of the thermal regime.

    PubMed

    Nienow, J A; McKay, C P; Friedmann, E I

    1988-01-01

    Microbial activity in the Antarctic cryptoendolithic habitat is regulated primarily by temperature. Previous field studies have provided some information on the thermal regime in this habitat, but this type of information is limited by the remoteness of the site and the harsh climatic conditions. Therefore, a mathematical model of the endolithic thermal regime was constructed to augment the field data. This model enabled the parameters affecting the horizontal and altitudinal distribution of the community to be examined. The model predicts that colonization should be possible on surfaces with zenith angle less than 15 degrees. At greater zenith angles, colonization should be restricted to surfaces with azimuth angles less than 135 degrees or greater than 225 degrees. The upper elevational limit of the community should be less than 2,500 m. The thermal regime probably does not influence the zonation of the community within a rock. PMID:11538333

  5. The cryptoendolithic microbial environment in the Ross Desert of Antarctica: Mathematical models of the thermal regime.

    PubMed

    Nienow, J A; McKay, C P; Friedmann, E I

    1988-11-01

    Microbial activity in the Antarctic cryptoendolithic habitat is regulated primarily by temperature. Previous field studies have provided some information on the thermal regime in this habitat, but this type of information is limited by the remoteness of the site and the harsh climatic conditions. Therefore, a mathematical model of the endolithic thermal regime was constructed to augment the field data. This model enabled the parameters affecting the horizontal and altitudinal distribution of the community to be examined. The model predicts that colonization should be possible on surfaces with zenith angle less than 15°. At greater zenith angles, colonization should be restricted to surfaces with azimuth angles less than 135° or greater than 225°. The upper elevational limit of the community should be less than 2,500 m. The thermal regime probably does not influence the zonation of the community within a rock. PMID:24201713

  6. Modeling the spatiotemporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape

    NASA Astrophysics Data System (ADS)

    Kumar, Jitendra; Collier, Nathan; Bisht, Gautam; Mills, Richard T.; Thornton, Peter E.; Iversen, Colleen M.; Romanovsky, Vladimir

    2016-09-01

    Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to the atmosphere under warming climate scenarios. Ice-wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. This microtopography plays a critical role in regulating the fine-scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behavior under the current as well as changing climate. We present here an end-to-end effort for high-resolution numerical modeling of thermal hydrology at real-world field sites, utilizing the best available data to characterize and parameterize the models. We develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites near Barrow, Alaska, spanning across low to transitional to high-centered polygons, representing a broad polygonal tundra landscape. A multiphase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using a high-resolution lidar digital elevation model (DEM), microtopographic features of the landscape were characterized and represented in the high-resolution model mesh. The best available soil data from field observations and literature were utilized to represent the complex heterogeneous subsurface in the numerical model. Simulation results demonstrate the ability of the developed modeling approach to capture - without recourse to model calibration - several aspects of the complex thermal regimes across the sites, and provide insights into the critical role of polygonal tundra microtopography in regulating the thermal dynamics of the carbon-rich permafrost soils. Areas of significant disagreement between model results and observations highlight the importance of field-based observations of soil thermal and

  7. Thermal regime of the San Andreas fault near Parkfield, California

    USGS Publications Warehouse

    Sass, J.H.; Williams, C.F.; Lachenbruch, A.H.; Galanis, S.P.; Grubb, F.V.

    1997-01-01

    Knowledge of the temperature variation with depth near the San Andreas fault is vital to understanding the physical processes that occur within the fault zone during earthquakes and creep events. Parkfield is near the southern end of the Coast Ranges segment of the San Andreas fault. This segment has higher mean heat flow than the Cape Mendocino segment to the northwest or the Mojave segment to the southeast. Boreholes were drilled specifically for the U.S. Geological Survey's Parkfield earthquake prediction experiment or converted from other uses at 25 sites within a few kilometers of the fault near Parkfield. These holes, which range in depth from 150 to over 1500 m, were intended mainly for the deployment of volumetric strain meters, water-level recorders, and other downhole instruments. Temperature profiles were obtained from all the holes, and heat flow values were estimated from 17 of them. For a number of reasons, including a paucity of thermal conductivity data and rugged local topography, the accuracy of individual determinations was not sufficiently high to document local variations in heat flow. Values range from 54 to 92 mW m-2, with mean and 95% confidence limits of 74 ?? 4 mW m-2. This mean is slightly lower than the mean (83 ?? 3) of 39 previously published values from the central Coast Ranges, but it is consistent with the overall pattern of elevated heat flow in the Coast Ranges, and it is transitional to the mean of 68 ?? 2 mW m-2 that characterizes the Mojave segment of the San Andreas fault immediately to the south. The lack of a heat flow peak near the fault underscores the absence of a frictional thermal anomaly and provides additional support for a very small resolved shear stress parallel to the San Andreas fault and the nearly fault-normal maximum compressive stress observed in this region. Estimates of subsurface thermal conditions indicate that the seismic-aseismic transition for the Parkfield segment corresponds to temperatures in the

  8. Thermal regimes in the Chukchi Sea from 1941-present

    NASA Astrophysics Data System (ADS)

    Luchin, Vladimir; Panteleev, Gleb

    2014-05-01

    The summer (June-October) temperature observations in the surface and subsurface (20m-bottom) Chukchi Sea layers collected from 1941-present have been analyzed using the self-consistent data recovery procedure based on correlation analysis and iterative empirical orthogonal function (EOF) decomposition. The analysis of the surface and subsurface EOFs identified "cold", "normal", and "warm" thermal states with variability of 2-4 years, and also 7-8 years. We found that the Chukchi Sea water temperature has gradually increased since 1941. Warming in the surface layer since 1941 has been minimal in the Bering Strait (0.8ºC) and maximalin Long Strait (2-2.4ºC). In the subsurface layer, the temperature increase is about half as much; minimal (0.2-0.5ºC) in Long Strait and rather uniform (0.7-1ºC) for the remaining Chukchi Sea. Analysis of the satellite sea surface height anomaly data shows that during the "warm" periods there is a stronger flow through the Bering Strait and intensification of the northwestward currents in the central Chukchi Sea. Extensive correlation analysis shows that the thermal state of the Chukchi Sea is strongly controlled by the flow of Pacific water through the Bering Strait and by an increase of the global atmospheric temperature. In addition, the typical circulation during the "warm" "warm" and "cold" periods was reconstructed using four dimensional variational (4Dvar) data assimilation into the ocean model, and estimates of volume and heat fluxes in the Chukchi Sea during "cold" and "warm" "warm" periods were derived which are consistent with EOF and correlation analyses.

  9. Thermal regimes in the Chukchi Sea from 1941 to 2008

    NASA Astrophysics Data System (ADS)

    Luchin, Vladimir; Panteleev, Gleb

    2014-11-01

    The summer (June-October) temperature observations in the surface (0 m) and subsurface (20 m-bottom) Chukchi Sea layers collected from 1941 to 2008 have been analyzed using the self-consistent data recovery procedure based on correlation analysis and iterative empirical orthogonal function (EOF) decomposition. The analysis of the surface and subsurface EOFs identified "cold", "normal", and "warm" thermal states with variability of 2-3 years, and also 4-7 years. We found that the Chukchi Sea water temperature has gradually increased since 1941. Warming in the surface layer since 1941 has been minimal in the Bering Strait (0.012 °C yr-1, total 0.8 °C) and maximal in Long Strait (0.030-0.036 °C yr-1, total 2.0-2.4 °C). In the subsurface layer, temperatures have increased about half as much; minimal (0.0030-0.0075 °C yr-1, total 0.2-0.5 °C) in Long Strait and rather uniform (0.010-0.015 °C yr-1, total 0.7-1.0 °C) for the remaining Chukchi Sea. Analysis of the satellite sea-surface height anomaly data shows that during the "warm" periods there is a stronger flow through the Bering Strait and intensification of the northwestward currents in the central Chukchi Sea. Extensive correlation analysis shows that the thermal state of the Chukchi Sea agrees well with the flow of Pacific water through the Bering Strait and by an increase of the global atmospheric temperature. In addition, typical circulation during "warm" and "cold" periods was reconstructed using four-dimensional variational (4Dvar) data assimilation into the ocean model, and estimates of volume and heat fluxes in the Chukchi Sea during "cold" and "warm" periods were derived which are consistent with EOF and correlation analyses.

  10. Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

    USGS Publications Warehouse

    Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

    2004-01-01

    Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of <0.56 between VS and T and of <0.47 between QS and T at any depth. Such low correlation coefficients can partially be attributed to modelling arrefacts; however, they also suggest that not all of the VS and QS anomalies in the continental upper mantle can be explained by T variations. Global maps show that, by the sign of the anomaly, VS and QS usually inversely correlate with lithospheric temperatures: most cratonic regions show high VS and QS and low T, while most active regions have seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in

  11. A Thermal Evolution Model of the Earth Including the Biosphere, Continental Growth and Mantle Hydration

    NASA Astrophysics Data System (ADS)

    Höning, D.; Spohn, T.

    2014-12-01

    By harvesting solar energy and converting it to chemical energy, photosynthetic life plays an important role in the energy budget of Earth [2]. This leads to alterations of chemical reservoirs eventually affecting the Earth's interior [4]. It further has been speculated [3] that the formation of continents may be a consequence of the evolution life. A steady state model [1] suggests that the Earth without its biosphere would evolve to a steady state with a smaller continent coverage and a dryer mantle than is observed today. We present a model including (i) parameterized thermal evolution, (ii) continental growth and destruction, and (iii) mantle water regassing and outgassing. The biosphere enhances the production rate of sediments which eventually are subducted. These sediments are assumed to (i) carry water to depth bound in stable mineral phases and (ii) have the potential to suppress shallow dewatering of the underlying sediments and crust due to their low permeability. We run a Monte Carlo simulation for various initial conditions and treat all those parameter combinations as success which result in the fraction of continental crust coverage observed for present day Earth. Finally, we simulate the evolution of an abiotic Earth using the same set of parameters but a reduced rate of continental weathering and erosion. Our results suggest that the origin and evolution of life could have stabilized the large continental surface area of the Earth and its wet mantle, leading to the relatively low mantle viscosity we observe at present. Without photosynthetic life on our planet, the Earth would be geodynamical less active due to a dryer mantle, and would have a smaller fraction of continental coverage than observed today. References[1] Höning, D., Hansen-Goos, H., Airo, A., Spohn, T., 2014. Biotic vs. abiotic Earth: A model for mantle hydration and continental coverage. Planetary and Space Science 98, 5-13. [2] Kleidon, A., 2010. Life, hierarchy, and the

  12. Asymptotic regimes for the electrical and thermal conductivities in dense plasmas

    SciTech Connect

    Faussurier, G. Blancard, C.

    2015-04-15

    We study the asymptotic regimes for the electrical and thermal conductivities in dense plasmas obtained by combining the Chester–Thellung–Kubo–Greenwood approach and the Kramers approximation [Faussurier et al., Phys. Plasmas 21, 092706 (2014)]. Non-degenerate and degenerate situations are considered. The Wiedemann–Franz law is obtained in the degenerate case.

  13. Predicting Thermal Regimes of Stream Networks Across New England: Natural and Anthropogenic Influences

    EPA Science Inventory

    Thermal regime is a critical factor in models predicting joint effects of watershed management activities and climate change on habitat suitability for fish. We used a database of lotic temperature time series across New England (> 7000 station-year combinations) from state a...

  14. Incorporating Retention Time to Refine Models Predicting Thermal Regimes of Stream Networks Across New England

    EPA Science Inventory

    Thermal regimes are a critical factor in models predicting effects of watershed management activities on fish habitat suitability. We have assembled a database of lotic temperature time series across New England (> 7000 station-year combinations) from state and Federal data s...

  15. Network-based Prediction of Lotic Thermal Regimes Across New England

    EPA Science Inventory

    Thermal regimes are a critical factor in models predicting effects of watershed management activities on fish habitat suitability. We have assembled a database of lotic temperature time series across New England (> 7000 station-year combinations) from state and Federal data sour...

  16. Predicting thermal regimes of stream networks across the Chesapeake Bay Watershed: Natural and anthropogenic influences

    EPA Science Inventory

    Thermal regimes are a critical factor in models predicting joint effects of watershed management activities and climate change on fish habitat suitability. We have compiled a database of lotic temperature time series across the Chesapeake Bay Watershed (725 station-year combinat...

  17. CSDP: the seismology of continental thermal regimes. Final technical report, January 1, 1975-December 31, 1984

    SciTech Connect

    Aki, K.

    1985-02-01

    Research progress is reported in the development of new seismological tools to define and characterize the geometry, mechanical construction and mass transport process of a geothermal system, and their application to various geothermal systems including the Fenton Hill Hot Dry Rock System, New Mexico, Kilauea and Kilauea Iki, Hawaii, Mt. St. Helens, Washington, and Long Valley, California. (ACR)

  18. Continental Scientific Drilling Program thermal regimes: comparative site assessment geology of five magma-hydrothermal systems

    SciTech Connect

    Goff, F.; Waters, A.C.

    1980-10-01

    The geology and salient aspects of geophysics and hydrogeochemistry of five high-grade geothermal systems in the USA are reviewed. On the basis of this information, a target location is suggested for a deep (5- to 8-km) borehole that will maximize the amount of scientific information to be learned at each of the five geothermal areas.

  19. Thermal effects on mass detection sensitivity of carbon nanotube resonators in nonlinear oscillation regime

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Keun; Yang, Hyun-Ik; Kim, Chang-Wan

    2015-11-01

    A mass sensor using a nano-resonator has high detection sensitivity, and mass sensitivity is higher with smaller resonators. Therefore, carbon nanotubes (CNTs) are the ultimate materials for these applications and have been actively studied. In particular, CNT-based nanomechanical devices may experience high temperatures that lead to thermal expansion and residual stress in devices, which affects the device reliability. In this letter, to demonstrate the influence of the temperature change (i.e., thermal effect) on the mass detection sensitivity of CNT-based mass sensor, dynamic analysis is carried out for a CNT resonator with thermal effects in both linear and nonlinear oscillation regimes. Based on the continuum mechanics model, the analytical solution method with an assumed deflection eigenmode is applied to solve the nonlinear differential equation which involves the von Karman nonlinear strain-displacement relation and the additional axial force associated with thermal effects. A thermal effect on the fundamental resonance behavior and resonance frequency shift due to adsorbed mas, i.e., mass detection sensitivity, is examined in high-temperature environment. Results indicate a valid improvement of fundamental resonance frequency by using nonlinear oscillation in a thermal environment. In both linear and nonlinear oscillation regimes, the mass detection sensitivity becomes worse due to the increasing of temperature in a high-temperature environment. The thermal effect on the detection sensitivity is less effective in the nonlinear oscillation regime. It is concluded that a temperature change of a mass sensor with a CNT-based resonator can be utilized to enhance the detection sensitivity depending on the CNT length, linear/nonlinear oscillation behaviors, and the thermal environment.

  20. Influence of Diffuse and Discrete Groundwater Discharge on River Thermal Regimes in Present and Future Climates

    NASA Astrophysics Data System (ADS)

    Kurylyk, B.; MacQuarrie, K. T. B.

    2015-12-01

    Groundwater discharge alters stream and river thermal regimes due to the thermal inertia of the subsurface, but the exact nature of its influence depends on the discharge conditions. Diffuse groundwater discharge attenuates daily, weekly, and seasonal changes in surface water temperature. On the other hand, discrete groundwater discharge (e.g., a spring) creates in-stream thermal anomalies that provide temporary refuge for cold-water fish and other aquatic species. Thus, diffusive groundwater input reduces the temporal variability of surface water temperature, while discrete groundwater input enhances its spatial variability. In the present climate, thermal effects of groundwater discharge can be empirically studied by comparing thermal regimes of groundwater-dominated streams to those of runoff-dominated streams. However, there are still many challenges associated with attempting to quantify the thermal influence of groundwater discharge. These difficulties arise in part because the heat flux from groundwater upwelling is induced by a mass flux, and thus it cannot be directly compared to purely sensible heat fluxes. Also, shallow subsurface flow exhibits complex thermal signatures that are not well represented with mean annual air temperature data. Examining the thermal influence of groundwater discharge becomes even more complex when potential effects of climate change are considered. Results from previous studies utilizing empirical transfer models, analytical solutions, and numerical models of groundwater temperature dynamics have demonstrated that the nature of groundwater warming depends on the soil properties, groundwater recharge rate, and aquifer configuration. This talk will highlight challenges associated with quantifying the thermal influence of groundwater discharge and provide recommendations for future research opportunities in this field, including the potential to engineer thermal diversity in rivers via manipulation of groundwater flow paths.

  1. Modeling the spatiotemporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape

    DOE PAGESBeta

    Kumar, Jitendra; Collier, Nathan; Bisht, Gautam; Mills, Richard T.; Thornton, Peter E.; Iversen, Colleen M.; Romanovsky, Vladimir

    2016-09-27

    Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to the atmosphere under warming climate scenarios. Ice-wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. This microtopography plays a critical role in regulating the fine-scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behavior under the current as well as changing climate. Here, we present an end-to-end effort for high-resolution numerical modeling of thermal hydrology at real-world fieldmore » sites, utilizing the best available data to characterize and parameterize the models. We also develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites near Barrow, Alaska, spanning across low to transitional to high-centered polygons, representing a broad polygonal tundra landscape. A multiphase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using a high-resolution lidar digital elevation model (DEM), microtopographic features of the landscape were characterized and represented in the high-resolution model mesh. The best available soil data from field observations and literature were utilized to represent the complex heterogeneous subsurface in the numerical model. Simulation results demonstrate the ability of the developed modeling approach to capture – without recourse to model calibration – several aspects of the complex thermal regimes across the sites, and provide insights into the critical role of polygonal tundra microtopography in regulating the thermal dynamics of the carbon-rich permafrost soils. Moreover, areas of significant disagreement between model results and observations highlight the importance of field

  2. Thermal stability of coal-derived jet fuels in the autoxidative and pyrolytic regimes

    SciTech Connect

    Andresen, J.M.; Strohm, J.J.; Song, C.

    1999-07-01

    Coal-based liquids have a great potential as precursors for advanced jet fuels that meet the more stringent thermal stability requirements for the future high-Mach jet aircraft. In current commercial planes, the fuel may be exposed to temperatures up to 300 C. However, as the flight speed will be increased to high Mach numbers, the fuel is expected to experience temperatures as high as 480 C (900 F) in the future, since the jet fuel also functions as the main coolant for the different electronic and mechanical parts of the aircraft. Even though the residence time at such elevated temperatures is expected to be fairly short (matter of minutes), the jet fuels presently used have shown to form solid deposits that can lead to catastrophic malfunction of the jet aircraft. The current jet fuels are petroleum-derived and consequently rich in linear alkanes, which are highly susceptible to pyrolytic cracking resulting in coking. The thermal stability of a jet fuel in the pyrolytic regime can be greatly enhanced by utilizing liquids rich in cyclo-alkanes. This is the case for hydro-treated coal-derived liquids, where the aromatic structures have been transformed over to their corresponding cyclo-alkanes. An additional problem with jet fuels is the presence of dissolved oxygen (from air), which reacts with the fuel during the autoxidative regime (150--250 C) before the fuel and its oxygenated reaction products enter the pyrolytic regime (400--500 C). Accordingly, this study compares the thermal stability of a linear alkane (tetradecane), a cyclo-alkane (decahydronaphthalene) and a coal-derived jet-fuel as they go through the autoxidative regime into the pyrolytic regime. Differences in chemical reactivity between the linear- and cyclo-alkane have been related to the stability of the coal-derived jet-fuel.

  3. Thermal regime of the deep carbonate reservoir of the Po Plain (Italy)

    NASA Astrophysics Data System (ADS)

    Pasquale, V.; Chiozzi, P.; Verdoya, M.

    2012-04-01

    Italy is one of the most important countries in the world with regard to high-medium enthalpy geothermal resources, a large part of which is already extracted at relatively low cost. High temperatures at shallow to medium depth occur within a wide belt, several hundred kilometre long, west of the Apennines mountain chain. This belt, affected by recent lithosphere extension, includes several geothermal fields, which are largely exploited for electricity generation. Between the Alps and Apennines ranges, the deeper aquifer, occurring in carbonate rocks of the Po Plain, can host medium enthalpy fluids, which are exploited for district heating. Such a general picture of the available geothermal resources has been well established through several geophysical investigations and drillings. Nevertheless, additional studies are necessary to evaluate future developments, especially with reference to the deep carbonate aquifer of the Po Plain. In this paper, we focus on the eastern sector of the plain and try to gain a better understanding of the thermal regime by using synergically geothermal methodologies and geological information. The analysis of the temperatures recorded to about 6 km depth in hydrocarbon wells supplies basic constraints to outline the thermal regime of the sedimentary basin and to investigate the occurrence and importance of hydrothermal processes in the carbonate layer. After correction for drilling disturbance, temperatures were analysed, together with geological information, through an inversion technique based on a laterally constant thermal gradient model. The inferred thermal gradient changes with depth; it is quite low within the carbonate layer, while is larger in the overlying, practically impermeable formations. As the thermal conductivity variation does not justify such a thermal gradient difference, the vertical change can be interpreted as due to convective processes occurring in the carbonate layer, acting as thermal reservoir. The

  4. Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble

    SciTech Connect

    Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.

    2014-07-28

    As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF{sub 6} sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.

  5. Lunar thermal regime to 300 km. [in crust and upper mantle

    NASA Technical Reports Server (NTRS)

    Keihm, S. J.; Langseth, M. G.

    1977-01-01

    Coupling of the global heat flow, crustal heat source enrichment, thermal conductivity, and temperature in the crust and upper mantle of the moon is examined. A steady-state moon in which conductive heat transfer dominates is assumed. Heat-flow measurements from the Apollo 15 and 17 missions and gamma-ray mapping of thorium conducted by the Apollo 15 and 16 missions provide data for the study of the lunar thermal regime. Temperatures in the range of 1100 to 1600 K are found for the 300-km depth level. In the upper mantle, temperature gradients are in the range of 1.8 to 3.2 K/km.

  6. A fluctuating thermal regime improves long-term survival of quiescent prepupal Megachile rotundata (Hymenoptera: Megachilidae).

    PubMed

    Rinehart, Joseph P; Yocum, George D; Kemp, William P; Greenlee, Kendra J

    2013-06-01

    The alfalfa leafcutting bee Megachile rotundata (F.) is the primary pollinator for alfalfa seed production. Under standard management conditions, the alfalfa leafcutting bee develops to the diapausing prepupal stage under field conditions, after which they are cold-stored at a static temperature until the following spring, when temperatures are raised and development resumes. We have assessed the effects of a fluctuating thermal regime (FTR) during overwintering cold storage, where bees were exposed to a daily 1 h pulse of 20 degrees C, and compared viability and insect quality to bees stored under a static thermal regime. Our results demonstrate that implementing an FTR protocol dramatically increases the survival of cold-stored alfalfa leafcutting bees, effectively extending their shelf-life into the subsequent growing season. These findings could substantially ameliorate significant obstacles that restrict the more widespread use of this important pollinator, such as the biological constraints that restrict its use in early blooming crops, and yearly fluctuations in bee prices that add significant financial uncertainty to end users. This study also strengthens a growing body of evidence that indicates FTR protocols are superior to static thermal regime protocols for insect cold storage.

  7. A fluctuating thermal regime improves long-term survival of quiescent prepupal Megachile rotundata (Hymenoptera: Megachilidae).

    PubMed

    Rinehart, Joseph P; Yocum, George D; Kemp, William P; Greenlee, Kendra J

    2013-06-01

    The alfalfa leafcutting bee Megachile rotundata (F.) is the primary pollinator for alfalfa seed production. Under standard management conditions, the alfalfa leafcutting bee develops to the diapausing prepupal stage under field conditions, after which they are cold-stored at a static temperature until the following spring, when temperatures are raised and development resumes. We have assessed the effects of a fluctuating thermal regime (FTR) during overwintering cold storage, where bees were exposed to a daily 1 h pulse of 20 degrees C, and compared viability and insect quality to bees stored under a static thermal regime. Our results demonstrate that implementing an FTR protocol dramatically increases the survival of cold-stored alfalfa leafcutting bees, effectively extending their shelf-life into the subsequent growing season. These findings could substantially ameliorate significant obstacles that restrict the more widespread use of this important pollinator, such as the biological constraints that restrict its use in early blooming crops, and yearly fluctuations in bee prices that add significant financial uncertainty to end users. This study also strengthens a growing body of evidence that indicates FTR protocols are superior to static thermal regime protocols for insect cold storage. PMID:23865170

  8. Thermal transport in Si and Ge nanostructures in the `confinement' regime

    NASA Astrophysics Data System (ADS)

    Kwon, Soonshin; Wingert, Matthew C.; Zheng, Jianlin; Xiang, Jie; Chen, Renkun

    2016-07-01

    Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales.

  9. Thermal transport in Si and Ge nanostructures in the 'confinement' regime.

    PubMed

    Kwon, Soonshin; Wingert, Matthew C; Zheng, Jianlin; Xiang, Jie; Chen, Renkun

    2016-07-21

    Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales. PMID:27344991

  10. Thermal transport in Si and Ge nanostructures in the 'confinement' regime.

    PubMed

    Kwon, Soonshin; Wingert, Matthew C; Zheng, Jianlin; Xiang, Jie; Chen, Renkun

    2016-07-21

    Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales.

  11. Geophysical study of the structure and processes of the continental convergence zones: Alpine-Himalayan belt

    NASA Technical Reports Server (NTRS)

    Toksoz, M. N.; Molnar, P.

    1983-01-01

    Studies of the structure of the continental collision zones using seismic and body waves, theoretical modelling of the thermal regime of the convergence processes, and studies of earthquake mechanisms and deformation aspects of the model are covered.

  12. Computational Modeling of Radiative, Thermal, and Kinetic Regimes of Flame Spread

    NASA Astrophysics Data System (ADS)

    Simsek, Aslihan

    The purpose of this thesis presented is to analyze flame spread over thermally thin solid fuels in three regimes of flame spread process; radiative, thermal, and kinetic regimes. The analyses have been performed using a comprehensive two dimensional computational fluid dynamics (CFD) model written in Fortran language developed by Bhattacharjee. Flame spread over thermally thin fuels in quiescent and opposing flow microgravity environments is investigated. An extinction study is performed with different computational domain sizes for a set of fuel thicknesses to understand the effect of domain size on the extinction velocities in the radiative and kinetic regimes. The effect of development length boundary layer is studied in both radiative and kinetic regimes. It is found that flame spread rate, flame size, flame temperature, blow-off and radiative extinction velocities depend on the development length and the boundary layer created by the opposing flow. A correlation between the extinction development length and opposed flow velocity is established. Flame spread over open cell phenolic foam is investigated in detail in a quiescent microgravity environment. The critical fuel thickness is found at different oxygen concentrations and compared to those for PMMA. Pressure, oxygen concentration, and radiation studies are also performed to analyze the flame spread over foam. To understand the effect of radiation on flame spread, the CFD model is coupled with two different radiation models in a microgravity environment. The first radiation model includes gas to surface conduction, gas to environment radiation loss, gas to surface feedback radiation, and surface to environment radiation loss. The second model only excludes gas to surface radiation feedback. The results obtained using these two models are compared with the CFD results; one with radiation completely neglected, and one with only gas to surface radiation feedback neglected. Flame spread in downward

  13. Wave theories of non-laminar charged particle beams: from quantum to thermal regime

    NASA Astrophysics Data System (ADS)

    Fedele, Renato; Tanjia, Fatema; Jovanović, Dusan; de Nicola, Sergio; Ronsivalle, Concetta; Ronsivalle

    2014-04-01

    The standard classical description of non-laminar charged particle beams in paraxial approximation is extended to the context of two wave theories. The first theory that we discuss (Fedele R. and Shukla, P. K. 1992 Phys. Rev. A 45, 4045. Tanjia, F. et al. 2011 Proceedings of the 38th EPS Conference on Plasma Physics, Vol. 35G. Strasbourg, France: European Physical Society) is based on the Thermal Wave Model (TWM) (Fedele, R. and Miele, G. 1991 Nuovo Cim. D 13, 1527.) that interprets the paraxial thermal spreading of beam particles as the analog of quantum diffraction. The other theory is based on a recently developed model (Fedele, R. et al. 2012a Phys. Plasmas 19, 102106; Fedele, R. et al. 2012b AIP Conf. Proc. 1421, 212), hereafter called Quantum Wave Model (QWM), that takes into account the individual quantum nature of single beam particle (uncertainty principle and spin) and provides collective description of beam transport in the presence of quantum paraxial diffraction. Both in quantum and quantum-like regimes, the beam transport is governed by a 2D non-local Schrödinger equation, with self-interaction coming from the nonlinear charge- and current-densities. An envelope equation of the Ermakov-Pinney type, which includes collective effects, is derived for both TWM and QWM regimes. In TWM, such description recovers the well-known Sacherer's equation (Sacherer, F. J. 1971 IEEE Trans. Nucl. Sci. NS-18, 1105). Conversely, in the quantum regime and in Hartree's mean field approximation, one recovers the evolution equation for a single-particle spot size, i.e. for a single quantum ray spot in the transverse plane (Compton regime). We demonstrate that such quantum evolution equation contains the same information as the evolution equation for the beam spot size that describes the beam as a whole. This is done heuristically by defining the lowest QWM state accessible by a system of non-overlapping fermions. The latter are associated with temperature values that are

  14. A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

    SciTech Connect

    Hoogeboom-Pot, Kathleen M.; Hernandez-Charpak, Jorge N.; Gu, Xiaokun; Frazer, Travis D.; Anderson, Erik H.; Chao, Weilun; Falcone, Roger W.; Yang, Ronggui; Murnane, Margaret M.; Kapteyn, Henry C.; Nardi, Damiano

    2015-03-23

    Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths and energy dispersion in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier’s law for heat conduction dramatically overpredicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interaction of phonons originating from neighboring heat sources enables more efficient diffusive-like heat dissipation, even from nanoscale heat sources much smaller than the dominant phonon mean free paths. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as previously projected. In conclusion, we demonstrate a unique capability to extract differential conductivity as a function of phonon mean free path in materials, allowing the first (to our knowledge) experimental validation of predictions from the recently developed first-principles calculations.

  15. A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

    PubMed Central

    Hoogeboom-Pot, Kathleen M.; Hernandez-Charpak, Jorge N.; Gu, Xiaokun; Frazer, Travis D.; Anderson, Erik H.; Chao, Weilun; Falcone, Roger W.; Yang, Ronggui; Murnane, Margaret M.; Kapteyn, Henry C.; Nardi, Damiano

    2015-01-01

    Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths and energy dispersion in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier’s law for heat conduction dramatically overpredicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interaction of phonons originating from neighboring heat sources enables more efficient diffusive-like heat dissipation, even from nanoscale heat sources much smaller than the dominant phonon mean free paths. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as previously projected. Finally, we demonstrate a unique capability to extract differential conductivity as a function of phonon mean free path in materials, allowing the first (to our knowledge) experimental validation of predictions from the recently developed first-principles calculations. PMID:25831491

  16. A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

    DOE PAGESBeta

    Hoogeboom-Pot, Kathleen M.; Hernandez-Charpak, Jorge N.; Gu, Xiaokun; Frazer, Travis D.; Anderson, Erik H.; Chao, Weilun; Falcone, Roger W.; Yang, Ronggui; Murnane, Margaret M.; Kapteyn, Henry C.; et al

    2015-03-23

    Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths and energy dispersion in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier’s law for heat conduction dramatically overpredicts the rate ofmore » heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interaction of phonons originating from neighboring heat sources enables more efficient diffusive-like heat dissipation, even from nanoscale heat sources much smaller than the dominant phonon mean free paths. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as previously projected. In conclusion, we demonstrate a unique capability to extract differential conductivity as a function of phonon mean free path in materials, allowing the first (to our knowledge) experimental validation of predictions from the recently developed first-principles calculations.« less

  17. A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency.

    PubMed

    Hoogeboom-Pot, Kathleen M; Hernandez-Charpak, Jorge N; Gu, Xiaokun; Frazer, Travis D; Anderson, Erik H; Chao, Weilun; Falcone, Roger W; Yang, Ronggui; Murnane, Margaret M; Kapteyn, Henry C; Nardi, Damiano

    2015-04-21

    Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths and energy dispersion in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier's law for heat conduction dramatically overpredicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interaction of phonons originating from neighboring heat sources enables more efficient diffusive-like heat dissipation, even from nanoscale heat sources much smaller than the dominant phonon mean free paths. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as previously projected. Finally, we demonstrate a unique capability to extract differential conductivity as a function of phonon mean free path in materials, allowing the first (to our knowledge) experimental validation of predictions from the recently developed first-principles calculations. PMID:25831491

  18. Mountain frozen grounds as small amplitude thermal proxy in southern continental Patagonia

    NASA Astrophysics Data System (ADS)

    Ruiz, Sebastian; Beriain, Eneko; Izagirre, Eñaut; Bockheim, James; Pedro, Cid-Agüero

    2015-04-01

    Frozen grounds are an important element of the cryosphere, covering between a 20-25% of the global area. Frozen grounds are becoming a relevant object of research in the southern hemisphere, being most studies focused mainly on Antarctica. With the exception of seasonally frozen grounds, perennially frozen ground is found in continental South America, for example, in high altitude terrains from 4.600m a.s.l. in central Chile. However, scarce or not information regarding permafrost on Southern Patagonia has been reported. One of the aims of this study was to establish mountain permafrost existence at 1.200m in the southern limit of the Southern Patagonian Ice-Field, a geographically active area surrounded by different kinds of glaciers on fast retreat. The area of study presents several features of past cryogenic activity such as undefined polygonal grounds with a thick clast border and sandy-loam interior. A scarce vegetal cover is limited to lichen and moss communities. The analyzed soil does not represent a thermal barrier that may avoid heat wave dynamic along the ground profile. There was neither significant snow-cover during winter nor a vegetation layer enough to consider as insulation for the analyzed ground. Oscillations above 0°C were evidenced down to 1.8m depth during winter of 2014, ruling out the existence of permafrost at that lower limit. Year round thermal dynamic down to 1.8m in the ground profile is presented as one result of the monitoring. Small amplitude temperature fluctuations were registered upon monitoring. These minimal amplitudes were stable throughout several months and as such serve as an interesting proxy for recent and long-term climatic thermal fluctuation. The influence of winds coming from nearby glaciers highly affects near-surface amplitude. This interaction was studied. The present work is part of an ongoing monitoring network along South America that intends to fill the gap between tropical Andes and the Antarctic Peninsula.

  19. Impact of various surface covers on water and thermal regime of Technosol

    NASA Astrophysics Data System (ADS)

    Kodešová, Radka; Fér, Miroslav; Klement, Aleš; Nikodem, Antonín; Teplá, Daniela; Neuberger, Pavel; Bureš, Petr

    2014-11-01

    Different soil covers influence water and thermal regimes in soils within urban areas. Knowledge of these regimes is needed, particularly when assessing effectiveness of energy gathering from soils using horizontal ground heat exchangers. The goal of this study was to calibrate the model HYDRUS-1D for simulating coupled water and thermal regime in Technosol type soils with grass cover, and to use this model for predicting water and thermal regimes under different materials covering the soil surface. For this purpose soil water contents were measured at depths of 10, 20, 30, 40, 60 and 100 cm at 4 locations and temperatures were measured at depths of 20, 40, 80, 120, 150 and 180 cm at three locations (all covered by grass) from June 2011 to December 2012. In addition sensors for simultaneous measuring soil water contents and temperatures were installed under different soil covers (grass, bark chips, sand, basalt gravel and concrete paving) at a depth of 7. The parameters of soil hydraulic properties were obtained on the 100-cm3 undisturbed soil samples using the multi-step outflow experiment and numerical inversion of the measured transient flow data using HYDRUS-1D. HYDRUS-1D was then used to simulated the water regime within the soil profile under the grass cover using climatic data from June 2011 to December 2012 and some of the soil hydraulic parameters were additionally numerically optimized using soil water contents measured at all depths. Water flow and heat transport were then simulated using these parameters, measured thermal properties and temperatures measured close to the surface applied as a top boundary condition. Simulated temperatures at all depths successfully approximated the measured data. Next, water and thermal regimes under another 4 different surface covers were simulated. Soil hydraulic properties of different materials were partly measured and partly optimized when simulating soil water regime from June 2011 to December 2012 using the soil

  20. Thermal and mechanical properties of selected 3D printed thermoplastics in the cryogenic temperature regime

    NASA Astrophysics Data System (ADS)

    Weiss, K.-P.; Bagrets, N.; Lange, C.; Goldacker, W.; Wohlgemuth, J.

    2015-12-01

    Insulating materials for use in cryogenic boundary conditions are still limited to a proved selection as Polyamid, Glasfiber reinforced resins, PEEK, Vespel etc. These materials are usually formed to parts by mechanical machining or sometimes by cast methods. Shaping complex geometries in one piece is limited. Innovative 3D printing is now an upcoming revolutionary technology to construct functional parts from a couple of thermoplastic materials as ABS, Nylon and others which possess quite good mechanical stability and allow realizing very complex shapes with very subtle details. Even a wide range of material mixtures is an option and thermal treatments can be used to finish the material structure for higher performance. The use of such materials in cryogenic environment is very attractive but so far poor experience exists. In this paper, first investigations of the thermal conductivity, expansion and mechanical strength are presented for a few selected commercial 3D material samples to evaluate their application prospects in the cryogenic temperature regime.

  1. Thermal origin of continental red beds in SE China: An experiment study

    NASA Astrophysics Data System (ADS)

    Jiang, Lianting; Chen, Guoneng; Grapes, Rodney; Peng, Zhuolun

    2015-04-01

    The origin of continental red beds in SE China is the result of high diagenetic temperatures, rather than an arid climate during their deposition. Here we present results from an experimental study where black mud was heated to demonstrate the formation of red beds. Diffuse reflectance spectroscopy (DRS) of heated samples enables determination of the relative proportion of goethite and hematite. Iron in black mud is predominantly in the form of goethite that has an initial dehydration temperature of ca.150 °C. Increasing temperature or prolonged heating time is accompanied by decreasing goethite and organic content, increasing hematite and red colouration. Heat provided to subsiding red bed basins is supplied by cooling of an intracrustal granitic magma layer. The thermal model can explain vertical colour, temperature, redox and mineral zonation in red bed sequences, from red (hematite-bearing), through green-yellow (Cu, Zn, V sulphide mineralization) to grey-black (hydrocarbon, halite-bearing) sediments. The model can also be used to help prospect for hydrocarbon and halite deposits in the SE China red bed basins.

  2. The thermal regime beneath cultural blocky materials: Ground temperature measurements in and around the Scythian Kurgans of the Russian Altay Mountains.

    NASA Astrophysics Data System (ADS)

    van de Kerchove, Ruben; Goossens, Rudi

    2010-05-01

    During historical times, the Altay Mountains were repeatedly occupied by several, mainly nomadic, cultures. Among them were the Scythians who lived in the area (and far beyond), from the 8th until the 2nd century BC. This culture is widely known for their specific burial rituals, including the burying of their death in a kurgan: a burial mound consisting of a coarse debris surface layer, overlaying a burial chamber. Due to this composition, together with the continental alpine climate of the Altay Mountains, several of these graves were found frozen, thanks to the existence of ice lenses and permafrost beneath the structures. If frozen, these kurgans contained well preserved bodies, often with the tattoos on their skin intact. As nowadays a distinct temperature rising is showed in these continental mountain ranges, the hundreds of kurgans, and especially these ones located at the lower fringe of the permafrost area, are likely to defrost within decades. As a result, the valuable, frozen, organic and inorganic content will get lost, resulting in a loss of extremely valuable cultural heritage and knowledge. Therefore, extensive permafrost research regarding the thermal state of the frozen tombs and the spatial distribution of the mountain permafrost is necessary to forecast which of the tombs are endangered by thawing. In the framework of this project a first expedition was organized in the Russian Altay Mountains during the summer of 2008. During this expedition, the valleys of Dzhazator, Tarkhata, Kalanegir and Ulandryk were visited in succession and temperature installments were made in order to give an overview of the thermal regime in the area. Beside installments intended for regional modelling, special sensors were placed in order to focus on the specific thermal regime related to the Scythian kurgans. This poster gives the first results of the temperature data as recorded by sensors located in and around the burial mounds. At first attention is given to the

  3. Monitoring Drought at Continental Scales Using Thermal Remote Sensing of Evapotranspiration (Invited)

    NASA Astrophysics Data System (ADS)

    Anderson, M. C.; Hain, C.; Mecikalski, J. R.; Kustas, W. P.

    2009-12-01

    assessing standard meteorologically-based drought indicators, and may be more robust in regions with limited monitoring networks. In this study, monthly maps of ESI anomalies for 2000-2008 are compared to standard drought indices and to drought classifications in the U.S. Drought Monitor. The ESI shows better skill in ranking drought severity than do precipitation-based indices composited over comparable time intervals. The thermal remote sensing inputs to ALEXI detect drought conditions even under the dense forest cover along the East Coast of the United States, where microwave soil moisture retrievals typically lose sensitivity. On the other hand, microwave observations are not constrained by cloud cover and provide better temporal continuity, but typically at significantly lower spatial resolution. A merged TIR-microwave moisture anomaly product may have potential for optimizing both spatial and temporal coverage in continental-scale drought monitoring.

  4. Descriptors of natural thermal regimes in streams and their responsiveness to change in the Pacific Northwest of North America

    USGS Publications Warehouse

    Arismendi, Ivan; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy

    2013-01-01

    1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year. 2. To more completely describe thermal regimes, we developed several descriptors of magnitude, variability, frequency, duration and timing of thermal events throughout a year. We evaluated how these descriptors change over time using long-term (1979–2009), continuous temperature data from five relatively undisturbed cold-water streams in western Oregon, U.S.A. In addition to trends for each descriptor, we evaluated similarities among them, as well as patterns of spatial coherence, and temporal synchrony. 3. Using different groups of descriptors, we were able to more fully capture distinct aspects of the full range of variability in thermal regimes across space and time. A subset of descriptors showed both higher coherence and synchrony and, thus, an appropriate level of responsiveness to examine evidence of regional climatic influences on thermal regimes. Most notably, daily minimum values during winter–spring were the most responsive descriptors to potential climatic influences. 4. Overall, thermal regimes in streams we studied showed high frequency and low variability of cold temperatures during the cold-water period in winter and spring, and high frequency and high variability of warm temperatures during the warm-water period in summer and autumn. The cold and warm periods differed in the distribution of events with a higher frequency and longer duration of warm events in summer than cold events in winter. The cold period exhibited lower variability in the duration of events, but showed more variability in timing. 5. In conclusion, our results highlight the importance of a year-round perspective in identifying the most responsive

  5. Thermal and water regime of green roof segments filled with Technosol

    NASA Astrophysics Data System (ADS)

    Jelínková, Vladimíra; Šácha, Jan; Dohnal, Michal; Skala, Vojtěch

    2016-04-01

    Artificial soil systems and structures comprise appreciable part of the urban areas and are considered to be perspective for number of reasons. One of the most important lies in contribution of green roofs and facades to the heat island effect mitigation, air quality improvement, storm water reduction, etc. The aim of the presented study is to evaluate thermal and water regime of the anthropogenic soil systems during the first months of the construction life cycle. Green roof test segments filled with two different anthropogenic soils were built to investigate the benefits of such systems in the temperate climate. Temperature and water balance measurements complemented with meteorological observations and knowledge of physical properties of the soil substrates provided basis for detailed analysis of thermal and hydrological regime. Water balance of green roof segments was calculated for available vegetation seasons and individual rainfall events. On the basis of an analysis of individual rainfall events rainfall-runoff dependency was found for green roof segments. The difference between measured actual evapotranspiration and calculated potential evapotranspiration was discussed on period with contrasting conditions in terms of the moisture stress. Thermal characteristics of soil substrates resulted in highly contrasting diurnal variation of soils temperatures. Green roof systems under study were able to reduce heat load of the roof construction when comparing with a concrete roof construction. Similarly, received rainfall was significantly reduced. The extent of the rainfall reduction mainly depends on soil, vegetation status and experienced weather patterns. The research was realized as a part of the University Centre for Energy Efficient Buildings supported by the EU and with financial support from the Czech Science Foundation under project number 14-10455P.

  6. Influence of the seasonal snow cover on the ground thermal regime: An overview

    NASA Astrophysics Data System (ADS)

    Zhang, Tingjun

    2005-12-01

    The presence of seasonal snow cover during the cold season of the annual air temperature cycle has significant influence on the ground thermal regime in cold regions. Snow has high albedo and emissivity that cool the snow surface, high absorptivity that tends to warm the snow surface, low thermal conductivity so that a snow layer acts as an insulator, and high latent heat due to snowmelt that is a heat sink. The overall impact of snow cover on the ground thermal regime depends on the timing, duration, accumulation, and melting processes of seasonal snow cover; density, structure, and thickness of seasonal snow cover; and interactions of snow cover with micrometeorological conditions, local microrelief, vegetation, and the geographical locations. Over different timescales either the cooling or warming impact of seasonal snow cover may dominate. In the continuous permafrost regions, impact of seasonal snow cover can result in an increase of the mean annual ground and permafrost surface temperature by several degrees, whereas in discontinuous and sporadic permafrost regions the absence of seasonal snow cover may be a key factor for permafrost development. In seasonally frozen ground regions, snow cover can substantially reduce the seasonal freezing depth. However, the influence of seasonal snow cover on seasonally frozen ground has received relatively little attention, and further study is needed. Ground surface temperatures, reconstructed from deep borehole temperature gradients, have increased by up to 4°C in the past centuries and have been widely used as evidence of paleoclimate change. However, changes in air temperature alone cannot account for the changes in ground temperatures. Changes in seasonal snow conditions might have significantly contributed to the ground surface temperature increase. The influence of seasonal snow cover on soil temperature, soil freezing and thawing processes, and permafrost has considerable impact on carbon exchange between the

  7. Paleoclimatic evolution of the Galician continental shelf (NW of Spain) during the last 3000 years: from a storm regime to present conditions

    NASA Astrophysics Data System (ADS)

    González-Álvarez, R.; Bernárdez, P.; Pena, L. D.; Francés, G.; Prego, R.; Diz, P.; Vilas, F.

    2005-02-01

    A multiproxy study of the sedimentary record carried out on gravity core CGPL00-1 retrieved from the outer Galician continental shelf (NW of Spain) has allowed us to establish the main climate fluctuations affecting the region during the Upper Holocene. Grain size, TOC, C/N ratio, biogenic opal and planktonic foraminifera are the main analysed parameters. Lithology and grain size distribution lead to identify two sedimentary sequences: a lower half mainly composed by glauconitic sand and a muddy upper half. A chronology has been established based on three AMS radiocarbon ages, 907 cal. BC, 898 cal. BC and 1399 AD, and the aforementioned sedimentary sequences. The obtained radiocarbon ages are the first dated sediment samples for the Galician continental shelf. Geochemical markers show different trends in both sequences: low and/or fluctuating values in the sandy sequence and high and relatively constant values in the upper muddy sequence. The whole sandy interval is interpreted to be a nearly instantaneous deposit from a distal storm ebb current. The muddy interval was deposited in a stable and low-energy marine environment, similar to that found on the present outer shelf. The shift from a storm-dominated shelf to a low-energy environment took place synchronous with the Subboreal/Subatlantic transition, when an increase in storminess appears related to climatic instability. Transitional planktonic foraminiferal assemblage dominates the whole record, although a change to more abundant cold water species at 1420 AD, may relate to an intense upwelling pulse, probably reinforced by colder atmospheric temperatures during the Little Ice Age (LIA). Despite the presence of an upwelling regime since 1420 AD, lesser amount of opal has accumulated in the outer shelf due to enhanced offshore transport and stronger remineralization.

  8. An Analytic Parameterized Thermal Convection Model Predicting Multiple Convective Regimes and Transition Behavior

    NASA Astrophysics Data System (ADS)

    Crowley, J. W.; O'Connell, R. J.; Höink, T.

    2010-12-01

    Plates and mantle convection experience resistance to motion due to deformation associated with subduction. Parameterized models for thermal convection have attempted to incorporate this through the addition of a plate bending dissipation term in the energy balance (e.g. Conrad and Hager [1999, 2001]). However, these models assume that the plate velocity is approximately equal to the mantle flow velocity. This assumption loses validity for non-isoviscous convection. It leads to unreasonably high dissipation rates for plate bending in cases of strongly temperature dependent viscosity in which a sluggish or stagnant lid exists above a rapidly convecting mantle. We present an analytic parameterized model for thermal convection with a finite-strength plate and depth-dependent viscosity. The model allows for a convective flow in which the plate velocity can become small compared to mantle flow velocities. Our model predicts the plate velocity, plate thickness and heat flow, as well as the laterally averaged horizontal flow profile for a convective cell. The model reproduces the classic scaling laws when the plate is weak and the mantle isoviscous. The presence of an asthenosphere in our model allows for the asthenospheric flow channelization observed by Höink and Lenardic [2010]. Furthermore, our model is able to reproduce the plate velocity and flow profiles from their 2D and 3D numerical convection simulations. We find that the introduction of a strong plate has a significant impact on the behavior of the system. Solutions predicted by our model span several convective regimes: the mobile-lid, sluggish-lid and near stagnant-lid regimes. For some model parameters (mantle temperature, viscosities, material properties, etc) multiple solutions can occur. The existence of multiple solutions suggests that the system can move between states and/or that the convective state of the system is history dependent. Preliminary comparisons with 3D spherical numerical simulations

  9. Regional Heat Flow Map and the Continental Thermal Isostasy Understanding of México

    NASA Astrophysics Data System (ADS)

    Espinoza-Ojeda, O. M.; Harris, R. N.

    2014-12-01

    The first heat flow values made in Mexico were reported by Von Herzen [Science, 1963] for the marine environment and Smith [EPSL, 1974] for the continent. Since that time the number of measurements has increased greatly but are mostly from oil and gas exploration and in and around geothermal areas. We have compiled published values of conductive heat flow for Mexico and the Gulf of California to generate a new regional heat flow map consisting of 261 values. In addition to those original values, published heat flow sources include, Lee and Henyey [JGR, 1975], Lawver and Williams [JGR, 1979] Smith et al. [JGR, 1979], Lachenbruch et al. [JGR, 1985], and Ziagos et al. [JGR, 1985]. Although the geographic distribution is uneven, heat flow data are present in each of the eight main tectonic provinces. Our new compilation indicates relatively high regional heat flow averages in the Gulf Extensional Province (n=114, 92±22 mW/m2) and Mexican Basin and Range (n=21, 82±20 mW/m2) and are consistent with geologic estimates of extension. Lower regional averages are found in the Baja California Microplate (n=91, 75±19 mW/m2), the Sierra Madre Occidental (n=9, 75±12 mW/m2), the Sierra Madre Oriental (n=4, 68±15 mW/m2) and Mesa Central (n=X 77±23 mW/m2). In contrast low and variable heat flow value characterize the forearc region of the Middle America Trench (n=6, 35±16 mW/m2). A higher mean heat flow is associated with the Trans-Mexican Volcanic Belt (n=6, 78±26 mW/m2). Continental elevation results from a combination of buoyancy (i.e. compositional and thermal) and geodynamic forces. We combine these regional heat flow values with estimates of crustal thickness and density for each tectonic province and compute the thermal and compositional buoyancy following the approach of Hasterok and Chapman [JGR, 2007a,b]. We find that within uncertainties most provinces lie near the theoretical isostatic relationship with the exception of the Mesa Central and Sierra Madre del Sur

  10. Thermal and dynamical regimes of single- and two-phase magmatic flow in dikes

    NASA Technical Reports Server (NTRS)

    Carrigan, Charles R.; Schubert, Gerald; Eichelberger, John C.

    1992-01-01

    The coupling between thermal and dynamical regimes of single- and two-phase magmatic flow in dikes, due to temperature-dependent viscosity and dissipation, was investigated using finite element calculations of magma flow in dikelike channels with length-to-width ratios of 1000:1 or more. Solutions of the steady state equations governing magma flow are obtained for a variety of conditions ranging from idealized plane-parallel models to cases involving nonparallel geometry and two-phase flows. The implications of the numerical simulations for the dynamics of flow in a dike-reservoir system and the consequences of dike entrance conditions on magmatic storage are discussed. Consideration is also given to an unmixing/self-lubrication mechanism which may be important for the lubrication of silicic magmas rising to the earth's surface in mixed magma ascent scenarios, which naturally segregates magma mixtures of two components with differing viscosities to minimize the driving pressure gradient.

  11. The influence of thermal regime on gasoline direct injection engine performance and emissions

    NASA Astrophysics Data System (ADS)

    Leahu, C. I.; Tarulescu, S.

    2016-08-01

    This paper presents the experimental research regarding to the effects of a low thermal regime on fuel consumption and pollutant emissions from a gasoline direct injection (GDI) engine. During the experimental researches, the temperature of the coolant and oil used by the engine were modified 4 times (55, 65, 75 and 85 oC), monitoring the effects over the fuel consumption and emissions (CO2, CO and NOx). The variations in temperature of the coolant and oil have been achieved through AVL coolant and oil conditioning unit, integrated in the test bed. The obtained experimental results reveals the poor quality of exhaust gases and increases of fuel consumption for the gasoline direct injection engines that runs outside the optimal ranges for coolant and oil temperatures.

  12. Numerical investigation of thermal regimes in twin-tube-channel heat pipelines using conductive-convective model of heat transfer

    NASA Astrophysics Data System (ADS)

    Kuznetzov, G. V.; Polovnikov, V. Yu.

    2012-04-01

    The results of numerical investigation are reported on thermal regimes in the systems of heat transport based on the solution of the conjugative problem of conductive-convective heat transfer in the system •twin-tube-channel underground heat pipeline„ environmental medium. It is shown that the use of the proposed approach allows one to perform the comprehensive analysis of the heating regimes in such systems.

  13. Effect of tidal regime on the thermal tolerance of the marine gastropod Lunella smaragda (Gmelin 1791).

    PubMed

    Mortensen, B J D; Dunphy, B J

    2016-08-01

    The tidal cycle around New Zealand results in spring low tides consistently occurring during the hottest part of the day (mid-afternoon) in north-eastern New Zealand, and during the cooler dawn/dusk periods in the north-west of the country. We hypothesised that due to mid-afternoon spring low tides, intertidal populations residing at north-eastern sites would show greater thermotolerance than their north-west conspecifics. To test this we used the marine gastropod, Lunella smaragda, which were collected from sites on both the East and West coasts of the Auckland region and exposed to an acute heat shock. Thermotolerance was measured as survivorship (LT50), drop down time (time to heat coma) and thermal stability of the anaerobic energy producing enzyme Tauropine dehydrogenase. Furthermore, temperature loggers were deployed at each site so as to record and compare thermal regimes among sites. A strong temperature spike associated with spring low tide was found at all sites, and maximal temperatures of all East coast sites were higher than West coast sites (in some case by up to 10°C). In terms of thermotolerance, mortality of L. smaragda occurred at 42°C leading to 100% mortality at 45°C. However, comparison of LT50 showed snails were equally thermotolerant regardless of site of collection. Similar results were found in TDH thermal stability with animals from all sites showing an approximately 80% decrease in enzyme activity after 10min exposure to 42°C. Whilst drop down times were different among sites these were correlated with animal size as opposed to site of collection. Thus, East coast populations of L. smaragda appear no more thermotolerant than their West coast counterparts. Such a result is concerning as maximal temperatures at East coast sites already exceed the LT50 values of L. smaragda recorded in the lab suggesting these populations have less of a thermal safety margin.

  14. Effect of tidal regime on the thermal tolerance of the marine gastropod Lunella smaragda (Gmelin 1791).

    PubMed

    Mortensen, B J D; Dunphy, B J

    2016-08-01

    The tidal cycle around New Zealand results in spring low tides consistently occurring during the hottest part of the day (mid-afternoon) in north-eastern New Zealand, and during the cooler dawn/dusk periods in the north-west of the country. We hypothesised that due to mid-afternoon spring low tides, intertidal populations residing at north-eastern sites would show greater thermotolerance than their north-west conspecifics. To test this we used the marine gastropod, Lunella smaragda, which were collected from sites on both the East and West coasts of the Auckland region and exposed to an acute heat shock. Thermotolerance was measured as survivorship (LT50), drop down time (time to heat coma) and thermal stability of the anaerobic energy producing enzyme Tauropine dehydrogenase. Furthermore, temperature loggers were deployed at each site so as to record and compare thermal regimes among sites. A strong temperature spike associated with spring low tide was found at all sites, and maximal temperatures of all East coast sites were higher than West coast sites (in some case by up to 10°C). In terms of thermotolerance, mortality of L. smaragda occurred at 42°C leading to 100% mortality at 45°C. However, comparison of LT50 showed snails were equally thermotolerant regardless of site of collection. Similar results were found in TDH thermal stability with animals from all sites showing an approximately 80% decrease in enzyme activity after 10min exposure to 42°C. Whilst drop down times were different among sites these were correlated with animal size as opposed to site of collection. Thus, East coast populations of L. smaragda appear no more thermotolerant than their West coast counterparts. Such a result is concerning as maximal temperatures at East coast sites already exceed the LT50 values of L. smaragda recorded in the lab suggesting these populations have less of a thermal safety margin. PMID:27503732

  15. Thermal regimes, nonnative trout, and their influences on native Bull Trout in the Upper Klamath River Basin, Oregon

    USGS Publications Warehouse

    Benjamin, Joseph R.; Heltzel, Jeannie; Dunham, Jason; Heck, Michael; Banish, Nolan P.

    2016-01-01

    The occurrence of fish species may be strongly influenced by a stream’s thermal regime (magnitude, frequency, variation, and timing). For instance, magnitude and frequency provide information about sublethal temperatures, variability in temperature can affect behavioral thermoregulation and bioenergetics, and timing of thermal events may cue life history events, such as spawning and migration. We explored the relationship between thermal regimes and the occurrences of native Bull Trout Salvelinus confluentus and nonnative Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta across 87 sites in the upper Klamath River basin, Oregon. Our objectives were to associate descriptors of the thermal regime with trout occurrence, predict the probability of Bull Trout occurrence, and estimate upper thermal tolerances of the trout species. We found that each species was associated with a different suite of thermal regime descriptors. Bull Trout were present at sites that were cooler, had fewer high-temperature events, had less variability, and took longer to warm. Brook Trout were also observed at cooler sites with fewer high-temperature events, but the sites were more variable and Brook Trout occurrence was not associated with a timing descriptor. In contrast, Brown Trout were present at sites that were warmer and reached higher temperatures faster, but they were not associated with frequency or variability descriptors. Among the descriptors considered, magnitude (specifically June degree-days) was the most important in predicting the probability of Bull Trout occurrence, and model predictions were strengthened by including Brook Trout occurrence. Last, all three trout species exhibited contrasting patterns of tolerating longer exposures to lower temperatures. Tolerance limits for Bull Trout were lower than those for Brook Trout and Brown Trout, with contrasts especially evident for thermal maxima. Our results confirm the value of exploring a suite of thermal

  16. Thermal history and evolution of the South Atlantic passive continental margin in northern Namibia

    NASA Astrophysics Data System (ADS)

    Menges, Daniel; Karl, Markus; Glasmacher, Ulrich Anton

    2013-04-01

    northwestern Namibia, and their relationship to continental breakup, Journal of the Geological Society of London 152: 97-104. Renne, P.R., Ernesto, M., Pacca, I.I., G. Coe, R.S., Glen, J. M., Prévot, M., Perrin, M., 1992. The age of Paraná flood volcanism, rifting of Gondwanaland, and the Jurassic -Cretaceous boundary. Science 258, 975 - 979. Stewart, K. S., Turner, S., Kelly, S., Hawkesworth, C. J., Kirstein, L. and Mantovani, M. S. M., 1996. 3D 40Ar-39Ar geochronology in the Parańa flood basalt province, Earth and Planetary Science Letters 143: 95-110. Turner, S., Hawkesworth, C., Gallagher, K., Stewart, K., Peate, D. and Mantovani, M., 1996. Mantle plumes, flood basalts, and thermal models for melt generation beneath continents: Assessment of a conductive heating model and application to the Parana, Journal of Geophysical Research 101: 11503- 11518.

  17. Response of stream invertebrates to a global-warming thermal regime: An ecosystem-level manipulation

    SciTech Connect

    Hogg, I.D.; Williams, D.D.

    1996-03-01

    We manipulated, in accord with global-warming predictions, the thermal regime of a permanent first-order stream near Toronto, Ontario, Canada. We examined the effects of a 2-3.5{degrees}C water-temperature increase on densities, biomass, species composition, and life histories of resident stream invertebrates. The stream was divided longitudinally at the source into two channels, one control and one experimental, and a before and after (BACI) design was employed such that one pre-manipulation year was followed by 2 yr of the temperature manipulation. Changes in the experimental channel following commencement of the manipulation included: (1) decreased total animal densities, particularly Chironomidae (Diptera); (2) earlier onset of adult insect emergence; (3) increased growth rates and precocious breeding in Hyallella azteca (Amphipoda); (4) smaller size at maturity for Nemoura trispinosa (Plecoptera) and H., azteca and (5) altered sex ratios for Lepidostoma vernale (Trichoptera). These results partially corroborate previous laboratory and field studies. However, variation in the responses of individual target species to the manipulation was unexpected and may have been influenced by the genetic structure of local populations. We conclude that levels of gene flow among habitats may be critical to the degree of impact seen as a result of large-scale thermal perturbation (e.g., global warming). 60 refs., 13 figs., 1 tab.

  18. Monitoring the Thermal Regime at Hot Creek and Vicinity, Long Valley Caldera, Eastern California

    NASA Astrophysics Data System (ADS)

    Clor, L. E.; Hurwitz, S.; Howle, J.

    2015-12-01

    Hot Creek Gorge contains the most obvious surface expression of the hydrothermal system in Long Valley Caldera, California, discharging 200-300 L/s of thermal water according to USGS measurements made since 1988. Formerly, Hot Creek was a popular public swimming area, but it was closed in 2006 due to unpredictable temperature fluctuations and sporadic geysering of thermal water within the creek (Farrar et al. USGS Fact Sheet2007-3045). The USGS has monitored the thermal regime in the area since the mid-1980s, including a long-term series of studies 0.6 km away at well CH-10b. Temperature measurements in the ~100 m deep well, which have been performed on an intermittent basis since it was drilled in 1983, reveal a complex temperature profile. Temperatures increase with depth to a maximum at about 45 meters below the ground surface, and then decrease steadily to the bottom of the well. The depth of the temperature maximum in the well (~45 m) corresponds to an elevation of ~2,120 m, roughly equivalent to the elevation of Hot Creek, and appears to sample the same hydrothermal flow system that supplies thermal features at the surface in the gorge. Starting in the early 1990s, the maximum temperature in CH-10b rose from 93.4°C to its peak in 2007 at 101.0°C. A cooling trend was observed beginning in 2009 and continues to present (99.3°C in June 2015). As the input into CH-10b is at the elevation of the creek, it exhibits the potential for response to thermal events at Hot Creek, and could provide a useful tool for monitoring future hazards. On short timescales, CH-10b also responds to large global earthquakes, greater than ~M7. These responses are captured with continuously logged high-frequency data (5s), and are usually characterized by a co-seismic water level drop of up to ten centimeters. Water levels tend to recover to pre-earthquake levels within a few hours to days.

  19. The Case for a Thermal Origin of Magmatism on the North Atlantic Continental Margin

    NASA Astrophysics Data System (ADS)

    White, R.

    2008-12-01

    The cause of the magmatism on 'volcanic' continental margins is still disputed, specifically as to whether it is due to increased mantle temperatures. New normal incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the NE Atlantic enable us to constrain the seismic velocities and volumes of both the extruded and intruded melt. Near the Faroe Islands, for every 1 km along strike, 360-- 400 cubic kilometers of basalt was extruded, while 540--600 cubic kilometers was intruded into the continent- ocean transition (COT). Lower-crustal intrusions are focused mainly into a narrow zone about 50 km wide on the COT, whereas extruded basalts flow more than 100 km from the rift. Deep-penetration seismic profiles show that melt is intruded into the lower crust as sills which cross-cut the continental fabric, rather than as 'underplate' of 100 per cent melt as has previously often been assumed. This means that measured lower-crustal velocities represent a mixture of continental crust and new igneous rock. Tomographic inversion of wide-angle traveltimes from 85 ocean bottom seismometers constrain average lower-crustal seismic velocities as 6.9-7.3 km/s under the COT, intermediate between the velocities of the continental crust and fully igneous oceanic crust on either side. By comparison with theoretical curves of igneous thickness versus seismic velocity (H- Vp), our observations are consistent with the dominant control on the melt production being elevated mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or of the presence of fertile mantle at the time of continental breakup as suggested for the North Atlantic by other authors. The mantle temperature anomaly was c. 130-150°C above normal at the time of continental breakup, decreasing steadily by about 75°C over the first 10 Ma of seafloor spreading. Comparison with the conjugate Greenland margins reveal a similar

  20. Enhanced thermal radiation in terahertz and far-infrared regime by hot phonon excitation in a field effect transistor

    SciTech Connect

    Chung, Pei-Kang; Yen, Shun-Tung

    2014-11-14

    We demonstrate the hot phonon effect on thermal radiation in the terahertz and far-infrared regime. A pseudomorphic high electron mobility transistor is used for efficiently exciting hot phonons. Boosting the hot phonon population can enhance the efficiency of thermal radiation. The transistor can yield at least a radiation power of 13 μW and a power conversion efficiency higher than a resistor by more than 20%.

  1. Effects of constant and cyclical thermal regimes on growth and feeding of juvenile cutthroat trout of variable sizes

    USGS Publications Warehouse

    Meeuwig, M.H.; Dunham, J.B.; Hayes, J.P.; Vinyard, G.L.

    2004-01-01

    The effects of constant (12, 18, and 24 A?C) and cyclical (daily variation of 15a??21 and 12a??24 A?C) thermal regimes on the growth and feeding of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) of variable sizes were examined. Higher constant temperatures (i.e., 24 A?C) and more variable daily temperatures (i.e., 12a??24 A?C daily cycle) negatively affected growth rates. As fish mass increased (from 0.24 to 15.52 g) the effects of different thermal regimes on mass growth became more pronounced. Following 14 days exposure to the thermal regimes, feeding rates of individual fish were assessed during acute exposure (40 min) to test temperatures of 12, 18, and 24 A?C. Feeding rate was depressed during acute exposure to 24 A?C, but was not significantly affected by the preceding thermal regime. Our results indicate that even brief daily exposure to higher temperatures (e.g., 24 A?C) can have considerable sublethal effects on cutthroat trout, and that fish size should be considered when examining the effects of temperature.

  2. Soil thermal regime and geomorphogenesis at Fuentes Carrionas massif (Cantabrian Range, NW Iberian Peninsula).

    NASA Astrophysics Data System (ADS)

    Pellitero, Ramon; Serrano Cañadas, Enrique

    2015-04-01

    Fuentes Carrionas is a massif within the Cantabrian Range, in NW Iberian Peninsula. Its altitude ranges between 1400 and 2500 meters and its climate is an oceanic/Mediterranean transition one, with cold temperatures and heavy snowfall in the winter/early spring season, and a warm and dry summer season. Due to its outstanding altitude and lithological variety in the Cantabrian Range context, Fuentes Carrionas holds some periglacial activity (gelifluction, frost shattering) which is absent elsewhere in NW Iberian Peninsula. This work is relates the soil thermal regime across the mountain gradient to landforms formation. 14 thermometers (11 i-button, protected in a plastic can, and three UTL data loggers) were buried at a shallow depth (10 cm.) between autumn 2009 and summer 2012. 12 thermometers were placed between 1900 and 2400 m.a.s.l. at 250 meters altitude interval at the four main aspects. Two additional thermometers were place in the Curavacas N face for permafrost identification. Thermometers were calibrated to yield a measurement every 6 hours starting from 8 AM during one year's time. Data was collected annually in the summer season. Some additional soil temperature data was obtained from an external project in the same area for the 2007-2009 interval. In this case thermometers were "Hobbo" model, and they were also buried to a shallow depth. Results show a permafrost free mountain range. Annual average soil temperatures range between 1 and 8 degrees Celsius. Snow pack appears as a decisive factor in winter temperatures, as the zero curtain effect can be tracked in many cases. Snow cover patterns show a distinctive behavior between S and N aspects, with a 3 months snow cover on the southern faces and between 6 and 9 at the northern analogues. This cover has a relevant impact on geomorphological processes. There is a clear relation between spring snow melt and solifluction or channelized erosion. Also, snow cover prevents the occurrence of freeze/thaw cycles

  3. Importance of soil thermal regime in terrestrial ecosystem carbon dynamics in the circumpolar north

    NASA Astrophysics Data System (ADS)

    Jiang, Yueyang; Zhuang, Qianlai; Sitch, Stephen; O'Donnell, Jonathan A.; Kicklighter, David; Sokolov, Andrei; Melillo, Jerry

    2016-07-01

    In the circumpolar north (45-90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries. With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~ 0.4 Pg C yr- 1 lower present-day heterotrophic respiration but ~ 0.5 Pg C yr- 1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr- 1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the e nhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.

  4. Active layer thermal regime at different vegetation covers at Lions Rump, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Almeida, Ivan C. C.; Schaefer, Carlos Ernesto G. R.; Fernandes, Raphael B. A.; Pereira, Thiago T. C.; Nieuwendam, Alexandre; Pereira, Antônio Batista

    2014-11-01

    Climate change impacts the biotic and abiotic components of polar ecosystems, affecting the stability of permafrost, active layer thickness, vegetation, and soil. This paper describes the active layer thermal regimes of two adjacent shallow boreholes, under the same soil but with two different vegetations. The study is location in Lions Rump, at King George Island, Maritime Antarctic, one of the most sensitive regions to climate change, located near the climatic limit of Antarctic permafrost. Both sites are a Turbic Cambic Cryosol formed on andesitic basalt, one under moss vegetation (Andreaea gainii, at 85 m a.s.l.) and another under lichen (Usnea sp., at 86 m a.s.l.), located 10 m apart. Ground temperature at same depths (10, 30 and 80 cm), water content at 80 cm depth and air temperature were recorded hourly between March 2009 and February 2011. The two sites showed significant differences in mean annual ground temperature for all depths. The lichen site showed a higher soil temperature amplitude compared to the moss site, with ground surface (10 cm) showing the highest daily temperature in January 2011 (7.3 °C) and the lowest daily temperature in August (- 16.5 °C). The soil temperature at the lichen site closely followed the air temperature trend. The moss site showed a higher water content at the bottommost layer, consistent with the water-saturated, low landscape position. The observed thermal buffering effect under mosses is primarily associated with higher moisture onsite, but a longer duration of the snowpack (not monitored) may also have influenced the results. Active layer thickness was approximately 150 cm at low-lying moss site, and 120 cm at well-drained lichen site. This allows to classify these soils as Cryosols (WRB) or Gelisols (Soil Taxonomy), with evident turbic features.

  5. Regional warming and the thermal regimes of American crocodile nests in the Tempisque Basin, Costa Rica.

    PubMed

    Murray, Christopher M; Easter, Michael; Padilla, Sergio; Marin, Mahmood Sasa; Guyer, Craig

    2016-08-01

    Spatial variation in global climate change makes population-specific responses to this enigmatic threat pertinent on a regional scale. Organisms with temperature-dependent sex determination (TSD) potentially possess a unique physiological susceptibility that threatens population viability if rapid environmental effects on sex ratios render populations non-viable. A heavily male-biased sex ratio for hatchling American crocodiles of the Tempisque Basin, Costa Rica requires assessment of how nest temperature affects sex determination at this site, how females might compensate for these effects when creating nests, and how current patterns of climate change might alter future sex ratios and survival in hatchling cohorts. We demonstrate high within-nest variation in temperature but predict a female bias at hatching based on nest temperatures quantified here. Further, our data suggest that egg size and metabolic heating associated with this factor outweighs microhabitat parameters and depth in influencing nest thermal regimes. Finally, we document regional warming in the Tempisque Basin over the last 15 years and project that further heating over the next 15 years will not yield hatchling sex ratios as male biased as those currently found at this site. Thus, we find no support for nest temperature or climate change as likely explanations for male-biased American crocodile (Crocodylus acutus) sex ratios in the Tempisque Basin. PMID:27503716

  6. Regional warming and the thermal regimes of American crocodile nests in the Tempisque Basin, Costa Rica.

    PubMed

    Murray, Christopher M; Easter, Michael; Padilla, Sergio; Marin, Mahmood Sasa; Guyer, Craig

    2016-08-01

    Spatial variation in global climate change makes population-specific responses to this enigmatic threat pertinent on a regional scale. Organisms with temperature-dependent sex determination (TSD) potentially possess a unique physiological susceptibility that threatens population viability if rapid environmental effects on sex ratios render populations non-viable. A heavily male-biased sex ratio for hatchling American crocodiles of the Tempisque Basin, Costa Rica requires assessment of how nest temperature affects sex determination at this site, how females might compensate for these effects when creating nests, and how current patterns of climate change might alter future sex ratios and survival in hatchling cohorts. We demonstrate high within-nest variation in temperature but predict a female bias at hatching based on nest temperatures quantified here. Further, our data suggest that egg size and metabolic heating associated with this factor outweighs microhabitat parameters and depth in influencing nest thermal regimes. Finally, we document regional warming in the Tempisque Basin over the last 15 years and project that further heating over the next 15 years will not yield hatchling sex ratios as male biased as those currently found at this site. Thus, we find no support for nest temperature or climate change as likely explanations for male-biased American crocodile (Crocodylus acutus) sex ratios in the Tempisque Basin.

  7. Normal fault thermal regimes and the interpretation of low-temperature thermochronometers

    NASA Astrophysics Data System (ADS)

    Ehlers, Todd A.; Armstrong, Phillip A.; Chapman, David S.

    2001-11-01

    Exhumation rates inferred from thermochronometers are dependent on spatial and temporal variations in temperature. In active extensional mountain belts, the temperature field is complicated by tectonic and surface processes including: (1) lateral heat flow across large, range-bounding normal faults due to the juxtaposition of a cool hanging wall and a relatively warmer footwall, (2) uplift and erosion of the footwall, (3) sedimentation and burial of the hanging wall, (4) lateral heat refraction around low thermal conductivity sediments deposited in the hanging wall basin, and (5) 3D temperature variations due to high-relief topography developed on the footwall. We explore these mechanisms through a series of 2D conductive thermal models designed to investigate the effect of tectonics and topography on apatite fission track (AFT) and (U-Th)/He thermochronometer data. Models were tuned to the geometry and kinematics of the Wasatch Mountains, Utah, USA. The principal parameters in our model are exhumation and burial rates ranging from 0.2 to 5.7 mm per year at the range front and decreasing with distance from the fault, surface morphology taken from USGS digital elevation models, and basin geometries inferred from seismic and gravity surveys. Predicted AFT and (U-Th)/He ages were generated using cooling rate dependent annealing and diffusion kinetic models. Results indicate after 10 million years of exhumation, footwall (U-Th)/He and AFT closure temperature isotherms within 10 km of the fault are advected upward 500 and 1000 m, respectively, from their initial position. The upward advection of isotherms and the 2D nature of the thermal regime can result in erroneous exhumation rates calculated from plots of sample elevation versus age using 1D thermal models. For simulations with a uniform vertical uplift rate and canyon and ridge topography, 1D and 2D exhumation rate differences were 20-70% for (U-Th)/He and ˜10% for AFT data. Samples collected perpendicular to

  8. Thermal regime of active layer at two lithologically contrasting sites on James Ross Island, Antarctic Peninsula.

    NASA Astrophysics Data System (ADS)

    Hrbáček, Filip; Nývlt, Daniel; Láska, Kamil

    2016-04-01

    Antarctic Peninsula region (AP) represents one of the most rapidly warming parts of our planet in the last 50 years. Despite increasing research activities along both western and eastern sides of AP in last decades, there is still a lot of gaps in our knowledge relating to permafrost, active layer and its thermal and physical properties. This study brings new results of active layer monitoring on James Ross Island, which is the largest island in northern AP. Its northern part, Ulu Peninsula, is the largest ice-free area (more than 200 km2) in the region. Due its large area, we focused this study on sites located in different lithologies, which would affect local thermal regime of active layer. Study site (1) at Abernethy Flats area (41 m a.s.l.) lies ~7 km from northern coast. Lithologically is formed by disintegrated Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. Study site (2) is located at the northern slopes of Berry Hill (56 m a.s.l.), about 0.4 km from northern coastline. Lithology is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine grained sandstones of the Mendel Formation. Data of air temperature at 2 meters above ground and the active layer temperatures at 75 cm deep profiles were obtained from both sites in period 1 January 2012 to 31 December 2014. Small differences were found when comparing mean air temperatures and active temperatures at 5 and 75 cm depth in the period 2012-2014. While the mean air temperatures varied between -7.7 °C and -7.0 °C, the mean ground temperatures fluctuated between -6.6 °C and -6.1 °C at 5 cm and -6.9 °C and -6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes respectively. Even though ground temperature differences along the profiles weren't pronounced during thawing seasons, the maximum active layer thickness was significantly larger at Berry Hill slopes (80 to 82 cm) than at Abernethy Flats (52 to 64 cm). We assume this differences are affected by

  9. Subsurface hydro-thermal regime and the atmospheric hydroclimate by a climate model

    NASA Astrophysics Data System (ADS)

    Saito, K.

    2009-04-01

    experiments were run for 20 years, forced by the climatological sea surface temperature and sea ice concentrations derived from the 1981-2000 period, after 150-year spin-up for the subsurface regime. The last 9 years were taken for the analysis. Different complexity of the subsurface hydro-thermal physics simulated different near-surface thermal states and seasonality. The refined physics showed warmer summer and cooler winter. The difference was most apparent in high latitudes; surface air temperature increased about 2°C in summer (zonal average, only over land), and decreased by about 5°C in winter. The improved physics and the presence of the top organic layer kept more ground ice during the warmer seasons. The total amount of soil moisture (i.e. soil wetness), however, did not change by the change of the physics. This helped mitigating the unrealistically fast and large flux of heat within the ground and at the interface between the atmosphere and the land surface, and fed back to the change in the subsurface thermal regime (e.g., active layer depth, or length of ground freezing), and affected the seasonality. It also led to improvement of the cumulative temperature indices for the atmospheric forcing in the warm and cold season (e.g. Thaw and Freezing Index). . The difference in the near-surface thermal state in high latitudes also affected snow accumulation in winter,earlier and larger for the finer physics, although precipitation did not vary largely except in the lower latitudes, at the southern flank of the Tibetan Plateau, where large precipitation differences were found during the summer monsoonal period, leading to a contrast between wetter Tibetan Plateau and drier coastal China. Land-average total annual runoff did not vary greatly between integrations at all latitudes; however, its seasonal distribution showed large difference. During the melting season, high-latitude runoff was greater for the finer physics due to shallower active layer, whereas it was

  10. Nonconstant Thermal Regimes Enhance Overwintering Success and Accelerate Diapause Development for Smicronyx fulvus (Coleoptera: Curculionidae).

    PubMed

    Prasifka, Jarrad R; Rinehart, Joseph P; Yocum, George D

    2015-08-01

    Recent populations of the red sunflower seed weevil, Smicronyx fulvus LeConte (Coleoptera: Curculionidae), have been inconsistent or declining, particularly in North Dakota. Consequently, research on weevil biology, including development of resistant germplasm, has been limited. To determine whether cold storage of diapausing larvae could be improved, nonconstant temperature treatments (fluctuating thermal regime [FTR] and thermoperiod [TP]) were tested versus a constant 6°C for storage up to 365 d. Both alternate temperature treatments produced more adult weevils than constant 6°C for short (42, 91 d) storage, while all temperature treatments were good (≥60% adult emergence) at moderate term (182 d) cold storage, and FTR was best for long (365 d) periods. Excluding the 14-d storage period, which produced too few weevils for comparison, each doubling of cold storage time (e.g., from 42 to 91 d, 91 to 182 d), usually decreased the number of days to 50% relative emergence by ∼10 d. After 365 d of larval storage, emerged S. fulvus adults successfully infested sunflowers in a plant growth chamber, with damage per female similar to that observed in field trials. Compared with previous efforts to store weevil larvae, the method of collection and FTR storage is either more effective (greater adult emergence and reduced parasitism) or more time-efficient, and should permit year-round research using S. fulvus adults. Because successful emergence under FTR was >75% after 365 d, additional research would be required to determine the maximum effective duration of cold storage for S. fulvus. PMID:26470322

  11. Fluid Origins, Thermal Regimes, and Fluid and Solute Fluxes in the Forearc of Subduction Zones

    NASA Astrophysics Data System (ADS)

    Kastner, M.; Solomon, E. A.; Harris, R. N.; Torres, M. E.

    2014-12-01

    An in-depth analysis and synthesis of published and newly acquired data on the chemical and isotopic composition of forearc fluids, fluid fluxes, and the associated thermal regimes in five well-studied, representative erosional and accretionary subduction zone (SZ) forearcs will be presented. Evidence of large-scale fluid flow, primarily focused along faults, is manifested by widespread seafloor venting, associated biological communities, authigenic carbonate formation, chemical and isotopic anomalies in pore-fluid depth-profiles, and thermal anomalies. The nature of fluid venting seems to differ at the two types of SZs. At both, fluid and gas venting sites are primarily associated with faults. At accretionary SZs, the décollement and underthrust coarser-grained stratigraphic horizons are the main fluid conduits, whereas at non-accreting and erosive margins, the fluids from compaction and dehydration reactions are to a great extent partitioned between the décollement and focused conduits through the prism. The measured fluid output fluxes at seeps are high, ~15-40 times the amount that can be produced through local steady-state compaction, suggesting additional fluid sources or non-steady-state fluid flow must be involved. Recirculation of seawater must be an important component of the overall forearc output fluid flux. The most significant chemical and isotopic characteristics of the expelled fluids relative to seawater are: Cl dilution, sulfate, Ca and Mg depletions, and enrichments in Li, B, Si, Sr, alkalinity, and hydrocarbon concentrations; they often have distinctive δ18O, δD, δ7Li, δ11B, and δ37Cl values, and variable Sr isotope ratios. These characteristics provide key insights on the source of the fluid and the temperature at the source. Using our best fluid output flux estimate and considering an ocean volume of 1340 × 106 km3, the global ocean residence time in SZs is ~100 Myr. This value is five times faster than previous estimates for SZs and

  12. Modeling the spatio-temporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape: Modeling Archive

    DOE Data Explorer

    Peter E. Thornton; Jitendra Kumar; Colleen M. Iversen; Richard T. Mills; Gautam Bisht; Nathan Collier; Vladimir Romanovsky

    2016-01-27

    This Modeling Archive is in support of an NGEE Arctic discussion paper under review and available at http://www.the-cryosphere-discuss.net/tc-2016-29/. Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to atmosphere under warming climate. Ice--wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. The microtopography plays a critical role in regulating the fine scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behaviour under current as well as changing climate. We present here an end-to-end effort for high resolution numerical modeling of thermal hydrology at real-world field sites, utilizing the best available data to characterize and parameterize the models. We develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites at Barrow, Alaska spanning across low to transitional to high-centered polygon and representative of broad polygonal tundra landscape. A multi--phase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using high resolution LiDAR DEM, microtopographic features of the landscape were characterized and represented in the high resolution model mesh. Best available soil data from field observations and literature was utilized to represent the complex hetogeneous subsurface in the numerical model. This data collection provides the complete set of input files, forcing data sets and computational meshes for simulations using PFLOTRAN for four sites at Barrow Environmental Observatory. It also document the complete computational workflow for this modeling study to allow verification, reproducibility and follow up studies.

  13. Third-order correlation function and ghost imaging of chaotic thermal light in the photon counting regime

    SciTech Connect

    Zhou Yu; Simon, Jason; Liu Jianbin; Shih, Yanhua

    2010-04-15

    In a near-field three-photon correlation measurement, we observed the third-order temporal and spatial correlation functions of chaotic thermal light in the single-photon counting regime. In the study, we found that the probability of jointly detecting three randomly radiated photons from a chaotic thermal source by three individual detectors is 6 times greater if the photodetection events fall in the coherence time and coherence area of the radiation field than if they do not. From the viewpoint of quantum mechanics, the observed phenomenon is the result of three-photon interference. By making use of this property, we measured the three-photon thermal light lensless ghost image of a double spot and achieved higher visibility compared with the two-photon thermal light ghost image.

  14. Active layer thermal monitoring of a Dry Valley of the Ellsworth Mountains, Continental Antarctica

    NASA Astrophysics Data System (ADS)

    Schaefer, Carlos Ernesto; Michel, Roberto; Souza, Karoline; Senra, Eduardo; Bremer, Ulisses

    2015-04-01

    daily average in late December 2012, reaching a minimum in mid July 2013 on P1 (10.9 °C, -37.9 °C, ± 11.1) and P2 (6.9 °C, -37.1 °C, ± 10.2). The active layer thickness reaches a maximum of 48.4 cm at P1 on January 17th 2013 and 47.8 cm at P2 on January 7th 2012. No ID were recorded for the studied period, one TD was recorded at 5 cm on P2, 143 FTD were recorded at 5 cm, 81 at 10 cm and 46 days at 30 cm on P1, on P2 118 FTD were recorded at 5 cm, 80 at 10 cm and 42 days at 30 cm. The majority of the days were classified as FD for both sites; 585 at 5 cm, 647 at 10 cm and 684 days at 30 cm on P1, on P2 611 FD were recorded at 5 cm, 650 at 10 cm and 688 days at 30 cm. Only 17 FTD were recorded for the air temperature and 713 FD. Over the 728 days of the studied period the sum of all positive daily average temperatures was 166.3 TDD at 5 cm and 23.8 TDD at 10 cm on P1, 45.0 TDD at 5 cm and 5.2 TDD at 10 cm on P2. No positive daily average was recorded at 30 cm for both sites. The sum of all negative daily average temperatures was -13504.5 FDD at 5 cm, -13389.9 FDD at 10 cm and -13381.0 FDD at 30 cm on P1, -13508.0 FDD at 5 cm, -13486.6 FDD at 10 cm and -13398.9 FDD at 30 cm on P2. Only 0.28 TDD were summed for the air temperature and -14430.7 FDD. The soil thermal regime at the dry valley of Edson Hill, Ellsworth Mountains is characteristic of polar desert affected by Dry-frozen permafrost. Although air temperature does not reach high positive values, variations in soil temperature are more intense during the year, showing the soil's response to solar radiation.

  15. Adaptation to local thermal regimes by crustose coralline algae does not affect rates of recruitment in coral larvae

    NASA Astrophysics Data System (ADS)

    Siboni, Nachshon; Abrego, David; Evenhuis, Christian; Logan, Murray; Motti, Cherie A.

    2015-12-01

    Crustose coralline algae (CCA) are well known for their ability to induce settlement in coral larvae. While their wide distribution spans reefs that differ substantially in temperature regimes, the extent of local adaptation to these regimes and the impact they have on CCA inductive ability are unknown. CCA Porolithon onkodes from Heron (southern) and Lizard (northern) islands on Australia's Great Barrier Reef (separated by 1181 km) were experimentally exposed to acute or prolonged thermal stress events and their thermal tolerance and recruitment capacity determined. A sudden onset bleaching model was developed to determine the health status of CCA based on the rate of change in the CCA live surface area (LSA). The interaction between location and temperature was significant ( F (2,119) = 6.74, p = 0.0017), indicating that thermally driven local adaptation had occurred. The southern population remained healthy after prolonged exposure to 28 °C and exhibited growth compared to the northern population ( p = 0.022), with its optimum temperature determined to be slightly below 28 °C. As expected, at the higher temperatures (30 and 32 °C) the Lizard Island population performed better that those from Heron Island, with an optimum temperature of 30 °C. Lizard Island CCA displayed the lowest bleaching rates at 30 °C, while levels consistently increased with temperature in their southern counterparts. The ability of those CCA deemed thermally tolerant (based on LSA) to induce Acropora millepora larval settlement was then assessed. While spatial differences influenced the health and bleaching levels of P. onkodes during prolonged and acute thermal exposure, thermally tolerant fragments, regardless of location, induced similar rates of coral larval settlement. This confirmed that recent thermal history does not influence the ability of CCA to induce settlement of A. millepora larvae.

  16. Caldera processes and magma-hydrothermal systems continental scientific drilling program: thermal regimes, Valles caldera research, scientific and management plan

    SciTech Connect

    Goff, F.; Nielson, D.L.

    1986-05-01

    Long-range core-drilling operations and initial scientific investigations are described for four sites in the Valles caldera, New Mexico. The plan concentrates on the period 1986 to 1993 and has six primary objectives: (1) study the origin, evolution, physical/chemical dynamics of the vapor-dominated portion of the Valles geothermal system; (2) investigate the characteristics of caldera fill and mechanisms of caldera collapse and resurgence; (3) determine the physical/chemical conditions in the heat transfer zone between crystallizing plutons and the hydrothermal system; (4) study the mechanism of ore deposition in the caldera environment; (5) develop and test high-temperature drilling techniques and logging tools; and (6) evaluate the geothermal resource within a large silicic caldera. Core holes VC-2a (500 m) and VC-2b (2000 m) are planned in the Sulphur Springs area; these core holes will probe the vapor-dominated zone, the underlying hot-water-dominated zone, the boiling interface and probable ore deposition between the two zones, and the deep structure and stratigraphy along the western part of the Valles caldera fracture zone and resurgent dome. Core hole VC-3 will involve reopening existing well Baca number12 and deepening it from 3.2 km (present total depth) to 5.5 km, this core hole will penetrate the deep-crystallized silicic pluton, investigate conductive heat transfer in that zone, and study the evolution of the central resurgent dome. Core hole VC-4 is designed to penetrate deep into the presumably thick caldera fill in eastern Valles caldera and examine the relationship between caldera formation, sedimentation, tectonics, and volcanism. Core hole VC-5 is to test structure, stratigraphy, and magmatic evolution of pre-Valles caldera rocks, their relations to Valles caldera, and the influences of regional structure on volcanism and caldera formation.

  17. CSDP: The seismology of continental thermal regimes: Final report for period April 1, 1986-April 1, 1987

    SciTech Connect

    Aki, K.

    1987-07-01

    This report describes progress in the study of both wave propagation in complex structures and source mechanism of geothermal seismic events. The following work was accomplished in the past one-year period: (1) interpretation of long-period events observed at Mt. St. Helens and at the Fenton Hill hot-dry-rock experimental site in terms of seismic radiation from a fluid-filled crack; (2) interpretation of teleseismic data collected in and near the Valles caldera in terms of a model with irregular topography, caldera fill, and magma chamber; (3) interpretation of VSP (Vertical Seismic Profiling) data from the Oroville fault zone by ray tracing and polarization calculation for P, SV, and SH waves in heterogeneous and anisotropic media containing aligned fluid-filled and/or dry cracks; and (4) development of a new powerful method for calculating seismic motions in media with irregular topography and interfaces by the superposition of Gaussian Beams.

  18. Estimation of lifespan and economy parameters of steam-turbine power units in thermal power plants using varying regimes

    NASA Astrophysics Data System (ADS)

    Aminov, R. Z.; Shkret, A. F.; Garievskii, M. V.

    2016-08-01

    The use of potent power units in thermal and nuclear power plants in order to regulate the loads results in intense wear of power generating equipment and reduction in cost efficiency of their operation. We review the methodology of a quantitative assessment of the lifespan and wear of steam-turbine power units and estimate the effect of various operation regimes upon their efficiency. To assess the power units' equipment wear, we suggest using the concept of a turbine's equivalent lifespan. We give calculation formulae and an example of calculation of the lifespan of a steam-turbine power unit for supercritical parameters of steam for different options of its loading. The equivalent lifespan exceeds the turbine's assigned lifespan only provided daily shutdown of the power unit during the night off-peak time. We obtained the engineering and economical indices of the power unit operation for different loading regulation options in daily and weekly diagrams. We proved the change in the prime cost of electric power depending on the operation regimes and annual daily number of unloading (non-use) of the power unit's installed capacity. According to the calculation results, the prime cost of electric power for the assumed initial data varies from 11.3 cents/(kW h) in the basic regime of power unit operation (with an equivalent operation time of 166700 hours) to 15.5 cents/(kW h) in the regime with night and holiday shutdowns. The reduction of using the installed capacity of power unit at varying regimes from 3.5 to 11.9 hours per day can increase the prime cost of energy from 4.2 to 37.4%. Furthermore, repair and maintenance costs grow by 4.5% and by 3 times, respectively, in comparison with the basic regime. These results indicate the need to create special maneuverable equipment for working in the varying section of the electric load diagram.

  19. Factors controlling early stage salt tectonics at rifted continental margins and their thermal consequences

    NASA Astrophysics Data System (ADS)

    Goteti, Rajesh; Beaumont, Christopher; Ings, Steven J.

    2013-06-01

    We use 2-D thermomechanical models to investigate the early evolution of rifted margin salt tectonics in terms of the competition among margin tilt, salt flow, and sediment aggradation. Model experiments include initial geometry of the rifted margin and autochthonous salt basin, subsequent synrift and thermal subsidence, sediment and water loading, and sediment compaction. We also calculate the thermal evolution of the system to investigate the impact of the high thermal conductivity of the salt (halite). Model Set 1 demonstrates a two-phase response to salt deposition: short-term thermal equilibration between the salt and crust and longer-term relaxation in which the salt basin thermal image penetrates to a depth on the order of its width. Set 2 addresses the competition among margin tilt, salt flow, and sediment aggradation. Set 3 examines other factors, the salt basin width and depth, and the rifted margin width, which potentially affect the system evolution. Set 4 shows that sawtooth subsalt topography, representing faulted basement grabens, does not strongly impede salt flow. The model results are discussed in terms of a ternary diagram with apices representing tilt, salt flow, and sedimentation rates. Characteristic styles include the following: (1) tilt and rapid salt flow draining salt to the distal basin before the sediment aggrades, (2) an equivalent system with faster aggradation that captures draining salt as diapirs between minibasins, and (3) rapid sediment aggradation in which diapir-minibasins systems develop before the salt drains. Thermal consequences of these styles are discussed. A preliminary comparison shows that salt structures resembling these styles occur in the southwest Nova Scotian margin.

  20. Adapting of the Background-Oriented Schlieren (BOS) Technique in the Characterization of the Flow Regimes in Thermal Spraying Processes

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Rademacher, H. G.; Anjami, N.; Hagen, L.

    2014-01-01

    In thermal spraying technique, the changes in the in-flight particle velocities are considered to be only a function of the drag forces caused by the dominating flow regimes in the spray jet. Therefore, the correct understanding of the aerodynamic phenomena occurred at nozzle out let and at the substrate interface is an important task in the targeted improvement in the nozzle and air-cap design as well as in the spraying process in total. The presented work deals with the adapting of an innovative technique for the flow characterization called background-oriented Schlieren. The flow regimes in twin wire arc spraying (TWAS) and high velocity oxygen fuel (HVOF) were analyzed with this technique. The interfering of the atomization gas flow with the intersected wires causes in case of TWAS process a deformation of the jet shape. It leads also to areas with different aero dynamic forces. The configurations of the outlet air-caps in TWAS effect predominantly the outlet flow characteristics. The ratio between fuel and oxygen determine the dominating flow regimes in the HVOF spraying jet. Enhanced understanding of the aerodynamics at outlet and at the substrate interface could lead to a targeted improvement in thermal spraying processes.

  1. Estimating thermal regimes of bull trout and assessing the potential effects of climate warming on critical habitats

    USGS Publications Warehouse

    Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.; McGlynn, Brian L.; Kershner, Jeffrey L.

    2013-01-01

    Understanding the vulnerability of aquatic species and habitats under climate change is critical for conservation and management of freshwater systems. Climate warming is predicted to increase water temperatures in freshwater ecosystems worldwide, yet few studies have developed spatially explicit modelling tools for understanding the potential impacts. We parameterized a nonspatial model, a spatial flow-routed model, and a spatial hierarchical model to predict August stream temperatures (22-m resolution) throughout the Flathead River Basin, USA and Canada. Model comparisons showed that the spatial models performed significantly better than the nonspatial model, explaining the spatial autocorrelation found between sites. The spatial hierarchical model explained 82% of the variation in summer mean (August) stream temperatures and was used to estimate thermal regimes for threatened bull trout (Salvelinus confluentus) habitats, one of the most thermally sensitive coldwater species in western North America. The model estimated summer thermal regimes of spawning and rearing habitats at <13 C° and foraging, migrating, and overwintering habitats at <14 C°. To illustrate the useful application of such a model, we simulated climate warming scenarios to quantify potential loss of critical habitats under forecasted climatic conditions. As air and water temperatures continue to increase, our model simulations show that lower portions of the Flathead River Basin drainage (foraging, migrating, and overwintering habitat) may become thermally unsuitable and headwater streams (spawning and rearing) may become isolated because of increasing thermal fragmentation during summer. Model results can be used to focus conservation and management efforts on populations of concern, by identifying critical habitats and assessing thermal changes at a local scale.

  2. Lattice thermal conductivity of crystalline and amorphous silicon with and without isotopic effects from the ballistic to diffusive thermal transport regime

    SciTech Connect

    Park, Minkyu; Lee, In-Ho; Kim, Yong-Sung

    2014-07-28

    Thermal conductivity of a material is an important physical parameter in electronic and thermal devices, and as the device size shrinks down, its length-dependence becomes unable to be neglected. Even in micrometer scale devices, materials having a long mean free path of phonons, such as crystalline silicon (Si), exhibit a strong length dependence of the thermal conductivities that spans from the ballistic to diffusive thermal transport regime. In this work, through non-equilibrium molecular-dynamics (NEMD) simulations up to 17 μm in length, the lattice thermal conductivities are explicitly calculated for crystalline Si and up to 2 μm for amorphous Si. The Boltzmann transport equation (BTE) is solved within a frequency-dependent relaxation time approximation, and the calculated lattice thermal conductivities in the BTE are found to be in good agreement with the values obtained in the NEMD. The isotopic effects on the length-dependent lattice thermal conductivities are also investigated both in the crystalline and amorphous Si.

  3. Quantifying stream thermal regimes at management-pertinent scales: combining thermal infrared and stationary stream temperature data in a novel modeling framework.

    USGS Publications Warehouse

    Vatland, Shane J.; Gresswell, Robert E.; Poole, Geoffrey C.

    2015-01-01

    Accurately quantifying stream thermal regimes can be challenging because stream temperatures are often spatially and temporally heterogeneous. In this study, we present a novel modeling framework that combines stream temperature data sets that are continuous in either space or time. Specifically, we merged the fine spatial resolution of thermal infrared (TIR) imagery with hourly data from 10 stationary temperature loggers in a 100 km portion of the Big Hole River, MT, USA. This combination allowed us to estimate summer thermal conditions at a relatively fine spatial resolution (every 100 m of stream length) over a large extent of stream (100 km of stream) during during the warmest part of the summer. Rigorous evaluation, including internal validation, external validation with spatially continuous instream temperature measurements collected from a Langrangian frame of reference, and sensitivity analyses, suggests the model was capable of accurately estimating longitudinal patterns in summer stream temperatures for this system Results revealed considerable spatial and temporal heterogeneity in summer stream temperatures and highlighted the value of assessing thermal regimes at relatively fine spatial and temporal scales. Preserving spatial and temporal variability and structure in abiotic stream data provides a critical foundation for understanding the dynamic, multiscale habitat needs of mobile stream organisms. Similarly, enhanced understanding of spatial and temporal variation in dynamic water quality attributes, including temporal sequence and spatial arrangement, can guide strategic placement of monitoring equipment that will subsequently capture variation in environmental conditions directly pertinent to research and management objectives.

  4. Quantifying stream thermal regimes at multiple scales: Combining thermal infrared imagery and stationary stream temperature data in a novel modeling framework

    NASA Astrophysics Data System (ADS)

    Vatland, Shane J.; Gresswell, Robert E.; Poole, Geoffrey C.

    2015-01-01

    Accurately quantifying stream thermal regimes can be challenging because stream temperatures are often spatially and temporally heterogeneous. In this study, we present a novel modeling framework that combines stream temperature data sets that are continuous in either space or time. Specifically, we merged the fine spatial resolution of thermal infrared (TIR) imagery with hourly data from 10 stationary temperature loggers in a 100 km portion of the Big Hole River, MT, USA. This combination allowed us to estimate summer thermal conditions at a relatively fine spatial resolution (every ˜100 m of stream length) over a large extent of stream (˜100 km of stream) during the warmest part of the summer. Rigorous evaluation, including internal validation, external validation with spatially continuous instream temperature measurements collected from a Langrangian frame of reference, and sensitivity analyses, suggests the model was capable of accurately estimating longitudinal patterns in summer stream temperatures for this system (validation RMSEs < 1°C). Results revealed considerable spatial and temporal heterogeneity in summer stream temperatures and highlighted the value of assessing thermal regimes at relatively fine spatial and temporal scales. Preserving spatial and temporal variability and structure in abiotic stream data provides a critical foundation for understanding the dynamic, multiscale habitat needs of mobile stream organisms. Similarly, enhanced understanding of spatial and temporal variation in dynamic water quality attributes, including temporal sequence and spatial arrangement, can guide strategic placement of monitoring equipment that will subsequently capture variation in environmental conditions directly pertinent to research and management objectives.

  5. Yellowstone National Park as an opportunity for deep continental drilling in thermal regions. [Abstract only

    SciTech Connect

    Fournier, R.O.

    1983-03-01

    The Yellowstone caldera represnets the most intense magnatic and thermal anomaly within the conterminous United States. Voluminous rhyolite ash flows, accompanied by formation of huge calderas, occurred approximately 2.0, 1.3, and 0.6 My B.P. Although the last lava flow was about 70,000 B.P., much evidence suggests that magma may still be present at relatively shallow depth. The evidence from gravity and magnetic lows, magnetotelluric soundings, seismic wave velocities, maximum depths of earthquake foci, significant recent uplift of the caldera floor, and exceptionally high heat flux suggest that magmatic temperatures may be attained 5 to 10 km beneath much of the caldera. Most of the hot-spring and geyser activity occurs within the caldera and along a fault zone that trends north from the caldera rim through Norris Geyser Basin and Mammoth Hot Springs. The thermal waters and gases have been extensively sampled and analyzed over a period of 100 years. The chemical, isotopic, and hydrologic data obtained from natural discharges and from shallow wells drilled in thermal areas, enable formulation of models of the hydrothermal system. No previous intermediate-depth drilling has been conducted at Yellowstone to help select the best location for a deep drill hole, and because Yellowstone is a National Park, no commercial drilling will be available for add-on experiments. Also, a deep drill hole in Yellowstone would have to be sited with great regard to environmental and ecological considerations. Nevertheless, the large amount of existing data is sufficient to formulate testable models. The Yellowstone thermal anomaly is so extensive and scientifically interesting that almost any suitable drilling site there may be superior to the best drilling site in any other silicic caldera complex in the United States.

  6. Operational Constraints on Hydropeaking and its Effects on the Hydrologic and Thermal Regime of a River in Central Chile

    NASA Astrophysics Data System (ADS)

    Olivares, M. A.; Guzman, C.; Rossel, V.; De La Fuente, A.

    2013-12-01

    Hydropower accounts for about 44% of installed capacity in Chile's Central Interconnected System, which serves most of the Chilean population. Hydropower reservoir projects can affect ecosystems by changing the hydrologic regime and water quality. Given its volumen regulation capacity, low operation costs and fast response to demand fluctuations, reservoir hydropower plants commonly operate on a load-following or hydropeaking scheme. This short-term operational pattern produces alterations in the hydrologic regime downstream the reservoir. In the case of thermally stratified reservoirs, peaking operations can affect the thermal structure of the reservoir, as well as the thermal regime downstream. In this study, we assessed the subdaily hydrologic and thermal alteration donwstream of Rapel reservoir in Central Chile for alternative operational scenarios, including a base case and several scenarios involving minimum instream flow (Qmin) and maximum hourly ramping rates (ΔQmax). Scenarios were simulated for the stratification season of summer 2009-2012 in a grid-wide short-term economic dispatch model which prescribes hourly power production by every power plant on a weekly horizon. Power time series are then translated into time series of turbined flows at each hydropower plants. Indicators of subdaily hydrologic alteration (SDHA) were computed for every scenario. Additionally, turbined flows were used as input data for a three-dimensional hydrodynamic model (CWR-ELCOM) of the reservoir which simulated the vertical temperature profile in the reservoir and the outflow temperature. For the time series of outflow temperatures we computed several indicators of subdaily thermal alteration (SDTA). Operational constraints reduce the values of both SDHA and SDTA indicators with respect to the base case. When constraints are applied separately, the indicators of SDHA decrease as each type of constraint (Qmin or ΔQmax) becomes more stringent. However, ramping rate

  7. Heat flow in eastern Egypt - The thermal signature of a continental breakup

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

    1985-01-01

    Data on the heat flow in eastern Egypt were collected to provide information related to the mode and the mechanism of the Red Sea opening. The data indicate a general increase in heat flow towards the Red Sea (75-100 mW/sq m in a zone within 40 km of the coast compared with 35-55 mW/sq m inland). Moderately high heat flow (about 70 mW/sq m) was found for the Gulf of Suez. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. Possible causes of the anomaly (one of which could be a high mantle heat flow causing a lithospheric thinning centered beneath the Red Sea) are discussed.

  8. Estimate of the influence of thermophysical parameter deviations on SC thermal regime

    NASA Astrophysics Data System (ADS)

    Petrov, Yu. V.; Rassamakin, B. M.; Taranova, T. A.; Khoroshylov, V. S.

    The necessity of accurate information on actual values of thermophysical properties for the SC with passive thermal control system is substantiated. On the basis of the telemetry information from the temperature sensors of the AUOS-SM-KF SC, the degradation of black enamel AK-512 is analyzed using inverse-scattering method as well as effective thermal conductivity of honeycomb panel and embedded heat-pipes is evaluated.

  9. Pollen and palynofacies analyses of Paleocene-Eocene Thermal Maximum sediments from the North American continental shelf

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Robinson, M. M.; Self-Trail, J. M.; Wandless, G. A.; Sluijs, A.

    2014-12-01

    Analyses of pollen and palynofacies from Paleocene-Eocene Thermal Maximum (PETM) sediments from three cores collected on the Atlantic Coastal Plain provide insights into the timing of vegetation and hydrologic changes associated with the PETM in eastern North America. The Mattawoman Creek-Billingsley Road (MCBR2), South Dover Bridge (SDB), and Bass River (ODP Site 1074AX) cores were collected at progressively greater distances from the paleoshoreline in continental shelf deposits in Maryland and New Jersey, USA. The PETM carbon isotope excursion (CIE) at each site is accompanied by sharp increases in pollen and spore concentrations, as well as changes in terrestrial palynomorph assemblage composition. In the two sites proximal to the paleoshoreline in Maryland, CIE fern spore abundance was two- to three times greater than in pre-CIE assemblages. At the distal site at Bass River, fern spores are present in CIE sediments and absent in pre-CIE sediments. Angiosperm pollen is most common in CIE sediments at all three sites. Palynofacies analyses, which quantify contributions of organic material from marine and non-marine sources, indicate that terrestrial influx increased sharply at the CIE onset. This observation is consistent with seasonally increased runoff from the continent.

  10. Insect cold tolerance and repair of chill-injury at fluctuating thermal regimes: role of ion homeostasis.

    PubMed

    Kostál, V; Renault, D; Mehrabianová, A; Bastl, J

    2007-05-01

    Adults of the bug Pyrrhocoris apterus and the beetle Alphitobius diaperinus developed chill-injury slower and survived longer when they were exposed to fluctuating thermal regimes (FTRs, where periods of low temperature were alternated with periods of higher temperature on a daily basis) rather than to constant low temperatures. The extracellular (haemolymph) concentrations of potassium ions increased with significantly higher rates in the insects exposed to constant low temperatures than in those exposed to FTRs. The concentrations of magnesium and sodium ions were maintained relatively constant or decreased slightly in both thermal regimes. The loss of body water and the increase of haemolymph osmolality contributed to, but could not fully explain, the ion concentration changes, which probably resulted also from impairing the function of an active metabolic component (ion pump) at low temperatures. This explanation was supported by observing (in P. apterus) the return toward normal [K+] during the warm "recovery" period of the FTR. Collectively, the paper stresses the importance of considering the temperature fluctuations in the experimental studies on insect cold tolerance and suggests that the positive effect of the FTR on cold tolerance may consist, at least partially, in allowing the primary ion pumping systems to re-establish the ion gradients across cell membranes and epithelia during the recovery periods at a higher temperature.

  11. A fluctuating thermal regime improves survival of cold-mediated delayed emergence in developing Megachile rotundata (Hymenoptera: Megachilidae).

    PubMed

    Rinehart, Joseph P; Yocum, George D; West, Mark; Kemp, William P

    2011-08-01

    A significant concern in the commercial application of the alfalfa leafcutting bee, Megachile rotundata (F.) (Hymenoptera: Megachilidae), for pollination is synchronizing bee emergence and activity with peak crop bloom. Previous studies have demonstrated that the commercial spring incubation of this species can be successfully interrupted by low temperature incubation, thereby slowing development and giving producers flexibility in timing emergence to weather conditions or crop bloom. In this study, we demonstrate that the implementation of a fluctuating thermal regime, during which bees are given a daily one hour pulse of high temperature, markedly increases the "shelf-life" of individuals of this species. Although constant temperatures can be used to store bees for up to 1 wk with no decrease in survival, properly staged bees can be stored for up to 6 wk without a significant decrease in percentage of emergence. Hence, we expect fluctuating thermal regime protocols to become a valuable tool for M. rotundata managers, especially when timing nesting activity with peak bloom to maximize effectiveness. PMID:21882678

  12. Contrasted thermal regimes do not influence digestion and growth rates in a snake from a temperate climate.

    PubMed

    Michel, Catherine Louise; Bonnet, Xavier

    2010-01-01

    Temperature influences almost all life-history traits. For a period of 3 mo, we placed four groups of snakes under four contrasted thermal treatments: (1) a natural regime (NR), based on daily variations (24-h cycle); (2) an accelerated regime (AR), where the thermoperiod fluctuated rapidly (12-h cycle); (3) a slow regime (SR; 48-h cycle); and (4) a cool stable regime (ZR; no fluctuation). The mean temperature, set at 23°C, was identical for the four groups. For the first three groups (NR, AR, SR), ambient temperature fluctuated between 18°C and 28°C. Relative humidity and photoperiod were constant. We recorded feeding success, digestion efficiency, growth rate, activity, and ecdysis events. Differences between groups were expected because of varied exposure to the optimal temperatures, most notably in the ZR group, where the preferred body temperature for digestion (approximately 30°C) would not be reached. Surprisingly, there was no significant effect of the experimental treatment on feeding rate, digestion, body mass increase, and growth rate. Our results do not conform to the paradigm stipulating that maximal body temperature selected by ectotherms necessarily corresponds to the most efficient for resource assimilation and that temperature fluctuations are essential. We propose that increasing the digestive tract's performance through body-temperature elevation trades off against elevated (parasite) energy expenditure from the rest of the body. The main advantage of high body temperatures would be to reduce the amount of time necessary to assimilate prey rather than to improve the net mass gain during digestion.

  13. Detailed predictions of climate induced changes in the thermal and flow regimes in mountain streams of the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Santiago, José M.; Muñoz-Mas, Rafael; García de Jalón, Diego; Solana, Joaquín; Alonso, Carlos; Martínez-Capel, Francisco; Ribalaygua, Jaime; Pórtoles, Javier; Monjo, Robert

    2016-04-01

    Streamflow and temperature regimes are well-known to influence on the availability of suitable physical habitat for instream biological communities. General Circulation Models (GCMs) have predicted significant changes in timing and geographic distribution of precipitation and atmospheric temperature for the ongoing century. However, differences in these predictions may arise when focusing on different spatial and temporal scales. Therefore, to perform substantiated mitigation and management actions detailed scales are necessary to adequately forecast the consequent thermal and flow regimes. Regional predictions are relatively abundant but detailed ones, both spatially and temporally, are still scarce. The present study aimed at predicting the effects of climate change on the thermal and flow regime in the Iberian Peninsula, refining the resolution of previous studies. For this purpose, the study encompassed 28 sites at eight different mountain rivers and streams in the central part of the Iberian Peninsula (Spain). The daily flow was modelled using different daily, monthly and quarterly lags of the historical precipitation and temperature time series. These precipitation-runoff models were developed by means of M5 model trees. On the other hand water temperature was modelled at similar time scale by means of nonlinear regression from dedicated site-specific data. The developed models were used to simulate the temperature and flow regime under two Representative Concentration Pathway (RCPs) climate change scenarios (RCP 4.5 and RCP 8.5) until the end of the present century by considering nine different GCMs, which were pertinently downscaled. The precipitation-runoff models achieved high accuracy (NSE>0.7), especially in regards of the low flows of the historical series. Results concomitantly forecasted flow reductions between 7 and 17 % (RCP4.5) and between 8 and 49% (RCP8.5) of the annual average in the most cases, being variable the magnitude and timing at each

  14. Thermal regime of the Escalante Desert, Utah, with an analysis of the the Newcastle Geothermal System

    SciTech Connect

    Chapman, D.S.; Clement, M.D.; Mase, C.W.

    1981-12-10

    Twenty-five new heat flow measurements are presented for the Escalante Desert region within the Great Basin of the wester United States. Heat flow, excluding geothermal areas, ranges from 43 to 350 mW m/sup -2/, but much of the variability may be caused by deeply circulating groundwater redistributing the regional flux. A subset of 10 sites drilled specifically to characterize the heat flow of the region yielded a mean of 100 mW m/sup -2/ with a standard deviation of 22 mW m/sup -2/. A comparison of thermal conductivities of solid cylindrical discs and rock chips (rhyolite to andesite tuffs) confirmed the importance of porosity corrections to thermal conductivity measurements. A 'blind' geothermal system southwest of Newastle, Utah, situated within the Escalante Desert, has also been studied. Temperature Desert, has also been studied. Temperatures of 110/sup 0/C are observed only 75 m below the ground surface. Heat flow results from 11 drillholes in this region yield values between 163 and 3065 mW m/sup -2/. The 500 mW m/sup -2/ contour encloses an area of 9.4 km/sup 2/. By integrating the excess heat flux (above background) over the thermal anomaly, we deduce a thermal power loss of 12.8 MW for this geothermal system, which corresponds to a subsurface water discharge of 32 kg s/sup -1/.

  15. Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequences.

    PubMed

    Angilletta, Michael J; Ashley Steel, E; Bartz, Krista K; Kingsolver, Joel G; Scheuerell, Mark D; Beckman, Brian R; Crozier, Lisa G

    2008-05-01

    Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. PMID:25567632

  16. Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequences

    PubMed Central

    Angilletta, Michael J; Ashley Steel, E; Bartz, Krista K; Kingsolver, Joel G; Scheuerell, Mark D; Beckman, Brian R; Crozier, Lisa G

    2008-01-01

    Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. PMID:25567632

  17. Variscan to Neogene thermal and exhumation history at the Moroccan passive continental margin assessed by low temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Sehrt, M.; Glasmacher, U. A.; Stockli, D. F.; Kluth, O.; Jabour, H.

    2012-04-01

    In North Africa, a large amount of Mesozoic terrigenous sedimentary rocks are deposited in most of the basins along the continental margin indicating a major episode of erosion occurred during the rift and early post-rift period in the Central Atlantic. In the Tarfaya-Dakhla Basin, Morocco the sedimentary cover reaches thicknesses of up to 9000 m. The presence of high surface elevations in the Anti-Atlas mountain belt (2500 m) indicates a potential source area for the surrounding basins. The NE-SW oriented Anti-Atlas of Morocco is located at the northwestern fringe of the West African Craton and south of the High Atlas and represents the Phanerozoic foreland of the Late Paleozoic North African Variscides and the Cenozoic Atlas Belt. Variscan deformation affected most of Morocco. Paleozoic basins were folded and thrusted, with the major collision dated as late Devonian to Late Carboniferous. Zircon fission-track ages of 287 (±23) to 331 (±24) Ma confirmed the main exhumation referred to the Variscan folding, followed by rapid exhumation and the post-folding erosion. Currently, phases of uplift and exhumation in the Anti-Atlas during the Central Atlantic rifting and places where the associated erosion products are deposited are poorly constrained and there is little quantitative data available at present. The objective of the study is to determine the thermal and exhumation history of the Anti-Atlas and the connected Tarfaya-Dakhla Basin at the Moroccan passive continental margin. Besides zircon fission-track dating, apatite and zircon (U-Th-Sm)/He and apatite fission-track analyses and furthermore 2-D modelling with 'HeFTy' software has been carried out at Precambrian rocks of the Western Anti-Atlas and Cretaceous to Neogene sedimentary rocks from the Northern Tarfaya-Dakhla Basin. The apatite fission-track ages of 120 (±13) to 189 (±14) Ma in the Anti-Atlas and 176 (±20) to 216 (±18) Ma in the Tarfaya Basin indicate very obvious a Central Atlantic opening

  18. Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico ( USA).

    USGS Publications Warehouse

    Sass, J.H.; Morgan, P.

    1988-01-01

    Over 5% of heat in the western USA is lost through Quaternary silicic volcanic centers, including the Valles caldera in N central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. Presents new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the SW margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 + or - 16 mW m-2. Inteprets the shallow thermal gradient data and the thermal regime at VC-1 to indicate a long-lived hydrothermal (and magmatic) system in the southwestern Valles caldera that has been maintained through the generation of shallow magma bodies during the long postcollapse history of the caldera. High heat flow at the VC-1 site is interpreted to result from hot water circulating below the base of the core hole, and we attribute the lower heat flow in the unsaturated zone is attributed to hydrologic recharge. -from Authors

  19. Thermal regime of the State 2-14 well, Salton Sea Scientific Drilling Project

    USGS Publications Warehouse

    Sass, J.H.; Priest, S.S.; Duda, L.E.; Carson, C.C.; Hendricks, J.D.; Robison, L.C.

    1988-01-01

    Temperature logs were made repeatedly during breaks in drilling and both during and after flow tests in the Salton Sea Scientific Drilling Project well (State 2-14). The purpose of these logs was to assist in identifying zones of fluid loss or gain and to characterize reservoir temperatures. At the conclusion of the active phase of the project, a series of logs was begun in an attempt to establish the equilibrium temperature profile. Thermal gradients decrease from about 250 mK m-1 in the upper few hundred meters to just below 200 mK m-1 near the base of the conductive cap. Using one interpretation, thermal conductivities increase with depth (mainly because of decreasing porosity), resulting in component heat flows that agree reasonably well with the mean of about 450 mW m-2. This value agrees well with heat flow data from the shallow wells within the Salton Sea geothermal field. A second interpretation, in which measured temperature coefficients of quartz- and carbonate-rich rocks are used to correct thermal conductivity, results in lower mean conductivities that are roughly constant with depth and, consequently, systematically decreasing heat flux averaging about 350 mW m-2 below 300 m. This interpretation is consistent with the inference (from fluid inclusion studies) that the rocks in this part of the field were once several tens of degrees Celsius hotter than they are now. The age of this possible disturbance is estimated at a few thousand years. -from Authors

  20. Deep observation and sampling of the earth's continental crust (DOSECC). Final report

    SciTech Connect

    Not Available

    1985-05-01

    The need to validate and refine concepts regarding the structure, properties, and dynamic processes of the earth's continental crust through the use of the drill was the subject of the workshop sponsored by DOSECC, Inc. and held April 29 through May 1, 1985 in Houston, Texas and attended by more than 145 scientists. Scientific objectives and targets for a program of research drilling as part of basic studies of the continental lithosphere were discussed, with over 30 scientific proposals presented. Individual drilling proposals were grouped under several themes; basement structures and deep continental basins, active fault zones, thermal regimes and fossil mineralized hydrothermal/magma systems.

  1. Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain.

    PubMed

    Bédard, Emilie; Boppe, Inès; Kouamé, Serge; Martin, Philippe; Pinsonneault, Linda; Valiquette, Louis; Racine, Jules; Prévost, Michèle

    2016-01-01

    Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila.

  2. Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain.

    PubMed

    Bédard, Emilie; Boppe, Inès; Kouamé, Serge; Martin, Philippe; Pinsonneault, Linda; Valiquette, Louis; Racine, Jules; Prévost, Michèle

    2016-01-01

    Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila. PMID:27092528

  3. Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain

    PubMed Central

    Bédard, Emilie; Boppe, Inès; Kouamé, Serge; Martin, Philippe; Pinsonneault, Linda; Valiquette, Louis; Racine, Jules; Prévost, Michèle

    2016-01-01

    Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila. PMID:27092528

  4. Evaluation of thermal regimes for transported ambassador ectotherms: One size does not fit all.

    PubMed

    Tetzlaff, Sasha J; Tetzlaff, Kristin E; Connors, Richard J

    2016-07-01

    Providing appropriate environmental temperatures for captive ectotherms should be a husbandry priority. This can be especially challenging for ectotherms that are routinely transported, such as those used in education programs at zoos, because they are unable to thermoregulate while confined in non-temperature controlled, compact carriers. To assess if ectotherms used in the Fort Wayne Children's Zoo's outreach programs experienced appropriate transit temperatures during cold weather, we placed temperature loggers inside two sizes of transport carriers, half containing a heat source (bottle of hot water) and half not (control). While transport temperatures were appropriate for many ectotherms, this simple procedure failed to meet the thermal preferences of species with relatively low or high preferred temperatures such as the eastern tiger salamander (Ambystoma tigrinum) and the spiny-tailed lizard (Uromastyx maliensis), respectively. We found large heated carriers were warmer than small heated carriers, but the temperatures of control carriers did not differ. Despite considerable interspecific variation, large heated carriers provided higher thermal quality environments than both small heated and control carriers for all species except eastern tiger salamanders. We suggest further thermal monitoring of ectotherms during transit with the aim of identifying appropriate heat sources and developing efficient and effective transportation protocols. This could be achieved by modifying transport carriers so that animals are able to thermoregulate. Limiting or ceasing their use when appropriate temperatures cannot be provided may be necessary. Particular attention should be given to species with temperature preferences markedly different than the majority of others in a given collection. Zoo Biol. 35:339-345, 2016. © 2016 Wiley Periodicals, Inc. PMID:27007783

  5. Arctic Oscillation impact on thermal regime of the Baltic region Eastern part

    NASA Astrophysics Data System (ADS)

    Gecaite, Indre; Pogoreltsev, Aleksandr; Ugryumov, Aleksandr

    2016-04-01

    Statistical estimations of Arctic Oscillation (AO) impact on air temperature regime in the Eastern part of Baltic region are presented. The region is characterized by high inter-annual and inter-seasonal variabilities. It is important to note that in the region of global warming extremely low winter temperatures can be observed on the European territory of Russia. AO is one of large-scale global structures of atmospheric circulation closely associated with weather variability in Northern Europe. AO anomalies occur in the upper atmosphere (stratosphere) and only then transferred to tropospheric lower layers. The anomalies can be preserved during long period up to two months, so they can be predictors in long-range weather forecast. In turn, changes in stratospheric polar vortex and sudden stratospheric warmings can be related to the geomagnetic activity. Perhaps, the geomagnetic activity influences the meridional temperature gradient and then changes in the structure of the stratospheric zonal wind. In turn, the changes have an impact on the tropospheric circulation. The stratosphere-troposphere connection occurs during winter months. Therefore, the paper presents the analysis of extremely cold winter anomalies in the Eastern part of Baltic Sea region. At the same time, we considered atmospheric circulation peculiarities related to AO phase change. The analyzable time interval covers 1951-2014.

  6. A modeling assessment of the thermal regime for an urban sport fishery

    NASA Astrophysics Data System (ADS)

    Bartholow, John M.

    1991-11-01

    Water temperature is almost certainly a limiting factor in the maintenance of a self-sustaining rainbow trout ( Oncorhynchus mykiss, formerly Salmo gairdneri) and brown trout ( Salmo trutta) fishery in the lower reaches of the Cache la Poudre River near Fort Collins, Colorado, USA. Irrigation diversions dewater portions of the river, but cold reservoir releases moderate water temperatures during some periods. The US Fish and Wildlife Service’s Stream Network Temperature Model (SNTEMP) was applied to a 31-km segment of the river using readily available stream geometry and hydrological and meteorological data. The calibrated model produced satisfactory water temperature predictions ( R 2=0.88, P<0.001, N=49) for a 62-day summer period. It was used to evaluate a variety of flow and nonflow alternatives to keep water temperatures below 23.3°C for the trout. Supplemental flows or reduced diversions of 3 m3/sec would be needed to maintain suitable summer temperatures throughout most of the study area. Such flows would be especially beneficial during weekends when current irrigation patterns reduce flows. The model indicated that increasing the riparian shade would result in little improvement in water temperatures but that decreasing the stream width would result in significant temperature reductions. Introduction of a more thermally tolerant redband trout ( Oncorhynchus sp.), or smallmouth bass ( Micropterus dolomieui) might prove beneficial to the fishery. Construction of deep pools for thermal refugia might also be helpful.

  7. A modeling assessment of the thermal regime for an urban sport fishery

    USGS Publications Warehouse

    Bartholow, John M.

    1991-01-01

    Water temperature is almost certainly a limiting factor in the maintenance of a self-sustaining rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri) and brown trout (Salmo trutta) fishery in the lower reaches of the Cache la Poudre River near Fort Collins, Colorado, USA. Irrigation diversions dewater portions of the river, but cold reservoir releases moderate water temperatures during some periods. The US Fish and Wildlife Service’s Stream Network Temperature Model (SNTEMP) was applied to a 31-km segment of the river using readily available stream geometry and hydrological and meteorological data. The calibrated model produced satisfactory water temperature predictions (R2=0.88,P3/sec would be needed to maintain suitable summer temperatures throughout most of the study area. Such flows would be especially beneficial during weekends when current irrigation patterns reduce flows. The model indicated that increasing the riparian shade would result in little improvement in water temperatures but that decreasing the stream width would result in significant temperature reductions. Introduction of a more thermally tolerant redband trout (Oncorhynchus sp.), or smallmouth bass (Micropterus dolomieui) might prove beneficial to the fishery. Construction of deep pools for thermal refugia might also be helpful.

  8. Thermal regime, predation danger and the early marine exit of sockeye salmon Oncorhynchus nerka.

    PubMed

    Katinic, P J; Patterson, D A; Ydenberg, R C

    2015-01-01

    Marine exit timing of sockeye salmon Oncorhynchus nerka populations on the Haida Gwaii Archipelago, British Columbia, Canada, is described, with specific focus on Copper Creek. Marine exit in Copper Creek occurs > 130 days prior to spawning, one of the longest adult freshwater residence periods recorded for any O. nerka population. Copper Creek presents an easy upstream migration, with mild water temperatures (7 to 14°  C), short distance (13·1 km) and low elevation gain (41 m) to the lake where fish hold prior to spawning. An energetic model estimates that <1% of the initial energy reserve is required for upstream migration, compared with 62% for lake holding and 38% for reproductive development. Historical records suggest that it is unlikely that water temperature in any of the O.nerka streams in Haida Gwaii has ever exceeded the presumed temperature threshold (19° C) for early marine exit. Although it is not impossible that the thermal tolerance of Copper Creek O.nerka is very low, the data presented here appear inconsistent with thermal avoidance as an explanation for the early marine exit timing in Copper Creek and in three other populations on the archipelago with early marine exit. PMID:25494933

  9. Fast Regime Fluidized Bed Machining (FR-FBM) of Thermally Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Barletta, Massimiliano; Rubino, Gianluca; Bolelli, Giovanni; Lusvarghi, Luca

    2008-12-01

    Finishing of thermally sprayed metallic, ceramic, and cermet coatings is required to meet tolerances and requirements on surface roughness in most industrial applications. Conventional machining is a costly and time-consuming process, and is difficult to automate. Therefore, this study investigates and develops a new technique highly amenable for automation: fast regime—fluidized bed machining (FR-FBM). Atmospheric plasma sprayed TiO2, Cr2O3, and HVOF-sprayed WC-17%Co and Tribaloy-800 coatings, deposited on AISI 1040 steel substrates, were subjected to FR-FBM treatment. The effects of the leading operational parameters, namely, abrasive size, jet pressure, and processing time, were evaluated on all coatings by using a two/three-levels full factorial design of experiments. The FR-FBM treated surfaces were observed by FE-SEM and their surface finishing was evaluated by contact profilometry. Significant improvements in surface finishing of all the machined thermally sprayed coatings can always be detected, with FR-FBM being able to guarantee the precision and to ensure the closest geometrical tolerances.

  10. Exploring thermal imaging variables for the detection of stress responses in grapevine under different irrigation regimes.

    PubMed

    Grant, Olga M; Tronina, Lukasz; Jones, Hamlyn G; Chaves, M Manuela

    2007-01-01

    Temperatures of leaves or canopies can be used as indicators of stomatal closure in response to soil water deficit. In 2 years of field experiments with grapevines (Vitis vinifera L., cvs Castelão and Aragonês), it was found that thermal imaging can distinguish between irrigated and non-irrigated canopies, and even between deficit irrigation treatments. Average canopy temperature was inversely correlated with stomatal conductance measured with a porometer. Variation of the distribution of temperatures within canopies was not found to be a reliable indicator of stress. A large degree of variation between images was found in reference 'wet' and 'dry' leaves used in the first year for the calculation of an index proportional to stomatal conductance. In the second year, fully irrigated (FI) (100% Et(c)) and non-irrigated (NI) canopies were used as alternatives to wet and dry leaves. A crop water stress index utilizing these FI and NI 'references', where stressed canopies have the highest values and non-stressed canopies have the lowest values, was found to be a suitable measure for detecting stress. It is suggested that the average temperatures of areas of canopies containing several leaves may be more useful for distinguishing between irrigation treatments than the temperatures of individual leaves. Average temperatures over several leaves per canopy may be expected to reduce the impact of variation in leaf angles. The results are discussed in relation to the application of thermal imaging to irrigation scheduling and monitoring crop performance. PMID:17032729

  11. Thermal regime of shallow water bodies in the coastal tundra zone of the Hudson Bay Lowlands

    NASA Astrophysics Data System (ADS)

    Duguay, C. R.; Soliman, A. S.; Macrae, M. L.

    2011-12-01

    Many shallow lakes and ponds of the Arctic/sub-Arctic contain thick, organic-rich sediments, which have the potential to release significant amounts of CO2 or CH4 to the atmosphere if sediment decomposition rates increase in response to warmer temperatures caused by global warming. This may be exacerbated by a deepening of the seasonal sediment thaw depth in small water bodies that are underlain by permafrost. An important step in linking climatic conditions to rates of organic matter decomposition and gas production from shallow water bodies is an improved understanding of the thermal properties of lake sediments and how sediment temperatures fluctuate in response to changing air temperatures. This knowledge is also important if the ratio of terrestrial to aquatic landscape units in cold regions changes under a warmer climate. One approach that has been used in terrestrial permafrost environments is the examination of how mean annual permafrost surface temperature deviates from mean annual 2-m screen height air temperature (MAAT). The offset between MAAT and the mean annual sediment surface temperature (MASST) has been found to be much larger in deep aquatic systems (greater than 10 m) than in terrestrial permafrost systems due to the presence of the water column that can efficiently transfer heat through mixing. However, the efficiency of heat transfer in shallow water bodies is expected to larger in summer (thawed) than in winter (frozen) conditions, when thermal energy must move by conduction alone. The present study examined the efficiency of sediment heat transfer in shallow water bodies (less than 3 m) during summer and winter periods. Air, sediment and water temperatures of three shallow water bodies in the coastal tundra zone of the Hudson Bay Lowlands near Churchill, Manitoba, Canada were monitored (December 2009-August 2011). Arrays of thermistors and heat pulse probes were placed at 10 cm increments between 20 cm above the water/sediment interface and

  12. Redefining thermal regimes to design reserves for coral reefs in the face of climate change.

    PubMed

    Chollett, Iliana; Enríquez, Susana; Mumby, Peter J

    2014-01-01

    Reef managers cannot fight global warming through mitigation at local scale, but they can use information on thermal patterns to plan for reserve networks that maximize the probability of persistence of their reef system. Here we assess previous methods for the design of reserves for climate change and present a new approach to prioritize areas for conservation that leverages the most desirable properties of previous approaches. The new method moves the science of reserve design for climate change a step forwards by: (1) recognizing the role of seasonal acclimation in increasing the limits of environmental tolerance of corals and ameliorating the bleaching response; (2) using the best proxy for acclimatization currently available; (3) including information from several bleaching events, which frequency is likely to increase in the future; (4) assessing relevant variability at country scales, where most management plans are carried out. We demonstrate the method in Honduras, where a reassessment of the marine spatial plan is in progress.

  13. Redefining Thermal Regimes to Design Reserves for Coral Reefs in the Face of Climate Change

    PubMed Central

    Chollett, Iliana; Enríquez, Susana; Mumby, Peter J.

    2014-01-01

    Reef managers cannot fight global warming through mitigation at local scale, but they can use information on thermal patterns to plan for reserve networks that maximize the probability of persistence of their reef system. Here we assess previous methods for the design of reserves for climate change and present a new approach to prioritize areas for conservation that leverages the most desirable properties of previous approaches. The new method moves the science of reserve design for climate change a step forwards by: (1) recognizing the role of seasonal acclimation in increasing the limits of environmental tolerance of corals and ameliorating the bleaching response; (2) using the best proxy for acclimatization currently available; (3) including information from several bleaching events, which frequency is likely to increase in the future; (4) assessing relevant variability at country scales, where most management plans are carried out. We demonstrate the method in Honduras, where a reassessment of the marine spatial plan is in progress. PMID:25333380

  14. Thermal regime of the Great Basin and its implications for hydrocarbon occurrence

    SciTech Connect

    Sass, J.H.; Williams, C.F.

    1995-06-01

    The Great Basin is a province of high average heat flow (92+-9 mW m{sup -2}), but it contains sub-provinces of both higher and lower heat flow. Higher heat flow (>100 mW m{sup -2}) is characteristic of the north-central Great Basin (the Battle Mountain High, BMH) and several smaller areas along its margins. There is also a large area of lower heat flow (<60 mW m{sup -2}, the Eureka Low, EL) in the south-central portion of the province. There is hydrologic and thermal evidence that the EL is a shallow ({approximately}3 km) hydrologically controlled heat sink associated with interbasin water flow. For example, the temperature profile from a 3.7 km deep hole at Pahute Mesa in the EL indicates low heat flow in the upper 1.5 km and high heat flow in the lowermost kilometer. On the other hand, seismic and magnetic studies suggest that the heat sink in the EL extends to at least mid-crustal depths. Temperatures in the deeper parts of many basins in the BMH are higher than considered favorable for generation or stability of oil. Paradoxically, temperature-gradients as high as 100{degrees}C km{sup -1} and an underlying hydrothermal system are found within the EL in Railroad Valley, the site of the most productive oil-fields in the Great Basin. The heat source driving this hydrothermal system is a combination of local upward flow from the Paleozoic carbonate aquifer and possible thermal input from nearby igneous activity. J. B. Hulen and others have suggested that the Railroad Valley hydrothermal system has enhanced hydrocarbon transport and accelerated maturation. If a hydrothermal system is required for the formation of significant hydrocarbon reservoirs in the EL, then such reservoirs will occur only where groundwater flow in the carbonate aquifer is not removing heat from the basins.

  15. Paleocene-Eocene Thermal Maximum (PETM) and its Effects on Continental Biotas: Evidence from Polecat Bench in Northwestern Wyoming

    NASA Astrophysics Data System (ADS)

    Gingerich, P. D.

    2012-12-01

    Many important environmental events in the geological past were first recognized by their effects on the associated biota, and this is true for the Paleocene-Eocene Thermal Maximum or PETM global greenhouse warming event, which happened 55 million years before present. In the Southern Ocean, PETM carbon and oxygen isotope anomalies were found to coincide with a major terminal-Paleocene disappearance or extinction of benthic foraminiferans. On North America the PETM carbon isotope excursion (CIE) was found to coincide with mammalian dwarfing and a major initial-Eocene appearance or origination event of continental mammals. Linking the two records, marine and continental, resolved a long-standing disagreement over competing definitions of the Paleocene-Eocene epoch boundary, and more importantly indicated that the PETM greenhouse warming event was global. Dwarfing of herbivorous mammals can be interpreted as a response to elevated atmospheric CO2. The origin of modern orders of mammals including Artiodactyla, Perissodactyla, and Primates ('APP' taxa) is more complicated and difficult to explain but the origin of these orders may also be a response, directly or indirectly, to PETM warming. We now know from Polecat Bench and elsewhere in North America that the biotic response to PETM greenhouse warming involved the appearance of at least two new mammalian faunas distinct from previously known Clarkforkian mammals of the upper or late Paleocene and previously known Wasatchian mammals of the lower or early Eocene. Three stages and ages of the former are known (Cf-1 to Cf-3) and seven stages and ages of the latter are known (Wa-1 to Wa-7), each occupying about a hundred meters of strata representing a half-million years or so of time. Between the standard Clarkforkian and Wasatchian faunal zones is an initial 'Wa-M' faunal zone of only five or so meters in thickness and something on the order of 20 thousand years of geological time. The Wa-M fauna includes the first

  16. Upper temperature tolerance of loach minnow under acute, chronic, and fluctuating thermal regimes

    USGS Publications Warehouse

    Widmer, A.M.; Carveth, C.J.; Bonar, Scott A.; Simms, J.R.

    2006-01-01

    We used four methods to estimate the upper lethal temperature of loach minnow Rhinichthys cobitis: the lethal thermal method (LTM), chronic lethal method (CLM), acclimated chronic exposure (ACE) method with static temperatures, and ACE method with diel temperature fluctuations. The upper lethal temperature of this species ranged between 32??C and 38??C, depending on the method and exposure time; however, temperatures as low as 28??C resulted in slowed growth compared with the control groups. In LTM trials, we increased temperatures 0.3??C/min and death occurred at 36.8 ?? 0.2??C (mean ?? SE) for fish (37-19 mm total length) acclimated to 30??C and at 36.4 ?? 0.07??C for fish acclimated to 25??C. In CLM trials, temperatures were increased more slowly (1??C/d), allowing fish to acclimate. Mean temperature at death was 33.4 ?? 0.1??C for fish 25-35 mm and 32.9 ?? 0.4??C for fish 45-50 mm. In the ACE experiment with static temperatures, we exposed fish for 30 d to four constant temperatures. No fish (20-40 mm) survived beyond 30 d at 32??C and the 30-d temperature lethal to 50% of the test animals was 30.6??C. Growth at static 28??C and 30??C was slower than growth at 25??C, suggesting that fish were stressed at sublethal temperatures. In ACE trials with diel temperature fluctuations of 4,6, and 10??C and a 32??C peak temperature, over 80% of fish (20-40 mm) survived 30 d. Although brief exposures to 32??C were not lethal, the growth of fish in the three fluctuating-temperature treatments was significantly less than the growth at the ambient temperature (25-29??C). To minimize thermal stress and buffer against temperature spikes, we recommend that loach minnow habitat be managed to avoid water temperatures above 28??C. ?? Copyright by the American Fisheries Society 2006.

  17. Lithospheric structure, composition, and thermal regime of the East European Craton: Implications for the subsidence of the Russian platform

    USGS Publications Warehouse

    Artemieva, I.M.

    2003-01-01

    A new mechanism for Paleozoic subsidence of the Russian, or East European, platform is suggested, since a model of lithosphere tilting during the Uralian subduction does not explain the post-Uralian sedimentation record. Alternatively, I propose that the Proterozoic and Paleozoic rifting (when a platform-scale Central Russia rift system and a set of Paleozoic rifts were formed) modified the structure and composition of cratonic lithosphere, and these tectono-magmatic events are responsible for the post-Uralian subsidence of the Russian platform. To support this hypothesis, (a) the thermal regime and the thickness of the lithosphere are analyzed, and (b) lithospheric density variations of non-thermal origin are calculated from free-board constraints. The results indicate that Proterozoic and Paleozoic rifting had different effects on the lithospheric structure and composition. (1) Proterozoic rifting is not reflected in the present thermal regime and did not cause significant lithosphere thinning (most of the Russian platform has lithospheric thickness of 150-180 km and the lithosphere of the NE Baltic Shield is 250-300 km thick). Paleozoic rifting resulted in pronounced lithospheric thinning (to 120-140 km) in the southern parts of the Russian platform. (2) Lithospheric density anomalies suggest that Proterozoic-Paleozoic rifting played an important role in the platform subsidence. The lithospheric mantle of the Archean-early Proterozoic part of the Baltic Shield is ??? 1.4 ?? 0.2% less dense than the typical Phanerozoic upper mantle. However, the density deficit in the subcrustal lithosphere of most of the Russian platform is only about (0.4-0.8) ?? 0.2% and decreases southwards to ???0%. Increased densities (likely associated with low depletion values) in the Russian platform suggest strong metasomatism of the cratonic lithosphere during rifting events, which led to its subsidence. It is proposed that only the lower part of the cratonic lithosphere was

  18. Soil thermal regime on ice-free areas in Livingston Island and James Ross Island, Antarctic Peninsula region

    NASA Astrophysics Data System (ADS)

    Hrbáček, Filip; Oliva, Marc; Láska, Kamil; Ruiz-Fernández, Jesús; Ángel de Pablo, Miguel; Vieira, Gonçalo; Ramos, Miguel; Nývlt, Daniel

    2016-04-01

    Permafrost and active layer are considered prominent components of the Cryosphere, which react very sensitively to small climate variations. The Antarctic Peninsula (AP) region is considered as one of the fastest warming regions on Earth, where mean annual air temperature locally increased more than 2.5°C over the last 60 years. Significant climate differences are found between the eastern and western sides of the AP. While mean annual air temperatures (MAAT) oscillate around -1 to -2 °C and precipitation reach 800 mm w.e. year-1 in the western AP, the MAAT in the eastern AP are below -6 °C and precipitation does not exceed 500 mm. These differences determine different permafrost thickness and spatial distribution in these two regions, as well as diverse patterns of active layer dynamics. With the purpose to better understand the factors controlling the soil thermal regime in maritime permafrost environments, we examine data from 2014 acquired from several sites in Livingston Island (western AP) and James Ross Island (eastern AP). The study sites show similar characteristics in terms of topography (slope < 7°) and altitude (50 to 100 m a.s.l.). Air temperature, soil thermal regime at 5 cm and 75 cm depth, as well as active layer thickness and its evolution were analysed. Mean air temperature over the study period varied between -2.6 to -2.7 °C on the different monitoring sites in Livingston Island, while in James Ross Island ranged from -7.0 to -7.9 °C. Mean soil temperature at 5 cm depth was slightly higher than air temperature in both areas: -0.7 to -1.3 °C in Livingston Island and -6.2 to -6.3 °C in James Ross Island; the same occurred for soil temperature at 75 cm: -0.4 to -0.7 °C in Livingston Island and -6.0 to -6.6 °C James Ross Island. Significantly lower values of mean daily amplitude of soil temperature at 5 cm depth and the freezing n-factor values observed during the freezing season on Livingston Island suggest a pronounced insulating effect

  19. Solitary Ring Pairs and Non-Thermal Regimes in Plasmas Connected with Black Holes*

    NASA Astrophysics Data System (ADS)

    Coppi, Bruno

    2011-10-01

    The two-dimensional plasma and field configurations that can be associated with compact objects such as black holes are described, (in the limit where assuming a scalar pressure can be justified), by two characteristic non-linear equations: i) one that connects the plasma density profile to that of the relevant magnetic surfaces and is called the ``master equation'': ii) the other, the ``vertical equilibrium equation,'' connects the plasma pressure to the density and the magnetic surfaces and is closely related to the G-S equation for magnetically confined laboratory plasmas. Two kinds of solutions are found that consist of: i) a periodic sequence of plasma rings; ii) solitary pairs of rings. Experimental observations support the presence of rings around collapsed objects. Tridimensional configuration are found in the linear approximation as consisting of trailing spirals. Observations of High Frequency Quasi-Periodic oscillations implies that they originate from 3-dimentional structures. The existing theory is extended to involve non-thermal particle distributions in order to comply with relevant experimental observations. *Sponsored in part by the U.S. DOE.

  20. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae).

    PubMed

    Falfushynska, H; Gnatyshyna, L; Yurchak, I; Ivanina, A; Stoliar, O; Sokolova, I

    2014-12-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25°C and 30°C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30°C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25°C and 30°C and in mussels from N site at 30°C. The mussels from N site also demonstrated better survival at elevated temperature (30°C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30°C) is harmful to mussels from all populations indicating limit to this induced

  1. Cyclic CO2 emissions during the high temperature pulse of fluctuating thermal regime in eye-pigmented pupae of Megachile rotundata

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Megachile rotundata, the primary pollinator used in alfalfa seed production, may need to be exposed to low-temperature storage to slow the bees’ development to better match spring emergence with the alfalfa bloom. It has been demonstrated that using a fluctuating thermal regime (FTR) improves the be...

  2. Phonon-engineered thermal transport in Si wires with constant and periodically modulated cross-sections: A crossover between nano- and microscale regimes

    NASA Astrophysics Data System (ADS)

    Cocemasov, A. I.; Nika, D. L.; Fomin, V. M.; Grimm, D.; Schmidt, O. G.

    2015-07-01

    The transition between nanoscale and microscale thermal transport regime at room temperature in silicon wires with constant and periodically modulated cross-section is theoretically investigated. Extrapolating the calculated thermal conductivity from the nano- to micrometer range, we find the characteristic dimensions of the wires where a crossover between nanoscale and microscale thermal transport occurs. This crossover is observed in both generic (smooth) and cross-section-modulated wires. In case of smooth silicon wires, we reveal a strong dependence of the crossing point position on the boundary roughness. For silicon wires with weak boundary roughness, the crossover occurs at cross-sections ˜60 nm × 300 nm, while for very rough boundaries it occurs at cross-sections ˜150 nm × 750 nm. In case of the periodically modulated wires, the crossover between nano- and microscale regimes occurs at typical cross-sections ˜120 nm × 120 nm of the narrow segment, and it is almost independent of boundary roughness. A strong distinction from the case of smooth wires is attributed (i) to the different trends at the nanometer scale, wherefrom the extrapolation was performed, and (ii) to the different phonon-boundary scattering due to the specific geometry. For modulated silicon wires, the influence of modulation thickness, modulation length, and cross-sectional area on the phonon thermal conductivity at the room temperature is analyzed. A possibility of thermal transport engineering in cross-section-modulated wires by resizing them is revealed in both nano- and microscale regimes. The presented results pave the way towards a better understanding of thermal transport reduction in Si nanowires with engineered diameter modulations and shed light on the crossover between nano- and microscale regimes of thermal transport.

  3. THERMAL ESCAPE IN THE HYDRODYNAMIC REGIME: RECONSIDERATION OF PARKER's ISENTROPIC THEORY BASED ON RESULTS OF KINETIC SIMULATIONS

    SciTech Connect

    Volkov, Alexey N.; Johnson, Robert E.

    2013-03-10

    The one-dimensional steady-state problem of thermal escape from a single-component atmosphere of mon- and diatomic gases is studied in the hydrodynamic (blow-off) regime using the direct simulation Monte Carlo method for an evaporative-type condition at the lower boundary. The simulations are performed for various depths into an atmosphere, indicated by a Knudsen number, Kn{sub 0}, equal to the ratio of the mean free path of molecules to the radial position of the source surface, ranging from 10 to 10{sup -5}, and for the range of the source Jeans parameter, {lambda}{sub 0}, equal to the ratio of gravitational and thermal energies, specific to blow-off. The results of kinetic simulations are compared with the isentropic model (IM) and the Navier-Stokes model. It is shown that the IM can be simplified if formulated in terms of the local Mach number and Jeans parameter. The simulations predict that at Kn{sub 0} < {approx} 10{sup -3} the flow includes a near-surface non-equilibrium Knudsen layer, a zone where the flow can be well approximated by the IM, and a rarefied far field. The corresponding IM solutions, however, only approach Parker's critical solution as {lambda}{sub 0} approaches the upper limit for blow-off. The IM alone is not capable for predicting the flow and requires boundary conditions at the top of the Knudsen layer. For small Kn{sub 0}, the scaled escape rate and energy loss rate are found to be independent of {lambda}{sub 0}. The simulation results can be scaled to any single-component atmosphere exhibiting blow-off if the external heating above the lower boundary is negligible, in particular, to sublimation-driven atmospheres of Kuiper belt objects.

  4. Testing the reference Moon model in respect of the thermal regime and chemical composition of the mantle: Thermodynamics versus seismology

    NASA Astrophysics Data System (ADS)

    Kuskov, O. L.; Kronrod, V. A.; Kronrod, E. V.

    2016-05-01

    The VPREMOON seismic reference Moon model (Garcia et al., 2011) has been tested with respect to the thermal regime and chemical composition of the mantle. Based on a self-consistent thermodynamic approach and petrological models of the lunar mantle covering a wide range of concentrations of CaO, Al2O3, and FeO, we convert the P- and S-wave velocity profiles to the temperature-depth profiles. The solution procedure relies on the method of the Gibbs free energy minimization and the equations of state for the mantle material which take into account the effects of phase transformations, anharmonicity, and anelasticity. We find that regardless of the chemical composition, the positive P- and S-wave velocity gradient in the lunar mantle leads to a negative temperature gradient, which has no physical basis. For adequate mantle temperatures, the P- and S-wave velocities should remain almost constant or slightly decrease with depth (especially V S ) as a result of the effects of the temperature, which grows faster than pressure. These findings underscore the importance of the relationship of the thermodynamics and physics of minerals with seismology.

  5. Survival, development, and growth of fall Chinook salmon embryos, alevin, and fry exposed to variable thermal and dissolved oxygen regimes

    SciTech Connect

    Geist, David R.; Abernethy, Cary S.; Hand, Kristine D.; Cullinan, Valerie I.; Chandler, James A.; Groves, Philip

    2006-11-15

    Some fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Snake River downstream of Hells Canyon Dam at temperatures that exceed 13?C and at intergravel dissolved oxygen concentrations that are less than 8 mg O2/L. Although water temperature declines and dissolved oxygen increases soon after spawning, these temperature and dissolved oxygen levels do not meet the water quality standards established by the states of Oregon and Idaho for salmonid spawning. Our objective was to determine if temperatures from 13 to 17 C and dissolved oxygen levels from 4 to greater than 8 mg O2/L during the first 40 days of incubation followed by declining temperature and rising dissolved oxygen affected survival, development, and growth of Snake River fall Chinook salmon embryos, alevins, and fry. During the first 40 days of incubation, temperatures were adjusted downward approximately 0.2 C/day and oxygen was increased in increments of 2 mg O2/L to mimic the thermal and oxygen regime of the Snake River where these fish spawn. At 40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal and dissolved oxygen profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures equal to or greater than 17?C, and a rapid decline in survival occurred between 16.5 C and 17 C, with no significant difference in survival at temperatures less than or equal to 16.5 C. Initial dissolved oxygen levels as low as 4 mg O2/L over a range of initial temperatures from 15 to 16.5 C did not affect embryo survival to emergence. There were no significant differences across the range of initial temperature exposures for alevin and fry size at hatch and emergence. The number of days from fertilization to eyed egg, hatch, and emergence was highly related to temperature and dissolved oxygen; it took from 6 to 10 days longer to reach hatch at 4 mg O2/L than at saturation and up to

  6. An epidemic model for the interactions between thermal regime of rivers and transmission of Proliferative Kidney Disease in salmonid fish

    NASA Astrophysics Data System (ADS)

    Carraro, Luca; Bertuzzo, Enrico; Mari, Lorenzo; Gatto, Marino; Strepparava, Nicole; Hartikainen, Hanna; Rinaldo, Andrea

    2015-04-01

    Proliferative kidney disease (PKD) affects salmonid populations in European and North-American rivers. It is caused by the endoparasitic myxozoan Tetracapsuloides bryosalmonae, which exploits freshwater bryozoans (Fredericella sultana) and salmonids as primary and secondary hosts, respectively. Incidence and mortality, which can reach up to 90-100%, are known to be strongly related to water temperature. PKD has been present in brown trout population for a long time but has recently increased rapidly in incidence and severity causing a decline in fish catches in many countries. In addition, environmental changes are feared to cause PKD outbreaks at higher latitude and altitude regions as warmer temperatures promote disease development. This calls for a better comprehension of the interactions between disease dynamics and the thermal regime of rivers, in order to possibly devise strategies for disease management. In this perspective, a spatially explicit model of PKD epidemiology in riverine host metacommunities is proposed. The model aims at summarizing the knowledge on the modes of transmission of the disease and the life-cycle of the parasite, making the connection between temperature and epidemiological parameters explicit. The model accounts for both local population and disease dynamics of bryozoans and fish and hydrodynamic dispersion of the parasite spores and hosts along the river network. The model is time-hybrid, coupling inter-seasonal and intra-seasonal dynamics, the former being described in a continuous time domain, the latter seen as time steps of a discrete time domain. In order to test the model, a case study is conducted in river Wigger (Cantons of Aargau and Lucerne, Switzerland), where data about water temperature, brown trout and bryozoan populations and PKD prevalence are being collected.

  7. Geothermal measurements in the northern Red Sea: Implications for lithospheric thermal structure and mode of extension during continental rifting

    SciTech Connect

    Martinez, F.; Cochran, J.R. )

    1989-09-10

    The northern Red Sea is a continental rift in the process of transition from continental to oceanic rifting. We present 191 new heat flow measurements from the northern Red Sea forming three traverses across the water covered portion of the rift. The heat flow across the rift systematically increases from values of about 125 mW/m{sup 2} seaward of the coasts to average values greater than 250 mW/m{sup 2} in the axial depression. The heat flow measurements are evaluated for environmental disturbances. These are found to be generally small. The largest estimated disturbance results from the relief of the seafloor and of the top of a subbottom evaporite layer. The relief on these surfaces can account for the 20% point to point scatter typically observed in the heat flow measurements. Limits are placed on systematic disturbances to the heat flow pattern across the rift. The estimated largest systematic disturbance results from sediment blanketing which may cause a reduction in the heat flow on the order of 10%.

  8. The Influences of Land Surface Properties on Soil Thermal Regimes in the Low Arctic of Northwestern Siberia

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Frost, G. V., Jr.; Matyshak, G. V.; Walker, D. A.; Meakem, V. M.

    2014-12-01

    Understanding the feedbacks among climate, permafrost, and vegetation is crucial for assessments of arctic ecosystem vulnerability and response to climate change, and for development of sustainable engineering and management methods associated with infrastructure. Vegetation, snow cover, and near-surface soil organic layers are key determinants in regulating the energy exchange between the atmosphere and the deeper soils. Here we present high-temporal resolution soil thermal regime data over annual time extents for multiple sites at two locations in the Low Arctic of northwestern Siberia. At a location near Nadym, Russia, we measured soil temperatures at various depths in the soil profile (down to 60 cm) at three sites: 1) a boreal forest stand with lichen understory and a shallow organic layer (8 cm), 2) a young, cryoturbated Sphagnum peatland with soil organic layers to 40 cm depth, and 3) an old Sphagnum peatland with deep organic soil horizons (58+ cm). At a location near Kharp, Russia, we measured soil temperatures at 5 and 20 cm depth for sites along a chronosequence of tall alder shrub expansion, from short-statured tundra to mature and old alder stands, with deeper organic layers. The deeper snow accumulation at the Nadym forest site kept winter soil temperatures dramatically warmer than the peatland soils, up to 8 °C difference, but the shading of the forest tended to cool the surface during the summer. The overall effect of the forest was cooler summer soils in the near-surface layers, yet warmer summer soils at the deeper layers (20-60 cm). The forest location had substantially greater thawing degree days at depth (20-60 cm), compared to the Sphagnum peatlands. At the Kharp site, mature alder shrub stands cooled summer soil temperatures relative to shorter tundra by up to 8 °C (at 20 cm depth), yet warmed winter soils by greater than 10 °C. Mature and old shrubland locations had reduced thawing degree days at 20 cm depth relative to short

  9. Thermal regime and potential bedrock weathering in alpine rockwalls of Austria: Results from eight years of monitoring (2006-2014)

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas; Wecht, Matthias

    2015-04-01

    Bedrock temperature at sites with a minor winter snow cover gives a good indication for the effects of air temperature anomalies on ground thermal conditions as well as for the intensity of near-surface physical weathering in bedrock. In this study we present results from an ongoing bedrock temperature monitoring program initiated in 2006. Within the framework of this program nine surface boreholes in rockwalls with different slope orientations and two additional boreholes at flat bedrock sites were drilled between August and September 2006 and subsequently instrumented. The altogether eleven rock temperature sites (RTS) are located in the alpine periglacial zone of the Austrian Alps at latitude 46°55' to 47°22' and longitude 12°44' to 14°41'. All RTS have been installed in metamorphic rock (5 x mica schist; 6 x gneiss) at elevations between 1960 and 2725 m asl (mean 2491 m asl.). Three temperature sensors (PT1000) have been inserted at each borehole site at vertical depths of 3, 10 and 30-40 cm. At each RTS the three sensors are connected to a 3-channel miniature temperature datalogger (MTD) manufactured by GeoPrecision, Germany. Our analysis focussed on (a) the variation of mean and extreme daily temperatures at the rock surface and at depth, (b) the variation of the daily temperature range, (c) the number of freeze-thaw-cycles (FTC) and (d) effective freeze-thaw cycles for frost shattering (eFTC), (e) the duration and intensity of freeze-thaw-cycles (DI-FTC), (f) the number of hours and days within the so-called frost-cracking-window (FCW), and effects of (g) aspect and (h) snow cover on the thermal regimes in the bedrock. Results show for instance that the number of FTC and eFTC varied substantially during the observation period at all eleven RTS and at all sensor depths. However, this variation differs from site to site related to snow cover condition, elevation and aspect. For instance, at one lower-elevated (2255 m asl) north exposed RTS the number of

  10. The Mw 8.8, 1906 Colombia-Ecuador Subduction Earthquake: Seismic Structure and Thermal Regime of the Plate Boundary.

    NASA Astrophysics Data System (ADS)

    Collot, J.; Marcaillou, B.; Agudelo, W.; Ribodetti, A.; D'Acremont, E.

    2007-05-01

    subduction earthquakes, which occurred beneath the subsiding fore-arc basin. North of latitude 2°30'N, although the trench fill is thinner (~2 km), the Colombian accretionary wedge has developed and reaches 30 km in width at 3°30'N. The zones where each of the 1942, 1958 and 1979 earthquake rupture zones meet with the adjacent rupture zone have been shown to correlate with along strike changes in the fore-arc tectonic regime from uplift (1942) to subsidence (1958), and oblique compression (1979), and with transverse crustal faults that segment the margin. In addition, a fault-bounded outer basement high and a major splay fault that branches upward from the plate interface may control the seaward limit of the 1958 earthquake rupture zone. Thermal modeling, matching bottom simulating reflector (BSR)-derived heat flow, and heat flow measurements, suggests that the 1958 and 1979 earthquakes nucleated within a central to shallow portion of the seismogenic zone, at temperatures estimated to be ~160°C and that the updip limit of the seismogenic zone is controlled by low temperature (60-70°C) processes, with the exception of the 1958 event, where the updip limit is more likely related to prominent structural features fronting the margin.

  11. The Paleocene-Eocene Thermal Maximum record in the organic matter of the Claret and Tendruy continental sections (South-central Pyrenees, Lleida, Spain)

    NASA Astrophysics Data System (ADS)

    Domingo, Laura; López-Martínez, Nieves; Leng, Melanie J.; Grimes, Stephen T.

    2009-05-01

    The Carbon Isotope Excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been detected for the first time in the total organic carbon (TOC) contained within the continental sediments of the Tremp Formation (South Central Pyrenees, Lleida, Spain). The δ13C TOC magnitude of the CIE is ~ 4.3‰ in the Claret section and ~ 3.0‰ in the Tendruy section with minimum values of - 27.6‰ and - 26.7‰, respectively. Previous studies have detected the CIE in the South Central Pyrenees in both marine carbonates and within continental soil carbonate nodules. These studies have located the onset of the CIE either above or within the Claret Conglomerate, interpreted as a megafan produced by a profound change in the precipitation regimen at the beginning of the PETM. Our higher resolution δ13C TOC study in the Claret and Tendruy sections places the onset of the CIE below the base of the Claret Conglomerate and therefore suggests a 4 to 9 kyr time lag between the onset of the CIE and an increase in intense seasonal precipitation rates. Furthermore, this study suggests that the CIE took place ~ 30-55 kyr after the deposition of important late Cernaysian Tremp mammalian sites (Claret-4, Tendruy-V, Tendruy and Palau) which contain the youngest known occurrence of endemic Paleocene mammalian taxa in Europe before the Mammalian Dispersal Event (MDE, migration of new mammal groups, such as perissodactyls, artiodactyls, primates, marsupials, carnivores, creodonts and rodents). The first immigrant mammals in Europe are recorded at Dormaal (Belgium) above a hiatus, the base of which has been dated to around the start of the CIE. Our data indicate that the MDE might have in fact occurred in Europe within a time interval of about 67 kyr around the CIE onset.

  12. Partial melting of an ancient sub-continental lithospheric mantle in the early Paleozoic intracontinental regime and its contribution to petrogenesis of the coeval peraluminous granites in South China

    NASA Astrophysics Data System (ADS)

    Zhong, Yufang; Wang, Lianxun; Zhao, Junhong; Liu, Lei; Ma, Changqian; Zheng, Jianping; Zhang, Zejun; Luo, Biji

    2016-11-01

    The appinite-granite association has been found in various tectonic regimes related to recent subduction, arc-continent or continent-continent collision and post-collision (orogen), and appinites generally originate from recently subduction-modified lithospheric mantle. We conducted a study on a rarely reported appinite-granite association formed in an intracontinental regime, the Zhangjiafang-Qinglongshan complex (ZQC), in which the appinites were derived from an ancient sub-continental lithospheric mantle (SCLM). The ZQC is located in the western Wugongshan domain, and consists of basaltic to intermediate appinites and granitoids. Ten dated samples (including massive and gneissoid granitoids, hornblende gabbro, and diorite) give zircon 206Pb/238U ages ranging from 444 ± 3 Ma to 452 ± 4 Ma, indicating that these various lithologies were emplaced synchronously. The basaltic appinites show radiogenic 87Sr/86Sri (0.71016-0.71431) and negative εNd(t) (- 6.1 to - 8.9) and zircon εHf(t) (- 4.2 to - 7.5) values. Combined with regional geological background, an origin from the Neoproterozoic metasomatised SCLM can be inferred for the appinites in the Wugongshan domain. The granitoids are peraluminous and almost high-K calc-alkaline to shoshonitic. They exhibit a wide range of isotopic compositions (87Sr/86Sri = 0.70828-0.71857, εNd(t) = - 6.2 to - 10.5, zircon εHf(t) = - 9.5 to - 26.6). Some of the granitoids display the most evolved Sr-Nd isotopic signatures among all the studied lithologies, which are consistent with those of the middle to upper crust, suggesting a pure crustal origin. Other granitoids show relatively mafic composition and less evolved isotopic signature. The intermediate appinites have intermediate chemical compositions between those of the basaltic appinites and granitoids, and similar Sr-Nd isotopic compositions to those of the basaltic appinites that have relatively evolved composition and isotopic signature. The petrographical and the

  13. Thermal history, exhumation and long-term landscape evolution of the South Atlantic passive continental margin, Kaoko Belt, NW Namibia

    NASA Astrophysics Data System (ADS)

    Menges, Daniel; Glasmacher, Ulrich A.; Hackspacher, Peter C.; Schneider, Gabriele; Zentner, Henning; Karl, Markus

    2014-05-01

    After the Damara Orogeny at the end of the Neoproterozoic the Kaoko Belt in northwestern Namibia was affected by deep erosion of the Damara Sequence, followed by the depositon of the Karoo Supergroup from Permo-Carboniferous to Early Cretaceous. The lithostratigraphic units consist of Late Proterozoic to Cambrian metamorphosed rocks and intrusive complexes of the Damara Group, with ages of 534 (7) Ma to 481 (25) Ma (Miller 1983), that are unconformably overlain by terrestrial deposits of the Karoo Supergroup (Stollhofen 1999), comprising two flood basalt events: the Karoo flood basalts, at 183 (1) Ma (Duncan et al. 1997), and the Early Cretaceous Paraná-Etendeka flood basalts, at 132 (1) Ma (Renne et al. 1996). The latter marking the rift stage of the opening of the South Atlantic. The "passive" continental margin along the Kaoko Belt in northern Namibia is a perfect location to quantify exhumation and uplift rates, model the long-term landscape evolution and provide information about the major processes controlling the landscape evolution in this region. The poster/talk will present thermochronological data, t-T-models and exhumation rates for the Kaoko belt, NW Namibia. References Miller, R. M., 1983. Evolution of the Damara Orogen, Vol. 11, Geol. Soc., South Africa Spec. Pub.. Renne, P.R., Glen, J.M., Milner, S.C., Duncan, A.R., 1996. Age of Etendeka flood volcanism and associated intrusions in southwestern Africa, Geology 24 (7): 659- 662. Duncan, R., Hooper, P., Rehacek, J., March, J. and Duncan, A., 1997. The timing and duration of the Karoo igneous event, southern Gondwana, J. Geophys. Res. 102: 18127-18138. Stollhofen, H., 1999. Karoo Synrift-Sedimentation und ihre tektonische Kontrolle am entstehenden Kontinentalrand Namibias, Z.dt.geol.Ges. 149: 519-632.

  14. Influence of Earth crust composition on continental collision style in Precambrian conditions: Results of supercomputer modelling

    NASA Astrophysics Data System (ADS)

    Zavyalov, Sergey; Zakharov, Vladimir

    2016-04-01

    A number of issues concerning Precambrian geodynamics still remain unsolved because of uncertainity of many physical (thermal regime, lithosphere thickness, crust thickness, etc.) and chemical (mantle composition, crust composition) parameters, which differed considerably comparing to the present day values. In this work, we show results of numerical supercomputations based on petrological and thermomechanical 2D model, which simulates the process of collision between two continental plates, each 80-160 km thick, with various convergence rates ranging from 5 to 15 cm/year. In the model, the upper mantle temperature is 150-200 ⁰C higher than the modern value, while the continental crust radiogenic heat production is higher than the present value by the factor of 1.5. These settings correspond to Archean conditions. The present study investigates the dependence of collision style on various continental crust parameters, especially on crust composition. The 3 following archetypal settings of continental crust composition are examined: 1) completely felsic continental crust; 2) basic lower crust and felsic upper crust; 3) basic upper crust and felsic lower crust (hereinafter referred to as inverted crust). Modeling results show that collision with completely felsic crust is unlikely. In the case of basic lower crust, a continental subduction and subsequent continental rocks exhumation can take place. Therefore, formation of ultra-high pressure metamorphic rocks is possible. Continental subduction also occurs in the case of inverted continental crust. However, in the latter case, the exhumation of felsic rocks is blocked by upper basic layer and their subsequent interaction depends on their volume ratio. Thus, if the total inverted crust thickness is about 15 km and the thicknesses of the two layers are equal, felsic rocks cannot be exhumed. If the total thickness is 30 to 40 km and that of the felsic layer is 20 to 25 km, it breaks through the basic layer leading to

  15. Growth of the continental crust: A planetary-mantle perspective

    NASA Technical Reports Server (NTRS)

    Warren, Paul H.

    1988-01-01

    The lack of earth rocks older than about 3.8 Ga is frequently interpreted as evidence that the earth formed little or no subduction-resistant continental crust during the first 700 My of its history. Such models obviously imply that the pre-3.8 Ga earth was covered entirely or almost entirely by smoothly subducting oceanic crust. On the other hand, the thermal regime of the early earth probably tended to cause the oceanic crust at this time to be comparatively thin and comparatively mafic. The present earth is covered by about 50 percent oceanic crust, averaging about 7 km in thickness, and 41 percent continental crust, averaging roughly 40 km in thickness. Thus continentless-early-earth models would seem to imply a total mass of crust less than 1/3 that of the present day earth. Possible explanations are examined.

  16. Heating-frequency-dependent thermal conductivity: An analytical solution from diffusive to ballistic regime and its relevance to phonon scattering measurements

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Dames, Chris

    2015-04-01

    The heating-frequency dependence of the apparent thermal conductivity in a semi-infinite body with periodic planar surface heating is explained by an analytical solution to the Boltzmann transport equation. This solution is obtained using a two-flux model and gray mean free time approximation and verified numerically with a lattice Boltzmann method and numerical results from the literature. Extending the gray solution to the nongray regime leads to an integral transform and accumulation-function representation of the phonon scattering spectrum, where the natural variable is mean free time rather than mean free path, as often used in previous work. The derivation leads to an approximate cutoff conduction similar in spirit to that of Koh and Cahill [Phys. Rev. B 76, 075207 (2007), 10.1103/PhysRevB.76.075207] except that the most appropriate criterion involves the heater frequency rather than thermal diffusion length. The nongray calculations are consistent with Koh and Cahill's experimental observation that the apparent thermal conductivity shows a stronger heater-frequency dependence in a SiGe alloy than in natural Si. Finally these results are demonstrated using a virtual experiment, which fits the phase lag between surface temperature and heat flux to obtain the apparent thermal conductivity and accumulation function.

  17. Review of biomaterial thermal property measurements in the cryogenic regime and their use for prediction of equilibrium and non-equilibrium freezing applications in cryobiology.

    PubMed

    Choi, Jeunghwan; Bischof, John C

    2010-02-01

    It is well accepted in cryobiology that the temperature history and cooling rates experienced in biomaterials during freezing procedures correlate strongly with biological outcome. Therefore, heat transfer measurement and prediction in the cryogenic regime is central to the field. Although direct measurement of temperature history (i.e. heat transfer) can be performed, accuracy is usually achieved only for local measurements within a given system and cannot be readily generalized to another system without the aid of predictive models. The accuracy of these models rely upon thermal properties which are known to be highly dependent on temperature, and in the case of significant cryoprotectant loading, also on crystallized fraction. In this work, we review the available thermal properties of biomaterials in the cryogenic regime. The review shows a lack of properties for many biomaterials in the subzero temperature domain, and especially for systems with cryoprotective agents. Unfortunately, use of values from the limited data available (usually only down to -40 degrees C) lead to an underestimation of thermal property change (i.e. conductivity rise and specific heat drop due to ice crystallization) with lower temperatures. Conversely, use of surrogate values based solely on ice thermal properties lead to an overestimation of thermal property change for most biomaterials. Additionally, recent work extending the range of available thermal properties to -150 degrees C has shown that the thermal conductivity will drop in both PBS and tissue (liver) due to amorphous/glassy phases (versus crystalline) of biomaterials with the addition of cryoprotective additives such as glycerol. Thus, we investigated the implications of using approximated or constant property values versus measured temperature-dependent values for predicting temperature history during freezing in PBS (phosphate-buffered saline) and porcine liver with and without cryoprotectants (glycerol). Using measured

  18. Theoretical regime diagrams for thermally driven flows in a beta-plane channel in the presence of variable gravity

    NASA Technical Reports Server (NTRS)

    Geisler, J. E.; Fowlis, W. W.

    1980-01-01

    The effect of a power law gravity field on baroclinic instability is examined, with a focus on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by a dielectric force. Growth rates are obtained of unstable normal modes as a function of parameters of the problem by solving a second order differential equation numerically. It is concluded that over the range of parameter space explored, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as parameter.

  19. Thermal form factor approach to the ground-state correlation functions of the XXZ chain in the antiferromagnetic massive regime

    NASA Astrophysics Data System (ADS)

    Dugave, Maxime; Göhmann, Frank; Kozlowski, Karol K.; Suzuki, Junji

    2016-09-01

    We use the form factors of the quantum transfer matrix in the zero-temperature limit in order to study the two-point ground-state correlation functions of the XXZ chain in the antiferromagnetic massive regime. We obtain novel form factor series representations of the correlation functions which differ from those derived either from the q-vertex-operator approach or from the algebraic Bethe Ansatz approach to the usual transfer matrix. We advocate that our novel representations are numerically more efficient and allow for a straightforward calculation of the large-distance asymptotic behaviour of the two-point functions. Keeping control over the temperature corrections to the two-point functions we see that these are of order {T}∞ in the whole antiferromagnetic massive regime. The isotropic limit of our result yields a novel form factor series representation for the two-point correlation functions of the XXX chain at zero magnetic field. Dedicated to the memory of Petr Petrovich Kulish.

  20. Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

    NASA Astrophysics Data System (ADS)

    Maksimov, Vyacheslav I.; Nagornova, Tatiana A.; Glazyrin, Viktor P.; Shestakov, Igor A.

    2016-02-01

    Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG). The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables "vorticity - the stream function". Are obtained distributions of the hydrodynamic parameters and temperatures, that characterize basic regularities of the processes. The special features of the formation of circulation flows are isolated and the analysis of the temperature distribution in the solution region is carried out. Is shown the influence of geometric characteristics and intensity of heat exchange on the outer boundaries of reservoir on the temperature field in the LNG storage.

  1. Combining Bioenergetic Responses of Fish to Thermal Regimes and Productivity in Reservoirs: Implications for Conservation and Re-Introduction of Anadromous Salmonids

    NASA Astrophysics Data System (ADS)

    Beauchamp, D.

    2014-12-01

    Temperature, food availability, and predation risk form vertical gradients determining growth and survival for fish in lakes and reservoirs. These gradients change on inter-annual, seasonal, and diel temporal scales and are strongly influenced by climatic variability, conflicting water demands and management. Temperatures associated with optimal growth and energy loss vary both among life stages and species of fish, but the quantity and quality of available food resources can significantly alter these thermal responses. Greater understanding of how water management affects the timing, magnitude, and duration of thermal stratification, and how key species and their supporting aquatic resources respond can improve strategies for development and operation of water storage facilities within the context of localized environmental and ecological constraints. An emerging trend for coldwater reservoirs in the Pacific Northwest has been to re-introduce anadromous salmon above historically impassable dams. Thermal regimes and the existing ecological communities in the reservoirs and tributary habitats above these dams will determine the seasonal importance of lotic and lentic habitats for rearing or migration corridors. The feasibility of reservoir rearing and migration can be evaluated by combining mass- and species-specific thermal growth response curves with temporal dynamics in the vertical and longitudinal thermal structure of reservoirs and associated distribution of food resources (primarily zooplankton). The value of reservoirs as rearing habitats or migration corridors could be compared with coincident tributary conditions to predict the likely temporal-spatial distribution of optimal conditions for growth and survival of different species or life stages of salmonids within the watershed and how these conditions might change under different climatic or water management scenarios.

  2. Impacts of projected mid-century temperatures on thermal regimes for select specialty and fieldcrops common to the southwestern U.S.

    NASA Astrophysics Data System (ADS)

    Elias, E.; Lopez-Brody, N.; Dialesandro, J.; Steele, C. M.; Rango, A.

    2015-12-01

    The impacts of projected temperature increases in agricultural ecosystems are complex, varyingby region, cropping system, crop growth stage and humidity. We analyze the impacts of mid-century temperature increases on crops grown in five southwestern states: Arizona, California,New Mexico, Nevada and Utah. Here we present a spatial impact assessment of commonsouthwestern specialty (grapes, almonds and tomatoes) and field (alfalfa, cotton and corn)crops. This analysis includes three main components: development of empirical temperaturethresholds for each crop, classification of predicted future climate conditions according to thesethresholds, and mapping the probable impacts of these climatic changes on each crop. We use30m spatial resolution 2012 crop distribution and seasonal minimum and maximumtemperature normals (1970 to 2000) to define the current thermal envelopes for each crop.These represent the temperature range for each season where 95% of each crop is presentlygrown. Seasonal period change analysis of mid-century temperatures changes downscaled from20 CMIP5 models (RCP8.5) estimate future temperatures. Change detection maps representareas predicted to become more or less suitable, or remain unchanged. Based upon mid-centurytemperature changes, total regional suitable area declined for all crops except cotton, whichincreased by 20%. For each crop there are locations which change to and from optimal thermalenvelope conditions. More than 80% of the acres currently growing tomatoes and almonds willshift outside the present 95% thermal range. Fewer acres currently growing alfalfa (14%) andcotton (20%) will shift outside the present 95% thermal range by midcentury. Crops outsidepresent thermal envelopes by midcentury may adapt, possibly aided by adaptation technologiessuch as misters or shade structures, to the new temperature regime or growers may elect togrow alternate crops better suited to future thermal envelopes.

  3. Simulating the thermal regime and thaw processes of ice-rich permafrost ground with the land-surface model CryoGrid 3

    NASA Astrophysics Data System (ADS)

    Westermann, S.; Langer, M.; Boike, J.; Heikenfeld, M.; Peter, M.; Etzelmüller, B.; Krinner, G.

    2016-02-01

    Thawing of permafrost in a warming climate is governed by a complex interplay of different processes of which only conductive heat transfer is taken into account in most model studies. However, observations in many permafrost landscapes demonstrate that lateral and vertical movement of water can have a pronounced influence on the thaw trajectories, creating distinct landforms, such as thermokarst ponds and lakes, even in areas where permafrost is otherwise thermally stable. Novel process parameterizations are required to include such phenomena in future projections of permafrost thaw and subsequent climatic-triggered feedbacks. In this study, we present a new land-surface scheme designed for permafrost applications, CryoGrid 3, which constitutes a flexible platform to explore new parameterizations for a range of permafrost processes. We document the model physics and employed parameterizations for the basis module CryoGrid 3, and compare model results with in situ observations of surface energy balance, surface temperatures, and ground thermal regime from the Samoylov permafrost observatory in NE Siberia. The comparison suggests that CryoGrid 3 can not only model the evolution of the ground thermal regime in the last decade, but also consistently reproduce the chain of energy transfer processes from the atmosphere to the ground. In addition, we demonstrate a simple 1-D parameterization for thaw processes in permafrost areas rich in ground ice, which can phenomenologically reproduce both formation of thermokarst ponds and subsidence of the ground following thawing of ice-rich subsurface layers. Long-term simulation from 1901 to 2100 driven by reanalysis data and climate model output demonstrate that the hydrological regime can both accelerate and delay permafrost thawing. If meltwater from thawed ice-rich layers can drain, the ground subsides, as well as the formation of a talik, are delayed. If the meltwater pools at the surface, a pond is formed that enhances heat

  4. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city

    NASA Astrophysics Data System (ADS)

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas.

  5. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city.

    PubMed

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas. PMID:26349476

  6. Thermal comfort in Quebec City, Canada: sensitivity analysis of the UTCI and other popular thermal comfort indices in a mid-latitude continental city.

    PubMed

    Provençal, Simon; Bergeron, Onil; Leduc, Richard; Barrette, Nathalie

    2016-04-01

    The newly developed Universal Thermal Climate Index (UTCI), along with the physiological equivalent temperature (PET), the humidex (HX) and the wind chill index (WC), was calculated in Quebec City, Canada, a city with a strong seasonal climatic variability, over a 1-year period. The objective of this study is twofold: evaluate the operational benefits of implementing the UTCI for a climate monitoring program of public comfort and health awareness as opposed to relying on traditional and simple indices, and determine whether thermal comfort monitoring specific to dense urban neighborhoods is necessary to adequately fulfill the goals of the program. In order to do so, an analysis is performed to evaluate each of these indices' sensitivity to the meteorological variables that regulate them in different environments. Overall, the UTCI was found to be slightly more sensitive to mean radiant temperature, moderately more sensitive to humidity and much more sensitive to wind speed than the PET. This dynamic changed slightly depending on the environment and the season. In hot weather, the PET was found to be more sensitive to mean radiant temperature and therefore reached high values that could potentially be hazardous more frequently than the UTCI and the HX. In turn, the UTCI's stronger sensitivity to wind speed makes it a superior index to identify potentially hazardous weather in winter compared to the PET and the WC. Adopting the UTCI broadly would be an improvement over the traditionally popular HX and WC indices. The urban environment produced favorable conditions to sustain heat stress conditions, where the indices reached high values more frequently there than in suburban locations, which advocates for weather monitoring specific to denser urban areas.

  7. Structural controls, alteration, permeability and thermal regime of Dixie Valley from new-generation MT/galvanic array profiling

    SciTech Connect

    Philip E. Wannamaker

    2007-11-30

    State-of-the-art MT array measurements in contiguous bipole deployments across the Dixie Valley thermal area have been integrated with regional MT transect data and other evidence to address several basic geothermal goals. These include 1), resolve a fundamental structural ambiguity at the Dixie Valley thermal area (single rangefront fault versus shallower, stepped pediment; 2), delineate fault zones which have experienced fluid flux as indicated by low resistivity; 3), infer ultimate heat and fluid sources for the thermal area; and 4), from a generic technique standpoint, investigate the capability of well-sampled electrical data for resolving subsurface structure. Three dense lines cross the Senator Fumaroles area, the Cottonwood Creek and main producing area, and the low-permeability region through the section 10-15 area, and have stand-alone MT soundings appended at one or both ends for local background control. Regularized 2-D inversion implies that shallow pediment basement rocks extend for a considerable distance (1-2 km) southeastward from the topographic scarp of the Stillwater Range under all three dense profiles, but especially for the Senator Fumaroles line. This result is similar to gravity interpretations in the area, but with the intrinsic depth resolution possible from EM wave propagation. Low resistivity zones flank the interpreted main offsetting fault especially toward the north end of the field which may be due to alteration from geothermal fluid outflow and upflow. The appended MT soundings help to substantiate a deep, subvertical conductor intersecting the base of Dixie Valley from the middle crust, which appears to be a hydrothermal conduit feeding from deep crustal magmatic underplating. This may supply at least part of the high temperature fluids and explain enhanced He-3 levels in those fluids.

  8. Impact of climate change on soil thermal and moisture regimes in Serbia: An analysis with data from regional climate simulations under SRES-A1B.

    PubMed

    Mihailović, D T; Drešković, N; Arsenić, I; Ćirić, V; Djurdjević, V; Mimić, G; Pap, I; Balaž, I

    2016-11-15

    We considered temporal and spatial variations to the thermal and moisture regimes of the most common RSGs (Reference Soil Groups) in Serbia under the A1B scenario for the 2021-2050 and 2071-2100 periods, with respect to the 1961-1990 period. We utilized dynamically downscaled global climate simulations from the ECHAM5 model using the coupled regional climate model EBU-POM (Eta Belgrade University-Princeton Ocean Model). We analysed the soil temperature and moisture time series using simple statistics and a Kolmogorov complexity (KC) analysis. The corresponding metrics were calculated for 150 sites. In the future, warmer and drier regimes can be expected for all RSGs in Serbia. The calculated soil temperature and moisture variations include increases in the mean annual soil temperature (up to 3.8°C) and decreases in the mean annual soil moisture (up to 11.3%). Based on the KC values, the soils in Serbia are classified with respect to climate change impacts as (1) less sensitive (Vertisols, Umbrisols and Dystric Cambisols) or (2) more sensitive (Chernozems, Eutric Cambisols and Planosols). PMID:27473773

  9. Impact of climate change on soil thermal and moisture regimes in Serbia: An analysis with data from regional climate simulations under SRES-A1B.

    PubMed

    Mihailović, D T; Drešković, N; Arsenić, I; Ćirić, V; Djurdjević, V; Mimić, G; Pap, I; Balaž, I

    2016-11-15

    We considered temporal and spatial variations to the thermal and moisture regimes of the most common RSGs (Reference Soil Groups) in Serbia under the A1B scenario for the 2021-2050 and 2071-2100 periods, with respect to the 1961-1990 period. We utilized dynamically downscaled global climate simulations from the ECHAM5 model using the coupled regional climate model EBU-POM (Eta Belgrade University-Princeton Ocean Model). We analysed the soil temperature and moisture time series using simple statistics and a Kolmogorov complexity (KC) analysis. The corresponding metrics were calculated for 150 sites. In the future, warmer and drier regimes can be expected for all RSGs in Serbia. The calculated soil temperature and moisture variations include increases in the mean annual soil temperature (up to 3.8°C) and decreases in the mean annual soil moisture (up to 11.3%). Based on the KC values, the soils in Serbia are classified with respect to climate change impacts as (1) less sensitive (Vertisols, Umbrisols and Dystric Cambisols) or (2) more sensitive (Chernozems, Eutric Cambisols and Planosols).

  10. Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

    PubMed Central

    Murphy, Andrew; Semenov, Alexander; Korneev, Alexander; Korneeva, Yulia; Gol’tsman, Gregory; Bezryadin, Alexey

    2015-01-01

    We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced. PMID:25988591

  11. Effects of local climate and hydrological conditions on the thermal regime of a reservoir at Tropic of Cancer, in southern China.

    PubMed

    Wang, Sheng; Qian, Xin; Han, Bo-Ping; Luo, Lian-Cong; Hamilton, David P

    2012-05-15

    Thermal regime is strongly associated with hydrodynamics in water, and it plays an important role in the dynamics of water quality and ecosystem succession of stratified reservoirs. Changes in both climate and hydrological conditions can modify thermal regimes. Liuxihe Reservoir (23°45'50″N; 113°46'52″E) is a large, stratified and deep reservoir in Guangdong Province, located at the Tropic of Cancer of southern China. The reservoir is a warm monomictic water body with a long period of summer stratification and a short period of mixing in winter. The vertical distribution of suspended particulate material and nutrients are influenced strongly by the thermal structure and the associated flow fields. The hypolimnion becomes anoxic in the stratified period, increasing the release of nutrients from the bottom sediments. Fifty-one years of climate and reservoir operational observations are used here to show the marked changes in local climate and reservoir operational schemes. The data show increasing air temperature and more violent oscillations in inflow volumes in the last decade, while the inter-annual water level fluctuations tend to be more moderate. To quantify the effects of changes in climate and hydrological conditions on thermal structure, we used a numerical simulation model to create scenarios incorporating different air temperatures, inflow volumes, and water levels. The simulations indicate that water column stability, the duration of the mixing period, and surface and outflow temperatures are influenced by both natural factors and by anthropogenic factors such as climate change and reservoir operation schemes. Under continuous warming and more stable storage in recent years, the simulations indicate greater water column stability and increased duration of stratification, while irregular large discharge events may reduce stability and lead to early mixing in autumn. Our results strongly suggest that more attention should be focused on water quality

  12. No thermal anomalies in the mantle transition zone beneath an incipient continental rift: evidence from the first receiver function study across the Okavango Rift Zone, Botswana

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Liu, K. H.; Moidaki, M.; Reed, C. A.; Gao, S. S.

    2015-08-01

    Mechanisms leading to the initiation and early-stage development of continental rifts remain enigmatic, in spite of numerous studies. Among the various rifting models, which were developed mostly based on studies of mature rifts, far-field stresses originating from plate interactions (passive rifting) and nearby active mantle upwelling (active rifting) are commonly used to explain rift dynamics. Situated atop of the hypothesized African Superplume, the incipient Okavango Rift Zone (ORZ) of northern Botswana is ideal to investigate the role of mantle plumes in rift initiation and development, as well as the interaction between the upper and lower mantle. The ORZ developed within the Neoproterozoic Damara belt between the Congo Craton to the northwest and the Kalahari Craton to the southeast. Mantle structure and thermal status beneath the ORZ are poorly known, mostly due to a complete paucity of broad-band seismic stations in the area. As a component of an interdisciplinary project funded by the United States National Science Foundation, a broad-band seismic array was deployed over a 2-yr period between mid-2012 and mid-2014 along a profile 756 km in length. Using P-to-S receiver functions (RFs) recorded by the stations, the 410 and 660 km discontinuities bordering the mantle transition zone (MTZ) are imaged for the first time. When a standard Earth model is used for the stacking of RFs, the apparent depths of both discontinuities beneath the Kalahari Craton are about 15 km shallower than those beneath the Congo Craton. Using teleseismic P- and S-wave traveltime residuals obtained by this study and lithospheric thickness estimated by previous studies, we conclude that the apparent shallowing is the result of a 100-150 km difference in the thickness of the lithosphere between the two cratons. Relative to the adjacent tectonically stable areas, no significant anomalies in the depth of the MTZ discontinuities or in teleseismic P- and S-wave traveltime residuals are

  13. Thermal regime from bottom simulating reflectors along the N Ecuador - S Colombia margin: relation between tectonic segmentation, thermal variation and the limit of the seismic rupture zones.

    NASA Astrophysics Data System (ADS)

    Marcaillou, B.; Spence, G.; Collot, J.; Wang, K.; Ribodetti, A.

    2005-12-01

    In the North Ecuador South Columbian (NESC) convergent margin (0°N) three megathrust events, in 1942, 1958 and 1979, present rupture zones that abut one another. Multichannel seismic (MCS) reflection and bathymetric data acquired during the SISTEUR (2000) and AMADEUS (2005) cruises highlighted that the margin comprises four transverse segments (called, from south to north, the Esmeraldas, Manglares, Tumaco and Patia segments), each with clearly different tectonic and structural patterns. The central Manglares and Tumaco segments are separated by the newly discovered NW trending Manglares fault that matches the boundary between the 1958 and 1979 rupture zones. North of the fault, the fore-arc basin is shortened deformed and uplifted, while to the south the fore-arc basin, located landward of a prominent Outer Basement High (OBH), is widely subsiding and undeformed. Moreover, to the north of the Manglares fault, the underthrusting Nazca plate present an intense normal faulting is absent to the south. To investigate the relationships between seismogenesis and thermal structure along the plate boundary, we conducted thermal modelling constrained by sediment heat flow measurements and by heat flow derived from Bottom Simulating Reflectors (BSRs) on MCS lines collected during the SISTEUR and AMADEUS cruises. Just landward of the deformation front in the region of the Tumaco segment, a zone of anomalously low heat flow values is present and results in a thermal segmentation of the margin consistent with the tectonic segmentation. Finite-element thermal models carried out for each thermal segment show that: The along-strike heat flow variations are produced by changes in the age of the oceanic plate, the dip of the decollement and hydrothermal cooling due to the subduction of the strongly faulted part of the Nazca crust. The hypocenters for both the 1958 and 1979 earthquakes occurred at a depth on the interface where the temperature is ~160°C. For the seismogenic zone

  14. Continental aggregation, subduction initiation, and plume generation

    NASA Astrophysics Data System (ADS)

    Heron, P. J.; Lowman, J. P.

    2013-12-01

    Several processes unfold during the supercontinent cycle, more than one of which might result in an elevation in subcontinental mantle temperatures through the generation of mantle plumes. Paleogeographic plate reconstructions have indicated that sub-continental mantle upwellings appear below large continents that are extensively ringed by subduction zones. Moreover, several numerical simulations of supercontinent formation and dispersal attribute the genesis of sub-continental plumes to the generation of subduction zones on the edges of the supercontinent, rather than resulting from continental insulation. However, the role of the location of downwellings in producing a return-flow upwelling, and on increasing sub-continental mantle temperatures, is not fully understood. In this mantle convection study, we examine the evolution of mantle dynamics after supercontinent accretion over a subduction zone (analogous to the formation of Pangea) for a range of continental coverage. We present 2D and 3D Cartesian geometry mantle convection simulations, featuring geotherm- and pressure-dependent viscosity with thermally and mechanically distinct oceanic and continental plates. Through changing the size of the continent we are able to analyze the factors involved in the generation of mantle plumes in purely thermal convection. Furthermore, we change the upper and lower mantle viscosity to determine their relation to plume formation in vigorous mantle convection simulations. Elevated sub-continental temperatures are analyzed in relation to continental coverage to further understand the influence of continental tectonics on the thermal evolution of the mantle.

  15. The effects of season and sand mining activities on thermal regime and water quality in a large shallow tropical lake.

    PubMed

    Sharip, Zati; Zaki, Ahmad Taqiyuddin Ahmad

    2014-08-01

    Thermal structure and water quality in a large and shallow lake in Malaysia were studied between January 2012 and June 2013 in order to understand variations in relation to water level fluctuations and in-stream mining activities. Environmental variables, namely temperature, turbidity, dissolved oxygen, pH, electrical conductivity, chlorophyll-A and transparency, were measured using a multi-parameter probe and a Secchi disk. Measurements of environmental variables were performed at 0.1 m intervals from the surface to the bottom of the lake during the dry and wet seasons. High water level and strong solar radiation increased temperature stratification. River discharges during the wet season, and unsustainable sand mining activities led to an increased turbidity exceeding 100 NTU, and reduced transparency, which changed the temperature variation and subsequently altered the water quality pattern.

  16. The influence of stream thermal regimes and preferential flow paths on hyporheic exchange in a glacial meltwater stream

    USGS Publications Warehouse

    Cozzetto, Karen D.; Bencala, Kenneth E.; Gooseff, Michael N.; McKnight, Diane M.

    2013-01-01

    Given projected increases in stream temperatures attributable to global change, improved understanding of relationships between stream temperatures and hyporheic exchange would be useful. We conducted two conservative tracer injection experiments in a glacial meltwater stream, to evaluate the effects of hyporheic thermal gradients on exchange processes, including preferential flow paths (PFPs). The experiments were conducted on the same day, the first (a stream injection) during a cool, morning period and the second (dual stream and hyporheic injections) during a warm, afternoon period. In the morning, the hyporheic zone was thermally uniform at 4°C, whereas by the afternoon the upper 10 cm had warmed to 6–12°C and exhibited greater temperature heterogeneity. Solute transport modeling showed that hyporheic cross-sectional areas (As) at two downstream sites were two and seven times lower during the warm experiment. Exchange metrics indicated that the hyporheic zone had less influence on downstream solute transport during the warm, afternoon experiment. Calculated hyporheic depths were less than 5 cm, contrasting with tracer detection at 10 and 25 cm depths. The hyporheic tracer arrival at one downstream site was rapid, comparable to the in-stream tracer arrival, providing evidence for PFPs. We thus propose a conceptual view of the hyporheic zone in this reach as being dominated by discrete PFPs weaving through hydraulically isolated areas. One explanation for the simultaneous increase in temperature heterogeneity and As decrease in a warmer hyporheic zone may be a flow path preferentiality feedback mechanism resulting from a combination of temperature-related viscosity decreases and streambed heterogeneity.

  17. Continental magnetic anomaly constraints on continental reconstruction

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Crustal magnetic anomalies mapped by the MAGSAT satellite for North and South America, Europe, Africa, India, Australia and Antarctica and adjacent marine areas were adjusted to a common elevation of 400 km and differentially reduced to the radial pole of intensity 60,000 nT. These radially polarized anomalies are normalized for differential inclination, declination and intensity effects of the geomagnetic field, so that in principle they directly reflected the geometric and magnetic polarization attributes of sources which include regional petrologic variations of the crust and upper mantle, and crustal thickness and thermal perturbations. Continental anomalies demonstrate remarkably detailed correlation of regional magnetic sources across rifted margins when plotted on a reconstruction of Pangea. Accordingly, they suggest further fundamental constraints on the geologic evolution of the continents and their reconstructions.

  18. Survival, development, and growth of Snake River fall Chinook salmon Embryos, Alevins, and Fry Exposed to Variable Thermal and Dissolved Oxygen Regimes

    SciTech Connect

    Geist, David R.; Abernethy, Cary S.; Hand, Kristine D.; Cullinan, Valerie I.; Chandler, James A.; Groves, Philip

    2006-11-01

    Fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Hells Canyon reach of the Snake River, Idaho (rkm 240-397), at water temperatures above 16 C. This temperature exceeds the states of Idaho and Oregon water quality standards for salmonid spawning. These standards are consistent with results from studies of embryos exposed to a constant thermal regime, while salmon eggs in the natural environment are rarely exposed to a constant temperature regime. The objective of this study was to assess whether variable temperatures (i.e., declining after spawning) affected embryo survival, development, and growth of Snake River fall Chinook salmon alevins and fry. In 2003, fall Chinook salmon eggs were exposed to initial incubation temperatures ranging from 11-19 C in 2 C increments, and in 2004 eggs were exposed to initial temperatures of 13 C, 15 C, 16 C, 16.5 C, and 17 C. In both years, temperatures were adjusted downward approximately 0.2 C/day to mimic the thermal regime of the Snake River where these fish spawn. At 37-40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures >17 C in both years. A logistic regression model estimated that a 50% reduction in survival from fertilization to emergence would occur at an initial incubation temperature of {approx}16 C. The laboratory results clearly showed a significant reduction in survival between 15 C and 17 C, which supported the model estimate. Results from 2004 showed a rapid decline in survival occurred between 16.5 C and 17 C, with no significant differences in survival at initial incubation temperatures <16.5 C. There were no significant differences across the range of initial temperature exposures for alevin and fry size at hatch and emergence. Differences in egg mass among females (notably 2003) most likely masked any

  19. The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

    USGS Publications Warehouse

    Hurwitz, S.; Farrar, C.D.; Williams, C.F.

    2010-01-01

    Long Valley Caldera in eastern California formed 0.76Ma ago in a cataclysmic eruption that resulted in the deposition of 600km3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~290MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40MWe. The RD in the center of the caldera was uplifted by ~80cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50??C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7??C and 129.5??C and bottom hole temperatures range between 99.4??C and 129.5??C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate

  20. Random walks with thermalizing collisions in bounded regions: Physical applications valid from the ballistic to diffusive regimes

    NASA Astrophysics Data System (ADS)

    Swank, C. M.; Petukhov, A. K.; Golub, R.

    2016-06-01

    The behavior of a spin undergoing Larmor precession in the presence of fluctuating fields is of interest to workers in many fields. The fluctuating fields cause frequency shifts and relaxation which are related to their power spectrum, which can be determined by taking the Fourier transform of the auto-correlation functions of the field fluctuations. Recently we have shown how to calculate these correlation functions for all values of mean-free path (ballistic to diffusive motion) in finite bounded regions by using the model of persistent continuous time random walks (CTRW) for particles subject to scattering by fixed (frozen) scattering centers so that the speed of the moving particles is not changed by the collisions. In this work we show how scattering with energy exchange from an ensemble of scatterers in thermal equilibrium can be incorporated into the CTRW. We present results for 1, 2, and 3 dimensions. The results agree for all these cases contrary to the previously studied "frozen" models. Our results for the velocity autocorrelation function show a long-time tail (˜t-1 /2 ), which we also obtain from conventional diffusion theory, with the same power, independent of dimensionality. Our results are valid for any Markovian scattering kernel as well as for any kernel based on a scattering cross section ˜1 /v .

  1. Influence of thermal regime and land use on benthic invertebrate communities inhabiting headwater streams exposed to contrasted shading.

    PubMed

    Dohet, Alain; Hlúbiková, Daša; Wetzel, Carlos E; L'Hoste, Lionel; Iffly, Jean François; Hoffmann, Lucien; Ector, Luc

    2015-02-01

    Headwaters account for a high proportion of total freshwater stream-channel length in a drainage basin and are critical habitats for rare, endangered, and specialized species. In the context of climate warming, increasing water temperatures may be an ultimate threat to cold-adapted species even in temperate ecosystems. Climate change effects on streams may interact with other pressures such as pollution or habitat fragmentation, confounding their real impact on biological communities. Three headwater streams exposed to contrasted shading and land use conditions were sampled over a three-year period in spring and autumn (2010-2012). Five stations distributed along the longitudinal continuum were chosen in the upstream part of each stream. In addition to benthic invertebrate sampling, water temperature was recorded continuously using data loggers. Results showed that the riparian woodland associated with forested land use throughout the catchment clearly moderated winter temperature minima, summer temperature maxima and thermal variability compared to open river channels with narrow or absent riparian tree cover. Although, the variability in macroinvertebrate species distribution was mainly attributed to anthropogenic land use in the catchment, a significant part of the variability was explained by temperature descriptors such as the number of cumulative degree-days in summer and extremes in winter temperature. Trichoptera species preferring headwaters and cold water temperatures were found exclusively in the forested unimpacted stream. Conservation issues are discussed in relation to the predicted loss of the potential future distributions of these Trichoptera cold-adapted species.

  2. Influence of thermal regime and land use on benthic invertebrate communities inhabiting headwater streams exposed to contrasted shading.

    PubMed

    Dohet, Alain; Hlúbiková, Daša; Wetzel, Carlos E; L'Hoste, Lionel; Iffly, Jean François; Hoffmann, Lucien; Ector, Luc

    2015-02-01

    Headwaters account for a high proportion of total freshwater stream-channel length in a drainage basin and are critical habitats for rare, endangered, and specialized species. In the context of climate warming, increasing water temperatures may be an ultimate threat to cold-adapted species even in temperate ecosystems. Climate change effects on streams may interact with other pressures such as pollution or habitat fragmentation, confounding their real impact on biological communities. Three headwater streams exposed to contrasted shading and land use conditions were sampled over a three-year period in spring and autumn (2010-2012). Five stations distributed along the longitudinal continuum were chosen in the upstream part of each stream. In addition to benthic invertebrate sampling, water temperature was recorded continuously using data loggers. Results showed that the riparian woodland associated with forested land use throughout the catchment clearly moderated winter temperature minima, summer temperature maxima and thermal variability compared to open river channels with narrow or absent riparian tree cover. Although, the variability in macroinvertebrate species distribution was mainly attributed to anthropogenic land use in the catchment, a significant part of the variability was explained by temperature descriptors such as the number of cumulative degree-days in summer and extremes in winter temperature. Trichoptera species preferring headwaters and cold water temperatures were found exclusively in the forested unimpacted stream. Conservation issues are discussed in relation to the predicted loss of the potential future distributions of these Trichoptera cold-adapted species. PMID:25461112

  3. Hesperian polythermal glaciation in Isidis Planitia, Mars - Ice sheet dynamics and thermal regime inferred from numerical modeling

    NASA Astrophysics Data System (ADS)

    Souček, Ondřej; Bourgeois, Olivier; Pochat, Stéphane; Guidat, Thomas

    2015-04-01

    We test the hypothesis that the Thumbprint Terrain observed on the floor of Isidis Planitia, a giant impact crater located close to the martian equator, is a landform assemblage inherited from a glaciation during the Hesperian. For this purpose, we perform numerical simulations with a coupled thermo-mechanical model of ice sheet dynamics. We use surface temperatures and ice accumulation/ablation patterns predicted by a climatic Global Circulation Model, and values of the geothermal heat flux provided by a global model of planetary thermal evolution. We find that, with atmospheric physical properties similar to the current ones and under favorable orbital conditions, net ice accumulation in the northwestern part of Isidis Planitia leads within a few Ma to the development of a massive ice sheet, as much as 4.9 km in thickness, over the entire basin. The modeled ice sheet is polythermal: its center and its periphery are permanently frozen to the base, while the pressure melting point is reached episodically in an intermediate ring. Our simulations suggest that the propagation of thermo-mechanical melting waves in this ring is responsible for the formation of the Thumbprint Terrain, a probable martian equivalent of terrestrial ribbed moraines. They support the interpretation that sinuous ridges and linear valleys observed at the periphery of the basin are parts of a subglacial network of eskers and tunnel valleys that drained glacial meltwater outwards, across the cold-based outer part of the ice sheet. This work strengthens the hypothesis that massive glaciers covered large portions of the martian surface before the Amazonian and that basal melting below the wet-based portions of these ice sheets contributed significantly to the production and flow of liquid water in the ancient martian history.

  4. A 3 Ga old polythermal ice sheet in Isidis Planitia, Mars: Dynamics and thermal regime inferred from numerical modeling

    NASA Astrophysics Data System (ADS)

    Souček, Ondřej; Bourgeois, Olivier; Pochat, Stéphane; Guidat, Thomas

    2015-09-01

    Isidis Planitia is a 1350 km wide impact crater located close to the martian equator. To test the hypothesis that the 2.8 to 3.4 Ga old Thumbprint Terrain preserved on the floor of this basin is a glacial landform assemblage, we perform a numerical simulation of glaciation with a thermo-mechanically coupled model of ice sheet dynamics. As model inputs, we use surface temperatures and ice accumulation patterns predicted by a General Circulation Model based on the present-day atmospheric characteristics, and values of the geothermal heat flux provided by a global model of planetary thermal evolution. We find that, under favorable orbital conditions, an ice sheet covering the entire basin can develop in 2 to 5 Ma, with a maximum thickness of 4.9 km. The modeled ice sheet is polythermal: it is permanently cold-based in the periphery and, due to a negative heat-flux anomaly, also in the center, while the pressure melting point is reached in an intermediate ring. Our simulation is consistent with the interpretation that the Thumbprint Terrain is a martian equivalent of terrestrial ribbed moraines and has formed below a wet-based ice sheet. It supports also the interpretation that sinuous ridges and linear valleys observed at the periphery of the basin are parts of a subglacial network of eskers and tunnel valleys that drained the glacial meltwater outwards, across the cold-based periphery of the ice sheet. This work strengthens the hypothesis that glaciers thick as much as several km may have existed on Mars several Ga ago and that glacial basal melting may have contributed to the production and flow of surface liquid water at that time, under an atmosphere no thicker than the present-day one.

  5. The Response of the Mediterranean Gorgonian Eunicella singularis to Thermal Stress Is Independent of Its Nutritional Regime

    PubMed Central

    Ezzat, Leïla; Merle, Pierre-Laurent; Furla, Paola; Buttler, Alexandre; Ferrier-Pagès, Christine

    2013-01-01

    Over the last few decades, sessile benthic organisms from the Mediterranean Sea have suffered from the global warming of the world's oceans, and several mass mortality events were observed during warm summers. It has been hypothesized that mortality could have been due to a nutrient (food) shortage following the stratification of the water column. However, the symbiotic gorgonian Eunicella singularis has also presented a locally exceptional mortality, despite its autotrophic capacities through the photosynthesis of its dinoflagellate symbionts. Thus, this study has experimentally investigated the response of E. singularis to a thermal stress (temperature increase from 18 to 26°C), with colonies maintained more than 2 months under four nutritional diets: autotrophy only (AO), autotrophy and inorganic nitrogen addition (AN), autotrophy and heterotrophy (AH), heterotrophy only (HO). At 18°C, and contrary to many other anthozoans, supplementation of autotrophy with either inorganic nitrogen or food (heterotrophy) had no effect on the rates of respiration, photosynthesis, as well as in the chlorophyll, lipid and protein content. In the dark, heterotrophy maintained the gorgonian's metabolism, except a bleaching (loss of pigments), which did not affect the rates of photosynthesis. At 24°C, rates of respiration, and photosynthesis significantly decreased in all treatments. At 26°C, in addition to a decrease in the lipid content of all treatments, a bleaching was observed after 1 week in the AO treatment, while the AH and AN treatments resisted three weeks before bleaching. These last results suggest that, temperatures above 24°C impair the energetic reserves of this species and might explain the mortality events in the Mediterranean. PMID:23667711

  6. Investigation of the thermal regime and geologic history of the Cascade volcanic arc: First phase of a program for scientific drilling in the Cascade Range

    SciTech Connect

    Priest, G.R.

    1987-01-01

    A phased, multihole drilling program with associated science is proposed as a means of furthering our understanding of the thermal regime and geologic history of the Cascade Range of Washington, Oregon, and northern California. The information obtained from drilling and ancillary geological and geophysical investigations will contribute to our knowledge in the following general areas: (1) the magnitude of the regional background heat flow of parts of the Quaternary volcanic belt dominated by the most abundant volcanic rock types, basalt and basaltic andesite; (2) the nature of the heat source responsible for the regional heat-flow anomaly; (3) the characteristics of the regional hydrothermal and cold-water circulation; the rates of volcanism for comparison with models for the rate and direction of plate convergence of the Cascades; (5) the history of deformation and volcanism in the volcanic arc that can be related to subduction; (6) the present-day stress regime of the volcanic arc and the relation of these stresses to plate interactions and possible large earthquakes; and the current geometry of the subducted oceanic plate below the Cascade Range and the relationship of the plate to the distribution of heat flow, Quaternary volcanism, and Quaternary deformation. Phase I research will be directed toward a detailed investigation of the Santiam Pass segment. In concert with the Santiam Pass research, a detailed study of the nearby Breitenbush Hot Springs area is also recommended as a component of Phase I. The object of the Breitenbush research is to study one of the hottest known Cascade hydrothermal systems, which coincidentally also has a good geological and geophysical data base. A coordinated program of drilling, sampling, subsurface measurements, and surface surveys will be associated with the drilling of several holes.

  7. Thermal regime of the Costa Rican convergent margin: 1. Along-strike variations in heat flow from probe measurements and estimated from bottom-simulating reflectors

    NASA Astrophysics Data System (ADS)

    Harris, Robert N.; Grevemeyer, Ingo; Ranero, CéSar R.; Villinger, Heinrich; Barckhausen, Udo; Henke, Thomas; Mueller, Christian; Neben, Soenke

    2010-12-01

    The thermal structure of convergent margins provides information related to the tectonics, geodynamics, metamorphism, and fluid flow of active plate boundaries. We report 176 heat flow measurements made with a violin bow style probe across the Costa Rican margin at the Middle America Trench. The probe measurements are collocated with seismic reflection lines. These seismic reflection lines show widespread distribution of bottom-simulating reflectors (BSRs). To extend the spatial coverage of heat flow measurements we estimate heat flow from the depth of BSRs. Comparisons between probe measurements and BSR-derived estimates of heat flow are generally within 10% and improve with distance landward of the deformation front. Together, these determinations provide new information on the thermal regime of this margin. Consistent with previous studies, the margin associated with the northern Nicoya Peninsula is remarkably cool. We define better the southern boundary of the cool region. The northern extent of the cool region remains poorly determined. A regional trend of decreasing heat flow landward of the deformation front is apparent, consistent with the downward advection of heat by the subducting Cocos Plate. High wave number variability at a scale of 5-10 km is significantly greater than the measurement uncertainty and is greater south of the northern Nicoya Peninsula. These heat flow anomalies vary between approximately 20 and 60 mW m-2 and are most likely due to localized fluid flow through mounds and faults on the margin. Simple one-dimensional models show that these anomalies are consistent with flow rates of 7-15 mm yr-1. Across the margin toe variability is significant and likely due to fluid flow through deformation structures associated with the frontal sedimentary prism.

  8. Mycoplasmal upper respiratory tract disease across the range of the threatened Mojave Desert tortoise: associations with thermal regime and natural antibodies.

    PubMed

    Sandmeier, Franziska C; Tracy, C Richard; Hagerty, Bridgette E; DuPré, Sally; Mohammadpour, Hamid; Hunter, Kenneth

    2013-03-01

    Most research of upper respiratory tract disease (mycoplasmal URTD) in the threatened Mojave Desert tortoise (Gopherus agassizii) has worked under the hypothesis that the pathogen, Mycoplasma agassizii, has a relatively consistent and predictable effect on tortoise populations across their natural range. In contrast, we hypothesized that multiple factors influence the prevalence of disease and analyzed biological and environmental variables that vary significantly across the Mojave Desert. We used multiple regression models to analyze associations between mycoplasmal URTD and the genetic structure of 24 tortoise populations, levels of natural antibody (NAb) to M. agassizii in tortoises (one component of the innate immune system), precipitation, and colder thermal regimes. We detected a significant, positive association between mean levels of NAb and seroprevalence to M. agassizii. We hypothesized that NAbs may provide tolerance to mycoplasmal infections and that more tolerant populations may act as host reservoirs of disease. We also detected significant associations between colder winters and mycoplasmal URTD, suggesting that colder winters may depress tortoise immune resistance against M. agassizii or enhance conditions for the growth of M. agassizii.

  9. Electronic transport regimes through an alkoxythiolated diphenyl-2,2'-bithiophene-based molecular junction diodes: critical assessment of the thermal dependence

    NASA Astrophysics Data System (ADS)

    Pace, Giuseppina; Caranzi, Lorenzo; Bucella, Sadir G.; Canesi, Eleonora V.; Dell'Erba, Giorgio; Bertarelli, Chiara; Caironi, Mario

    2015-01-01

    The detailed understanding of electronic transport through a single molecule or an ensemble of self-assembled molecules embedded between two metallic leads is still a matter of controversy. Multiple factors influence the charge transport in the molecular junction, with particular attention to be given to the band states of the electrodes, molecular orbital energies, bias potential and importantly molecule-electrode electronic coupling. Moreover it is not trivial to disentangle molecular contributions from other possible conduction pathways directly coupling the opposite electrodes. We here investigate the electronic transport properties of an ensemble molecular junction embedding an alkylthiol derivative of a diphenol substituted bithiophene (DPBT) by means of current vs. voltage and temperature dependent measurements. We explored different junction configurations using: micropores (Au//DPBT//Au and Au//DPBT-polymer conductor//Au) and conductive-atomic force microscopy (c-AFM). In all cases, we found a transition voltage VT of ~0.35 V. The consistent presence of a similar VT in all the tested configurations is a strong, but not conclusive, indication of a molecular signature in the charge transport, which we assessed and confirmed by temperature dependent measurements. We found a transition from an incoherent resonant tunneling at low biases and close to room temperature, where transport is thermally activated with an activation energy of ~85 meV, to a coherent tunneling at voltages higher than VT. Unlike many other molecular junctions reported in the literature, resonant conditions commonly attributed to a hopping transport regime can be found already at room temperature and very low biases for a molecule only ~1.5 nm long. This paper is the first report to clearly show temperature activated transport through a short and not fully conjugated molecule. Moreover, we could clearly identify a regime at low temperatures and low bias where the transport mechanism is

  10. Thermal structure of the lithosphere: a petrologic model.

    PubMed

    Macgregor, I D; Basu, A R

    1974-09-20

    A preliminary evaluation of the thermal history of the upper mantle as determined by petrologic techniques indicates a general correspondence with theoretically derived models. The petrologic data supply direct information which may be used as an independent calibration of calculated models, serve as a base for evaluating the assumptions of the theoretical approach, and allow more careful selection of the variables describing mantle thermal properties and processes. Like the theoretical counterpart, the petrological approach indicates that the lithosphere is dominated by two thermal regimes: first, there is a continental regime which cools at rates of the order of 10(9) years and represents the longterm cooling of the earth. Secondly, superimposed on the continental evolution is the thermal event associated with the formation of an oceanic basin, and which may be thought of as a 10(8) year convective perturbation on the continental cycle. Of special interest is petrologic evidence for a sudden steepening of the thermal gradients across the lithosphere-asthenosphere boundary not seen in the theoretical models. The unexpected change of slope points to the need for a critical reevaluation of the thermal processes and properties extant in the asthenosphere. The potential of the petrologic contribution has yet to be fully realized. For a start, this article points to an important body of independent evidence critical to our understanding of the earth's thermal history.

  11. Regime change?

    SciTech Connect

    Pilat, Joseph F.; Budlong-Sylvester, K. W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  12. Use of the subsurface thermal regime as a groundwater-flow tracer in the semi-arid western Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Salem, Zenhom E.; Bayumy, Dina A.

    2016-06-01

    Temperature profiles from 25 boreholes were used to understand the spatial and vertical groundwater flow systems in the Western Nile Delta region of Egypt, as a case study of a semi-arid region. The study area is located between the Nile River and Wadi El Natrun. The recharge areas, which are located in the northeastern and the northwestern parts of the study area, have low subsurface temperatures. The discharge areas, which are located in the western (Wadi El Natrun) and southern (Moghra aquifer) parts of the study area, have higher subsurface temperatures. In the deeper zones, the effects of faults and the recharge area in the northeastern direction disappear at 80 m below sea level. For that depth, one main recharge and one main discharge area are recognized. The recharge area is located to the north in the Quaternary aquifer, and the discharge area is located to the south in the Miocene aquifer. Two-dimensional groundwater-flow and heat-transport models reveal that the sealing faults are the major factor disturbing the regional subsurface thermal regime in the study area. Besides the main recharge and discharge areas, the low permeability of the faults creates local discharge areas in its up-throw side and local recharge areas in its down-throw side. The estimated average linear groundwater velocity in the recharge area is 0.9 mm/day to the eastern direction and 14 mm/day to the northwest. The average linear groundwater discharge velocities range from 0.4 to 0.9 mm/day in the southern part.

  13. Cyclic CO(2) emissions during the high temperature pulse of fluctuating thermal regime in eye-pigmented pupae of Megachile rotundata.

    PubMed

    Yocum, George D; Greenlee, Kendra J; Rinehart, Joseph P; Bennett, Meghan M; Kemp, William P

    2011-12-01

    Megachile rotundata (Hymenoptera: Megachilidae), the primary pollinator used in alfalfa seed production, may need to be exposed to low-temperature storage to slow the insects' development to better match spring emergence with the alfalfa bloom. It has been demonstrated that using a fluctuating thermal regime (FTR) improves the tolerance of pupae to low temperatures. Carbon dioxide emission rates were compared between four different FTRs, all with a base temperature of 6°C and a daily high-temperature pulse. Four different high-temperature pulses were examined, 15 or 25°C for 2h and 20°C for 1 or 2h. A subset of pupae at the FTR base temperature of 6°C exhibited continuous gas exchange and, once ramped to 20 or 25°C, shifted to cyclic gas exchange. As temperatures were ramped down from the high-temperature pulse to 6°C, the pupae reverted to continuous gas exchange. The following conclusions about the effect of FTR on the CO(2) emissions of M. rotundata pupae exposed to low-temperature storage during the spring incubation were reached: 1) the high temperature component of the FTR was the best predictor of respiratory pattern; 2) neither pupal body mass nor days in FTR significantly affected which respiratory pattern was expressed during FTRs; 3) cyclic gas exchange was induced only in pupae exposed to temperatures greater than 15°C during the FTR high temperature pulse; and 4) a two hour pulse at 25°C doubled the number of CO(2) peaks observed during the FTR pulse as compared to a two hour pulse at 20°C. PMID:21854865

  14. Use and usability of experimental monitoring data and temperature modeling to inform adaptive management of the Colorado River's thermal regime for native fish conservation below Glen Canyon Dam

    NASA Astrophysics Data System (ADS)

    Melis, T. S.

    2014-12-01

    Seasonal thermal variability of the Colorado River in Grand Canyon was severely decreased by closure of Glen Canyon Dam and filling of Lake Powell reservoir that was achieved in 1980. From 1973 to 2002, downstream summer river temperatures at Lees Ferry were about 18°C below pre-dam conditions, and limited juvenile native fish growth and survival. A large-scale flow experiment to improve the river's thermal regime for spawning and rearing habitat of endangered native humpback chub and other native fish in eastern Grand Canyon was conducted in Water Year 2000. Monitoring revealed warming, but well below the 16-18°C optimum for chub 124 km below the dam near the Little Colorado River confluence, and no measurable chub population increase in Grand Canyon. Fall-timed stable flow experiments to improve shoreline chub nursery habitat (2008-12) were also inconclusive relative to juvenile chub growth and recruitment. Field studies also showed that daytime warming of shoreline habitats used by fish under steady flows is limited by high daily exchange rates with main channel water. Monthly averaged and higher resolution temperature models have also been developed and used to support more recent experimental management planning. Temperature simulations have been useful for screening dam release scenarios under varied reservoir storage conditions with and without use of previously proposed but never constructed multilevel intake structures on the dam's hydroelectric units. Most importantly, modeling revealed the geophysical limits on downstream warming under existing water management and dam operating policies. Hourly unsteady flow simulations in 2006 predicted equivalent levels of average downstream river warming under either fluctuating or steady flows for a given monthly release volume. River warming observed since 2002, has resulted from reduced Lake Powell storage resulting from drier upper basin hydrology. In support of new environmental compliance on dam operations

  15. Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland

    SciTech Connect

    Mullis, J. ); Dubessy, J.; Poty, B. ); O'Neil, J. )

    1994-05-01

    Fluid evolution during neo-alpine metamorphism during late stages of the continental collision between Europe and Africa was studied by analyzing fluid inclusions in alpine fissure quartz collected in forty-nine localities along a geotraverse through the Central Alps, Switzerland. The methods employed include microthermometry, micro-Raman spectroscopy, K/Na thermometry, and stable isotope analysis. Early fluid inclusions provide evidence of close to peak metamorphic temperatures of the late Tertiary or neo-alpine metamorphic event. Fluid composition evolved along the geotraverse from north to south as follows: higher hydrocarbons were dominant in the low- and medium-grade diagenetic zones, methane was the main volatile in the high-grade diagenetic and low-grade anchizone, water dominated in the high-grade anchizone and low-grade epizone, with CO[sub 2] > 10 mol% in the high-grade epizone and in the mesozone. Higher hydrocarbons and CH[sub 4] were the products of kerogen maturation and cracking of preexisting petroleum. Large water supplies originated from the dehydration of cooler metasedimentary rocks that were overthrust by crystalline basements of the Lepontines, Aar, and Gotthard massifs. Carbon isotope analyses suggest that the CO[sub 2] component was derived from oxidation of graphitic matter, especially in the vicinity of sulfate-bearing metasediments and from decarbonation reactions. In the Aar and Gotthard massifs as well as in the Helvetic Axen nappe and its underlying North Helvetic flysch, high fluid pressures prevailed and favored nappe transport. By contrast, in the southern Lepontine area, very low early fluid pressures were probably related to dry rocks and scarce metasediments, and to high geothermal gradients that resulted from intense uplift and erosion between 26 and 18 Ma.

  16. Snowpack regimes of the Western United States

    NASA Astrophysics Data System (ADS)

    Trujillo, Ernesto; Molotch, Noah P.

    2014-07-01

    Snow accumulation and melt patterns play a significant role in the water, energy, carbon, and nutrient cycles in the montane environments of the Western United States. Recent studies have illustrated that changes in the snow/rainfall apportionments and snow accumulation and melt patterns may occur as a consequence of changes in climate in the region. In order to understand how these changes may affect the snow regimes of the region, the current characteristics of the snow accumulation and melt patterns must be identified. Here we characterize the snow water equivalent (SWE) curve formed by the daily SWE values at 766 snow pillow stations in the Western United States, focusing on several metrics of the yearly SWE curves and the relationships between the different metrics. The metrics are the initial snow accumulation and snow disappearance dates, the peak snow accumulation and date of peak, the length of the snow accumulation season, the length of the snowmelt season, and the snow accumulation and snowmelt slopes. Three snow regimes emerge from these results: a maritime, an intermountain, and a continental regime. The maritime regime is characterized by higher maximum snow accumulations reaching 300 cm and shorter accumulation periods of less than 220 days. Conversely, the continental regime is characterized by lower maximum accumulations below 200 cm and longer accumulation periods reaching over 260 days. The intermountain regime lies in between. The regions that show the characteristics of the maritime regime include the Cascade Mountains, the Klamath Mountains, and the Sierra Nevada Mountains. The intermountain regime includes the Eastern Cascades slopes and foothills, the Blue Mountains, Northern and Central basins and ranges, the Columbia Mountains/Northern Rockies, the Idaho Batholith, and the Canadian Rockies. Lastly, the continental regime includes the Middle and Southern Rockies, and the Wasatch and Uinta Mountains. The implications of snow regime

  17. Regional magnetic anomaly constraints on continental breakup

    SciTech Connect

    von Frese, R.R.B.; Hinze, W.J.; Olivier, R.; Bentley, C.R.

    1986-01-01

    Continental lithosphere magnetic anomalies mapped by the Magsat satellite are related to tectonic features associated with regional compositional variations of the crust and upper mantle and crustal thickness and thermal perturbations. These continental-scale anomaly patterns when corrected for varying observation elevation and the global change in the direction and intensity of the geomagnetic field show remarkable correlation of regional lithospheric magnetic sources across rifted continental margins when plotted on a reconstruction of Pangea. Accordingly, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans.

  18. A Climatological Study of Evapotranspiration and Moisture Stress Across the Continental U.S. Based on Thermal Remote Sensing. II. Surface Moisture Climatology.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Robust satellite-derived moisture stress indices will be beneficial to operational drought monitoring, both in the US and globally. Using thermal infrared imagery from the Geostationary Operational Environmental Satellites (GOES) and vegetation information from the Moderate Resolution Imaging Spect...

  19. Structural, igneous and metamorphic footprints of Pangea break-up preserved in the subducted Austroalpine continental lithosphere of the European Alps.

    NASA Astrophysics Data System (ADS)

    Spalla, M. I.; Gosso, G.; Rebay, G.; Roda, M.; Zanoni, D.; Zucali, M.

    2015-12-01

    Although in the Alps a large amount of continental lithosphere from both European (lower plate) and Adriatic (upper plate) continental margins was absorbed in the sub-lithospheric mantle during Alpine subduction, relict metamorphic and igneous imprints of the Variscan convergence and the successive Pangea break-up are preserved in the continental crust of both margins. These pre-Alpine signatures are preserved either in small volumes within the exhumed continental crust slivers of the axial belt or in the Alpine hinterland and foreland crusts that were never reworked in deep-seated conditions. Because of the common occurrence of metamorphic and igneous markers of the Variscan convergence in the pre-Alpine continental crust, the Permian-Triassic high thermal regime, which left widespread metamorphic and igneous imprints, can be interpreted as the effect of lithospheric thinning leading to continental rifting and subsequent Tethyan ocean opening. In addition, even Permian igneous activity and related basin formation may be interpreted as linked to lithospheric extension leading to the Pangaea break-up and to subsequent oceanization, predating the marine transgression from the east, where the Neotethys Ocean was opening. Permian-Triassic HT-LP metamorphic imprints recorded in the Austroalpine continental units are correlatable to this scenario; these peculiar metamorphic patterns have been widely recognized in lower, intermediate and upper continental crust. HT assemblages mark newly differentiated foliations locally associated with discrete shear zones, mainly in metapelites. Ages inferred for Tmax conditions are comprised between 220 and 295 Ma and Jurassic mineral ages are obtained where LP-LT metamorphic imprints, recorded during uplift and associated with fluid circulation, are dominant. The uplift paths are usually characterized by a high T/P ratio and wide parts of the uplift paths occurred under high thermal regime and the exhumation of some of the deep

  20. Continental Margins: Linking Ecosystems

    NASA Astrophysics Data System (ADS)

    Kelly-Gerreyn, Boris; Rabalais, Nancy; Middelburg, Jack; Roy, Sylvie; Liu, Kon-Kee; Thomas, Helmuth; Zhang, Jing

    2008-02-01

    Impacts of Global, Local and Human Forcings on Biogeochemical Cycles and Ecosystems, IMBER/LOICZ Continental Margins Open Science Conference; Shanghai, China, 17-21 September 2007; More than 100 scientists from 25 countries came together to address global, regional, local, and human pressures interactively affecting continental margin biogeochemical cycles, marine food webs, and society. Continental margins cover only 12% of the global ocean area yet account for more than 30% of global oceanic primary production. In addition, continental margins are the most intensely used regions of the world's ocean for natural commodities, including productive fisheries and mineral and petroleum resources. The land adjacent to continental margins hosts about 50% of the world's population, which will bear many direct impacts of global change on coastal margins. Understanding both natural and human-influenced alterations of biogeochemical cycles and ecosystems on continental margins and the processes (including feedbacks) that threaten sustainability of these systems is therefore of global interest.

  1. Deep continental margin reflectors

    USGS Publications Warehouse

    Ewing, J.; Heirtzler, J.; Purdy, M.; Klitgord, Kim D.

    1985-01-01

    In contrast to the rarity of such observations a decade ago, seismic reflecting and refracting horizons are now being observed to Moho depths under continental shelves in a number of places. These observations provide knowledge of the entire crustal thickness from the shoreline to the oceanic crust on passive margins and supplement Consortium for Continental Reflection Profiling (COCORP)-type measurements on land.

  2. Freshly brewed continental crust

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Hayes, J. L.; Caddick, M. J.; Madrigal, P.

    2015-12-01

    Earth's crust is the life-sustaining interface between our planet's deep interior and surface. Basaltic crusts similar to Earth's oceanic crust characterize terrestrial planets in the solar system while the continental masses, areas of buoyant, thick silicic crust, are a unique characteristic of Earth. Therefore, understanding the processes responsible for the formation of continents is fundamental to reconstructing the evolution of our planet. We use geochemical and geophysical data to reconstruct the evolution of the Central American Land Bridge (Costa Rica and Panama) over the last 70 Ma. We also include new preliminary data from a key turning point (~12-6 Ma) from the evolution from an oceanic arc depleted in incompatible elements to a juvenile continental mass in order to evaluate current models of continental crust formation. We also discovered that seismic P-waves (body waves) travel through the crust at velocities closer to the ones observed in continental crust worldwide. Based on global statistical analyses of all magmas produced today in oceanic arcs compared to the global average composition of continental crust we developed a continental index. Our goal was to quantitatively correlate geochemical composition with the average P-wave velocity of arc crust. We suggest that although the formation and evolution of continents may involve many processes, melting enriched oceanic crust within a subduction zone, a process probably more common in the Achaean where most continental landmasses formed, can produce the starting material necessary for juvenile continental crust formation.

  3. Organic geochemistry of outer continental margins and deep ocean sediments

    SciTech Connect

    Whelan, J.K.

    1990-01-01

    This report discusses the activities and progress made in the study of continental margins and deep ocean sediments. Topics discussed are the calibration of thermal maturation markers, hydrous pyrolysis studies and sample collection. (KS)

  4. The basins on the Argentine continental margin

    SciTech Connect

    Urien, C.M.

    1996-08-01

    After the stabilization of the central Gondwana Craton, orogenic belts were accreted, as a result of convergence events and an extensive passive margin developed in southwestern Gondwana. Thermal subsidence in Parana, Karoo-Ventania basins and the Late Paleozoic-Early Mesozoic rifts, were modified by the Gondwana breakup and the South Atlantic opening. Early Paleozoic marine transgressions deposited the Table Mountain Group in Ventania. In southwestern Patagonia foreland clastics were deposited. Magmatic arcs and marine units indicate a tectonic trough was formed, alternating with continental sequences, over Late Paleozoic metamorphics and intrusives, resulting from plastered terrains along the Gondwana margin. In Patagonia, Permo-Carboniferous continental and glacio marine clastics infill the basins, while in Ventania, paralic sequences, grade from neritic to continental to the northeast, extending beneath the continental margin. The Triassic-Jurassic rift basins progressed onto regional widespread acid lavas and were infilled by lagoonal organic-rich sequences. Early drift phase built basins transverse to the margin, with fluvio-lacustrine sequences: Salado, Colorado, Valdes-Rawson, San Julian and North Malvinas intracratonic basins, which underwent transtensional faulting. Post-Oxfordian to Neocomian brackish sequences, onlapped the conjugate basins during the margin`s drift, with petroleum systems, as in Austral and Malvinas. In the Valanginian, basic extrusions commenced to form on the continental border, heralding the oceanic phase. Due to thermal subsidence, offlaping sediments prograded onto the remaining half-grabens. Several petroleum systems, proven and hypothetical, are identified in this region.

  5. Snowpack Regimes of the Western United States

    NASA Astrophysics Data System (ADS)

    Trujillo, E.; Molotch, N. P.

    2011-12-01

    Snow accumulation and melt patterns play a significant role in the water, energy, carbon and nutrient cycles in the montane environments of the Western United States. Recent studies have illustrated that changes in the snow/rainfall apportionments, and snow accumulation and melt patterns may occur as a consequence of changes in climate in the region. In order to understand how these changes may affect the snow regimes of the region, the current characteristics of the snow accumulation and melt patterns must be identified. Here, we characterize the snow water equivalent (SWE) curve formed by the daily SWE values at over seven hundred snow pillow stations in the Western U.S., focusing on several metrics of the yearly SWE curves and the cross relationships between the different metrics. The metrics include the initial snow accumulation and meltout dates, the peak accumulation and date of peak, the time from initial accumulation to peak, the time from peak to meltout, the accumulation and melt slopes, and the daily rates of accumulation and melt. Three distinct regimes emerge from these results: a maritime, an intermediate (intercontinental), and a continental regime. The maritime regime is characterized by higher maximum snow accumulations reaching 300 cm and shorter accumulation periods of less than 220 days, while on the other hand; the continental regime is characterized by lower maximum accumulations below 200 cm and longer accumulation periods reaching over 260 days. The intercontinental regime lies in between. Several other differences are identified between the metrics of the SWE curve in these regimes. The regions that show the characteristics of the maritime regime include the Cascade Mountains, the Klamath Mountains, and the Sierra Nevada Mountains. The intercontinental regime includes the Northern and Central basins and ranges, the Idaho Batholith, the Northern Rockies and the Blue Mountains. Lastly, the Continental regime includes the Middle and Southern

  6. Continental Basaltic Rocks

    NASA Astrophysics Data System (ADS)

    Farmer, G. L.

    2003-12-01

    During the past few decades, geochemical studies of continental basaltic rocks and their petrologic kin have become mainstays of studies of the continental lithosphere. These igneous rocks have taken on such an important role largely because the chemical and isotopic composition of continental basaltic rocks and their mantle (see Chapter 2.05) and crustal xenoliths (see Chapter 3.01) provide the best proxy record available to earth scientists for the chemical and physical evolution of the deep continental lithosphere and underlying mantle, areas that are otherwise resistant to direct study. Keeping this in mind, the primary goal of this chapter is to illustrate how geochemical data can be used both to assess the origin of these rocks and to study the evolution of the continental lithosphere.A complete overview of continental basaltic rocks will not be attempted here, because continental "basalts" come in too wide a range of compositions, and because of the sheer volume of geochemical data available for such rocks worldwide. The scope of the chapter is limited to a discussion of a select group of ultramafic to mafic composition "intraplate" continental igneous rocks consisting primarily of kimberlites, potassic and sodic alkali basalts, and continental flood basalts. Igneous rocks forming at active continental margins, such as convergent or transform plate margins, are important examples of continental magmatism but are not directly discussed here (convergent margin magmas are discussed in Chapters 2.11, 3.11, and 3.18). The geochemistry of intraplate igneous rocks of the ocean basins are covered in Chapters 2.04 and 3.16. Although basaltic magmatism has occurred throughout the Earths history, the majority of the examples presented here are from Mesozoic and Cenozoic volcanic fields due to the more complete preservation of younger continental mafic igneous rocks. While considerable effort has been expended in studying the chemical differentiation of mafic magmas

  7. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate.

    PubMed

    de Freitas, Christopher R; Grigorieva, Elena A

    2015-12-01

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This

  8. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate.

    PubMed

    de Freitas, Christopher R; Grigorieva, Elena A

    2015-11-26

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This

  9. Role of Acclimatization in Weather-Related Human Mortality During the Transition Seasons of Autumn and Spring in a Thermally Extreme Mid-Latitude Continental Climate

    PubMed Central

    de Freitas, Christopher R.; Grigorieva, Elena A.

    2015-01-01

    Human mortality is closely related to natural climate-determined levels of thermal environmental stress and the resulting thermophysiological strain. Most climate-mortality research has focused on seasonal extremes during winter and summer when mortality is the highest, while relatively little attention has been paid to mortality during the transitional seasons of autumn and spring. The body acclimatizes to heat in the summer and cold in winter and readjusts through acclimatization during the transitions between the two during which time the body experiences the thermophysiological strain of readjustment. To better understand the influences of weather on mortality through the acclimatization process, the aim here is to examine the periods that link very cold and very warms seasons. The study uses the Acclimatization Thermal Strain Index (ATSI), which is a comparative measure of short-term thermophysiological impact on the body. ATSI centers on heat exchange with the body’s core via the respiratory system, which cannot be protected. The analysis is based on data for a major city in the climatic region of the Russian Far East characterized by very hot summers and extremely cold winters. The results show that although mortality peaks in winter (January) and is at its lowest in summer (August), there is not a smooth rise through autumn nor a smooth decline through spring. A secondary peak occurs in autumn (October) with a smaller jump in May. This suggests the acclimatization from warm-to-cold produces more thermophysiological strain than the transition from cold-to-warm. The study shows that ATSI is a useful metric for quantifying the extent to which biophysical adaptation plays a role in increased strain on the body during re-acclimatization and for this reason is a more appropriate climatic indictor than air temperature alone. The work gives useful bioclimatic information on risks involved in transitional seasons in regions characterized by climatic extremes. This

  10. Applications of a New England stream temperature model to evaluate distribution of thermal regimes and sensitivity to change in riparian condition

    EPA Science Inventory

    We have applied a statistical stream network (SSN) model to predict stream thermal metrics (summer monthly medians, growing season maximum magnitude and timing, and daily rates of change) across New England nontidal streams and rivers, excluding northern Maine watersheds that ext...

  11. Continental drift before 1900.

    PubMed

    Rupke, N A

    1970-07-25

    The idea that Francis Bacon and other seventeenth and eighteenth century thinkers first conceived the notion of continental drift does not stand up to close scrutiny. The few authors who expressed the idea viewed the process as a catastrophic event.

  12. Visco-elastic effects with simultaneous thermal and mass diffusion in MHD free convection flow near an oscillating plate in the slip flow regime

    NASA Astrophysics Data System (ADS)

    Das, Bandita; Choudhury, Rita

    2016-06-01

    The present study analyzes the influence of visco-elastic flow of fluid through a porous medium bounded by an oscillating porous plate with heat source in the slip flow regime. Effects of heat transfer, mass transfer and chemical reaction are also taken into account. The porous plate is subjected to a transverse suction velocity. The dimensionless governing equations of the problem are solved by regular perturbation technique. The analytical expressions for the velocity, temperature, concentration, and Shearing stress have been obtained and illustrated graphically for different values of physical parameters involved in the problem. The investigation reveals that the visco-elastic fluid has significant effects on the considered flow field in comparison with Newtonian fluid flow phenomenon.

  13. The 3-D dynamics of slab break-off and implications for continental collision zones

    NASA Astrophysics Data System (ADS)

    van Hunen, Jeroen; Allen, Mark

    2010-05-01

    Some of the world best studied mountain ranges are a result of continental collision, such as the Himalayas, Zagros mountains, and the Alps. Continental collision forms the last stage of the closure of an oceanic basin, and leads to the slow-down or complete cessation of the subduction process. Previously subducted slab material will experience a period of thermal warming (Gerya et al., 2004) and/or a larger tensile stress, and will eventually weaken, yield and sink into the mantle. This process has potentially important implications for the thermal and stress regime of the overlying convergence zone, and has been held responsible for various phenomena such as late-stage magmatism (Davies and von Blanckenburg, 1995) and surface uplift or depression (van der Meulen et al., 1998, Buiter et al., 2002). Even though the collision process itself is relatively short-lived compared to the preceding oceanic subduction, its remnants are often preserved, and probably provide a valuable window into the plate tectonic process during the Proterozoic and perhaps the Archaean (e.g. Calvert et al., 1995). The three-dimensional nature of this break-off process has previously been discussed with conceptual models. E.g. slab break-off has been suggested to propagate laterally through an advancing tear (Wortel and Spakman, 2000). In this study we present 3D numerical results of the evolution of slab break-off. We focus on the development and evolution of a laterally migrating slab tear, and present results on the sensitivity of this process to the geometry of the closing oceanic basin, the tensile stresses in and the rheological properties of the slab, and the thermal state of the surrounding mantle. By comparing our numerical results to previously published analogue results (Regard et al., 2004) and various tomographic, structural, and magmatic observations of well-studied subduction collision systems, we are able to extract valuable insights in to the dynamics and strength of

  14. Post subduction thermal regime of the western North America and effects on the Great Valley, Sierra Nevada and northern Baja California provinces

    NASA Astrophysics Data System (ADS)

    Erkan, Kamil

    Tectonic evolution of the transform margin of western North America has attracted great interest. This boundary formed as the fault-fault-trench type Mendocino triple junction has moved north. The tectonic transition is expected to have a significant thermal signature because the subduction zones are quite distinct from any other plate boundary zones with their depressed heat flow in the outer arc regions. There is a significant amount of heat flow data in most of California covering the Great Valley and Sierra Nevada regions where were part of the outer arc of the Farallon subduction was located. The heat flow in a very large area covering all over the Great Valley and western Sierra Nevada shows the consistent pattern of a recent subduction. The unique pattern of the heat flow distribution indicates the tectonic origin of the data which has a potential to reveal the nature of the tectonic transition after the cessation of subduction 30 Ma. In this collection, the first two papers deal with the interpretation of heat flow data using forward thermal models of the lithosphere. The two proposed tectonic scenarios, namely the slab window and the stalled slab models, were compared in terms of the thermal consequences. The low heat flow in the Great Valley and the narrow transition zone toward the Coast Ranges rules out opening of a slab window in a conventional sense and is therefore indicative of a stalled slab type transition. Therefore, the high heat flow in the Coast Ranges must be explained by a mechanism other than opening of a slab window beneath the Coast Ranges. The low (reduced) heat flow in the Western Sierra Nevada which extends to the south end of the region where the subduction ceased more than 15 My ago is important in understating the thermal history of the lithosphere after the cessation of subduction. The thermal data are also in close agreement with the seismic cut-out depth where sufficient seismic activity is present. The numerical thermal model of

  15. RECIPES FOR WRITING ALGORITHMS FOR ATMOSPHERIC CORRECTIONS AND TEMPERATURE/EMISSIVITY SEPARATIONS IN THE THERMAL REGIME FOR A MULTI-SPECTRAL SENSOR

    SciTech Connect

    C. BOREL; W. CLODIUS

    2001-04-01

    This paper discusses the algorithms created for the Multi-spectral Thermal Imager (MTI) to retrieve temperatures and emissivities. Recipes to create the physics based water temperature retrieval, emissivity of water surfaces are described. A simple radiative transfer model for multi-spectral sensors is developed. A method to create look-up-tables and the criterion of finding the optimum water temperature are covered. Practical aspects such as conversion from band-averaged radiances to brightness temperatures and effects of variations in the spectral response on the atmospheric transmission are discussed. A recipe for a temperature/emissivity separation algorithm when water surfaces are present is given. Results of retrievals of skin water temperatures are compared with in-situ measurements of the bulk water temperature at two locations are shown.

  16. Continental drift before 1900.

    PubMed

    Rupke, N A

    1970-07-25

    The idea that Francis Bacon and other seventeenth and eighteenth century thinkers first conceived the notion of continental drift does not stand up to close scrutiny. The few authors who expressed the idea viewed the process as a catastrophic event. PMID:16057953

  17. The Continental Crust.

    ERIC Educational Resources Information Center

    Burchfiel, B. Clark

    1983-01-01

    Continental crust underlies the continents, their margins, and also small shallow regions in oceans. The nature of the crust (much older than oceanic crust) and its dynamics are discussed. Research related to and effects of tectonics, volcanism, erosion, and sedimentation on the crust are considered. (JN)

  18. Continental Flood Basalts

    NASA Astrophysics Data System (ADS)

    Continental flood basalts have been receiving considerable scientific attention lately. Recent publications have focused on several particular flood-basalt provinces (Brito-Arctic, Karoo, Parana', Deccan, and Columbia Plateau), and much attention has been given to the proposed connection between flood-basalt volcanism, bolide impacts, and mass extinctions. The editor of Continental Flood Basalts, J. D. Macdougall, conceived the book to assemble in a single volume, from a vast and scattered literature, an overview of each major post-Cambrian flood-basalt province.Continental Flood Basalts has 10 chapters; nine treat individual flood-basalt provinces, and a summary chapter compares and contrasts continental flood-basalts and mid-oceanic ridge basalts. Specifically, the chapters address the Columbia River basalt, the northwest United States including the Columbia River basalt, the Ethiopian Province, the North Atlantic Tertiary Province, the Deccan Traps, the Parana' Basin, the Karoo Province, the Siberian Platform, and Cenozoic basaltic rocks in eastern China. Each chapter is written by one or more individuals with an extensive background in the province.

  19. Effects of storm runoff on the thermal regime and water quality of a deep, stratified reservoir in a temperate monsoon zone, in Northwest China.

    PubMed

    Huang, Tinglin; Li, Xuan; Rijnaarts, Huub; Grotenhuis, Tim; Ma, Weixing; Sun, Xin; Xu, Jinlan

    2014-07-01

    Jinpen Reservoir is a deep, stratified reservoir in Shaanxi province, located in a warm temperate zone of Northwest China. Influenced by a temperate monsoon climate, more than 60% of the annual precipitation is concentrated from late summer to autumn (July-September). In recent years, extreme rainfall events occurred more frequently and strongly affected the thermal structure, mixing layer depth and evolution of stratification of Jinpen Reservoir. The reservoir's inflow volume increased sharply after heavy rainfall during the flooding season. Large volumes of inflow induced mixing of stratified water zones in early autumn and disturbed the stratification significantly. A temporary positive effect of such disturbance was the oxygenation of the water close to the bottom of the reservoir, leading to inhibition of the release of nutrients from sediments, especially phosphate. However, the massive inflow induced by storm runoff with increased oxygen-consuming substances led to an increase of the oxygen consumption rate. After the bottom water became anaerobic again, the bottom water quality would deteriorate due to the release of pollutants from sediments. Heavy rainfall events could lead to very high nutrient input into the reservoir due to massive erosion from the surrounding uninhabited steep mountains, and the particulate matter contributed to most nutrient inputs. Reasonably releasing density flow is an effective way to reduce the amounts of particulate associated pollutants entering the reservoir. Significant turbid density flow always followed high rainfall events in Jinpen Reservoir, which not only affected the reservoir water quality but also increased costs of the drinking water treatment plant. Understanding the effects of the storm runoff on the vertical distributions of water quality indicators could help water managers to select the proper position of the intake for the water plant in order to avoid high turbidity outflow.

  20. Salton Sea Geothermal Field, Imperial Valley, California as a site for continental scientific drilling. [Abstract only

    SciTech Connect

    Elders, W.A.; Cohen, L.H.

    1983-03-01

    The Salton Trough, where seafloor spreading systems of the East Pacific Rise transition into the San Andreas transform fault system, is the site of such continental rifting and basin formation today. The largest thermal anomaly in the trough, the Salton Sea Geothermal Field (SSGF), is of interest to both thermal regimes and mineral resources investigators. At this site, temperatures >350/sup 0/C and metal-rich brines with 250,000 mg/L TDS have been encountered at <2 km depth. Republic Geothermal Inc. will drill a new well to 3.7 km in the SSGF early in 1983; we propose add-on experiments in it. If funded, we will obtain selective water and core samples and a large-diameter casing installed to 3.7 km will permit later deepening. In Phase 2, the well would be continuously cored to 5.5 km and be available for scientific studies until July 1985. The deepened well would encounter hydrothermal regimes of temperature and pressure never before sampled.

  1. Continental rifting - Progress and outlook

    NASA Technical Reports Server (NTRS)

    Baker, B. H.; Morgan, P.

    1981-01-01

    It is noted that in spite of the flood of new data on continental rifts in the last 15 years, there is little consensus about the basic mechanisms and causes of rifting. The remarkable similarities in rift cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of rifts is more dependent on lithosphere properties than the mode of rifting. It is thought that there is a spectrum of rifting processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides rifts into two basic categories: active rifting and passive rifting. Here, the magnitude of active rifting will depend on the rate at which lithosphere moves over the thermal source, with rifts being restricted to stationary or slow-moving plates.

  2. Ductile deformation of the continental crust below volcanic and non-volcanic passive margins: insight from high quality industrial seismic profiles

    NASA Astrophysics Data System (ADS)

    Clerc, Camille; Jolivet, Laurent; Ringenbach, Jean-Claude; Ballard, Jean-François

    2015-04-01

    High quality industrial seismic profiles have now been acquired along most of the world's passive margins. Stunningly increasing resolution over the past decades leads to unravel unexpected structures and to see real images of models drawn from the integration of field data. Some profiles show clear indications of ductile deformation of the deep continental crust, more or less localized along large-scale shallow-dipping shear zones. Maximums of deformation are suggested at the very base of the continental crust, and the Moho appears to be strongly sheared. These shear zones show a top-to-the-continent sense of shear consistent with the activity of counter-regional (continentward) normal faults observed in the upper crust. This pattern is responsible for a migration of the deformation and associated sedimentation or volcanic activity toward the ocean. We present some of the most striking examples and discuss their implications for the time-temperature-subsidence history of the margins. The distal domain of the non-magmatic margins is generally represented with an important sag basin (i.e. West African margins). This kind of sag basin is usually described as a vertically subsiding basin without differential tilting and resting on a highly thinned, little faulted continental crust. In contrast, we present new interpretations of seismic profiles across the West African margins showing evidences of intense syn-sedimentary tectonic activity within the Sag-basin. Sequences of low-angle normal faults horizontalizing in a hyper-stretched and ductile continental crust control a migration of the depot-center toward the ocean, in response to the horizontal extraction of the base of the continental crust and upper mantle. Finally, the hyper-thinned continental crust has undergone a ductile stretching under a cover of early syn-rift sediments, which implies a probable high thermal regime during rifting.

  3. Polar continental margins: Studies off East Greenland

    NASA Astrophysics Data System (ADS)

    Mienert, J.; Thiede, J.; Kenyon, N. H.; Hollender, F.-J.

    The passive continental margin off east Greenland has been shaped by tectonic and sedimentary processes, and typical physiographic patterns have evolved over the past few million years under the influence of the late Cenozoic Northern Hemisphere glaciations. The Greenland ice shield has been particularly affected.GLORIA (Geological Long Range Inclined Asdic), the Institute of Oceanographic Sciences' (IOS) long-range, side-scan sonar, was used on a 1992 RV Livonia cruise to map large-scale changes in sedimentary patterns along the east Greenland continental margin. The overall objective of this research program was to determine the variety of large-scale seafloor processes to improve our understanding of the interaction between ice sheets, current regimes, and sedimentary processes. In cooperation with IOS and the RV Livonia, a high-quality set of seafloor data has been produced. GLORIA'S first survey of east Greenland's continental margin covered several 1000- × 50-km-wide swaths (Figure 1) and yielded an impressive sidescan sonar image of the complete Greenland Basin and margin (about 250,000 km2). A mosaic of the data was made at a scale of 1:375,000. The base map was prepared with a polar stereographic projection having a standard parallel of 71°.

  4. Fission track analysis, rift shoulder uplift, and tectonic modeling of the Norwegian Continental Margin

    SciTech Connect

    Andriessen, P.; Van Der Beek, P.; Cloetingh, S.; Rohrman, M. )

    1993-09-01

    Apatite fission track analysis from southern Norway and Sweden, across the Permian Carboniferous Oslo rift, are presented and discussed in relation to different rifting scenarios. Vertical and horizontal apatite fission tack profiles in middle and southern Norway unravel the post-Carboniferous history of the Fennoscandian shield. Fission track apatite ages range from 240 Ma in the south to 160 Ma in the north, and according to spontaneous fission track length measurements, they must be interpreted as mixed ages, indicating minor amounts of Paleozoic-Mesozoic sedimentary cover. Apatite fission track length and age modeling suggest rapid cooling and uplift in the Tertiary for the southernmost part of Norway, suggesting a differential uplift of the basement. the obtained data are important for the reconstruction of burial and thermal histories of Cenozoic sedimentary basins of the Norwegian continental margin in the northern North Sea, where diverse rifting events, intraplate stress regimes, and inversion tectonics are involved. Fission track analysis puts constraints on tectonic modeling of uplift of rift flanks and the Norwegian continental margin and yields information for these assessment of hydrocarbon potentials of the sedimentary basins.

  5. Moroccan crustal response to continental drift.

    PubMed

    Kanes, W H; Saadi, M; Ehrlich, E; Alem, A

    1973-06-01

    The formation and development of a zone of spreading beneath the continental crust resulted in the breakup of Pangea and formation of the Atlantic Ocean. The crust of Morocco bears an extremely complete record of the crustal response to this episode of mantle dynamics. Structural and related depositional patterns indicate that the African margin had stabilized by the Middle Jurassic as a marine carbonate environment; that it was dominated by tensile stresses in the early Mesozoic, resulting in two fault systems paralleling the Atlantic and Mediterranean margins and a basin and range structural-depositional style; and that it was affected by late Paleozoic metamorphism and intrusion. Mesozoic events record the latter portion of African involvement in the spreading episode; late Paleozoic thermal orogenesis might reflect the earlier events in the initiation of the spreading center and its development beneath significant continental crust. In that case, more than 100 million years were required for mantle dynamics to break up Pangea.

  6. Moroccan crustal response to continental drift.

    PubMed

    Kanes, W H; Saadi, M; Ehrlich, E; Alem, A

    1973-06-01

    The formation and development of a zone of spreading beneath the continental crust resulted in the breakup of Pangea and formation of the Atlantic Ocean. The crust of Morocco bears an extremely complete record of the crustal response to this episode of mantle dynamics. Structural and related depositional patterns indicate that the African margin had stabilized by the Middle Jurassic as a marine carbonate environment; that it was dominated by tensile stresses in the early Mesozoic, resulting in two fault systems paralleling the Atlantic and Mediterranean margins and a basin and range structural-depositional style; and that it was affected by late Paleozoic metamorphism and intrusion. Mesozoic events record the latter portion of African involvement in the spreading episode; late Paleozoic thermal orogenesis might reflect the earlier events in the initiation of the spreading center and its development beneath significant continental crust. In that case, more than 100 million years were required for mantle dynamics to break up Pangea. PMID:17735922

  7. The Brazilian continental margin

    NASA Astrophysics Data System (ADS)

    Martins, L. R.; Coutinho, P. N.

    1981-04-01

    The Brazilian continental margin, with its interesting morphology, structure and sediments, has become better known only during the last two decades. Six physiographical provinces can be recognized at the continental margin and the adjacent coast: (1) Cabo Orange-Parnaiba delta; (2) Parnaiba delta-Cabo Sa˜o Roque; (3) Cabo Sa˜o Roque-Belmonte; (4) Belmonte-Cabo Frio; (5) Cabo Frio-Cabo Santa Marta; and (6) Cabo Santa Marta-Chui. The shelf is rather wide near the Amazon Mouth, becoming narrower eastwards, continuing very narrow along the northeastern and eastern coast, and becoming wider again in the south towards the Plate River. Prominent morphological features along the margin are the Amazon cone, the marginal plateaus off northeastern Brazil, the Sa˜o Francisco cone and canyon, the Abrolhos Bank, and the deep-sea plateaus of Pernambuco and Sa˜o Paulo. On the shelf proper a number of relief elements exist, such as sand waves east of the Amazon, submarine terraces at various places, and irregularities of structural origin. The shelf break is rather smooth in the far north and south, more abrupt in the remainder. Surface sediments of the Brazilian shelf show five distinct facies types: littoral quartz sands, mud, transition sand-mud, coralline algae, and biodetrital. The terrigenous elastic fractions dominate off the Amazon and in southern Brazil; between these areas they occupy a very narrow strip near the coast. The carbonate facies, predominantly composed of calcareous algae, is abundant between the Parnaiba delta and Cabo Frio; to the south this facies is more biodetrital and restricted to the outer shelf. Economically important on the Brazilian continental margin besides oil, are sands and gravels, carbonate deposits, evaporites and some subsurface coal. Other possible mineral resources could be phosphate, heavy minerals and clays for ceramics.

  8. Permafrost and the geothermal regime

    NASA Astrophysics Data System (ADS)

    Lachenbruch, A. H.; Marshall, B. V.

    Permafrost is the region in the solid earth where the temperature is below 0 C summer and winter. Within this region, water usually occurs as ice, often in massive segregated forms, although capillary water, brines, and gas hydrates also occur. The frozen condition renders permafrost impermeable to water flow, subject to brittle fracture under seasonally induced thermal stress, and subject to mechanical failure and flow when thawed by natural processes or disturbed by man. Hence an understanding of the factors controlling the geothermal regime is necessary for an understanding of geomorphic processes and for successful design of engineering structures such as roadways, heated buildings, pipelines, and oil wells in permafrost terrains. Studies of these factors are greatly simplified by the general absence of heat transfer by flowing ground water; temperatures are estimated with confidence from heat-conduction theory if the ground surface temperature, regional heat flow, and thermal properties are known.

  9. A Regime Diagram for Subduction

    NASA Astrophysics Data System (ADS)

    Stegman, D. R.; Farrington, R.; Capitanio, F. A.; Schellart, W. P.

    2009-12-01

    Regime diagrams and associated scaling relations have profoundly influenced our understanding of planetary dynamics. Previous regime diagrams characterized the regimes of stagnant-lid, small viscosity contrast, transitional, and no-convection for temperature-dependent (Moresi and Solomatov, 1995), and non-linear power law rheologies (Solomatov and Moresi, 1997) as well as stagnant-lid, sluggish-lid, and mobile-lid regimes once the finite strength of rock was considered (Moresi and Solomatov, 1998). Scalings derived from such models have been the cornerstone for parameterized models of thermal evolution of rocky planets and icy moons for the past decade. While such a theory can predict the tectonic state of a planetary body, it is still rather incomplete in regards to predicting tectonics. For example, the mobile-lid regime is unspecific as to how continuous lithospheric recycling should occur on a terrestrial planet. Towards this goal, Gerya et al., (2008) advanced a new regime diagram aiming to characterize when subduction would manifest itself as a one-sided or two-sided downwelling and either symmetric or asymmetric. Here, we present a regime diagram for the case of a single-sided, asymmetric type of subduction (most Earth-like type). Using a 3-D numerical model of a free subduction, we describe a total of 5 different styles of subduction that can possibly occur. Each style is distinguished by its upper mantle slab morphology resulting from the sinking kinematics. We provide movies to illustrate the different styles and their progressive time-evolution. In each regime, subduction is accommodated by a combination of plate advance and slab rollback, with associated motions of forward plate velocity and trench retreat, respectively. We demonstrate that the preferred subduction mode depends upon two essential controlling factors: 1) buoyancy of the downgoing plate and 2) strength of plate in resisting bending at the hinge. We propose that a variety of subduction

  10. Subduction-driven recycling of continental margin lithosphere.

    PubMed

    Levander, A; Bezada, M J; Niu, F; Humphreys, E D; Palomeras, I; Thurner, S M; Masy, J; Schmitz, M; Gallart, J; Carbonell, R; Miller, M S

    2014-11-13

    Whereas subduction recycling of oceanic lithosphere is one of the central themes of plate tectonics, the recycling of continental lithosphere appears to be far more complicated and less well understood. Delamination and convective downwelling are two widely recognized processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts. Here we relate oceanic plate subduction to removal of adjacent continental lithosphere in certain plate tectonic settings. We have developed teleseismic body wave images from dense broadband seismic experiments that show higher than expected volumes of anomalously fast mantle associated with the subducted Atlantic slab under northeastern South America and the Alboran slab beneath the Gibraltar arc region; the anomalies are under, and are aligned with, the continental margins at depths greater than 200 kilometres. Rayleigh wave analysis finds that the lithospheric mantle under the continental margins is significantly thinner than expected, and that thin lithosphere extends from the orogens adjacent to the subduction zones inland to the edges of nearby cratonic cores. Taking these data together, here we describe a process that can lead to the loss of continental lithosphere adjacent to a subduction zone. Subducting oceanic plates can viscously entrain and remove the bottom of the continental thermal boundary layer lithosphere from adjacent continental margins. This drives surface tectonics and pre-conditions the margins for further deformation by creating topography along the lithosphere-asthenosphere boundary. This can lead to development of secondary downwellings under the continental interior, probably under both South America and the Gibraltar arc, and to delamination of the entire lithospheric mantle, as around the Gibraltar arc. This process reconciles numerous, sometimes mutually exclusive, geodynamic models proposed to explain the complex oceanic-continental tectonics of these subduction zones

  11. Subduction-driven recycling of continental margin lithosphere.

    PubMed

    Levander, A; Bezada, M J; Niu, F; Humphreys, E D; Palomeras, I; Thurner, S M; Masy, J; Schmitz, M; Gallart, J; Carbonell, R; Miller, M S

    2014-11-13

    Whereas subduction recycling of oceanic lithosphere is one of the central themes of plate tectonics, the recycling of continental lithosphere appears to be far more complicated and less well understood. Delamination and convective downwelling are two widely recognized processes invoked to explain the removal of lithospheric mantle under or adjacent to orogenic belts. Here we relate oceanic plate subduction to removal of adjacent continental lithosphere in certain plate tectonic settings. We have developed teleseismic body wave images from dense broadband seismic experiments that show higher than expected volumes of anomalously fast mantle associated with the subducted Atlantic slab under northeastern South America and the Alboran slab beneath the Gibraltar arc region; the anomalies are under, and are aligned with, the continental margins at depths greater than 200 kilometres. Rayleigh wave analysis finds that the lithospheric mantle under the continental margins is significantly thinner than expected, and that thin lithosphere extends from the orogens adjacent to the subduction zones inland to the edges of nearby cratonic cores. Taking these data together, here we describe a process that can lead to the loss of continental lithosphere adjacent to a subduction zone. Subducting oceanic plates can viscously entrain and remove the bottom of the continental thermal boundary layer lithosphere from adjacent continental margins. This drives surface tectonics and pre-conditions the margins for further deformation by creating topography along the lithosphere-asthenosphere boundary. This can lead to development of secondary downwellings under the continental interior, probably under both South America and the Gibraltar arc, and to delamination of the entire lithospheric mantle, as around the Gibraltar arc. This process reconciles numerous, sometimes mutually exclusive, geodynamic models proposed to explain the complex oceanic-continental tectonics of these subduction zones.

  12. Finite-element models of continental extension

    NASA Technical Reports Server (NTRS)

    Lynch, H. David; Morgan, Paul

    1990-01-01

    Numerical models of the initial deformation of extending continental lithosphere, computed to investigate the control of preexisting thermal and mechanical heterogeneities on the style of deformation, are presented. The finite element method is used to calculate deformation with a viscoelastic-plastic model for the lithosphere. Comparisons of the results of analytic models and finite-element models using this method show that good results may be obtained by the numerical technique, even with elements containing both brittle and viscoelastic sampling points. It is shown that the gross style of initial extensional deformation is controlled by the depth and width of the initial heterogeneity which localizes deformation.

  13. Anorthosite belts, continental drift, and the anorthosite event.

    PubMed

    Herz, N

    1969-05-23

    Most anorthosites lie in two principal belts when plotted on a predrift continental reconstruction. Anorthosite ages in the belts cluster around 1300 +/- 200 million years and range from 1100 to 1700 million years. This suggests that anorthosites are the product of a unique cataclysmic event or a thermal event that was normal only during the earth's early history. PMID:17775597

  14. Anorthosite belts, continental drift, and the anorthosite event.

    PubMed

    Herz, N

    1969-05-23

    Most anorthosites lie in two principal belts when plotted on a predrift continental reconstruction. Anorthosite ages in the belts cluster around 1300 +/- 200 million years and range from 1100 to 1700 million years. This suggests that anorthosites are the product of a unique cataclysmic event or a thermal event that was normal only during the earth's early history.

  15. Anorthosite belts, continental drift, and the anorthosite event

    USGS Publications Warehouse

    Herz, N.

    1969-01-01

    Most anorthosites lie in two principal belts when plotted on a predrift continental reconstruction. Anorthosite ages in the belts cluster around 1300 ?? 200 million years and range from 1100 to 1700 million years. This suggests that anorthosites are the product of a unique cataclysmic event or a thermal event that was normal only during the earth's early history.

  16. NSF Continental Lithosphere Program

    NASA Astrophysics Data System (ADS)

    Mayhew, Michael; MacGregor, Ian

    For several months the Continental Lithosphere Program (CL) of the National Science Foundation has been subject to a major review. The process was stimulated by a series of budget setbacks over the past few years. Although Presidential budget requests have been very favorable for the Division of Earth Sciences (EAR), and there has been strong support within the National Science Foundation and Congress, actual appropriations by Congress have been disappointing.In each year the final allocation to EAR has been affected by external factors beyond the control of the Foundation. In the four fiscal years from 1986 through 1989 the factors include reductions tied to the Gramm-Rudman deficit reduction measures, congressional reaction to the October 1987 stock market crash, and two years of protection for the Ocean Sciences part of the NSF budget that was paid for from the budgets of the Atmospheric and Earth Sciences divisions.

  17. Cascading Off Continental Shelves

    NASA Astrophysics Data System (ADS)

    Huthnance, J.

    Cascading is the motion of dense water that is formed by cooling, evaporation or freezing in the surface layer, along a sloping sea bottom to a greater depth. It is in- fluential in water-mass formation and particularly in ventilation of intermediate and abyssal layers, hence affecting thermohaline circulation and global climate. Cascad- ing is intermittent in time and space, takes place in the bottom layers and cannot be traced via satellites. Hence it is rarely observed while in progress, and there is a dearth of knowledge of the statistical and main individual characteristics of cascading: most favourable locations, frequency of occurrence, density difference, speed of sinking, off-shore volume fluxes etc. The INTAS 99-1600 project "Dense water overflows off continental shelves (cascading)" aims to (i) improve understanding and modelling of dense water overflows, ie. cascading as a meso-scale process (ii) extrapolate from spe- cific observations (focused on the edge of the continental shelf) using generic models and (iii) estimate its influence on fluxes of dissolved and particulate matter between the shelf and open ocean in the bottom boundary layer. An overview of the project to date will be given: - collation of existing confirmed observations of cascading, and data of relevant laboratory experiments, to provide a common data base for modelling; - search of oceanographic data banks and collation of wider relevant data; - systematic analysis; inter-comparison, identifying factors and mechanisms in pre-conditioning, initiation, the evolving form and the end-stages of dense water overflow. - developing a linked set of new or modified models (1.5-layer to 3-D full-physics) capable of sim- ulating the main driving mechanisms and predicting the characteristics of cascading; - developing a model to study the generation and movement of mudslides that the cas- cading process can trigger if sediment material becomes unstable over a steep bottom slope.

  18. Stable Continental Region Earthquakes in South China

    NASA Astrophysics Data System (ADS)

    Liu, L.

    This paper reviews some remarkable characteristics of earthquakes in a Stable Continental Region (SCR) of the South China Block (SCB). The kernel of the SCB is the Yangtze platform solidified in late Proterozoic time, with continental growth to the southeast by a series of fold belts in Paleozoic time. The facts that the deviatoric stress is low, the orientations of the major tectonic features in the SCB are substantially normal to the maximum horizontal principal stress, and a relatively uniform crust, seem to be the major reasons for lack of significant seismicity in most regions of the SCB. Earthquakes in this region are mainly associated with three seismic zones: (1) the Southeast China Coast seismic zone related to Guangdong-Fujian coastal folding belt (associated with Eurasia-Philippine Sea plate collision); (2) the Southern Yellow Sea seismic zone associated with continental shelf rifts and basins; and (3) the Downstream Yangtze River seismic zone spatially coinciding with Tertiary rifts and basin development. All three seismic zones are close to one or two major economic and population centers in the SCB so that they pose significant seismic hazards. Earthquake focal mechanisms in the SCB are consistent with strike-slip to normal faulting stress regimes. Because of the global and national economic significance of the SCB and its dense population, the seismic hazard of the region is of outstanding importance. Comparing the SCB with another less developed region, a pending earthquake with the same size and tectonic setting would cause substantially more severe social and economic losses in the SCB. This paper also compiles an inventory of historic moderate to great earthquakes in the SCB; most of the data are not widely available in English literature.

  19. The thermal conditions of Venus

    NASA Technical Reports Server (NTRS)

    Zharkov, Vladimir N.; Solomatov, V. S.

    1991-01-01

    Models of Venus' thermal evolution are examined. The following subject areas are covered: (1) modified approximation of parameterized convection; (2) description of the model; (3) numerical results and asymptotic solution of the MAPC equations; (4) magnetism and the thermal regime of the cores of Earth and Venus; and (5) the thermal regime of the Venusian crust.

  20. Extreme Temperature Regimes during the Cool Season and their Associated Large-Scale Circulations

    NASA Astrophysics Data System (ADS)

    Xie, Z.

    2015-12-01

    In the cool season (November-March), extreme temperature events (ETEs) always hit the continental United States (US) and provide significant societal impacts. According to the anomalous amplitudes of the surface air temperature (SAT), there are two typical types of ETEs, e.g. cold waves (CWs) and warm waves (WWs). This study used cluster analysis to categorize both CWs and WWs into four distinct regimes respectively and investigated their associated large-scale circulations on intra-seasonal time scale. Most of the CW regimes have large areal impact over the continental US. However, the distribution of cold SAT anomalies varies apparently in four regimes. In the sea level, the four CW regimes are characterized by anomalous high pressure over North America (near and to west of cold anomaly) with different extension and orientation. As a result, anomalous northerlies along east flank of anomalous high pressure convey cold air into the continental US. To the middle troposphere, the leading two groups feature large-scale and zonally-elongated circulation anomaly pattern, while the other two regimes exhibit synoptic wavetrain pattern with meridionally elongated features. As for the WW regimes, there are some patterns symmetry and anti-symmetry with respect to CW regimes. The WW regimes are characterized by anomalous low pressure and southerlies wind over North America. The first and fourth groups are affected by remote forcing emanating from North Pacific, while the others appear mainly locally forced.

  1. Early mantle differentiation and its thermal consequences

    SciTech Connect

    Galer, S.J.G. Max-Planck-Institut fuer Chemie, Mainz ); Goldstein, S.L. )

    1991-01-01

    Initial positive {epsilon}{sub Nd} values of early Archean continental crust imply derivation from depleted mantle sources. A balancing enriched region is therefore required to exist contemporaneously somewhere on the Earth during the early Archean. It is shown that the enriched reservoir must contain a large proportion ({approximately}30-70%) of the total Nd budget of the differentiated system, even it is was formed only shortly after the accretion of the Earth. This amount of Nd is comparable to or greater than the present-day continental inventory relative to the upper mantle. If this enriched reservoir was continental crust, the small proportion of surviving early Archean continent requires that nearly all of it was destroyed. However, surviving Archean metasediments and granites, in general, have primitive or depleted initial Sr and Nd isotopic compositions, and this does not suggest the existence of a large continental crust at this time. Therefore, there is considerable difficulty reconciling this with a plate tectonic regime in which isentropic melting due to plate spreading occurred to the near surface. The authors propose that no significant plate spreading occurred. In this case, an alkalic crust of basalt would be produced because any isentropic melting in the mantle would be of much more limited extent than occurs beneath ocean ridges. A crust built up serially in this way, rather than laterally, appears the most likely candidate for the enriched reservoir balancing the positive {epsilon}{sub Nd} values of the depleted mantle in the early to middle Archean. The existence of such a layer has important implications for the thermal and tectonic history of the Earth.

  2. Arctic circulation regimes.

    PubMed

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  3. Arctic circulation regimes

    PubMed Central

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

    2015-01-01

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  4. Stratigraphic Modelling of Continental Rifting

    NASA Astrophysics Data System (ADS)

    Mondy, Luke; Duclaux, Guillaume; Salles, Tristan; Thomas, Charmaine; Rey, Patrice

    2013-04-01

    Interlinks between deformation and sedimentation have long been recognised as an important factor in the evolution of continental rifts and basins development. However, determining the relative impact of tectonic and climatic forcing on the dynamics of these systems remains a major challenge. This problem in part derives from a lack of modelling tools capable of simulated high detailed surface processes within a large scale (spatially and temporally) tectonic setting. To overcome this issue an innovative framework has been designed using two existing numerical forward modelling codes: Underworld, capable of simulating 3D self-consistent tectonic and thermal lithospheric processes, and Tellus, a forward stratigraphic and geomorphic modelling framework dedicated to simulating highly detailed surface dynamics. The coupling framework enables Tellus to use Underworld outputs as internal and boundary conditions, thereby simulating the stratigraphic and geomorphic evolution of a realistic, active tectonic setting. The resulting models can provide high-resolution data on the stratigraphic record, grain-size variations, sediment provenance, fluvial hydrometric, and landscape evolution. Here we illustrate a one-way coupling method between active tectonics and surface processes in an example of 3D oblique rifting. Our coupled model enables us to visualise the distribution of sediment sources and sinks, and their evolution through time. From this we can extract and analyse at each simulation timestep the stratigraphic record anywhere within the model domain. We find that even from a generic oblique rift model, complex fluvial-deltaic and basin filling dynamics emerge. By isolating the tectonic activity from landscape dynamics with this one-way coupling, we are able to investigate the influence of changes in climate or geomorphic parameters on the sedimentary and landscape record. These impacts can be quantified in part via model post-processing to derive both instantaneous and

  5. Palaeomagnetism and the continental crust

    SciTech Connect

    Piper, J.D.A.

    1987-01-01

    This book is an introduction to palaeomagnetism offering treatment of theory and practice. It analyzes the palaeomagnetic record over the whole of geological time, from the Archaean to the Cenozoic, and goes on to examine the impact of past geometries and movements of the continental crust at each geological stage. Topics covered include theory of rock and mineral magnetism, field and laboratory methods, growth and consolidation of the continental crust in Archaean and Proterozoic times, Palaeozoic palaeomagnetism and the formation of Pangaea, the geomagnetic fields, continental movements, configurations and mantle convection.

  6. Dynamics of Continental Accretion

    NASA Astrophysics Data System (ADS)

    Moresi, L. N.; Betts, P. G.; Miller, M. S.

    2013-12-01

    Subduction zones become congested when they try to swallow buoyant exotic crust. Accretionary mountain belts (orogens) that form at these convergent plate margins are the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North and South American Cordilleras and southwest Pacific. The geologic record is riddled with accretionary orogens, such as the Tasmanides along the eastern margin of the supercontinent Gondwana and the Altaides that formed on the southern margin of Laurasia. Both the modern and ancient examples are characterised by episodic switches between extension and shortening associated with transitions from collision of exotic crust and subduction related rollback. We present three-dimensional dynamic models that show for the first time how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back arc region. The complexity of the morphology and evolution of the system are driven by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonal to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, but infer that this is a global phenomena throughout Earth's evolution.

  7. Dynamics of continental accretion.

    PubMed

    Moresi, L; Betts, P G; Miller, M S; Cayley, R A

    2014-04-10

    Subduction zones become congested when they try to consume buoyant, exotic crust. The accretionary mountain belts (orogens) that form at these convergent plate margins have been the principal sites of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North American Cordilleras and southwest Pacific subduction zones. The geologic record contains abundant accretionary orogens, such as the Tasmanides, along the eastern margin of the supercontinent Gondwana, and the Altaïdes, which formed on the southern margin of Laurasia. In modern and ancient examples of long-lived accretionary orogens, the overriding plate is subjected to episodes of crustal extension and back-arc basin development, often related to subduction rollback and transient episodes of orogenesis and crustal shortening, coincident with accretion of exotic crust. Here we present three-dimensional dynamic models that show how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back-arc region. The complexity of the morphology and the evolution of the system are caused by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonally to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, and infer that this is a recurrent and global phenomenon.

  8. Dynamics of the Precambrian Continental Crust

    NASA Astrophysics Data System (ADS)

    Perchuk, L. L.; Gerya, T. V.; van Reenen, D. D.; Smit, C. A.

    2003-04-01

    The Precambrian continental crust is mainly composed of (1) granite greenstone belts (GGB) and (2) granulite facies complexes (GFC). The GFC are often separated from GGB by inward dipping crustal scale shear zones with characteristic sense of movements reflecting thrusting of GFC onto cratonic rocks. The isotope age of the shear zones is identical to GFC, while the latter are always younger than the granite greenstone belts. The dynamics relationships between these two geological units strongly determine tectonic evolution of the Precambrian continental crust. Numerous thermobarometric studies of magmatic and metamorphic rocks show that the Archaean to Early Protorozoic crust as well as the Mantle were hot and therefore relatively soft. Such geothermal regimes may limit separation and movement of micro continents, limiting collisional mechanisms in evolution of the Precambrian crust. The goal of this paper is to show evidence for an alterative model that is based on the mechanism of gravitational redistribution of rocks within the Precambrian continental crust, which might be initiated by a fluid/heat flow related to mantle plumes. The model is tested on the basis of geological, geochemical, geophysical and petrologic data for many paired GFT GGB complexes around the word. Studied granulite complexes are located in between Archaean GGB from which they are separated by inward dipping crustal scale shear zones with reverse sense of movements. The most important evidence for this mechanism is: (i) the near isobaric cooling (IC) and (ii) decompression cooling (DC) shapes of the retrograde P T paths recorded in GFC, while rocks from the juxtaposed GGB in footwalls of the bounding shear zones record P T loops. The Pmax of the loops corresponds to the Pmin, recorded in GFC. Thus the GGB P T loop reflects the burial and ascending of the juxtaposed GGB while the GFC P T path records the exhumation only. The identical isotopic age of GFC and contacting rocks from the shear

  9. Coordination: Southeast continental shelf studies

    SciTech Connect

    Menzel, D.W.

    1989-01-26

    The objective of this investigation is to obtain model descriptions of the flow modifications in the Southeast Atlantic continental shelf due to Gulf Stream fluctuations and topographic effects. 2 refs., 4 figs.

  10. -induced continental warming

    NASA Astrophysics Data System (ADS)

    Kamae, Youichi; Watanabe, Masahiro; Kimoto, Masahide; Shiogama, Hideo

    2014-11-01

    In this the second of a two-part study, we examine the physical mechanisms responsible for the increasing contrast of the land-sea surface air temperature (SAT) in summertime over the Far East, as observed in recent decades and revealed in future climate projections obtained from a series of transient warming and sensitivity experiments conducted under the umbrella of the Coupled Model Intercomparison Project phase 5. On a global perspective, a strengthening of land-sea SAT contrast in the transient warming simulations of coupled atmosphere-ocean general circulation models is attributed to an increase in sea surface temperature (SST). However, in boreal summer, the strengthened contrast over the Far East is reproduced only by increasing atmospheric CO2 concentration. In response to SST increase alone, the tropospheric warming over the interior of the mid- to high-latitude continents including Eurasia are weaker than those over the surrounding oceans, leading to a weakening of the land-sea SAT contrast over the Far East. Thus, the increasing contrast and associated change in atmospheric circulation over East Asia is explained by CO2-induced continental warming. The degree of strengthening of the land-sea SAT contrast varies in different transient warming scenarios, but is reproduced through a combination of the CO2-induced positive and SST-induced negative contributions to the land-sea contrast. These results imply that changes of climate patterns over the land-ocean boundary regions are sensitive to future scenarios of CO2 concentration pathways including extreme cases.

  11. Fractal behavior in continental crustal heat production

    NASA Astrophysics Data System (ADS)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  12. Rapid vertical tectonics in ductile continental crust

    NASA Astrophysics Data System (ADS)

    Pearse, Jillian

    Research over the past two decades has shown that in regions of moderately high heat flow, the lower continental crust is ductile enough to flow on geological timescales. Vertical motions taking place within continental interiors produce localized features such as intracratonic basins and domes, and the results of this thesis indicate that ductile crustal flow can contribute significantly to the formation of these otherwise enigmatic features. A major goal of this thesis has been to analyze, quantitatively, the behaviour of loaded continental crust where a ductile layer is present. Specifically, I examine the long-term effects of sublithospheric heating events on crust with embedded density loads. Density anomalies within the crust can be initially supported by elastic stresses but sag appreciably if the elastic crust is thinned modestly. Beginning with a semi-analytic approach, I estimate the additional subsidence that would result from thermal reactivation, and introduce the previously unmodelled phenomenon of thermal annealing of stresses at the base of the elastic crust. In basins caused by intracrustal density loads, reactivated subsidence can be significant (of the order of 1 km, enough to account for about one quarter of the total Michigan basin subsidence). If the crust is sufficiently weakened, the long-term result is detachment of the load followed by rebound and inversion of the basin to form a dome. To model this phenomenon I use a full thermal and viscoelastic finite-element model, and find that such load detachment can occur for geologically reasonable load densities in high heat flow regions. Strikingly, the total upward displacement of material from depth during rebound can be as much as 10 km, enough to exhume the basin completely and expose basement rocks to some depth. Exhumation is rapid, lasting only about 5 to 10 million years. This raises the interesting question of what field evidence might support such a history for a dome: the results of

  13. Dynamic Treatment Regimes

    PubMed Central

    Chakraborty, Bibhas; Murphy, Susan A.

    2014-01-01

    A dynamic treatment regime consists of a sequence of decision rules, one per stage of intervention, that dictate how to individualize treatments to patients based on evolving treatment and covariate history. These regimes are particularly useful for managing chronic disorders, and fit well into the larger paradigm of personalized medicine. They provide one way to operationalize a clinical decision support system. Statistics plays a key role in the construction of evidence-based dynamic treatment regimes – informing best study design as well as efficient estimation and valid inference. Due to the many novel methodological challenges it offers, this area has been growing in popularity among statisticians in recent years. In this article, we review the key developments in this exciting field of research. In particular, we discuss the sequential multiple assignment randomized trial designs, estimation techniques like Q-learning and marginal structural models, and several inference techniques designed to address the associated non-standard asymptotics. We reference software, whenever available. We also outline some important future directions. PMID:25401119

  14. Factors controlling depth of continental rift zones

    NASA Astrophysics Data System (ADS)

    Elesin, Y.; Artemieva, I.; Thybo, H.

    2012-04-01

    Subsidence of continental rift basins is caused by thinning of the crust and lithospheric mantle together with isostatic compensation for the extra load of sediments and thermal relaxation. It is generally believed that the final depth of rift basins is primarily controlled by the amount of stretching and that other processes, such as rheology and sedimentation, only have secondary influence. However, we show that the relative rheological strength of faults inside and outside rift zones exerts substantial control on the volume of the final rift basin (by more than a factor of 3) even for the same amount of extension (total or inside the rift zone). This surprising result is mainly caused by irreversible deepening of the rift graben during stretching due to lower crustal flow when the faults in the rift zone are weak, whereas the effect is negligible for strong faults. Relatively strong faults inside the rift zone lead to substantial stretching of adjacent crust, and we find that long term stretching outside the main rift zone may explain the formation of wide continental margins, which are now below sea level. We also demonstrate that fast syn-rift erosion/sedimentation rates can increase the final volume of rift basins by up to a factor of 1.7 for weak crustal faults, whereas this effect is insignificant for strong faults inside the rift zone. These findings have significant implications for estimation of stretching factors, tectonic forces, and geodynamic evolution of sedimentary basins around failed rift zones.

  15. Oceanic and terrestrial sources of continental precipitation

    NASA Astrophysics Data System (ADS)

    Gimeno, Luis; Stohl, Andreas; Trigo, Ricardo M.; Dominguez, Francina; Yoshimura, Kei; Yu, Lisan; Drumond, Anita; DuráN-Quesada, Ana MaríA.; Nieto, Raquel

    2012-12-01

    The most important sources of atmospheric moisture at the global scale are herein identified, both oceanic and terrestrial, and a characterization is made of how continental regions are influenced by water from different moisture source regions. The methods used to establish source-sink relationships of atmospheric water vapor are reviewed, and the advantages and caveats associated with each technique are discussed. The methods described include analytical and box models, numerical water vapor tracers, and physical water vapor tracers (isotopes). In particular, consideration is given to the wide range of recently developed Lagrangian techniques suitable both for evaluating the origin of water that falls during extreme precipitation events and for establishing climatologies of moisture source-sink relationships. As far as oceanic sources are concerned, the important role of the subtropical northern Atlantic Ocean provides moisture for precipitation to the largest continental area, extending from Mexico to parts of Eurasia, and even to the South American continent during the Northern Hemisphere winter. In contrast, the influence of the southern Indian Ocean and North Pacific Ocean sources extends only over smaller continental areas. The South Pacific and the Indian Ocean represent the principal source of moisture for both Australia and Indonesia. Some landmasses only receive moisture from the evaporation that occurs in the same hemisphere (e.g., northern Europe and eastern North America), while others receive moisture from both hemispheres with large seasonal variations (e.g., northern South America). The monsoonal regimes in India, tropical Africa, and North America are provided with moisture from a large number of regions, highlighting the complexities of the global patterns of precipitation. Some very important contributions are also seen from relatively small areas of ocean, such as the Mediterranean Basin (important for Europe and North Africa) and the Red Sea

  16. The northern Egyptian continental margin

    NASA Astrophysics Data System (ADS)

    Badawy, Ahmed; Mohamed, Gad; Omar, Khaled; Farid, Walid

    2015-01-01

    Africa displays a variety of continental margin structures, tectonics and sedimentary records. The northern Egyptian continental margin represents the NE portion of the North African passive continental margin. Economically, this region is of great importance as a very rich and productive hydrocarbon zone in Egypt. Moreover, it is characterized by remarkable tectonic setting accompanied by active tectonic processes from the old Tethys to recent Mediterranean. In this article, seismicity of the northern Egyptian continental margin has been re-evaluated for more than 100-years and the source parameters of three recent earthquakes (October 2012, January 2013 and July 2013) have been estimated. Moment tensor inversions of 19th October 2012 and 17th January 2013 earthquakes reveal normal faulting mechanism with strike-slip component having seismic moment of 3.5E16 N m and 4.3E15 N m respectively. The operation of the Egyptian National Seismic Network (ENSN) since the end of 1997 has significantly enhanced the old picture of earthquake activity across northern Egyptian continental margin whereas; the record-ability (annual rate) has changed from 2-events/year to 54-event/year before and after ENSN respectively. The spatial distribution of earthquakes foci indicated that the activity tends to cluster at three zones: Mediterranean Ridge (MR), Nile Cone (NC) and Eratosthenes Seamount (ERS). However, two seismic gaps are reported along Levant Basin (LEV) and Herodotus Basin (HER).

  17. Convective Regimes in Crystallizing Basaltic Magma Chambers

    NASA Astrophysics Data System (ADS)

    Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.

    2015-12-01

    Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may convect, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible convective modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. Convection in this system is driven thermally, simulating magma convection above and within a porous cumulate pile. We observe a range of possible convective regimes, enabling us to produce a regime diagram. In addition to modes characterised by convection of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by convection in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional convection within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a

  18. The role of structural inheritance in continental rifting

    NASA Astrophysics Data System (ADS)

    Buiter, Susanne; Tetreault, Joya

    2015-04-01

    In nature we observe that passive margins tend to originate on continental collision zones. This is not surprising as continents are long-lived and therefore have undergone multiple deformation phases, producing many regions with inherited structures. Collision zones can act as intrinsic rift-localizers for several reasons: rifting at a suture may be initiated by extensional collapse of the orogen, the thicker crustal root of orogens and their associated increase in heat producing elements makes orogens thermally weak, and inherited thrust faults form large-scale heterogeneities. When investigating continental extension geodynamically, numerical experiments often simplify such inheritance and start from laterally homogeneous crustal layers with a prescribed inhomogeneity that initiates deformation. These inhomogeneities represent thermal or structural remnants from previous deformation phases and are imposed as a thermal anomaly, a variation in Moho geometry, or an inherited weak region. However, imposed initial heterogeneities do not fully capture the structural and thermal complexities of continental sutures. Here we present 2-D numerical experiments that investigate the role of inherited crustal structures in continental rifting and passive margin formation. We first examine a series of experiments in which we explicitly prescribe collisional structures in the initial setup, such as increased Moho depth and inherited thrust faults. Different prescribed collisional structures result in different rift to break-up durations, crustal shear zone patterns, and margin symmetry. Our second series of experiments actually creates an inherited collision zone through subduction and closure of an ocean. We use this set-up to investigate how extension localizes on a former continental collision zone. Passive margin architecture strongly depends on the duration of post-collision thermal equilibration time, with a long pause between collision and initiation of extension

  19. Weighing the deep continental biosphere.

    PubMed

    McMahon, Sean; Parnell, John

    2014-01-01

    There is abundant evidence for widespread microbial activity in deep continental fractures and aquifers, with important implications for biogeochemical cycling on Earth and the habitability of other planetary bodies. Whitman et al. (P Natl Acad Sci USA, 95, 1998, 6578) estimated a continental subsurface biomass on the order of 10(16) -10(17) g C. We reassess this value in the light of more recent data including over 100 microbial population density measurements from groundwater around the world. Making conservative assumptions about cell carbon content and the ratio of attached and free-living microorganisms, we find that the evidence continues to support a deep continental biomass estimate of 10(16) -10(17) g C, or 2-19% of Earth's total biomass.

  20. Continental crust: a geophysical approach

    SciTech Connect

    Meissner, R.

    1986-01-01

    This book develops an integrated and balanced picture of present knowledge of the continental crust. Crust and lithosphere are first defined, and the formation of crusts as a general planetary phenomenon is described. The background and methods of geophysical studies of the earth's crust and the collection of related geophysical parameters are examined. Creep and friction experiments and the various methods of radiometric age dating are addressed, and geophysical and geological investigations of the crustal structure in various age provinces of the continents are studied. Specific tectonic structures such as rifts, continental margins, and geothermal areas are discussed. Finally, an attempt is made to give a comprehensive view of the evolution of the continental crust and to collect and develop arguments for crustal accretion and recycling. 647 references.

  1. Carbonate clumped isotope thermometry in continental tectonics

    NASA Astrophysics Data System (ADS)

    Huntington, Katharine W.; Lechler, Alex R.

    2015-04-01

    Reconstructing the thermal history of minerals and fluids in continental environments is a cornerstone of tectonics research. Paleotemperature constraints from carbonate clumped isotope thermometry have provided important tests of geodynamic, structural, topographic and basin evolution models. The thermometer is based on the 13C-18O bond ordering in carbonates (mass-47 anomaly, Δ47) and provides estimates of the carbonate formation temperature independent of the δ18O value of the water from which the carbonate grew; Δ47 is measured simultaneously with conventional measurements of carbonate δ13C and δ18O values, which together constrain the isotopic composition of the parent water. Depending on the geologic setting of carbonate growth, this information can help constrain paleoenvironmental conditions or basin temperatures and fluid sources. This review examines how clumped isotope thermometry can shed new light on problems in continental tectonics, focusing on paleoaltimetry, basin evolution and structural diagenesis applications. Paleoaltimetry is inherently difficult, and the precision in carbonate growth temperature estimates is at the limit of what is useful for quantitative paleoelevation reconstruction. Nevertheless, clumped isotope analyses have enabled workers to address previously intractable problems and in many settings offer the best chance of understanding topographic change from the geologic record. The portion of the shallow crust residing at temperatures up to ca. 200 °C is important as host to economic resources and records of tectonics and climate, and clumped isotope thermometry is one of the few proxies that can access this critical range with sensitivity to temperature alone. Only a handful of studies to date have used clumped isotopes to investigate diagenesis and other sub-surface processes using carbonate crystallization temperatures or the sensitivity of Δ47 values to a sample's thermal history. However, the thermometer is

  2. Signs of continental rifting in the southwestern Japanese Island Arc

    NASA Astrophysics Data System (ADS)

    Chernysheva, E. A.; Eroshenko, D. V.

    2016-03-01

    The southwestern margin of the Japan Arc evolved in the geodynamic regime of continental rifting during the Miocene-Pleistocene. This has been verified by broad manifestations of metasomatosis of mantle peridotites that underlie the lithosphere of the Japan Islands and by episodes of deep magmatism (kimberlites and melilitites) in the region. The high enrichment of deep melts in incompatible rare and rare earth elements is partially preserved in melts of regional basalts from smaller depths. In contrast, spreading basalts of the Sea of Japan and subduction basalts from the Nankai trench at the boundary with the Philippine Plate are extremely depleted in rare elements.

  3. Non-climatic factors and long-term, continental-scale changes in seasonally frozen ground

    NASA Astrophysics Data System (ADS)

    Shiklomanov, Nikolay I.

    2012-03-01

    ). In their recent paper entitled 'An observational 71-year history of seasonally frozen ground changes in Eurasian high latitudes', Frauenfeld and Zhang (2011) provided detailed analysis of soil temperature data to assess 1930-2000 trends in seasonal freezing depth. The data were obtained from 387 Soviet non-permafrost meteorological stations. The authors performed systematic, quality-controlled, integrative analysis over the entire former Soviet Union domain. The long-term changes in depth of seasonal freezing were discussed in relation to such forcing variables as air temperature, degree days of freezing/thawing, snow depth and summer precipitation as well as modes of the North Atlantic Oscillation. The spatially average approach adopted for the study provides a generalized continental-scale trend. The study greatly improves, expands and extends previous 1956-90 analysis of the ground thermal regime over the Eurasian high latitudes (Frauenfeld et al 2004). Although the work of Frauenfeld and Zhang (2011) is the most comprehensive assessment of the continental-scale long-term trends in seasonal freezing available to date, more detailed analysis is needed to determine the effect of climate change on seasonally frozen ground. It should be noted that, in addition to the variables considered for analysis, other non-climatic factors affect the depth of freezing propagation. Unlike the surface, which is influenced by the climate directly, the ground even at shallow depth receives a climatic signal that is substantially modified by edaphic processes, contributing to highly localized thermal sensitivities of the ground to climatic forcing. Subsurface properties, soil moisture, and snow and vegetation covers influence the depth of freezing. Topography also plays an important role in establishing the ground thermal regime. It is an important determinant of the amount of heat received by the ground surface, affects the distribution of snow and vegetation, and influences the

  4. Estimation of continental precipitation recycling

    SciTech Connect

    Brubaker, K.L.; Entekhabi, D.; Eagleson, P.S. )

    1993-06-01

    The total amount of water that precipitates on large continental regions is supplied by two mechanisms: (1) advection from the surrounding areas external to the region and (2) evaporation and transpiration from the land surface within the region. The latter supply mechanism is tantamount to the recycling of precipitation over the Continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. Gridded data on observed wind and humidity in the global atmosphere are used to determine the convergence of atmospheric water vapor over continental regions. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. The results indicate that the contribution of regional evaporation to regional precipitation varies substantially with location and season. For the regions studied, the ratio of locally contributed to total monthly precipitation generally lies between 0. 10 and 0.30 but is as high as 0.40 in several cases. 48 refs., 7 figs., 4 tabs.

  5. Estimation of continental precipitation recycling

    NASA Technical Reports Server (NTRS)

    Brubaker, Kaye L.; Entekhabi, Dara; Eagleson, P. S.

    1993-01-01

    The total amount of water that precipitates on large continental regions is supplied by two mechanisms: 1) advection from the surrounding areas external to the region and 2) evaporation and transpiration from the land surface within the region. The latter supply mechanism is tantamount to the recycling of precipitation over the continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. Gridded data on observed wind and humidity in the global atmosphere are used to determine the convergence of atmospheric water vapor over continental regions. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. The results indicate that the contribution of regional evaporation to regional precipitation varies substantially with location and season. For the regions studied, the ratio of locally contributed to total monthly precipitation generally lies between 0. 10 and 0.30 but is as high as 0.40 in several cases.

  6. The evolution of oceanic 87Sr/86Sr does not rule out early continental growth

    NASA Astrophysics Data System (ADS)

    Flament, N.; Coltice, N.; Rey, P. F.

    2010-12-01

    evolution of oceanic 87Sr/86Sr is not a suitable proxy for continental growth. We suggest that the delayed appearance of the differentiated reservoir in surface geochemical tracers reflects the emergence of the continents rather than a peak in extraction of juvenile continental crust from the mantle. Therefore, there could be no need for delayed continental growth models. Armstrong, R. L., 1981. Radiogenic isotopes: the case for crustal recycling on a near-steady-state no-continental-growth. Earth. Philos. Trans. R. Soc. London 301, 443-471. Flament, N., Coltice, N., and Rey, P. F., 2008. A case for late-Archaean continental emergence from thermal evolution models and hypsometry. Earth Planet. Sc. Lett. 275, 326-336. Labrosse, S., Jaupart, C., 2007. Thermal evolution of the Earth: Secular changes and fluctuations of plate characteristics. Earth Planet. Sc. Lett. 260, 465-481. Rey, P. F. and Coltice N., 2008. Neoarchean strengthening of the lithosphere and the coupling of the Earth's geochemical reservoirs. Geology 36, 635-638. Taylor, S. R. and McLennan, S. M., 1985. The continental crust: its composition and evolution. Blackwell Scientific Publications, 328 p.

  7. Transform continental margins - part 1: Concepts and models

    NASA Astrophysics Data System (ADS)

    Basile, Christophe

    2015-10-01

    This paper reviews the geodynamic concepts and models related to transform continental margins, and their implications on the structure of these margins. Simple kinematic models of transform faulting associated with continental rifting and oceanic accretion allow to define three successive stages of evolution, including intra-continental transform faulting, active transform margin, and passive transform margin. Each part of the transform margin experiences these three stages, but the evolution is diachronous along the margin. Both the duration of each stage and the cumulated strike-slip deformation increase from one extremity of the margin (inner corner) to the other (outer corner). Initiation of transform faulting is related to the obliquity between the trend of the lithospheric deformed zone and the relative displacement of the lithospheric plates involved in divergence. In this oblique setting, alternating transform and divergent plate boundaries correspond to spatial partitioning of the deformation. Both obliquity and the timing of partitioning influence the shape of transform margins. Oblique margin can be defined when oblique rifting is followed by oblique oceanic accretion. In this case, no transform margin should exist in the prolongation of the oceanic fracture zones. Vertical displacements along transform margins were mainly studied to explain the formation of marginal ridges. Numerous models were proposed, one of the most used is being based on thermal exchanges between the oceanic and the continental lithospheres across the transform fault. But this model is compatible neither with numerical computation including flexural behavior of the lithosphere nor with timing of vertical displacements and the lack of heating related to the passing of the oceanic accretion axis as recorded by the Côte d'Ivoire-Ghana marginal ridge. Enhanced models are still needed. They should better take into account the erosion on the continental slope, and the level of coupling

  8. Non-climatic factors and long-term, continental-scale changes in seasonally frozen ground

    NASA Astrophysics Data System (ADS)

    Shiklomanov, Nikolay I.

    2012-03-01

    ). In their recent paper entitled 'An observational 71-year history of seasonally frozen ground changes in Eurasian high latitudes', Frauenfeld and Zhang (2011) provided detailed analysis of soil temperature data to assess 1930-2000 trends in seasonal freezing depth. The data were obtained from 387 Soviet non-permafrost meteorological stations. The authors performed systematic, quality-controlled, integrative analysis over the entire former Soviet Union domain. The long-term changes in depth of seasonal freezing were discussed in relation to such forcing variables as air temperature, degree days of freezing/thawing, snow depth and summer precipitation as well as modes of the North Atlantic Oscillation. The spatially average approach adopted for the study provides a generalized continental-scale trend. The study greatly improves, expands and extends previous 1956-90 analysis of the ground thermal regime over the Eurasian high latitudes (Frauenfeld et al 2004). Although the work of Frauenfeld and Zhang (2011) is the most comprehensive assessment of the continental-scale long-term trends in seasonal freezing available to date, more detailed analysis is needed to determine the effect of climate change on seasonally frozen ground. It should be noted that, in addition to the variables considered for analysis, other non-climatic factors affect the depth of freezing propagation. Unlike the surface, which is influenced by the climate directly, the ground even at shallow depth receives a climatic signal that is substantially modified by edaphic processes, contributing to highly localized thermal sensitivities of the ground to climatic forcing. Subsurface properties, soil moisture, and snow and vegetation covers influence the depth of freezing. Topography also plays an important role in establishing the ground thermal regime. It is an important determinant of the amount of heat received by the ground surface, affects the distribution of snow and vegetation, and influences the

  9. River Flow Regimes and Effective Discharge

    NASA Astrophysics Data System (ADS)

    Basso, S.; Sprocati, R.; Frascati, A.; Marani, M.; Schirmer, M.; Botter, G.

    2015-12-01

    The concept of effective discharge is widespread in geomorphology and river engineering and restoration. For example, it is used to design the most stable channel configuration, to estimate sedimentation rate and lifespan of reservoirs and to characterize the hydrologic forcing in models studying long-term evolution of rivers. Accordingly, the effective discharge has been the focus of countless empirical, theoretical and numerical studies, which found it to vary among catchments as a function of climate, landscape and river morphology, type of transport (dissolved, suspended or bedload), and of streamflow variability. The heterogeneity of the effective discharge values observed in different catchments challenges a thorough understanding of its pivotal drivers, and a consistent framework which explains observations carried out in different geographic areas is still lacking. In the present work, the observed diversity is explained in terms of the underlying heterogeneity of river flow regimes, by linking effective discharge to attributes of the sediment rating curve and to streamflow variability, as resulting from climatic and landscape drivers. An analytic expression of the effective ratio (i.e. the ratio between effective discharge and mean streamflow) is provided, which captures observed values of effective discharge for suspended sediment transport in a set of catchments of the continental United States. The framework disentangles hydrologic and landscape controls on effective discharge, and highlights distinct effective ratios of persistent and erratic hydrologic regimes (respectively characterized by low and high flow variability), attributable to intrinsically different streamflow dynamics. Clusters of river catchments characterized by similar streamflow dynamics can be identified. The framework provides an opportunity for first-order estimates of effective discharge in rivers belonging to different areas, based on the type of flow regime.

  10. Drift of continental rafts with asymmetric heating.

    PubMed

    Knopoff, L; Poehls, K A; Smith, R C

    1972-06-01

    A laboratory model of a lithospheric raft is propelled through a viscous asthenospheric layer with constant velocity of scaled magnitude appropriate to continental drift. The propulsion is due to differential heat concentration in the model oceanic and continental crusts.

  11. Regimes of turbulence without an energy cascade

    PubMed Central

    Barenghi, C. F.; Sergeev, Y. A.; Baggaley, A. W.

    2016-01-01

    Experiments and numerical simulations of turbulent 4He and 3He-B have established that, at hydrodynamic length scales larger than the average distance between quantum vortices, the energy spectrum obeys the same 5/3 Kolmogorov law which is observed in the homogeneous isotropic turbulence of ordinary fluids. The importance of the 5/3 law is that it points to the existence of a Richardson energy cascade from large eddies to small eddies. However, there is also evidence of quantum turbulent regimes without Kolmogorov scaling. This raises the important questions of why, in such regimes, the Kolmogorov spectrum fails to form, what is the physical nature of turbulence without energy cascade, and whether hydrodynamical models can account for the unusual behaviour of turbulent superfluid helium. In this work we describe simple physical mechanisms which prevent the formation of Kolmogorov scaling in the thermal counterflow, and analyze the conditions necessary for emergence of quasiclassical regime in quantum turbulence generated by injection of vortex rings at low temperatures. Our models justify the hydrodynamical description of quantum turbulence and shed light into an unexpected regime of vortex dynamics. PMID:27761005

  12. Evolution of magma-poor continental margins from rifting to seafloor spreading.

    PubMed

    Whitmarsh, R B; Manatschal, G; Minshull, T A

    2001-09-13

    The rifting of continents involves faulting (tectonism) and magmatism, which reflect the strain-rate and temperature dependent processes of solid-state deformation and decompression melting within the Earth. Most models of this rifting have treated tectonism and magmatism separately, and few numerical simulations have attempted to include continental break-up and melting, let alone describe how continental rifting evolves into seafloor spreading. Models of this evolution conventionally juxtapose continental and oceanic crust. Here we present observations that support the existence of a zone of exhumed continental mantle, several tens of kilometres wide, between oceanic and continental crust on continental margins where magma-poor rifting has taken place. We present geophysical and geological observations from the west Iberia margin, and geological mapping of margins of the former Tethys ocean now exposed in the Alps. We use these complementary findings to propose a conceptual model that focuses on the final stage of continental extension and break-up, and the creation of a zone of exhumed continental mantle that evolves oceanward into seafloor spreading. We conclude that the evolving stress and thermal fields are constrained by a rising and narrowing ridge of asthenospheric mantle, and that magmatism and rates of extension systematically increase oceanward. PMID:11557977

  13. Evolution of magma-poor continental margins from rifting to seafloor spreading.

    PubMed

    Whitmarsh, R B; Manatschal, G; Minshull, T A

    2001-09-13

    The rifting of continents involves faulting (tectonism) and magmatism, which reflect the strain-rate and temperature dependent processes of solid-state deformation and decompression melting within the Earth. Most models of this rifting have treated tectonism and magmatism separately, and few numerical simulations have attempted to include continental break-up and melting, let alone describe how continental rifting evolves into seafloor spreading. Models of this evolution conventionally juxtapose continental and oceanic crust. Here we present observations that support the existence of a zone of exhumed continental mantle, several tens of kilometres wide, between oceanic and continental crust on continental margins where magma-poor rifting has taken place. We present geophysical and geological observations from the west Iberia margin, and geological mapping of margins of the former Tethys ocean now exposed in the Alps. We use these complementary findings to propose a conceptual model that focuses on the final stage of continental extension and break-up, and the creation of a zone of exhumed continental mantle that evolves oceanward into seafloor spreading. We conclude that the evolving stress and thermal fields are constrained by a rising and narrowing ridge of asthenospheric mantle, and that magmatism and rates of extension systematically increase oceanward.

  14. Thinning of Refertilized Sub-Continental Lithospheric Mantle (SLCM) beneath the Main Ethiopian Rift During Tertiary Rifting: Petrologic and Thermal Constraints from (Garnet)-Spinel Peridotite Xenoliths (Mega, Ethiopia).

    NASA Astrophysics Data System (ADS)

    Casagli, A.; Frezzotti, M. L.; Peccerillo, A.; Tiepolo, M.; De Astis, G.

    2014-12-01

    The East African Rift System (EARS) represents a key locality for the knowledge of the nature and evolution of SCLM during continental rifting processes, traditionally ascribed to ascending mantle plumes. We report petrological and geothermobarometric data from mantle xenoliths in Quaternary alkali-basalt lava flows and scoria cones at Mega (Sidamo Region; EARS) in the southern Main Ethiopian Rift (MER), that give evidence for refertilization of SCLM and for thinning during Tertiary rifting. Studied samples consist of seven lherzolites, five harzburgites and one olivine-websterite that contain spinel-pyroxene symplectites, interpreted as products of garnet breakdown reactions. These rocks were analyzed for major (whole rock and minerals) and trace elements (pyroxenes). Major element data have been used to reconstruct original garnet composition (pyrope). Equilibration temperatures range from 985 ± 40°C in the garnet facies (2.9-2.2 GPa) to 960 ± 55°C in the spinel facies (1.3 GPa). Xenoliths consist of depleted and fertile peridotites. Five lherzolites have up to 4 wt% of CaO, high CaO/Al2O3 (1.42-4.46), and the most fertile are more enriched than primitive mantle. Variations of major oxides in bulk rocks and minerals are consistent with variable degrees of melt extraction. Evidence for modal and cryptic metasomatism is given by addition of clinopyroxene ± phlogopite, and by LILE and LREE enrichment in clinopyroxene. Refertilization process appears to have been induced by sub-lithospheric volatile-rich melts at high melt/rock ratio, and were followed by cooling. To account for the geodynamic evolution of SCLM beneath the southern MER, which implies a temperature gradient from 50-60 to ˜ 90 mW/m2, we propose that thinning of the base of fertile SCLM from 90-95 to ˜45km depth and associated magmatism occurred along a normal-mantle adiabat above an upwelling asthenosphere (i.e., decompression melting) without the need for significant heat sources.

  15. Equatorial atmospheric weather regimes: Their structure and role

    SciTech Connect

    Connors, V.S.

    1991-01-01

    Infrared radiance measurements by the Geostationary Operational Environmental Satellite (GOES-6) from April 1986 through April 1987 are used to characterize and identify distinct regimes of persistent, large-scale cloudiness patterns over the Amazon Basin. These tropical weather regimes are responsible for the continental-scale atmospheric processes that transport air, trace gases, and heat from the Amazon Basin. The cloud patterns are represented by both scene-scale parameters, such as the cloud-free area and the value of the 'clear sky peak' in a histogram, and textural measures, such as contrast of cloudy area and homogeneity or cloudy area. Correlation analyses of the attribute arrays determined that only 9 of the original 15 cloud pattern descriptors are required for the cluster analyses. Seventy-six percent of the satellite images are classified into 1 of 14 weather regimes which persist for periods that range from 3 to 15 days each. The dominant weather regimes are described by the recurrence and duration of the events, by the rainfall produced and energy released to the tropical atmosphere, and by the composite kinematic and thermodynamic analyses. While the classification analyses identified a range of organized weather conditions in the Amazon Basin, two weather regimes, each occurring in separate seasons, dominate the year. The prominent dry season regime (A) occurs 11 times, persists for 25 percent of the year, produces 81 percent of the dry season rainfall, and 7 percent of the energy export necessary to balance the global heat budget. The prominent wet season regime (B) occurs 8 times, persists for 18 percent of the year, delivers about 30 percent of the wet season rainfall, and 16 percent of the energy export requirement. Because the dry season regime (A) draws nearly half of its water vapor supply from local sources, a vital link may exist between the rainforest ecosystem and the dry season rainfall.

  16. Factors controlling depth of continental rifts

    NASA Astrophysics Data System (ADS)

    Elesin, Y.; Artemieva, I. M.; Thybo, H.

    2011-12-01

    Rifting is a fundamental plate tectonic process, which forms elongated, narrow tectonic depressions in the Earth's surface and, eventually, may break continental plates to form new oceanic lithosphere. Subsidence of rift basins is caused by thinning of the crust and lithospheric mantle together with isostatic compensation for the extra load of sediments and thermal relaxation. It is generally believed that the final depth of rift basins is primarily controlled by the amount of stretching and that other processes only have secondary influence. However, we show that the relative rheological strength of faults inside and outside rift zones exerts substantial control on the volume of the final rift basin (by more than a factor of 3) even for the same amount of extension (total or inside the rift zone). This surprising result is mainly caused by irreversible deepening of the rift graben during stretching due to lower crustal flow when the faults in the rift zone are weak, whereas the effect is negligible for strong faults. Relatively strong faults inside the rift zone lead to substantial stretching of adjacent crust, and we find that long term stretching outside the main rift zone may explain the formation of wide continental margins, which are now below sea level. We also demonstrate that fast syn-rift erosion/sedimentation rates can increase the final volume of rift basins by up to a factor of 1.7 for weak crustal faults, whereas this effect is insignificant for strong faults inside the rift zone. These findings have significant implications for estimation of stretching factors, tectonic forces, and geodynamic evolution of sedimentary basins around failed rift zones.

  17. Continental collisions and seismic signature

    NASA Astrophysics Data System (ADS)

    Meissner, R.; Wever, Th.; Sadowiak, P.

    1991-04-01

    Reflection seismics in compressional belts has revealed the structure of crustal shortening and thickening processes, showing complex patterns of indentation and interfingering of colliding crusts and subcrustal lithospheres. Generally, in the upper crust large zones of detachments develop, often showing duplexes and 'crocodile' structures. The lower crust from zones of active collision (e.g. Alps, Pyrenees) is characterized by strongly dipping reflections. The base of the crust with the Moho must be continuously equilibrating after orogenic collapse as areas of former continental collision exhibit flat Mohos and subhorizontal reflections. The depth to the Moho increases during collision and decreases after the onset of post-orogenic extension, until finally the crustal root disappears completely together with the erosion of the mountains. Processes, active during continental collisions and orogenic collapse, create distinct structures which are imaged by reflection seismic profiling. Examples are shown and discussed.

  18. Continental crust beneath southeast Iceland.

    PubMed

    Torsvik, Trond H; Amundsen, Hans E F; Trønnes, Reidar G; Doubrovine, Pavel V; Gaina, Carmen; Kusznir, Nick J; Steinberger, Bernhard; Corfu, Fernando; Ashwal, Lewis D; Griffin, William L; Werner, Stephanie C; Jamtveit, Bjørn

    2015-04-14

    The magmatic activity (0-16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland--and especially the Öræfajökull volcano--is characterized by a unique enriched-mantle component (EM2-like) with elevated (87)Sr/(86)Sr and (207)Pb/(204)Pb. Here, we demonstrate through modeling of Sr-Nd-Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2-6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume. PMID:25825769

  19. Continental crust beneath southeast Iceland.

    PubMed

    Torsvik, Trond H; Amundsen, Hans E F; Trønnes, Reidar G; Doubrovine, Pavel V; Gaina, Carmen; Kusznir, Nick J; Steinberger, Bernhard; Corfu, Fernando; Ashwal, Lewis D; Griffin, William L; Werner, Stephanie C; Jamtveit, Bjørn

    2015-04-14

    The magmatic activity (0-16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland--and especially the Öræfajökull volcano--is characterized by a unique enriched-mantle component (EM2-like) with elevated (87)Sr/(86)Sr and (207)Pb/(204)Pb. Here, we demonstrate through modeling of Sr-Nd-Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2-6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume.

  20. Why does continental convergence stop

    SciTech Connect

    Hynes, A.

    1985-01-01

    Convergence between India and Asia slowed at 45 Ma when they collided, but continues today. This requires that substantial proportions of the Indian and/or Asian lithospheric mantle are still being subducted. The resulting slab-pull is probably comparable with that from complete lithospheric slabs and may promote continued continental convergence even after collision. Since descending lithospheric slabs are present at all collision zones at the time of collision such continued convergence may be general after continental collisions. It may cease only when there is a major (global) plate reorganization which results in new forces on the convergent continents that may counteract the slab-pull. These inferences may be tested on the late Paleozoic collision between Gondwanaland and Laurasia. This is generally considered to have been complete by mid-Permian time (250 Ma). However, this may be only the time of docking of Gondwanaland with North America, not that of the cessation of convergence. Paleomagnetic polar-wander paths for the Gondwanide continents exhibit consistently greater latitudinal shifts from 250 Ma to 200 Ma than those of Laurasia when corrected for post-Triassic drift, suggesting that convergence continued through late Permian well into the Triassic. It may have been accommodated by crustal thickening under what is now the US Coastal Plain, or by strike-slip faulting. Convergence may have ceased only when Pangea began to fragment again, in which case the cause for its cessation may be related to the cause of continental fragmentation.

  1. Continental crust beneath southeast Iceland

    PubMed Central

    Torsvik, Trond H.; Amundsen, Hans E. F.; Trønnes, Reidar G.; Doubrovine, Pavel V.; Gaina, Carmen; Kusznir, Nick J.; Steinberger, Bernhard; Corfu, Fernando; Ashwal, Lewis D.; Griffin, William L.; Werner, Stephanie C.; Jamtveit, Bjørn

    2015-01-01

    The magmatic activity (0–16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland—and especially the Öræfajökull volcano—is characterized by a unique enriched-mantle component (EM2-like) with elevated 87Sr/86Sr and 207Pb/204Pb. Here, we demonstrate through modeling of Sr–Nd–Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2–6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume. PMID:25825769

  2. The Magnetic Signature of Zones of Continental Collision

    NASA Astrophysics Data System (ADS)

    Purucker, M. E.; Whaler, K. A.

    2007-12-01

    Near-surface and satellite maps of the crustal component of the magnetic field can be interpreted in terms of thermal conditions at depth because the magnetic properties of rocks depend on their temperature. Observations related to continental deformation at diffuse plate boundaries are often considered in relation to three length scales: the thickness of the seismogenic upper crust, the entire continental crust, and the mechanical lithosphere. The lower boundary of the magnetic crust coincides with the Moho, or in the presence of an elevated geotherm, with the Curie isotherm. New global perspectives on the magnetic signature of zones of continental collision are afforded by the recently published Magnetic Anomaly Map of the World (Purucker, 2007, EOS, 88, 263), the MF-5 satellite magnetic field (Maus et al., 2007, Gcubed), and NASA's ST-5 constellation mission in 2006. The thickness of the magnetic crust can be estimated by integrating the MF-5 satellite magnetic field into the 3SMAC compositional and thermal model of the lithosphere, and a minimum estimate of the magnetization can be estimated using a Greens function approach. We compare our magnetic maps with the diffuse plate boundary maps of Gordon (1998) and Dumoulin et al. (1998). The diffuse plate boundary zones exhibit intermediate (22-31 km) magnetic thicknessses, significantly less than those of the adjacent stable plate. The diffuse NE Asia plate boundary zone, from the Lena River delta to the Sea of Okhotsk, is especially well- expressed in both satellite and near-surface magnetic maps.

  3. Mantle discontinuities and temperature under the North American continental keel

    NASA Astrophysics Data System (ADS)

    Li, Aibing; Fischer, Karen M.; Wysession, Michael E.; Clarke, Timothy J.

    1998-09-01

    A ubiquitous feature of upper-mantle seismic velocity models has been the presence of high-velocity `keels' beneath stable continental interiors. Uncertainty remains, however, regarding the maximum depth to which continental keels extend, the degree to which they have cooled the mantle that surrounds them and their role in mantle flow. Here we investigate thermal anomalies across the eastern margin of the North American continental keel by imaging the seismic discontinuities at depths of 410 and 660km with compressional-to-shear converted waves recorded by a 1,500-km-long seismometer deployment in the eastern United States. The thickness of the transition zone (the region nominally between depths of 410 and 660km) and the depth to the `410-km' discontinuity indicate that cold keel material and sub-keel downwellings must be largely confined to the upper mantle and may impinge on the transition zone only in localized regions and with thermal anomalies of less than ~150K. A 20-km depression of the `660-km' discontinuity to the south of the westernmost stations coincides with a region of fast velocity in the deep transition zone and may be associated with the remnants of the subducted Farallon plate,,.

  4. The Davie Ridge: a Marginal Transform Ridge not Formed During Continental Breakup

    NASA Astrophysics Data System (ADS)

    Phethean, J. J. J.; Van Hunen, J.; McCaffrey, K. J. W.; Davies, R. J.

    2014-12-01

    The breakup of Gondwana translated Madagascar southwards relative to Africa along the Davie Fracture Zone (DFZ). This fracture zone now forms the Transform Passive Continental Margin (TPCM) from Kenya to Mozambique. The Davie Ridge (DR), a transform marginal ridge, has formed along the DFZ between 5 and 2°S and 22 and 11°S, but with little expression in-between. It has been proposed that this marginal ridge was formed by the thermal effects of a passing Mid Ocean Ridge (MOR) during the separation of Gondwana. Plate kinematic reconstructions, however, constrained by ocean magnetic anomalies, show that the MOR only passed between the north and south expressions of the DR. Therefore the positive linear gravity anomalies of the DR cannot be attributed to the effects of a passing MOR, and some other mechanism must be found to explain their formation. Interpretation of seismic reflection profiles along the DR shows that the gravity highs occur adjacent to large basin structures. In the north this correlates with a basin-bounding basement high of ~Albian age, and in the south with the rift flank uplifts of the currently active Quirimbas graben. This suggests that the northern and southern DR segments are instead shoulder uplifts resulting from two separate extensional episodes during different stress regimes. These are the Cretaceous NE-SW extension during the breakup of the south Atlantic, and the E-W extension of the Neogene-recent Afar-East Africa rift system, respectfully. The lack of deformation and DR formation along the region of the TPCM passed by the MOR suggests it has been coupled by thermal effects and/or the injection of magma.

  5. Lithospheric records of orogeny within the continental U.S.

    NASA Astrophysics Data System (ADS)

    Porter, Ryan; Liu, Yuanyuan; Holt, William E.

    2016-01-01

    In order to better understand the tectonic evolution of the North American continent, we utilize data from the EarthScope Transportable Array network to calculate a three-dimensional shear velocity model for the continental United States. This model was produced through the inversion of Rayleigh wave phase velocities calculated using ambient noise tomography and wave gradiometry, which allows for sensitivity to a broad depth range. Shear velocities within this model highlight the influence of orogenic and postorogenic events on the evolution of the lithosphere. Most notable is the contrast in crustal and upper mantle structure between the relatively slow western and relatively fast eastern North America. These differences are unlikely to stem solely from thermal variations within the lithosphere and highlight both the complexities in lithospheric structure across the continental U.S. and the varying impacts that orogeny can have on the crust and upper mantle.

  6. Development of topography in 3-D continental-collision models

    NASA Astrophysics Data System (ADS)

    Pusok, A. E.; Kaus, Boris J. P.

    2015-05-01

    Understanding the formation and evolution of high mountain belts, such as the Himalayas and the adjacent Tibetan Plateau, has been the focus of many tectonic and numerical models. Here we employ 3-D numerical simulations to investigate the role that subduction, collision, and indentation play on lithosphere dynamics at convergent margins, and to analyze the conditions under which large topographic plateaus can form in an integrated lithospheric and upper mantle-scale model. Distinct dynamics are obtained for the oceanic subduction side (trench retreat, slab rollback) and the continental-collision side (trench advance, slab detachment, topographic uplift, lateral extrusion). We show that slab pull alone is insufficient to generate high topography in the upper plate, and that external forcing and the presence of strong blocks such as the Tarim Basin are necessary to create and shape anomalously high topographic fronts and plateaus. Moreover, scaling is used to predict four different modes of surface expression in continental-collision models: (I) low-amplitude homogeneous shortening, (II) high-amplitude homogeneous shortening, (III) Alpine-type topography with topographic front and low plateau, and (IV) Tibet-Himalaya-type topography with topographic front and high plateau. Results of semianalytical models suggest that the Argand number governs the formation of high topographic fronts, while the amplitude of plateaus is controlled by the initial buoyancy ratio of the upper plate. Applying these results to natural examples, we show that the Alps belong to regime (III), the Himalaya-Tibet to regime (IV), whereas the Andes-Altiplano fall at the boundary between regimes (III) and (IV).

  7. Modes of continental extension in a lithospheric wedge

    NASA Astrophysics Data System (ADS)

    Wu, G.; Lavier, L. L.; Choi, E.

    2014-12-01

    We studied extension of a lithospheric wedge as an approximation to an orogenic belt or a continental margin. We ran a series of numerical models to quantify the effects of the strength of the lower crust and a mid-crustal shear zone (MCSZ) on the extension processes. When the MCSZ is present, we found that the regional lower crustal flow plays a critical role in controlling the modes of extension. The compensation is long-wavelength when the lower crust flows from the highest to the lowest elevation in order to compensate upper crustal thinning. In response to this motion, the mantle flows towards the highest elevation in order to balance for the lower crust leaving the area under the highest topography. For weak (wet quartz regime with partial melting) or intermediate (wet quartz regime), or strong (dry quartz regime) lower crust, we recognized three predominantly decoupled modes of extension characterized by 1) significant lower crustal exhumation exemplified as a large massif, 2) formation of core complexes and detachment faults, and 3) distributive domino faulting, respectively. Without the MCSZ, however, the lower crustal flow is essentially subdued with predominantly coupled extension. For weak or intermediate, or strong lower crust, we recognized three coupled modes characterized by 1) localized generally symmetric crustal exhumation, 2) distributed grabens and narrow rifts, and 3) wide continental margins, respectively. The MCSZ controls the degree of decoupling of the lower crustal flow such that a frictionally stronger MCSZ does not change the behaviors of the models but results in a more distributed extension. Due to the long-wavelength compensation, subhorizontal Moho is achieved where intensive extension occurred for all the decoupled models with a MCSZ. Natural counterparts for each mode may be easily identified, for instance, in the Basin and Range or the Aegean.

  8. Examination Regimes and Student Achievement

    ERIC Educational Resources Information Center

    Cosentino de Cohen, Clemencia

    2010-01-01

    Examination regimes at the end of secondary school vary greatly intra- and cross-nationally, and in recent years have undergone important reforms often geared towards increasing student achievement. This research presents a comparative analysis of the relationship between examination regimes and student achievement in the OECD. Using a micro…

  9. The geodynamic province of transitional crust adjacent to magma-poor continental margins

    NASA Astrophysics Data System (ADS)

    Sibuet, J.; Tucholke, B. E.

    2011-12-01

    Two types of 'transitional crust' have been documented along magma-poor rifted margins. One consists of apparently sub-continental mantle that has been exhumed and serpentinized in a regime of brittle deformation during late stages of rifting. A second is highly thinned continental crust, which in some cases is known to have been supported near sea level until very late in the rift history and thus is interpreted to reflect depth-dependent extension. In both cases it is typically assumed that formation of oceanic crust occurs shortly after the breakup of brittle continental crust and thus that the transitional crust has relatively limited width. We here examine two representative cases of transitional crust, one in the Newfoundland-Iberia rift (exhumed mantle) and one off the Angola-Gabon margin (highly thinned continental crust). Considering the geological and geophysical evidence, we propose that depth-dependent extension (riftward flow of weak lower/middle continental crust and/or upper mantle) may be a common phenomenon on magma-poor margins and that this can result in a much broader zone of transitional crust than has hitherto been assumed. Transitional crust in this extended zone may consist of sub-continental mantle, lower to middle continental crust, or some combination thereof, depending on the strength profile of the pre-rift continental lithosphere. Transitional crust ceases to be emplaced (i.e., final 'breakup' occurs) only when emplacement of heat and melt from the rising asthenosphere becomes dominant over lateral flow of the weak lower lithosphere. This model implies a two-stage breakup: first the rupture of the brittle upper crust and second, the eventual emplacement of oceanic crust. Well-defined magnetic anomalies can form in transitional crust consisting of highly serpentinized, exhumed mantle, and they therefore are not diagnostic of oceanic crust. Where present in transitional crust, these anomalies can be helpful in interpreting the rifting

  10. Craton stability and continental lithosphere dynamics during plume-plate interaction

    NASA Astrophysics Data System (ADS)

    Wang, H.; Van Hunen, J.; Pearson, D.

    2013-12-01

    Survival of thick cratonic roots in a vigorously convecting mantle system for billions of years has long been studied by the geodynamical community. A high cratonic root strength is generally considered to be the most important factor. We first perform and discuss new numerical models to investigate craton stability in both Newtonian and non-Newtonian rheology in the stagnant lid regime. The results show that only a modest compositional rheological factor of Δη=10 with non-Newtonian rheology is required for the survival of cratonic roots in a stagnant lid regime. A larger rheological factor (100 or more) is needed to maintain similar craton longevity in a Newtonian rheology environment. Furthermore, chemical buoyancy plays an important role on craton stability and its evolution, but could only work with suitable compositional rheology. During their long lifespan, cratons experienced a suite of dynamic, tectonothermal events, such as nearby subduction and mantle plume activity. Cratonic nuclei are embedded in shorter-lived, more vulnerable continental areas of different thickness, composition and rheology, which would influence the lithosphere dynamic when tectonothermal events happen nearby. South Africa provides a very good example to investigate such dynamic processes as it hosts several cratons and there are many episodic thermal events since the Mesozoic as indicated by a spectrum of magmatic activity. We numerically investigate such an integrated system using the topographic evolution of cratons and surrounding lithosphere as a diagnostic observable. The post-70Ma thinning of pericratonic lithosphere by ~50km around Kaapvaal craton (Mather et al., 2011) is also investigated through our numerical models. The results show that the pericratonic lithosphere cools and grows faster than cratons do, but is also more likely to be effected by episodic thermal events. This leads to surface topography change that is significantly larger around the craton than within

  11. Hydrological Modeling of Continental-Scale Basins

    NASA Astrophysics Data System (ADS)

    Wood, Eric F.; Lettenmaier, Dennis; Liang, Xu; Nijssen, Bart; Wetzel, Suzanne W.

    Hydrological models at continental scales are traditionally used for water resources planning. However, continental-scale hydrological models may be useful in assessing the impacts from future climate change on catchment hydrology and water resources or from human activity on hydrology and biogeochemical cycles at large scales. Development of regional-scale terrestrial hydrological models will further our understanding of the Earth's water cycle. Continental scales allow for better understanding of the geographic distribution of land-atmospheric moisture fluxes, improved water management at continental scales, better quantification of the impact of human activity and climate change on the water cycle, and improved simulation of weather and climate.

  12. Continental rifting: a planetary perspective

    SciTech Connect

    Muehlberger, W.R.

    1985-01-01

    The only inner planet that has abundant evidence of regional extension, and the consequent generation of rifts in the earth. The absence of plate motion on the other inner planets limits their rifts to localized bulges or subsidence areas. The rifting of oceanic lithosphere is seldom preserved in the geological record. Thus, such rifting must be inferred via plate tectonic interpretation: if there is rifting, then there must be subduction whose results are commonly well preserved. Modern continental rifts are found in many tectonic settings: continental breakup, extension transverse to collisional stresses, or wide regions of nearly uniform extension. Recognition of these settings in older rocks becomes more difficult the farther back in geologic time you travel. Rift basin fillings typically show rapid lateral and vertical facies and thickness changes, bimodal volcanism, and distinctive rift-drift sequences. Proterozoic rifts and aulacogens are well-documented in North America; ex. Keweenawan, western margin of Labrador fold belt, Belt-Uinta and the Wopmay-Athapuscow regions. Documented Archean rifts are rare. In Quebec, the truncated margin of the Minto craton bounded on the south by a 2.8 Ga greenstone belt implies an earlier rift event. The oldest proposed rift dated at 3.0 Ga contains the Pongola Supergroup in southeastern Africa. The presence of Archean dikes demonstrates a rigid crust and andesites as old as 3.5 Ga imply plate tectonics and thus, at least, oceanic rifting.

  13. Palaeoclimate, Sedimentation and Continental Accretion

    NASA Astrophysics Data System (ADS)

    Ziegler, A. M.; Barrett, S. F.; Scotese, C. R.

    1981-05-01

    Climate has a pervasive effect on sedimentation today, and the same climatic patterns are reflected in the distribution of lithofacies through the Palaeozoic, as the continents migrate beneath the climatic zones. The low-latitude hot wet zone is represented by thick clastics, coals and carbonates and is best developed along east coasts where prevailing winds bring moisture and heated surface waters toward the continent. The desert zones occur on the west sides of continents centred at 20 degrees north and south, and these dry belts are represented in the geological record by evaporites. Tillites, thick clastics and coals occur in the temperate rainy belts, especially on the windward, west sides of continents above 40 degrees latitude. Continental accretion occurs where subduction zones coincide with rainy zones, such that the products of erosion are transported to the trench, and thus thrust back, extending the margin of the continent. The opposite process of `tectonic erosion', wherein the descending oceanic slab continually `rasps' away the margin of the continental crust, may occur in areas where rainfall and surface run-off is insufficient to provide trench sediments. This process has been operating adjacent to the Atacama Desert in South America during the past 200 Ma. To judge by the eastward migration of the calc-alkaline intrusive foci, about 250 km of the margin of South America have been transported down the subduction zone during this period.

  14. Cratons Formation and the Earth Episodic Thermal History

    NASA Astrophysics Data System (ADS)

    Davaille, A.; Arndt, N.

    2007-12-01

    U-Pb ages of zircons in granites and large rivers record a three-stage evolution of the continental crust. Plate tectonics operated in the first stage, from ~4.4 to 2.7 Ga. Huge peaks of crustal growth separated by long troughs dominated the second stage, from 2.7 to 1.8 Ga. Semi-continuous growth punctuated by large peaks characterized the last stage, from 1.8 to 0 Ga. Individual peaks in the second stage open with massive mafic- ultramafic volcanism and climax 30 Ma later with intrusion of voluminous granitoids: each peak opened with enhanced mantle plume activity, climaxed with accelerated plate tectonic activity, and was followed by a long quiet period when little crust formed. We develop a fluid-mechanics model to explain the three-stage evolution and the pronounced peak-and-trough pattern of the second stage. Low temperatures in the upper mantle during the first and last stages allow the formation of thin, subductable oceanic crust, and lead to a plate-tectonic regime. The crustal-growth peaks of the second regime results from destabilization of a hot denser layer at the bottom of the lower mantle. Domes rising from this layer partially melt to form voluminous mafic magmas. Moreover, when the domes hit and spread under the top surface, they peel off the cold thermal boundary layer there, which triggers a ring of enhanced cold instabilities around each thermochemical dome. This period of enhanced downwellings (i.e. subduction) is however followed by a lull, during which the cold thermal boundary layer is growing again. The onset of the first thermochemical instabilities is predicted to be synchroneous on the whole mantle , and followed by several more disorganized events, in agreement with observations. These experiments closely link continental growth and the thermal history of our planet, which appear strongly episodic. The importance of the 2.7 Ga peak, related to the sudden destabilization of a lower denser layer, suggests that extraction of heat from the

  15. Earth's continental crustal gold endowment

    NASA Astrophysics Data System (ADS)

    Frimmel, H. E.

    2008-03-01

    The analysis of the temporal distribution of gold deposits, combined with gold production data as well as reserve and resource estimates for different genetic types of gold deposit, revealed that the bulk of the gold known to be concentrated in ore bodies was added to the continental crust during a giant Mesoarchaean gold event at a time (3 Ga) when the mantle temperature reached a maximum and the dominant style of tectonic movement changed from vertical, plume-related to subhorizontal plate tectonic. A magmatic derivation of the first generation of crustal gold from a relatively hot mantle that was characterized by a high degree of partial melting is inferred from the gold chemistry, specifically high Os contents. While a large proportion of that gold is still present in only marginally modified palaeoplacer deposits of the Mesoarchaean Witwatersrand Basin in South Africa, accounting for about 40% of all known gold, the remainder has been recycled repeatedly on a lithospheric scale, predominantly by plate-tectonically induced magmatic and hydrothermal fluid circulation, to produce the current variety of gold deposit types. Post-Archaean juvenile gold addition to the continental crust has been limited, but a mantle contribution to some of the largest orogenic or intrusion-related gold deposits is indicated, notably for the Late Palaeozoic Tien Shan gold province. Magmatic fluids in active plate margins seem to be the most effective transport medium for gold mobilization, giving rise to a large proportion of volcanic-arc related gold deposits. Due to their generally shallow crustal level of formation, they have a low preservation potential. In contrast, those gold deposits that form at greater depth are more widespread also in older rocks. This explains the high proportion of orogenic (including intrusion-related) gold (32%) amongst all known gold deposits. The overall proportion of gold concentrated in known ore bodies is only 7 × 10- 7 of the estimated total

  16. Optical and Hall conductivities of a thermally disordered two-dimensional spin-density wave : two-particle response in the pseudogap regime of electron-doped high-T{sub c} superconductors.

    SciTech Connect

    Lin, J.; Millis, A. J.

    2011-03-18

    We calculate the frequency-dependent longitudinal ({sigma}{sub xx}) and Hall ({sigma}{sub xy}) conductivities for two-dimensional metals with thermally disordered antiferromagnetism using a generalization of a theoretical model, involving a one-loop quasistatic fluctuation approximation, which was previously used to calculate the electron self-energy. The conductivities are calculated from the Kubo formula, with current vertex function treated in a conserving approximation satisfying the Ward identity. In order to obtain a finite dc limit, we introduce phenomenologically impurity scattering, characterized by a relaxation time {tau}. {sigma}{sub xx}({Omega}) satisfies the f-sum rule. For the infinitely peaked spin-correlation function, {chi}(q){proportional_to}{delta}(q-Q), we recover the expressions for the conductivities in the mean-field theory of the ordered state. When the spin-correlation length {zeta} is large but finite, both {sigma}{sub xx} and {sigma}{sub xy} show behaviors characteristic of the state with long-range order. The calculation runs into difficulty for {Omega} {approx}< 1/{tau}. The difficulties are traced to an inaccurate treatment of the very-low-energy density of states within the one-loop quasistatic approximation for the self-energy. The results for {sigma}{sub xx}({Omega}) and {sigma}{sub xy}({Omega}) are qualitatively consistent with data on electron-doped cuprates when {Omega} > 1/{tau}.

  17. Density Sorting During the Evolution of Continental Crust

    NASA Astrophysics Data System (ADS)

    Kelemen, P. B.; Behn, M. D.; Hacker, B. R.

    2015-12-01

    We consider two settings - in addition to "delamination" of arc lower crust - in which dense, mafic eclogites founder into the convecting mantle while buoyant, felsic lithologies accumulate at the base of evolving continental crust. Arc processes play a central role in generating continental crust, but it remains uncertain how basaltic arc crust is transformed to andesitic continental crust. Dense, SiO2-poor products of fractionation may founder from the base of arc crust by "delamination", but lower arc crust after delamination has significantly different trace elements compared to lower continental crust (LCC). In an alternative model, buoyant magmatic rocks generated at arcs are first subducted, mainly via subduction erosion. Upon heating, these buoyant lithologies ascend through the mantle wedge or along a subduction channel, and are "relaminated" at
the base of overlying crust (e.g., Hacker et al EPSL 11, AREPS 15). Average buoyant lavas and plutons
for the Aleutians, Izu-Bonin-Marianas, Kohistan and Talkeetna arcs fall within the range of estimated LCC major and trace elements. Relamination is more efficient in generating continental crust than delamination. Himalayan cross-sections show Indian crust thrust beneath Tibetan crust, with no intervening mantle. There is a horizontal Moho at ca 80 km depth, extending from thickened Indian crust, across the region where Tibetan crust overlies Indian crust, into thickened Tibetan crust. About half the subducted Indian crust is present, whereas the other half is missing. Data (Vp/Vs; Miocene lavas formed by interaction of continental crust with mantle; xenolith thermometry) indicate 1000°C or more from ca 50 km depth to the Moho since the Miocene. We build on earlier studies (LePichon et al Tectonics 92, T'phys 97; Schulte-Pelkum et al Nature 05; Monsalve et al JGR 08) to advance the hypothesis that rapid growth of garnet occurs at 70-80 km and 1000°C within subducting Indian crust. Dense eclogites founder

  18. Sulfur and metal fertilization of the lower continental crust

    NASA Astrophysics Data System (ADS)

    Locmelis, Marek; Fiorentini, Marco L.; Rushmer, Tracy; Arevalo, Ricardo; Adam, John; Denyszyn, Steven W.

    2016-02-01

    Mantle-derived melts and metasomatic fluids are considered to be important in the transport and distribution of trace elements in the subcontinental lithospheric mantle. However, the mechanisms that facilitate sulfur and metal transfer from the upper mantle into the lower continental crust are poorly constrained. This study addresses this knowledge gap by examining a series of sulfide- and hydrous mineral-rich alkaline mafic-ultramafic pipes that intruded the lower continental crust of the Ivrea-Verbano Zone in the Italian Western Alps. The pipes are relatively small (< 300 m diameter) and primarily composed of a matrix of subhedral to anhedral amphibole (pargasite), phlogopite and orthopyroxene that enclose sub-centimeter-sized grains of olivine. The 1 to 5 m wide rim portions of the pipes locally contain significant blebby and disseminated Fe-Ni-Cu-PGE sulfide mineralization. Stratigraphic relationships, mineral chemistry, geochemical modeling and phase equilibria suggest that the pipes represent open-ended conduits within a large magmatic plumbing system. The earliest formed pipe rocks were olivine-rich cumulates that reacted with hydrous melts to produce orthopyroxene, amphibole and phlogopite. Sulfides precipitated as immiscible liquid droplets that were retained within a matrix of silicate crystals and scavenged metals from the percolating hydrous melt. New high-precision chemical abrasion TIMS U-Pb dating of zircons from one of the pipes indicates that these pipes were emplaced at 249.1 ± 0.2 Ma, following partial melting of lithospheric mantle pods that were metasomatized during the Eo-Variscan oceanic to continental subduction (~ 420-310 Ma). The thermal energy required to generate partial melting of the metasomatized mantle was most likely derived from crustal extension, lithospheric decompression and subsequent asthenospheric rise during the orogenic collapse of the Variscan belt (< 300 Ma). Unlike previous models, outcomes from this study suggest a

  19. Deformation in the continental lithosphere

    NASA Astrophysics Data System (ADS)

    The Physical Properties of Earth Materials Committee, a technical committee of AGU's Tectonophysics Section, is organizing a dinner/colloquium as part of the Fall Meeting in San Francisco, Calif. This event will be held Monday, December 3rd, in the Gold Rush Room of the Holiday Inn Golden Gateway Hotel at 1500 Van Ness St. There will be a no-host bar from 6:30 to 7:30 P.M., followed by dinner from 7:30 to 8:30 P.M. Paul Tapponnier will deliver the after-dinner talk, “Large-Scale Deformation Mechanisms in the Continental Lithosphere: Where Do We Stand?” It will start at 8:30 P.M. and a business meeting will follow at 9:30 P.M.

  20. Composition of the continental plates

    USGS Publications Warehouse

    Gilluly, J.

    1954-01-01

    The structures of continental plates and of oceanic basins suggested by several seismologists are utilized to estimate the relative volumes of sial and sima in the earth's crust. It seems that sial of the composition of the average igneous rock constitutes fully 26% and perhaps as much as 43% of the total crust. This ratio is far higher than seems likely if the sial had been entirely derived through fractional crystallization of a basaltic magma. The relative paucity of intermediate rocks as compared with granite and gabbro in the crust points in the same direction. The tentative conclusion is reached that the sial owes a large part of its volume to some process other than fractional crystallization of basalt-possibly to the emanation of low-melting constituents such as water, silica, potassa, soda, and alumina directly from the mantle to the crust. ?? 1954 Springer-Verlag.

  1. Inventory and burial fluxes of Black Carbon in the Swedish continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Sánchez-García, L.; Cato, I.; Gustafsson, Ö.

    2009-04-01

    Highly condensed black carbon (BC) particles, mainly derived from incomplete combustion of biomass and fossil fuel, are involved in several important processes in the biogeosphere [1], including sedimentary carbon burial, sequestration of organic pollutants in soils and sediments, affecting Earth's radiative heat balance and even human respiratory health. BC is commonly found to constitute several to 20% of total sedimentary carbon, and thus plays an important but poorly constrained role in the global biogeospheric carbon cycle. Sequestration of biogenic carbon as BC is a direct sink of the element from the rapidly cycling atmosphere-biosphere reservoirs, whereas burial of petrogenic/fossil BC is simply a conversion of one form of geological carbon to another [2]. Considerable emphasis has been made on the relevant role this recalcitrant form of organic matter (OM) may play on the global C cycle and yet large uncertainty exists around BC detection and quantification. This work seeks to provide a large-scale estimate of the reservoir and burial sink flux of BC in sediments from the extensive Swedish continental shelf (SCS), as a first approach to global inventories. To this end, a total of 120 sediment samples were collected from the Exclusive Economic Zone (EEZ) along the ?2000 km SCS stretch. The most recalcitrant fraction of the sedimentary OM was isolated and determined by means of a commonly applied method in biogeochemical studies of soils and sediments: chemo-thermal oxidation at 375˚ C in air (CTO-375). The obtained BC concentration was used to estimate the inventory and burial flux of BC in the SCS surface sediments, following [3], which takes into account key geophysical and geochemical properties of the nine distinct sedimentary regimes of the SCS that was separately assessed. Globally representative values of the sediment properties (e.g. density of dried sediments, bioturbated mixing depth, sedimentation rate or porosity over the mixed depth) were

  2. How Continental Bank outsourced its "crown jewels.".

    PubMed

    Huber, R L

    1993-01-01

    No industry relies more on information than banking does, yet Continental, one of America's largest banks, outsources its information technology. Why? Because that's the best way to service the customers that form the core of the bank's business, says vice chairman Dick Huber. In the late 1970s and early 1980s, Continental participated heavily with Penn Square Bank in energy investments. When falling energy prices burst Penn Square's bubble in 1982, Continental was stuck with more than $1 billion in bad loans. Eight years later when Dick Huber came on board, Continental was working hard to restore its once solid reputation. Executives had made many tough decisions already, altering the bank's focus from retail to business banking and laying off thousands of employees. Yet management still needed to cut costs and improve services to stay afloat. Regulators, investors, and analysts were watching every step. Continental executives, eager to focus on the bank's core mission of serving business customers, decided to outsource one after another in-house service--from cafeteria services to information technology. While conventional wisdom holds that banks must retain complete internal control of IT, Continental bucked this argument when it entered into a ten-year, multimillion-dollar contract with Integrated Systems Solutions Corporation. Continental is already reaping benefits from outsourcing IT. Most important, Continental staffers today focus on their true core competencies: intimate knowledge of customers' needs and relationships with customers.

  3. How Continental Bank outsourced its "crown jewels.".

    PubMed

    Huber, R L

    1993-01-01

    No industry relies more on information than banking does, yet Continental, one of America's largest banks, outsources its information technology. Why? Because that's the best way to service the customers that form the core of the bank's business, says vice chairman Dick Huber. In the late 1970s and early 1980s, Continental participated heavily with Penn Square Bank in energy investments. When falling energy prices burst Penn Square's bubble in 1982, Continental was stuck with more than $1 billion in bad loans. Eight years later when Dick Huber came on board, Continental was working hard to restore its once solid reputation. Executives had made many tough decisions already, altering the bank's focus from retail to business banking and laying off thousands of employees. Yet management still needed to cut costs and improve services to stay afloat. Regulators, investors, and analysts were watching every step. Continental executives, eager to focus on the bank's core mission of serving business customers, decided to outsource one after another in-house service--from cafeteria services to information technology. While conventional wisdom holds that banks must retain complete internal control of IT, Continental bucked this argument when it entered into a ten-year, multimillion-dollar contract with Integrated Systems Solutions Corporation. Continental is already reaping benefits from outsourcing IT. Most important, Continental staffers today focus on their true core competencies: intimate knowledge of customers' needs and relationships with customers. PMID:10124146

  4. A Facies Model for Temperate Continental Glaciers.

    ERIC Educational Resources Information Center

    Ashley, Gail Mowry

    1987-01-01

    Discusses the presence and dynamics of continental glaciers in the domination of the physical processes of erosion and deposition in the mid-latitudes during the Pleistocene period. Describes the use of a sedimentary facies model as a guide to recognizing ancient temperate continental glacial deposits. (TW)

  5. Evolution of Oxidative Continental Weathering

    NASA Astrophysics Data System (ADS)

    Konhauser, Kurt; Lalonde, Stefan

    2014-05-01

    The Great Oxidation Event (GOE) is currently viewed as a protracted process during which atmospheric oxygen levels increased above 10-5 times the present atmospheric level. This value is based on the loss of sulphur isotope mass independent fractionation (S-MIF) from the rock record, beginning at 2.45 Ga and disappearing by 2.32 Ga. However, a number of recent papers have pushed back the timing for oxidative continental weathering, and by extension, the onset of atmospheric oxygenation several hundreds of million years earlier despite the presence of S-MIF (e.g., Crowe et al., 2013). This apparent discrepancy can, in part, be resolved by the suggestion that recycling of older sedimentary sulphur bearing S-MIF might have led to this signal's persistence in the rock record for some time after atmospheric oxygenation (Reinhard et al., 2013). Here we suggest another possibility, that the earliest oxidative weathering reactions occurred in environments at profound redox disequilibrium with the atmosphere, such as biological soil crusts, riverbed and estuarine sediments, and lacustrine microbial mats. We calculate that the rate of O2 production via oxygenic photosynthesis in these terrestrial microbial ecosystems provides largely sufficient oxidizing potential to mobilise sulphate and a number of redox-sensitive trace metals from land to the oceans while the atmosphere itself remained anoxic with its attendant S-MIF signature. These findings reconcile geochemical signatures in the rock record for the earliest oxidative continental weathering with the history of atmospheric sulphur chemistry, and demonstrate the plausible antiquity of a terrestrial biosphere populated by cyanobacteria. Crowe, S.A., Dossing, L.N., Beukes, N.J., Bau, M., Kruger, S.J., Frei, R. & Canfield, D.E. Atmospheric oxygenation three billion years ago. Nature 501, 535-539 (2013). Reinhard, C.T., Planavsky, N.J. & Lyons, T.W. Long-term sedimentary recycling of rare sulphur isotope anomalies. Nature 497

  6. Two contrasting modes of continental break-up associated with the formation of the Paleo- and Neo-Tethys in Iran: Implications for petrological and geodynamic evolution at a regional scale

    NASA Astrophysics Data System (ADS)

    Saccani, Emilio; Marroni, Michele; Pandolfi, Luca; Allahyari, Khalil; Azimzadeh, Zohreh

    2014-05-01

    contrast with the Ligurian Tethys model, the Neo-Tethys rift stage was also associated with volcanism featuring a marked influence of plume-type components. Nonetheless, no geological evidence (e.g. regional doming, anomalous thermal regime, basaltic plateaux, magmatic evolution from more depleted to more enriched rocks, etc.) supporting the existence of a Triassic mantle plume activity in this area has been documented. Therefore, the plume-type geochemical signature observed in the Kermanshah CMO sequences can likely be explained with the re-activation of portions of enriched mantle (mantle heterogeneities) that were inherited from the Paleozoic mantle plume associated with the opening of Paleo-Tethys.

  7. Some depositional patterns at continental margin of southeastern Mediterranean Sea

    SciTech Connect

    Mart, Y.; Gai, Y.B.

    1982-04-01

    The upper Miocene to Holocene sedimentary strata in the continental margin of the southeastern Mediterranean Sea depict two depositional regimes. The upper Miocene sequence is predominantly evaporitic and forms the southeastern portion of the upper Miocene evaporites present throughout the Mediterranean region. The Pliocene-Quaternary sequence is predominantly detrital and its major source of sediments has been the Nile River. Interpretation of data derived from several multichannel seismic profiles suggested facial variations in the upper Miocene and the Pliocene-Pleistocene formations. Two depositional facies of the upper Miocene evaporites, indicating basinal and shelf depositional environments, were found. Statistical analyses show correlations of the thickness of the evaporites with their interval seismic velocity, their depth, and the present bathymetry, indicating the autochthonous characteristics of the sequence. The basinal and the shelf depositional facies are separated by a transition zone that trends NNE-SSW and is associated with faulting. It is suggested that this zone, commonly known as The Pelusium Line, was the shelf-edge zone during the late Miocene. Facial analysis of the data pertaining to the Pliocene-Pleistocene sequence depicts its allochthonous characteristics. Statistical negative correlation was calculated between the distance from the continental shelf and the thickness of this sequence, indicating its detrital origin. Variations in thicknesses of both formations compared with the bathymetric depths suggest a post-Miocene subsidence of the southeast Mediterranean basin. 6 figures, 4 tables.

  8. Mapping Evaporative Stress at Continental Scales Using GOES Thermal Imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Robust, operational methodologies for mapping daily evapotranspiration (ET), soil moisture, and moisture stress over large areas using satellite remote sensing will have widespread utility in applications such as drought detection, crop yield forecasting, irrigation scheduling, water resource manage...

  9. Great Lakes' regional climate regimes

    NASA Astrophysics Data System (ADS)

    Kravtsov, Sergey; Sugiyama, Noriyuki; Roebber, Paul

    2016-04-01

    We simulate the seasonal cycle of the Great Lakes' water temperature and lake ice using an idealized coupled lake-atmosphere-ice model. Under identical seasonally varying boundary conditions, this model exhibits more than one seasonally varying equilibrium solutions, which we associate with distinct regional climate regimes. Colder/warmer regimes are characterized by abundant/scarce amounts of wintertime ice and cooler/warmer summer temperatures, respectively. These regimes are also evident in the observations of the Great Lakes' climate variability over recent few decades, and are found to be most pronounced for Lake Superior, the deepest of the Great Lakes, consistent with model predictions. Multiple climate regimes of the Great Lakes also play a crucial role in the accelerated warming of the lakes relative to the surrounding land regions in response to larger-scale global warming. We discuss the physical origin and characteristics of multiple climate regimes over the lakes, as well as their implications for a longer-term regional climate variability.

  10. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Technical Reports Server (NTRS)

    Oglesby, Robert; Arnold, James E. (Technical Monitor); Hoffman, Forrest; Hargrove, W. W.; Erickson, D.

    2002-01-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and time

  11. Predictive mapping of the natural flow regimes of France

    NASA Astrophysics Data System (ADS)

    Snelder, Ton H.; Lamouroux, Nicolas; Leathwick, John R.; Pella, Hervé; Sauquet, Eric; Shankar, Ude

    2009-06-01

    SummaryHydrologic variability is important in sustaining a variety of ecological processes in streams and rivers. Natural flow regime classifications group streams and rivers that are relatively homogeneous with respect to flow variability and have been promoted as a method of defining units for management of river flows. Although there has been considerable interest in classifying natural flow regimes, there has been less emphasis given to developing accurate methods of extrapolating these classifications to locations without flow data. We developed a method of mapping flow regime classes using boosted regression trees (BRT) that automatically fits non-linear functions and interactions between explanatory variables of flow regimes, both of which can be expected when comparing responses between complex systems such as watersheds. A natural flow regimes classification of continental France was developed from cluster analysis of 157 hydrological indices derived from 763 gauging stations representing unmodified flows. BRT models were used to predict the likelihood of gauging stations belonging to each class based on the watershed characteristics. These models were used to extrapolate the natural flow regime classification to all segments of a national river network. The performance of the BRT models were compared with other methods of assigning locations to flow regime classes, including the use of geographically contiguous regions, linear discriminant analysis (LDA) and classification and regression trees (CART). The "fitted" misclassification rate (associated with model fits) for assignment based on the BRT models was 13% whereas the fitted misclassification rates for geographically contiguous regions, LDA and CART were 52%, 44% and 39% respectively. A "predictive" misclassification rate (calculated for new cases) was estimated for assignments based on the BRT, LDA and CART models using cross validation analysis. For assignment based on the BRT models, the mean

  12. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Astrophysics Data System (ADS)

    Hoffman, F.; Oglesby, R.; Hargrove, W. W.; Erickson, D.

    2002-12-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan--has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and

  13. A change in stress regime along the Eskisehir Fault, central northwestern Turkey

    NASA Astrophysics Data System (ADS)

    Ozden, S.; Gundogdu, E.

    2009-04-01

    The Eskisehir Fault (EF) which is one of the active main faults in central northwestern Turkey elongated a 150 km long with the WNW-ENE to E-W trending between Bursa and SE Eskisehir. EF is representing a right lateral widespread intra-continental fault zone which has separated from central Anatolian block than Aegean extensional province. Kinematic evolution of this fault determined from inversion of both measured fault-slip vectors (by 209 fault-striae) and earthquake focal mechanism solutions (by 13 earthquakes). The inversion of slip vectors measured on fault planes indicate that a right lateral strike-slip stress regime is dominant having a consistent NW-trending Hmax(1) and NE-trending Hmin(3) axes. This stress regime changes old transpressional to young transtensional probably in Plio-Pleistocene time. Also, the earthquake focal mechanism inversions confirm that the regional transtensional stress regime continues into recent time. These stress states are characterized by NW and NE-trending 1 and 3 axes, respectively. However, local consistent NE-trending Hmin(3) extension directed normal faulting regime shows in relation with the development of the Eskisehir basins. Kinematic evolution and/or change in the stress regime probably resulted from (1) coeval influence of the forces due to subduction processes along the Cyprus and Hellenic arc in the south, (2) continental collision Anatolia/Arabian plate in the east, (3) anti-clockwise rotation and (4) westward escape and/or extrusion of the Anatolian Block.

  14. Evolution of the water regime of Phobos

    SciTech Connect

    Fanale, F.P.; Salvail, J.R. )

    1990-12-01

    In the present model of Phobos water regime evolution, a time-dependent solar insolation is influenced by both decreasing solar output over geologic time and the Mars and Phobos cycles of eccentricity and obliquity, which vary over 100,000-1,000,000 year time scales. The results presented address model cases which assume (1) a homogeneous distribution of water ice, and (2) a driving of water ice toward the surface by the internal thermal gradient near the poles. A two-dimensional model is used to compute temperatures, heat and vapor fluxes, and ice removal/deposition rates, for the case of uniform ice distribution throughout Phobos. The results obtained indicate that a substantial amount of vapor is produced within 1 km of the surface. 15 refs.

  15. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  16. Macrofaunal production along the UK continental shelf

    NASA Astrophysics Data System (ADS)

    Bolam, S. G.; Barrio-Frojan, C. R. S.; Eggleton, J. D.

    2010-10-01

    Estimates of secondary production ( P/ B ratio and total production) by macrobenthic communities across the UK continental shelf are presented. Values for individual sampling stations varied from 0.21 to 4.1 y - 1 for community P/ B and 3.1 to 897.2 kJ m - 2 y - 1 for total production. Such data fills an important gap pertaining to our understanding of the spatial variation in production estimates for this region. Benthic production estimates varied primarily at small (inter-station) scales (24 nm), although larger-scale differences were observed. In general, the highest production estimates were exhibited by benthic communities in Cardigan Bay (Irish Sea) and East English Channel, while the lowest estimates were observed for the mid- and northern North Sea areas. The former were typified by shallow, gravelly areas of seabed which exhibit high bed tidal stress and do not thermally stratify during the summer months. On average, annelids contribute an overwhelming majority of the total production with different regions varying in the relative contributions from other phyla such as molluscs, crustaceans and echinoderms. Spatial heterogeneity of sediment granulometric variables occurred primarily between stations while those of other variables (e.g., depth, stratification, and tidal bed stress) were more regional. Although a large proportion of the spatial variation in secondary production estimates was not explained by environmental characteristics, the data indicate that such relationships are scale-dependent. Average bed temperature was a significant factor in creating some of the observed differences at large spatial scales. The possible reasons why a larger proportion of the variation in production estimates was not explained by the present study are presented.

  17. Episodic Instabilities of Thick Continental Lithosphere (Invited)

    NASA Astrophysics Data System (ADS)

    Jaupart, C. P.; Fourel, L.; Farnetani, C. G.

    2009-12-01

    Although continental interiors are commonly described as stable, many have been subjected to major perturbations. The North American continent, for example, saw the formation or reactivation of four intracratonic basins (Williston, Hudson Bay, Illinois and Michigan) in the Paleozoic about 500 million years ago. These events occurred far from ocean basins and are not related to other tectonic events, and hence have usually been explained as late consequences of earlier orogenies or of mantle plumes impinging the base of the lithosphere. Why and how subsidence affected four neighbouring basins simultaneously in the Paleozoic has not been explained, however. Other important observations are that intracratonic basins and subsidence events tend to recur at the same locations, and that subsidence is rarely preceded by domal uplift. These observations can be explained by the behaviour of thick compositionally buoyant lithosphere that becomes unstable because it is being cooled from above. Laboratory analog experiments, stability theory and numerical simulations in 2-D and 3-D have been conducted to specify the necessary conditions for instability and to illustrate how flow develops and deforms the lithosphere. Numerical solutions accounting for temperature-dependent viscosity show that the compositional viscosity contrast between the lithospheric mantle and the underlying asthenosphere has only a weak effect on flow and deformation. Lithosphere behaviour depends on the Rayleigh number and the buoyancy ratio, which is equal to the ratio of compositional density contrast over the thermal density contrast through the unstable part of the lithosphere. Episodic instabilities are generated at small buoyancy numbers appropriate for geological conditions. Scaling laws for temperature-dependent viscosity fluids will be presented. Little uplift is generated by the instability because the hot upwelling asthenospheric mantle displaces compositionally buoyant colder lithospheric

  18. Flux of energy and essential elements through the continental shelf ecosystem. Progress report

    SciTech Connect

    Pomeroy, L.R.

    1981-11-30

    There are three distinct but not mutually exclusive areas of research in this contract, studies of intrusions of the west wall of the Gulf Stream onto the outer continental shelf, studies of the flux of materials across nearshore density fronts, and advances in understanding of the planktonic food web of the continental shelf. Studies of frontal events on the outer and inner continental shelf involve distinctive physical and chemical regimes and have proven to require distinctive biological approaches. The studies of the food web run through our work on both of the frontal regimes, but certain aspects have become subjects in their own right. We have developed a simulation model of the flux of energy through the continental shelf food web which we believe to be more realistic than previous ones of its type. We have examined several of the many roles of dissolved organic compounds in sea water which originate either from release by phytoplankton, digestive processes or metabolites of zooplankton, or extracellular digestion of microorganisms. Methods have been developed under this contract to measure both the chelating capacity of naturally occurring organic materials and the copper concentration in the water. It has been possible to characterize the effects, both toxic and stimulatory, of copper on photosynthesis of naturally occurring phytoplankton populations. It is possible to characterize in considerable detail the course of biological events associated with meanders of the Gulf Stream. We are now in a position to explain the limits to biological productivity of the outer continental shelf of the southeastern US and the reasons why that biological production moves through the food web in the characteristic way that it does.

  19. Continental volume and freeboard through geological time

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Reymer, A. P. S.

    1985-01-01

    The consequences of approximately constant freeboard for continental growth are explored using a model that relates the volumes of isostatically compensated continents and oceans to the secular decline in terrestrial heat flow. It is found that a post-Archean increase in freeboard by 200 m requires continental growth of only 10 percent, while a decrease in freeboard by 200 m during this same period necessitates a crustal growth of 40 percent. Shrinkage of the continental crust since the end of the Archean can be ruled out. Changes of more than 10 percent in post-Archean crustal thickness are highly unlikely.

  20. Potential evapotranspiration and continental drying

    NASA Astrophysics Data System (ADS)

    Milly, P. C. D.; Dunne, K. A.

    2016-10-01

    By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth’s land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation. `Offline’ analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century, despite an expected increase in global land precipitation. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming, underlies the drying trends, but may be a methodological artefact. Here we show that the PET estimator commonly used (the Penman-Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

  1. Quantifying Continental Margin Deformation North and South of the Opening of the Gulf of California—Evidence for Subduction Erosion?

    NASA Astrophysics Data System (ADS)

    Peterman, E. M.; Grove, M.; Kimbrough, D. L.

    2010-12-01

    A striking contrast exists in the geology of the continental margin north and south of the opening of the Gulf of California. For 1200km north of the Gulf opening, a reasonably well-preserved forearc region is associated with strongly magnetic 130-100 Ma plutonic rocks, volcanics and ophiolitic basement. This package of rocks is also coupled with a weakly magnetic eastern belt of 100-90 Ma tonalite and trondhjemite. In contrast, the southern continental margin bound by the Acapulco Trench lacks both a forearc basin and the 130-100 Ma plutonic belt. Instead, Late Cretaceous and Early to Middle Cenozoic granitoids crop out both along the coast and in the offshore region east of the Acapulco Trench, extending 1300 km south to 16°N. The geologic contrast between the northern and southern segments has been attributed to Cenozoic subduction erosion of the latter. The transition region between these two regimes occurs ~50 km northwest of the Gulf opening at 23°N along the Pacific coast of Baja California. North of Todos Santos, Late Cretaceous and younger strata depositionally overlie the western margin of the 130-100 Ma plutonic belt. The plutonic rocks are well-expressed in aeromagnetic images, even where buried. South of Todos Santos, 100-90 m.y. granitoids crop out along the coast and underlie the offshore Todos Santos basin; the strongly magnetic basement and undeformed forearc rocks are absent. Near Todos Santos, 94 Ma orthogneiss intercalated with upper amphibolite facies (garnet ± andalusite) Late Triassic(?) wallrocks are structurally juxtaposed above epidote amphibolite calc-schist of the mid-Cretaceous accretionary complex, suggesting significant forearc deformation. Previous 40Ar/39Ar data gathered south of Todos Santos reveal 5-10 m.y. of discordance between hornblende and biotite in the 100-90 m.y. granitoids. The age discordance could be related to either transient heating from 83-68 Ma granitoids located to the east or subduction erosion deformation

  2. Modeling the dynamics of continental shelf carbon.

    PubMed

    Hofmann, Eileen E; Cahill, Bronwyn; Fennel, Katja; Friedrichs, Marjorie A M; Hyde, Kimberly; Lee, Cindy; Mannino, Antonio; Najjar, Raymond G; O'Reilly, John E; Wilkin, John; Xue, Jianhong

    2011-01-01

    Continental margin systems are important contributors to global nutrient and carbon budgets. Effort is needed to quantify this contribution and how it will be modified under changing patterns of climate and land use. Coupled models will be used to provide projections of future states of continental margin systems. Thus, it is appropriate to consider the limitations that impede the development of realistic models. Here, we provide an overview of the current state of modeling carbon cycling on continental margins as well as the processes and issues that provide the next challenges to such models. Our overview is done within the context of a coupled circulation-biogeochemical model developed for the northeastern North American continental shelf region. Particular choices of forcing and initial fields and process parameterizations are used to illustrate the consequences for simulated distributions, as revealed by comparisons to observations using quantitative statistical metrics.

  3. Volatile components and continental material of planets

    NASA Technical Reports Server (NTRS)

    Florenskiy, K. P.; Nikolayeva, O. V.

    1986-01-01

    It is shown that the continental material of the terrestrial planets varies in composition from planet to planet according to the abundances and composition of true volatiles (H20, CO2, etc.) in the outer shells of the planets. The formation of these shells occurs very early in a planet's evolution when the role of endogenous processes is indistinct and continental materials are subject to melting and vaporizing in the absence of an atmosphere. As a result, the chemical properties of continental materials are related not only to fractionation processes but also to meltability and volatility. For planets retaining a certain quantity of true volatile components, the chemical transformation of continental material is characterized by a close interaction between impact melting vaporization and endogeneous geological processes.

  4. The Continental Plates are Getting Thicker.

    ERIC Educational Resources Information Center

    Kerr, Richard A.

    1986-01-01

    Reviews seismological studies that provide evidence of the existence of continental roots beneath the continents. Suggests, that through the collisions of plate tectonics, continents stabilized part of the mobile mantle rock beneath them to form deep roots. (ML)

  5. Coordination: southeast continental shelf studies. Progress report

    SciTech Connect

    Menzel, D.W.

    1981-02-01

    The objectives are to identify important physical, chemical and biological processes which affect the transfer of materials on the southeast continental shelf, determine important parameters which govern observed temporal and spatial varibility on the continental shelf, determine the extent and modes of coupling between events at the shelf break and nearshore, and determine physical, chemical and biological exchange rates on the inner shelf. Progress in meeting these research objectives is presented. (ACR)

  6. Freshwater peat on the continental shelf

    USGS Publications Warehouse

    Emery, K.O.; Wigley, R.L.; Bartlett, A.S.; Rubin, M.; Barghoorn, E.S.

    1967-01-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west.

  7. The Continental Margins Program in Georgia

    USGS Publications Warehouse

    Cocker, M.D.; Shapiro, E.A.

    1999-01-01

    From 1984 to 1993, the Georgia Geologic Survey (GGS) participated in the Minerals Management Service-funded Continental Margins Program. Geological and geophysical data acquisition focused on offshore stratigraphic framework studies, phosphate-bearing Miocene-age strata, distribution of heavy minerals, near-surface alternative sources of groundwater, and development of a PC-based Coastal Geographic Information System (GIS). Seven GGS publications document results of those investigations. In addition to those publications, direct benefits of the GGS's participation include an impetus to the GGS's investigations of economic minerals on the Georgia coast, establishment of a GIS that includes computer hardware and software, and seeds for additional investigations through the information and training acquired as a result of the Continental Margins Program. These addtional investigations are quite varied in scope, and many were made possible because of GIS expertise gained as a result of the Continental Margins Program. Future investigations will also reap the benefits of the Continental Margins Program.From 1984 to 1993, the Georgia Geologic Survey (GGS) participated in the Minerals Management Service-funded Continental Margins Program. Geological and geophysical data acquisition focused on offshore stratigraphic framework studies, phosphate-bearing Miocene-age strata, distribution of heavy minerals, near-surface alternative sources of groundwater, and development of a PC-based Coastal Geographic Information System (GIS). Seven GGS publications document results of those investigations. In addition to those publications, direct benefits of the GGS's participation include an impetus to the GGS's investigations of economic minerals on the Georgia coast, establishment of a GIS that includes computer hardware and software, and seeds for additional investigations through the information and training acquired as a result of the Continental Margins Program. These additional

  8. Freshwater peat on the continental shelf.

    PubMed

    Emery, K O; Wigley, R L; Bartlett, A S; Rubin, M; Barghoorn, E S

    1967-12-01

    Freshwater peats from the continental shelf off northeastern United States contain the same general pollen sequence as peats from ponds that are above sea level and that are of comparable radiocarbon ages. These peats indicate that during glacial times of low sea level terrestrial vegetation covered the region that is now the continental shelf in an unbroken extension from the adjacent land areas to the north and west. PMID:17801856

  9. Thermo-mechanical laboratory modeling of lithospheric-scale processes: the example of deep continental subduction and exhumation of UHP/LT rocks

    NASA Astrophysics Data System (ADS)

    Boutelier, David

    2010-05-01

    Purely mechanical (isothermal) laboratory experiments of continental subduction suggested existence of two principal regimes of this process, defined by the interplate pressure and inversely proportional to the pull-force. The pull-force itself depends on the difference between the average density of the subducting lithosphere and the surrounding mantle. In both high and low compression regimes, the continental crust reaches a critical depth proportional to its strength. Although these modeling results correspond quite well to geological data, it was purely mechanical and did not consider change in the mechanical properties during subduction. In nature, however, both pressure and temperature increase causing the strength of the subducting crust and mantle to be reduced by about one order of magnitude when reaching ~100 km-depth. Thermo-mechanical laboratory experiments revealed that such strong change deeply affect the subduction and exhumation processes. In the low compression regime, the crust can only subducts to ~120 km-depth in the asthenosphere. By then, it has become too hot and weak and undergoes large deformation, including upward ductile flow of the deeply subducted portions and a localized failure of the upper crust at depth of a few tens of kilometers. This deformation is accompanied by the delamination of the crustal and mantle layers. In the high compression regime, the deeply subducted continental crust reaches greater depth (~150 to 200 km) and maintains lower temperature when continental subduction triggers the subduction of the fore-arc block or the arc plate. 2-D thermo-mechanical laboratory modeling of continental subduction thus show that exhumation of deeply subducted continental crust is possible in the low compression regime (i.e. when the effective interplate pressure Pn is lower than the lithostatic pressure), while for the deeply subducted continental crust to be preserved at low temperature at great depth, the continental subduction

  10. Continental subduction induced tremor activity?

    NASA Astrophysics Data System (ADS)

    Tai, H. J.; Chen, K. H.; Ide, S.; Mouyen, M.; Byrne, T. B.

    2015-12-01

    Southern Central Range of Taiwan, a place where deep-seated tectonic tremors (a proxy of slow slip) and earthquake swarms are closely located in space and highly correlated in time, provides rare opportunity towards the understanding of physical mechanisms governing different style of slip. To identify tremor events, we used the identification scheme similar to Ide et al. (2015) but applied slightly different techniques: (1) Higher waveform cross-correlation coefficient (>0.6) (2) careful visual inspection for excluding local earthquakes and short-lasted event (duration < 60 s) (3) Signal to noise ratio higher than 1.2 and lower than 30 (4) No spatio-temporal clustering technique used. During the study period of 2007-2012, we identified 2320 tremor events with duration ranging from 60 s to 1550 s. They are located underneath southern Central Range, forming a NS-striking and SE-dipping pipe-like structure at a depth of 20-40 km. The up-dip extension of this tremor structure reaches an aseismic zone under the western flank of Central Range at shallow depths, where is an area characterized by high heat flow, low Vp and Vs anomaly. Such seismic gap was explained by the buoyancy induced crust detachment during continental subduction of Eurasian Plate. This detachment may open a new channel for hot and ductile material ascending to shallow depth, producing high temperatures along the way. This provides a common mechanism for down-dip tremor and up-dip shallow seismic gap along the same eastern dipping channel. In addition, the tremor events are found to be mostly occurred in high tides and exhibit higher correlation with tide data from west coast of Taiwan. This may again imply the association between tremor activity and subduction of Eurasian Plate.

  11. The Continental Crust: A Geophysical Approach

    NASA Astrophysics Data System (ADS)

    Christensen, Nikolas I.

    Nearly 80 years ago, Yugoslavian seismologist Andrija Mohorovicic recognized, while studying a Balkan earthquake, that velocities of seismic waves increase abruptly at a few tens of kilometers depth , giving rise to the seismological definition of the crust. Since that discovery, many studies concerned with the nature of both the continental and oceanic crusts have appeared in the geophysical literature.Recently, interest in the continental crust has cascaded. This is largely because of an infusion of new data obtained from major reflection programs such as the Consortium for Continental Reflection Profiling (COCORP) and British Institutions Reflection Profiling Syndicate (BIRPS) and increased resolution of refraction studies. In addition, deep continental drilling programs are n ow in fashion. The Continental Crust: A Geophysical Approach is a summary of present knowledge of the continental crust. Meissner has succeeded in writing a book suited to many different readers, from the interested undergraduate to the professional. The book is well documented , with pertinent figures and a complete and up-to-date reference list.

  12. Petroleum source potential of rocks dredged from the continental slope in the eastern Gulf of Alaska

    USGS Publications Warehouse

    Plafker, George; Claypool, George Edwin

    1979-01-01

    A bedrock dredging program by the R/V Sea Sounder in 1977 and 1978 along the continental slope in the eastern Gulf of Alaska revealed a previously unknown Eocene sedimentary sequence that includes argillaceous rocks with favorable petroleum source rock characteristics. Seven of 36 dredge hauls that sampled outcrop contain argillaceous rocks with more than l percent and as much as 1.64 percent organic carbon. Some of the rocks in samples of probable early Eocene age have undergone a thermal history that has resulted in generation of hydrocarbons. The organic matter appears to be hydrogen deficient, however, which could indicate that the rocks are more likely to be a source of gas rather than liquid hydrocarbon, unless the hydrogen loss is due to weathering. The Eocene rocks are associated with sandstone and conglomerate on the continental slope. They dip northward beneath younger Tertiary strata in the outer continental shelf where they could be an important petroleum source and exploratory target.

  13. MCNP/X TRANSPORT IN THE TABULAR REGIME

    SciTech Connect

    HUGHES, H. GRADY

    2007-01-08

    The authors review the transport capabilities of the MCNP and MCNPX Monte Carlo codes in the energy regimes in which tabular transport data are available. Giving special attention to neutron tables, they emphasize the measures taken to improve the treatment of a variety of difficult aspects of the transport problem, including unresolved resonances, thermal issues, and the availability of suitable cross sections sets. They also briefly touch on the current situation in regard to photon, electron, and proton transport tables.

  14. The operating regimes and basic control principles of SNPS Topaz''. [Cs

    SciTech Connect

    Makarov, A.N.; Volberg, M.S.; Grayznov, G.M.; Zhabotinsky, E.E.; Serbin, V.I. )

    1991-01-05

    The basic operating regimes of space nuclear power system (SNPS) Topaz'' are considered. These regimes include: prelaunch preparation and launch into working orbit, SNPS start-up to obtain desired electric power, nominal regime, SNPS shutdown. The main requirements for SNPS at different regimes are given, and the control algorithms providing these requirements are described. The control algorithms were chosen on the basis of theoretical studies and ground power tests of the SNPS prototypes. Topaz'' successful ground and flight tests allow to conclude that for SNPS of this type control algorithm providing required thermal state of cesium vapor supply system and excluding any possibility of discharge processes in current conducting elements is the most expedient at the start-up regime. At the nominal regime required electric power should be provided by maintenance of reactor current and fast-acting voltage regulator utilization. The limitation of the outlet coolant temperature should be foreseen also.

  15. Optimizing fluctuating thermal regime storage of developing Megachile rotundata

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The alfalfa leafcutting bee, Megachile rotundata, is the primary pollinator for alfalfa seed production in North America. Under current management practice developing pupae are incubated at 29ºC until the adults emerge for pollination. If unfavorable spring weather delays peak alfalfa bloom, bee m...

  16. Continental margin tectonics - Forearc processes

    SciTech Connect

    Lundberg, N.; Reed, D.L. )

    1991-01-01

    Recent studies of convergent plate margins and the structural development of forearc terranes are summarized in a critical review of U.S. research from the period 1987-1990. Topics addressed include the geometry of accretionary prisms (Coulomb wedge taper and vertical motion in response to tectonic processes), offscraping vs underplating or subduction, the response to oblique convergence, fluids in forearc settings, the thermal framework and the effects of fluid advection, and serpentinite seamounts. Also included is a comprehensive bibliography for the period.

  17. Merging of Rhine flow regimes

    NASA Astrophysics Data System (ADS)

    Boessenkool, Berry; Bronstert, Axel; Bürger, Gerd

    2016-04-01

    The Rhine flow regime is changing: (a) in the alpine nival regime, snow melt floods occur earlier in the year and (b) in the pluvial middle-Rhine regime, rainfall induced flood magnitudes rise. The seasonality of each is currently separated in time, but it is conceivable that this may shift due to climate change. If extremes of both flood types coincide, this would create a new type of hydrologic extreme with disastrous consequences. Quantifying the probability for a future overlap of pluvial and nival floods is therefore of high relevance to society and particularly to reinsurance companies. In order to investigate possible changes in magnitude and timing of flood types, we are developing a chain of physical models for spatio-temporal combination of flood probabilities. As input, we aim to use stochastically downscaled temperature and rainfall extremes from climate model weather projections. Preliminary research shows a six-week forward-shift of peak discharge at the nival gauge Maxau in the past century. The aim of presenting our early-stage work as a poster is to induce an exchange of ideas with fellow scientists in close research disciplines.

  18. Time-Lapse Zirconography of Continental Growth

    NASA Astrophysics Data System (ADS)

    Parman, S. W.

    2014-12-01

    When did the continents form? Peaks in the distributions of zircon U-Pb ages around 2.7, 1.9 and 1.2 Ga have been used as evidence for increased crustal growth rates at these times (growth pulses). The pulses appear linked to the formation of super-continents, with fundamental implications for the thermal evolution of the mantle. However, the age peaks could also be produced by variations in preservation/destruction rates, in which case the implications for the deep Earth are less direct. Here I use the novel approach of examining U-Pb zircon age spectra as a function of the age of the sediment in which the zircons are preserved. This produces time-lapse sequences of zircon age distributions, and presumably, crustal evolution. The database [1] is large enough (n>200,000) that time-lapse sequences can be constructed for each continent. To my knowledge, this approach has only been applied to the Australian zircon record [2]. The results are quite clear (Figure 1; circles are positions of peaks (x-axis) in detrital zircon U-Pb age spectra in different age sediments (y-axis), size of circle is proportional to the height of the peak). There are no major zircon U-Pb age peaks in the ranges 2.2-2.4 Ga and 1.3-1.6 Ga in any sediment of any age on any continent. While some crust was produced at these times, there is no evidence in the zircon record that substantial amounts of crust of these ages ever existed, suggesting that the troughs in the age spectra are due to substantial decreases in (though not cessation of) crustal production. In contrast, U-Pb age peaks between 2.5 and 2.7 Ga appear in sediments immediately after these times and persist in subsequent sedimentary records. The peak heights decrease steadily through time, indicating that crustal destruction is a significant process in modifying the zircon record, but is not responsible for producing the peaks. The same pattern is seen for age peaks at 1.6-2.1 and 1.0-1.3 Ga. Comparing the time-lapse results with Hf

  19. Continental drift and climate change drive instability in insect assemblages.

    PubMed

    Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

    2015-01-01

    Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale. PMID:26081036

  20. Continental drift and climate change drive instability in insect assemblages

    NASA Astrophysics Data System (ADS)

    Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

    2015-06-01

    Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region—one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

  1. Continental drift and climate change drive instability in insect assemblages.

    PubMed

    Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

    2015-06-17

    Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

  2. Heat flow and continental breakup: The Gulf of Elat (Aqaba)

    NASA Technical Reports Server (NTRS)

    Ben-Avraham, Z.; Vonherzen, R. P.

    1985-01-01

    Heat flow measurements were made in the major basins of the Gulf of Elat (Aqaba), northern Red Sea. The gulf is located at the southern portion of the Dead Sea rift which is a transform plate boundary. Gradient measurements at each site were made with a probe which allows multiple penetration of the bottom during a single deployment of the instrument. Thermal conductivity was determined by needle probe measurements on sedimentary cores. The mean heat flux, about 80 mWm(-2), is significantly above the continental mean, and probably also above that from the adjacent Sinai and Arabian continental blocks. The heat flow appears to increase from north to south. Such an increase may be related to the more advanced rifting stage of the Red Sea immediately to the south, which presently includes creation of an oceanic crust. This trend also corresponds to the general trend of the deep crustal structure in the gulf. Evidence from various geophysical fields suggest a gradual thinning of the crust towards the direction of the Red Sea where a normal oceanic crust exists. The heat flow data, together with other geophysical data, indicate a propagation of mature rifting activity from the Red Sea into the Gulf of Elat. This process is acting simultaneously with the transform motion along the Dead Sea rift.

  3. Thermal balance testing of the MSAT spacecraft

    NASA Technical Reports Server (NTRS)

    Samson, Serge; Choueiry, Elie; Pang, Kenneth

    1994-01-01

    This paper reports on the recently completed thermal balance/thermal vacuum testing of an MSAT satellite, the first satellite to provide mobile communications service for all of continental North America. MSAT is a two-spacecraft program, using a three-axis-stabilized HUGHES HS-601 series bus as the vehicle for the Canadian-designed payload. The thermal tests performed at the Canadian Space Agency's David Florida Laboratory in Ottawa, Canada, lasted approximately 32 days.

  4. Arctic and Antarctic Crustal Thickness and Continental Lithosphere Thinning from Gravity Inversion

    NASA Astrophysics Data System (ADS)

    Kusznir, Nick J.; Alvey, Andy; Vaughan, Alan P. M.; Ferraccioli, Fausto; Jordan, Tom A. R. M.; Roberts, Alan M.

    2013-04-01

    Mapping crustal thickness, continental lithosphere thinning and oceanic lithosphere distribution represents a substantial challenge for the Polar Regions. The Arctic region formed as a series of small distinct ocean basins leading to a complex distribution of oceanic crust, thinned continental crust and rifted continental margins. Antarctica, both peripherally and internally, experienced poly-phase rifting and continental breakup. We determine Moho depth, crustal basement thickness, continental lithosphere thinning and ocean-continent transition location for the Polar Regions using a gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction. The method is carried out in the 3D spectral domain and predicts Moho depth and incorporates a lithosphere thermal gravity anomaly correction. Ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. A correction to the predicted continental lithospheric thinning derived from gravity inversion is made for volcanic material addition produced by decompression melting during continental rifting and seafloor spreading. For the Arctic, gravity data used is from the NGA (U) Arctic Gravity Project, bathymetry is from IBCAO and sediment thickness is from a new regional compilation. For Antarctica and the Southern Oceans, data used are elevation and bathymetry, free-air gravity anomaly, ice and sediment thickness from Smith and Sandwell (2008), Sandwell and Smith (2008) and Laske and Masters (1997) respectively, supplemented by Bedmap2 data south of 60 degrees south. Using gravity anomaly inversion, we have produced the first comprehensive maps of crustal thickness and oceanic lithosphere distribution for the Arctic, Antarctica and the Southern Ocean. Our gravity inversion predicts thin crust and high continental lithosphere thinning factors in the Makarov, Podvodnikov, Nautilus and Canada

  5. Lithospheric buoyancy and continental intraplate stresses

    USGS Publications Warehouse

    Zoback, M.L.; Mooney, W.D.

    2003-01-01

    Lithospheric buoyancy, the product of lithospheric density and thickness, is an important physical property that influences both the long-term stability of continents and their state of stress. We have determined lithospheric buoyancy by applying the simple isostatic model of Lachenbruch and Morgan (1990). We determine the crustal portion of lithospheric buoyancy using the USGS global database of more than 1700 crustal structure determinations (Mooney et al., 2002), which demonstrates that a simple relationship between crustal thickness and surface elevation does not exist. In fact, major regions of the crust at or near sea level (0-200 m elevation) have crustal thicknesses that vary between 25 and 55 km. Predicted elevations due to the crustal component of buoyancy in the model exceed observed elevations in nearly all cases (97% of the data), consistent with the existence of a cool lithospheric mantle lid that is denser than the asthenosphere on which it floats. The difference between the observed and predicted crustal elevation is assumed to be equal to the decrease in elevation produced by the negative buoyancy of the mantle lid. Mantle lid thickness was first estimated from the mantle buoyancy and a mean lid density computed using a basal crust temperature determined from extrapolation of surface heat flow, assuming a linear thermal gradient in the mantle lid. The resulting values of total lithosphere thickness are in good agreement with thicknesses estimated from seismic data, except beneath cratonic regions where they are only 40-60% of the typical estimates (200-350 km) derived from seismic data. This inconsistency is compatible with petrologic data and tomography and geoid analyses that have suggested that cratonic mantle lids are ??? 1% less dense than mantle lids elsewhere. By lowering the thermally determined mean mantle lid density in cratons by 1%, our model reproduces the observed 200-350+ km cratonic lithospheric thickness. We then computed

  6. Upper mantle viscosity and dynamic subsidence of curved continental margins.

    PubMed

    Sacek, Victor; Ussami, Naomi

    2013-01-01

    Continental rifting does not always follow a straight line. Nevertheless, little attention has been given to the influence of rifting curvature in the evolution of extended margins. Here, using a three-dimensional model to simulate mantle dynamics, we demonstrate that the curvature of rifting along a margin also controls post-rift basin subsidence. Our results indicate that a concave-oceanward margin subsides faster than a convex margin does during the post-rift phase. This dynamic subsidence of curved margins is a result of lateral thermal conduction and mantle convection. Furthermore, the differential subsidence is strongly dependent on the viscosity structure. As a natural example, we analyse the post-rift stratigraphic evolution of the Santos Basin, southeastern Brazil. The differential dynamic subsidence of this margin is only possible if the viscosity of the upper mantle is >2-3 × 10(19) Pa s.

  7. Constraints on continental accretion from sedimentation

    NASA Technical Reports Server (NTRS)

    Abbott, Dallas

    1988-01-01

    Heat loss in the ancient Earth was discussed assuming that classical sea floor spreading was the only mechanism. This may be expressed as faster spreading or longer total ridge length. These have important implications as to the size and number of cratonic plates in the distant past, the degree to which they are flooded, the kinds of sediments and volcanics that would be expected, and the amount of recycling of continental material taking place. The higher proportion of marine sedimentary rocks and oceanic volcanics in the Archean, and the relative paucity of evaporites and continental volcanics may in part be due to smaller cratonic blocks. A model was developed of the percentage of continental flooding which utilizes round continents and a constant width of the zone of flooding. This model produces a reasonable good fit to the percentage of flooding on the present day continents.

  8. Cenozoic continental climatic evolution of Central Europe.

    PubMed

    Mosbrugger, Volker; Utescher, Torsten; Dilcher, David L

    2005-10-18

    Continental climate evolution of Central Europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation, and winter and summer temperatures. Although some regional effects occur, the European Cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments. During the last 45 million years, continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures. Correspondingly, Cenozoic cooling in Central Europe is directly associated with an increase of seasonality. In contrast, inferred Cenozoic mean annual precipitation remained relatively stable, indicating the importance of latent heat transport throughout the Cenozoic. Moreover, our data support the concept that changes in atmospheric CO2 concentrations, although linked to climate changes, were not the major driving force of Cenozoic cooling.

  9. Breddin's graph for tectonic regimes

    NASA Astrophysics Data System (ADS)

    Célérier, Bernard; Séranne, Michel

    2001-05-01

    A simple graphical method is proposed to infer the tectonic regime from a fault and slip data set. An abacus is overlaid on a plot of the rake versus strike of the data. This yields the horizontal principal stress directions and a constraint on the stress tensor aspect ratio, in a manner similar to Breddin's graph for two-dimensional strain analysis. The main requirement is that one of the principal stress directions is close to the vertical. This method is illustrated on monophase synthetic and natural data, but is also expected to help sort out multiphase data sets.

  10. Gas hydrates of outer continental margins

    SciTech Connect

    Kvenvolden, K.A. )

    1990-05-01

    Gas hydrates are crystalline substances in which a rigid framework of water molecules traps molecules of gas, mainly methane. Gas-hydrate deposits are common in continental margin sediment in all major oceans at water depths greater than about 300 m. Thirty-three localities with evidence for gas-hydrate occurrence have been described worldwide. The presence of these gas hydrates has been inferred mainly from anomalous lacoustic reflectors seen on marine seismic records. Naturally occurring marine gas hydrates have been sampled and analyzed at about tensites in several regions including continental slope and rise sediment of the eastern Pacific Ocean and the Gulf of Mexico. Except for some Gulf of Mexico gas hydrate occurrences, the analyzed gas hydrates are composed almost exclusively of microbial methane. Evidence for the microbial origin of methane in gas hydrates includes (1) the inverse relation between methane occurence and sulfate concentration in the sediment, (2) the subparallel depth trends in carbon isotopic compositions of methane and bicarbonate in the interstitial water, and (3) the general range of {sup 13}C depletion ({delta}{sub PDB}{sup 13}C = {minus}90 to {minus}60 {per thousand}) in the methane. Analyses of gas hydrates from the Peruvian outer continental margin in particular illustrate this evidence for microbially generated methane. The total amount of methane in gas hydrates of continental margins is not known, but estimates of about 10{sup 16} m{sup 3} seem reasonable. Although this amount of methane is large, it is not yet clear whether methane hydrates of outer continental margins will ever be a significant energy resource; however, these gas hydrates will probably constitute a drilling hazard when outer continental margins are explored in the future.

  11. The New English Quality Assurance Regime

    ERIC Educational Resources Information Center

    Brown, Roger

    2011-01-01

    England is developing a new quality assurance regime that will come into effect in October 2011. A new funding regime will operate from the following year, together with new rules to ease the participation of private higher education providers. This article describes and analyses the new quality and funding regimes. It argues that the greater…

  12. Fatty acids on continental sulfate aerosol particles

    NASA Astrophysics Data System (ADS)

    Tervahattu, H.; Juhanoja, J.; Vaida, V.; Tuck, A. F.; Niemi, J. V.; Kupiainen, K.; Kulmala, M.; VehkamäKi, H.

    2005-03-01

    Surface analyses of atmospheric aerosols from different continental sources, such as forest fires and coal and straw burning, show that organic surfactants are found on such aerosols. The predominant organic species detected by time-of-flight secondary ion mass spectrometry on the sulfate aerosols are fatty acids of different carbon chain length up to the C32 acid. These observations are consistent with literature accounts of functional group analysis of bulk samples, but this is the first direct evidence of fatty acid films on the surface of sulfate aerosols. Surface analysis leads to the conclusion that fatty acid films on continental aerosols may be more common than has been previously suggested.

  13. MAGSAT anomaly map and continental drift

    NASA Technical Reports Server (NTRS)

    Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.

    1981-01-01

    Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.

  14. Continental drift under the Third Reich.

    PubMed

    Buffetaut, Eric

    2003-12-01

    Contrary to what happened in many other countries in the 1930s and 1940s, Alfred Wegener's theory of continental drift was not generally rejected in Nazi Germany, although several leading German geologists of the time did not accept it. It was actually presented as the modern view of Earth history in books and magazine articles aimed at the general public. Although outlandish geological theories such as Hörbiger's Welteislehre were favoured by some Nazi dignitaries, they were not widely accepted in scientific circles. On the other hand, continental drift received official support under the Third Reich, at a time when it was ignored or ridiculed by most earth scientists outside Germany.

  15. Do the pyramids show continental drift?

    PubMed

    Pawley, G S; Abrahamsen, N

    1973-03-01

    The mystery of the orientation of the Great Pyramids of Giza has remained unexplained for many decades. The general alignment is 4 minutes west of north. It is argued that this is not a builders' error but is caused by movement over the centuries. Modern theories of continental drift do not predict quite such large movements, but other causes of polar wandering give even smaller shifts. Thus, continental drift is the most likely explanation, although somewhat implausible, especially as relevant measurements have been made over a 50-year period, whereas geophysical measurements of sea-floor spreading relate to million-year time scales.

  16. Thermal expansion in nanoresonators

    NASA Astrophysics Data System (ADS)

    Mancardo Viotti, Agustín; Monastra, Alejandro G.; Moreno, Mariano F.; Florencia Carusela, M.

    2016-08-01

    Inspired by some recent experiments and numerical works related to nanoresonators, we perform classical molecular dynamics simulations to investigate the thermal expansion and the ability of the device to act as a strain sensor assisted by thermally-induced vibrations. The proposed model consists in a chain of atoms interacting anharmonically with both ends clamped to thermal reservoirs. We analyze the thermal expansion and resonant frequency shifts as a function of temperature and the applied strain. For the transversal modes the shift is approximately linear with strain. We also present analytical results from canonical calculations in the harmonic approximation showing that thermal expansion is uniform along the device. This prediction also works when the system operates in a nonlinear oscillation regime at moderate and high temperatures.

  17. Adaptation in Collaborative Governance Regimes

    NASA Astrophysics Data System (ADS)

    Emerson, Kirk; Gerlak, Andrea K.

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  18. Different regimes of dynamic wetting

    NASA Astrophysics Data System (ADS)

    Gustav, Amberg; Wang, Jiayu; Do-Quang, Minh; Shiomi, Junichiro; Physiochemical fluid mechanics Team; Maruyama-Chiashi Laboratory Team

    2014-11-01

    Dynamic wetting, as observed when a droplet contacts a dry solid surface, is important in various engineering processes, such as printing, coating, and lubrication. Our overall aim is to investigate if and how the detailed properties of the solid surface influence the dynamics of wetting. Here we discuss how surface roughness influences the initial dynamic spreading of a partially wetting droplet by studying the spreading on a solid substrate patterned with microstructures just a few micrometers in size. This is complemented by matching numerical simulations. We present a parameter map, based on the properties of the liquid and the solid surface, which identifies qualitatively different spreading regimes, where the spreading speed is limited by either the liquid viscosity, the surface properties, or the liquid inertia. The peculiarities of the different spreading regimes are studied by detailed numerical simulations, in conjuction with experiments. This work was financially supported in part by, the Japan Society for the Promotion of Science (J.W. and J.S) and Swedish Governmental Agency for Innovation Systems (M.D.-Q. and G.A).

  19. Adaptation in collaborative governance regimes.

    PubMed

    Emerson, Kirk; Gerlak, Andrea K

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  20. Modeling Continental Growth and Mantle Hydration in Earth's Evolution and the Impact of Life

    NASA Astrophysics Data System (ADS)

    Höning, Dennis; Spohn, Tilman

    2016-04-01

    The evolution of planets with plate tectonics is significantly affected by several intertwined feedback cycles. On Earth, interactions between atmosphere, hydrosphere, biosphere, crust, and interior determine its present day state. We here focus on the feedback cycles including the evolutions of mantle water budget and continental crust, and investigate possible effects of the Earth's biosphere. The first feedback loop includes cycling of water into the mantle at subduction zones and outgassing at volcanic chains and mid-ocean ridges. Water is known to reduce the viscosity of mantle rock, and therefore the speed of mantle convection and plate subduction will increase with the water concentration, eventually enhancing the rates of mantle water regassing and outgassing. A second feedback loop includes the production and erosion of continental crust. Continents are formed above subduction zones, whose total length is determined by the total size of the continents. Furthermore, the total surface area of continental crust determines the amount of eroded sediments per unit time. Subducted sediments affect processes in subduction zones, eventually enhancing the production rate of new continental crust. Both feedback loops affect each other: As a wet mantle increases the speed of subduction, continental production also speeds up. On the other hand, the total length of subduction zones and the rate at which sediments are subducted (both being functions of continental coverage) affect the rate of mantle water regassing. We here present a model that includes both cycles and show how the system develops stable and unstable fixed points in a plane defined by mantle water concentration and surface of continents. We couple these feedback cycles to a parameterized thermal evolution model that reproduces present day observations. We show how Earth has been affected by these feedback cycles during its evolution, and argue that Earth's present day state regarding its mantle water

  1. Small quantum absorption refrigerator in the transient regime: Time scales, enhanced cooling, and entanglement

    NASA Astrophysics Data System (ADS)

    Brask, Jonatan Bohr; Brunner, Nicolas

    2015-12-01

    A small quantum absorption refrigerator, consisting of three qubits, is discussed in the transient regime. We discuss time scales for coherent dynamics, damping, and approach to the steady state, and we study cooling and entanglement. We observe that cooling can be enhanced in the transient regime, in the sense that lower temperatures can be achieved compared to the steady-state regime. This is a consequence of coherent dynamics but can occur even when this dynamics is strongly damped by the dissipative thermal environment, and we note that precise control over couplings or timing is not needed to achieve enhanced cooling. We also show that the amount of entanglement present in the refrigerator can be much larger in the transient regime compared to the steady state. These results are of relevance to future implementations of quantum thermal machines.

  2. Small quantum absorption refrigerator in the transient regime: Time scales, enhanced cooling, and entanglement.

    PubMed

    Brask, Jonatan Bohr; Brunner, Nicolas

    2015-12-01

    A small quantum absorption refrigerator, consisting of three qubits, is discussed in the transient regime. We discuss time scales for coherent dynamics, damping, and approach to the steady state, and we study cooling and entanglement. We observe that cooling can be enhanced in the transient regime, in the sense that lower temperatures can be achieved compared to the steady-state regime. This is a consequence of coherent dynamics but can occur even when this dynamics is strongly damped by the dissipative thermal environment, and we note that precise control over couplings or timing is not needed to achieve enhanced cooling. We also show that the amount of entanglement present in the refrigerator can be much larger in the transient regime compared to the steady state. These results are of relevance to future implementations of quantum thermal machines.

  3. Expanding Ice Sheets on the Antarctic Peninsula during the Plio/Pleistocene Recorded in Continental Rise Sediment Drifts

    NASA Astrophysics Data System (ADS)

    Cowan, E. A.; Hillenbrand, C.

    2007-12-01

    Sediment drifts on the continental rise west of the Antarctic Peninsula are located within 125 km from the continental shelf edge, the main contributor of terrigenous sediment during both glacial and interglacial periods. The composition of drift deposits continuously recorded changes in ice sheet volume and thermal regime as well as sea surface temperatures (SSTs) and sea ice extent. The coarse-grained terrigenous sediment (pebbles and coarse sand), a proxy for iceberg-rafted debris (IRD), was analyzed in sediments spanning the last 3.1 m.y. at Ocean Drilling Program (ODP) Sites 1101 and 1096. IRD is deposited in both glacial intervals, dominated by fine-grained laminated mud and interglacial units consisting of bioturbated muds enriched in biogenic components. Contents of biogenic opal, which reflect diatom abundance, are relatively high from 3.1-2.2 Ma. Calcareous nannofossils are present within interglacial sediments from 2.2-0.76 Ma. Both findings suggest warm SSTs and limited sea ice over the drifts during interglacial periods before the Late Pleistocene. Quartz grains picked from the IRD fraction and imaged with a scanning electron microscope (SEM) show an abrupt change in surface microtextures at 1.35 Ma. During the Late Pliocene to Early Pleistocene, many quartz grains are completely weathered and only a few show signs of crushing and abrasion, indicating that glaciers were too small to inundate the Antarctic Peninsula topography. Debris shed from mountain peaks was transported supraglacially or englacially allowing weathered grains to pass unmodified through the glaciers. Glaciers expanded in size during glacial periods from 1.35-0.76 Ma. The IRD accumulation during those periods was very high and diverse dropstone lithologies document supply from sources throughout the Antarctica Peninsula. Conditions that spawned the large polar ice sheet identified at the Last Glacial Maximum have been present on the Antarctic Peninsula during glacial periods since

  4. He-accreting white dwarfs: accretion regimes and final outcomes

    NASA Astrophysics Data System (ADS)

    Piersanti, L.; Tornambé, A.; Yungelson, L. R.

    2014-12-01

    The behaviour of carbon-oxygen (CO) white dwarfs (WDs) subject to direct helium accretion is extensively studied. We aim to analyse the thermal response of an accreting WD to mass deposition at different timescales. The analysis has been performed for initial WD masses and accretion rates in the range 0.60-1.02 M⊙ and 10-9-10-5 M⊙ yr-1, respectively. Thermal regimes in the parameter space MWD-dot{M}_He leading to formation of red-giant-like structures, steady burning of He, and mild, strong and dynamical flashes have been identified and the transition between these regimes has been studied in detail. In particular, the physical properties of WDs experiencing the He-flash accretion regime have been investigated to determine the mass retention efficiency as a function of the accretor total mass and accretion rate. We also discuss to what extent the building up of a He-rich layer via H burning could be described according to the behaviour of models accreting He-rich matter directly. Polynomial fits to the obtained results are provided for use in binary population synthesis computations. Several applications for close binary systems with He-rich donors and CO WD accretors are considered and the relevance of the results for interpreting He novae is discussed.

  5. A biogeochemical paradigm for reconstruction of past shelf sea regimes

    NASA Astrophysics Data System (ADS)

    Jago, C. F.; Jones, S. E.

    2003-04-01

    A new paradigm is proposed for reconstruction of past continental shelf regimes that were driven by tides. It is argued that the combined impact of dynamics, nutrients, and suspended matter produces strong spatial gradients in biogeochemical fluxes to the seabed. These gradients produce diagnostic signatures in seabed sediments so that mixed, frontal, and stratified regions of past shelf regimes can be reconstructed using appropriate microbiological and isotopic proxies in the sediments. Much of the algal production in summer takes place in the thermocline and at tidal mixing fronts. The themocline stimulates plankton growth due to availability of light and nutrients and optimal conditions occur at fronts due to enhanced lateral mixing. Organic matter generated by algae is incorporated in suspended particulate matter (SPM) with most of the mass in large aggregates which settle to the seabed. Aggregation is facilitated by carbohydrates produced by the algae. Aggregates deposit on the seabed as benthic fluff. The potential for pelagic remineralisation of SPM is reduced in frontal regions due to rapid settling and limited resuspension. Combination of enhanced supply and rapid export means that benthic fluff deposition per unit area of seabed is greatest in frontal regions. Subsequent resuspension combined with cross-frontal mixing in summer and storms in winter should disperse fluff away from fronts. Net deposition of this material is most likely on the stratified side of the frontal regions. The end result is that there are differences in benthic fluff deposition in mixed, frontal and stratified regions. These differences impact on seabed exchanges. Fluff controls benthic oxygen demand (BOD) and determines whether biogeochemical exchanges are oxic or anoxic. Diagnostic indicators of water column and seabed regimes are preserved in the sediment record. For example, gradients in BOD and temperature are reflected in benthic foraminifera assemblages and stable isotope

  6. Geometries of hyperextended continental crust in northeastern continental brazilian margin: insights from potential field and seismic interpretation

    NASA Astrophysics Data System (ADS)

    Magalhães, José; Barbosa, José; Ribeiro, Vanessa; Oliveira, Jefferson; Filho, Osvaldo; Buarque, Bruno

    2016-04-01

    The study region encompasses a set of three basins located at Northeast Brazilian continental margin: Pernambuco (south sector), Paraíba and Natal platform (north sector). These basins were formed during the last stage of separation between South America and African plates during Cretaceous. The continental breakup in these regions occurred probably during the Middle-Upper Albian (~102 m.y). The adjacent basement rocks belong to Borborema Province (BP), which was formed due a complex superposition between Pre-Cambrian orogenic cycles. The structural framework of BP is dominated by large shear zones that divided this province in three main tectonic domains: South, Central and North. The Pernambuco Basin is located in the South Domain and the Paraíba and Natal platform basins are related to the Central Domain. The tectonic and magmatic evolution of the Pernambuco Basin was influenced by oblique rifting (~ 35° to rift axis) and a thermal anomaly probably caused by the Santa Helena hotspot. The north sector represents a continental shelf characterized by basement high with a narrow platform and an abrupt shelf break on transition to the abyssal plain. The continental platform break of this sector was parallel to the rift axis. In this way, we present a regional structural interpretation of these sectors of Brazilian rifted margin based on interpretation and 2D forward modeling of potential field and 2D seismic data. The magnetic maps (Reduction to magnetic pole and Analytic signal) revealed the influence of an alternating pattern of large narrow magnetic and non-magnetic lineaments, oriented NE-SW, E-W and NW-SE. In the Pernambuco Basin these lineaments (NE-SW and E-W) are related to shear zones in the hyperextended basement which is interpreted as a continuation of the granitic-gneissic and metasedimentary rocks of the South Domain of BP. The Paraíba and Natal platform basins show a slight change in the orientation of structures trending E-W (shear zones in

  7. Plate Tectonics and Continental Drift: Classroom Ideas.

    ERIC Educational Resources Information Center

    Stout, Prentice K.

    1983-01-01

    Suggests various classroom studies related to plate tectonics and continental drift, including comments on and sources of resource materials useful in teaching the topics. A complete list of magazine articles on the topics from the Sawyer Marine Resource Collection may be obtained by contacting the author. (JN)

  8. Elephant teeth from the atlantic continental shelf

    USGS Publications Warehouse

    Whitmore, F.C.; Emery, K.O.; Cooke, H.B.S.; Swift, D.J.P.

    1967-01-01

    Teeth of mastodons and mastodons have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, and relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25.000 years.

  9. Deep observation and sampling of the earth's continental crust (DOSECC): Continental scientific drilling workshop

    SciTech Connect

    Not Available

    1985-01-01

    Research summaries are presented of ongoing or proposed deep drilling programs to explore hydrothermal systems, buried astroblemes, continental crust, magma systems, mountain belt tectonics, subduction zones, and volcanoes. Separate abstracts have been prepared for individual papers. (ACR)

  10. 75 FR 61512 - Outer Continental Shelf Official Protraction Diagrams

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... Outer Continental Shelf Official Protraction Diagrams (OPDs) located within Atlantic Ocean areas, with... Bureau of Ocean Energy Management, Regulation and Enforcement Outer Continental Shelf Official Protraction Diagrams AGENCY: Bureau of Ocean Energy Management, Regulation and Enforcement, Interior....

  11. The fate of mafic and ultramafic intrusions in the continental crust

    NASA Astrophysics Data System (ADS)

    Roman, Alberto; Jaupart, Claude

    2016-11-01

    Geochemical and petrological data indicate that the bulk continental crust results from the fractionation of basaltic magmas followed by the foundering of residual mafic cumulates. Structural and geological evidence for foundering has been elusive and it is argued that it lies in the shapes of mafic intrusions that have been preserved in the crust. Numerical calculations of visco-elasto-plastic deformation induced by a dense intrusive body in continental crust have been carried out for a wide range of physical conditions. Three regimes are defined on the basis of the amount of dense material that remains at the original emplacement level as well as on the shape of the residual body. With strong encasing rocks, the intrusion deforms weakly in a sagging regime characterized by downwarping of the floor. At the other extreme, the intrusion sinks through weak surroundings, leaving behind a very small volume of material. In an intermediate regime, the intrusion does not sink wholesale and undergoes a dramatic change of shape. A residual body is preserved with a shape that depends on the aspect ratio of the initial intrusion. For aspect ratios of order one, the residual body is funnel-shaped above a thin and deep vertical extension. For the small aspect ratios that typify large igneous complexes such as the Bushveld, South Africa, the residual body is characterized by thick peripheral lobes with inward-dipping igneous layers and a thinner central area that has lost some of the basal cumulates. The transitions between these regimes depend on the rheology and temperature of encasing rocks.

  12. When do jammed sphere packings have a valid linear regime?

    NASA Astrophysics Data System (ADS)

    Goodrich, Carl; Liu, Andrea; Nagel, Sidney

    2014-03-01

    The physics of jamming can be studied in its purest form in packings of soft spheres at zero temperature. One of the successes of this approach is that bulk material properties, such as the elastic moduli or density of normal modes, can be predicted solely from the distance of the system to the jamming transition. Such properties are both defined and measured in the linear-response regime. It is thus tacitly assumed that the harmonic approximation to the local energy landscape can capture the meaningful physics, and it is therefore essential to delineate when this assumption is valid. We will examine the regime of validity of the harmonic approximation in jammed sphere packings as a function of system size and density. We will also discuss the crossover from linear response of the zero-temperature jammed solid to thermal behavior at nonzero temperatures.

  13. On the heat capacity of elements in WMD regime

    NASA Astrophysics Data System (ADS)

    Hamel, Sebatien

    2014-03-01

    Once thought to get simpler with increasing pressure, elemental systems have been discovered to exhibit complex structures and multiple phases at high pressure. For carbon, QMD/PIMC simulations have been performed and the results are guiding alternative modelling methodologies for constructing a carbon equation-of-state covering the warm dense matter regime. One of the main results of our new QMD/PIMC carbon equation of state is that the decay of the ion-thermal specific heat with temperature is much faster than previously expected. An important question is whether this is only found in carbon and not other element. In this presentation, based on QMD calculations for several elements, we explore trends in the transition from condensed matter to warm dense matter regime.

  14. Growth of early continental crust by partial melting of eclogite.

    PubMed

    Rapp, Robert P; Shimizu, Nobumichi; Norman, Marc D

    2003-10-01

    The tectonic setting in which the first continental crust formed, and the extent to which modern processes of arc magmatism at convergent plate margins were operative on the early Earth, are matters of debate. Geochemical studies have shown that felsic rocks in both Archaean high-grade metamorphic ('grey gneiss') and low-grade granite-greenstone terranes are comprised dominantly of sodium-rich granitoids of the tonalite-trondhjemite-granodiorite (TTG) suite of rocks. Here we present direct experimental evidence showing that partial melting of hydrous basalt in the eclogite facies produces granitoid liquids with major- and trace-element compositions equivalent to Archaean TTG, including the low Nb/Ta and high Zr/Sm ratios of 'average' Archaean TTG, but from a source with initially subchondritic Nb/Ta. In modern environments, basalts with low Nb/Ta form by partial melting of subduction-modified depleted mantle, notably in intraoceanic arc settings in the forearc and back-arc regimes. These observations suggest that TTG magmatism may have taken place beneath granite-greenstone complexes developing along Archaean intraoceanic island arcs by imbricate thrust-stacking and tectonic accretion of a diversity of subduction-related terranes. Partial melting accompanying dehydration of these generally basaltic source materials at the base of thickened, 'arc-like' crust would produce compositionally appropriate TTG granitoids in equilibrium with eclogite residues.

  15. Continental-Scale Convection-Permitting Regional Climate Modeling

    NASA Astrophysics Data System (ADS)

    Prein, A. F.; Rasmussen, R.; Clark, M. P.; Ikeda, K.; Liu, C.

    2015-12-01

    Convection-permitting regional climate models (CPCMs) have proven to be useful for down scaling large-scale climate information to regional and local scales. They add value to the representation of impact relevant parameters such as near surface temperature, precipitation, and the representation of extremes by improving local scale processes such as soil atmosphere interactions, snowpack dynamics, or the representation of deep convection. Due to their high computational costs most CPCM simulations have been restricted to small domains on the order of a few 100 km. On such small domains CPCMs might not reach their full potential because they are restricted by the lateral boundary forcing and may not be able to spin up properly. In this study we investigate the ability of a continental scale CPCM to simulate climate conditions in the Contiguous United States within the period October 2000 to December 2010. We downscale ERA-Interim reanalysis data to a horizontal grid spacing of 4 km with the Weather Research and Forecasting (WRF) Model that allows an explicit treatment of deep convection. The model performance is analyzed in different synoptic-scale weather regimes, which enables a process-oriented evaluation. The significance of model biases in simulated precipitation and temperature is investigated by including observational uncertainties in the analysis. Significant biases are further investigated and possible error sources are discussed. The goal of this study is to provide a benchmark on the state-of-the-art convection-permitting regional climate modeling and to give guidance for future model development.

  16. Hydromechanical effects of continental glaciation on groundwater systems

    USGS Publications Warehouse

    Neuzil, C.E.

    2012-01-01

    Hydromechanical effects of continental ice sheets may involve considerably more than the widely recognized direct compression of overridden terrains by ice load. Lithospheric flexure, which lags ice advance and retreat, appears capable of causing comparable or greater stress changes. Together, direct and flexural loading may increase fluid pressures by tens of MPa in geologic units unable to drain. If so, fluid pressures in low-permeability formations subject to glaciation may have increased and decreased repeatedly during cycles of Pleistocene glaciation and can again in the future. Being asynchronous and normally oriented, direct and flexural loading presumably cause normal and shear stresses to evolve in a complex fashion through much or all of a glacial cycle. Simulations of fractured rock predict permeability might vary by two to three orders of magnitude under similar stress changes as fractures at different orientations are subjected to changing normal and shear stresses and some become critically stressed. Uncertainties surrounding these processes and their interactions, and the confounding influences of surface hydrologic changes, make it challenging to delineate their effects on groundwater flow and pressure regimes with any specificity. To date, evidence for hydromechanical changes caused by the last glaciation is sparse and inconclusive, comprising a few pressure anomalies attributed to the removal of direct ice load. This may change as more data are gathered, and understanding of relevant processes is refined.

  17. Nicolas and Eel submarine fans, California continental borderland

    SciTech Connect

    Reynolds, S.; Gorsline, D.S.

    1987-04-01

    Nicolas and Eel Submarine Fans occur in the San Nicolas basin - an outer basin of the California continental borderland that has a low sedimentation rate. Nicolas Fan lies southeast of San Nicolas Island and the broad San Nicolas Bank. The upper fan is characterized by numerous channels. The midfan region may be divided into three distinct areas: a central midfan and two subfans. The central midfan deposition system is typical of Normark's suprafan. The subfans are essentially flat, sandy lobes. Eel Fan lies west of San Clemente Island and is fed by an erosional valley. Its midfan region may also be characterized as a flat, sandy lobe. Box-core data show that holocene turbidity currents have occurred on the central Nicolas Fan, whereas the subfans and Eel Fan are nearly inactive. The local tectonic regime influences these fans by determining slope trends, creating bathymetric obstacles, controlling canyon location, and triggering mass movements. Sea level changes affect sedimentation patterns of the fans by increasing the mean grain size and the amount of sediment delivered to the fan during lowstands. These changes may, in turn, affect the morphology of the fan. The characteristics of these fans represent variations of the generalized fan models described in the literature. 12 figures, 1 table.

  18. The limits of seaward spreading and slope instability at the continental margin offshore Mt Etna, imaged by high-resolution 2D seismic data

    NASA Astrophysics Data System (ADS)

    Gross, Felix; Krastel, Sebastian; Geersen, Jacob; Behrmann, Jan Hinrich; Ridente, Domenico; Chiocci, Francesco Latino; Bialas, Jörg; Papenberg, Cord; Cukur, Deniz; Urlaub, Morelia; Micallef, Aaron

    2016-01-01

    Mount Etna is the largest active volcano in Europe. Instability of its eastern flank is well documented onshore, and continuously monitored by geodetic and InSAR measurements. Little is known, however, about the offshore extension of the eastern volcano flank, defining a serious shortcoming in stability models. In order to better constrain the active tectonics of the continental margin offshore the eastern flank of the volcano, we acquired a new high-resolution 2D reflection seismic dataset. The data provide new insights into the heterogeneous geology and tectonics at the continental margin offshore Mt Etna. The submarine realm is characterized by different blocks, which are controlled by local- and regional tectonics. A compressional regime is found at the toe of the continental margin, which is bound to a complex basin system. Both, the clear link between on- and offshore tectonic structures as well as the compressional regime at the easternmost flank edge, indicate a continental margin gravitational collapse as well as spreading to be present at Mt Etna. Moreover, we find evidence for the offshore southern boundary of the moving flank, which is identified as a right lateral oblique fault north of Catania Canyon. Our findings suggest a coupled volcano edifice/continental margin instability at Mt Etna, demonstrating first order linkage between on- and offshore tectonic processes.

  19. Testing Predictions of Continental Insulation using Oceanic Crustal Thicknesses

    NASA Astrophysics Data System (ADS)

    Hoggard, Mark; Shorttle, Oliver; White, Nicky

    2016-04-01

    The thermal blanketing effect of continental crust has been predicted to lead to elevated temperatures within the upper mantle beneath supercontinents. Initial break-up is associated with increased magmatism and the generation of flood basalts. Continued rifting and sea-floor spreading lead to a steady reduction of this thermal anomaly. Recently, evidence in support of this behaviour has come from the major element geochemistry of mid-ocean ridge basalts, which suggest excess rifting temperatures of ˜ 150 °C that decay over ˜ 100 Ma. We have collated a global inventory of ˜ 1000 seismic reflection profiles and ˜ 500 wide-angle refraction experiments from the oceanic realm. Data are predominantly located along passive margins, but there are also multiple surveys in the centres of the major oceanic basins. Oceanic crustal thickness has been mapped, taking care to avoid areas of secondary magmatic thickening near seamounts or later thinning such as across transform faults. These crustal thicknesses are a proxy for mantle potential temperature at the time of melt formation beneath a mid-ocean ridge system, allowing us to quantify the amplitude and duration of thermal anomalies generated beneath supercontinents. The Jurassic break-up of the Central Atlantic and the Cretaceous rifting that formed the South Atlantic Ocean are both associated with excess temperatures of ˜ 50 °C that have e-folding times of ˜ 50 Ma. In addition to this background trend, excess temperatures reach > 150 °C around the region of the Rio Grande Rise, associated with the present-day Tristan hotspot. The e-folding time of this more local event is ˜ 10 Ma, which mirrors results obtained for the North Atlantic Ocean south of Iceland. In contrast, crustal thicknesses from the Pacific Ocean reveal approximately constant potential temperature through time. This observation is in agreement with predictions, as the western Pacific was formed by rifting of an oceanic plate. In summary

  20. Surface heat flow measurements from the East Siberian continental slope and southern Lomonosov Ridge, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    O'Regan, Matt; Preto, Pedro; Stranne, Christian; Jakobsson, Martin; Koshurnikov, Andrey

    2016-05-01

    Surface heat flow data in the Arctic Ocean are needed to assess hydrocarbon and methane hydrate distributions, and provide constraints into the tectonic origins and nature of underlying crust. However, across broad areas of the Arctic, few published measurements exist. This is true for the outer continental shelf and slope of the East Siberian Sea, and the adjoining deep water ridges and basins. Here we present 21 new surface heat flow measurements from this region of the Arctic Ocean. On the Southern Lomonosov Ridge, the average measured heat flow, uncorrected for effects of sedimentation and topography, is 57 ± 4 mW/m2 (n = 4). On the outer continental shelf and slope of the East Siberian Sea (ESS), the average is 57 ± 10 mW/m2 (n = 16). An anomalously high heat flow of 203 ± 28 mW/m2 was measured at a single station in the Herald Canyon. With the exception of this high heat flow, the new data from the ESS are consistent with predictions for thermally equilibrated lithosphere of continental origin that was last affected by thermotectonic processes in the Cretaceous to early Cenozoic. Variability within the data likely arises from differences in radiogenic heat production within the continental crust and overlying sediments. This can be further explored by comparing the data with geophysical constraints on sediment and crustal thicknesses.

  1. Rates, Mechanisms, and Implications of Crustal Assimilation in Continental Arcs

    NASA Astrophysics Data System (ADS)

    Dungan, M.; Davidson, J.

    2002-12-01

    Contrary to the limiting constraints postulated by Bowen for the coupled thermal and mass balance implicated in assimilation, many studies [1-6] suggest that multi-stage and multi-component assimilation, abetted by magma mixing, may be volumetrically important and have profound consequences for the chemistry of basaltic and evolved magmas in long-lived continental magmatic systems. The probability of a primitive or evolved basalt arriving at the Earth's surface having undergone perfectly closed-system evolution during passage through 25-60 km of continental crust is vanishingly low. A case-by-case demonstration that the intra-crustal chemical overprint is trivial, or that it can be quantified and subtracted, is an essential step in any evaluation of mantle source-region chemistry and processes based on inversion of continental basalt compositions. In magmatic systems characterized by mafic magma recharge the thermal energy and physical dynamism needed for assimilation are not constrained to come uniquely from one magma batch [7, 8]. Equally important is that assimilation is rarely equivalent to bulk melting of ingested blocks followed by reservoir-wide homogenization. The mechanics of crustal assimilation are governed by grain boundary melting, disaggregation, and dispersal of refractory solids (including xenocryst settling) wherein liberated low-density, incompatible element-enriched partial melts have the capacity to render primitive arc magma batches variably modified, as well as heterogeneous on short length-scales. Evidence that basalts thermally erode surface channels and conduit walls, and new observations constraining the maximum time that some extensively melted xenoliths have resided in their host magmas, indicate that the time required to impose an open-system overprint on a hot basaltic magma (days to yrs) is far shorter than typical repose periods at most arc volcanoes (50-500 yrs). Assimilative recycling of broadly gabbroic arc cumulates has had large

  2. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  3. Discriminatory Proofreading Regimes in Nonequilibrium Systems

    NASA Astrophysics Data System (ADS)

    Murugan, Arvind; Huse, David A.; Leibler, Stanislas

    2014-04-01

    We use ideas from kinetic proofreading, an error-correcting mechanism in biology, to identify new kinetic regimes in nonequilibrium systems. These regimes are defined by the sensitivity of the occupancy of a state of the system to a change in its energy. In biological contexts, higher sensitivity corresponds to stronger discrimination between molecular substrates with different energetics competing in the same reaction. We study this discriminatory ability in systems with discrete states that are connected by a general network of transitions. We find multiple regimes of different discriminatory ability when the energy of a given state of the network is varied. Interestingly, the occupancy of the state can even increase with its energy, corresponding to an "antiproofreading" regime. The number and properties of such discriminatory regimes are limited by the topology of the network. Finally, we find that discriminatory regimes can be changed without modifying any "hard-wired" structural aspects of the system but rather by simply changing external chemical potentials.

  4. Regimes of suprathermal electron transport

    SciTech Connect

    Glinsky, M.E.

    1995-07-01

    Regimes of the one-dimensional (1-D) transport of suprathermal electrons into a cold background plasma are delineated. A well ordered temporal progression is found through eras where {ital J}{center_dot}{ital E} heating, hot electron--cold electron collisional heating, and diffusive heat flow dominate the cold electron energy equation. Scaling relations for how important quantities such as the width and temperature of the heated layer of cold electrons evolve with time are presented. These scaling relations are extracted from a simple 1-D model of the transport which can be written in dimensionless form with one free parameter. The parameter is shown to be the suprathermal electron velocity divided by the drift velocity of cold electrons which balances the suprathermal current. Special attention is paid to the assumptions which allow the reduction from the collisional Vlasov equation, using a Fokker--Planck collision operator, to this simple model. These model equations are numerically solved and compared to both the scaling relations and a more complete multigroup electron diffusion transport. Implications of the scaling relations on fast ion generation, magnetic field generation, and electric field inhibition of electron transport are examined as they apply to laser heated plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  5. Multistability of synchronous regimes in rotator ensembles.

    PubMed

    Kryukov, A K; Petrov, V S; Osipov, G V; Kurths, J

    2015-12-01

    We study collective dynamics in rotator ensembles and focus on the multistability of synchronous regimes in a chain of coupled rotators. We provide a detailed analysis of the number of coexisting regimes and estimate in particular, the synchronization boundary for different types of individual frequency distribution. The number of wave-based regimes coexisting for the same parameters and its dependence on the chain length are estimated. We give an analytical estimation for the synchronization frequency of the in-phase regime for a uniform individual frequency distribution. PMID:26723160

  6. Assessing sufficiency of thermal riverscapes for resilient salmon and steelhead populations

    EPA Science Inventory

    Resilient salmon populations require river networks that provide water temperature regimes sufficient to support a diversity of salmonid life histories across space and time. Efforts to protect, enhance and restore watershed thermal regimes for salmon may target specific location...

  7. Continental and oceanic crustal magnetization modelling

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.; Hayling, K. L.

    1984-01-01

    Inversion of magnetic data from the MAGSAT satellite, to arrive at intensities of magnetization of the Earth's crust, was performed by two different methods. The first method uses a spherical harmonic model of the magnetic field. The coefficients believed to represent sources in the Earth's crust can then be inverted to arrive at vertical dipole moments per unit area at the Earth's surface. The spherical harmonic models contain coefficients of degrees of harmonics up to 23. The dipole moment per unit area for a surface element can then be determined by summing the contribution for each individual degree of harmonic. The magnetic moments were calculated for continental and oceanic areas separately as well as over certain latitudinal segments. Of primary concern was to determine whether there are any differences between continental and oceanic areas. The second analysis with magnetization intensities was made using narrower ranges of degrees of harmonics, assuming that higher degrees are present in the core field signal.

  8. Continental crustal composition and lower crustal models

    NASA Technical Reports Server (NTRS)

    Taylor, S. R.

    1983-01-01

    The composition of the upper crust is well established as being close to that of granodiorite. The upper crustal composition is reflected in the uniform REE abundances in shales which represent an homogenization of the various REE patterns. This composition can only persist to depths of 10-15 km, for heat flow and geochemical balance reasons. The composition of the total crust is model dependent. One constraint is that it should be capable of generating the upper granodioritic (S.L.) crust by partial melting within the crust. This composition is based on the andesite model, which assumes that the total crust has grown by accretion of island arc material. A representation of the growth rate of the continental crust is shown. The composition of the lower crust, which comprises 60-80% of the continental crust, remains a major unknown factor for models of terrestrial crustal evolution. Two approaches are used to model the lower crust.

  9. Regional magnetic anomaly constraints on continental rifting

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  10. North Atlantic Margins: Case studies of Magmatic Continental Breakup

    NASA Astrophysics Data System (ADS)

    Eccles, J. D.; White, R. S.; Christie, P. A. F.

    2012-04-01

    Continental breakup between Europe and Greenland was accompanied by the rapid eruption of the > 1 million cubic kilometres of extruded basalts forming North Atlantic Igneous Province. With episodes of extension in the region dating back to the Devonian, rifting finally proceeded to full breakup and oceanic spreading in the Paleocene. Flood basalt units flowed up to 150 km over pre-existing sedimentary basins, discrete volcanic centres formed and intrusion into the thinned continental crust occurred. Marine seismic investigations utilising industry-leading seismic reflection imaging technologies and large deployments of ocean bottom seismometers across the Faroes and Hatton Bank margins have been used to better resolve margin structure and composition, improving our understanding of breakup processes. Seismic reflection imaging reveals sub-aerial and submarine seaward-dipping reflector sequences tracking the interplay of uplift (transient and permanent), crustal loading through extrusion and ongoing extension. Lower crustal reflectors, cross-cutting the continental fabric and interpreted as intrusions, are observed within the narrow continent-ocean transition. P-wave tomography of wide-angle reflections and refractions, recorded to offsets of up to ~200 km, reveals unusually thick oceanic crust with lower crustal velocities in excess of those expected for MORB compositions. High P-wave velocities are attributed to magnesium-rich compositions which, combined with the large oceanic crustal thickness, would be consistent with an elevated mantle temperature (~150°C higher than 'normal') at the time of breakup. Vp/Vs ratios derived from tomography of converted shear wave phases also support high magnesium melt composition. P-wave velocities and Vp/Vs ratios across the continent-ocean transition show a mixing trend between magnesium-rich gabbroic compositions (100% for oceanic crust) and compositions consistent with the Lewisian gneiss basement or Early Proterozoic

  11. Iceberg scouring on the Norwegian continental shelf

    SciTech Connect

    Lien, R.

    1983-05-01

    This paper is a condensed version of parts of a Dr. ing. thesis to be presented during 1983. The first part of the paper deals with the regional distribution of iceberg scouring on the Norwegian continental shelf, and some general aspects related to it. The second part deals with iceberg scouring as a local phenomenon and its relation to the sea floor topography, sediment distribution, and geological and geotechnical properties of the sediments.

  12. Ocean processes at the Antarctic continental slope.

    PubMed

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  13. Ocean processes at the Antarctic continental slope.

    PubMed

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

  14. Precipitation of Continental Origin over South America

    NASA Astrophysics Data System (ADS)

    Martinez-Agudelo, J. A.; Dominguez, F.

    2012-12-01

    The Amazon forest receives high amounts of moisture from the tropical Atlantic. A significant part of this moisture is returned back to the atmosphere by the forest, and further redistributed to the rest of the continent by the meridional flow imposed by the Andes. Thus, the land-atmosphere interaction between the Amazon forest and the large-scale flow affects not only the forest itself but also the downstream regions. We develop a method to quantify the precipitation of continental origin over South America, and identify the contribution that selected source regions make to continental precipitation. The average annual cycle of precipitation of continental origin for the five-year period 2000-2004 shows a band of high values aligned along the northwest-southeast direction, from southern Peru to northeastern Argentina. The lowest values of precipitation of continental origin occur upstream, over the northeastern coast of South America. Precipitation that originates as moisture from the Amazon forest shows maximum values over the western side of the Amazon, east of the Andes, especially over southern Peru. The Amazon forest also contributes to precipitation over La Plata River Basin (LPRB) and the Pacific coast of Colombia. During its dry season, up to 29.3% of the precipitation over LPRB originates as moisture from the Amazon forest. Throughout the year, the contributions to precipitation over LPRB by the Amazon forest and LPRB (recycled precipitation) are in the same range, but out of phase. The average contribution of the rest of the continent to precipitation over LPRB is smaller but of the same order as that of the Amazon and LPRB.

  15. Workshop on the Growth of Continental Crust

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D. (Editor)

    1988-01-01

    Constraints and observations were discussed on a fundamental unsolved problem of global scale relating to the growth of planetary crusts. All of the terrestrial planets were considered, but emphasis was placed on the Earth's continental crust. The title of each session is: (1) Extraterrestrial crustal growth and destruction; (2) Constraints for observations and measurements of terrestrial rocks; (3) Models of crustal growth and destruction; and (4) Process of crustal growth and destruction.

  16. Continental sources of halocarbons and nitrous oxide

    NASA Technical Reports Server (NTRS)

    Prather, M. J.

    1985-01-01

    Estimates of continental sources of CFC-11, CFC-12, CCl4, CH3CCl3 and N2O are derived from the atmospheric lifetime experiment in Adrigole, Ireland, and anthropogenic emissions of CCl4 and N2O from Europe have been identified. Relative source strengths are consistent with global budgets for the halocarbons and N2O. Different industrial release patterns for halocarbons are observed for Europe, the western United States and Australia.

  17. Landscape modelling at Regional to Continental scales

    NASA Astrophysics Data System (ADS)

    Kirkby, M. J.

    Most work on simulating landscape evolution has been focused at scales of about 1 Ha, there are still limitations, particularly in understanding the links between hillslope process rates and climate, soils and channel initiation. However, the need for integration with GCM outputs and with Continental Geosystems now imposes an urgent need for scaling up to Regional and Continental scales. This is reinforced by a need to incorporate estimates of soil erosion and desertification rates into national and supra-national policy. Relevant time-scales range from decadal to geological. Approaches at these regional to continental scales are critical to a fuller collaboration between geomorphologists and others interested in Continental Geosystems. Two approaches to the problem of scaling up are presented here for discussion. The first (MEDRUSH) is to embed representative hillslope flow strips into sub-catchments within a larger catchment of up to 5,000 km2. The second is to link one-dimensional models of SVAT type within DEMs at up to global scales (CSEP/SEDWEB). The MEDRUSH model is being developed as part of the EU Desertification Programme (MEDALUS project), primarily for semi-natural vegetation in southern Europe over time spans of up to 100 years. Catchments of up to 2500 km2 are divided into 50-200 sub-catchments on the basis of flow paths derived from DEMs with a horizontal resolution of 50 m or better. Within each sub-catchment a representative flow strip is selected and Hydrology, Sediment Transport and Vegetation change are simulated in detail for the flow strip, using a 1 hour time step. Changes within each flow strip are transferred back to the appropriate sub-catchment and flows of water and sediment are then routed through the channel network, generating changes in flood plain morphology.

  18. Cyclic growth in Atlantic region continental crust

    NASA Technical Reports Server (NTRS)

    Goodwin, A. M.

    1986-01-01

    Atlantic region continental crust evolved in successive stages under the influence of regular, approximately 400 Ma-long tectonic cycles. Data point to a variety of operative tectonic processes ranging from widespread ocean floor consumption (Wilson cycle) to entirely ensialic (Ampferer-style subduction or simple crustal attenuation-compression). Different processes may have operated concurrently in some or different belts. Resolving this remains the major challenge.

  19. Ocean processes at the Antarctic continental slope

    PubMed Central

    Heywood, Karen J.; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D.; Queste, Bastien Y.; Stevens, David P.; Wadley, Martin; Thompson, Andrew F.; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K.; Smith, Walker

    2014-01-01

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean–atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

  20. Abrupt plate accelerations shape rifted continental margins

    NASA Astrophysics Data System (ADS)

    Brune, Sascha; Williams, Simon E.; Butterworth, Nathaniel P.; Müller, R. Dietmar

    2016-08-01

    Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth’s major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength–velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.

  1. Abrupt plate accelerations shape rifted continental margins.

    PubMed

    Brune, Sascha; Williams, Simon E; Butterworth, Nathaniel P; Müller, R Dietmar

    2016-08-11

    Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth's major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength--velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time.

  2. Modelled and observed continental surface heat fluxes

    NASA Astrophysics Data System (ADS)

    Beltrami, H.; MacDougall, A. H.; Gonzalez-Rouco, F. J.; Stevens, M. B.; Bourlon, E.

    2009-12-01

    Heat fluxes in the continental subsurface were estimated from general circulation model (GCM) simulations of the climate of the last millennium and compared to those obtained from subsurface geothermal data. Since GCMs have bottom boundary conditions (BBCs) that are less than 10 m deep and thus may be thermodynamically restricted in the continental subsurface, we used an idealized land surface model (LSM) with a very deep BBC to estimate the potential for realistic subsurface heat storage in the absence of bottom boundary constraints. Results indicate that there is good agreement between observed fluxes and GCM simulated fluxes for the 1780-1980 period when the GCM simulated temperatures are coupled to the LMS with deep BBC. These results emphasize the importance of placing a deep BBC in GCM soil components for the proper simulation of the overall continental heat budget. In addition, the agreement between the LSM surface fluxes and the borehole temperature reconstructed fluxes lends additional support to the overall quality of the GCM (ECHO-G) paleoclimatic simulations. Simulations to 2100 show a divergence between the LSM simulated subsurface heat content and the heat gain in the ECHO-G soil model, with the placement of the BBCs surpassing the thermodynamical effect of the choice of emission scenario as the most important factor determining heat absorption in the simulated subsurface.

  3. Continental Deformation in Madagascar from GNSS Observations

    NASA Astrophysics Data System (ADS)

    Stamps, D. S.; Rajaonarison, T.; Rambolamanana, G.; Herimitsinjo, N.; Carrillo, R.; Jesmok, G.

    2015-12-01

    D.S. Stamps, T. Rajaonarison, G. Rambolamanana Madagascar is the easternmost continental segment of the East African Rift System (EARS). Plate reconstructions assume the continental island behaves as a rigid block, but studies of geologically recent kinematics suggest Madagascar undergoes extension related to the broader EARS. In this work we test for rigidity of Madagascar in two steps. First, we quantify surface motions using a novel dataset of episodic and continuous GNSS observations that span Madagascar from north to south. We established a countrywide network of precision benchmarks fixed in bedrock and with open skyview in 2010 that we measured for 48-72 hours with dual frequency receivers. The benchmarks were remeasured in 2012 and 2014. We processed the episodic GNSS data with ABPO, the only continuous GNSS station in Madagascar with >2.5 years of data, for millimeter precision positions and velocities at 7 locations using GAMIT-GLOBK. Our velocity field shows 2 mm/yr of differential motion between southern and northern Madagascar. Second, we test a suite of kinematic predictions from previous studies and find residual velocities are greater than 95% uncertainties. We also calculate angular velocity vectors assuming Madagascar moves with the Lwandle plate or the Somalian plate. Our new velocity field in Madagascar is inconsistent with all models that assume plate rigidity at the 95% uncertainty level; this result indicates the continental island undergoes statistically significant internal deformation.

  4. Abrupt plate accelerations shape rifted continental margins.

    PubMed

    Brune, Sascha; Williams, Simon E; Butterworth, Nathaniel P; Müller, R Dietmar

    2016-08-11

    Rifted margins are formed by persistent stretching of continental lithosphere until breakup is achieved. It is well known that strain-rate-dependent processes control rift evolution, yet quantified extension histories of Earth's major passive margins have become available only recently. Here we investigate rift kinematics globally by applying a new geotectonic analysis technique to revised global plate reconstructions. We find that rifted margins feature an initial, slow rift phase (less than ten millimetres per year, full rate) and that an abrupt increase of plate divergence introduces a fast rift phase. Plate acceleration takes place before continental rupture and considerable margin area is created during each phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. The extension models suggest that the two-phase velocity behaviour is caused by a rift-intrinsic strength--velocity feedback, which can be robustly inferred for diverse lithosphere configurations and rheologies. Our results explain differences between proximal and distal margin areas and demonstrate that abrupt plate acceleration during continental rifting is controlled by the nonlinear decay of the resistive rift strength force. This mechanism provides an explanation for several previously unexplained rapid absolute plate motion changes, offering new insights into the balance of plate driving forces through time. PMID:27437571

  5. The geochemical and temporal evolution of the continental lithosphere and its relationship to continental-scale faulting: The Karakoram Fault, eastern Karakoram, NW Himalayas

    NASA Astrophysics Data System (ADS)

    Phillips, Richard J.; Searle, Michael P.; Parrish, Randall R.

    2013-03-01

    New laser ablation multicollector-inductively coupled plasma-mass spectrometry and isotope dilution-thermal ionization mass spectrometry U-Pb ages, coupled with Sm-Nd isotope and geochemical analysis, define the temporal and geochemical evolution of the continental lithosphere in the eastern Karakoram, India, NW Himalaya. Our analysis demonstrates that magmatism occurred between ~108 and 69 Ma and ~22 and 13 Ma. The new age data, coupled with geochemical examination of the granitoids, confirm a parallel evolution with the western Karakoram in Pakistan and supports a model of regional continental crustal thickening and related metamorphism. Middle to Late Cretaceous magmatism immediately adjacent to the Karakoram fault suggests that crustal melting and associated metamorphism are unrelated to shearing along the fault. Miocene leucogranite magmatism occurred almost exactly concomitant with the emplacement of the Baltoro batholith in Pakistan. These trans-Karakoram leucogranites also display similar geochemical evolution trends. Our new data clearly link the leucogranites along the fault to the regional Baltoro batholith and related metamorphic complexes to the west. This supports previous work suggesting that magmatism and metamorphism were not syn-kinematic with continental-scale faulting. The data demonstrate that the Karakoram fault could not have accommodated lateral offset in this region prior to ~16 Ma, limiting the long-term averaged slip rate to a maximum of ~10 mm/yr.

  6. Atmospheric Residence Times of Continental Aerosols.

    NASA Astrophysics Data System (ADS)

    Balkanski, Yves Jacques

    The global atmospheric distributions of ^{222}Rn and ^{210 }Pb are simulated with a three-dimensional model of atmospheric transport based on the meteorology of the NASA GISS^1>=neral circulation model. The short-lived radioactive gas ^ {222}Rn (half-life = 3.8d) is emitted almost exclusively from land, at a relatively uniform rate; hence it is an excellent tracer of continental influences. Lead -210 is produced by decay of ^{222} Rn and immediately condenses to preexisting aerosol surfaces. It provides an excellent measure of aerosol residence times in the atmosphere because its source is accurately defined by the ^{222} Rn distribution. Results from the three-dimensional model are compared to measurements of ^ {222}Rn and ^{210 }Pb atmospheric concentrations to evaluate model's long-range transport over oceanic regions and to study the deposition mechanisms of atmospheric aerosols. Model results for ^{222} Rn are used to examine the long-range transport of continental air over two selected oceanic regions, the subantartic Indian Ocean and the North Pacific. It is shown that fast transport of air from southern Africa causes substantial continental pollution at southern mid-latitudes, a region usually regarded as pristine. Air over the North Pacific is heavily impacted by continental influences year round, but the altitude at which the transport occurs varies seasonally. Observations of aerosols at island sites, which are commonly used as diagnostics of continental influences, may be misleading because they do not account for influences at high altitude and because aerosols are efficiently scavenged by deposition during transport. The study of ^{210}Pb focuses on defining the residence times of submicron aerosols in the troposphere. Scavenging in wet convective updrafts is found to provide the dominant sink on a global scale. The globally averaged residence time for ^{210 }Pb-containing aerosols in the troposphere is 7 days. The average increase in residence time

  7. Basins in ARC-continental collisions

    USGS Publications Warehouse

    Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

    2012-01-01

    Arc-continent collisions occur commonly in the plate-tectonic cycle and result in rapidly formed and rapidly collapsing orogens, often spanning just 5-15 My. Growth of continental masses through arc-continent collision is widely thought to be a major process governing the structural and geochemical evolution of the continental crust over geologic time. Collisions of intra-oceanic arcs with passive continental margins (a situation in which the arc, on the upper plate, faces the continent) involve a substantially different geometry than collisions of intra-oceanic arcs with active continental margins (a situation requiring more than one convergence zone and in which the arc, on the lower plate, backs into the continent), with variable preservation potential for basins in each case. Substantial differences also occur between trench and forearc evolution in tectonically erosive versus tectonically accreting margins, both before and after collision. We examine the evolution of trenches, trench-slope basins, forearc basins, intra-arc basins, and backarc basins during arc-continent collision. The preservation potential of trench-slope basins is low; in collision they are rapidly uplifted and eroded, and at erosive margins they are progressively destroyed by subduction erosion. Post-collisional preservation of trench sediment and trench-slope basins is biased toward margins that were tectonically accreting for a substantial length of time before collision. Forearc basins in erosive margins are usually floored by strong lithosphere and may survive collision with a passive margin, sometimes continuing sedimentation throughout collision and orogeny. The low flexural rigidity of intra-arc basins makes them deep and, if preserved, potentially long records of arc and collisional tectonism. Backarc basins, in contrast, are typically subducted and their sediment either lost or preserved only as fragments in melange sequences. A substantial proportion of the sediment derived from

  8. Flow regimes and heat transfer in vertical narrow annuli

    SciTech Connect

    Ulke, A.; Goldberg, I.

    1993-11-01

    In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ``isolated`` bubbles, ``coalesced`` bubbles and liquid deficient regions have been defined.

  9. On the Evolution of Glaciated Continental Margins

    NASA Astrophysics Data System (ADS)

    Sverre Laberg, Jan; Rydningen, Tom Arne; Safronova, Polina A.; Forwick, Matthias

    2016-04-01

    Glaciated continental margins, continental margins where a grounded ice sheet repeatedly has been at or near the shelf break, are found at both northern and southern high-latitudes. Their evolution are in several aspects different from their low-latitude counterparts where eustatic sea-level variations possess a fundamental control on their evolution and where fluvial systems provide the main sediment input. From studies of the Norwegian - Barents Sea - Svalbard and NE Greenland continental margins we propose the following factors as the main control on the evolution of glaciated continental margins: 1) Pre-glacial relief controlling the accommodation space, 2) Ice sheet glaciology including the location of fast-flowing ice streams where source area morphology exerts a fundamental control, 3) Composition of the glacigenic sediments where the clay content in previous studies have been found to be important, and 4) Sea-level controlled both by eustacy and isostacy. From three case studies, 1) the western Barents Sea, 2) part of the North Norwegian (Troms), and 3) the Mid-Norwegian margin, the influence on these factors for the sea-floor morphology, sedimentary processes of the continental slope - deep sea and continental margin architecture are discussed. The pre-glacial relief of the mid-Norwegian and Troms margins relates to the onset of rifting and plate break-up from the early Cenozoic while for the SW Barents Sea, plate shear was followed by rifting. A wide zone of extended continental crust occurs offshore mid-Norway while this zone is much narrower offshore Troms leading to a more pronounced pre-glacial relief. Regarding sediment delivery and ice sheet glaciology the western Barents Sea exemplifies very high sediment input corresponding to an estimated average erosion of the source area of ~0.4 mm/yr (SW Barents Sea), much of which is related to subglacial erosion of Mesozoic - Cenozoic sedimentary rocks from large paleo-ice streams. The mid-Norwegian margin

  10. Reconstructing Rodinia by Fitting Neoproterozoic Continental Margins

    USGS Publications Warehouse

    Stewart, John H.

    2009-01-01

    Reconstructions of Phanerozoic tectonic plates can be closely constrained by lithologic correlations across conjugate margins by paleontologic information, by correlation of orogenic belts, by paleomagnetic location of continents, and by ocean floor magmatic stripes. In contrast, Proterozoic reconstructions are hindered by the lack of some of these tools or the lack of their precision. To overcome some of these difficulties, this report focuses on a different method of reconstruction, namely the use of the shape of continents to assemble the supercontinent of Rodinia, much like a jigsaw puzzle. Compared to the vast amount of information available for Phanerozoic systems, such a limited approach for Proterozoic rocks, may seem suspect. However, using the assembly of the southern continents (South America, Africa, India, Arabia, Antarctica, and Australia) as an example, a very tight fit of the continents is apparent and illustrates the power of the jigsaw puzzle method. This report focuses on Neoproterozoic rocks, which are shown on two new detailed geologic maps that constitute the backbone of the study. The report also describes the Neoproterozoic, but younger or older rocks are not discussed or not discussed in detail. The Neoproterozoic continents and continental margins are identified based on the distribution of continental-margin sedimentary and magmatic rocks that define the break-up margins of Rodinia. These Neoproterozoic continental exposures, as well as critical Neo- and Meso-Neoproterozoic tectonic features shown on the two new map compilations, are used to reconstruct the Mesoproterozoic supercontinent of Rodinia. This approach differs from the common approach of using fold belts to define structural features deemed important in the Rodinian reconstruction. Fold belts are difficult to date, and many are significantly younger than the time frame considered here (1,200 to 850 Ma). Identifying Neoproterozoic continental margins, which are primarily

  11. Regimes of DNA confined in a nanochannel

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Doyle, Patrick

    2014-03-01

    Scaling regimes for polymers confined to tubular channels are well established when the channel cross-sectional dimension is either very small (Odjik regime) or large (classic de Gennes regime) relative to the polymer Kuhn length. In the literature, there is no clear consensus regarding the intermediate region and if subregimes even exist to connect these two classic bounding regimes. The confluence of emerging single DNA mapping technologies and a resurged interest in the fundamental properties of confined polymers has led to extensive research in this area using DNA as a model system. Due to the DNA molecule's properties and limitations of nanofabrication, most experiments are performed in this intermediate regime with channel dimensions of a few Kuhn lengths. Here we use simulations and theory to reconcile conflicting theories and show that there are indeed extended de Gennes, partial alignment and hairpin regimes located between the two classic regimes. Simulations results for both chain extension and free energy support the existence of these regimes. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (CBET-1335938).

  12. FISHER INFORMATION AND ECOSYSTEM REGIME CHANGES

    EPA Science Inventory

    Following Fisher’s work, we propose two different expressions for the Fisher Information along with Shannon Information as a means of detecting and assessing shifts between alternative ecosystem regimes. Regime shifts are a consequence of bifurcations in the dynamics of an ecosys...

  13. Capacitance densitometer for flow regime identification

    DOEpatents

    Shipp, Jr., Roy L.

    1978-01-01

    This invention relates to a capacitance densitometer for determining the flow regime of a two-phase flow system. A two-element capacitance densitometer is used in conjunction with a conventional single-beam gamma densitometer to unambiguously identify the prevailing flow regime and the average density of a flowing fluid.

  14. Arctic and Antarctic submarine gullies—A comparison of high latitude continental margins

    NASA Astrophysics Data System (ADS)

    Gales, J. A.; Forwick, M.; Laberg, J. S.; Vorren, T. O.; Larter, R. D.; Graham, A. G. C.; Baeten, N. J.; Amundsen, H. B.

    2013-11-01

    Submarine gullies are common features of high latitude continental slopes and, over the last decade, have been shown to play a key role in continental margin evolution, submarine erosion, downslope sediment transport, slope deposits, and the architecture of petroleum reservoirs. However, the processes that form these gullies, the timescales over which they develop, and the environmental controls influencing their morphology remain poorly constrained. We present the first systematic and comparative analysis between Arctic and Antarctic gullies with the aim of identifying differences in slope character, from which we infer differences in processes operating in these environments. Quantitative analysis of multibeam echosounder data along 2441 km of the continental shelf and upper slope and morphometric signatures of over 1450 gullies show that six geomorphically distinct gully types exist on high latitude continental margins. We identify distinct differences between Arctic and Antarctic gully morphologies. In the Arctic data sets, deep relief (> 30 m gully incision depth at 50 m below the shelf edge) and shelf-incising gullies are lacking. These differences have implications for the timescales over which the gullies were formed and for the magnitude of the flows that formed them. We consider two hypotheses for these differences: (1) some Antarctic gullies developed through several glacial cycles; and (2) larger Antarctic gullies were formed since the Last Glacial Maximum as a result of erosive flows (i.e., sediment-laden subglacial meltwater) being more abundant on parts of the Antarctic margin over longer timescales. A second difference is that unique gully signatures are observed on Arctic and on Antarctic margins. Environmental controls, such as the oceanographic regime and geotechnical differences, may lead to particular styles of gully erosion observed on Arctic and Antarctic margins.

  15. The impact of U.S. continental outflow on ozone and aerosol distributions over the western Atlantic

    SciTech Connect

    Anderson, B.E.; Gregory, G.L.; Barrick, J.D.W.; Collins, J.E. Jr.; Sachse, G.W.; Bagwell, D.; Shipham, M.C.; Bradshaw, J.D.; Sandholm, S.T. ||

    1993-12-01

    Aircraft measurements of selected trace gas species, aerosols, and meteorological parameters were performed in the lower troposphere off the U.S. east coast during August and September 1989 as part of the NASA Global Tropospheric Experiment (GTE) Chemical Instrumentation Test and Evaluation (CITE 3) expedition. In this paper, we examine these data to assess the impact of continental outflow on western Atlantic O3 and small aerosol budgets. Results show that mixed layer (ML) O3 concentrations and small aerosol number densities (Np) were enhanced by factors of 3 and 6, respectively, within air masses of predominantly continental origin compared with clean maritime background air. These enhancements exhibited a marked altitude dependence, declining rapidly above the ML to the point where only slight to moderate differences in O3 and Np, respectively, were notable above 2.4 km. Within continentally influenced ML`s, both O3 and Np were correlated with CO, exhibiting linear regression slopes averaging 0.4 ppbv (O3)/ppbv(CO) for O3 and 7.7 (particles/cc)/ppbv(CO) for Np and indicating a primarily anthropogenic origin for the observed enhancement of these species. Comparisons between profiles in continental and background maritime air masses suggest that photochemical production below 1.4-km altitude adds over 10% to western Atlantic tropospheric column O3 abundance in continental outflow regimes. For aerosols, eastward advection of low-level continental air contributes an average net flux of 2.8 metric tons of submicron (accumulation mode) particles per kilometer of shoreline per day to the western Atlantic troposphere.

  16. The impact of U.S. continental outflow on ozone and aerosol distributions over the western Atlantic

    NASA Technical Reports Server (NTRS)

    Anderson, B. E.; Gregory, G. L.; Barrick, J. D. W.; Collins, J. E., Jr.; Sachse, G. W.; Bagwell, D.; Shipham, M. C.; Bradshaw, J. D.; Sandholm, S. T.

    1993-01-01

    Aircraft measurements of selected trace gas species, aerosols, and meteorological parameters were performed in the lower troposphere off the U.S. east coast during August and September 1989 as part of the NASA Global Tropospheric Experiment (GTE) Chemical Instrumentation Test and Evaluation (CITE 3) expedition. In this paper, we examine these data to assess the impact of continental outflow on western Atlantic O3 and small aerosol budgets. Results show that mixed layer (ML) O3 concentrations and small aerosol number densities (Np) were enhanced by factors of 3 and 6, respectively, within air masses of predominantly continental origin compared with clean maritime background air. These enhancements exhibited a marked altitude dependence, declining rapidly above the ML to the point where only slight to moderate differences in O3 and Np, respectively, were notable above 2.4 km. Within continentally influenced ML's, both O3 and Np were correlated with CO, exhibiting linear regression slopes averaging 0.4 ppbv (O3)/ppbv(CO) for O3 and 7.7 (particles/cc)/ppbv(CO) for Np and indicating a primarily anthropogenic origin for the observed enhancement of these species. Comparisons between profiles in continental and background maritime air masses suggest that photochemical production below 1.4-km altitude adds over 10% to western Atlantic tropospheric column O3 abundance in continental outflow regimes. For aerosols, eastward advection of low-level continental air contributes an average net flux of 2.8 metric tons of submicron (accumulation mode) particles per kilometer of shoreline per day to the western Atlantic troposphere.

  17. Warm inflation dynamics in the low temperature regime

    SciTech Connect

    Bastero-Gil, Mar; Berera, Arjun

    2007-08-15

    Warm inflation scenarios are studied with the dissipative coefficient computed in the equilibrium approximation. Use is made of the analytical expressions available in the low temperature regime with focus on the possibility of achieving strong dissipation within this approximation. Two different types of models are examined: monomial or equivalently chaotic type potentials, and hybrid like models where the energy density during inflation is dominated by the false vacuum. In both cases dissipation is shown to typically increase during inflation and bring the system into the strong dissipative regime. Observational consequences are explored for the amplitude of the primordial spectrum and the spectral index, which translate into constraints on the number of fields mediating the dissipative mechanism, and the number of light degrees of freedom produced during inflation. This paper furthers the foundational development of warm inflation dynamics from first principles quantum field theory by calculating conservative lower bound estimates on dissipative effects during inflation using the well established thermal equilibrium approximation. This approximation does not completely represent the actual physical system and earlier work has shown relaxing both the equilibrium and low temperature constraints can substantially enlarge the warm inflation regime, but these improvements still need further theoretical development.

  18. Discrete fluorescent saturation regimes in multilevel systems

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Bhatia, A. K.

    1988-01-01

    Using models of multilevel atoms, the fluorescent process was examined for the ratio of the photooxidation rate, Pij, to the collisional oxidation rate, Cij, in the pumped resonance transition i-j. It is shown that, in the full range of the parameter Pij/Cij, there exist three distinct regimes (I, II, and III) which may be usefully exploited. These regimes are defined, respectively, by the following conditions: Pij/Cij smaller than about 1; Pij/Cij much greater than 1 and Pij much lower than Cki; and Pij/Cij much greater than 1 and Pij much higher than Cki, where Cki is the collisional rate populating the source level i. The only regime which is characterized by the sensitivity of fluorescent-fluorescent line intensity ratios to Pij is regime I. If regime III is reached, even fluorescent-nonfluorescent line ratios become independent of Pij. The analysis is applied to the resonant photoexcitation of a carbonlike ion.

  19. Origin of Enriched Geochemical Signatures in Continental Arc Rocks by Antithetic Subduction of Continental Lithosphere

    NASA Astrophysics Data System (ADS)

    Glazner, A. F.; Brandon, M. T.

    2002-12-01

    The source materials for magmas in continental arcs are not well known. Magmas are typically assumed to be derived from the subducted slab, subducted sediment, and mantle wedge, but some continental arcs have isotopic signatures that are inconsistent with these sources. For example, a large volume of the Sierra Nevada batholith consists of rocks that have initial Sr ratios of about 0.706-0.708 and ɛNd values ranging from -3 to -8. Late Cenozoic volcanic rocks erupted through the batholith, and their entrained xenoliths, have similar isotopic compositions. These characteristics are inconsistent with derivation from only the sources above and are most easily explained by derivation from enriched continental lithospheric mantle. However, there was never enough lithospheric mantle under the arc to produce the observed volume of enriched arc rocks; mass balance fails by one or two orders of magnitude, and lithosphere cannot flow by viscous processes to provide material to the arc. A possible solution to this problem lies in kinematic mass balance of the arc system. In many continental arcs (e.g., Cenozoic Andes, Mesozoic northern Cordillera and Sierra Nevada), thrust faults have carried the arc at least 100-200 km toward the craton. This motion requires moving a comparable amount of sub-detachment lower crust and mantle toward the arc and produces a tremendous cross-sectional balance problem. Geologic field studies and geodynamic modeling indicate that this antithetic subduction feeds continental lithosphere into the convecting mantle wedge where it can contribute to magma genesis. This process provides a large volume of enriched and probably fertile continental lithospheric mantle to the arc system and may account for the unusual geochemical signatures of some arc rocks.

  20. H2O-fluid-saturated melting of subducted continental crust facilitates exhumation of ultrahigh-pressure rocks in continental subduction zones

    NASA Astrophysics Data System (ADS)

    Labrousse, L.; Duretz, T.; Gerya, T.

    2015-10-01

    We present two-dimensional numerical models of plate subduction and collision inspired by the Scandinavian Caledonian orogeny to investigate the possible impact of continental crust partial melting on the exhumation of ultra-high pressure metamorphic rocks. Three possible reactions were tested: low temperature solidus representing H2O-fluid-saturated partial melting, and two end-member reaction curves for dehydration melting. Thermo-mechanical effects of partial melting were implemented as (1) a viscosity decrease as a determined rheologically critical melt percentage was reached (here 0.1), (2) a change in effective heat capacity and adiabatic heating/cooling accounting for a latent heat term in the heat equation. Among the 3 tested reactions, only H2O-fluid-saturated partial melting drastically modifies the collision dynamics from the non-melting reference model holding all other parameters constant. A substantially low general viscosity truncation (here 1017 Pa s) is needed to properly resolve the effect of partial melting on deep collision processes. Low temperature melting indeed induces the development of a low viscosity buoyant plume prior to slab detachment, where migmatites exhume from UHP conditions at rates and with pressure-temperature paths similar to the natural values acknowledged for the Norwegian Caledonides. High temperature melting has no drastic influence on early collision dynamics. While positive buoyancy remains the first order driver for the exhumation of buried continental rocks, exhumation initiates in these cases with eduction subsequent to slab detachment. Melting and formation of a migmatite plume can later occur along decompression path while continental crust undergoes thermal reequilibration at temperatures above 900 °C. Some of the partially molten material can also relaminate in the overriding plate rather than exhume within the collision zone. Even if minor in terms of amount of magma produced, H2O-fluid-saturated partial melting

  1. Anomalous Subsidence at the Ocean Continent Transition of the Gulf of Aden Rifted Continental Margin

    NASA Astrophysics Data System (ADS)

    Cowie, Leanne; Kusznir, Nick; Leroy, Sylvie

    2013-04-01

    It has been proposed that some rifted continental margins have anomalous subsidence and that at break-up they were elevated at shallower bathymetries than the isostatic response predicted by classical rift models (McKenzie, 1978). The existence of anomalous syn- or early-post break-up subsidence of this form would have important implications for our understanding of the geodynamics of continental break-up and sea-floor spreading initiation. We have investigated subsidence of the young rifted continental margin of the eastern Gulf of Aden, focussing on the western Oman margin (break-up age 17.6 Ma). Lucazeau et al. (2008) have found that the observed bathymetry here is approximately 1 km shallower than the predicted bathymetry. In order to examine the proposition of an anomalous early post break-up subsidence history of the Omani Gulf of Aden rifted continental margin, we have determined the subsidence of the oldest oceanic crust adjacent to the continent-ocean boundary (COB) using residual depth anomaly (RDA) analysis corrected for sediment loading and oceanic crustal thickness variation. RDAs corrected for sediment loading using flexural backstripping and decompaction have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous subsidence of the Gulf of Aden rifted continental margin. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions of Crosby and McKenzie (2009). Non-zero RDAs at the Omani Gulf of Aden rifted continental margin can be the result of non standard oceanic crustal thickness or the effect of mantle dynamic topography or a non-classical rift and break-up model. Oceanic crustal basement thicknesses from gravity inversion together with Airy isostasy have been used to predict a "synthetic" gravity RDA, in order to determine the RDA contribution from non-standard oceanic crustal thickness. Gravity inversion, used to determine crustal basement thickness

  2. Transport in Porous Fins From Laminar to Turbulent Regime

    NASA Astrophysics Data System (ADS)

    Coletti, Filippo; Muramatsu, Kenshiro; Furciniti, Brian; Elkins, Chris; Eaton, John

    2012-11-01

    Lotus type porous metal has elongated pores of random size and spatial distribution but a common orientation. Sets of so-called lotus fins are obtained by slicing the metal into thin layers and stacking them in the flow path, forcing the fluid to pass through the pores. Lotus fins represent a promising alternative to metal foam heat exchangers, because they offer higher thermal conductivity and lower pressure drop. We have experimentally analyzed the fluid flow and heat transfer in lotus fins to determine their transport properties in a range of flow regimes. The investigated Reynolds numbers based on the pore diameter and inner velocity ranged from 100 to 4000. Three-dimensional mean velocity fields were obtained by magnetic resonance velocimetry performed on magnified replicas of the fins, allowing determination of the mechanical dispersion imposed by the random structure of the fins. Thermal measurements on non-conductive fins provided the global diffusivity coefficient, which accounts for molecular, mechanical and (at high Reynolds number) turbulent diffusion. The latter contribution was isolated and its relevance assessed as a function of the flow regime.

  3. Flux of energy and essential elements through the continental shelf ecosystem. Progress report, May 31, 1980-May 31, 1981

    SciTech Connect

    Pomeroy, L R

    1981-02-01

    There are three distinct areas of research reported, studies of intrusions of the west wall of the Gulf Stream onto the outer continental shelf, studies of the flux of materials across near-shore density fronts, and advances in the understanding of the planktonic food web of the continental shelf. Studies of frontal events on the outer and inner continental shelf involve distinctive physical and chemical regimes and have proven to required distinctive biological approaches. A simulation model of the flux of energy through the continental shelf food web was developed. It represents realistically both details of the energy transfers within the plankton community and the termanal production of fishes. It was discovered that the fecal ribbons of pelagic tunicates break up into flocculent material visually and chemically identical with the flocculent organic aggregates present in sea water. Subsequent experimental work with tunicate fecal matter indicates that some of the naturally occurring aggregates are indeed fecal. This makes it possible to understand and quantify for the first time the production and fate of that population of seston. An examination was made of several of the many roles of dissolved organic compounds in sea water which originate either from release by phytoplankton, digestive processes or metabolites of zooplankton, or extracellular digestion of microorganisms.

  4. Generation of Continental Rifts, Basins and Swells by Lithosphere Instabilities

    NASA Astrophysics Data System (ADS)

    Milelli, L.; Fourel, L.; Jaupart, C. P.

    2012-12-01

    blocks of finite size that became unstable due to cooling from above and describe the peculiar horizontal planform that developed. Dynamical behaviour depends on three dimensionless numbers, a Rayleigh number for the unstable block, a buoyancy number that scales the intrinsic density contrast to the thermal one and the aspect ratio of the block. Within the block, instability develops in two different ways in an outer annulus and in an inner region. In the outer annulus, upwellings and downwellings take the form of radial rolls spaced regularly. In the interior region, the planform adopts the more familiar form of polygonal cells. Translated to geological conditions, such instabilities should manifest themselves as linear rifts striking at a right angle to the continent-ocean boundary and an array of domal uplifts, volcanic swells and basins in the continental interior. The laboratory data lead to simple scaling laws for the dimensions and spacings of the convective structures. For the sub-continental lithospheric mantle, these dimensions and distances take values in the 500-1000 km range, close to geological examples. The large intrinsic buoyancy of Archean lithospheric roots prevents this type of instability, which explains why the widespread volcanic activity that currently affects Western Africa is confined to post-Archean domains.

  5. Yellowstone hotspot-continental lithosphere interaction

    NASA Astrophysics Data System (ADS)

    Jean, Marlon M.; Hanan, Barry B.; Shervais, John W.

    2014-03-01

    The Snake River Plain represents 17 m.y. of volcanic activity that took place as the North American continent migrated over a relatively fixed magma source, or hotspot. We present new Pb, Sr, and Nd data for a suite of 25 basalts collected from Western and Central Snake River Plain (SRP). The new isotope data, combined with previously published data from the SRP, provide a traverse of the Wyoming craton margin, from the 87Sr/86Sr = 0.706 line boundary of western SRP with Phanerozoic accreted terranes, east through the central and eastern SRP, to the Yellowstone Plateau. Low-K basalts from the western SRP, overlain by high-K basalts, provide a temporal record of regional source variation from ∼16.8 to 0.2 Ma. Principal Component Analysis (PCA) of the new and previously published SRP basalt Pb isotopes reveals that >97% of the total variability is accounted for by mixing between three end-members and is consistent with a sublithospheric Yellowstone hotspot mantle source with a radiogenic isotope composition similar to the mantle source of the early Columbia River Basalt Group (CRBG) and two continental lithosphere end-members, heterogeneous in age and composition. We use the SRP Pb, Sr, and Nd isotope data to model the Yellowstone Hotspot-continental lithosphere interaction by three component mixing between two continental lithospheric components, Archean lithosphere (CL1) that represents older lithosphere underlying the Yellowstone Plateau in the east, and Paleoproterozoic lithosphere (CL2) representing the younger lithosphere underlying the SRP in the west near the craton margin, and a sublithospheric end-member, representing the Yellowstone hotspot (PL). The results suggest a continuous flow of PL material westward as the NA continental lithosphere migrated over the upwelling hotspot along a shoaling gradient in the sub-continental mantle lithosphere. The model shows a decrease in Total Lithosphere end-members (CL1 + CL2) and the Lithosphere Ratio (CL1/CL2

  6. Hard thermal loops in static external fields

    SciTech Connect

    Frenkel, J.; Takahashi, N.; Pereira, S. H.

    2009-04-15

    We examine, in the imaginary-time formalism, the high temperature behavior of n-point thermal loops in static Yang-Mills and gravitational fields. We show that in this regime, any hard thermal loop gives the same leading contribution as the one obtained by evaluating the loop integral at zero external energies and momenta.

  7. Idealized Simulations of Precipitation Regimes over Small Tropical Islands

    NASA Astrophysics Data System (ADS)

    Wang, S.; Sobel, A. H.

    2014-12-01

    Tropical islands are global focal points of convection. Observational studies have shown that precipitation over tropical islands is strongly regulated by their size and elevation, and by the large scale prevailing wind. To further develop physical understanding of convection over tropical islands, we perform a set of highly idealized simulations with uniform sea surface temperature to explore flow regimes around an idealized small island (~120 km wide) as a function of large scale wind speed and island elevation. In our simulations the domain as a whole is in radiative-convective equilibrium (RCE), which constrains the domain average precipitation. The island occupies a small part of the domain, so that significant precipitation variations over the island can occur, compensated by smaller anomalies over the larger surrounding area. Over flat islands, as we vary prevailing wind speed, the island experiences three distinct flow regimes: rainfall is greatly enhanced and a local symmetric circulation is formed in the time mean around the island when the prevailing large scale wind speed is small (0 m/s); but there is little rainfall enhancement when the wind speed is increased to a moderate value (~5 m/s). We interpret these two regimes as the shift of triggering mechanism of convection: thermally forced convection due to surface solar heating dominates when large scale wind is very weak, while mechanically forced convection is favored when the impinging wind is moderate. Further increase of the prevailing wind speed to large values leads to strong asymmetry in the windward and leeward side of island and its coastal area, likely due to gravity waves from flow passing over elevated diurnal heating. Topography has a quantitative impact, but does not alter the qualitative shift of flow regimes as a function of wind speed.

  8. Temperature regimes and turbulent heat fluxes across a heterogeneous canopy in an Alaskan boreal forest

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We evaluate local differences in thermal regimes and turbulent heat fluxes across the heterogeneous canopy of a black spruce boreal forest on discontinuous permafrost in interior Alaska. The data was taken during an intensive observing period in the summer of 2013 from two micrometeorological tower...

  9. Transport of particles across continental shelves

    SciTech Connect

    Nittrouer, C.A. ); Wright, L.D. College of William and Mary, Gloucester Point, VA )

    1994-02-01

    Transport of particulate material across continental shelves is well demonstrated by the distributions on the seabed and in the water column of geological, chemical, or biological components, whose sources are found farther landward or farther seaward. This paper addresses passive (incapable of swimming) particles and their transport across (not necessarily off) continental shelves during high stands of sea level. Among the general factors that influence across-shelf transport are shelf geometry, latitudinal constraints, and the timescale of interest. Research studies have investigated the physical mechanisms of transport and have made quantitative estimates of mass flux across continental shelves. Important mechanisms include wind-driven flows, internal wave, wave-orbital flows, infragravity phenomena, buoyant plumes, and surf zone processes. Most particulate transport occurs in the portion of the water column closest to the seabed. Therefore physical processes are effective where and when they influence the bottom boundary layer, causing shear stresses sufficient to erode and transport particulate material. Biological and geological processes at the seabed play important roles within the boundary layer. The coupling of hydrodynamic forces from currents and surface gravity waves has a particularly strong influence on across-shelf transport; during storm events, the combined effect can transport particles tens of kilometers seaward. Several important mechanisms can cause bidirectional (seaward and landward) transport, and estimates of the net flux are difficult to obtain. Also, measurements of across-shelf transport are made difficult by the dominance of along-shelf transport. Geological parameters are often the best indicators of net across-shelf transport integrated over time scales longer than a month. For example, fluvially discharged particles with distinct composition commonly accumulate in the midshelf region. 47 refs., 16 figs.

  10. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  11. Continental scientific drilling program data base: 1982

    SciTech Connect

    Pawloski, G.A.; Howard, N.; Hage, G.; Higuera; M.L.; Richardson, W.

    1982-05-18

    The Continental Scientific Drilling Program (CSDP) data base maintained at Lawrence Livermore National Laboratory is funded by the Office of Basic Energy Sciences of the Department of Energy. It is a central repository of information concerning approximately 1800 government funded and scientifically interesting drill holes in the United States. This data base can help reduce drilling costs and maximize scientific value of drilling efforts of government agencies and industry. The services of the CSDP data base are free of charge and available to all.

  12. Crew coordination concepts: Continental Airlines CRM training

    NASA Technical Reports Server (NTRS)

    Christian, Darryl; Morgan, Alice

    1987-01-01

    The outline of the crew coordination concepts at Continental airlines is: (1) Present relevant theory: Contained in a pre-work package and in lecture/discussion form during the work course, (2) Discuss case examples: Contained in the pre-work for study and use during the course; and (3) Simulate practice problems: Introduced during the course as the beginning of an ongoing process. These concepts which are designed to address the problem pilots have in understanding the interaction between situations and their own theories of practice are briefly discussed.

  13. Structure of continental rifts: Role of older features and magmatism

    SciTech Connect

    Keller, G.R.

    1996-12-31

    Recent geological and geophysical studies in several continental rifts have begun to shed light on the details of the processes which govern the structural evolution of these important exploration targets. In Kenya and Tanzania, the classic East African rift has been the object of several investigations which reveal that its location follows the boundary (suture ?) between the Tanzanian craton (Archean) and Mozambiquan belt (Proterozoic), The Baikal rift also follows a similar boundary, and the Mid-continent rift of North America appears to do the same. Rifts themselves often act as zones of weakness which are reactivated by younger tectonic regimes. The classic North American example of this effect is the Eocambrian Southern Oklahoma aulacogen which was deformed to create the Anadarko basin and Wichita uplift in the late Paleozoic. The Central basin platform has a similar history although the original rift formed at {approximately}1,100Ma. Integration of geophysical data with petrologic and geochemical data from several rift zones has also provided a new picture of the nature and extent of magmatic modification of the crust. An interesting contradiction is that Phanerozoic rifts, except the Afar region, show little evidence for major magmatic modification of the crust whereas, at least in North America, many Precambrian rifts are associated with very large mafic bodies in the crust. The Kenya rift displays evidence for modification of the lower crust in a two-phase magmatic history, but upper crustal magmatic features are limited to local intrusions associated with volcanoes. In this rift, complex basement structure plays a much more important role than previously realized, and the geophysical signatures of basement structure and magmatism are easy to confuse. If this is also the case in other rifts, additional rift basins remain to be discovered.

  14. Structure of continental rifts: Role of older features and magmatism

    SciTech Connect

    Keller, G.R. )

    1996-01-01

    Recent geological and geophysical studies in several continental rifts have begun to shed light on the details of the processes which govern the structural evolution of these important exploration targets. In Kenya and Tanzania, the classic East African rift has been the object of several investigations which reveal that its location follows the boundary (suture ) between the Tanzanian craton (Archean) and Mozambiquan belt (Proterozoic), The Baikal rift also follows a similar boundary, and the Mid-continent rift of North America appears to do the same. Rifts themselves often act as zones of weakness which are reactivated by younger tectonic regimes. The classic North American example of this effect is the Eocambrian Southern Oklahoma aulacogen which was deformed to create the Anadarko basin and Wichita uplift in the late Paleozoic. The Central basin platform has a similar history although the original rift formed at [approximately]1,100Ma. Integration of geophysical data with petrologic and geochemical data from several rift zones has also provided a new picture of the nature and extent of magmatic modification of the crust. An interesting contradiction is that Phanerozoic rifts, except the Afar region, show little evidence for major magmatic modification of the crust whereas, at least in North America, many Precambrian rifts are associated with very large mafic bodies in the crust. The Kenya rift displays evidence for modification of the lower crust in a two-phase magmatic history, but upper crustal magmatic features are limited to local intrusions associated with volcanoes. In this rift, complex basement structure plays a much more important role than previously realized, and the geophysical signatures of basement structure and magmatism are easy to confuse. If this is also the case in other rifts, additional rift basins remain to be discovered.

  15. Earthquakes, elevations and the construction of continental plateaux

    NASA Astrophysics Data System (ADS)

    Goddard, Catherine; Allen, Mark; DePaola, Nicola; Nielsen, Stefan; Saville, Christopher

    2016-04-01

    It has long been noted that larger thrust earthquakes (M>~5) are rare at higher elevations in continental fold-and-thrust belts. For example, the cut-off is the 1250 m elevation contour in the Zagros fold-and-thrust belt, while thrust events are rare above 3500 m in the Himalayas and other fold-and-thrust belts marginal to the Tibetan Plateau. There are various possible explanations for this phenomenon, including aspects of the critical wedge model, but one interpretation which has addressed the relationship is the recognition that higher elevation regions resist major seismogenic thrusting due to the additional gravitational potential energy (GPE) added from the increase in height. Here we have investigated the elevation distribution of earthquake data sets for the Qilian Shan (at the northeast margin of the Tibetan Plateau) and the Zagros, to identify a relationship between elevation and earthquake magnitude. Preliminary findings show a gradual reduction of larger thrust events rather than an abrupt termination. Regression analysis has additionally been carried out on the plots created to test the strength of the relationship found between elevation and magnitude. We aim to repeat this analysis over a variety of different areas via the use of public-domain datasets for seismicity and topography in an attempt to quantify this relationship. We are also investigating an alternative model, where increase in height, and therefore in lithostatic load, creates a thicker zone of distributed deformation above the temperature dependent brittle-plastic transition. This could potentially suppress the ability of large earthquakes to propagate through the entire brittle crust, while still allowing smaller earthquakes to continue to develop above and also below the brittle-ductile transition. Future work will involve laboratory analysis to mimic the increasing conditions of confining pressure experienced by rocks as the regional elevations increase. This will aim to understand

  16. Future changes in climatic water balance determine potential for transformational shifts in Australian fire regimes

    NASA Astrophysics Data System (ADS)

    Boer, Matthias M.; Bowman, David M. J. S.; Murphy, Brett P.; Cary, Geoffrey J.; Cochrane, Mark A.; Fensham, Roderick J.; Krawchuk, Meg A.; Price, Owen F.; Resco De Dios, Víctor; Williams, Richard J.; Bradstock, Ross A.

    2016-06-01

    Most studies of climate change effects on fire regimes assume a gradual reorganization of pyrogeographic patterns and have not considered the potential for transformational changes in the climate-vegetation-fire relationships underlying continental-scale fire regimes. Here, we model current fire activity levels in Australia as a function of mean annual actual evapotranspiration (E) and potential evapotranspiration (E 0), as proxies for fuel productivity and fuel drying potential. We distinguish two domains in E,{E}0 space according to the dominant constraint on fire activity being either fuel productivity (PL-type fire) or fuel dryness (DL-type fire) and show that the affinity to these domains is related to fuel type. We propose to assess the potential for transformational shifts in fire type from the difference in the affinity to either domain under a baseline climate and projected future climate. Under the projected climate changes potential for a transformational shift from DL- to PL-type fire was predicted for mesic savanna woodland in the north and for eucalypt forests in coastal areas of the south–west and along the Continental Divide in the south–east of the continent. Potential for a shift from PL- to DL-type fire was predicted for a narrow zone of eucalypt savanna woodland in the north–east.

  17. Future changes in climatic water balance determine potential for transformational shifts in Australian fire regimes

    NASA Astrophysics Data System (ADS)

    Boer, Matthias M.; Bowman, David M. J. S.; Murphy, Brett P.; Cary, Geoffrey J.; Cochrane, Mark A.; Fensham, Roderick J.; Krawchuk, Meg A.; Price, Owen F.; Resco De Dios, Víctor; Williams, Richard J.; Bradstock, Ross A.

    2016-06-01

    Most studies of climate change effects on fire regimes assume a gradual reorganization of pyrogeographic patterns and have not considered the potential for transformational changes in the climate-vegetation-fire relationships underlying continental-scale fire regimes. Here, we model current fire activity levels in Australia as a function of mean annual actual evapotranspiration (E) and potential evapotranspiration (E 0), as proxies for fuel productivity and fuel drying potential. We distinguish two domains in E,{E}0 space according to the dominant constraint on fire activity being either fuel productivity (PL-type fire) or fuel dryness (DL-type fire) and show that the affinity to these domains is related to fuel type. We propose to assess the potential for transformational shifts in fire type from the difference in the affinity to either domain under a baseline climate and projected future climate. Under the projected climate changes potential for a transformational shift from DL- to PL-type fire was predicted for mesic savanna woodland in the north and for eucalypt forests in coastal areas of the south-west and along the Continental Divide in the south-east of the continent. Potential for a shift from PL- to DL-type fire was predicted for a narrow zone of eucalypt savanna woodland in the north-east.

  18. Raindrop Size Distribution in Different Climatic Regimes from Disdrometer and Dual-Polarized Radar Analysis.

    NASA Astrophysics Data System (ADS)

    Bringi, V. N.; Chandrasekar, V.; Hubbert, J.; Gorgucci, E.; Randeu, W. L.; Schoenhuber, M.

    2003-01-01

    The application of polarimetric radar data to the retrieval of raindrop size distribution parameters and rain rate in samples of convective and stratiform rain types is presented. Data from the Colorado State University (CSU), CHILL, NCAR S-band polarimetric (S-Pol), and NASA Kwajalein radars are analyzed for the statistics and functional relation of these parameters with rain rate. Surface drop size distribution measurements using two different disdrometers (2D video and RD-69) from a number of climatic regimes are analyzed and compared with the radar retrievals in a statistical and functional approach. The composite statistics based on disdrometer and radar retrievals suggest that, on average, the two parameters (generalized intercept and median volume diameter) for stratiform rain distributions lie on a straight line with negative slope, which appears to be consistent with variations in the microphysics of stratiform precipitation (melting of larger, dry snow particles versus smaller, rimed ice particles). In convective rain, `maritime-like' and `continental-like' clusters could be identified in the same two-parameter space that are consistent with the different multiplicative coefficients in the Z = aR1.5 relations quoted in the literature for maritime and continental regimes.

  19. Investigating Continental Margins: An Activity to Help Students Better Understand the Continental Margins of North America

    ERIC Educational Resources Information Center

    Poli, Maria-Serena; Capodivacca, Marco

    2011-01-01

    Continental margins are an important part of the ocean floor. They separate the land above sea level from the deep ocean basins below and occupy about 11% of Earth's surface. They are also economically important, as they harbor both mineral resources and some of the most valuable fisheries in the world. In this article students investigate North…

  20. Deformation and seismicity associated with continental rift zones propagating toward continental margins

    NASA Astrophysics Data System (ADS)

    Lyakhovsky, V.; Segev, A.; Schattner, U.; Weinberger, R.

    2012-01-01

    We study the propagation of a continental rift and its interaction with a continental margin utilizing a 3-D lithospheric model with a seismogenic crust governed by a damage rheology. A long-standing problem in rift-mechanics, known as thetectonic force paradox, is that the magnitude of the tectonic forces required for rifting are not large enough in the absence of basaltic magmatism. Our modeling results demonstrate that under moderate rift-driving tectonic forces the rift propagation is feasible even in the absence of magmatism. This is due to gradual weakening and "long-term memory" of fractured rocks that lead to a significantly lower yielding stress than that of the surrounding intact rocks. We show that the style, rate and the associated seismicity pattern of the rift zone formation in the continental lithosphere depend not only on the applied tectonic forces, but also on the rate of healing. Accounting for the memory effect provides a feasible solution for thetectonic force paradox. Our modeling results also demonstrate how the lithosphere structure affects the geometry of the propagating rift system toward a continental margin. Thinning of the crystalline crust leads to a decrease in the propagation rate and possibly to rift termination across the margin. In such a case, a new fault system is created perpendicular to the direction of the rift propagation. These results reveal that the local lithosphere structure is one of the key factors controlling the geometry of the evolving rift system and seismicity pattern.

  1. Changes in size and trends of North American sea duck populations associated with North Pacific oceanic regime shifts

    USGS Publications Warehouse

    Flint, Paul L.

    2013-01-01

    Broad-scale multi-species declines in populations of North American sea ducks for unknown reasons is cause for management concern. Oceanic regime shifts have been associated with rapid changes in ecosystem structure of the North Pacific and Bering Sea. However, relatively little is known about potential effects of these changes in oceanic conditions on marine bird populations at broad scales. I examined changes in North American breeding populations of sea ducks from 1957 to 2011 in relation to potential oceanic regime shifts in the North Pacific in 1977, 1989, and 1998. There was strong support for population-level effects of regime shifts in 1977 and 1989, but little support for an effect of the 1998 shift. The continental-level effects of these regime shifts differed across species groups and time. Based on patterns of sea duck population dynamics associated with regime shifts, it is unclear if the mechanism of change relates to survival or reproduction. Results of this analysis support the hypothesis that population size and trends of North American sea ducks are strongly influenced by oceanic conditions. The perceived population declines appear to have halted >20 years ago, and populations have been relatively stable or increasing since that time. Given these results, we should reasonably expect dramatic changes in sea duck population status and trends with future oceanic regime shifts.

  2. LINKAGE BETWEEN PRODUCTION AND RESPIRATION ON THE LOUISIANA CONTINENTAL SHELF.

    EPA Science Inventory

    Abstract for presentation. Original title, "PRIMARY PRODUCTION, BACTERIOPLANKTON PRODUCTION, AND COMMUNITY RESPIRATION IN STRATIFIED WATERS OF THE NORTHERN GULF OF MEXICO CONTINENTAL SHELF: LINKAGE TO HYPOXIA."

  3. GPS constraints on the kinematics of continental deformation

    USGS Publications Warehouse

    Thatcher, W.

    2003-01-01

    Recent GPS observations from the western United States, New Zealand, central Greece, and Japan indicate that present-day continental deformation is typically focused in narrow deforming zones whose extent is much smaller than the intervening largely inactive regions. However, these narrow zones are heterogeneously distributed, reflecting the inherent heterogeneity of continental lithospheric strength and internal buoyancy. Plate driving and resisting forces stress plate boundary zones and plate interiors and drive deformation. These forces change continuously and discontinuously, leading to continental deformation that typically evolves and migrates with time. Magmatic and tectonic processes alter lithospheric rheology and internal buoyancy and also contribute to the time-varying character of continental deformation.

  4. Aeromagnetic data and geological structure of continental China: A review

    NASA Astrophysics Data System (ADS)

    Xiong, Sheng-Qing; Tong, Jing; Ding, Yan-Yun; Li, Zhan-Kui

    2016-06-01

    We review the latest aeromagnetic geological data of continental China. We discuss the latest achievements in geological mapping and the newly detected features based on aeromagnetic data. Using aeromagnetic data collected for more than 50 years, a series of 1:5000000 and 1:1000000 aeromagnetic maps of continental China were compiled using state-of-the-art digital technology, and data processing and transformation. Guided by plate tectonics and continental dynamics, rock physical properties, and magnetic anomalies, we compiled maps of the depth of the magnetic basement of continental China and the major geotectonic units, and presented newly detected geological structures based on the aeromagnetic data.

  5. Organic acids in continental background aerosols

    NASA Astrophysics Data System (ADS)

    Limbeck, Andreas; Puxbaum, Hans

    With a newly developed method aerosol samples from three distinctly different continental sites were analyzed: an urban site (Vienna), a savanna site in South Africa (Nylsvley Nature Reserve, NNR) and a free tropospheric continental background site (Sonnblick Observatory, SBO). In all samples a range of monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) has been identified and quantified. The three most abundant MCAs in Vienna were the C18, C16 and C14 acids with concentrations of 66, 45 and 36 ng m -3, respectively. At the mid tropospheric background site (SBO) the three most abundant MCAs were the C18, C16 and C12 acid. For the DCAs at all three sites oxalic, malonic and succinic acid were the dominant compounds. For some individual compounds an information about the sources could be obtained. For example the determined unsaturated MCAs in South Africa appear to result from biogenic sources whereas in Vienna those acids are considered to be derived from combustion processes. Oxalic and glyoxalic acid appear to have a free tropospheric air chemical source. The relative high amounts at SBO in comparison to Vienna can only be explained by secondary formation of oxalic acid in the atmosphere.

  6. Anthropogenic impacts on continental surface water fluxes

    NASA Astrophysics Data System (ADS)

    Haddeland, Ingjerd; Skaugen, Thomas; Lettenmaier, Dennis P.

    2006-04-01

    Impacts of reservoirs and irrigation water withdrawals on continental surface water fluxes are studied within the framework of the Variable Infiltration Capacity (VIC) model for a part of North America, and for Asia. A reservoir model, designed for continental-scale simulations, is developed and implemented in the VIC model. The model successfully simulates irrigation water requirements, and captures the main effects of reservoir operations and irrigation water withdrawals on surface water fluxes, although consumptive irrigation water use is somewhat underestimated. For the North American region, simulated irrigation water requirements and consumptive irrigation water uses are 191 and 98 km3year-1, while the corresponding numbers for the Asian region are 810 and 509 km3year-1, respectively. The consumptive uses represent a decrease in river discharge of 4.2 percent for the North American region, and 2.8 percent for the Asian region. The largest monthly decrease is about 30 percent, for the area draining the Western USA in June. The maximum monthly increase in streamflow (28 percent) is in March for the Asian Arctic region.

  7. Exploring the deep continental crust by drilling

    NASA Astrophysics Data System (ADS)

    Elders, Wilfred A.

    Although geology transcends national boundaries, geologists are not free of national influences. To the question “Is continental scientific drilling an idea whose time has come?,” answers might range from an enthusiastic “yes” in the Soviet Union and the Federal Republic of Germany, and a qualified “yes” in Sweden, to “We hope so” in Canada, France, Japan, the United Kingdom, and elsewhere, but most likely “We don't know” in the United States.In August 1988 at Jaroslavl in the U.S.S.R., Y. A. Kozlovsky, Minister of Geology, challenged participants in the international seminar Superdeep Continental Drilling and Deep Geophysical Research with his proposal for Project GLOBUS, a very-large-scale collaborative study of Earth's crust [Kozlovsky, 1988; Sass and Barber, 1989]. GLOBUS would investigate the crust of all of the world's continents and oceans by a network of geophysical transects, supported by up to 50 deep (5-10 km), to superdeep (>10 km), research boreholes, situated at the nodal points of the net to calibrate the geophysical interpretations and serve as permanent crustal observatories (Figure 1).

  8. Regimes of validity for balanced models

    NASA Astrophysics Data System (ADS)

    Gent, Peter R.; McWilliams, James C.

    1983-07-01

    Scaling analyses are presented which delineate the atmospheric and oceanic regimes of validity for the family of balanced models described in Gent and McWilliams (1983a). The analyses follow and extend the classical work of Charney (1948) and others. The analyses use three non-dimensional parameters which represent the flow scale relative to the Earth's radius, the dominance of turbulent or wave-like processes, and the dominant component of the potential vorticity. For each regime, the models that are accurate both at leading order and through at least one higher order of accuracy in the appropriate small parameter are then identified. In particular, it is found that members of the balanced family are the appropriate models of higher-order accuracy over a broad range of parameter regimes. Examples are also given of particular atmospheric and oceanic phenomena which are in the regimes of validity for the different balanced models.

  9. Earth Regime Network Evolution Study (ERNESt)

    NASA Technical Reports Server (NTRS)

    Menrad, Bob

    2016-01-01

    Speaker and Presenter at the Lincoln Laboratory Communications Workshop on April 5, 2016 at the Massachusetts Institute of Technology Lincoln Laboratory in Lexington, MA. A visual presentation titled Earth Regimes Network Evolution Study (ERNESt).

  10. Historical fire regime in southern California

    USGS Publications Warehouse

    Keeley, Jon E.; Fotheringham, Connie J.

    2003-01-01

    The historical variability in fire regime is a conservative indicator of ecosystem sustainability. Understanding the natural role of fire in chaparral ecosystems is therefore necessary for effective fire management.

  11. A relatively reduced Hadean continental crust

    NASA Astrophysics Data System (ADS)

    Yang, Xiaozhi; Gaillard, Fabrice; Scaillet, Bruno

    2014-05-01

    Among the physical and chemical parameters used to characterize the Earth, oxidation state, as reflected by its prevailing oxygen fugacity (fO2), is a particularly important one. It controls many physicochemical properties and geological processes of the Earth's different reservoirs, and affects the partitioning of elements between coexisting phases and the speciation of degassed volatiles in melts. In the past decades, numerous studies have been conducted to document the evolution of mantle and atmospheric oxidation state with time and in particular the possible transition from an early reduced state to the present oxidized conditions. So far, it has been established that the oxidation state of the uppermost mantle is within ±2 log units of the quartz-fayalite-magnetite (QFM) buffer, probably back to ~4.4 billion years ago (Ga) based on trace-elements studies of mantle-derived komatiites, kimberlites, basalts, volcanics and zircons, and that the O2 levels of atmosphere were initially low and rose markedly ~2.3 Ga known as the Great Oxidation Event (GOE), progressively reaching its present oxidation state of ~10 log units above QFM. In contrast, the secular evolution of oxidation state of the continental crust, an important boundary separating the underlying upper mantle from the surrounding atmosphere and buffering the exchanges and interactions between the Earth's interior and exterior, has rarely been addressed, although the presence of evolved crustal materials on the Earth can be traced back to ~4.4 Ga, e.g. by detrital zircons. Zircon is a common accessory mineral in nature, occurring in a wide variety of igneous, sedimentary and metamorphic rocks, and is almost ubiquitous in crustal rocks. The physical and chemical durability of zircons makes them widely used in geochemical studies in terms of trace-elements, isotopes, ages and melt/mineral inclusions; in particular, zircons are persistent under most crustal conditions and can survive many secondary

  12. Collision zone magmatism aids continental crustal growth

    NASA Astrophysics Data System (ADS)

    Savov, Ivan; Meliksetian, Khachatur; Ralf, Halama; Gevorg, Navasardian; Chuck, Connor; Massimo, D'Antonio; Samuele, Agostini; Osamu, Ishizuka; Sergei, Karapetian; Arkadi, Karakhanian

    2014-05-01

    The continental crust has a broadly andesitic bulk composition and is predominantly generated at convergent margins. However, estimates of the bulk composition of oceanic arcs indicate a bulk composition closer to basalt than to andesite. Hence, reworking processes that transform basaltic island arc crust into andesitic continental crust are essential[1] and explaining growth of andesitic continental crust via accretion of arc crustal fragments remains problematic. Recent studies of magmatism in the Great Tibetan Plateau[2], as site of multiple and still active continent-continent collisions, have proposed that andesitic CC is generated via amalgamation of large volumes of collision-related felsic magmas generated by melting of hydrated oceanic crust with mantle geochemical signatures. We aim to test this hypothesis by evaluating geochemical data from the volcanically and tectonically active Lesser Caucasus region (Armenia, Azerbaijan, Georgia and E. Turkey), as the only other region where active continent-continent collision takes place. We will benefit from the newly compiled volcano-tectonic database of collision-related volcanic and plutonic rocks of Armenia that is comparable in quality and detail to the one available on Tibet. Our dataset combines several detailed studies from the large Aragats shield volcano[3] and associated monogenetic volcanic fields (near the capital city of Yerevan), as well as > 500 Quaternary to Holocene volcanoes from Gegham, Vardenis and Syunik volcanic highlands (toward Armenia-Nagorno-Karabakh-Azerbaijan-Iran border). The Armenian collision-related magmatism is diverse in volume, composition, eruption style and volatile contents. Interestingly, the majority of exposed volcanics are andesitic in composition. Nearly all collision-related volcanic rocks, even the highly differentiated dacite and rhyolite ignimbrites, have elevated Sr concentrations and 87Sr/86Sr and 143Nd/144Nd ratios varying only little (average ~ 0.7043 and ~ 0

  13. Electron transport fluxes in potato plateau regime

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1997-12-01

    Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

  14. Thermal loading of natural streams

    USGS Publications Warehouse

    Jackman, Alan P.; Yotsukura, Nobuhiro

    1977-01-01

    The impact of thermal loading on the temperature regime of natural strea