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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. Thermal regime of the continental lithosphere

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Sass, J. H.

    1984-01-01

    From studies of the global heat flow data set, it has been generalized, with respect to the continental lithosphere, that there is a negative correlation between heat flow and the lithosphere's tectonic edge, and that the lithosphere's thermal evolution is similar to that of the ocean basins, resulting in a 'stable geotherm' in both environments. It is presently noted that a regional study perspective for heat flow data leads to doubts concerning the general applicability of either statement. Rao et al. (1982) have demonstrated that the data are not normally distributed, and that it is not possible to establish a negative correlation between heat flow and age in a rigorous statistical fashion. While some sites of stable continental blocks may have a geotherm that is by chance similar to that for old ocean basins, this need not hold true generally, and many stable continental terranes will be characterized by geotherms very different from those for old ocean basins.

  4. 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)

  5. 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.

  6. Thermal regime of a continental permafrost associated gas hydrate occurrence a continuous temperature profile record after drilling

    NASA Astrophysics Data System (ADS)

    Henninges, J.; Huenges, E.; Mallik Working Group

    2003-04-01

    Both the size and the distribution of natural methane hydrate occurrences, as well as the release of gaseous methane through the dissociation of methane hydrate, are affected by the subsurface pressure and temperature conditions. During a field experiment, which was carried out in the Mackenzie Delta, NWT, Canada, within the framework of the Mallik 2002 Production Research Well Program*, the variation of temperature within three 40 m spaced, 1200 m deep wells was measured deploying the Distributed Temperature Sensing (DTS) technology. An innovative experimental design for the monitoring of spatial and temporal variations of temperature along boreholes was developed and successfully applied under extreme arctic conditions. A special feature is the placement of the fibre-optic sensor cable inside the cement annulus between the casing and the wall of the borehole. Temperature profiles were recorded with a sampling interval of 0.25 m and 5 min, and temperatures can be determined with a resolution of 0.3 °C. The observed variation of temperature over time shows the decay of the thermal disturbances caused by the drilling and construction of the wells. An excellent indicator for the location of the base of the ice-bonded permafrost layer, which stands out as a result of the latent heat of the frozen pore fluid, is a sharp rise in temperature at 604 m depth during the period of equilibration. A similar effect can be detected in the depth interval between 1105 m and 1110 m, which is interpreted as an indicator for the depth to the base of the methane hydrate stability zone. Nine months after the completion of the wells the measured borehole temperatures are close to equilibrium. The mean temperature gradient rises from 9.4 K/km inside the permafrost to 25.4 K/km in the ice-free sediment layers underneath. The zone of the gas hydrate occurrences between 900 m and 1100 m shows distinct variations of the geothermal gradient, which locally rises up to 40 K/km. At the lower

  7. 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.

  8. CSDP: The seismology of continental thermal regimes

    SciTech Connect

    Aki, K.

    1991-05-01

    The past year continued to be extremely productive following up two major breakthroughs made in the preceding year. One of the breakthroughs was 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-multiple scattering theories based on the ray approach. We successfully applied the method to the data from the USGS regional seismic arrays in central California, Long Valley and Island of Hawaii, and obtained convincing results on the scattering Q{sup {minus}1} and intrinsic Q{sup {minus}1} in these areas for the frequency range from 1 Hz to 20 Hz. The frequency dependence of scattering Q{sup {minus}1} is, then, interpreted in terms of random medium with continuous or discrete scatterers. The other breakthrough was the application of T-matrix formulation to the seismic scattering problem. We are currently working on 2-dimensional inclusions with high and low velocity contrast with the surrounding medium. In addition to the above two main lines of research, we were able to use so-called T-phase'' observed on the Island of Hawaii to map the Q value with a good spatial resolution. We found that we can eliminate remarkably well the frequency dependent recording site effect from the T-phase amplitude using the amplification factor for coda waves, further confirming the fundamental separability of source, path and site effects for coda waves, and proving the effectiveness of stochastic modeling of high-frequency seismic waves. 70 refs., 24 figs.

  9. The thermal structure and thermal evolution of the continental lithosphere

    NASA Technical Reports Server (NTRS)

    Morgan, P.

    1984-01-01

    The thermal structure and evolution of the continental lithosphere are examined. Surface heat flow data and the factors which modify them are addressed, and the diversity of thermal phenomena in the lithosphere is discussed in the framework of plate interactions. The lithosphere is divided into three sections for the purposes of discussion. In the upper, near-surface zone, temperatures can be strongly affected by near-surface processes, which must be taken into account in the measurement and evaluation of surface heat flow. The thermal structure of the middle, internal zone of the lithosphere responds to the heat balance and thermal properties of the lithosphere, which define its steady state thermal structure. Internal deformation and magmatic intrusion within this zone, and interaction between the lithosphere and the asthenosphere in the lower boundary zone of the lithosphere cause transient thermal disturbances in the lithosphere. The criteria for defining the base of the thermal lithosphere are briefly discussed.

  10. 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.

  11. Thermal state of continental and oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Hasterok, Derrick P.

    The thermal state of the continental and oceanic lithosphere is reassessed on the basis of new databases for global heat flow and lithospheric heat production, recent advances in thermophysical properties measurements of minerals at high pressures and temperatures, and a better understanding of convective heat loss in young seafloor. The updated global heat flow database incorporates >60,000 records with >44,800 heat flow determinations. The update significantly increases the quantity and spatial coverage of global heat flow data since the last update in 1993. A new family of continental geotherms is proposed that is parametric in surface heat flow and takes advantage of thermophysical property data. The range of geotherms is constrained by xenolith P--T estimates; a cratonic geotherm consistent with a surface heat flow of 40 mW/m2 is particularly well constrained. Upper crustal heat production represents ˜26% of the total surface heat flow. Average heat production for the continental lower crust and mantle are 0.4 muW/m3 and 0.02 muW/m3, respectively. Recent controversy about the interpretation of heat flow observations in young seafloor is resolved by careful filtering of data based on sediment thickness and distance from seamounts and weighting marine studies where the environment of heat flow measurements is carefully documented. Oceanic geotherms, fit to bathymetry and heat flow data, are produced for a plate model with 7 km thick crust, a plate thickness of 95 km, and mantle potential temperature of 1425°C. While the current estimate of global heat loss (44 TW) is reasonable, these new reference models will be instrumental in refining and estimating uncertainty in the solid Earth's global heat loss.

  12. Thermal regimes of Malaysian sedimentary basins

    SciTech Connect

    Abdul Halim, M.F. )

    1994-07-01

    Properly corrected and calibrated thermal data are important in estimating source-rock maturation, diagenetics, evolution of reservoirs, pressure regimes, and hydrodynamics. Geothermal gradient, thermal conductivity, and heat flow have been determined for the sedimentary succession penetrated by exploratory wells in Malaysia. Geothermal gradient and heat-flow maps show that the highest average values are in the Malay Basin. The values in the Sarawak basin are intermediate between those of the Malay basin and the Sabah Basin, which contains the lowest average values. Temperature data were analyzed from more than 400 wells. An important parameter that was studied in detail is the circulation time. The correct circulation time is essential in determining the correct geothermal gradient of a well. It was found that the most suitable circulation time for the Sabah Basin is 20 hr, 30 hr for the Sarawak Basin and 40 hr for the Malay Basin. Values of thermal conductivity, determined from measurement and calibrated calculations, were grouped according to depositional units and cycles in each basin.

  13. 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

  14. 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.

  15. 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

  16. Envisioning, quantifying, and managing thermal regimes on river networks

    Treesearch

    E. Ashley Steel; Timothy J. Beechie; Christian E. Torgersen; Aimee H. Fullerton

    2017-01-01

    Water temperatures fluctuate in time and space, creating diverse thermal regimes on river networks. Temporal variability in these thermal landscapes has important biological and ecological consequences because of nonlinearities in physiological reactions; spatial diversity in thermal landscapes provides aquatic organisms with options to maximize growth and survival....

  17. Envisioning, quantifying, and managing thermal regimes on river networks

    USGS Publications Warehouse

    Steel, E. Ashley; Beechie, Timothy J.; Torgersen, Christian; Fullerton, Aimee H.

    2017-01-01

    Water temperatures fluctuate in time and space, creating diverse thermal regimes on river networks. Temporal variability in these thermal landscapes has important biological and ecological consequences because of nonlinearities in physiological reactions; spatial diversity in thermal landscapes provides aquatic organisms with options to maximize growth and survival. However, human activities and climate change threaten to alter the dynamics of riverine thermal regimes. New data and tools can identify particular facets of the thermal landscape that describe ecological and management concerns and that are linked to human actions. The emerging complexity of thermal landscapes demands innovations in communication, opens the door to exciting research opportunities on the human impacts to and biological consequences of thermal variability, suggests improvements in monitoring programs to better capture empirical patterns, provides a framework for suites of actions to restore and protect the natural processes that drive thermal complexity, and indicates opportunities for better managing thermal landscapes.

  18. Radiogenic heat production, thermal regime and evolution of continental crust

    NASA Astrophysics Data System (ADS)

    Mareschal, Jean-Claude; Jaupart, Claude

    2013-12-01

    Heat flow and heat production data complement seismic information and provide strong constraints on crustal composition, thickness and evolution. They have helped understand the nature of the Mohorovicic discontinuity and the variations in seismic velocities below the Moho. Notably, heat flow studies have delineated the vertical distribution of heat producing elements throughout the crust and in the upper most mantle lithosphere. Analysis of global data sets on heat flow and crustal thickness demonstrate that there is no correlation between these two variables. This is due to the large spatial variations in crustal composition and heat production that exist within a single geological province. For a given crustal thickness, the Moho temperature varies within a wide range (≈ 300 K) depending on surface heat flux and crustal heat production. Thus one cannot use generic models based on a “type” crustal column to calculate crustal geotherms. In stable regions, lower crustal temperatures depend on the amount and vertical distribution of heat producing elements in the crust. These temperatures determine the conditions of crustal stability and impose a limit on the maximum thickness of a stabilized crust.

  19. 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.

  20. Thermal machines beyond the weak coupling regime

    NASA Astrophysics Data System (ADS)

    Gallego, R.; Riera, A.; Eisert, J.

    2014-12-01

    How much work can be extracted from a heat bath using a thermal machine? The study of this question has a very long history in statistical physics in the weak-coupling limit, when applied to macroscopic systems. However, the assumption that thermal heat baths remain uncorrelated with associated physical systems is less reasonable on the nano-scale and in the quantum setting. In this work, we establish a framework of work extraction in the presence of quantum correlations. We show in a mathematically rigorous and quantitative fashion that quantum correlations and entanglement emerge as limitations to work extraction compared to what would be allowed by the second law of thermodynamics. At the heart of the approach are operations that capture the naturally non-equilibrium dynamics encountered when putting physical systems into contact with each other. We discuss various limits that relate to known results and put our work into the context of approaches to finite-time quantum thermodynamics.

  1. 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

  2. Thermal regimes of Mexican spotted owl nest stands

    Treesearch

    Joseph L. Ganey

    2004-01-01

    To evaluate the hypothesis that spotted owls (Strix occidentalis) select habitats with cool microclimates to avoid high daytime temperatures, I sampled thermal regimes in nest areas used by Mexican spotted owls (S. o. lucida) in northern Arizona. I sampled air temperature at 30-min intervals in 30 pairs of nest and random sites...

  3. An assessment of thermal regime in and around Japan

    NASA Astrophysics Data System (ADS)

    Tanaka, Akiko

    2016-04-01

    Terrestrial surface heat flow provides a direct means to estimate the crustal thermal structure. However, the number of heat flow data is limited and spatially very inhomogeneous and even in regions with measurements the data quality varies. To provide an attempt at a higher resolution map of heat flow, we newly measured and acquired thermal conductivity data from existing samples and data. 122 core samples from 42 sites at 37 Japanese volcanoes [Coordinating Committee for Prediction of Volcanic Eruption core analysis group, 2011] were measured for thermal conductivity, thermal capacity, and bulk density, which may be used to improve the thermal regime of volcanoes. Also, to estimate the heat flow using geothermal gradient data, the closest thermal conductivity data is used for each gradient data [Tanaka et al., 2004]. This approach does not take into account geological and hydrodynamical models to use the thermal conductivity, but this assumption works well enough to provide rough estimates of heat flow from geothermal gradient. On the other hand, the depth of magnetic sources based on spectrum analysis of magnetic anomaly data [e.g., Spector and Grant, 1970] is one of several proxies for estimating thermal regime at depth. This analysis is still controversial, however, good correlation between estimated depths of crustal magnetic sources and heat flow suggests that this depth may reflect the broad average temperature. We discuss some of the limitations and possible uses for various data sources.

  4. Geomorphic and Thermal Steady State Regimes: Reality or Wishful Thinking?

    NASA Astrophysics Data System (ADS)

    Lock, J.; Furlong, K.

    2003-04-01

    In many tectonic geomorphic studies, it is assumed that rates of uplift within an orogen are matched by rates of exhumation producing a steady-state orogen. However, the tools used to determine exhumation are thermally driven (e.g. Fission Track, U-Th/He) and exhumation can substantially perturb the crustal thermal regime. Since knowing the thermal regime is key to determining exhumation from thermochronology, problems arise. In order to interpret a rate of exhumation we make the assumption that an area is in thermal 'steady state', which in young active orogens unlikely exists. Taiwan, the Southern Alps, Fiordland, and Nanga Parbat are relatively young mountain belts that have begun to uplift or have experienced increased rates of uplift during the past 5-10 Ma. As there is a time lag between the onset of uplift and achieving geomorphic steady state and again between reaching geomorphic steady state and thermal steady state, these orogens may be too young to have achieved this final stage. Additionally, young orogens may not have experienced a constant rate of uplift and denudation in the time over which the thermochronometers average. Certainly, in the case of the Southern Alps, present uplift rates can not have existed since uplift begun. Therefore, an apparent age is recording a transient thermal state. Even in a case where geomorphic steady state exists i.e. exhumation balances uplift, it is unlikely that a thermal steady state has been reached. This precludes the simple interpretation of exhumation rates often made. When multiple thermochronometers are used, inconsistencies can arise. For example, an increase in the rate of uplift is often observed when comparing the rates of exhumation using different thermochronometers. Our modeling shows that in some cases this phenomena is actually eliminated by considering the transient nature of the thermal regime following the onset of uplift and exhumation of an active orogen. To accurately determine exhumation rate

  5. Spectral effectiveness of engineered thermal cloaks in the frequency regime

    PubMed Central

    Petiteau, David; Guenneau, Sebastien; Bellieud, Michel; Zerrad, Myriam; Amra, Claude

    2014-01-01

    We analyse basic thermal cloaks designed via different geometric transforms applied to thermal cloaking. We evaluate quantitatively the effectiveness of these heterogeneous anisotropic thermal cloaks through the calculation of the standard deviation of the isotherms. The study addresses the frequency regime and we point out the cloak's spectral effectiveness. We find that all these cloaks have comparable effectiveness irrespective of whether or not they have singular conductivity at their inner boundary. However, approximate cloaking with multi-layered cloak critically depends upon the homogenization algorithm and it is shown that the standard deviation varies linearly with the inverse of the number of layers. PMID:25486981

  6. 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.

  7. Duality of thermal regimes is the distinctive characteristic of plate tectonics since the Neoarchean

    NASA Astrophysics Data System (ADS)

    Brown, Michael

    2006-11-01

    Ultrahigh-temperature (UHT) granulite metamorphism is documented predominantly in the Neoarchean to Cambrian rock record, but UHT granulite metamorphism also may be inferred at depth in Cenozoic orogenic systems. The first occurrence of UHT granulite metamorphism in the record signifies a change in geodynamics that generated transient sites of very high heat flow. Many UHT granulite metamorphic belts may have developed in settings analogous to modern continental backarcs; on a warmer Earth, destruction of oceans floored by thinner lithosphere may have generated hotter backarcs than those associated with the modern Pacific ring of fire. Medium-temperature eclogite high- pressure (EHP) granulite metamorphism is documented in the Neoarchean rock record and at intervals throughout the Proterozoic and Paleozoic record. EHP granulite metamorphic belts are complementary to UHT granulite metamorphic belts in that they are generally inferred to record subduction-to-collision orogenesis. Blueschists become evident in the Neoproterozoic rock record, but lawsonite blueschist eclogite metamorphism (high pressure [HP]) and ultrahigh-pressure metamorphism (UHP) characterized by coesite or diamond are predominantly Phanerozoic phenomena. HP-UHP metamorphism registers the low thermal gradients and deep subduction of continental crust during the early stage of subduction-to-collision orogenesis. A duality of metamorphic belts—reflecting a duality of thermal regimes—appears in the record only since the Neoarchean Era. A duality of thermal regimes is the hallmark of modern plate tectonics, and the duality of metamorphic belts is the characteristic imprint of plate tectonics in the rock record. The occurrence of both UHT and EHP granulite metamorphism since the Neoarchean marks the onset of a “Proterozoic plate tectonics” regime, which evolved during a Neoproterozoic transition to the modern plate tectonics regime, characterized by colder subduction as chronicled by HP

  8. Thermal regime of ventilation shafts and its regulation

    SciTech Connect

    Petrov, N.N.; Timoshenko, N.I.

    1986-03-01

    This paper evaluates the regime of air flow through a ventilation shaft and the nondimensional heat-exchange criteria. It is shown that the air temperature in the shaft is affected more by the walls than by the reinforcement structure metal and that the heat released by internal combustion engines could be an alternative source for heating the air. High bypass aircraft turbojet engines decommissioned after their maximum surface life on planes could be used for this purpose. The study of the thermal regime in the shaft in the case of a sudden change of air temperature such as occurs during ventilation reversals has established the requirements for air heating equipment.

  9. 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.

  10. Effect of thermal noise on random lasers in diffusion regime

    NASA Astrophysics Data System (ADS)

    Zarei, Mohammad Ali; Hosseini-Farzad, Mahmood; Montakhab, Afshin

    2015-09-01

    In this paper, we study the effects of thermal noise on the time evolution of a weak light pulse (probe) in the presence of a strong light pulse (pump) within a gain medium which includes random scatterer particles. Suitable thermal noise term is added to a set of four coupled equations including three diffusion equations for energy densities and a rate equation for the upper level population in a four-level gain medium. These equations have been solved simultaneously by Crank-Nicholson numerical method. The main result is that the back-scattered output probe light is increased as the thermal noise strength is increased and simultaneously, with the same rate, the amplified spontaneous emission is decreased. Therefore, the amplified response of the random laser in diffusion regime for the input probe pulse is enhanced due to effect of the thermal noise.

  11. 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.

  12. Thermal Evolution of Continental Rifting in Corsica (France)

    NASA Astrophysics Data System (ADS)

    Seymour, N. M.; Stockli, D. F.; Beltrando, M.; Smye, A.

    2014-12-01

    Present thermal evolution models for continental rifting are based on pure-shear extension (McKenzie 1978), in which crustal and mantle strain is co-located and all rocks cool throughout rifting. However, the multi-phase rift model of Lavier and Manatschal (2006) accommodates lithospheric extension via spatially offset crustal and mantle strains, producing depth-dependent thinning and exhumation of lithospheric mantle. Significant reheating of the upper plate is a natural consequence of this model. We seek to constrain the temperature-time history of the upper-plate Tethyan margin preserved in Corsica to discriminate between the two thermal models. A record of the conditions and timing of reheating is preserved in the age and trace element compositions of metamorphic zircon overgrowths. Zircon from the hanging wall and footwall of the Jurassic-age Belli Piani shear zone (Beltrando et al 2013) were depth-profiled for both U-Pb and trace element concentrations via LA-ICP-MS split streaming. Across both sides of the shear zone, U-Pb ages show a strong population of 275-300 Ma grains. However, a subset of footwall grains show 165-210 Ma overgrowths. These ages indicate that the margin reached temperature conditions sufficient for zircon saturation and subsequent zircon growth. These lower crustal findings are consistent with prior observations made within the sedimentary succession, which records rapid thermal uplift, karstification, and subsequent drowning of Triassic dolostones contemporaneous with the opening of the Alpine Tethys (Decarlis and Lualdis 2008). Ti-in-zircon thermometry yields temperatures of ~720°C in the hanging wall and ~830°C in the footwall. This is consistent with the appearance of overgrowths, and provides further support that the Belli Piani shear zone was active during Jurassic rifting. Collectively, these data point directly to a rift-coeval reheating event that affected the entire crustal pile and lend support to the multi-stage Lavier and

  13. 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

  14. 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.

  15. Photopyroelectric Technique, in the Thermally Thin Regime, for Thermal Effusivity Measurements of Liquids

    NASA Astrophysics Data System (ADS)

    Balderas-López, J. A.; Jaime-Fonseca, M. R.; Díaz-Reyes, J.; Gómez-Gómez, Y. M.; Bautista-Ramírez, M. E.; Muñoz-Diosdado, A.; Gálvez-Coyt, G.

    2016-02-01

    A photopyroelectric methodology using pyroelectric devices in the thermally thin regime, for the measurement of the thermal effusivity of liquids, is described. A commercial buzzer, taking advantage of the pyroelectric activity of the ceramic material (PZT in this case), is used to achieve this goal. Equivalence for thermal effusivity measurements between this photopyroelectric methodology and a previously reported photoacoustic technique, in the front configuration, is established. The thermal effusivity of six liquids was measured using this device, and very good agreement was found with corresponding values reported in the literature.

  16. 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

  17. 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.

  18. 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.

  19. The thermal regimes of the upper mantle beneath Precambrian and Phanerozoic structures up to the thermobarometry data of mantle xenoliths

    NASA Astrophysics Data System (ADS)

    Glebovitsky, V. A.; Nikitina, L. P.; Khiltova, V. Ya.; Ovchinnikov, N. O.

    2004-05-01

    The thermal state of the upper mantle beneath tectonic structures of various ages and types (Archaean cratons, Early Proterozoic accretionary and collisional orogens, and Phanerozoic structures) is characterized by geotherms and by thermal gradients (TG) derived from data on the P- T conditions of mineral equilibria in garnet and garnet-spinel peridotite xenoliths from kimberlites (East Siberia, Northeastern Europe, India, Central Africa, North America, and Canada) and alkali basalts (Southeastern Siberia, Mongolia, southeastern China, southeastern Australia, Central Africa, South America, and the Solomon and Hawaiian islands). The use of the same garnet-orthopyroxene thermobarometer (Theophrastus Contributions to Advanced Studies in Geology. 3: Capricious Earth: Models and Modelling of Geologic Processes and Objects 2000 44) for all xenoliths allowed us to avoid discrepancies in estimation of the P- T conditions, which may be a result of the mismatch between different thermometers and barometers, and to compare the thermal regimes in the mantle in various regions. Thus, it was established that (1) mantle geotherms and geothermal gradients, obtained from the estimation of P- T equilibrium conditions of deep xenoliths, correspond to the age of crust tectonic structures and respectively to the time of lithosphere stabilization; it can be suggested that the ancient structures of the upper mantle were preserved within continental roots; (2) thermal regimes under continental mantle between the Archaean cratons and Palaeoproterozoic belts are different today; (3) the continental mantle under Neoproterozoic and Phanerozoic belts is characterized by significantly higher values of geothermal gradient compared to the mantle under Early Precambrian structures; (4) lithosphere dynamics seems to change at the boundary between Early and Mezo-Neoproterozoic and Precambrian and Phanerozoic.

  20. Distinct zooplankton regime shift patterns across ecoregions of the U.S. Northeast continental shelf Large Marine Ecosystem

    NASA Astrophysics Data System (ADS)

    Morse, R. E.; Friedland, K. D.; Tommasi, D.; Stock, C.; Nye, J.

    2017-01-01

    We investigated regime shifts in seasonal zooplankton communities of the Northeast continental shelf Large Marine Ecosystem (NES) and its subcomponent ecoregions over a multi-decadal period (1977-2013). Our cross ecoregion analysis shows that regime shifts in different ecoregions often exhibited very distinct characteristics, emphasizing more granular fluctuations in NES plankton communities relative to previous work. Shifts early in the time series generally reflected an increase in abundance levels. The response of zooplankton abundance within fall communities was more similar among ecoregions than for spring communities. The Gulf of Maine exhibited highly distinct patterns from other ecoregions, with regime shifts identified in the early 1980s, early 2000s, and mid-2000s for spring communities. Regime shifts were identified in the early to mid-1990s for the NES, Georges Bank, and the Mid-Atlantic Bight ecoregions, while the fall communities experienced shifts in the early 1990s and late 1980s for the NES and Georges Bank, but in the late 1990s in the Mid-Atlantic Bight. A constrained correspondence analysis of zooplankton community against local and basin-scale climatological indices suggests that water temperature, stratification, and the Atlantic multidecadal oscillation (AMO) were the predominant factors in driving the zooplankton community composition.

  1. 3D thermal modelling within the Lofoten-Vesterålen segment of the Mid-Norwegian continental margin

    NASA Astrophysics Data System (ADS)

    Maystrenko, Yuriy P.; Gernigon, Laurent; Gradmann, Sofie; Olesen, Odleiv

    2017-04-01

    A lithosphere-scale 3D structural model has been constructed based on the available structural data to reveal a deep structure of the Lofoten-Vesterålen segment and the northern part of the Vøring segment of the Mid-Norwegian continental margin. The constructed model covers the Vestfjorden, Ribban and Røst basins, the northern parts of the Vøring Basin and the Trøndelag Platform. The model also extends from the Fennoscandian Shield to the north-eastern part of the North Atlantic Ocean. The initial 3D structural model has been refined using a 3D gravity modelling over the whole study area. The final gravity-consistent model has been used as a structural base for a further 3D thermal modelling, which has been made by use of commercial software package COMSOL Multiphysics. As an upper thermal boundary condition, time-dependent temperature at the Earth's surface and sea bottom has been set, considering palaeoclimatic changes due to the last two Europe-scale glaciations (the Saalian and Weichselian glacial periods). The lithosphere-asthenosphere boundary has been used as a lower thermal boundary which corresponds to the 1300 °C isotherm. In addition to the above-mentioned paleoclimatic scenario, the effects of late Cenozoic erosion onshore and sedimentation offshore have been taken into account during the 3D thermal modelling. Results of this thermal modelling indicate that the continent is generally colder than the basin areas within the upper part of the 3D model. In particular, considering the transient perturbations in the near-surface thermal regime, as a result of the post-Paleogene erosion and sedimentation, helps us to understand additional details of subsurface temperature distribution within the study area. The thermal effects of the simultaneous erosion over the mainland and deposition within the basin areas indicate that a positive thermal anomaly should exist onshore, whereas the negative one must occur in the offshore part. These two thermal

  2. 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.

  3. 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

  4. Long-lasting floods buffer the thermal regime of the Pampas

    NASA Astrophysics Data System (ADS)

    Houspanossian, Javier; Kuppel, Sylvain; Nosetto, Marcelo; Di Bella, Carlos; Oricchio, Patricio; Barrucand, Mariana; Rusticucci, Matilde; Jobbágy, Esteban

    2016-10-01

    The presence of large water masses influences the thermal regime of nearby land shaping the local climate of coastal areas by the ocean or large continental lakes. Large surface water bodies have an ephemeral nature in the vast sedimentary plains of the Pampas (Argentina) where non-flooded periods alternate with flooding cycles covering up to one third of the landscape for several months. Based on temperature records from 17 sites located 1 to 700 km away from the Atlantic coast and MODIS land surface temperature data, we explore the effects of floods on diurnal and seasonal thermal ranges as well as temperature extremes. In non-flooded periods, there is a linear increase of mean diurnal thermal range (DTR) from the coast towards the interior of the region (DTR increasing from 10 to 16 K, 0.79 K/100 km, r 2 = 0.81). This relationship weakens during flood episodes when the DTR of flood-prone inland locations shows a decline of 2 to 4 K, depending on surface water coverage in the surrounding area. DTR even approaches typical coastal values 500 km away from the ocean in the most flooded location that we studied during the three flooding cycles recorded in the study period. Frosts-free periods, a key driver of the phenology of both natural and cultivated ecosystems, are extended by up to 55 days during floods, most likely as a result of enhanced ground heat storage across the landscape ( 2.7 fold change in day-night heat transfer) combined with other effects on the surface energy balance such as greater night evaporation rates. The reduced thermal range and longer frost-free periods affect plant growth development and may offer an opportunity for longer crop growing periods, which may not only contribute to partially compensating for regional production losses caused by floods, but also open avenues for flood mitigation through higher plant evapotranspirative water losses.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Archfield, S. A.; Kennen, J.; Carlisle, D.; Wolock, D.

    2013-12-01

    Hydroecological stream classification--the process of grouping streams by similar hydrologic responses and, thereby, similar aquatic habitat--has been widely accepted and is often one of the first steps towards developing ecological flow targets. Despite its importance, the last national classification of streamgauges was completed about 20 years ago. A new classification of 1,534 streamgauges in the contiguous United States is presented using a novel and parsimonious approach to understand similarity in ecological streamflow response. This new 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 hydroecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classes 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.

  7. 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.

  8. 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.

  9. Thermal rejuvenation of continental lithosphere in the Michigan Basin Area

    SciTech Connect

    Ahern, J.L.; Dikeou, P.J.

    1985-01-01

    Using depths to formation tops from almost 500 wells, the authors have determined changes in shape of the Michigan Basin during the Phanerozoic. Flexural rigidity of the lithosphere was then estimated for several time intervals by assuming that changes in shape were caused by deflection of an elastic plate subjected to a disk load. It is found that the flexural rigidity generally increased over time, from less than 10/sup 29/ dyne-cm early in the basin's history, to more than 10/sup 30/ dyne-cm late in the basin's development. They attribute this increase in rigidity to cooling and thickening of the elastic portion of the lithosphere as the basin was subsiding. Low flexural rigidity early in the basin's history indicates that the lithosphere was probably rejuvenated prior to basin subsidence. The rejuvenation process is investigated using a finite-difference thermal model in which a 142-km plate is temporarily heated from below. Taking the depth to the 450/sup 0/C isotherm to be the effective elastic thickness of the lithosphere, rigidity predicted by the thermal model is consistent with the observed increase in rigidity over time. They conclude that the lithosphere in this area was rejuvenated approximately 500 million years ago. As the lithosphere cooled, it thickened; it also contracted and subsided. Observed rapid subsidence between about 500 and 450 million years ago cannot be explained by thermal contraction; in fact, it occurs when the thermal model predicts heating and uplift. This subsidence episode may have been the result of densification processes accompanying rejuvenation.

  10. A downslope propagating thermal front over the continental slope

    NASA Astrophysics Data System (ADS)

    van Haren, Hans; Hosegood, Phil J.

    2017-04-01

    In the ocean, internal frontal bores above sloping topography have many appearances, depending on the local density stratification, and on the angle and source of generation of the carrier wave. However, their common characteristics are a backward breaking wave, strong sediment resuspension, and relatively cool (denser) water moving more or less upslope underneath warm (less dense) water. In this paper, we present a rare example of a downslope moving front of cold water moving over near-bottom warm water. Large backscatter is observed in the downslope moving front's trailing edge, rather than the leading edge as is common in upslope moving fronts. Time series observations have been made during a fortnight in summer, using a 101 m long array of high-resolution temperature sensors moored with an acoustic Doppler current profiler at 396 m depth in near-homogeneous waters, near a small canyon in the continental slope off the Malin shelf (West-Scotland, UK). Occurring between fronts that propagate upslope with tidal periodicity, the rare downslope propagating one resembles a gravity current and includes strong convective turbulence coming from the interior rather than the more usual frictionally generated turbulence arising from interaction with the seabed. Its turbulence is 3-10 times larger than that of more common upslope propagating fronts. As the main turbulence is in the interior with a thin stratified layer close to the bottom, little sediment is resuspended by a downslope propagating front. The downslope propagating front is suggested to be generated by oblique propagation of internal (tidal) waves and flow over a nearby upstream promontory.

  11. Intra-continental transpression and gneiss doming in an obliquely convergent regime in SE Asia

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Chai, Zhi; Yin, Cong Yuan; Huang, Wen Tao; Wang, Yang; Zhang, Jin Jiang; Wang, Xiao Xian; Cao, Kai

    2017-04-01

    The Tengchong terrane comprises a sequence of linear dome-like zones, cored by granite and migmatitic layers. These cores are mantled by predominantly gneiss and subordinate schist sequences, decreasing in deformation intensity outward from extensive mylonitization to weak mylonitization. The pre-doming deformation was characterized by the formation of large-scale top-to-the-east shearing (D1) in the gneiss terrane, locally preserved flat-lying foliation (S1), weak folding (F1) and emplacement of the Mangbang granite during the Cretaceous (114-104 Ma). The second stage of deformation (D2) consisted of map-scale east-verging folds (F2, dome amplification) and minor lateral strike-slip shear zones between the anticlines in the gneiss and migmatitic sequences. Extensive partial melting and emplacement of 67-30 Ma synkinematic granitoid bodies/veins occurred, leading to the emplacement of wedges of granite into the easterly directed F2 fold cores. These wedges formed kilometer-scale granitoid domes. The post-doming D3 deformation with transpression recorded strain partitioning with simple shear-dominated high-strain zones along the Gaoligong and Nabang dextral lateral strike-slip shear zones (active during 30-11 Ma). Late transtensional deformation (D4) during cooling of the entire terrane involved the localized low-temperature Gaoligong west and east detachment faults that controlled the late exhumation of the Gaoligong metamorphic zone (since 10 Ma). Our structural observations, combined with previous studies, suggest that this style of doming is a representative type of intra-continental deformation in the Cenozoic during the oblique India-Asia collision. The actual dome shapes reflect formation of antiforms during compression-dominated transpression, prior to localized strike-slip shearing, in the accommodation belt around the Eastern Himalayan Syntaxis. Vertical exhumation of crustal material by contractional doming played an important role in absorbing the vast

  12. 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

  13. The Effect of Long Lasting Floods on the Thermal Regime of the Pampas

    NASA Astrophysics Data System (ADS)

    Jobbagy, E. G.; Di Bella, C. M.; Nosetto, M. D.; Houspanossian, J.

    2014-12-01

    The presence of large water masses influences the thermal regime on the land, with proximity to the ocean or large continental water bodies having a strong effect on local climate. The vast sedimentary plain of the Pampas (Argentina) has extremely low regional slopes and poor surface drainage networks. Under its temperate subhumid climate this region alternates non-flooded periods with flooding cycles of several years that cover up to one third of the landscape with surface water and bring water tables within 1.5 m form the surface in approximately another third. Based on field temperature records for 50 years from 28 sites located 1 to 700 km away from the Atlantic coast and MODIS land surface temperature data, we explore the effects of floods on diurnal and seasonal thermal amplitude and temperature extremes. In non-flooded periods there is a linear increase of mean diurnal thermal amplitude (MDTA) from the coast towards the interior of the region (MDTA raising from 10 to 18 degrees C, 0.97 degrees C/100 km, r2=0.72). During floods the MTDA of flood prone stations declines between 2 to 4 degrees C depending on surface water coverage in the area. At Pehuajo (500 km away from the ocean, most flooded station), MTDA approached typical coastal values during the three flooding cycles recorded in the study period. Frosts-free periods, which are a key driver of the phenology of both natural and cultivated ecosystems, are extended during flooded periods, while heat waves are reduced in frequency and intensity. Temperature records from shallow groundwater (less than 0.5 m of depth) display a substantial diurnal cycle suggesting that waterlogged land complements surface water bodies in its day/night heat transfer role. Reduced thermal amplitude opens an opportunity for longer crop growing periods, including more intense double cropping, which not only contributes to compensates regional production losses caused by floods but opens an opportunity to mitigate them through

  14. Tracing the thermal evolution of continental lithosphere through depth-dependent extension

    NASA Astrophysics Data System (ADS)

    Smye, A.; Lavier, L. L.; Stockli, D. F.; Zack, T.

    2015-12-01

    Rifting of continental lithosphere requires a mechanism to reduce lithospheric thickness from 100-150 kilometers to close to zero kilometers at the point of rupture. At magma-poor continental margins, this has long-thought to be caused by uniform stretching and thinning of the lithosphere accompanied by passive upwelling of the asthenosphere [1]. For the last thirty years depth-dependent thinning has been proposed as an alternative to this model to explain the anomalously shallow environment of deposition along many continental margins [2, 3]. A critical prediction of this modification is that the lower crust and sub-continental lithospheric mantle undergo a phase of increased heat flow, potentially accompanied by heating, during thinning of the lithospheric mantle. Here, we test this prediction by applying recently developed U-Pb age depth profiling techniques [4] to lower crustal accessory minerals from the exhumed Alpine Tethys and Pyrenean margins. Inversion of diffusion-controlled U-Pb age profiles in rutile affords the opportunity to trace the thermal evolution of the lower crust through the rifting process. Resultant thermal histories are used to calculate thinning factors of the crust and lithospheric mantle by 2D thermo-kinematic models of extending lithosphere. Combined, we use the measured and modeled thermal histories to propose a mechanism to explain the initiation and growth of lithospheric instabilities that lead to depth-dependent thinning at magma-poor continental margins. [1] McKenzie, D. (1978) EPSL 40, 25-32; [2] Royden, L. & Keen, C. (1980) EPSL 51, 343-361; [3] Huismans, R. & Beaumont, C. (2014) EPSL, 407, 148-162; [4] Smye, A. and Stockli, D. (2014) EPSL, 408, 171-182.

  15. 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

  16. 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

  17. Fluid temperatures: Modeling the thermal regime of a river network

    Treesearch

    Rhonda Mazza; Ashley Steel

    2017-01-01

    Water temperature drives the complex food web of a river network. Aquatic organisms hatch, feed, and reproduce in thermal niches within the tributaries and mainstem that comprise the river network. Changes in water temperature can synchronize or asynchronize the timing of their life stages throughout the year. The water temperature fluctuates over time and place,...

  18. 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.

  19. Thermal regimes of Rocky Mountain lakes warm with climate change

    PubMed Central

    Roberts, James J.

    2017-01-01

    Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans. PMID:28683083

  20. Thermal regimes of Rocky Mountain lakes warm with climate change

    USGS Publications Warehouse

    Roberts, James J.; Fausch, Kurt D.; Schmidt, Travis S.; Walters, David M.

    2017-01-01

    Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

  1. Thermal regimes of Rocky Mountain lakes warm with climate change.

    PubMed

    Roberts, James J; Fausch, Kurt D; Schmidt, Travis S; Walters, David M

    2017-01-01

    Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

  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. 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.

  4. Three-dimensional numerical modeling of thermal regime and slab dehydration beneath Kanto and Tohoku, Japan

    NASA Astrophysics Data System (ADS)

    Ji, Yingfeng; Yoshioka, Shoichi; Manea, Vlad Constantin; Manea, Marina; Matsumoto, Takumi

    2017-01-01

    Although the thermal regime of the interface between two overlapping subducting plates, such as those beneath Kanto, Japan, is thought to play an important role in affecting the distribution of interplate and intraslab earthquakes, the estimation of the thermal regime remains challenging to date. We constructed a three-dimensional (3-D) thermal convection model to simulate the subduction of the Pacific plate along the Japan Trench and Izu-Bonin Trench, including the subduction of the Philippine Sea beneath Kanto and investigated the slab thermal regime and slab water contents in this complex tectonic setting. Based on the subduction parameters tested in generic models with two flat oceanic plates, a faster or thicker plate subducting in a more trench-normal direction produces a colder slab thermal regime. The interplate temperature of the cold anomaly beneath offshore Kanto was approximately 300°C colder than that beneath offshore Tohoku at a same depth of 40 km and approximately 600°C colder at a depth of 70 km. The convergence between the two subducting plates produces an asymmetric thermal structure in the slab contact zone beneath Kanto, which is characterized by clustered seismicity in the colder southwestern half. The thermo-dehydration state of the mid-ocean ridge basalt near the upper surface of the subducted Pacific plate controls the interplate seismicity beneath the Kanto-Tohoku region according to the spatial concurrence of the thermo-dehydration and seismicity along the megathrust fault zone of the subducted Pacific plate.

  5. 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.

  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. Extreme hydrodynamic atmospheric loss near the critical thermal escape regime

    NASA Astrophysics Data System (ADS)

    Erkaev, N. V.; Lammer, H.; Odert, P.; Kulikov, Yu. N.; Kislyakova, K. G.

    2015-04-01

    By considering martian-like planetary embryos inside the habitable zone of solar-like stars we study the behaviour of the hydrodynamic atmospheric escape of hydrogen for small values of the Jeans escape parameter β < 3, near the base of the thermosphere, that is defined as a ratio of the gravitational and thermal energy. Our study is based on a 1D hydrodynamic upper atmosphere model that calculates the volume heating rate in a hydrogen-dominated thermosphere due to the absorption of the stellar soft X-ray and extreme ultraviolet (XUV) flux. In case of a monatomic gas, we find that when the β value near the mesopause/homopause level exceeds a critical value of ˜2.5, there exists a steady hydrodynamic solution with a smooth transition from subsonic to supersonic flow. For a fixed XUV flux, the escape rate of the upper atmosphere is an increasing function of the temperature at the lower boundary. Our model results indicate a crucial enhancement of the atmospheric escape rate, when the Jeans escape parameter β decreases to this critical value. When β becomes ≤2.5, there is no stationary hydrodynamic transition from subsonic to supersonic flow. This is the case of a fast non-stationary atmospheric expansion that results in extreme thermal atmospheric escape rates.

  8. 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

  9. 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

  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. 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...

  13. 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...

  14. 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...

  15. 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...

  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. 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...

  18. Thermal regimes and snowpack relations of periglacial talus slopes, Sierra Nevada, California, USA.

    Treesearch

    Constance I Millar; Robert D. Westfall; Diane L. Delany

    2014-01-01

    Thermal regimes of eight periglacial talus slopes, at contrasting elevations, aspects, and substrates, in the Sierra Nevada, California, had complex microclimatic patterns partially decoupled from external conditions. Over three years, warm seasons showed mean talus matrix temperatures and daily variances lower than surfaces and cooler than free-air; talus surface and...

  19. 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...

  20. 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...

  1. A method to transform a variable thermal regime to a physiologically equivalent effective temperature.

    PubMed

    Mitz, Charles; Thome, Christopher; Thompson, Jeroen; Manzon, Richard G; Wilson, Joanna Y; Boreham, Douglas R

    2017-04-01

    We present a method to characterize variable thermal regimes in terms of an equivalent or effective temperature. Our method is based on a first order exponential transformation of a time series of temperatures to yield an exponentially-weighted mean temperature characteristic of the regime and independent of any particular species or end point. The resulting effective temperature or exponential mean, Te¯, offers an improved method for summarizing mean temperature where biological response scales exponentially to temperature. The exponential mean allows growth under varying thermal regimes to be predicted using constant temperature models and offers a compact descriptor communicating the growth capacity of variable thermal regimes. The method combines mathematical simplicity with translatability to different Q10 values without recourse to the underlining time series data. It also provides a quantitative baseline that improves on mean temperature by incorporating the effect of Jensen's inequality and it remains applicable at near zero temperatures where thermal sums lack accuracy. Copyright © 2017. Published by Elsevier Ltd.

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

    Treesearch

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

    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...

  3. 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.

  4. 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)

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

    DOE PAGES

    Kumar, Jitendra; Collier, Nathan; Bisht, Gautam; ...

    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

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

    SciTech Connect

    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 field 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

  7. 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

  8. Thermal Regime Change of a Retreating Polythermal Glacier from Repeat Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Rippin, D. M.; Willis, I. C.; Sevestre, H.

    2014-12-01

    Polythermal glaciers (i.e. glaciers that consist of some combination of both warm and cold ice) are common in the Arctic (e.g. Aschwanden and Blatter, 2005). Recent work (e.g. Rippin et al. 2011; Gusmeroli et al., 2012; Wilson and Flowers, 2013; Wilson et al., 2013) has focussed on how their polythermal structure might change in response to a warming climate. These studies suggest that the nature of future thermal regime change is complex, such that the relative volume of temperate ice in a shrinking glacier may increase or decrease, depending on local geographical, meteorological and hydrological parameters. Here, we present a unique data-set from the well-studied glacier Midtre Lovénbreen in Svalbard, which has shown continued and sustained retreat in recent years. We have a network of ground penetrating radar (GPR) lines from this glacier, first surveyed in 2006 and then repeat-surveyed along exactly the same lines in 2012. Despite significant retreat and thinning, our data suggests that minimal changes in thermal regime have taken place over this period, reinforcing previous observations of a significant lag in the rate at which the thermal regime responds to mass balance changes (cf. Rippin et al., 2011). Such a 'thermal lag' has implications for evolving hydrological and dynamical behaviour of these glaciers, and also for the future mass balance response. In this paper, we comment on the observed changes and consider the implications for our understanding of future thermal regime evolution. ReferencesAschwanden, A., and H. Blatter. 2005. Meltwater production due to strain heating in Storglaciären, Sweden. JGR, 110, doi:10.1029/2005JF000,328. Rippin, D.M., J.L. Carrivick and C. Williams. 2011. Evidence towards a thermal lag in the response of Kårsaglaciären, northern Sweden, to climate change. J. Glac., 57(205), 895-903. Gusmeroli, A., P. Jansson, R. Pettersson and T. Murray. 2012. Twenty years of cold surface layer thinning at Storglaciaren, sub

  9. 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.

  10. The Influence of Groundwater Flow on Thermal Regimes in Mountainous Terrain

    SciTech Connect

    Forster, Craig; Smith, Leslie

    1986-01-21

    Active circulation of cool groundwater in mountainous terrain can cause an advective disturbance of the thermal regime. This factor complicates interpretation of data collected in geothermal exploration programs. An isothermal free-surface model has been developed which provides qualitative insight into the nature of an advective disturbance as it is affected by topography, permeability and climate. A fully coupled model of fluid and heat transfer is being developed for quantitative study of idealized mountain hydrothermal systems.

  11. Seasonal thermal regime and climatic trends in lakes of the Tibetan highlands

    NASA Astrophysics Data System (ADS)

    Kirillin, Georgiy; Wen, Lijuan; Shatwell, Tom

    2017-04-01

    The hydrology of the lake-rich Tibetan Plateau is important for the global climate, yet little is known about the thermal regime of Tibetan lakes due to scant data. We (i) investigated the characteristic seasonal temperature patterns and recent trends in the thermal and stratification regimes of lakes on the Tibetan Plateau and (ii) tested the performance of the one-dimensional lake parameterization scheme FLake for the Tibetan lake system. For this purpose, we combined 3 years of in situ lake temperature measurements, several decades of satellite observations, and the global reanalysis data. We chose the two largest freshwater Tibetan lakes, Ngoring and Gyaring, as study sites. The lake model FLake faithfully reproduced the specific features of the high-altitude lakes and was subsequently applied to reconstruct the vertically resolved heat transport in both lakes during the last 4 decades. The model suggested that Ngoring and Gyaring were ice-covered for about 6 months and stratified in summer for about 4 months per year with a short spring overturn and a longer autumn overturn. In summer the surface mixed boundary layer extended to 6-8 m of depth and was about 20 % shallower in the more turbid Gyaring. The thermal regime of the transparent Ngoring responded more strongly to atmospheric forcing than Gyaring, where the higher turbidity damped the response. According to the reanalysis data, air temperatures and humidity have increased, whereas solar radiation has decreased, since the 1970s. Surprisingly, the modeled mean lake temperatures did not change, nor did the phenology of the ice cover or stratification. Lake surface temperatures in summer increased only marginally. The reason is that the increase in air temperature was offset by the decrease in radiation, probably due to increasing humidity. This study demonstrates that air temperature trends are not directly coupled to lake temperatures and underscores the importance of shortwave radiation for the thermal

  12. 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.

  13. 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.

  14. Changes of soil thermal and hydraulic regimes in the Heihe River Basin.

    PubMed

    Peng, Xiaoqing; Mu, Cuicui

    2017-09-02

    Soil thermal and hydraulic regimes are critical factors influencing terrestrial processes in cold regions. Collection of field data from frozen ground has occurred at point scales, but limited data exist that characterize changes of soil thermal and hydraulic regimes at the scale of the whole Heihe River Basin. This study uses a long-term regional climate model coupled with land surface model to investigate the soil thermal and hydraulic regime changes at a large spatial scale. It also explores potential factors, including the climate and non-climate factors. Results show that there is significant variability in mean annual air temperature (MAAT) of about 0.47 °C/decade during 1980-2013. A time series of area-averaged mean annual soil temperature (MAST) over the whole Heihe River Basin shows a significant increase between 0.25 and 0.36 °C/decade during 1984-2013, with a net change of 0.9 °C. A trend of increasing wetness is found in soil moisture. Frozen days (FD) decreased significantly both in seasonally frozen ground (SFG) regions and permafrost regions, with a net change between 7 and 13 days during 1984-2013. Freezing index (FI) had a positive effect on FD, while thawing index (TI), MAAT, precipitation, and normalized difference vegetation index (NDVI) had a negative effect. These results are important to understand dynamic mechanisms of soil freeze/thaw cycles.

  15. 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.

  16. 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

  17. 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

  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. 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.

  20. 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.

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

    DOE PAGES

    Hoogeboom-Pot, Kathleen M.; Hernandez-Charpak, Jorge N.; Gu, Xiaokun; ...

    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

  2. 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

  3. Hydrodynamics and thermal regime of a shallow reef-atoll rim

    NASA Astrophysics Data System (ADS)

    Maticka, S. A.; Lowe, R.; Monismith, S. G.

    2016-02-01

    As our understanding of reef-system hydrodynamics continues to advance, reef-atoll systems are still not fully understood. Of the reef-atoll research projects, few have focused on the smaller scale physics in these systems. Field observations and Delft3D model simulations are used to identify the dominant physics on the shallow outer rim ( 3 km wide) of a reef-atoll, Scott Reef, in the Timor Sea. Observations are used to understand what governs the thermal climate in these shallow regions. The reef-lagoon is characterized by a horseshoe shape that leaves the lagoon partially exposed to the ocean, with a meso-tidal regime (2-4 m). The physics on the rim appear to be dominated by tides. Temperature fluctuations follow a diurnal heating and cooling regime, with an additional tidal influence.

  4. The effects of regional groundwater flow in the thermal regime of a basin

    SciTech Connect

    Smith, Leslie; Chapman, David S.

    1982-09-01

    Numerical solutions of the equations of fluid flow and heat transport are used to quantify the effects of groundwater flow on the subsurface thermal regime. Simulations are carried out for a vertical section through a basin with a distance of 40 km separating the regional topographic high and low. Emphasis is placed on understanding the conditions under which advective effects significantly perturb the thermal field. The transition from conduction-dominated to advection-dominated thermal regimes is sharp and depends primarily on the topographic configuration of the water table, the magnitude and spatial distribution of permeability, hydraulic anisotropy and depth of active flow. Deviations of surface heat flow from the background heat flux are a measurable effect of groundwater flow and depend on the same factors. Our results show that from zero to almost one hundred per cent of the section may have surface heat flow significantly different from background heat flow, depending upon the nature of the hydrogeologic environment. A limited spatial variability in a distributed set of heat flow measurements and/or linear temperature-depth profiles does not ensure that surface heat flow measurements are not disturbed. The results of our simulations suggest that knowledge of the complete environment of a site, including the water table configuration and subsurface flow system, combined with more closely spaced heat flow measurements may be necessary to unravel the true background heat flux in active flow regions.

  5. A 3-D thermal regime model suitable for cold accumulation zones of polythermal mountain glaciers

    NASA Astrophysics Data System (ADS)

    Gilbert, A.; Gagliardini, O.; Vincent, C.; Wagnon, P.

    2014-09-01

    Analysis of the thermal and mechanical response of high altitude glaciers to climate change is crucial to assess future glacier hazards associated with thermal regime changes. This paper presents a new fully thermo-mechanically coupled transient thermal regime model including enthalpy transport, firn densification, full-Stokes porous flow, free surface evolution, strain heating, surface meltwater percolation, and refreezing. The model is forced by daily air temperature data and can therefore be used to perform prognostic simulations for different future climate scenarios. The set of equations is solved using the finite element ice sheet/ice flow model Elmer/Ice. This model is applied to the Col du Dôme glacier (Mont Blanc area, 4250 m a.s.l., France) where a comprehensive data set is available. The results show that the model is capable of reproducing observed density and velocity fields as well as borehole temperature evolution. The strong spatial variability of englacial temperature change observed at Col du Dôme is well reproduced. This spatial variability is mainly a result of the variability of the slope aspect of the glacier surface and snow accumulation. Results support the use of this model to study the influence of climate change on cold accumulation zones, in particular to estimate where and under what conditions glaciers will become temperate in the future.

  6. Thermal regime, hydrocarbon maturation and geodynamic events along the western margin of India since late Cretaceous

    NASA Astrophysics Data System (ADS)

    Pandey, O. P.; Agrawal, P. K.

    2000-11-01

    The passive continental margin of western India and the adjacent offshore region are associated with a transitional type thinned crust. It contains several sedimentary basins where substantial recoverable oil/gas reserves exist. The northern Cambay graben, northern and eastern parts of the Bombay offshore and the Konkan coast region that are situated close to western margin exhibit reasonably high heat flow and geothermal gradients beneath which the asthenosphere is upwarped to a depth of 30-70 km. Temperatures at the depth of 3 km are estimated to be in the range of 105-260°C. Curie depth analysis from MAGSAT studies in an area between latitudes 11°N and 19°N and longitudes 65°E and 73°E also indicates a high geothermal gradient of about 30°C/km within the upper crustal column. We suggest that the occurrence of oil and gas in these areas may be due to catastrophic and geodynamic events which took place in the last 130 Ma. India's super-mobility, continental breakups, possible bolide impact and Deccan volcanic episode at the western margin resulted in substantial lithospheric heating, accompanied by subcrustal melting and rise of isotherms, to eventually enhance the hydrocarbon maturation process. The study indicates that all other sedimentary basins situated on the western margin are also thermally mature and may have high potential for the occurrence of hydrocarbons.

  7. Thermal regimes and effusive trends at Nyamuragira volcano (DRC) from MODIS infrared data

    NASA Astrophysics Data System (ADS)

    Coppola, D.; Cigolini, C.

    2013-08-01

    Nyamuragira volcano is one of the most active African volcanoes. Eruptions have been occurring every 3-4 years throughout the last century. Here, we analyse satellite infrared data, collected by MODIS sensor to estimate the volcanic radiative power (VRP, in W) and energy (VRE; in J) released during the 2001, 2002, 2004, 2006-2007, 2010 and 2011-2012 eruptions. Based on the statistical distribution of VRP measurements, we found that thermal emissions at Nyamuragira fall into three distinct radiating regimes. The high-radiating regime occurs during the emplacement of poorly insulated lava flows and characterise most of the effusive activity. The moderate-radiating regime is associated with open-vent activity (Strombolian explosions and/or lava lake activity) eventually accompanied by the emplacement of short-lived and well-insulated flows. A third radiating regime (low-radiating regime) occurs during periods, which may last weeks to months, that follow each eruption and are associated with the cooling of the effused lava flows. By applying the radiant density approach to MODIS-derived VRP we also estimated the time-averaged lava discharge rates (TADR; in m3 s-1) and we analysed the effusive trends of the above eruptions. We found that the transition between the effusive and open-vent activity typically takes place when TADR reduces to low values (<5 m3 s-1) and marks a change in the eruptive style of the volcano. Finally, we observed a clear correlation between the volume of erupted lava and its cooling time. This suggests that the average thickness of the analysed lava flows is more variable than previously thought and sheds light on the uncertainty in calculating erupted volumes assuming that lava flow areas have uniform thickness.

  8. Seabeam and seismic reflection imaging of the tectonic regime of the Andean continental margin off Peru (4°S to 10°S)

    NASA Astrophysics Data System (ADS)

    Bourgois, J.; Pautot, G.; Bandy, W.; Boinet, T.; Chotin, P.; Huchon, P.; Mercier de Lepinay, B.; Monge, F.; Monlau, J.; Pelletier, B.; Sosson, M.; von Huene, R.

    1988-01-01

    Marine geophysical surveys employing Seabeam, multi- and single-channel seismic reflection, gravity and magnetic instruments were conducted at two locations along the continental slope of the Peru Trench during the Seaperc cruise of the R/V "Jean Charcot" in July 1986. These areas are centered around 5°30'S and 9°30'S off the coastal towns of Paita and Chimbote respectively. These data indicate that (1) the continental slope off Peru consists of three distinct morpho-structural domains (from west to east are the lower, middle and upper slopes) instead of just two as previously reported; (2) the middle slope has the characteristics of a zone of tectonic collapse at the front of a gently flexured upper slope; (3) the upper half of the lower slope appears to represent the product of mass wasting; (4) thrusting at the foot of the margin produces a continuous morphologic feature representing a deformation front where the products of mass-wasting are overprinted by a compressional tectonic fabric; (5) a change in the tectonic regime from tensional to compressional occurs at the mid-slope-lower slope boundary, the accretionary prism being restricted to the very base of the lower slope in the Paita area. The Andean margin off Peru is an "extensional active margin" or a "collapsing active margin" developing a subordinated accretionary complex induced by massive collapse of the middle slope area.

  9. Thermal and isostatic consequences of simple shear extension of the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Issler, Dale; McQueen, Herbert; Beaumont, Christopher

    1989-01-01

    Quantitative results are presented for a model involving large-scale simple shear of continental lithosphere. The locally compensated, finite element model includes the effects of sedimentation, radiogenic heat production in the crust and sediments, and finite rates of extension. Flexural effects during firting are examined using a simple shear model with a uniform initial elastic thickness. The locally compensated model predicts that a breakup unconformity develops on the upper plate when extension occurs at typical plate tectonic velocities. Subsidence occurs as the upper and lower lithospheric plates separate. Extension creates the potential for large accumulations of sediment ( ˜ 20 km), most of which is syn-rift if sedimentation keeps pace with subsidence. The effect of flexure is to modify the shape of the detachment surface and the uplift patterns on the flanks of the upper and lower plate sedimentary basins. A model which incorporates flexure predicts significant uplift of the lower plate as it is unloaded by the upper plate during extension. The Wernicke simple shear model can be distinguished from its opposite end member, the McKenzie pure shear model, by the predicted asymmetry in thermal evolution (higher predicted heat flux within the upper plate), uplift/subsidence histories and stratigraphic development of the upper and lower plates.

  10. 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.

  11. 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.

  12. 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

  13. Quasiparticle explanation of the weak-thermalization regime under quench in a nonintegrable quantum spin chain

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Ju; Motrunich, Olexei I.

    2017-02-01

    The eigenstate thermalization hypothesis provides one picture of thermalization in a quantum system by looking at individual eigenstates. However, it is also important to consider how local observables reach equilibrium values dynamically. Quench protocol is one of the settings to study such questions. A recent numerical study [Bañuls, Cirac, and Hastings, Phys. Rev. Lett. 106, 050405 (2007), 10.1103/PhysRevLett.106.050405] of a nonintegrable quantum Ising model with longitudinal field under such a quench setting found different behaviors for different initial quantum states. One particular case called the "weak-thermalization" regime showed apparently persistent oscillations of some observables. Here we provide an explanation of such oscillations. We note that the corresponding initial state has low energy density relative to the ground state of the model. We then use perturbation theory near the ground state and identify the oscillation frequency as essentially a quasiparticle gap. With this quasiparticle picture, we can then address the long-time behavior of the oscillations. Upon making additional approximations which intuitively should only make thermalization weaker, we argue that the oscillations nevertheless decay in the long-time limit. As part of our arguments, we also consider a quench from a BEC to a hard-core boson model in one dimension. We find that the expectation value of a single-boson creation operator oscillates but decays exponentially in time, while a pair-boson creation operator has oscillations with a t-3 /2 decay in time. We also study dependence of the decay time on the density of bosons in the low-density regime and use this to estimate decay time for oscillations in the original spin model.

  14. Few genetic and environmental correlations between life history and stress resistance traits affect adaptation to fluctuating thermal regimes.

    PubMed

    Manenti, T; Sørensen, J G; Moghadam, N N; Loeschcke, V

    2016-09-01

    Laboratory selection in thermal regimes that differed in the amplitude and the predictability of daily fluctuations had a marked effect on stress resistance and life history traits in Drosophila simulans. The observed evolutionary changes are expected to be the result of both direct and correlated responses to selection. Thus, a given trait might not evolve independently from other traits because of genetic correlations among these traits. Moreover, different test environments can induce novel genetic correlations because of the activation of environmentally dependent genes. To test whether and how genetic correlations among stress resistance and life history traits constrain evolutionary adaptation, we used three populations of D. simulans selected for 20 generations in constant, predictable and unpredictable daily fluctuating thermal regimes and tested each of these selected populations in the same three thermal regimes. We explored the relationship between genetic correlations between traits and the evolutionary potential of D. simulans by comparing genetic correlation matrices in flies selected and tested in different thermal test regimes. We observed genetic correlations mainly between productivity, body size, starvation and desiccation tolerance, suggesting that adaptation to the three thermal regimes was affected by correlations between these traits. We also found that the correlations between some traits such as body size and productivity or starvation tolerance and productivity were determined by test regime rather than selection regime that is expected to limit genetic adaptation to thermal regimes in these traits. The results of this study suggest that several traits and several environments are needed to explore adaptive responses, as genetic and environmentally induced correlations between traits as results obtained in one environment cannot be used to predict the response of the same population in another environment.

  15. 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.

  16. The consequences of hotspots on continental lithosphere : a thermal case study on the Arabian Plate.

    NASA Astrophysics Data System (ADS)

    Vicente De Gouveia, S.; Besse, J.; Greff-Lefftz, M.; Frizon de Lamotte, D.; Leparmentier, F.; Lescanne, M.

    2015-12-01

    Hotspots are thermal instabilities coming from various depths in the mantle. Their activity is often revealed by surface and sub-surface phenomena such as volcanic trapps or oceanic plateaus, and volcanic island tracks on the seafloor. The two first are often linked to the eruption of a hotspot head, while the third is due to the volcanic material fed by the subsequent tail. Consequences of a hotspot tail on the oceanic lithosphere are well known, while its effect on the continental lithosphere is most often masked by the thickness of the lithosphere. The aim of our study is to try and link hotspot tracks with geological events in the continental lithosphere. Hotspot tracks are first built using a modified version of the hybrid reference frame of Seton et al. (2012), and their effect on the continental lithosphere is then evaluated using geological markers issued from petroleum wells, in particular the sedimentary record, backstripping, heat flux anomaly and temperature data. A case study is performed on the Arabian Plate, potentially crossed by two hotspots (Afar and Comores). Several W-E heat flux profiles display a large thermal anomaly close to the Red Sea, while a smaller N-S elongated heat flow anomaly more to the E suggests that a hotspot track could impact the thermal history of the Arabian plate.

  17. 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

  18. 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.

  19. 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

  20. Many-body formalism for thermally excited wave packets: A way to connect the quantum regime to the classical regime

    NASA Astrophysics Data System (ADS)

    Chenu, Aurélia; Combescot, Monique

    2017-06-01

    Free classical particles have well-defined momentum and position, while free quantum particles have well-defined momentum but a position fully delocalized over the sample volume. We develop a many-body formalism based on wave-packet operators that connects these two limits, the thermal energy being distributed between the state spatial extension and its thermal excitation. The corresponding mixed quantum-classical states, which render the Boltzmann operator diagonal, are the physically relevant states when the temperature is finite. The formulation of many-body Hamiltonians in terms of these thermally excited wave packets and the resulting effective scatterings is provided.

  1. The plasma wake field excitation: Recent developments from thermal to quantum regime

    NASA Astrophysics Data System (ADS)

    Fedele, Renato; Tanjia, Fatema; de Nicola, Sergio; Jovanović, Dušan; Jovanović

    2013-12-01

    To describe the transverse nonlinear and collective self-consistent interaction of a long relativistic electron or positron beam with an unmagnetized plasma, a pair of coupled nonlinear differential equations were proposed by Fedele and Shukla in 1992 (Fedele, R. and Shukla, P. K. 1992a Phys. Rev. A 45, 4045). They were obtained within the quantum-like description provided by the thermal wave model and the theory of plasma wake field excitation. The pair of equations comprises a 2D Schrödinger-like equation for a complex wave function (whose squared modulus is proportional to beam density) and a Poisson-like equation for the plasma wake potential. The dispersion coefficient of the Schrödinger-like equation is proportional to the beam thermal emittance. More recently, Fedele-Shukla equations have been further applied to magnetized plasmas, and solutions were found in the form of nonlinear vortex states and ring solitons. They have been also applied to plasma focusing problems and extended from thermal to quantum regimes. We present here a review of the original approach, and subsequent developments.

  2. 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.

  3. Response of high-mountain Altai thermal regime to climate global warming of recent decades

    NASA Astrophysics Data System (ADS)

    Bezuglova, N. N.; Zinchenko, G. S.; Malygina, N. S.; Papina, T. S.; Barlyaeva, T. V.

    2012-12-01

    The paper presents a brief climatic characteristic and statistical analysis on dynamics of thermal regime in Altai Mountains. The close correlation between temperature series of the Russian and northern part of Mongolian Altai was determined. It was found that the rate of temperature increase for the period under consideration (1940-2008) ranged from 0.19 to 0.53 °С/10 years, and the most significant increase was registered during the cold seasons. During the maximum global warming (1980-1999), a 2-4.5 times increase of annual average temperature was observed as compared to the period of 1940-1979. The temperature series variations obtained with the Welch's method and wavelet analysis correspond to the periods of North Atlantic Oscillation and solar activity variation.

  4. 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.

  5. 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.

  6. Soil Thermal and Moisture Regimes in the Canadian Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Sushama, L.; Laprise, R.; Caya, D.

    2004-05-01

    Soil moisture, with its high spatial and temporal variability, is important in understanding and predicting a large number of processes including land-atmospheric interactions. In many northern-latitude regions, spring melt-water derived from the winter snow pack represents the greatest source for the yearly ground moisture budget. The ability of the Canadian Regional Climate model (CRCM4.0) with its three-layer, physically based, land-surface scheme (CLASS) to simulate the hydrological cycle, especially the soil moisture and thermal regimes, over a domain covering Eastern Canada and part of Eastern United States, is investigated. The CRCM was driven by NCEP reanalyses and was run at 45-km horizontal grid-point spacing for a five-year period from 1993-1997. The model simulates reasonably well the annual cycle of soil moisture variation. Air-soil temperature phase-space diagrams are examined for regions with (1) no snow-cover, (2) seasonal snow-cover and (3) permanent snow-cover. The annual air/soil thermal orbits help assess the nature of the heat transfer process in the subsurface qualitatively and hence in identifying areas of conductive and non-conductive regimes of the subsurface. In high-latitude cold regions with permanent snow-cover, the heat transfer is predominantly conductive, whereas in regions with seasonal snow-cover, the heat transfer is mostly non-conductive during periods of phase change. The top layers in regions of no snow-cover, in the domain considered, also exhibit seasonal nonconductive type of heat transfer. The hydrological fields such as snow-cover, precipitation and runoff are also verified against observations over two northern basins. The simulated basin average values of the various hydrological fields agree very well with observations. The closely coupled average energy partitioning and water partitioning are also simulated reasonably well in the model.

  7. 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

  8. 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.

  9. Thermal convection and the convective regime diagram in super-Earths

    NASA Astrophysics Data System (ADS)

    Miyagoshi, Takehiro; Kameyama, Masanori; Ogawa, Masaki

    2015-07-01

    Numerical models of bottom-heated thermal convection of highly compressible fluid with strongly temperature-dependent viscosity are presented to understand how the Rayleigh number Ra and the temperature dependence of viscosity exert control over the regimes of thermal convection in massive super-Earths. Thermodynamic properties of mantle materials are pressure dependent, but other material properties including the viscosity are not. A stagnant lid develops along the surface of the planet, when the viscosity contrast across the mantle due to temperature dependence r exceeds 106 at high Rayleigh number relevant to super-Earths. The threshold in r, which increases with increasing Ra, is higher than that expected for the Earth from earlier Boussinesq models. The efficiency of convective heat transport measured by the Nusselt number Nu is considerably lower than that expected from Boussinesq models; Nu depends on Ra and r as Nu = 59 ṡ r- 0.23 ṡ (Ra/109)0.27, when r ≤ 105. Strong adiabatic compression significantly reduces the activity of hot ascending plumes especially at high r. At r relevant for super-Earths, hot ascending plumes lose their buoyancy on their way and hardly reach the surface boundary: hot spot volcanism due to ascending plumes is probably suppressed on super-Earths. The lithosphere is considerably thicker than that suggested by earlier Boussinesq models and is unlikely to show a plate-like behavior.

  10. Thermal history and evolution of the Rio de Janeiro - Barbacena section of the southeastern Brazilian continental margin

    NASA Astrophysics Data System (ADS)

    Neri Gezatt, Julia; Stephenson, Randell; Macdonald, David

    2015-04-01

    The transect between the Brazilian cities of Rio de Janeiro and Barbacena (22°54'S, 43°12'W and 21°13'S, 43°46'W, respectively) runs through a segment of a complex range of N-NE/S-SW trending basement units of the Ribeira Belt and southern Sao Francisco Craton, intensely reworked during the Brasiliano-Pan-African orogenic cycle. The ortho- and paragneisses in the area have metamorphic ages between 650 and 540 Ma and are intruded by pre-, syn- and post-tectonic granitic bodies. The transect, perpendicular to the strike direction of the continental margin, crosses the Serra do Mar escarpment, where the sample density is higher in order to better constrain occasional significant age changes. For logistical reasons, the 40 samples collected were processed in two separate batches for apatite fission track (AFT) analysis. The first batch comprised 19 samples, from which 15 produced fission track ages. Analyses were carried out at University College London (UCL), following standard procedures. Preliminary results for the study show AFT ages between 85.9±6.3 and 54.1±4.2 Ma, generally with younger ages close to the coast and progressively older ages towards the continental interior. The highest area sampled, around the city of Teresopolis, ranges from 740 to 1216 m above sea level and shows ages between 85.9±6.3 and 71.3±5.3 Ma. There is no evident lithological or structural distribution control. Medium track length values range from 12.57 to 13.89 µm and distributions are unimodal. Thermal history modelling was done using software QTQt. Individual sample model cooling curves can be divided into two groups: a dominant one, showing a single, slower cooling trend, and a second one with a rapid initial cooling curve, which becomes less steep around 65 Ma. In both groups the maximum paleotemperatures are around 110 Ma. The thermal history model for the first batch of samples is compatible with a single cooling event for the area following continental rifting and

  11. Miniaturized non-thermal atmospheric pressure plasma jet—characterization of self-organized regimes

    NASA Astrophysics Data System (ADS)

    Schäfer, J.; Foest, R.; Ohl, A.; Weltmann, K.-D.

    2009-12-01

    The study reports for the first time on self-organization effects in a radio frequency (RF) plasma generated with a miniaturized non-thermal atmospheric pressure plasma jet. The source is configured as a capacitively coupled RF jet (27.2 MHz) with two outer ring electrodes around a quartz capillary (d = 4.0 mm) between which a gas mixture flows at typical rates of 0.05—5 slm. The application background of this source is the deposition of thin films with a PECVD process. Therefore, thin film producing agents can be added in small quantities downstream the active discharge region. Commonly, the time-resolved observation of the discharge development reveals that the discharge consists of distinct discharge filaments that appear stochastically and evolve alongside the wall of the capillary. This stochastic mode can be easily found under most situations. However, under special conditions, a quasi-laminar flow is established and a controlled number of equidistant filaments develop which form fixed discrete rotating patterns (locked mode). In this paper, a systematic study is performed using Ar as process gas to define the range of existence of the locked mode. The temporal discharge behaviour is studied by performing a low frequency analysis on the optical emission of the plasma. RF power, gas flow rate and electrode distance are interpreted as scaling parameters that are responsible for the self-organization in the non-thermal atmospheric pressure plasma jet. The appearance of the different discharge regimes is described on a phenomenological basis and the collective behavior of the discharge filaments is explained based on the thermal interference of the discharge channels with the gas flow inside the capillary.

  12. 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.

  13. 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%.

  14. 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

  15. 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.

  16. 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.

  17. Models of the thermal effects of melt migration at continental interiors, with applications to the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Johnson, A.; Roy, M.

    2016-12-01

    The relative plate motion of continental regions with respect to underlying asthenosphere produces shear forces which change the physical characteristics of the lithospheric plate. Dynamic pressure gradients created by relative motion between variable thickness lithosphere and the mantle beneath determine the path with which melt migrates by percolative flow towards the surface. This melt migration introduces a warming effect which weakens the lithospheric structure, especially in areas where melt is focused. The temperature profile of the lithosphere is modified by melt migration which leads to further changes in the shape and structure of the lithosphere through deformation and weakening. We build upon previous models in which a solid matrix with constant porosity and permeability with pore space filled with low-viscosity melt comprises a two-phase medium. We focus on deformation in regions with thicker than average lithosphere, where a protruding ``keel'' interacts with the underlying asthenosphere. In this model, advective heat transport in porous flow is introduced in the limit that inter-phase heat transfer dominates over the intra-phase thermal conduction of both solid and melt. The heat transfer coefficient for inter-phase heat exchange, dependent on the pore distribution and grain geometry, parameterizes the model. Our model quantatively assesses the spatially variable thermal weakening and its effect on melt transport. By understanding the way in which melt transport produces the surface spatial and temporal distribution of magmatic activity, continental interior regions with a variable thickness lithosphere, such as the colorado plateau, can be better understood.

  18. Temporal Changes in the Thermal Regime of Devils Hole, Death Valley National Park

    NASA Astrophysics Data System (ADS)

    Hausner, M. B.; Wilson, K. P.; Gaines, B.; Suarez, F. I.; Tyler, S. W.

    2012-12-01

    Devils Hole, a fracture in the carbonate bedrock underlying the Mojave Desert, is home to a unique ecosystem that includes the only extant population of the critically endangered Devils Hole pupfish (Cyprinodon diabolis). The pupfish inhabit an extremely limited ecosystem (~50 m2) and live near the thresholds of survivability for both temperature (~33.5 °C) and dissolved oxygen (~2.5 mg l-1). These factors combine to make the Devils Hole ecosystem very susceptible to small perturbations in its environment. In the late 1960s, the ecosystem was severely impacted when local groundwater mining dropped the water table below the shallow shelf that provides optimum spawning and foraging habitats in the ecosystem; the population of C. diabolis fell to approximately 100 individuals. Although the water table rose and the pupfish population appeared to recover after the cessation of pumping, a second population decline began in the mid 1990s, leading to surveys that counted as few as 38 individuals. Since water temperature acts as a significant control on pupfish reproduction, it is hypothesized that climate change has contributed to this decline. We examine the past, present, and future thermal regime of the Devils Hole ecosystem using a combination of field data, hydrodynamic simulations, and climate models. The impacts of temperature changes on the annual recruitment of Devils Hole pupfish are discussed, and several potential management strategies are presented to mitigate these effects.

  19. Thermal-diffusional Instability in White Dwarf Flames: Regimes of Flame Pulsation

    NASA Astrophysics Data System (ADS)

    Xing, Guangzheng; Zhao, Yibo; Modestov, Mikhail; Zhou, Cheng; Gao, Yang; Law, Chung K.

    2017-05-01

    Thermal-diffusional pulsation behaviors in planar as well as outwardly and inwardly propagating white dwarf (WD) carbon flames are systematically studied. In the 1D numerical simulation, the asymptotic degenerate equation of state and simplified one-step reaction rates for nuclear reactions are used to study the flame propagation and pulsation in WDs. The numerical critical Zel’dovich numbers of planar flames at different densities (ρ = 2, 3, and 4 × 107 g cm-3) and of spherical flames (with curvature c = -0.01, 0, 0.01, and 0.05) at a particular density (ρ = 2 × 107 g cm-3) are presented. Flame front pulsation in different environmental densities and temperatures are obtained to form the regime diagram of pulsation, showing that carbon flames pulsate in the typical density of 2 × 107 g cm-3 and temperature of 0.6 × 109 K. While being stable at higher temperatures, at relatively lower temperatures, the amplitude of the flame pulsation becomes larger. In outwardly propagating spherical flames the pulsation instability is enhanced and flames are also easier to quench due to pulsation at small radius, while the inwardly propagating flames are more stable.

  20. 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.

  1. 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

  2. Effect of snow cover on pan-Arctic permafrost thermal regimes

    NASA Astrophysics Data System (ADS)

    Park, Hotaek; Fedorov, Alexander N.; Zheleznyak, Mikhail N.; Konstantinov, Pavel Y.; Walsh, John E.

    2015-05-01

    This study quantitatively evaluated how insulation by snow depth (SND) affected the soil thermal regime and permafrost degradation in the pan-Arctic area, and more generally defined the characteristics of soil temperature (TSOIL) and SND from 1901 to 2009. This was achieved through experiments performed with the land surface model CHANGE to assess sensitivity to winter precipitation as well as air temperature. Simulated TSOIL, active layer thickness (ALT), SND, and snow density were generally comparable with in situ or satellite observations at large scales and over long periods. Northernmost regions had snow that remained relatively stable and in a thicker state during the past four decades, generating greater increases in TSOIL. Changes in snow cover have led to changes in the thermal state of the underlying soil, which is strongly dependent on both the magnitude and the timing of changes in snowfall. Simulations of the period 2001-2009 revealed significant differences in the extent of near-surface permafrost, reflecting differences in the model's treatment of meteorology and the soil bottom boundary. Permafrost loss was greater when SND increased in autumn rather than in winter, due to insulation of the soil resulting from early cooling. Simulations revealed that TSOIL tended to increase over most of the pan-Arctic from 1901 to 2009, and that this increase was significant in northern regions, especially in northeastern Siberia where SND is responsible for 50 % or more of the changes in TSOIL at a depth of 3.6 m. In the same region, ALT also increased at a rate of approximately 2.3 cm per decade. The most sensitive response of ALT to changes in SND appeared in the southern boundary regions of permafrost, in contrast to permafrost temperatures within the 60°N-80°N region, which were more sensitive to changes in snow cover. Finally, our model suggests that snow cover contributes to the warming of permafrost in northern regions and could play a more important role

  3. 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.

  4. 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.

  5. Extension of operational regime in high-temperature plasmas and effect of ECRH on ion thermal transport in the LHD

    NASA Astrophysics Data System (ADS)

    Takahashi, H.; Nagaoka, K.; Murakami, S.; Osakabe, M.; Nakano, H.; Ida, K.; Tsujimura, T. I.; Kubo, S.; Kobayashi, T.; Tanaka, K.; Seki, R.; Takeiri, Y.; Yokoyama, M.; Maeta, S.; Nakata, M.; Yoshinuma, M.; Yamada, I.; Yasuhara, R.; Ido, T.; Shimizu, A.; Tsuchiya, H.; Tokuzawa, T.; Goto, M.; Oishi, T.; Morita, S.; Suzuki, C.; Emoto, M.; Tsumori, K.; Ikeda, K.; Kisaki, M.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Makino, R.; Seki, T.; Kasahara, H.; Saito, K.; Kamio, S.; Nagasaki, K.; Mutoh, T.; Kaneko, O.; Morisaki, T.; the LHD Experiment Group

    2017-08-01

    A simultaneous high ion temperature (T i) and high electron temperature (T e) regime was successfully extended due to an optimized heating scenario in the LHD. Such high-temperature plasmas were realized by the simultaneous formation of an electron internal transport barrier (ITB) and an ion ITB by the combination of high power NBI and ECRH. Although the ion thermal confinement was degraded in the plasma core with an increase of T e/T i by the on-axis ECRH, it was found that the ion thermal confinement was improved at the plasma edge. The normalized ion thermal diffusivity {χ\\text{i}}/T\\text{i}1.5 at the plasma edge was reduced by 70%. The improvement of the ion thermal confinement at the edge led to an increase in T i in the entire plasma region, even though the core transport was degraded.

  6. Thermal regime of soils in the atlantic high mountain. The central massiff of Picos de Europa (Spain)

    NASA Astrophysics Data System (ADS)

    Pisabarro, Alfonso; Serrano, Enrique; José González Trueba, Juan; Pellitero, Ramón

    2015-04-01

    The study of ground thermal regime has got large interest because determine significant geomorphological processes, particularly in the high mountain where do not exist vegetal cover on the ground. Picos de Europa massifs is located in the North of the Iberian Peninsula (43°18'to 43°7'N and 5°7' to 4°36'W, Spain). It is a wet and temperate high mountain environment characterized by the presence of calcareous rock, featured by karst processes and Pleistocene glaciers. The aim of this work is analyse the thermal behavior of ground along the year at different altitudes and know limits of ice presence on the ground to differentiate stages without ice, with seasonal ice or potential permafrost. Temperature data were obtained by 12 thermal micro sensors I-Bottom and UTL-Geotest AG data-logger with centesimal accuracy undertaken to 5-10 cm depth. Micro sensors distribution vary between 1110 and 2535 m a.s.l. exploiting the sites with best topoclimatic terms in order to obtain the coldest records like ancient glaciers. The period of recordings was 2003-2007. It was enough to obtain parameters like annual ground medium temperatures, freeze and thaw cycles, freeze index or number of months with temperatures below zero. Thermal phases on the ground have been obtained. The thermal regime varies according topoclimatic conditions in the sites above cryonival stage (above 1800 m a.s.l.). It was possible to determinate four phases; highest temperatures, autumn change, winter isotherm and melt. The winter isotherm is the longest phase (6-10 months) due to the intense snowfall. During this period do not exist thermal daily amplitude and the minimum and maximum temperatures are similar; always into the interval (-0.1°C to 0°C). However there are sites where the cold is enough to break the wintry isotherm during several days with records around -6°C. The days with freeze and thaw cycles are scarce and concentrated in autumn during periods without snow cover. Results show that

  7. 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.

  8. 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.

  9. Thermal Regime and Meteorological Parameters Monitoring in Alpine Permafrost Rockwalls: the Aiguille du Midi

    NASA Astrophysics Data System (ADS)

    Morra di Cella, U.; Cremonese, E.; Deline, P.; Gruber, S.; Pogliotti, P.; Ravanel, L.

    2009-04-01

    During the last decades the alpine region has revealed to be extremely sensitive to ongoing increasing temperatures and permafrost has been identified as one of six cryospheric indicators of global climate change. In high-mountain regions the permafrost evidences are scarse and punctual, while its occurrence is wide and its distribution is mainly controlled by complex topography and ground cover condition. In such environment, steep bedrock slopes are abundant and contain a significant proportion of permafrost whose thermal response is very fast compared to permafrost in gentle morphology because of its less amount of ice content. Due to logistical problems like accessibility, costs, weather conditions, etc..., monitoring sites in such environments are few, while an increase of measurements of rockwall temperature and system energy balance is fundamental for the calibration and validation of both physical and statistical permafrost models. Started in the framework of the French-Italian project PERMAdataROC (www.fondazionemontagnasicura.org/multimedia/permadataroc/) and presently developped within the EU co-funded project PermaNET (www.permanet-alpinespace.eu), several monitoring sites have been equipped during the last years in the Western Alps from a collaboration of Swiss, French and Italian researchers, with the aim to cover the widest range of climatic, topographic, morphological and geological conditions. In such network, the Aiguille du Midì can be considered one of the most advanced site in high-mountain permafrost research thanks to the convergence of several instrumental approaches, but also a "cooperation laboratory" among different research groups. The site has been choosen because of its elevation, aspects variability, steep slopes and accessibility all over the year. In details, ARPA Valle d'Aosta in collaboration with University of Zurich started in 2006 the monitoring of rockwall thermal regimes and of some meteorological parameters on the different

  10. Thermal habitat constraints on zooplankton species associated with Atlantic cod (Gadus morhua) on the US Northeast Continental Shelf

    NASA Astrophysics Data System (ADS)

    Friedland, Kevin D.; Kane, Joe; Hare, Jonathan A.; Lough, R. Gregory; Fratantoni, Paula S.; Fogarty, Michael J.; Nye, Janet A.

    2013-09-01

    The US Northeast Continental Shelf is experiencing a period of increasing temperature levels and range, which impacts the quantity of thermal habitats within the ecosystem. With increasing temperatures, the amount of warmer, surface water thermal habitats (16-27 °C) has increased while there has been a reciprocal decline in cooler water habitats (5-15 °C). These cooler water habitats are the most abundant and comprise the core habitats of the ecosystem. The coldest thermal habitats (1-4 °C), however, have increased slightly in amount or have remained constant, reflecting a discontinuity in the progression of warming along a latitudinal gradient. This discontinuity may be the result of recent changes in the circulation of water masses in the northern Gulf of Maine, potentially associated with the Labrador Current. The contraction of core thermal habitats appears to have had biological consequences on multiple trophic levels. In particular, two zooplankton species associated with the larval feeding of Atlantic cod, Gadus morhua, have declined in abundance in the same areas where cod populations have exhibited continually poor recruitment. The zooplankton species group Pseudocalanus spp., which is associated with winter-spawning cod, has declined on Georges Bank and in the Eastern Gulf of Maine. The zooplankton Centropages typicus has declined in the Gulf of Maine during late summer into fall, potentially affecting spring-spawning cod in that area. These observations are consistent with the hypothesis that portions of the population complex of cod have lower reproductive output due to changes in zooplankton abundance, which we associate with the distribution of temperatures within the ecosystem.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Numerical study of dependence of thermally stimulated currents in disordered solids at step heating regime on initial trap occupancy

    NASA Astrophysics Data System (ADS)

    Tomaszewicz, W.; Grygiel, P.

    2011-04-01

    In the present paper numerical investigation of thermally stimulated currents (TSCs) in disordered solids, measured at step heating regime, is performed. The utilized energy distribution of trapping states is the superposition of exponential and Gaussian distributions. The monomolecular carrier recombination regime is assumed. The resulting set of stiff differential equations governing TSCs is solved with the use of Gear's procedure. The calculations are made for several carrier generation and recombination rates. The TSC curves are next analyzed by the methods developed in previous papers and the calculated trap distributions are compared with the input distributions. It is concluded that the methods have satisfactory accuracy solely in the cases of week carrier retrapping or small trap occupancy.

  20. Morphology control on hyporheic zone hydrodynamics: implication on redox and thermal regimes (Invited)

    NASA Astrophysics Data System (ADS)

    Marzadri, A.; Tonina, D.; Bellin, A.

    2013-12-01

    . Through this parameter we are able to define two dimensionless Damköhler numbers DaO, and DaT, which relate river morphology, through τ50, with the redox and the thermal regime within the hyporheic zone, respectively. In particular, DaO quantifies the biogeochemical status of the hyporheic zone through the ratio between τ50 and the time needed to consume dissolved oxygen to a prescribed threshold concentration (τlim), below which reductive reactions are activated: (DaO = τ50/τlim). In addition, DaT quantifies the importance of the temperature daily oscillations of the stream water on hyporheic environment through the ratio between τ50, and the time limit for which the amplitude of daily temperature oscillations of hyporheic waters are 1/e of those at the stream water. Our analysis showed that contrary to popular models such as transient storage, our approach is able to capture the relationship between moments recently proposed by González-Pinzón et al., (2013) in a study analyzing a large dataset of experimental BTCs. Moreover, through the Damköhler numbers we are able to define a new theoretical framework for scaling results at both the morphological-unit and stream-reach scales. González-Pinzón, R., R. Haggerty, and M. Dentz (2013), Scaling and predicting solute transport processes in streams, Water Resour. Res., 49, doi:10.1002/wrcr.20280.

  1. The growth of shrubs on high Arctic tundra at Bylot Island: impact on snow physical properties and permafrost thermal regime

    NASA Astrophysics Data System (ADS)

    Domine, Florent; Barrere, Mathieu; Morin, Samuel

    2016-12-01

    With climate warming, shrubs have been observed to grow on Arctic tundra. Their presence is known to increase snow height and is expected to increase the thermal insulating effect of the snowpack. An important consequence would be the warming of the ground, which will accelerate permafrost thaw, providing an important positive feedback to warming. At Bylot Island (73° N, 80° W) in the Canadian high Arctic where bushes of willows (Salix richardsonii Hook) are growing, we have observed the snow stratigraphy and measured the vertical profiles of snow density, thermal conductivity and specific surface area (SSA) in over 20 sites of high Arctic tundra and in willow bushes 20 to 40 cm high. We find that shrubs increase snow height, but only up to their own height. In shrubs, snow density, thermal conductivity and SSA are all significantly lower than on herb tundra. In shrubs, depth hoar which has a low thermal conductivity was observed to grow up to shrub height, while on herb tundra, depth hoar only developed to 5 to 10 cm high. The thermal resistance of the snowpack was in general higher in shrubs than on herb tundra. More signs of melting were observed in shrubs, presumably because stems absorb radiation and provide hotspots that initiate melting. When melting was extensive, thermal conductivity was increased and thermal resistance was reduced, counteracting the observed effect of shrubs in the absence of melting. Simulations of the effect of shrubs on snow properties and on the ground thermal regime were made with the Crocus snow physics model and the ISBA (Interactions between Soil-Biosphere-Atmosphere) land surface scheme, driven by in situ and reanalysis meteorological data. These simulations did not take into account the summer impact of shrubs. They predict that the ground at 5 cm depth at Bylot Island during the 2014-2015 winter would be up to 13 °C warmer in the presence of shrubs. Such warming may however be mitigated by summer effects.

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

    Treesearch

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

    2004-01-01

    The effects of constant (12, 18, and 24°C) and cyclical (daily variation of 15–21 and 12–24 °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°C) and more variable daily temperatures (i.e., 12–24°C daily cycle) negatively...

  3. Thermally induced phase changes, lateral heterogeneity of the mantle, continental roots, and deep slab anomalies

    NASA Technical Reports Server (NTRS)

    Anderson, Don L.

    1987-01-01

    Factors which influence the lateral heterogeneity in density and seismic velocity with depth in the upper earth mantle are discussed. It is emphasized that most of the increases in density and seismic velocity with depth are caused by pressure-induced solid-solid phase changes in the high-density high-velocity phases of mineral assemblage, due to variations in temperature. In particular, the ilmenite form of MgSiO3 and the gamma-spinel form of Mg2SiO4 have broad stability fields in cold mantle and are not stable in hotter mantle. It is emphasized that the density and velocity anomalies associated with temperature-induced phase changes in mineral assemblage must be taken into account in the thermal models of the slabs; when these effects are accounted for, the geoid and seismic anomalies associated with subducted slabs are consistent with slab confinement to the upper mantle and with layered models of mantle convection.

  4. 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.

  5. 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.

  6. Nitrogen isotopes in thermal fluids of a forearc region (Jalisco Block, Mexico): Evidence for heavy nitrogen from continental crust

    NASA Astrophysics Data System (ADS)

    Inguaggiato, S.; Taran, Y.; Grassa, F.; Capasso, G.; Favara, R.; Varley, N.; Faber, E.

    2004-12-01

    The Jalisco Block (JB) is a geologically and tectonically complex part of northwestern Mexico characterized by active subduction-type volcanism, rifting, and old stable structures. Thermal springs and groups of springs are widely distributed over JB. Bubbling gas from seven thermal springs located within different tectonic environments of the JB was analyzed for He, 20Ne, and N2 concentrations and δ15N ratios. All gases are N2-dominant (>84%) with the exception of one sample (Rió Purificación), which has a significant CH4 content (about 50%). All collected gas samples are relatively high in He, up to 1500 ppm vol and with 3He/4He values ranging from 0.6 to 4.5 Ra. All measured nitrogen isotope ratios are heavier than air with δ15N values ranging from 0.5 to 5.0‰. The relative N2 excess with respect to air-saturated water computed on the basis of N2 and 20Ne contents indicates the contribution of a nonatmospheric N2 source. All the samples show a good correlation between δ15N and the relative excess of N2 with δ15N ˜ +5.3‰ for the maximum N2 excess of 100%. Due to a presumed lack of seafloor sediment involved in the subduction process, such a δ15N positive value seems to reflect the addition to the fluids of a heavy nitrogen originating from metamorphism processes of rocks occurring within the overlying continental crust.

  7. Progeny of Osmia lignaria from distinct regions differ in developmental phenology and survival under a common thermal regime.

    PubMed

    Pitts-Singer, Theresa L; Cane, James H; Trostle, Glen

    2014-08-01

    Many insects, including some bees, have extensive subcontinental distributions that can differ in climatic conditions. Within and beyond these distributions, humans intentionally transport beneficial insects, including bees, to non-natal geographic locations. Insects also are experiencing unprecedented climatic change in their resident localities. For solitary bees, we know very little about the adaptive plasticity and geographic variation in developmental physiology that accommodates the different climates experienced within distributional ranges. Osmia lignaria Say (Hymenoptera: Megachilidae) is a widely distributed North American spring-emerging bee being developed as a managed pollinator for tree fruit crops, including almonds. We examined the development and survival of O. lignaria progeny that were descended from populations sourced from southern California, western Washington, and northern Utah, and then were reared together under an hourly and weekly temperature regime simulating those of a California almond-growing region. We found that developmental physiologies of Washington and Utah progeny were generally similar. However, California progeny developed slower, were more metabolically active, and survived better under California conditions than did populations native to regions at higher latitudes. Regardless of geographic origin, cocooned adults managed under prescribed thermal regimes emerged faster and lived longer after wintering. Progeny of parents from different regions exhibited some acclimatory plasticity in developmental phenologies to a novel climatic regime, but overall their responses reflected their geographic origins. This outcome is consistent with their developmental phenologies being largely heritable adaptations to regional climates.

  8. Millisecond dynamics of thermal expansion of mechanically controllable break junction electrodes studied in the tunneling regime

    NASA Astrophysics Data System (ADS)

    Kolesnychenko, O. Yu.; Toonen, A. J.; Shklyarevskii, O. I.; van Kempen, H.

    2001-10-01

    The thermal expansion dynamics of W, Pt-Ir, and Au mechanically controllable break junction electrodes was studied in the millisecond range. By measuring a transient tunnel current as a function of time, we found that, at low temperatures, the electrode elongation Δs˜t1/2 due to the large values of thermal diffusivity of metals. The magnitude of Δs varies in direct proportion to the power P dissipated in the electrodes.

  9. Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

    NASA Astrophysics Data System (ADS)

    Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; Longtin, Jon

    2017-09-01

    Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). A part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on the beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. As a result, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. In addition, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.

  10. Thermal considerations in the cryogenic regime for the BNL double ridge higher order mode waveguide

    DOE PAGES

    Ravikumar, Dhananjay K.; Than, Yatming; Xu, Wencan; ...

    2017-09-06

    Brookhaven National Laboratory (BNL) has proposed to build an electron ion collider (EIC) as an upgrade to the existing Relativistic Heavy Ion Collider (RHIC). One part of the new design is to use superconducting radio frequency (SRF) cavities for acceleration, which sit in a bath of superfluid helium at a temperature of 2 K. SRF cavities designed for the BNL EIC create a standing electromagnetic wave, oscillating at a fundamental frequency of 647 MHz. Interaction of the charged particle beam with the EM field in the cavity creates higher order modes (HOM) of oscillation which have adverse effects on themore » beam when allowed to propagate down the beam tube. HOM waveguides are thus designed to remove this excess energy which is then damped at room temperature. Thus, these waveguides provide a direct thermal link between room temperature and the superconducting cavities adding a static thermal load. The EM wave propagating through the warmer sections of the waveguide creates an additional dynamic thermal load. This study calculates these thermal loads, concluding that the dynamic load is small in comparison to the static load. Temperature distributions are mapped on the waveguide and the number of heat intercepts required to efficiently manage thermal loads have been determined. Additonally, a thermal radiation study has been performed and it is found that this contribution is around three orders of magnitude smaller than the static conduction and dynamic loads.« less

  11. Early Life-Stage Responses of a Eurythemal Estuarine Fish, Mummichog (Fundulus hetereoclitus) to Fixed and Fluctuating Thermal Regimes

    NASA Astrophysics Data System (ADS)

    Shaifer, J.

    2016-02-01

    The mummichog (Fundulus hetereoclitus) is an intertidal spawning fish that ranges from the Gulf of St. Lawrence to northeastern Florida. A notoriously hardy species, adults can tolerate a wide range of temperature typical of inshore, estuarine waters. This experiment assessed how a wide range of constant and fluctuating temperatures affect the survival, development, and condition of embryos and young larvae. Captive adults were provided nightly with spawning substrates that were inspected each morning for fertilized eggs. Young ( 8 hr post-fertilization) embryos (N = 25 per population) were assigned to either one of a wide range of constant temperatures (8 to 34 °C) generated by a thermal gradient block (TGB), or to one of 10 daily oscillating temperature regimes that spanned the TGB's mid temperature (21 °C). Water was changed and populations inspected for mortalities and hatching at 12-hr intervals. Hatch dates and mortalities were recorded, and larvae were either anesthetized and measured for size by analyzing digital images, or evaluated for persistence in a food-free environment. Mummichog embryos withstood all but the coldest constant regimes and the entire range of fluctuating ones although age at hatching varied substantially within and among experimental populations. Embryos incubated at warmer temperatures hatched out earlier and at somewhat smaller sizes than those experiencing cooler temperatures. Temperatures experienced by embryos had an inverse effect on persistence of larvae relying on yolk nutrition alone. Mummichog exhibited an especially plastic response to thermal challenges which reflects the highly variable nursery habitat used by this species.

  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. The Influence of Seasonal Climatic Parameters on the Permafrost Thermal Regime in West Siberia

    NASA Astrophysics Data System (ADS)

    Popova, V. V.; Shmakin, A. B.

    2009-12-01

    Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analyzed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1-2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5-10m depth were correlated with spring air temperatures in the current and preceding 1-2 years. The weather regime during the preceding 1-2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasizing the importance of analyses at short temporal scales and for individual terrain units.

  14. Active layer and permafrost thermal regime in a patterned ground soil in Maritime Antarctica, and relationship with climate variability models.

    PubMed

    Chaves, D A; Lyra, G B; Francelino, M R; Silva, Ldb; Thomazini, A; Schaefer, Cegr

    2017-04-15

    Permafrost and active layer studies are important to understand and predict regional climate changes. The objectives of this work were: i) to characterize the soil thermal regime (active layer thickness and permafrost formation) and its interannual variability and ii) to evaluate the influence of different climate variability modes to the observed soil thermal regime in a patterned ground soil in Maritime Antarctica. The study was carried out at Keller Peninsula, King George Island, Maritime Antarctica. Six soil temperatures probes were installed at different depths (10, 30 and 80cm) in the polygon center (Tc) and border (Tb) of a patterned ground soil. We applied cross-correlation analysis and standardized series were related to the Antarctic Oscillation Index (AAO). The estimated active layer thickness was approximately 0.75cm in the polygon border and 0.64cm in the center, indicating the presence of permafrost (within 80cm). Results indicate that summer and winter temperatures are becoming colder and warmer, respectively. Considering similar active layer thickness, the polygon border presented greater thawing days, resulting in greater vulnerability to warming, cooling faster than the center, due to its lower volumetric heat capacity (Cs). Cross-correlation analysis indicated statistically significant delay of 1day (at 10cm depth) in the polygon center, and 5days (at 80cm depth) for the thermal response between atmosphere and soil. Air temperature showed a delay of 5months with the climate variability models. The influence of southern winds from high latitudes, in the south facing slopes, favored freeze in the upper soil layers, and also contributed to keep permafrost closer to the surface. The observed cooling trend is linked to the regional climate variability modes influenced by atmospheric circulation, although longer monitoring period is required to reach a more precise scenario.

  15. 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

  16. Sensitivity analysis of a variability in rock thermal conductivity concerning implications on the thermal evolution of the Brazilian South Atlantic passive continental margin

    NASA Astrophysics Data System (ADS)

    Stippich, Christian; Krob, Florian; Glasmacher, Ulrich Anton; Hackspacher, Peter Christian

    2017-04-01

    The aim of the research is to quantify the long-term evolution of the western South Atlantic passive continental margin (SAPCM) in SE-Brazil. Excellent onshore outcrop conditions and extensive pre-rift to post-rift archives between São Paulo and Laguna allow a high precision quantification of exhumation, and rock uplift rates, influencing physical parameters, long-term acting forces, and process-response systems. The research integrates published (Karl et al., 2013) and partly published thermochronological data from Brazil, and test lately published new concepts on causes of long-term landscape and lithospheric evolution in southern Brazil. Six distinct lithospheric blocks (Laguna, Florianópolis, Curitiba, Ilha Comprida, Peruibe and Santos), which are separated by fracture zones (Karl et al., 2013) are characterized by individual thermochronological age spectra. Furthermore, the thermal evolution derived by numerical modeling indicates variable post-rift exhumation histories of these blocks. In this context, we will provide information on the causes for the complex exhumation history of the Florianópolis, and adjacent blocks. Following up on our latest publication (Braun et al., 2016) regarding the effect of variability in rock thermal conductivity on exhumation rate estimates we performed a sensitivity analysis to quantify the effect of a differentiated lithospheric crust on the thermal evolution of the Florianópolis block versus exhumation rates estimated from modelling a lithospheric uniform crustal block. The long-term landscape evolution models with process rates were computed with the software code PECUBE (Braun, 2003; Braun et al., 2012). Testing model solutions obtained for a multidimensional parameter space against the real thermochronological and geomorphological data set, the most likely combinations of parameters, values, and rates can be constrained. References Braun, J., 2003. Pecube: A new finite element code to solve the 3D heat transport

  17. 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

  18. The thermal regime of the Campi Flegrei magmatic system reconstructed through 3D numerical simulations

    SciTech Connect

    Di Renzo, Valeria; Wohletz, Kenneth; Civetta, Lucia; Moretti, Roberto; Orsi, Giovanni; Gasparini, Paolo

    2016-11-11

    In this paper, we illustrate a quantitative conductive/convective thermal model incorporating a wide range of geophysical, petrological, geological, geochemical and isotopical observations that constrain the thermal evolution and present state of the Campi Flegrei caldera (CFc) magmatic system. The proposed model has been computed on the basis of the current knowledge of: (1) the volcanic and magmatic history of the volcano over the last 44 ka, (2) its underlying crustal structure, and (3) the physical properties of the erupted magmas. 3D numerical simulations of heat conduction and convection within heterogeneous rock/magma materials with evolving heat sources and boundary conditions that simulate magma rise from a deep (≥ 8 km depth) to shallow (2–6 km) reservoirs, magma chamber formation, magma extrusion, caldera collapse, and intra-caldera hydrothermal convection, have been carried out. The evolution of the CFc magmatic system through time has been simulated through different steps related to its changes in terms of depth, location and size of magma reservoirs and their replenishment. The thermal modeling results show that both heat conduction and convection have played an important role in the CFc thermal evolution, although with different timing. Finally, the simulated present heat distribution is in agreement with the measured geothermal profiles (Agip, 1987), reproduces the thermal gradient peaks at the CFc margins in correspondence to the anomalies in surface gradients (Corrado et al., 1998), and suggests temperatures of 700 °C at depth of 4 km in the central portion of the caldera, in agreement with the estimated temperature for the brittle-ductile transition (Hill, 1992).

  19. The thermal regime of the Campi Flegrei magmatic system reconstructed through 3D numerical simulations

    DOE PAGES

    Di Renzo, Valeria; Wohletz, Kenneth; Civetta, Lucia; ...

    2016-11-11

    In this paper, we illustrate a quantitative conductive/convective thermal model incorporating a wide range of geophysical, petrological, geological, geochemical and isotopical observations that constrain the thermal evolution and present state of the Campi Flegrei caldera (CFc) magmatic system. The proposed model has been computed on the basis of the current knowledge of: (1) the volcanic and magmatic history of the volcano over the last 44 ka, (2) its underlying crustal structure, and (3) the physical properties of the erupted magmas. 3D numerical simulations of heat conduction and convection within heterogeneous rock/magma materials with evolving heat sources and boundary conditions thatmore » simulate magma rise from a deep (≥ 8 km depth) to shallow (2–6 km) reservoirs, magma chamber formation, magma extrusion, caldera collapse, and intra-caldera hydrothermal convection, have been carried out. The evolution of the CFc magmatic system through time has been simulated through different steps related to its changes in terms of depth, location and size of magma reservoirs and their replenishment. The thermal modeling results show that both heat conduction and convection have played an important role in the CFc thermal evolution, although with different timing. Finally, the simulated present heat distribution is in agreement with the measured geothermal profiles (Agip, 1987), reproduces the thermal gradient peaks at the CFc margins in correspondence to the anomalies in surface gradients (Corrado et al., 1998), and suggests temperatures of 700 °C at depth of 4 km in the central portion of the caldera, in agreement with the estimated temperature for the brittle-ductile transition (Hill, 1992).« less

  20. The thermal regime of the Campi Flegrei magmatic system reconstructed through 3D numerical simulations

    NASA Astrophysics Data System (ADS)

    Di Renzo, Valeria; Wohletz, Kenneth; Civetta, Lucia; Moretti, Roberto; Orsi, Giovanni; Gasparini, Paolo

    2016-12-01

    We illustrate a quantitative conductive/convective thermal model incorporating a wide range of geophysical, petrological, geological, geochemical and isotopical observations that constrain the thermal evolution and present state of the Campi Flegrei caldera (CFc) magmatic system. The proposed model has been computed on the basis of the current knowledge of: (1) the volcanic and magmatic history of the volcano over the last 44 ka, (2) its underlying crustal structure, and (3) the physical properties of the erupted magmas. 3D numerical simulations of heat conduction and convection within heterogeneous rock/magma materials with evolving heat sources and boundary conditions that simulate magma rise from a deep (≥ 8 km depth) to shallow (2-6 km) reservoirs, magma chamber formation, magma extrusion, caldera collapse, and intra-caldera hydrothermal convection, have been carried out. The evolution of the CFc magmatic system through time has been simulated through different steps related to its changes in terms of depth, location and size of magma reservoirs and their replenishment. The thermal modeling results show that both heat conduction and convection have played an important role in the CFc thermal evolution, although with different timing. The simulated present heat distribution is in agreement with the measured geothermal profiles (Agip, 1987), reproduces the thermal gradient peaks at the CFc margins in correspondence to the anomalies in surface gradients (Corrado et al., 1998), and suggests temperatures of 700 °C at depth of 4 km in the central portion of the caldera, in agreement with the estimated temperature for the brittle-ductile transition (Hill, 1992).

  1. The lithosphere thermal regime across the Dead Sea transform in Israel and Jordan

    NASA Astrophysics Data System (ADS)

    Förster, A.; Förster, H.-J.; Stromeyer, D.; Sobolev, S. V.; Oberhänsli, R.

    2003-04-01

    Reevaluation of thermal data (T-logs, thermal conductivity) from the area of the DESERT seismic refraction/reflection profiles in Israel shows that only part of the published heat-flow data correctly portrays the terrestrial heat flow. Taking into account the distortion factors on thermal conditions and discarding shallow (<100 m) boreholes from the database, nine heat-flow values remained yielding an average of 62±7.5 mW/m^2. We suggest that this value more closely approximates the terrestrial heat flow in this part of the African plate than previous values published for Israel, which are considerably lower (52±17.2 mW/m^2 and 40 mW/m^2, resp.). The new average is in good agreement with a surface heat-flow of preliminarily 60 mW/m^2 obtained from a 960-m deep borehole in southeastern Jordan. This well-constrained value is considerably higher than those proposed to represent the overall heat flow in this part of the African plate including Syria and Saudi Arabia (40--45 mW/m^2). Based on (1) newly acquainted data for Jordan on U-Th-K abundances from Pan-African basement rocks and xenoliths entrained in Cenozoic basalts, which allow to infer the radiogenic heat production in the Jordanian crust, (2) respective literature values from Israel, and (3) new seismic data from the DESERT project, the structure and composition of the crust are redefined, and general thermal models for the lithosphere subplates separated by the Dead Sea Transform (DST) are calculated. Considering the temperature and pressure dependence of rock thermal conductivity and present-day surface heat flow, the steady-state geotherm for the Jordan lower crust/upper mantle is higher than in Israel, where it is within the envelope of previous geotherms. The modeled heat flow at the crust/mantle boundary is similar on both sides of the DST and amounts to 30 mW/m^2. However, the xenolith-derived P-T estimates for Israel (close to the DST) and Jordan (not only restricted to the DST) do not meet these

  2. Thermal regimes in impact melts and the petrology of the Apollo 17 Station 6 boulder

    NASA Technical Reports Server (NTRS)

    Simonds, C. H.

    1975-01-01

    A progress report is presented on the petrologic study of the Station 6 boulder, taking into account the implications of its petrographic and geochemical studies to the understanding of the processes of formation and crystallization of impact melts. The interpretation of the data from the boulder suggests processes that appear reasonable for a petrogenetic model of impact events large enough to produce a layer of melt a kilometer or more wide and at most a few tens of meters thick. A summary of the model is presented. The primary difference between the new model and the previous models of Warner et al. (1973, 1974) and Simonds et al. (1973, 1974) is that melt and clasts are derived from distinctly different parts of the cratering regime. The cooling is modeled in two steps, first the rapid equilibration between clasts and matrix, and second, the much slower loss of heat to the surroundings.

  3. Roughness as a Route to the Kraichnan Regime in Thermal Convection

    NASA Astrophysics Data System (ADS)

    Toppaladoddi, Srikanth; Succi, Sauro; Wettlaufer, John

    2016-11-01

    We use highly resolved numerical simulations to study turbulent Rayleigh-Bénard convection in a cell with sinusoidally rough upper and lower walls in two dimensions. By varying the wavelength at a fixed amplitude, we find an optimal wavelength for which the Nusselt-Rayleigh scaling relation is (Nu - 1 Ra 0 . 482). This is consistent with (i) the upper bound of Goluskin and Doering (2016) who prove that Nu can grow no faster than O (Ra 1 / 2) as Ra -> ∞ , and thus (ii) the concept that roughness facilitates the attainment of the so-called ultimate regime of Kraichnan (1962). In the limits of very small and very large wavelengths we recover the planar case results, demonstrating how controlling the wall geometry manipulates the interaction between the boundary layers and the core flow.

  4. 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

  5. Characteristics-based methods applied to infinite Prandtl number thermal convection in the hard turbulent regime

    NASA Technical Reports Server (NTRS)

    Malevsky, A. V.; Yuen, D. A.

    1991-01-01

    Characteristics-based methods for the advection-diffusion equation are presented and directly applied to study thermal convection with extremely large Rayleigh number (Ra). It is shown that the operator-splitting method for advection-diffusion problems is very accurate for determining the advected field at extremely high Peclet number (Pe). The technique presented is considered to have great potential for solving advection-dominated problems, while the Langrangian method is more accurate for lower Pe. It is noted that the accuracy of these characteristics-based methods strongly depends on the quality of interpolation. The computational time for the operator-splitting method grows with the number of time steps employed. The Langrangian method was used for simulations of convection at very high Ra, up to 3 x 10 to the 9th, and time-dependent, thermal convection solutions were obtained for infinite Prandtl number.

  6. High power tungstate-crystal Raman laser operating in the strong thermal lensing regime.

    PubMed

    McKay, Aaron; Kitzler, Ondrej; Mildren, Richard P

    2014-01-13

    We report an investigation into a double metal tungstate Raman laser when pumped at elevated average powers. Potassium gadolinium tungstate (KGW) was placed in an external cavity configured for second-Stokes output and pumped at pulse repetition rate of 38 kHz with up to 46 W of average power. For output powers above 3 W, we observe preferential excitation of Hermite-Gaussian transverse modes whose order in the X(1)(') principal direction of the thermal expansion tensor scales linearly with Raman power. We deduce that strong astigmatic thermal lensing is induced in the Raman crystal with a negative component in the X(1)(') direction. At maximum pump power, 8.3 W of output power was obtained at a conversion efficiency of 18%.

  7. 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.

  8. 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

  9. Changes in soil thermal regime lead to substantial shifts in carbon and energy fluxes in drained Arctic tundra

    NASA Astrophysics Data System (ADS)

    Goeckede, M.; Kwon, M. J.; Kittler, F.; Heimann, M.; Zimov, N.; Zimov, S. A.

    2016-12-01

    Climate change impacts in the Arctic will not only depend on future temperature trajectories in this region. In particular, potential shifts in hydrologic regimes, e.g. linked to altered precipitation patterns or changes in topography following permafrost degradation, can dramatically modify ecosystem feedbacks to warming. Here, we analyze how severe drainage affects both biogeochemical and biogeophysical processes within a formerly wet Arctic tundra, with a special focus on the interactions between hydrology and soil temperatures, and related effects on the fluxes of carbon and energy. Our findings are based on year-round observations from a decade-long drainage experiment conducted near Chersky, Northeast Siberia. Through our multi-disciplinary observations we can document that the drainage triggered a suite of secondary changes in ecosystem properties, including e.g. adaptation processes in the vegetation community structure, or shifts in snow cover regime. Most profoundly, a combination of low heat capacity and reduced heat conductivity in dry organic soils lead to warmer soil temperatures near the surface, while deeper soil layers remained colder. These changes in soil thermal regime reduced the contribution of deeper soil layers with older carbon pools to overall ecosystem respiration, as documented through radiocarbon signals. Regarding methane, the observed steeper temperature gradient along the vertical soil profile slowed down methane production in deep layers, while promoting CH4 oxidation near the surface. Taken together, both processes contributed to a reduction in CH4 emissions up to a factor of 20 following drainage. Concerning the energy budget, we observed an intensification of energy transfer to the lower atmosphere, particularly in form of sensible heat, but the reduced energy transfer into deeper soil layers also led to systematically shallower thaw depths. Summarizing, drainage may contribute to slow down decomposition of old carbon from deep

  10. 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

  11. Influence of the Geometric Parameter on the Regimes of Natural Convection and Thermal Surface Radiation in a Closed Parallelepiped

    NASA Astrophysics Data System (ADS)

    Martyushev, S. G.; Miroshnichenko, I. V.; Sheremet, M. A.

    2015-11-01

    We have performed a numerical analysis of the stationary regimes of thermogravitational convection and thermal surface radiation in a closed differentially heated parallelepiped. The mathematical model formulated in dimensionless natural velocity-pressure-temperature variables was realized numerically in the control volume approach. Analysis of the radiative heat exchange was carried out on the basis of the surface radiation approach with the use of the balance method in the Polyak variant. We have obtained three-dimensional temperature and velocity fields, as well as dependences for the mean Nusselt number reflecting the influence of the geometric parameter, the Rayleigh number, and the reduced emissive factor of the walls on the flow structure and the heat transfer.

  12. 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. © 2016 Wiley Periodicals, Inc.

  13. 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.

  14. Steady state model for the thermal regimes of shells of airships and hot air balloons

    NASA Astrophysics Data System (ADS)

    Luchev, Oleg A.

    1992-10-01

    A steady state model of the temperature regime of airships and hot air balloons shells is developed. The model includes three governing equations: the equation of the temperature field of airships or balloons shell, the integral equation for the radiative fluxes on the internal surface of the shell, and the integral equation for the natural convective heat exchange between the shell and the internal gas. In the model the following radiative fluxes on the shell external surface are considered: the direct and the earth reflected solar radiation, the diffuse solar radiation, the infrared radiation of the earth surface and that of the atmosphere. For the calculations of the infrared external radiation the model of the plane layer of the atmosphere is used. The convective heat transfer on the external surface of the shell is considered for the cases of the forced and the natural convection. To solve the mentioned set of the equations the numerical iterative procedure is developed. The model and the numerical procedure are used for the simulation study of the temperature fields of an airship shell under the forced and the natural convective heat transfer.

  15. Roughness as a Route to the Ultimate Regime of Thermal Convection.

    PubMed

    Toppaladoddi, Srikanth; Succi, Sauro; Wettlaufer, John S

    2017-02-17

    We use highly resolved numerical simulations to study turbulent Rayleigh-Bénard convection in a cell with sinusoidally rough upper and lower surfaces in two dimensions for Pr=1 and Ra=[4×10^{6},3×10^{9}]. By varying the wavelength λ at a fixed amplitude, we find an optimal wavelength λ_{opt} for which the Nusselt-Rayleigh scaling relation is (Nu-1∝Ra^{0.483}), maximizing the heat flux. This is consistent with the upper bound of Goluskin and Doering [J. Fluid Mech. 804, 370 (2016)JFLSA70022-112010.1017/jfm.2016.528] who prove that Nu can grow no faster than O(Ra^{1/2}) as Ra→∞, and thus with the concept that roughness facilitates the attainment of the so-called ultimate regime. Our data nearly achieve the largest growth rate permitted by the bound. When λ≪λ_{opt} and λ≫λ_{opt}, the planar case is recovered, demonstrating how controlling the wall geometry manipulates the interaction between the boundary layers and the core flow. Finally, for each Ra, we choose the maximum Nu among all λ, thus optimizing over all λ, to find Nu_{opt}-1=0.01×Ra^{0.444}.

  16. 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.

  17. Roughness as a Route to the Ultimate Regime of Thermal Convection

    NASA Astrophysics Data System (ADS)

    Toppaladoddi, Srikanth; Succi, Sauro; Wettlaufer, John S.

    2017-02-01

    We use highly resolved numerical simulations to study turbulent Rayleigh-Bénard convection in a cell with sinusoidally rough upper and lower surfaces in two dimensions for Pr =1 and Ra =[4 ×1 06,3 ×1 09] . By varying the wavelength λ at a fixed amplitude, we find an optimal wavelength λopt for which the Nusselt-Rayleigh scaling relation is (Nu -1 ∝Ra0.483) , maximizing the heat flux. This is consistent with the upper bound of Goluskin and Doering [J. Fluid Mech. 804, 370 (2016), 10.1017/jfm.2016.528] who prove that Nu can grow no faster than O (Ra1 /2) as Ra →∞ , and thus with the concept that roughness facilitates the attainment of the so-called ultimate regime. Our data nearly achieve the largest growth rate permitted by the bound. When λ ≪λopt and λ ≫λopt , the planar case is recovered, demonstrating how controlling the wall geometry manipulates the interaction between the boundary layers and the core flow. Finally, for each Ra, we choose the maximum Nu among all λ , thus optimizing over all λ , to find Nuopt-1 =0.01 ×Ra0.444.

  18. Convective Heat Transfer in Bulk- and Boundary-Dominated Regimes in Turbulent Thermal Convection

    NASA Astrophysics Data System (ADS)

    Wei, Ping; Ni, Rui; Zhao, Xiao-Zheng; Xia, Ke-Qing

    2010-11-01

    We report Nusselt number measurements in Rayleigh-B'enard convection systems with modified boundary conditions and over the range of the Rayleigh number (Ra) spanning from 3x10^8 to 8x10^9 and with the Prandtl number Pr ˜4.3. These measurements were made in three convection cells: (1) both the top and bottom plates of the cell have plat smooth surface; (2) the top plate has a flat smooth surface while the bottom plate has a rough surface in the form of regularly-arrayed pyramids; and (3) the top plate is rough as in (2) but the bottom plate is smooth. All these cells have cylindrical shape with aspect ratio one. The experimental results suggest that the Nu ˜Ra relationship can be represented by the combination of two power laws, corresponding to the bulk-dominant regime (exponent = 1/2) and boundary layer dominant one (exponent =1/4) of the Grossmann-Lohse model. The behaviors of the coefficients of the two power laws suggest that the roughness of the plate can enhance the contribution of bulk and push the system to change from the boundary dominant state to bulk dominant state.

  19. Mapping and modelling of polythermal glacier structure in a meltwater-dominated thermal regime

    NASA Astrophysics Data System (ADS)

    Wilson, N.; Flowers, G. E.; Mingo, L.

    2012-12-01

    We have mapped zones of cold and temperate ice within two small polythermal glaciers in the Saint Elias Mountains of Yukon, Canada using ice-penetrating radar at multiple frequencies. Temperature measurements from instrumented boreholes provide validation of the radar data interpretation. Both glaciers exhibit temperate accumulation zones and cold termini indicating that accumulation zone entrapment and refreezing of meltwater constitute a primary heat source. When forced with a modern climate, a two-dimensional thermomechanically-coupled model based on a first-order momentum balance and an enthalpy method reproduces major features of the observations along the central flowband, such as the arrangement of and the approximate transition between cold and temperate ice. Concentrated rates of strain heating resulting from basal sliding provide a sufficient mechanism for explaining observed lateral heterogeneity in thermal structure. Meltwater entrapment serves as a direct connection between climate and thermal structure. Numerical experiments performed on a synthetic glacier geometry with a range of climatic conditions comparable to the study site reveal that similar glaciers in which meltwater entrapment is the dominant heat source are likely to experience declining temperate ice fractions in a warming climate.

  20. Shallow temperatures and thermal regime in the hydrocarbon province of Tierra del Fuego

    SciTech Connect

    Zielinski, G.W.; Bruchhausen, P.M.

    1983-01-01

    A suite of shallow (<2 m deep) thermal measurements across the San Sebastian oil and gas field, northeastern Tierra del Fuego, indicates at least a 200 mWm/sup -2/ (5 HFU) thermal anomaly over the field. The anomaly appears to be of subsurface origin and, due to its magnitude, must be caused by a localized discharge of deep ground water. A single published heat flow value and deep bottom hole temperature data for the area suggest a regional heat flow that is at least 20 mWm/sup -2/ (0.5 HFU) higher than the world average for similar tectonic provinces (postPrecambrian non-orogenic). Maturation level estimates based on the heat flow and burial history of sediments suggest considerable lateral migration (at least 100 km) of hydrocarbons from deeper in the Magellan basin. From estimates of the timing of possible oil generation, minimum average migration velocity is within 1 or 2 orders of magnitude of the ground water velocity required to cause the local and regional heat flow anomalies. This suggests that ground water moving from deeper in the Magellan basin might simultaneously transport hydrocarbons and heat to the area. Volume flux estimates require that hydrocarbon concentrations significantly greater than possible via aqueous molecular solution.

  1. Shallow temperatures and thermal regime in the hydrocarbon province of Tierra del Fuego

    SciTech Connect

    Zielinski, G.W.; Bruchhausen, P.M.

    1983-01-01

    A suite of shallow (<2 m deep) thermal measurements across the San Sebastian oil and gas field, northeastern Tierra del Fuego, indicates at least a 200 mWm/sup -2/ (5 HFU) thermal anomaly over the field. The anomaly appears to be of subsurface origin and, due to its magnitude, must be caused by a localized discharge of deep groundwater. A single published heat flow value and deep bottom hole temperature data for the area suggest a regional heat flow that is at least 20 mWm/sup -2/ (0.5 HFU) higher than the world average for similar tectonic provinces (post-Precambrian non-orogenic). Maturation level estimates based on the heat flow and burial history of sediments suggest considerable lateral migration (at least 100 km) of hydrocarbons from deeper in the Magellan basin. From estimates of the timing of possible oil generation, minimum average migration velocity is within 1 or 2 orders of magnitude of the groundwater velocity required to cause the local and regional heat flow anomalies. This suggests that groundwater moving from deeper in the Magellan basin might simultaneously transport hydrocarbons and heat to the area. Volume flux estimates require hydrocarbon concentrations significantly greater than possible via aqueous molecular solution.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. Thermal modelling of a transform-divergent interaction zone, the Demerara Plateau, French Guiana margin: architecture of oceanic and continental crusts

    NASA Astrophysics Data System (ADS)

    Grall, Céline; Marcaillou, Boris; Loncke, Lies; Mercier de Lepinay, Marion; Basile, Christophe; Roest, Walter R.; A. M Van Wees, Jan Diederik; A. P. L Cloetingh, Sierd

    2014-05-01

    The crustal architecture of passive margins is a key to constrain their origin and subsequent evolution, as well as their thermal subsidence. The square shaped continental Demerara Plateau, French Guiana margin, surmounts Central and Equatorial Atlantic oceanic crusts surrounding it. Bounded to the northeast by a WNW-ESE-trending transform fault segment and to both the west and the east by N-S divergent fault segments, the Demerara Plateau is a complex transform-divergent interaction zone. The aim of this study is to refine the crustal architecture of this region as derived from gravity and seismic data, by thermal modelling, and by using surface heat flow data as an additional constraint. Previous studies show that the transform transition domain from continental to oceanic crust occurs across a region of approximately 70-km wide, where the Moho deepens abruptly from 25-27 km beneath the plateau (thinned continental crust), to 11-12 km in the abyssal oceanic domain (3-4 km thick oceanic crust). During the IGUANES cruise (onboard R/V L'Atalante in 2013) 10 surface heat flow measurements crossing the plateau have been carried out. These data are combined with borehole heat flows values around. Measures indicate that surface heat flow values range between 47 and 80 mW/m2 (with an uncertainty on the measurements of ~4mW/m2 on average), and slightly decreases in the continental domain toward the ocean. Preliminary 1D thermal modelling results indicate that these heat flow values are consistent with crustal and sediment thicknesses observed on the Plateau. Along the transform domain, at the transition towards the oceanic crust, heat flow values are lower than model results, if we consider an oceanic crust of more than hundred million years and with a thickness of around 3-4 km. We examine, using a 2D approach, whether this low heat flow could be reasonably accounted for by thermal exchange between oceanic and continental lithospheres.

  7. 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

  8. 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

  9. 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.

  10. Exploratory models of the earth's thermal regime during segregation of the core

    NASA Technical Reports Server (NTRS)

    Davies, G. F.

    1980-01-01

    Some simple exploratory theoretical models of the thermal effects of core segregation have been investigated, assuming an initially homogeneous earth and including convective heat transport through a 'parameterized convection' approximation. The results indicate that either (1) mantle temperatures 30% or more above present values may have resulted from the gravitational energy released during core segregation, (2) the earth retained very little of its accretional energy, (3) core segregation lasted for one billion years or more, or (4) the earth accreted heterogeneously. Option 3 seems to be precluded by terrestrial lead isotope data, and the alternatives each raise substantial questions concerning the mechanics, chemistry, and petrology of the earth's early history. There is no recognized evidence for the early hot phase of option 1, and option 4 implies, among other things, an analogous early hot phase. Although it has not been favored, option 2 may be viable.

  11. Hotsotpots and hot moments; the control of structural heterogeneity on the thermal regime of the peatland soil-atmosphere interface.

    NASA Astrophysics Data System (ADS)

    Leonard, Rhoswen; Moore, Paul; Kettridge, Nicholas; Krause, Stefan; Devito, Kevin; Waddington, James Michael

    2017-04-01

    Peat surface temperature acts as a master variable driving non-linear terrestrial biogeochemical, ecohydrological, and micrometeorological processes, inducing short-lived extremes or spatially isolated events across heterogeneous peatland surfaces. Changes to ecosystem structure such as canopy removal may change the temperature extremes and spatio-temporal location of these non-linear processes. In order to understand the impact of structural disturbances on peat surface thermal regimes, we simulate how different ecosystem structural layers (i.e. tree layer, lower vascular layer, bryophyte layer, micro topography) influence the spatial and temporal variability of peatland surface temperatures on a carbon rich forested peatland system. Simulations of peat temperatures are validated using more than 1.9 million peat surface temperature measurements across a 10 m2 area of peatland under un-disturbed, trees removed, and lower vascular vegetation removed conditions (through the use of Fibre Optic Distributed Temperature Sensing Technology). The simulations of peat temperature using different structural complexity allows us to determine how ecosystem layers may simplify or complicate surface thermal patterns and promote or dampen temperature extremes. Our study provides important insight into spatial and temporal variability in peatland biogeochemical functioning and the production of hot spots or hot moments in peatland carbon storage or export.

  12. 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

  13. 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

  14. 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.

  15. Estimation of the effect of thermal convection and casing on the temperature regime of boreholes: a review

    NASA Astrophysics Data System (ADS)

    Eppelbaum, L. V.; Kutasov, I. M.

    2011-03-01

    In a vertical borehole, free heat convection arises when the temperature gradient equals or exceeds the so-called critical gradient. The critical temperature gradient is expressed through the critical Rayleigh number and depends on two parameters: (a) the ratio of formation (casings) to fluid (gas) conductivities (λf/λ) and (b) the convective parameter of the fluid. Both these parameters depend on the temperature (depth). An empirical equation for the critical Rayleigh number as a function of the ratio λf/λ is suggested. For the 0-100 °C range, empirical equations for convective parameters of water and air are proposed. The analysis of the published results of field investigations in deep boreholes and modelling shows that the temperature disturbances caused by thermal convection do not exceed 0.01-0.05 °C. Thus, in deep wells the temperature deviations due to thermal convection are usually within the accuracy of the temperature surveys. However, due to convection cells the geothermal gradient cannot be determined with sufficient accuracy for short well sections. In shallow boreholes the effect of thermal convection is more essential (up to 3-5 °C). To reduce the effect of convection on the temperature regime in shallow observational wells, it is necessary to reduce the diameter of the wellbores and use well fillers (fluids and gases) with low values of the convective parameters. The field observations and numerical calculations indicate that the distorting effect due to casing pipes is small and its influence is localized to the ends of the pipes, and this effect is independent of time.

  16. Multiscale modeling of binary polymer mixtures: Scale bridging in the athermal and thermal regime

    NASA Astrophysics Data System (ADS)

    McCarty, J.; Guenza, M. G.

    2010-09-01

    Obtaining a rigorous and reliable method for linking computer simulations of polymer blends and composites at different length scales of interest is a highly desirable goal in soft matter physics. In this paper a multiscale modeling procedure is presented for the efficient calculation of the static structural properties of binary homopolymer blends. The procedure combines computer simulations of polymer chains on two different length scales, using a united atom representation for the finer structure and a highly coarse-grained approach on the mesoscale, where chains are represented as soft colloidal particles interacting through an effective potential. A method for combining the structural information by inverse mapping is discussed, allowing for the efficient calculation of partial correlation functions, which are compared with results from full united atom simulations. The structure of several polymer mixtures is obtained in an efficient manner for several mixtures in the homogeneous region of the phase diagram. The method is then extended to incorporate thermal fluctuations through an effective χ parameter. Since the approach is analytical, it is fully transferable to numerous systems.

  17. Specific features of thermal regimes in rectangular laser slabs under steady-state pumping

    SciTech Connect

    Alpat'ev, A N; Smirnov, V A; Shcherbakov, Ivan A

    2010-01-31

    We continue to investigate the phenomena related to smoothing of temperature profiles in rectangular laser slabs and to an increase in the thresholds of their breakdown under optical pumping with variations in the slab optical density [the effect of smoothing of thermooptical inhomogeneities (STOI effect)]. It is found that the STOI effect is observed not only with increasing but also with decreasing optical density if this occurs due to a decrease in the sample thickness. The dependence of the maximum temperature difference inside the slab on its optical density at the instant of its thermal breakdown is calculated. It is shown that the variations in the optical density caused by variations in both the absorption coefficient and geometric dimensions of the slab differently affect the order of occurrence of two undesirable events - destruction of the slab or boiling of cooling water - with increasing pump power. The calculated relationships reveal two optical density regions corresponding to different orders of occurrence of these events. The maximum allowable temperatures in each region are determined. (active media)

  18. Ground surface thermal regime of rock glaciers in the High Tatra Mts., Slovakia

    NASA Astrophysics Data System (ADS)

    Uxa, Tomáš; Mida, Peter

    2017-04-01

    Numerous lobate- or tongue-shaped debris accumulations, mostly interpreted as rock glaciers, have recently been recognized in the High Tatra Mts., Slovakia (49˚ 10' N, 20˚ 08' E). These prominent landforms arise due to creep of voluminous debris-ice mixtures, and as such they are excellent indicators of present or past permafrost existence. Hence rock glaciers are extensively utilized to model the distribution of permafrost in mountain areas. However, commonly applied rules of thumb may not be entirely indicative to discriminate particularly between the inactive (permafrost in disequilibrium with present climate) and relict (without permafrost) rock glaciers, which may substantially complicate permafrost modelling. Accordingly, the information about their thermal state is essential to calibrate and validate regional permafrost models. Limited ground temperature data have been, however, available from the High Tatra Mts. to date and therefore, we bring the updated and enhanced results from the thermal investigations of eleven rock glaciers located in the Slavkovská dolina and Veľká Studená dolina valleys at elevations between 1832 and 2090 m asl. Ground surface temperature (GST) has been continuously monitored at seven rock glaciers between October 2014 and September 2016 using nine Minikin Tie (EMS Brno Inc.) and iButton DS1922L (Maxim Integrated Inc.) loggers with an accuracy of ±0.2 and ±0.5 ˚ C, respectively. In addition, the bottom temperature of snow (BTS) was measured at 306 locations during spring of 2015 and 2016 to map potential permafrost occurrence within all the surveyed rock glaciers and in their immediate surroundings. Mean annual ground surface temperature (MAGST) of the rock glaciers ranged between -1.3 ˚ C and +2.6 ˚ C and averaged +1.0 ˚ C and +0.8 ˚ C in 2014-2015 and 2015-2016, respectively. Two sites continually showed negative MAGST and two other sites were below +0.5 ˚ C and +1.0 ˚ C, respectively. This strongly contrasts with

  19. 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

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

    USDA-ARS?s Scientific Manuscript database

    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...

  1. High resolution characterization of northwest Mediterranean coastal waters thermal regimes: To better understand responses of benthic communities to climate change

    NASA Astrophysics Data System (ADS)

    Bensoussan, Nathaniel; Romano, Jean-Claude; Harmelin, Jean-Georges; Garrabou, Joaquim

    2010-04-01

    In the North West Mediterranean (NWM), mass mortality events (MME) of long-lived benthic species that have occurred over the last two decades have been related to regional warming trend. Gaining robust data sets on thermal regimes is critical to assess conditions to which species have adapted, detect extreme events and critically evaluate biological impacts. High resolution temperature ( T) time series obtained during 1999-2006 from 5 to 40 m depth at four contrasted sites of the NWM were analyzed: Area Marina Protegida de les Illes Medes (NE Spain), Riou (Marseilles, France), Parc National de Port-Cros (France), and Réserve Naturelle de Scandola (Corsica, France). The seasonal pattern showed winter T around 11-13 °C, and summer T mainly around 22-24 °C near surface to 18-20 °C at depth. Stratification dynamics showed recurrent downwellings (>40 m) at Medes, frequent observation (1/3rd of the summer) of deep and cold upwelled waters at Riou, while Scandola exhibited stable summer stratification and highest suprathermoclinal T. Port-Cros showed an intermediate regime that oscillated between Riou and Scandola depending on the occurrence of northern winds. Data distribution study permitted to identify and to characterize 3 large scale positive anomalies concomitant with the mass mortality outbreaks of summers 1999, 2003 and 2006. The analysis of biological surveys on gorgonian populations showed significant impacts during the 3 years with temperature anomalies. Besides the degree of impact showed inter-annual differences which could be related to different T conditions concomitant to mortality events, from slight increase in T extreme of only 1-2 °C over short duration, to lengthened more classical summer conditions. Our results therefore support the hypothesis that shallow NWM populations of long-lived benthic species are living near their upper thermal thresholds. Given actual trends and projections in NWM, the repetition of new MMEs in the next decades is

  2. Continents, supercontinents, mantle thermal mixing, and mantle thermal isolation: Theory, numerical simulations, and laboratory experiments

    NASA Astrophysics Data System (ADS)

    Lenardic, A.; Moresi, L.; Jellinek, A. M.; O'Neill, C. J.; Cooper, C. M.; Lee, C. T.

    2011-10-01

    Super-continental insulation refers to an increase in mantle temperature below a supercontinent due to the heat transfer inefficiency of thick, stagnant continental lithosphere relative to thinner, subducting oceanic lithosphere. We use thermal network theory, numerical simulations, and laboratory experiments to provide tighter physical insight into this process. We isolate two end-member dynamic regimes. In the thermally well mixed regime the insulating effect of continental lithosphere can not cause a localized increase in mantle temperature due to the efficiency of lateral mixing in the mantle. In this regime the potential temperature of the entire mantle is higher than it would be without continents, the magnitude depending on the relative thickness of continental and oceanic lithosphere (i.e., the insulating effects of continental lithosphere are communicated to the entire mantle). Thermal mixing can be short circuited if subduction zones surround a supercontinent or if the convective flow pattern of the mantle becomes spatially fixed relative to a stationary supercontinent. This causes a transition to the thermal isolation regime: The potential temperature increases below a supercontinent whereas the potential temperature below oceanic domains drops such that the average temperature of the whole mantle remains constant. Transition into this regime would thus involve an increase in the suboceanic viscosity, due to local cooling, and consequently a decrease in the rate of oceanic lithosphere overturn. Transition out of this regime can involve the unleashing of flow driven by a large lateral temperature gradient, which will enhance global convective motions. Our analysis highlights that transitions between the two states, in either direction, will effect not only the mantle below a supercontinent but also the mantle below oceanic regions. This provides a larger set of predictions that can be compared to the geologic record to help determine if a hypothesized

  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. Numerical modeling of the influence of cool skin on the heat balance and thermal regime of a water body

    NASA Astrophysics Data System (ADS)

    Chechin, D. G.; Repina, I. A.; Stepanenko, V. M.

    2010-08-01

    The influence that cool skin has on the energy exchange between the atmosphere and the ocean is investigated in this work. For this purpose, a series of numerical experiments with the use of the one-dimensional LAKE model of a water body were performed. Three types of cold-skin parameterization were used in this model. The data of in situ measurements in the coastal zone of the Black Sea, in the Arctic Ocean, and over Lake Sparkling served as the boundary and initial conditions. It has been established from the results of experiments that the LAKE model with the incorporated parameterization of the cool skin successfully reproduces cold-skin characteristics, namely, the difference between the temperature of the cool skin surface and the water temperature below the skin. The results of numerical experiments are within the variability of the results of in situ measurements. It has been shown that the presence of a cool skin reduces the heat losses of a body of water. The numerical experiments showed that the presence of a cool skin can change the thermal regime of a water body and its stratification by changing the heat balance at the surface. This result can be important for the modeling of many processes inside a body of water and at its surface, for example, gas and heat exchange.

  6. Observations on permafrost ground thermal regimes from Antarctica and the Italian Alps, and their relevance to global climate change

    NASA Astrophysics Data System (ADS)

    Mauro, Guglielmin

    2004-01-01

    Active-layer monitoring and the permafrost thermal regime are key indicators of climate change. The results of 3 years (1997-1999) of active-layer monitoring at one high-mountain site (La Foppa, 46°28'42″N; 10°11'18″E, 2670 m a.s.l.) and at one Antarctic site (Boulder Clay, 74°44'45″S; 164°01'17″E, 205 m a.s.l) are presented. The initial analysis of a thermal profile in a borehole (100.3 m deep) within mountain permafrost at Stelvio (3000 m a.s.l., 46°30'59″N; 10°28'35″E) is also presented. At the alpine site, the active-layer thickness variations (between 193 and 229 cm) relate to both the snow cover and to the air temperature changes. By contrast, at the Antarctic site, there is a strong direct linkage only between air temperature fluctuations and active-layer variations. At the alpine (La Foppa) site, the relationship between climate and active-layer thickness is complicated by thermal offset that is almost negligible at both the Stelvio and Antarctic sites. The permafrost temperature profile at Stelvio site contains a climate signal suitable for paleoclimate reconstruction. The permafrost at this site has a mean annual ground surface temperature (MAGST) of -1.9 °C (during 1998/1999), an active layer of about 2.5 m thick and a total thickness of ˜200 m. Analysis of the MAGST history, obtained by applying a simple heat conduction one-dimensional model, revealed the occurrence of a cold period from 1820 to 1940 followed by a warming period until 1978. Since the beginning of the 1980s, temperature dropped (less than 2 °C) until the middle 1990s, when a new period of warming started. All these climatic changes fit well with the glacial fluctuations in the area and with other paleoclimatic information derived from different proxy data.

  7. 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

  8. 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.

  9. 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%.

  10. Continents, Super-Continents, Mantle Thermal Mixing, and Mantle Thermal Isolation

    NASA Astrophysics Data System (ADS)

    Lenardic, A.; Jellinek, M.; O'Neill, C.; Cooper, C. M.; Moresi, L.; Lee, C.

    2010-12-01

    Super-continental insulation refers to an increase in the temperature of the mantle below a super-continent due to the heat transfer inefficiency of thick, stagnant continental lithosphere relative to thinner, subducting oceanic lithosphere. Recent studies have reached different conclusions as to the physical viability of this hypothesized effect with some groups arguing for a large heat up (100 degrees) and others arguing that any local heating is so small as to be insignificant. We start with the position that both groups are correct, in different limits, and use a combination of thermal network theory, numerical simulations, and laboratory experiments to provide tighter physical insight into the thermal link between continents and the mantle. We isolate two end-member dynamic regimes. In the thermally well mixed regime the insulating effect of continental lithosphere can not cause a localized increase in mantle temperature due to the efficiency of lateral mixing in the mantle. In this regime the potential temperature of the entire mantle is higher than it would be without continents (the magnitude depending on the specific properties of continental and oceanic lithosphere). Thermal mixing can be short circuited if, for example, subduction zones surround a super-coninent or if the convective flow pattern of the mantle becomes spatially fixed relative to a stationary super-continent. This causes a transition to the thermal isolation regime: The potential temperature increases below a super-coninent while the potential temperature below oceanic domains drops such that the volume averaged temperature of the whole mantle remains constant. Transition out of this regime would thus involve the unleashing of a potentially large lateral temperature gradient that would enhance global convective motions. The connection to sub-oceanic domains provides a larger set of predictions that can be compared to the post pangea geologic record to help determine if a hypothesized super-continental

  11. 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

  12. 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

  13. Conditions and Features of Paleoproterozoic Continental Subduction from Supercomputer Modelling Results

    NASA Astrophysics Data System (ADS)

    Zavyalov, Sergey; Zakharov, Vladimir

    2017-04-01

    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. The presence of ultra-high pressure metamorphic (UHPM) rocks in collisional orogens is considered reliable indicator of continental subduction. Low spread of Precambrian UHPM terranes gives reason to believe that subduction of continental crust was not common. 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 140-250 km thick, with convergence rate - 5 cm/year. In the model, the upper mantle temperature is 130-150⁰C higher than the modern value, while the continental crust radiogenic heat production is higher than the present value by the factor of 1.5. The results have shown that even in the Paleoproterozoic conditions continental subduction is widespread process. The primary parameter, which has the most significant influence on continental subduction style is composition of the continental crust. The 2 following archetypal settings of continental crust composition are examined: 1) completely felsic continental crust; 2) basic lower crust and felsic upper crust. Continental subduction with the felsic crust is short-termed and lasts less than 5 Myr. Rocks exhume very fast (< 1 Myr). In the case of basic lower crust, a continental subduction is more stable and last over 15 Myr. This work was supported by the Supercomputing Centre of Lomonosov Moscow State University.

  14. Assessing the conditions of continental breakup at magma-poor rifted margins: What can we learn from slow spreading mid-ocean ridges?

    NASA Astrophysics Data System (ADS)

    Cannat, Mathilde; Manatschal, Gianreto; Sauter, Daniel; Péron-Pinvidic, Gwenn

    2009-05-01

    We propose a review of the tectonic, magmatic and hydrothermal evolution of slow spreading ridges, focusing on concepts which we think are most relevant to discuss the rift to drift transition at magma-poor ocean-continent transitions (OCTs). Based on this review, we emphasize the importance of the thermal regime as a key parameter and we propose that the thermal regime of magma-poor OCTs evolves in the following principal phases: the onset of decompression mantle melting, the onset of localized plate divergence, the installation of a ridge-type thermal regime (active heat balance, no inheritance), which we argue is the most practical definition for continental breakup, and, possibly, the onset of ridge-type, focused mantle upwelling. We propose this phased evolution as a framework in which to develop further research, combining our understanding of rifting and seafloor spreading, in order to better quantify the processes that control continental breakup.

  15. 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.

  16. 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.

  17. 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.

  18. Accessory Mineral Depth-Profiling Applied to the Corsican Lower Crust: A Continuous Thermal History of Mesozoic Continental Rifting

    NASA Astrophysics Data System (ADS)

    Seymour, N. M.; Stockli, D. F.; Beltrando, M.; Smye, A.

    2015-12-01

    Despite advances in understanding the structural development of hyperextended magma-poor rift margins, the temporal and thermal evolution of lithospheric hyperextension during rifting remains only poorly understood. In contrast to classic pure-shear models, multi-stage rift models that include depth-dependent thinning predict significant lower-crustal reheating during the necking phase due to buoyant rise of the asthenosphere. The Santa Lucia nappe of NE Corsica is an ideal laboratory to test for lower-crustal reheating as it preserves Permian lower crust exhumed from granulitic conditions during Mesozoic Tethyan rifting. This study presents the first use of apatite U-Pb depth-profile thermochronology in conjunction with novel rutile U-Pb and zircon U-Pb thermo- and geochronology to reconstruct a continuous t-T path to constrain the syn-rift thermal evolution of this exposed lower-crustal section. LASS-ICP-MS depth-profile analyses of zircon reveal thin (<10 μm) ~210-180 Ma overgrowths on 300-270 Ma cores in lower-crustal lithologies, indicative of renewed thermal activity during Mesozoic rifting. Cooling due to rapid rift margin exhumation is recorded by the topology of rutile and apatite depth profiles caused by thermally-activated volume diffusion at T >400°C. Lower-crustal rutile reveal a rounded progression from core plateaus at ~170 Ma to 150-145 Ma at the outer 8-10 μm of grains while middle-crustal apatite records 170 Ma cores grading to 140-135 Ma rims. Inverse modeling of rutile profiles suggests the lower crust cooled from 700°C at 200 Ma to 425°C at 140 Ma. Middle-crustal apatite yield a two-stage history, with rapid cooling from 500°C at 200 Ma to 420°C at ~180 Ma followed by slow cooling to 400°C by 160 Ma. Combined with zircon overgrowth ages, these data indicate the Santa Lucia nappe underwent a thermal pulse in the late Triassic-early Jurassic associated with depth-dependent thinning and hyperextension of the Corsican margin.

  19. Evaluating the performance of coupled snow-soil models in SURFEXv8 to simulate the permafrost thermal regime at a high Arctic site

    NASA Astrophysics Data System (ADS)

    Barrere, Mathieu; Domine, Florent; Decharme, Bertrand; Morin, Samuel; Vionnet, Vincent; Lafaysse, Matthieu

    2017-09-01

    Climate change projections still suffer from a limited representation of the permafrost-carbon feedback. Predicting the response of permafrost temperature to climate change requires accurate simulations of Arctic snow and soil properties. This study assesses the capacity of the coupled land surface and snow models ISBA-Crocus and ISBA-ES to simulate snow and soil properties at Bylot Island, a high Arctic site. Field measurements complemented with ERA-Interim reanalyses were used to drive the models and to evaluate simulation outputs. Snow height, density, temperature, thermal conductivity and thermal insulance are examined to determine the critical variables involved in the soil and snow thermal regime. Simulated soil properties are compared to measurements of thermal conductivity, temperature and water content. The simulated snow density profiles are unrealistic, which is most likely caused by the lack of representation in snow models of the upward water vapor fluxes generated by the strong temperature gradients within the snowpack. The resulting vertical profiles of thermal conductivity are inverted compared to observations, with high simulated values at the bottom of the snowpack. Still, ISBA-Crocus manages to successfully simulate the soil temperature in winter. Results are satisfactory in summer, but the temperature of the top soil could be better reproduced by adequately representing surface organic layers, i.e., mosses and litter, and in particular their water retention capacity. Transition periods (soil freezing and thawing) are the least well reproduced because the high basal snow thermal conductivity induces an excessively rapid heat transfer between the soil and the snow in simulations. Hence, global climate models should carefully consider Arctic snow thermal properties, and especially the thermal conductivity of the basal snow layer, to perform accurate predictions of the permafrost evolution under climate change.

  20. 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

  1. 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

  2. Continental shelves

    SciTech Connect

    Postma, H.; Zijlstra

    1987-01-01

    Continental shelves form a relatively narrow fringe, of varying width, around the continents. Altogether they take up only about 7% of the ocean's surface and less than 0.2% if its volume. Nevertheless, their specific biological characteristics and economical importance justify a separate discussion in this series. Ecosystems of the World. The specific biological characteristics are due to the position of continental shelves between the land masses on one side and the oceans on the other, to their relative shallowness and variable sea-floor texture and to the fact that, besides residual currents, tidal streams exert a great influence on the movements of water bodies.

  3. 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.

  4. 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

  5. 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.

  6. 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 Central

    Choi, Jeunghwan

    2010-01-01

    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 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 °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 °C has shown that the thermal conductivity will drop in both PBS and tissue (liver) due to amorphous/glassy phases (vs. ice) 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 heat transfer in PBS (phosphate buffered saline) and porcine liver with and without cryoprotectants (glycerol). Using measured property values (thermal conductivity, specific heat, and latent heat

  7. 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.

  8. Controls on the Flow Regime and Thermal Structure of the Subduction Zone Mantle Wedge: A Systematic 2-D and 3-D Investigation

    NASA Astrophysics Data System (ADS)

    Le Voci, Giuseppe; Davies, Rhodri; Goes, Saskia; Kramer, Stephan; Wilson, Cian

    2014-05-01

    Arc volcanism at subduction zones is likely regulated by the mantle wedge's flow regime and thermal structure and, hence, numerous studies have attempted to quantify the principal controls on mantle wedge conditions. Here, we build on these previous studies by undertaking the first systematic 2-D and 3-D numerical investigation, across a wide parameter-space, into how hydration and thermal buoyancy influence the wedge's flow regime and associated thermal structure, above a kinematically driven subducting plate. We find that small-scale convection (SSC), resulting from Rayleigh-Taylor instabilities, or drips, off the base of the overriding lithosphere, is a typical occurrence, if: (i) viscosities are < 5×1018 Pa s; and (ii) hydrous weakening of wedge rheology extends at least 100-150 km from the trench. In 2-D models, instabilities generally take the form of 'drips'. Although along-strike averages of wedge velocities and temperature in 3-D structure are consistent with those in 2-D, fluctuations are larger in 3-D. Furthermore, in 3-D, two separate, but interacting, longitudinal Richter roll systems form (with their axes aligned perpendicular to the trench), the first below the arc region and the second below the back-arc region. These instabilities result in transient and spatial temperature fluctuations of 100-150K, which are sufficient to influence melting, the stability of hydrous minerals and the dehydration of crustal material. Furthermore, they are efficient at eroding the overriding lithosphere, particularly in 3-D and, thus, provide a means to explain observations of high heat flow and thin back-arc lithosphere at many subduction zones, if back-arc mantle is hydrated.

  9. Thermal regime along the Antilles subduction zone: Influence of the oceanic lithosphere materials subducted in the oceanic crust

    NASA Astrophysics Data System (ADS)

    Biari, Youssef; Marcaillou, Boris; Klingelhoefer, Frauke; Francis, Lucazeau; Fréderique, Rolandone; Arnauld, Heuret; Thibaud, Pichot; Hélène, Bouquerel

    2017-04-01

    Heat-flow measurements acquired during the Antithesis Cruise in the Northern Lesser Antilles reveal an atypical heat-flow trend, from the trench to the margin forearc, where the subducting crust consists of exhumed and serpentinized mantle rocks (see Marcaillou et al. same session). We investigate the thermal structure of the Lesser Antilles subduction zone along two transects perpendicular to the margin located off Antigua and Martinique Islands. We perform 2-D steady-state finite elements thermal modelling constrained by newly-recorded and existing data: heat flow measurements, deep multichannel reflection and wide angle seismic data as well as earthquake hypocenters location at depth. Along the Martinique profile, the heat-flow decreases from the trench (45 mW.m-2) to minimum in the outer fore-arc (30 mW.m-2) and increases to a plateau (50 mW.m-2) toward the back-arc area. These trend and values are typical for the subduction of a steep 80-MYr old oceanic plate beneath an oceanic margin. As a result, the 150°-350°C temperature range along the interplate contact, commonly associated to the thermally-defined seismogenic zone, is estimated to be located between 200 - 350km from the trench. In contrast, along the Antigua profile, the heat-flow shows an atypical "flat" trend at 40 ± 15 mW.m-2 from the trench to the inner forearc. Purely conductive thermal models fail at fitting both the measured values and the flat trend. We propose that the subducting crust made of serpentinized exhumed mantle rock strongly affecting the heat-flow at the surface and the margin thermal structure. The geothermal gradient in the 5-km-thick serpentinized layer is expected to be low compared to "normal" oceanic crust because of cold water percolation and peridotite alteration. Moreover, from 50km depth, serpentine dehydration reactions provide significant amounts of hot water expelled toward the upper plate, generated heat beneath the forearc. As a result, in our preferred model: 1/ A

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Thermal Regime in a Building in the Presence of Mixing of Heat Carriers from Delivery and Return Pipelines

    NASA Astrophysics Data System (ADS)

    Sabdenov, K. O.; Unaspekov, B. A.; Erzada, M.; Igembaev, B. A.

    2014-01-01

    We consider the problem of establishing a temperature regime in rooms and a heating system on mixing heat carriers flowing in a delivery and return pipelines. We show that unlimited mixing of heat carriers leads to the leveling of temperatures on the stories of a building and to attainment of a limiting temperature in the building close to the heat carrier temperature in the delivery pipeline of the municipal network. It has been established that if the heat carrier flow rate in the heating system does not change in the process of mixing, the temperature in the heating system and the temperature in the rooms of a building can decrease to the outdoor air temperature.

  16. Investigating the Sedimentary Response and its Role in Climate Feedbacks Associated with the Paleocene Eocene Thermal Maximum in a Continental Shelf Setting: Lodo Gulch, Lodo Formation, CA

    NASA Astrophysics Data System (ADS)

    Delmanowski, R. D.; Mushegan, A.; Brady, M. E.; Pluhar, C. J.

    2014-12-01

    The Lodo Formation (central CA), records the carbon isotope excursion (CIE) associated with the Paleocene Eocene Thermal Maximum (PETM) in a continental margin setting, where increased sedimentation rates - attributed to an enhanced hydrological cycle - provide a means for significant carbon drawdown after the peak of this hyperthermal event (John et al. 2008). This study investigates variations in grain size associated with the recovery from peak CIE values to better constrain the potential mechanism of the apparent increase in sedimentation rates, which can shed light on climate dynamics and feedbacks associated with other warming events.We collected bulk samples at ~10 cm increments over a stratigraphic interval that encompasses the previously documented CIE onset, peak, and recovery phases. We used a laser diffraction particle size analyzer on disaggregated samples to permit detection of variation within clay and silt sediment size fractions (2-63 microns) in addition to sand-size grains. Results show that, while the onset and peak CIE is associated with abundant clays, the recovery interval preserves a marked shift in median grain size to coarse silt and very fine sand. Ongoing work indicates that the grain size increase is not associated with an increase in foraminiferal abundance. Enhanced terrigenous sediment delivery during the CIE recovery could explain both the increase in grain size (this study) and sedimentation rates (previous work). This increased sediment supply could be attributed to (1) increased seasonality and storm intensity during the hyperthermal, (2) marine regression (i.e. basinward shift in shoreline) associated with decreasing rates of sea level rise during sea level highstand, or some combination of these factors. Future work to document compositional and preservational changes in sediments and foraminifera over this time interval will aid in teasing apart the relative influence of potential drivers of change associated with this event.

  17. 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).

  18. Influence Of Clear-cutting On Thermal and hydrological Regime In The Active Layer Near Yakutsk, Eastern Siberia

    NASA Astrophysics Data System (ADS)

    Iwahana, G.; Kobayashi, Y.; Machimura, T.; Fedorov, A. N.; Fukuda, M.

    2004-12-01

    Thermal and hydrological conditions in the active layer were investigated simultaneously at a mature larch forest (control site) and a cutover, which experienced clear-cutting in November 2000 during the thawing periods from 2001 to 2003, near Yakutsk, Eastern Siberia. The two sites were located about 100m apart and the cutover was formerly a part of the control larch forest site. The aims were to clarify the characteristics of heat and water budget in the active layer, and to assess the influence of clear-cutting on permafrost and active layer conditions, based on field observations at both intact and clear-cut forest. Clear-cutting enhanced ground thawing and the difference in the active layer thickness between the forest and the cutover (1-year) was 14cm. The soil water content drastically decreased at the forest, while that at the cutover was retained in during the first thawing season after clear-cutting. Marked changes in the active layer conditions were limited only to the first thawing season. The difference in the maximum thaw depth did not expand significantly in the second thawing season despite the increased ground heat flux at the cutover site. Thermal and hydrological analyses of the active layer revealed that the storage of latent heat was a predominant component in the energy balance in the active layer. Thus, the soil moisture condition, especially spring ice content in the active layer, plays an important role in controlling the energy balance of the active layer. Further increases in the maximum thaw depth at the cutover site were inhibited by the thermal inertial effect of the larger amount of ice in the second spring after disturbance.

  19. 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.

  20. The Effects of Rapid Sedimentation upon Continental Breakup: Kinematic and Thermal Modeling of the Salton Trough, Southern California, Based upon Recent Seismic Images

    NASA Astrophysics Data System (ADS)

    Han, L.; Hole, J. A.; Lowell, R. P.; Stock, J. M.; Fuis, G. S.

    2016-12-01

    The Salton Seismic Imaging Project (SSIP) illuminated crustal and upper mantle structure of the Salton Trough, the northern-most rift segment of the Gulf of California plate boundary. The crust is 17-18 km thick and homogeneous for 100 km in the plate motion direction. New crust is being created by distributed rift magmatism, Colorado River sedimentation, and metamorphism of the sediment. A 5 km thick pre-existing crustal layer may still exist. The crust has not broken apart to enable initiation of seafloor spreading. A one-dimensional time-dependent kinematic and thermal model was developed to simulate these observations. We assume that all crustal layers are stretched uniformly during extension. Distributed mafic magmatism and sedimentation are added simultaneously to compensate for the crustal thinning. The ratio of magmatism to sedimentation is constrained by the seismic observations. Heat is transported by thermal conduction and by advection due to stretching of the crust. A constant temperature boundary at the Moho is used to represent partial melting in the upper mantle. Assuming a constant plate motion rate, the zone of active rifting extends linearly with time. The crustal thickness and internal structure also evolve with time. The model constraints are the observed seismic structure and heat flow. The model rapidly reaches quasi-steady state, and could continue for many millions of years. The observed seismic structure and heat flow are reproduced after 3 Myr. The yield strength profile calculated from lithology and model temperature indicates that ductile deformation in the middle and lower crust dominates the crustal rheology. Rapid sedimentation delays crustal breakup and the initiation of seafloor spreading by maintaining the thickness of the crust and keeping it predominantly ductile. This process probably occurs wherever a large river flows into an active rift driven by far-field extension. It may have built passive margins in many locations

  1. 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

  2. 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

  3. Three temperature regimes in superconducting photon detectors: quantum, thermal and multiple phase-slips as generators of dark counts.

    PubMed

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

    2015-05-19

    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.

  4. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea

    PubMed Central

    Falfushynska, Halina I.; Phan, Tuan; Sokolova, Inna M.

    2016-01-01

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20–41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8–12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC. PMID:27995990

  5. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea.

    PubMed

    Falfushynska, Halina I; Phan, Tuan; Sokolova, Inna M

    2016-12-20

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20-41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8-12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC.

  6. Long-Term Acclimation to Different Thermal Regimes Affects Molecular Responses to Heat Stress in a Freshwater Clam Corbicula Fluminea

    NASA Astrophysics Data System (ADS)

    Falfushynska, Halina I.; Phan, Tuan; Sokolova, Inna M.

    2016-12-01

    Global climate change (GCC) can negatively affect freshwater ecosystems. However, the degree to which freshwater populations can acclimate to long-term warming and the underlying molecular mechanisms are not yet fully understood. We used the cooling water discharge (CWD) area of a power plant as a model for long-term warming. Survival and molecular stress responses (expression of molecular chaperones, antioxidants, bioenergetic and protein synthesis biomarkers) to experimental warming (20–41 °C, +1.5 °C per day) were assessed in invasive clams Corbicula fluminea from two pristine populations and a CWD population. CWD clams had considerably higher (by ~8–12 °C) lethal temperature thresholds than clams from the pristine areas. High thermal tolerance of CWD clams was associated with overexpression of heat shock proteins HSP70, HSP90 and HSP60 and activation of protein synthesis at 38 °C. Heat shock response was prioritized over the oxidative stress response resulting in accumulation of oxidative lesions and ubiquitinated proteins during heat stress in CWD clams. Future studies should determine whether the increase in thermal tolerance in CWD clams are due to genetic adaptation and/or phenotypic plasticity. Overall, our findings indicate that C. fluminea has potential to survive and increase its invasive range during warming such as expected during GCC.

  7. 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.

  8. Monoenergetic acceleration of a target foil by circularly polarized laser pulse in RPA regime without thermal heating

    SciTech Connect

    Khudik, V.; Yi, S. A.; Siemon, C.; Shvets, G.

    2012-12-21

    A kinetic model of the monoenergetic acceleration of a target foil irradiated by the circularly polarized laser pulse is developed. The target moves without thermal heating with constant acceleration which is provided by chirping the frequency of the laser pulse and correspondingly increasing its intensity. In the accelerated reference frame, bulk plasma in the target is neutral and its parameters are stationary: cold ions are immobile while nonrelativistic electrons bounce back and forth inside the potential well formed by ponderomotive and electrostatic potentials. It is shown that a positive charge left behind of the moving target in the ion tail and a negative charge in front of the target in the electron sheath form a capacitor whose constant electric field accelerates the ions of the target. The charge separation is maintained by the radiation pressure pushing electrons forward. The scalings of the target thickness and electromagnetic radiation with the electron temperature are found.

  9. 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.

  10. 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.

  11. 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

  12. 3D numerical modelling of the steady-state thermal regime constrained by surface heat flow data: a Monte Carlo approach

    NASA Astrophysics Data System (ADS)

    Mather, B.; Moresi, L. N.; Cruden, A. R.

    2014-12-01

    Uncertainty of the lithospheric thermal regime greatly increases with depth. Measurements of temperature gradient and crustal rheology are concentrated in the upper crust, whereas the majority of the lithospheric measurements are approximated using empirical depth-dependent functions. We have applied a Monte Carlo approach to test the variation of crustal heat flow with temperature-dependent conductivity and the redistribution of heat-producing elements. The dense population of precision heat flow data in Victoria, Southeast Australia offers the ideal environment to test the variation of heat flow. A stochastically consistent anomalous zone of impossibly high Moho temperatures in the 3D model (> 900°C) correlates well with a zone of low teleseismic velocity and high electrical conductivity. This indicates that transient heat transfer has perturbed the thermal gradient and therefore a steady-state approach to 3D modelling is inappropriate in this zone. A spatial correlation between recent intraplate volcanic eruption points (< 5 Ma) and elevated Moho temperatures is a potential origin for additional latent heat in the crust.

  13. Thermal transfer and pressure regime across a rifted margin in the presence of evaporites, with consequences for the hydrocarbon potential: A modeling approach in the Provencal basin

    SciTech Connect

    Burrus, J.; Audebert, F.

    1988-08-01

    Modeling the hydrocarbon potential of a sedimentary basin requires one to at least reconstruct the burial, the thermal history, and the pressure regime in the sediments. This is complicated, in the case of the western Mediterranean basins, by two problems: (1) Reconstruction of the temperature history is dependent on the rifted nature of these basins and on the particular distribution of thermal gradients linked with the presence of the high-conductivity evaporitic layers deposited in the late Miocene. (2) Reconstruction of pore pressure must account for the high sedimentation rate generally observed in the Pliocene-Quaternary and the presence of hydraulic barriers which correspond to the evaporitic layers. The negligible permeability of these rocks created a significant undercompaction of the sediments underneath, associated with high excess pressures. The authors present the result of a modeling study of these effects using a 2-D code (Themis) developed at IFP. The model describes simultaneously the geodynamic evolution of the margin during and after rifting and the phenomena of heat redistribution and abnormal compaction in the sediments. This is applied to the evolution of the Gulf of Lions margin (Provencal basin, northwestern Mediterranean). The effects of these processes for the level of maturation of organic matter and pattern of migration are discussed.

  14. Increases in the mean and variability of thermal regimes result in differential phenotypic responses among genotypes during early ontogenetic stages of lake sturgeon (Acipenser fulvescens).

    PubMed

    Dammerman, Kari J; Steibel, Juan P; Scribner, Kim T

    2016-12-01

    Climate change is affecting thermal conditions worldwide. Understanding organismal responses associated with predicted changes are essential for predicting population persistence. Few studies have examined the effects of both increased mean and variance in temperature on organismal traits, particularly during early life stages. Using lake sturgeon (Acipenser fulvescens) from Black Lake, MI, we tested whether phenotypic variation differed among families reared in two constant (10 and 18°C) and two fluctuating-temperature treatments (10-19°C) representing temperatures experienced in the river and a simulated anthropogenic disturbance. Body length, body area, and yolk-sac area were quantified at hatch. Family-by-treatment interactions explained up to 50% of the variance observed among families in offspring hatch traits. Families incubated in 18°C and the fluctuating anthropogenic treatment had 6-10 times higher variance in traits than those incubated at 10°C. Hatched larvae were placed in raceways with ambient river water. Emergence body length, emergence timing, and growth were quantified upon emergence. Families differed in time to emergence and growth with the greatest range observed in the 18°C treatment. Results demonstrate that differential responses among genotypes to changes in the mean and variability of thermal incubation regimes can affect traits at hatch as well as a subsequent ontogenetic stage.

  15. 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

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

    NASA Astrophysics Data System (ADS)

    Hurwitz, Shaul; Farrar, Christopher D.; Williams, Colin F.

    2010-12-01

    Long Valley Caldera in eastern California formed 0.76 Ma ago in a cataclysmic eruption that resulted in the deposition of 600 km 3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~ 290 MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40 MWe. The RD in the center of the caldera was uplifted by ~ 80 cm 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 (327-1,158 m) 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

  17. Effects of spatially variable snow cover on thermal regime and hydrology of an Arctic ice wedge polygon landscape identified using ground penetrating radar and LIDAR datasets

    NASA Astrophysics Data System (ADS)

    Gusmeroli, A.; Liljedahl, A. K.; Peterson, J. E.; Hubbard, S. S.; Hinzman, L. D.

    2012-12-01

    Ice wedge polygons are common in Arctic terrains underlain by permafrost. Permafrost degradation could transform low- into high centered polygons, causing profound changes in the hydrologic regime of Arctic lands, which in turn, could affect the energy balance and subsurface biodegradation of organic carbon responsible for greenhouse gas production. Understanding the linkages between microtopography, snow cover, thermal properties, and thaw depth is critical for developing a predictive understanding of terrestrial ecosystems and their feedbacks to climate. In this study, we use high frequency (500-1000 MHz) ground penetrating radar (GPR) data acquired in spring 2012 within the Next Generation Ecosystem Experiment (NGEE) study site in Barrow, AK to characterize the spatial variability of snow distribution. We compare it's distribution to microtopography, estimated using LIDAR data, and thaw depth, also estimated using ground penetrating radar collected at different times during the year and simulated over time using mechanistic thermal-hydrologic modeling. The high spatial resolution offered by LIDAR and ground penetrating radar permit detailed investigations of the control of microtopography on snow and thaw layer depth. Results suggest that microtopographical variations are responsible for substantial differences in snow accumulation. In low centered polygons, snow depth can be up to four times greater in the troughs than on the rims. Both modeling and observations suggest that the microtopography-governed snow thickness affects the thermal properties of the subsurface and thus the thaw layer thickness; regions with thicker snowpack generally correspond to regions of greater thaw depth. We conclude that a transition from low- to high centered polygons will not only impact watershed runoff but, since snow accumulation is sensitive to the microtopography, it will also impact snow distribution. In turn, snow distribution affects thaw depth thickness, and the

  18. The response of the Mediterranean gorgonian Eunicella singularis to thermal stress is independent of its nutritional regime.

    PubMed

    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.

  19. 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.

  20. 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.

  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. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. 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.

  3. Monitoring of active layer thermal regime and depth on CALM-S site, James Ross Island, Eastern Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Hrbáček, Filip; Kňažková, Michaela; Nývlt, Daniel; Láska, Kamil; Mueller, Carsten W.; Ondruch, Jakub

    2017-04-01

    ) and -6.7 °C (2015), while the mean annual ground temperature at 5 cm ranged from -5.6 °C (2013) to -5.3 °C (2014). Thawing season started in mid-November between 17th (2013/14) and 24th (2014/15) and ended at the end of February (22nd in 2014/15) and beginning of March (7th in 2013/14). The maximum active layer thickness determined from 0°C isotherm varied from 86 to 87 cm at profile 1, while it reached only 51 to 65 cm at profile 2. The mean probed active layer depth varied between 66 cm (2013/4) and 78 cm (2014/15). The maximum probed active layer depth increased from 100 cm in 2014 to 113 cm in 2016. High variability of active layer depth across CALM-S site was caused by different ground thermal properties of Holocene marine terrace sand and Cretaceous clayey sandstones. These results differ significantly from another CALM-S sites in Antarctica, where the main factors affecting thawing depth variability were snow cover and topography. These results confirmed previous observation from James Ross Island, where variability of active layer depth was related primarily to different ground properties (texture, moisture, physical characteristic) then local climate or snow cover.

  4. 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.

  5. 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.

  6. 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.

  7. He and N isotopes in thermal springs of the Mexican Pacific coast: subducting slab, continental crust and mantle contributions to fluids of a forearc zone.

    NASA Astrophysics Data System (ADS)

    Taran, Yuri; Inguaggiato, Salvatore; Varley, Nicholas; Ramirez Guzman, Alejandro

    2010-05-01

    Two oceanic plates are subducting beneath the continent along the Mexican Pacific coast: Cocos Plate south of Colima graben (~19°N) and a young Rivera Plate to the north of Colima graben. The trench is situated ~ 70 km from the shore line which is very close comparing with other continental margins. There are 26 groups of thermal springs between 16°N and 21°N, in a 30 km-wide zone along the coast. The temperature and salinity ranges are 40-90°C and 100-20,000 ppm, respectively. The springs are mainly of a low salinity (< 1000 ppm), high pH (8-10) and temperatures of 37-50°C. Almost all springs discharge bubbling gas with N2 as a predominant component and have He content between 400 and 1500 ppmV. Two groups of springs are methane-rich (70 and 10 vol%). The CO2-rich springs and high-HCO3 waters are absent. All springs to the south of the Michoacan-Guerrero boarder (~ 18°N) are characterized by N2/Ar ≈ 100, δ15N ≈0 and 3He/4He ratios lower than 0.2Ra (where Ra=1.4x10-6, the air ratio) except the Paso Real springs (0.9Ra) located within a Coyuca seismogenic fracture zone. Springs along the Michoacan coast, the northern part of the Cocos Plate subduction, discharge gases with 1.5Ra < 3He/4He <2.5Ra but still low, close to the atmospheric N2/Ar and δ15N ≈0. All springs located within the Colima graben have high 3He/4He (up to 4.5Ra) and elevated N2/Ar and δ15N. The El Salitre (La Tuna) springs located within the southern board of the Colima graben discharge saline Na-Ca-Cl water (46°C, Cl=15,000 ppm) with N2/Ar > 400, δ15N = +4.6‰, almost no CH4 (<0.1 %) and 3He/4He = 2.3Ra. The only group of hot springs within the Jalisco Block and close to the shore line, Rio Purificacion, discharge hot, saline Na-Cl water (80°C, 12,000 ppm of Cl), with N2/Ar > 300, δ15N = +5‰ and 3He/4He = 0.4Ra. A number of hot and warm springs associated with Puerto Vallarta graben are characterized by high 3He/4He up to 4.5Ra, elevated N2/Ar and δ15N. The last group, Punta

  8. The coarse- to fine-grained boundary beneath the New England Mud Patch: evidence from seismic and core data for an abrupt post-transgressive change in hydrologic regime on the continental shelf

    NASA Astrophysics Data System (ADS)

    Goff, J.; Chaytor, J. D.; Reed, A. H.; Liu, S.; Wilson, P. S.; Knobles, D. P.

    2016-12-01

    The New England Mud Patch (NEMP) is an anomaly on the Atlantic coast of North America. This 13,000 km2 area, located south of Cape Cod between the 60 m and 160 m isobaths, is a region of active fine-grained deposition on a shelf that is predominantly non-depositional and even erosional in places. Prior studies theorized that NEMP sediments are derived from fines winnowed from Georges Bank, transported westward by coastal currents, and then settled in more quiescent conditions at the mud patch. A CHIRP seismic reflection (2015) and coring (2016) survey of the NEMP was conducted in support of a planned acoustic experiment for the Office of Naval Research. The survey focused on a 30 km (E-W) by 8 km (N-S) region between the 75 m and 85 m isobaths, encompassing a sediment "pond" up to 13 m thick. The dense (250 m) CHIRP survey lines allow a pseudo-3D stratigraphic interpretation. The sediment pond itself occupies an accommodation space that appears to have been eroded into substrate (Pleistocene?) sediments, perhaps by glacial processes. The interpreted transgressive ravinement is capped by marine sands organized into oblique sand ridge morphology. The sense of obliquity, morphologic asymmetry and internal dipping reflectors indicate that the sand ridges formed under an east-directed transport regime. However, as evidenced by prograding internal layering, NEMP deposition occurred under a west-directed transport regime, consistent with modern shelf conditions. The onset of fine-grained deposition was therefore contemporaneous with a significant shift in the hydrologic regime. Layer reflectivity increases with depth, likely indicating that terrestrial sources may have been more prominent in the early stages of NEMP deposition. Several cores penetrated the finer-grained sediment ("mud") to sand transition; analysis this Fall should help us to better understand this important transition.

  9. 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

  10. 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.

  11. Water, lithium and trace element compositions of olivine from Lanzo South replacive mantle dunites (Western Alps): New constraints into melt migration processes at cold thermal regimes

    NASA Astrophysics Data System (ADS)

    Sanfilippo, Alessio; Tribuzio, Riccardo; Ottolini, Luisa; Hamada, Morihisa

    2017-10-01

    Replacive mantle dunites are considered to be shallow pathways for extraction of mantle melts from their source region. Dunites offer a unique possibility to unravel the compositional variability of the melts produced in the upper mantle, before mixing and crystal fractionation modify their original signature. This study includes a quantification of H2O, Li and trace elements (Ni, Mn, Co, Sc, V, Ti, Zr, Y and HREE) in olivine from large replacive dunite bodies (>20 m) within a mantle section exposed in the Western Italian Alps (Lanzo South ophiolite). On the basis of olivine, clinopyroxene and spinel compositions, these dunites were previously interpreted to be formed by melts with a MORB signature. Variations in Ni, Mn, Co and Ca contents in olivine from different dunite bodies suggested formation by different melt batches. The variable H2O and Li contents of these olivines agree with this idea. Compared to olivine from residual peridotites and olivine phenocrysts in MORB (both having H2O <5 ppm; Li >1 ppm), the Lanzo South dunite olivine has high H2O (18-40 ppm) and low Li (0.35-0.83 ppm) contents. Geochemical modelling suggests that the dunite-forming melts were produced by low melting degrees of a mixed garnet-pyroxenite-peridotite mantle source, with a contribution of a garnet pyroxenite component variable from 20 to 80%. The Lanzo dunites experienced migration of melts geochemically enriched and mainly produced in the lowermost part of the melting region. Extraction of enriched melts through dunite channels are probably characteristic of cold thermal regimes, where low temperatures and a thick mantle lithosphere inhibit mixing with melts produced at shallower depths.

  12. 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.

  13. 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.

  14. Hydrographic and ecologic implications of foraminiferal stable isotopic response across the U.S. mid-Atlantic continental shelf during the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Makarova, Maria; Wright, James D.; Miller, Kenneth G.; Babila, Tali L.; Rosenthal, Yair; Park, Jill I.

    2017-01-01

    We present new δ13C and δ18O records of surface (Morozovella and Acarinina) and thermocline dwelling (Subbotina) planktonic foraminifera and benthic foraminifera (Gavelinella, Cibicidoides, and Anomalinoides) during the Paleocene-Eocene Thermal Maximum (PETM) from Millville, New Jersey, and compare them with three other sites located along a paleoshelf transect from the U.S. mid-Atlantic coastal plain. Our analyses show different isotopic responses during the PETM in surface versus thermocline and benthic species. Whereas all taxa record a 3.6-4.0‰ δ13C decrease associated with the carbon isotope excursion, thermocline dwellers and benthic foraminifera show larger δ18O decreases compared to surface dwellers. We consider two scenarios that can explain the observed isotopic records: (1) a change in the water column structure and (2) a change in habitat or calcification season of the surface dwellers due to environmental stress (e.g., warming, ocean acidification, surface freshening, and/or eutrophication). In the first scenario, persistent warming during the PETM would have propagated heat into deeper layers and created a more homogenous water column with a thicker warm mixed layer and deeper, more gradual thermocline. We attribute the hydrographic change to decreased meridional thermal gradients, consistent with models that predict polar amplification. The second scenario assumes that environmental change was greater in the mixed layer forcing surface dwellers to descend into thermocline waters as a refuge or restrict their calcification to the colder seasons. Although both scenarios are plausible, similar δ13C responses recorded in surface, thermocline, and benthic foraminifera challenge mixed layer taxa migration.

  15. Effects of Thermal Regimes, Starvation and Age on Heat Tolerance of the Parthenium Beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) following Dynamic and Static Protocols

    PubMed Central

    Chidawanyika, Frank; Nyamukondiwa, Casper; Strathie, Lorraine; Fischer, Klaus

    2017-01-01

    Temperature and resource availability are key elements known to limit the occurrence and survival of arthropods in the wild. In the current era of climate change, critical thermal limits and the factors affecting these may be of particular importance. We therefore investigated the critical thermal maxima (CTmax) of adult Zygogramma bicolorata beetles, a biological control agent for the invasive plant Parthenium hysterophorus, in relation to thermal acclimation, hardening, age, and food availability using static (constant) and dynamic (ramping) protocols. Increasing temperatures and exposure times reduced heat survival. In general, older age and lack of food reduced heat tolerance, suggesting an important impact of resource availability. Acclimation at constant temperatures did not affect CTmax, while fluctuating thermal conditions resulted in a substantial increase. Hardening at 33°C and 35°C improved heat survival in fed young and mid-aged but only partly in old beetles, while CTmax remained unaffected by hardening throughout. These findings stress the importance of methodology when assessing heat tolerance. Temperature data recorded in the field revealed that upper thermal limits are at least occasionally reached in nature. Our results therefore suggest that the occurrence of heat waves may influence the performance and survival of Z. bicolorata, potentially impacting on its field establishment and effectiveness as a biological control agent. PMID:28052099

  16. Effects of Thermal Regimes, Starvation and Age on Heat Tolerance of the Parthenium Beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) following Dynamic and Static Protocols.

    PubMed

    Chidawanyika, Frank; Nyamukondiwa, Casper; Strathie, Lorraine; Fischer, Klaus

    2017-01-01

    Temperature and resource availability are key elements known to limit the occurrence and survival of arthropods in the wild. In the current era of climate change, critical thermal limits and the factors affecting these may be of particular importance. We therefore investigated the critical thermal maxima (CTmax) of adult Zygogramma bicolorata beetles, a biological control agent for the invasive plant Parthenium hysterophorus, in relation to thermal acclimation, hardening, age, and food availability using static (constant) and dynamic (ramping) protocols. Increasing temperatures and exposure times reduced heat survival. In general, older age and lack of food reduced heat tolerance, suggesting an important impact of resource availability. Acclimation at constant temperatures did not affect CTmax, while fluctuating thermal conditions resulted in a substantial increase. Hardening at 33°C and 35°C improved heat survival in fed young and mid-aged but only partly in old beetles, while CTmax remained unaffected by hardening throughout. These findings stress the importance of methodology when assessing heat tolerance. Temperature data recorded in the field revealed that upper thermal limits are at least occasionally reached in nature. Our results therefore suggest that the occurrence of heat waves may influence the performance and survival of Z. bicolorata, potentially impacting on its field establishment and effectiveness as a biological control agent.

  17. The microbial temperature sensitivity to warming is controlled by thermal adaptation and is independent of C-quality across a pan-continental survey

    NASA Astrophysics Data System (ADS)

    Berglund, Eva; Rousk, Johannes

    2017-04-01

    Climate models predict that warming will result in an increased loss of soil organic matter (SOM). However, field experiments suggest that although warming results in an immediate increase in SOM turnover, the effect diminishes over time. Although the use and subsequent turnover of SOM is dominated by the soil microbial community, the underlying physiology underpinning warming responses are not considered in current climate models. It has been suggested that a reduction in the perceived quality of SOM to the microbial community, and changes in the microbial thermal adaptation, could be important feed-backs to soil warming. Thus, studies distinguishing between temperature relationships and how substrate quality influences microbial decomposition are a priority. We examined microbial communities and temperature sensitivities along a natural climate gradient including 56 independent samples from across Europe. The gradient included mean annual temperatures (MAT) from ca -4 to 18 ˚ C, along with wide spans of environmental factors known to influence microbial communities, such as pH (4.0 to 8.8), nutrients (C/N from 7 to 50), SOM (from 4 to 94%), and plant communities, etc. The extensive ranges of environmental conditions resulted in wide ranges of substrate quality, indexed as microbial respiration per unit SOM, from 5-150 μg CO2g-1 SOM g-1 h-1. We hypothesised microbial communities to (1) be adapted to the temperature of their climate, leading to warm adapted bacterial communities that were more temperature sensitive (higher Q10s) at higher MAT; (2) have temperature sensitivities affected by the quality of SOM, with higher Q10s for lower quality SOM. To determine the microbial use of SOM and its dependence on temperature, we characterized microbial temperature dependences of bacterial growth (leu inc), fungal growth (ac-in-erg) and soil respiration in all 56 sites. Temperature dependences were determined using brief (ca. 1-2 h at 25˚ C) laboratory incubation

  18. Thermal Monitoring at Volcán de Colima, Mexico: Characterizing the Activity and Studying the Transition Between Explosive and Effusive Regimes

    NASA Astrophysics Data System (ADS)

    Varley, N. R.; Johnson, J.

    2005-12-01

    Volcán de Colima has significantly increased in its activity during the last few years. Explosive activity during 2005 produced pyroclastic flows which reached up to 5.44 km, distances which not been recorded since the last Plinian eruption (1913). Monitoring is being improved by the introduction of thermal, infrasound and scanning UV spectrometer systems. Seismic monitoring has been enhanced by the use of pattern recognition techniques for rapid evaluation. The techniques are being utilized to characterize and quantify both explosive and effusive activity to enable improved modelling and understand the transition between styles. Thermal imaging using an infrared camera has enabled the temporal variation in fumarole temperature to be monitored remotely. Precursory activity has been identified prior to large explosive events: swarms of low frequency (< 10 Hz) seismic events and an increase in fumarole temperatures. The distribution of the seismic events has been analysed, showing the relationship between the swarm and the magnitude of the associated explosion. Increasing temperatures reflect the uprising of the magma body and pressurization within the conduit. Explosive activity has been examined in detail, comparing the thermal characteristics of the plume with its ascent rate, gas flux, ash content and associated seismicity. The thermal evolution of some of the larger events was captured with an installed sensor. The arrival of the relatively cool pyroclastic flows was also registered. A poor correlation has been observed between certain variables, which has important implications for both numeric modelling of this type of activity and for monitoring, where seismic amplitudes are often used to quantify explosive events. Thermal monitoring during episodes of effusion enables the study of the evolution of the dome and flows, which can assist in the forecasting of collapse events. It is clear that the integration of thermal monitoring with various other geophysical

  19. 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

  20. 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

  1. 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...

  2. 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...

  3. The Jameson Land basin (east Greenland): a fission track study of the tectonic and thermal evolution in the Cenozoic North Atlantic spreading regime

    NASA Astrophysics Data System (ADS)

    Hansen, Kirsten; Bergman, Steven C.; Henk, Bo

    2001-02-01

    The Late Mesozoic and Cenozoic thermal history of the Jameson Land basin is constrained by new apatite and zircon fission track (FT) data of surface Permian to Jurassic sedimentary rocks. The results show a general regional thermal evolution related to burial to temperatures close to and in excess of the maximum temperatures of the apatite annealing interval (∼125°C) followed by cooling mainly due to Cenozoic uplift and erosion. Faulting and differential movements in the basin generally occurred after cooling below the apatite partial annealing zone (PAZ: ∼75-125°C). However, in the northern part of the basin the data suggest a thicker sediment cover or localized heating related to an earlier fracture zone. Both apatite FT analysis and vitrinite reflectance values reveal a postmature signature for the studied rocks in the northeastern Jameson Land and premature to mature for the western, central and southern Jameson Land rocks with respect to generation of hydrocarbons. The chemical variations of apatite enhance the possibility of recognizing sample positions near maximum temperatures in the PAZ. Furthermore, the Pb-Zn mineralization pattern closely follows the Tertiary maturity trend given by the FT data. The type and distribution of mineralization suggest that it was influenced by the regional thermal evolution of the basin. In the northeast domain, circulating fluids may have overprinted the regional thermal record before ca. 20 Ma. Basaltic dyke and sill intrusions (55-45 Ma) locally caused resetting of apatite FT ages, but generally the direct influence from upper crustal magmatic activity played only a minor role. The thermal evolution in northeast Jameson Land is related to the late tectonic evolution of the Northeast Atlantic involving a change in ridge position at ca. 25 Ma which followed the passage of the proto-Icelandic mantle plume at 63-40 Ma.

  4. Temperature Control of Continental Lithosphere Elastic Thickness: Effective Elastic Thickness Te vs Upper Mantle Velocity Vs

    NASA Astrophysics Data System (ADS)

    Hyndman, R. D.; Currie, C. A.; Mazzotti, S.; Frederiksen, A.

    2006-12-01

    The elastic thickness of continental lithosphere is closely related to its total strength and therefore to its susceptibility to tectonic deformation and earthquakes. Recently it has been questioned whether the elastic thickness and strength are dependent on crust and upper mantle temperatures and compositions in the way predicted by laboratory data. We test this dependence in western North America by a regional comparison of the effective elastic thickness (Te) from topography-gravity coherence, and upper mantle temperatures mapped by tomography shear wave velocities (Vs). We find a good correlation between Te and Vs of the form expected based on the thermal and laboratory data. The Te distribution is strongly bimodal as previously found globally, less than 20 km for the high temperature Cordillera and over 100 km for the adjacent cold stable Canadian Shield. Only intermediate thermal regimes have intermediate Te that suggests a weak layer in the lower crust over a stronger upper mantle. Strength envelopes based on laboratory data correspond to the observed Te for thermal regimes with temperatures at the Moho of 800-900C for the Cordillera and 400-500C for the Shield, in agreement with temperatures from Vs and other estimators. Our study supports the conclusion that lithosphere elastic thickness and strength are controlled primarily by temperature and that laboratory- based rheology provides a good first order estimate of the deformation behaviour of the crust and upper mantle. The Cordillera and other continental backarcs are weak enough to be deformed by plate boundary forces, whereas cratons are generally much too strong. In the Cordillera, the upper mantle is too hot for brittle failure and earthquakes occur only in the upper 10-15 km of the crust. In the cool craton, earthquakes occur rarely in the upper mantle because the total lithosphere strength is too great for significant deformation by plate tectonic forces.

  5. 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.

  6. 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.

  7. From P-T-age to secular change and global tectonic regimes (or Essene in reverse - from granulites to blueschists and eclogites over time)

    NASA Astrophysics Data System (ADS)

    Brown, M.

    2006-12-01

    predominantly Phanerozoic phenomena. HPM-UHPM registers low thermal gradients and deep subduction of continental crust during the early stage of the collision process in Phanerozoic subduction-to-collision orogens. Although counterintuitive, many HPM-UHPM belts appear to have developed by closure of small ocean basins in the process of accretion of a continental terrane during a period of supercontinent introversion (Wilson cycle ocean basin opening and closing). A duality of metamorphic belts - reflecting a duality of thermal regimes - appears in the record only since the Neoarchean Era. A duality of thermal regimes is the hallmark of modern plate tectonics and the duality of metamorphic belts is the characteristic imprint of plate tectonics in the rock record. The occurrence of both G- UHTM and E-HPGM belts since the Neoarchean manifests the onset of a `Proterozoic plate tectonics regime', although the style of tectonics likely involved differences from modern Earth. Although the style of Proterozoic subduction remains cryptic, the change in tectonic regime whereby interactions between discrete lithospheric plates generated tectonic settings with contrasting thermal regimes was a landmark event in Earth history. The `Proterozoic plate tectonics regime' evolved during a Neoproterozoic transition to the `modern plate tectonics regime' characterized by colder subduction, and subduction of continental crust deep into the mantle and its (partial) return from depths of up to 300 km, as chronicled by the appearance of blueschists and HPM-UHPM in the rock record.

  8. 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

  9. Limiting thermal regimes of active disk elements under steady-state pumping and two-dimensional temperature distribution inside the disk

    SciTech Connect

    Alpat'ev, A N; Lis, Denis A; Smirnov, V A; Shcherbakov, Ivan A

    2010-09-10

    An analytic expression describing the stationary two-dimensional axially symmetric temperature distribution in a disk active element (AE) is derived upon pumping the entire disk whose thickness is 0.01 cm {<=} h {<=} 0.3 cm and the diameter-to-thickness ratio is 1 {<=} d/h {<=} 100. Thermomechanical stresses are calculated. It is shown that from the point of view of the disk damage, the tangential stress on the disk side face constitutes the major threat. For different scaling parameters x =d/h, the limiting lasing powers P{sub las} are estimated in multimode approximation, which can be obtained using a disk AE in the case of end and side cooling for different heat exchange coefficients a (by the example of an Nd : YAG crystal). It is found that the side cooling can decrease P{sub las} in some situations. The priority regions are established in the space of the parameters h, x, and a which, while increasing the pump intensity, are accompanied by one of the three events violating the normal operation of the laser: deterioration of spectral and luminescent AE parameters due to heating, malfunctioning of the cooling regime, or thermomechanical damage of the disk. It is shown that an increase in the scaling parameter x smoothes the radial temperature profile and the thermoelastic stress distribution profile. (lasers)

  10. Effects of free air carbon dioxide enrichment and drought stress on the feed value of maize silage fed to sheep at different thermal regimes.

    PubMed

    Lohölter, Malte; Meyer, Ulrich; Manderscheid, Remy; Weigel, Hans-Joachim; Erbs, Martin; Flachowsky, Gerhard; Dänicke, Sven

    2012-08-01

    Information about the effects of rising atmospheric CO2 concentration and drought on the feed value of maize silage and interactions with the thermal environment during feeding is limited. A free air carbon dioxide enrichment facility was operated in a maize field to generate an elevated CO2 concentration of 550 ppm. Drought was induced by the exclusion of precipitation in one half of all experimental plots. Plants were harvested, chopped and ensiled. In a balance experiment on sheep, the nutrient digestibility was determined for three climatic treatments (temperate, temperature humidity index (THI) 57-63; mild heat, THI 68-71; severe heat, THI 75-80). The CO2 concentration and drought did not alter the crude nutrient content of silage dry matter (DM) or nutrient and organic matter (OM) digestibility. Drought increased the concentration of deoxynivalenol (DON, p < 0.001). The drought-associated increase of DON was reduced by CO2 enrichment (p = 0.003). The lowest digestibility of acid detergent fibre (p = 0.024) and neutral detergent fibre (p = 0.005) was observed during the coldest climate. OM digestibility increased during mild heat (p = 0.023). This study did not indicate considerable alterations of the feed value of maize silage due to increased atmospheric CO2 and drought. Enriched CO2 may decrease DON contaminations during drought. The thermal environment during the balance experiment did not interact with feeding maize silage grown under elevated CO2, but may affect cell wall and OM digestibility.

  11. Raising the continental crust

    NASA Astrophysics Data System (ADS)

    Campbell, Ian H.; Davies, D. Rhodri

    2017-02-01

    The changes that occur at the boundary between the Archean and Proterozoic eons are arguably the most fundamental to affect the evolution of Earth's continental crust. The principal component of Archean continental crust is Granite-Greenstone Terranes (GGTs), with granites always dominant. The greenstones consist of a lower sequence of submarine komatiites and basalts, which erupted onto a pre-existing Tonalite-Trondhjemite-Granodiorite (TTG) crust. These basaltic rocks pass upwards initially into evolved volcanic rocks, such as andesites and dacites and, subsequently, into reworked felsic pyroclastic material and immature sediments. This transition coincides with widespread emplacement of granitoids, which stabilised (cratonised) the continental crust. Proterozoic supra-crustal rocks, on the other hand, are dominated by extensive flat-lying platform sequences of mature sediments, which were deposited on stable cratonic basements, with basaltic rocks appreciably less abundant. The siliceous TTGs cannot be produced by direct melting of the mantle, with most hypotheses for their origin requiring them to be underlain by a complimentary dense amphibole-garnet-pyroxenite root, which we suggest acted as ballast to the early continents. Ubiquitous continental pillow basalts in Archean lower greenstone sequences require the early continental crust to have been sub-marine, whereas the appearance of abundant clastic sediments, at higher stratigraphic levels, shows that it had emerged above sea level by the time of sedimentation. We hypothesise that the production of komatiites and associated basalts, the rise of the continental crust, widespread melting of the continental crust, the onset of sedimentation and subsequent cratonisation form a continuum that is the direct result of removal of the continent's dense amphibole-garnet-pyroxenite roots, triggered at a regional scale by the arrival of a mantle plume at the base of the lithosphere. Our idealised calculations suggest

  12. Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

    NASA Astrophysics Data System (ADS)

    Majorowicz, Jacek A.; Embry, Ashton F.

    1998-06-01

    Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15-50 mK/m range (mean = 31 ± 7 mK/m). Present heat flow is mainly in the 35-90 mW/m 2 range (mean = 53 ± 12 mW/m 2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15-50 mK/m (mean = 28 ± 9 mK/m) and paleo-heat flow is in the 40-90 mW/m 2 range (mean = 57 ± 18 mW/m 2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 ± 12 versus 57 ± 18 mW/m 2, respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 ± 7 versus 28 ± 9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that

  13. 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.

  14. The influence of snow cover thickness on the thermal regime of Tête Rousse Glacier (Mont Blanc range, 3200 m a.s.l.): consequences for water storage, outburst flood hazards and glacier response to global warming

    NASA Astrophysics Data System (ADS)

    Gilbert, A.; Vincent, C.; Wagnon, P.; Thibert, E.; Rabatel, A.

    2012-04-01

    Tête Rousse Glacier (French Alps) was responsible for an outburst flood in 1892 that devastated the village of St Gervais-Le Fayet close to Chamonix, causing 175 fatalities. In 2010, geophysical surveys of this glacier revealed a subglacial lake that was subsequently drained artificially. The processes controlling the thermal regime of the glacier have been investigated on the basis of measurements and snow cover and heat flow models using meteorological data covering the last 200 years. Temperature measurements show a polythermal structure with subglacial water trapped by the cold lowest part of the glacier (-2°C). The modeling approach shows that the polythermal structure results mainly from changes in the depth of the snow cover with time at the glacier surface. Paradoxically, periods with negative mass balances, associated with warmer air temperature, tend to cool the glacier because the warmer temperatures reduce the snowpack depth and extent, thereby decreasing the insulation of the glacier from the cold and the amount of latent heat introduced by meltwater refreezing. Conversely years with colder temperatures, associated with positive mass balances, tend to increase the glacier temperature by maintaining a thick snowpack all year round at the glacier surface. The thermal effect of the subglacial lake is evaluated and suggests that the lake existed before 1980. Modeling shows that the glacier will cool again in the future. This study provides insight into the thermal processes responsible for water storage inside a small static glacier which can lead to catastrophic outburst floods such as the 1892 event or potentially dangerous situations as in 2010.

  15. Assessment of extreme hydrological conditions in the Bothnian Bay, Baltic Sea, and the impact of the nuclear power plant "Hanhikivi-1" on the local thermal regime

    NASA Astrophysics Data System (ADS)

    Dvornikov, Anton Y.; Martyanov, Stanislav D.; Ryabchenko, Vladimir A.; Eremina, Tatjana R.; Isaev, Alexey V.; Sein, Dmitry V.

    2017-04-01

    The results of the study aimed to assess the influence of future nuclear power plant Hanhikivi-1 upon the local thermal conditions in the Bothnian Bay in the Baltic Sea are presented. A number of experiments with different numerical models were also carried out in order to estimate the extreme hydro-meteorological conditions in the area of the construction. The numerical experiments were fulfilled both with analytically specified external forcing and with real external forcing for 2 years: a cold year (2010) and a warm year (2014). The study has shown that the extreme values of sea level and water temperature and the characteristics of wind waves and sea ice in the vicinity of the future nuclear power plant can be significant and sometimes catastrophic. Permanent release of heat into the marine environment from an operating nuclear power plant will lead to a strong increase in temperature and the disappearance of ice cover within a 2 km vicinity of the station. These effects should be taken into account when assessing local climate changes in the future.

  16. 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.

  17. Construction of Continental Crust at the Central American and Philippines Arc Systems

    NASA Astrophysics Data System (ADS)

    Whattam, S. A.; Stern, R. J.

    2016-12-01

    Whether or not magmatic arcs evolve compositionally with time and the processes responsible remain controversial. Resolution of this question requires reconstructing arc geochemical evolution at the level of discrete arc systems, as has been done for IBM, Central America, and the Greater Antilles. Emphasis should be on arcs built on oceanic crust because interaction with continental crust complicates interpretations. The Philippines are a particularly attractive target because this may be the best example where proto-continental crust has been generated and processed in Cretaceous and younger time. Here, we show how this question could be addressed for the Philippines using the well-studied Central American Volcanic Arc System (CAVAS) as an example. For the CAVAS, we avoided the northern arc segment because these are (Guatemala) or maybe (El Salvador) sections built on continental crust. Geochemical and isotopic data were compiled for 1031 samples of lavas and intrusive rocks from the 1100 km-long segment built on thickened, initially plume-derived oceanic crust over its 75 million year lifespan (Panama, Costa Rica, Nicaragua) . The most striking observation is the overall evolution of the CAVAS to more incompatible element enriched and ultimately continental-like compositions with time. Models entailing progressive arc magmatic enrichment are generally supported by the CAVAS record. Progressive enrichment of the oceanic CAVAS with time reflects changes in mantle wedge composition and decreased melting due to arc crust thickening, which was kick-started by the involvement of enriched plume mantle. Progressive crustal thickening and associated changes in the sub-arc thermal regime resulted in decreasing degrees of partial melting over time, which allowed for progressive enrichment of the CAVAS and ultimately the production of continental-like crust in Panama and Costa Rica by 16-10 Ma. Our similar study of the Philippine Arc system is in its infancy but earlier

  18. 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)

  19. 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)

  20. 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.

  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. Continental rifting - Progress and outlook

    SciTech Connect

    Baker, B.H.; Morgan, P.

    1981-07-21

    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.

  3. Continental crust formation on early Earth controlled by intrusive magmatism.

    PubMed

    Rozel, A B; Golabek, G J; Jain, C; Tackley, P J; Gerya, T

    2017-05-18

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the "Plutonic squishy lid" tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  4. Continental crust formation on early Earth controlled by intrusive magmatism

    NASA Astrophysics Data System (ADS)

    Rozel, A. B.; Golabek, G. J.; Jain, C.; Tackley, P. J.; Gerya, T.

    2017-05-01

    The global geodynamic regime of early Earth, which operated before the onset of plate tectonics, remains contentious. As geological and geochemical data suggest hotter Archean mantle temperature and more intense juvenile magmatism than in the present-day Earth, two crust-mantle interaction modes differing in melt eruption efficiency have been proposed: the Io-like heat-pipe tectonics regime dominated by volcanism and the “Plutonic squishy lid” tectonics regime governed by intrusive magmatism, which is thought to apply to the dynamics of Venus. Both tectonics regimes are capable of producing primordial tonalite-trondhjemite-granodiorite (TTG) continental crust but lithospheric geotherms and crust production rates as well as proportions of various TTG compositions differ greatly, which implies that the heat-pipe and Plutonic squishy lid hypotheses can be tested using natural data. Here we investigate the creation of primordial TTG-like continental crust using self-consistent numerical models of global thermochemical convection associated with magmatic processes. We show that the volcanism-dominated heat-pipe tectonics model results in cold crustal geotherms and is not able to produce Earth-like primordial continental crust. In contrast, the Plutonic squishy lid tectonics regime dominated by intrusive magmatism results in hotter crustal geotherms and is capable of reproducing the observed proportions of various TTG rocks. Using a systematic parameter study, we show that the typical modern eruption efficiency of less than 40 per cent leads to the production of the expected amounts of the three main primordial crustal compositions previously reported from field data (low-, medium- and high-pressure TTG). Our study thus suggests that the pre-plate-tectonics Archean Earth operated globally in the Plutonic squishy lid regime rather than in an Io-like heat-pipe regime.

  5. Brazilian continental cretaceous

    NASA Astrophysics Data System (ADS)

    Petri, Setembrino; Campanha, Vilma A.

    1981-04-01

    Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.

  6. 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.

  7. 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.

  8. Evolution of continental collision styles since the Precambrian

    NASA Astrophysics Data System (ADS)

    Sizova, Elena; Gerya, Taras; Brown, Michael

    2010-05-01

    from modern style of collision with formation of HP-UHP rocks to a different tectonic regime at upper mantle temperature rising by around 100 - 200 degrees (depending on the lithosphere thickness) above the present value. From this point continental plate subducts and induces the rising of melt-bearing hot mantle in the mantle wedge. The area of the melt-bearing mantle is not big (up to 150 km width) and after some time at the compressional conditions it starts to contract and melt starts to crystallize back. Further increase in the mantle temperature (by around 200-250 degrees above present) causes transition to another regime with the vast amount of melt-bearing mantle areas which give rise to plates sinking into the mantle without any contact with the surface anymore. Based on our experiments there is no big influence on the collision style of density contrast between subcontinental lithospheric and underlying mantles, on the other hand collisional evolution strongly depends on the upper-mantle temperature and lithosphere thickness. The fact that slab breakoff and relaxation of the continental plate leads to melting and detachment of the continental crust from the continental plate is interesting, and may be the mechanism by which the UHP history is erased from gneiss complexes whereas UHP history tends to be preserved in mafic and ultramafic boudins within these complexes (and sometimes within zircons within the gneisses). The transition from the modern style of collision to the determined regime with melt-bearing mantle in the mantle wedge may correspond to disappearing of UHP after 600 Ma in the continental geological record.

  9. Converting your Continental

    SciTech Connect

    Wirz, B.M.

    1981-07-01

    Inflation and higher fuel and environmental costs make conventional-generated power as unaffordable (as a Lincoln Continental in the automobile market) for retail and industrial customers, many of whom are looking for alternatives to purchase electric power. The loss of revenue from competing energy sources eliminates the monopoly status that utilities have enjoyed and is forcing utilities to provide what customers want and do it better than the competition. Utilities have only research and development or fuel switching to improve efficiency unless they rethink their approach and come up with new alternatives. 1 table. (DCK)

  10. 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

  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. Shallow subduction, ridge subduction, and the evolution of continental lithosphere

    SciTech Connect

    Helmstaedt, H.; Dixon, J.M.; Farrar, E.; Carmichael, D.M.

    1985-01-01

    Subduction of oceanic lithosphere beneath continental crust at a shallow angle has occurred throughout the Phanerozoic Eon. Ridge subduction often follows shallow subduction and causes bimodal volcanism and crustal rifting, forming back-arc basins. Recent models for Archean plate tectonics propose very fast rates of spreading (400-800 km/Ma) and convergence, and sinking rates comparable to or slower (<10 km/Ma) than those of today. As faster convergence and slower sinking correspond to subduction at shallower angles, shallow subduction and ridge subduction must have been ubiquitous during the Archean permobile regime. This is compatible with a back-arc-basin origin for Archean greenstone belts. The common coexistence of tholeiitic and calc-alkaline igneous rocks in Archean greenstone belts, also implies ridge subduction. The authors envisage a transition, between 2.4 and 1.8 Ga., from a regime dominated by shallow subduction and repeated ridge subduction to one of normal plate tectonics with steeper subduction. Spreading rates decreased; continental plates became larger and stable shelves could develop at trailing margins. Shallow subduction became the exception, restricted to episodes of abnormally fast convergence; nevertheless, the long span of post-Archean time makes it unlikely that any part of the continental crust has escaped shallow subduction and ridge subduction. These processes recycle much volatile-rich oceanic crust into the sub-continental upper mantle, thereby underplating the crust, effecting upper-mantle metasomatism and affecting intraplate magmatism.

  13. 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.

  14. Ignitability of materials in transitional heating regimes

    Treesearch

    Mark A. Dietenberger

    2004-01-01

    Piloted ignition behavior of materials, particularly wood products, during transitions between heating regimes is measured and modeled in a cone calorimetry (ISO 5660) heating environment. These include (1) effect of material thickness, density, moisture content, and paint coating variations on thermal response characteristics, (2) effect of fire retardant treatment...

  15. The Effect of Temperature Dependent Rheology on a Kinematic Model of Continental Breakup and Rifted Continental Margin Formation

    NASA Astrophysics Data System (ADS)

    Tymms, V. J.; Kusznir, N. J.

    2004-12-01

    The effect of temperature dependent rheology has been examined for a model of continental lithosphere thinning by an upwelling divergent flow field within continental lithosphere and asthenosphere leading to continental breakup and rifted continental margin formation. The model uses a coupled FE fluid flow and thermal solution and is kinematically driven using a half divergence rate Vx and upwelling velocity Vz. Viscosity structure is modified by the evolving temperature field of the model through the temperature dependent Newtonian rheology. Continental lithosphere and asthenosphere material are advected by the fluid-flow field in order to predict crustal and mantle lithosphere thinning leading to rifted continental margin formation. The results of the temperature dependent rheology model are compared with those of a simple isoviscous model. The temperature dependent rheology model predicts continental lithosphere thinning and depth dependent stretching, similar to that predicted by the uniform viscosity model. However compared with the uniform viscosity model the temperature dependent rheology predicts greater amounts of thinning of the continental crust and lithospheric mantle than the isoviscous solutions. An important parameter within the kinematic model of continental lithosphere breakup and rifted continental margin development is the velocity ratio Vz/Vx. For non-volcanic margins, Vz/Vx is thought to be around unity. Applying a velocity ratio Vz/Vx of unity gives a diffuse ocean-continent transition and exhumation of continental lithospheric mantle. For volcanic margins, Vz/Vx is of order 10, falling to unity with a half-life of order 10 Ma, leading to a more sharply defined ocean-continent transition. While Vx during continental breakup may be estimated, Vz can only be inferred. FE fluid flow solutions, in which Vz is not imposed and without an initial buoyancy driven flow component, predict a velocity ratio Vz/Vx of around unity for both temperature

  16. 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.

  17. 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.

  18. 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.

  19. Fractional activation of accumulation-mode particles in warm continental stratiform clouds

    SciTech Connect

    Gillani, N.V.; Daum, P.H.; Schwartz, S.E.; Leaitch, W.R.; Strapp, J.W.; Isaac, G.A.

    1991-07-01

    The degree of activation of accumulation-mode particles (AMP) in clouds has been studied using continuous (1 second average) aircraft measurements of the number concentrations of cloud droplets (N{sub cd}, 2 to 35 {mu}m diameter) and of unactivated AMP (N{sub amp}, 0.17 to 2.07 {mu}m diameter) in cloud interstitial air. The magnitude and spatial variation of the activated fraction (F) of all measured particles (defined as F {triple_bond} N{sub cd}/N{sub tot}, where N{sub tot} = N{sub cd} + N{sub amp}) are investigated, based on measurements made during ten aircraft flights in non-precipitating warm continental stratiform clouds near Syracuse NY in the fall of 1984. Based on instantaneous observations throughout the clouds, the spatial distribution of F was found to be quite nonuniform. In general, F was low in cloud edges and where total particle loading was high and/or cloud convective activity was low. In the interior of clouds, the value of F exceeded 0.9 for 36% of the data, but was below 0.6 for 28%. Factors influencing F the most were the total particle loading (N{sub tot}) and the thermal stability of the cloud layer. The dependence of F on N{sub tot} in cloud interior was characterized by two distinct regimes. For N{sub tot} < 600 cm{sup {minus}3}, F was generally close to unity and relatively insensitive to N{sub tot}. For N{sub tot} > 800 cm{sup {minus}3}, F tended to decrease with increasing N{sub tot}. This decrease was greatest in a stable stratus deck embedded in a warm moist airmass. The results suggest that, in warm continental stratiform clouds, the process of particle activation becomes nonlinear and self-limiting at high particle loading. The degree of this nonlinearity depends on cloud convective activity (thermal instability).

  20. Fractional activation of accumulation-mode particles in warm continental stratiform clouds

    SciTech Connect

    Gillani, N.V. Associates, Inc., St. Louis, MO ); Daum, P.H.; Schwartz, S.E. ); Leaitch, W.R.; Strapp, J.W.; Isaac, G.A. . Cloud Physics Research Div.)

    1991-07-01

    The degree of activation of accumulation-mode particles (AMP) in clouds has been studied using continuous (1 second average) aircraft measurements of the number concentrations of cloud droplets (N[sub cd], 2 to 35 [mu]m diameter) and of unactivated AMP (N[sub amp], 0.17 to 2.07 [mu]m diameter) in cloud interstitial air. The magnitude and spatial variation of the activated fraction (F) of all measured particles (defined as F [triple bond] N[sub cd]/N[sub tot], where N[sub tot] = N[sub cd] + N[sub amp]) are investigated, based on measurements made during ten aircraft flights in non-precipitating warm continental stratiform clouds near Syracuse NY in the fall of 1984. Based on instantaneous observations throughout the clouds, the spatial distribution of F was found to be quite nonuniform. In general, F was low in cloud edges and where total particle loading was high and/or cloud convective activity was low. In the interior of clouds, the value of F exceeded 0.9 for 36% of the data, but was below 0.6 for 28%. Factors influencing F the most were the total particle loading (N[sub tot]) and the thermal stability of the cloud layer. The dependence of F on N[sub tot] in cloud interior was characterized by two distinct regimes. For N[sub tot] < 600 cm[sup [minus]3], F was generally close to unity and relatively insensitive to N[sub tot]. For N[sub tot] > 800 cm[sup [minus]3], F tended to decrease with increasing N[sub tot]. This decrease was greatest in a stable stratus deck embedded in a warm moist airmass. The results suggest that, in warm continental stratiform clouds, the process of particle activation becomes nonlinear and self-limiting at high particle loading. The degree of this nonlinearity depends on cloud convective activity (thermal instability).

  1. 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.

  2. Oceanography of the Southeastern Continental Shelf

    NASA Astrophysics Data System (ADS)

    This volume, the second in the Coastal and Estuarine Sciences series, provides a synthesis of the physical, chemical, and biological oceanography of the South Atlantic Bight (SAB). The results presented derive from a decade-long multidisciplinary investigation of the SAB continental shelf regime.The SAB extends from West Palm Beach, Fla., where the narrow south Florida shelf begins to broaden, to Cape Hatteras, N.C., where the shelf again narrows. This broad and shallow area is distinguished by the proximity of the Gulf Stream to the shelf break. Large contrasts in the distribution of properties, the strength of oceanic and atmospheric forces, and the high frequency (4-12 days) at which these forces vary have created a unique natural laboratory in which a variety of oceanic processes may be studied.

  3. GEWEX Continental-scale International Project (GCIP)

    NASA Technical Reports Server (NTRS)

    Try, Paul

    1993-01-01

    The Global Energy and Water Cycle Experiment (GEWEX) represents the World Climate Research Program activities on clouds, radiation, and land-surface processes. The goal of the program is to reproduce and predict, by means of suitable models, the variations of the global hydrological regime and its impact on atmospheric and oceanic dynamics. However, GEWEX is also concerned with variations in regional hydrological processes and water resources and their response to changes in the environment such as increasing greenhouse gases. In fact, GEWEX contains a major new international project called the GEWEX Continental-scale International Project (GCIP), which is designed to bridge the gap between the small scales represented by hydrological models and those scales that are practical for predicting the regional impacts of climate change. The development and use of coupled mesoscale-hydrological models for this purpose is a high priority in GCIP. The objectives of GCIP are presented.

  4. Back-arc rifting initiated with a hot and wet continental lithosphere

    NASA Astrophysics Data System (ADS)

    Yamasaki, Tadashi; Stephenson, Randell

    2011-02-01

    How back-arc rifting is initiated is studied by inferring the tectonic force and strain rate regimes from published subsidence data for nine back-arc basins in the European Tethyan belt and in the western Pacific. The results show that rifting only begins after some particular magnitude of tectonic force is reached. This implies that subduction has already progressed to a point such that the total negative buoyancy of the slab becomes so large that the relevant tectonic force exceeds its bending strength. Once back-arc rifting has been initiated, the force required to maintain it gradually decays. This indicates that the processes governing back-arc extension are fast enough that lithosphere weakening due to an increase in geothermal gradient exceeds strengthening due to the thermal relaxation and crustal thinning. This is achieved, given currently accepted estimates for the maximum force (≤ 7 TN/m), if the thickness of the thermal lithosphere is significantly less than 125 km and if the lithosphere has a wet rheology, meaning that a weak continental lithosphere is required for the initiation of back-arc rifting. The presence of significant strength in the uppermost mantle is not precluded, but it is not required.

  5. 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.

  6. Numerical modelling of crustal growth at active continental margins: implications for the origin of batholiths

    NASA Astrophysics Data System (ADS)

    Vogt, Katharina; Gerya, Taras; Castro, Antonio

    2010-05-01

    As the dynamics and melt sources for batholith generation still remain controversial a set of numerical experiments has been performed using a 2D geochemical - petrological - thermomechanical numerical code (I2VIS) to study dynamics of crustal growth at an active continental margin. The petrological - thermomechanical model simulates oceanic - continental subduction, based on finite differences and marker in cell techniques. The model accounts for spontaneous slab retreat and bending, dehydration of subducted crust, aqueous fluid transport, partial melting, melt extraction and melt emplacement in form of both extrusive volcanics and intrusive plutons. A set of numerical experiments has been performed by varying the rheological weakening effect imposed by fluids and melts. The results indicate that two major tectonic modes of crustal growth exist: (i) plume - absent and (ii) plume - present regimes. Crustal growth in the plume - absent regime is accomplished dominantly by magma emplacement within the lower crust. Melts are extracted from partially molten rocks located atop the slab (i.e. hydrated mantle, sediments and basalts) and are emplaced within the lower crust in form of laterally extending and crystallizing, flattened batholiths of mainly basaltic to andesitic composition. In the case of a plume - present regime subduction of large quantities of sediments results in the formation of buoyant, silicic plumes composed of partially molten sediments and partially molten basalts with some contribution of hydrated mantle. Subsequently these plumes ascend from the slab and intrude into the crust, where they finally crystallize as intrusive bodies (batholiths) within the upper crust. Additionally, extracted melts from partially molten rocks, which are formed both atop the slab and inside the plumes, are being emplaced within the lower crust, where they extend laterally with time until they crystallize. Consequently, two coupled mechanisms contribute to crustal growth

  7. 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.

  8. 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.

  9. Dynamics of continental accretion

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  10. 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.

  11. Regime Dependant Microphysical Variability in Darwin, Australia

    NASA Astrophysics Data System (ADS)

    Dolan, B.; Rutledge, S. A.; Lang, T. J.

    2010-12-01

    Of utmost importance for global precipitation estimates from satellites such as TRMM and the upcoming Global Precipitation Measurement (GPM) is to understand processes that lead to variability in precipitation on sub-seasonal, seasonal, and climatological scales. Many studies have linked differences in rainfall characteristics such as mean diameter (D0) to sub-seasonal regime variability forced by large scale wind shifts, topography, and continental and maritime convection, across various regions of the globe. Several analyses have tied differences between regimes to differing microphysical processes that drive changes in the drop-size distributions occurring in convective rainfall. For example, decreased ice mass aloft and smaller mean diameters are indicative of warm rain processes, while vigorous ice formation leads to large, melting ice to create large drops. If the microphysical variability in different regimes is characterized and understood, the results could be used to improve satellite precipitation algorithms. The polarimetric, Doppler C-band radar, CPOL, located near Darwin, Australia provides a unique platform to study differences in microphysics between land and ocean, as well as variability between monsoon and break periods. The focus of this study is to examine the microphysical processes occurring in four distinct regimes around Darwin (monsoon-land, monsoon-ocean, break-land, break-ocean), using polarimetric data from CPOL. Analyses such as contoured frequency by altitude (CFADs) diagrams, cumulative distribution functions, and mean profiles of precipitation water mass, precipitation ice mass, reflectivity, differential reflectivity and specific differential phase will aide in understanding the physics of precipitation in these regimes. The formation of precipitation ice aloft, warm rain processes, and the contributions of warm rain and cold cloud processes including melting of ice into large drops, will be linked to differences in D0, rain

  12. Cratonization: a thermal and petrological perspective

    SciTech Connect

    Pollack, H.N.

    1985-01-01

    The long term thermal and tectonic history of the continental lithosphere derives from the processes that lead to crationization. Cratons are characterized by mechanical stability, buoyancy and freeboard, a paucity of magmatism, and deep roots. The process is not slow and gradual, extending over aeons, but rather is relatively rapid, being accomplished in a period on the order of 300-500 Ma; cratonic nuclei existed by the end of the Archean. The essential process is devolatilization of the upper mantle, in associations with major orogenic events, to a depth of about 300 km. Devolatilization has the following effects: 1) it elevates the solidus of the affected lithosphere, making it less vulnerable to subsequent melting, 2) it augments the mechanical strength and stiffness of the region by increasing the activation energy, thereby 3) enhancing the structural stability of the lithosphere, thickening it, and extending to greater depths the region in which conduction is the principal mode of heat transfer, thereby 4) maintaining freeboard by the thermal expansion of the extended lithosphere because of the higher temperatures of the conductive thermal regime, and 5) enhancement of buoyancy by thermal expansion and petrological differentiation. The process of cratonization can be reversed by reintroduction of volatiles for the deeper mantle, or by raising the temperature sufficiently to reach the volatile-free refractory solidus. Mantle metasomatic processes probably promote destabilization by recharging the thick need lithosphere with both volatiles and heat producing isotopes.

  13. 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

  14. 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. © 2015 The Authors.

  15. 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.

  16. -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.

  17. 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.

  18. Regimes of Helium Burning

    NASA Astrophysics Data System (ADS)

    Timmes, F. X.; Niemeyer, J. C.

    2000-07-01

    The burning regimes encountered by laminar deflagrations and Zeldovich von Neumann Döring (ZND) detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts that start with a thermonuclear runaway on the surface of a neutron star and to the thin-shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial direction encounter a transition from the distributed regime to the flamelet regime at a density of ~108 g cm-3. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than ~106 g cm-3. Self-sustained laminar deflagrations traveling in the radial direction cannot exist below this density. Similarly, the planar ZND detonation width becomes larger than the pressure scale height at ~107 g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. In the thin helium shell case, turbulent deflagrations traveling in the lateral or radial direction encounter the distributed regime at densities below ~107 g cm-3 and the flamelet regime at larger densities. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than ~104 g cm-3, indicating that steady state laminar deflagrations cannot form below this density. The planar ZND detonation width becomes larger than the pressure scale height at ~5×104 g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction.

  19. Regimes of Helium Burning

    SciTech Connect

    Timmes, F. X.; Niemeyer, J. C.

    2000-07-10

    The burning regimes encountered by laminar deflagrations and Zeldovich von Neumann Doering [ZND] detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts that start with a thermonuclear runaway on the surface of a neutron star and to the thin-shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial direction encounter a transition from the distributed regime to the flamelet regime at a density of {approx}108 g cm-3. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}106 g cm-3. Self-sustained laminar deflagrations traveling in the radial direction cannot exist below this density. Similarly, the planar ZND detonation width becomes larger than the pressure scale height at {approx}107 g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. In the thin helium shell case, turbulent deflagrations traveling in the lateral or radial direction encounter the distributed regime at densities below {approx}107 g cm-3 and the flamelet regime at larger densities. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}104 g cm-3, indicating that steady state laminar deflagrations cannot form below this density. The planar ZND detonation width becomes larger than the pressure scale height at {approx}5x10{sup 4} g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. (c) 2000 The American Astronomical Society.

  20. Dependency of continental crustal rupture, decompression melt initiation and OCT architecture on lithosphere deformation modes during continental breakup: Numerical experiments

    NASA Astrophysics Data System (ADS)

    Jeanniot, L.; Kusznir, N. J.; Manatschal, G.

    2012-12-01

    During the continental breakup process, the initiation of sea-floor spreading requires both the rupture of the continental crust and the initiation of decompression melting. Using numerical experiments, we investigate how the deformation mode of continental lithosphere thinning and stretching controls the rupture of continental crust and lithospheric mantle, the onset of decompression melting and their relative timing. We use a two dimensional finite element viscous flow model to describe lithosphere and asthenosphere deformation. This flow field is used to advect lithosphere and asthenosphere material and temperature. Decompression melting is predicted using the parameterization scheme of Katz et al. (2003). Consistent with the observations of deformation processes occurring at slow spreading ocean ridges (Cannat, 1996), we assume that the topmost continental and oceanic lithosphere, corresponding to the cooler brittle seismogenic layer, deforms by extensional faulting (which we approximate to pure-shear deformation) and magmatic intrusion. Beneath this topmost lithosphere layer approximately 15-20 km thick, we assume that deformation occurs in response to passive upwelling and thermal and melt buoyancy driven small-scale convection. The relative contribution of these deformation components is parameterised by the ratio Vz/Vx, where Vx is the half spreading rate applied to the topmost lithosphere deformation and Vz is the upwelling velocity associated with the small scale convection. We use a series of numerical experiments to investigate the dependency of continental crust and lithosphere rupture, decompression melt initiation, rifted margin ocean-continent transition architecture and subsidence history on the half-spreading rate Vx, buoyancy driven upwelling rate Vz, the ratio Vz/Vx and upper lithosphere pure-shear width W. Based on the numerical experiment results we explore a polyphase evolution of deformation modes leading to continental breakup, sea

  1. 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

  2. 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).

  3. Bioenergetics of Continental Serpentinites

    NASA Astrophysics Data System (ADS)

    Cardace, D.; Meyer-Dombard, D. R.

    2011-12-01

    Serpentinization is the aqueous alteration of ultramafic (Fe- and Mg-rich) rocks, resulting in secondary mineral assemblages of serpentine, brucite, iron oxyhydroxides and magnetite, talc, and possibly carbonate and silica-rich veins and other minor phases-all depending on the evolving pressure-temperature-composition of the system. The abiotic evolution of hydrogen and possibly organic compounds via serpentinization (McCollom and Bach, 2009) highlights the relevance of this geologic process to carbon and energy sources for the deep biosphere. Serpentinization may fuel life over long stretches of geologic time, throughout the global seabed and in exposed, faulted peridotite blocks (as at Lost City Hydrothermal Field, Kelley et al., 2005), and in obducted oceanic mantle units in ophiolites (e.g., Tiago et al., 2004). Relatively little work has been published on life in continental serpentinite settings, though they likely host a unique resident microbiota. In this work, we systematically model the serpentinizing fluid as an environmental niche. Reported field data for high and moderate pH serpentinizing fluids were modeled from Cyprus, the Philippines, Oman, Northern California, New Caledonia, Yugoslavia, Portugal, Italy, Newfoundland Canada, New Zealand, and Turkey. Values for Gibbs Energy of reaction (ΔGr), kJ per mole of electrons transferred for a given metabolism, are calculated for each field site. Cases are considered both for (1) modest assumptions of 1 nanomolar hydrogen and 1 micromolar methane, based on unpublished data for a similar northern California field site (Cardace and Hoehler, in prep.) and (2) an upper estimate of 10 nanomolar hydrogen and 500 micromolar methane. We survey the feasibility of microbial metabolisms for key steps in the nitrogen cycle, oxidation of sulfur in pyrite, iron oxidation or reduction reactions, sulfate reduction coupled to hydrogen or methane oxidation, methane oxidation coupled to the reduction of oxygen, and

  4. 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

  5. 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.

  6. 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. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  7. 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

  8. Continental rifts and mineral resources

    SciTech Connect

    Burke, K. . Geosciences Dept.)

    1992-01-01

    Continental rifts are widespread and range in age from the present to 3 b.y. Individual rifts may form parts of complex systems as in E. Africa and the Basin and Range. Rifts have originated in diverse environments such as arc-crests, sites of continental collision, collapsing mountain belts and on continents at rest over the mantle circulation pattern. Continental rift resources can be classified by depth of origin: For example, in the Great Dike, Norilsk and Mwadui magma from the mantle is the host. At shallower depths continental crust partly melted above mafic magma hosts ore (Climax, Henderson). Rift volcanics are linked to local hydrothermal systems and to extensive zeolite deposits (Basin and Range, East Africa). Copper (Zambia, Belt), zinc (Red Dog) and lead ores (Benue) are related to hydrothermal systems which involve hot rock and water flow through both pre-rift basement and sedimentary and volcanic rift fill. Economically significant sediments in rifts include coals (the Gondwana of Inida), marine evaporites (Lou Ann of the Gulf of Mexico) and non-marine evaporites (East Africa). Oil and gas in rifts relate to a variety of source, reservoir and trap relations (North Sea, Libya), but rift-lake sediment sources are important (Sung Liao, Bo Hai, Mina, Cabinda). Some ancient iron ores (Hammersley) may have formed in rift lakes but Algoman ores and greenstone belt mineral deposits in general are linked to oceanic and island arc environments. To the extent that continental environments are represented in such areas as the Archean of the Superior and Slave they are Andean Arc environments which today have locally rifted crests (Ecuador, N. Peru). The Pongola, on Kaapvaal craton may, on the other hand represent the world's oldest preserved, little deformed, continental rift.

  9. Mantle plumes and continental tectonics.

    PubMed

    Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

    1992-04-10

    Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

  10. 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.

  11. 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

  12. Spatial and temporal variation of water temperature regimes on the Snoqualmie River network

    Treesearch

    Ashley E. Steel; Colin Sowder; Erin E. Peterson

    2016-01-01

    Although mean temperatures change annually and are highly correlated with elevation, the entire thermal regime on the Snoqualmie River, Washington, USA does not simply shift with elevation or season. Particular facets of the thermal regime have unique spatial patterns on the river network and at particular times of the year. We used a spatially and temporally dense...

  13. 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

  14. 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.

  15. 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.

  16. Evolution of the continental crust.

    PubMed

    Hawkesworth, C J; Kemp, A I S

    2006-10-19

    The continental crust covers nearly a third of the Earth's surface. It is buoyant--being less dense than the crust under the surrounding oceans--and is compositionally evolved, dominating the Earth's budget for those elements that preferentially partition into silicate liquid during mantle melting. Models for the differentiation of the continental crust can provide insights into how and when it was formed, and can be used to show that the composition of the basaltic protolith to the continental crust is similar to that of the average lower crust. From the late Archaean to late Proterozoic eras (some 3-1 billion years ago), much of the continental crust appears to have been generated in pulses of relatively rapid growth. Reconciling the sedimentary and igneous records for crustal evolution indicates that it may take up to one billion years for new crust to dominate the sedimentary record. Combining models for the differentiation of the crust and the residence time of elements in the upper crust indicates that the average rate of crust formation is some 2-3 times higher than most previous estimates.

  17. Evidence for transform margin evolution from the Ivory Coast-Ghana continental margin

    NASA Astrophysics Data System (ADS)

    Mascle, Jean; Blarez, Emmanuel

    1987-03-01

    Results are presented from a recent study (Blarez and Mascle, 1986) of the northern Gulf of Guinea margins, particularly off the eastern Ivory Coast and Ghana, where the continental margin is one of the best-preserved examples of an extinct transform margin. The observations support a four-stage model for transform margin evolution. Tectonically active transform contacts, first between normal continental crusts and then between thinned margins, induce characteristic structures such as pull-apart grabens and shear folds. The next stage, in which thermal exchange between oceanic and continental lithospheres controls a complex subsidence, is followed by the transition to a true intraoceanic fracture zone.

  18. The Hadley and Rossby regimes in a spherical atmosphere

    NASA Technical Reports Server (NTRS)

    Feldstein, S. B.; Clark, J. H. E.

    1985-01-01

    The properties of the steady Hadley and Rossby regimes for a thermally forced rotating fluid on a sphere are studied. The two layer modified geostrophic model is employed which allows for thermal advection by the divergent wind and time dependent static stability. Heating processes are parameterized using the Newtonian approximation and Rayleigh friction is accounted for. The equations are transformed to spectral form using spherical harmonics and then truncated retaining a simple axisymmetric state and initial, one wave. A time independent Hadley circulation is obtained which is neutral to axisymmetric disturbances but unstable to wave like perturbations for intermediate values of the meridional temperature gradient, indicating the existence of both an upper and lower symmetric Hadley regime. An analytical solution for the steady Rossby circulation is determined for values of the meridional temperature gradient where the Hadley regime is unstable. Linear perturbation theory is used to show that within the steady Rossby regime two or more waves cannot exist simultaneously.

  19. 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.

  20. Drift of continental rafts with asymmetric heating.

    PubMed

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

    1972-06-02

    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.

  1. 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.

  2. The structural evolution of the deep continental lithosphere

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Miller, Meghan S.; Moresi, Louis

    2017-01-01

    Continental lithosphere houses the oldest and thickest regions of the Earth's surface. Locked within this deep and ancient rock record lies invaluable information about the dynamics that has shaped and continue to shape the planet. Much of that history has been dominated by the forces of plate tectonics which has repeatedly assembled super continents together and torn them apart - the Wilson Cycle. While the younger regions of continental lithosphere have been subject to deformation driven by plate tectonics, it is less clear whether the ancient, stable cores formed and evolved from similar processes. New insight into continental formation and evolution has come from remarkable views of deeper lithospheric structure using enhanced seismic imaging techniques and the increase in large volumes of broadband data. Some of the most compelling observations are that the continental lithosphere has a broad range in thicknesses (< 100 to > 300 km), has complex internal structure, and that the thickest portion appears to be riddled with seismic discontinuities at depths between 80 and 130 km. These internal structural features have been interpreted as remnants of lithospheric formation during Earth's early history. If they are remnants, then we can attempt to investigate the structure present in the deep lithosphere to piece together information about early Earth dynamics much as is done closer to the surface. This would help delineate between the differing models describing the dynamics of craton formation, particularly whether they formed in the era of modern plate tectonics, a transitional mobile-lid tectonic regime, or are the last fragments of an early, stagnant-lid planet. Our review paper (re)introduces readers to the conceptual definitions of the lithosphere and the complex nature of the upper boundary layer, then moves on to discuss techniques and recent seismological observations of the continental lithosphere. We then review geodynamic models and hypotheses for the

  3. Regimes of turbulence without an energy cascade

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  4. 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

  5. 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.

  6. 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.

  7. Modes of continental decretion in western Canada

    NASA Astrophysics Data System (ADS)

    Cook, F. A.

    2010-12-01

    Between the Archean Slave Province and the Pacific Ocean, the North American continent in Canada appears to have ‘grown’ westward during Paleoproterozoic (Wopmay) and Paleozoic-Mesozoic (Cordilleran) orogenesis. However, results from geological observations combined with regional geophysical surveys lead to interpretations in which pre-orogenic basement in both the Wopmay and the Cordillera projects far beneath proposed ‘accreted’ terranes. In the Wopmay orogen (1.89-1.84 Ga), deep geophysical images indicate that Archean Slave basement projects in the subsurface up to 50 km west of the Medial zone (formerly Wopmay fault), a boundary that was previously interpreted as the transition from Slave basement to accreted terrane basement. The Slave basement appears as a west-tapering tectonic wedge into accreted(?) rocks, consistent with an interpretation by Hildebrand and Bowring (Geology, 1999) that the Archean lithosphere that was formerly west of the wedge broke off and was recycled. In the Cordillera, cross sections of the lithosphere illustrate that lower crustal and upper mantle rocks as much as 2/3 of the distance across the orogen can be stratigraphically, geologically and seismically correlated to the ancient cratonic margin. Retrodeformation of rocks that were deposited on or adjacent to the craton leads to the conclusion that, prior to the onset of terrane accretion, the North American margin and associated rocks projected even farther west (today’s coordinates) - at least as far as the modern margin. Apparently, as flakes of terranes were added to the surface in the western regions of the Cordillera, the North American lithosphere, which may have been foreshortened during contraction, was tectonically and/or thermally eroded from below. As a result, terrane accretion in the Cordillera apparently resulted in a net decretion of continental lithosphere. Together, these observations lead to the interpretation that the processes responsible for

  8. Initiation of continental accretion: metamorphic conditions

    NASA Astrophysics Data System (ADS)

    Clement, Conand; Frederic, Mouthereau; Gianreto, Manatschal; Adbeltif, Lahfid

    2017-04-01

    The physical processes involved at the beginning of the continental collision are largely unknown because they are transient and therefore hardly identifiable from the rock record. Despite the importance of key parameters for understanding mountain building processes, especially the formation of deep mountain roots and their impacts on earthquakes nucleation, rock/fluid transfers and oil/gas resources in the continental crust, observations from the earliest collision stages remain fragmentary. Here, we focus on the example of Taiwan, a young and active mountain belt where the transition from oceanic subduction, accretion of the first continental margin to mature collision can be followed in space and time. We present preliminary results and provide key questions regarding the reconstruction of time-pressure-temperature paths of rocks & fluids to allow discriminating between rift-related thermal/rheological inheritance and burial/heating phases during convergence. Previous studies have focused on peak temperatures analyzed by Raman Spectrometry of Carbonaceous Matter from the deeper structural layers exposed in the Central Range of Taiwan. In the pre-rift sediments, these studies reported a positive gradient from West to Est, and values from <330 to 520 °C. We detect from our preliminary analyses of the Miocene "post-rift" sediments, a trend of increasing temperature from 170 to 340 °C northwards. These temperature data are discussed against key structural features recognized in the field and available low-temperature thermochronological constraints. We show that our RSCM temperatures cannot directly be interpreted in terms of syn-convergence nappe stacking only and must reflect a component of initial (pre-collisional) high-geothermal gradients (up to 60°C/km) known in the region, and higher temperature closer to the pre-rift units. Cross sections and maps with high resolution peak temperatures are in process as well as pressure estimations to determine how the

  9. 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.

  10. 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

  11. Physical oceanography of continental shelves

    SciTech Connect

    Allen, J.S.; Beardlsey, R.C.; Blanton, J.O.; Boicourt, W.C.; Butman, B.; Coachman, L.K.; Huyer, A.; Kinder, T.H.; Royer, T.C.; Schumacher, J.D.

    1983-06-01

    Knowledge of the physical oceanography of continental shelves has increased tremendously in recent years, primarily as a result of new current and hydrographic measurements made in locations where no comparable measurements existed previously. In general, observations from geographically distinct continental shelves have shown that the nature of the flow may vary considerably from region to region. Although some characteristics, such as the response of currents to wind forcing, are common to many shelves, the relative importance of various physical processes in influencing the shelf flow field frequently is different. In the last several years, the scientific literature on shelf studies has expanded rapidly, with that for separate regions, to some extent, developing independently because of the variable role played by different physical effects. Consequently, it seems that a simultaneous review of progress in physical oceanographic research in different shelf regions would be especially useful at this time in order to help assess the overall progress in the field. This multi-author report has been compiled as a result. Included are sections on the physical oceanography of continental shelves, in or off of, the eastern Bering Sea, northern Gulf of Alaska, Pacific Northwest, southern California, west Florida, southeastern US, Middle Atlantic Bight, Georges Bank and Peru. These discussions clearly point to the diverse nature of the dominant physics in several of the regions, as well as to some of the dynamical features they share in common. 390 references, 23 figures.

  12. 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.

  13. 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.

  14. Multiagent simulation of evolutive plate tectonics applied to the thermal evolution of the Earth

    NASA Astrophysics Data System (ADS)

    Combes, M.; Grigné, C.; Husson, L.; Conrad, C. P.; Le Yaouanq, S.; ParenthoëN, M.; Tisseau, C.; Tisseau, J.

    2012-05-01

    The feedback between plate tectonics and mantle convection controls the Earth's thermal evolution via the seafloor age distribution. We therefore designed the MACMA model to simulate time-dependent plate tectonics in a 2D cylindrical geometry with evolutive plate boundaries, based on multiagent systems that express thermal and mechanical interactions. We compute plate velocities using a local force balance and use explicit parameterizations to treat tectonic processes such as trench migration, subduction initiation, continental breakup and plate suturing. These implementations allow the model to update its geometry and thermal state at all times. Our approach has two goals: (1) to test how empirically- and analytically-determined rules for surface processes affect mantle and plate dynamics, and (2) to investigate how plate tectonics impact the thermal regime. Our predictions for driving forces, plate velocities and heat flux are in agreement with independent observations. Two time scales arise for the evolution of the heat flux: a linear long-term decrease and high-amplitude short-term fluctuations due to surface tectonics. We also obtain a plausible thermal history, with mantle temperature decreasing by less than 200 K over the last 3 Gyr. In addition, we show that on the long term, mantle viscosity is less thermally influential than tectonic processes such as continental breakup or subduction initiation, because Earth's cooling rate depends mainly on its ability to replace old insulating seafloor by young thin oceanic lithosphere. We infer that simple convective considerations alone cannot account for the nature of mantle heat loss and that tectonic processes dictate the thermal evolution of the Earth.

  15. Composition of the Continental Crust

    NASA Astrophysics Data System (ADS)

    Rudnick, R. L.; Gao, S.

    2003-12-01

    The Earth is an unusual planet in our solar system in having a bimodal topography that reflects the two distinct types of crust found on our planet. The low-lying oceanic crust is thin (˜7 km on average), composed of relatively dense rock types such as basalt and is young (≤200 Ma old) (see Chapter 3.13). In contrast, the high-standing continental crust is thick (˜40 km on average), is composed of highly diverse lithologies (virtually every rock type known on Earth) that yield an average intermediate or "andesitic" bulk composition (Taylor and McLennan (1985) and references therein), and contains the oldest rocks and minerals yet observed on Earth (currently the 4.0 Ga Acasta gneisses (Bowring and Williams, 1999) and 4.4 Ga detrital zircons from the Yilgarn Block, Western Australia (Wilde et al., 2001)), respectively. Thus, the continents preserve a rich geological history of our planet's evolution and understanding their origin is critical for understanding the origin and differentiation of the Earth.The origin of the continents has received wide attention within the geological community, with hundreds of papers and several books devoted to the topic (the reader is referred to the following general references for further reading: Taylor and McLennan (1985), Windley (1995), and Condie (1997). Knowledge of the age and composition of the continental crust is essential for understanding its origin. Patchett and Samson (Chapter 3.10) review the present-day age distribution of the continental crust and Kemp and Hawkesworth (Chapter 3.11) review secular evolution of crust composition. Moreover, to understand fully the origin and evolution of continents requires an understanding of not only the crust, but also the mantle lithosphere that formed more-or-less contemporaneously with the crust and translates with it as the continents move across the Earth's surface. The latter topic is reviewed in Chapter 2.05.This chapter reviews the present-day composition of the

  16. 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.

  17. 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

  18. A unified continental thickness from seismology and diamonds suggests a melt-defined plate.

    PubMed

    Tharimena, Saikiran; Rychert, Catherine; Harmon, Nicholas

    2017-08-11

    Thick, rigid continents move over the weaker underlying mantle, although geophysical and geochemical constraints on the exact thickness and defining mechanism of the continental plates are widely discrepant. Xenoliths suggest a chemical continental lithosphere ~175 kilometers thick, whereas seismic tomography supports a much thicker root (>250 kilometers) and a gradual lithosphere-asthenosphere transition, consistent with a thermal definition. We modeled SS precursor waveforms from continental interiors and found a 7 to 9% velocity drop at depths of 130 to 190 kilometers. The discontinuity depth is well correlated with the origin depths of diamond-bearing xenoliths and corresponds to the transition from coarse to deformed xenoliths. At this depth, the xenolith-derived geotherm also intersects the carbonate-silicate solidus, suggesting that partial melt defines the plate boundaries beneath the continental interior. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  19. 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…

  20. Chapter 5. Borderlands fire regimes

    Treesearch

    Margot Wilkinson-Kaye; Thomas Swetnam; Christopher R. Baisan

    2006-01-01

    Fire is a keystone process in most natural, terrestrial ecosystems. The vital role that fire plays in controlling the structure of an ecosystem underscores the need for us to increase our knowledge of past and current fire regimes (Morgan and others 1994). Dendrochronological reconstructions of fire histories provide descriptions of past fire regimes across a range of...

  1. TRMM Observations of Convective Regimes in the Amazon

    NASA Technical Reports Server (NTRS)

    Petersen, W. A.; Nesbitt, S. W.; Blakeslee, Robert J.; Hein, P.; Cifelli, R.; Rutledge, S. A.; Arnold, James E. (Technical Monitor)

    2001-01-01

    This study utilizes TRMM satellite precipitation radar, lightning imaging sensor, and passive microwave imager data together with ground-based lightning data to investigate the vertical structure, lightning, and rainfall characteristics of Amazonian and central South American convection for three separate wet-seasons. These characteristics are partitioned as a function of 850 mb zonal wind direction, motivated by observations collected during the six-week TRMM-LBA field campaign. The TRMM-LBA field campaign observations suggest that systematic variations in Amazonian convective vertical structure, lightning, and rainfall are all linked to bimodal variations in the low-level zonal wind (e.g., easterly and westerly regimes). The more spatially and temporally comprehensive TRMM dataset used in this study extends the TRMM-LBA observations by examining regime variability in Amazonian and South American convective structure over a continental scale domain. On a continental-scale, patterns of east and west regime 850 mb winds combined with LIS lightning flash densities suggest the presence of synoptic-scale controls (e.g., intrusion of extratropical frontal systems and interaction with the SACZ) on regional-scale variability in convective vertical structure. TRMM PR, TMI and ground-based lightning data suggest that regional variability in wet-season convective structure is most evident over the southern Amazon, Mato Grosso, Altiplano, southern Brazil, and eastern coastal regions of central and southern South America. Convective vertical structure, rain fall rates, and lightning activity are all more pronounced during easterly (westerly) regimes over the southern Amazon and Mato Grosso (Altiplano, and southern Brazil). Importantly, when considered with case-study results from TRMM-LBA, the systematic differences in convective structure that occur as a function of regime suggest that associated regime-differences may exist in the vertical distribution of diabatic heating

  2. The effects of continental block configuration on the Earth's heat loss

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Moresi, L. N.; Lenardic, A.

    2012-12-01

    The presence of continents on the Earth's surface produces an unusual convective system with parallel mechanisms for losing internal heat: conduction through the stable, continental insulating lid, and a more efficient balance of horizontal advection and vertical conduction in the actively overturning oceanic thermal boundary layer. The resulting thermal network which describes the heat loss behavior of the combined mechanisms can create a buffer which moderates the insulating effect of the continental lid on the Earth's overall heat loss, but only if the deep mantle flow communicates between sub-continental and sub-oceanic regions. If communication is disconnected between the two heat transfer mechanisms, then the continent locally insulates the mantle beneath it causing the subcontinental mantle temperature to increase compared to the sub-oceanic mantle setting the stage for a different global impact on mantle dynamics. The thermal-network theory which describes the two end-member cases does not directly constrain the cross-over between these states; however, the configuration of the insulating lid is expected to play a major role. Here we extend previous 2D work to include multiple continental blocks in various configurations to determine when the mixed-network theory holds and when thermal isolated modes can be produced. The continental blocks were arranged in three configurations while holding the total surface area covered by the blocks constant. The three possible layouts were: (1) a single block centered in the model domain, (2) two blocks of equal size centered in the model domain or (3) four blocks of equal size centered in the 3x3x1 Cartesian model domain. All continental blocks are fixed to the coordinate system; when apart (in the two or four block configuration), the blocks do not move relative to each other, but the mantle is free to move dynamically in all directions via periodic boundary conditions. The total surface area covered by continental

  3. Continental temperature change during Early Eocene hyperthermal events

    NASA Astrophysics Data System (ADS)

    Ziegler, Martin; Abels, Hemmo; de Winter, Nils; Gingerich, Philip; Bernasconi, Stefano

    2015-04-01

    Carbonate clumped isotope thermometry has great potential for solving long-standing questions in paleoclimatology as it provides temperature estimates that are independent from assumptions regarding the isotopic or elemental composition of water from which the carbonate precipitated. The clumped isotope group at ETH has worked towards decreasing the sample size requirements and derived new calibrations for the Kiel method based on synthetic and natural calcites. Here we present results of clumped isotope based continental temperatures across the Paleocene-Eocene Thermal Maximum (PETM). The Bighorn Basin of northwestern Wyoming provides hundreds of meters of excellently exposed river floodplain strata of Paleocene and early Eocene age. Records of the the largest greenhouse-warming episode in this interval of time, were recovered soon after their discovery in deep marine sediments. This has allowed intensive study of the major impact this greenhouse warming event had on continental interior climate. Recently, records of four successive, smaller, transient greenhouse warming events in the early Eocene - ETM2/H1/Elmo, H2, I1, and I2 - were located in the fluvial rock record of the basin. We show that the (summer) temperature excursions during hyperthermal events in continental mid-latitudes were amplified compared to marine temperatures and proportional to the size of associated carbon isotope excursions.

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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}.

  9. Compression-extension transition of continental crust in a subduction zone: A parametric numerical modeling study with implications on Mesozoic-Cenozoic tectonic evolution of the Cathaysia Block

    PubMed Central

    Chan, Lung Sang; Gao, Jian-Feng

    2017-01-01

    The Cathaysia Block is located in southeastern part of South China, which situates in the west Pacific subduction zone. It is thought to have undergone a compression-extension transition of the continental crust during Mesozoic-Cenozoic during the subduction of Pacific Plate beneath Eurasia-Pacific Plate, resulting in extensive magmatism, extensional basins and reactivation of fault systems. Although some mechanisms such as the trench roll-back have been generally proposed for the compression-extension transition, the timing and progress of the transition under a convergence setting remain ambiguous due to lack of suitable geological records and overprinting by later tectonic events. In this study, a numerical thermo-dynamical program was employed to evaluate how variable slab angles, thermal gradients of the lithospheres and convergence velocities would give rise to the change of crustal stress in a convergent subduction zone. Model results show that higher slab dip angle, lower convergence velocity and higher lithospheric thermal gradient facilitate the subduction process. The modeling results reveal the continental crust stress is dominated by horizontal compression during the early stage of the subduction, which could revert to a horizontal extension in the back-arc region, combing with the roll-back of the subducting slab and development of mantle upwelling. The parameters facilitating the subduction process also favor the compression-extension transition in the upper plate of the subduction zone. Such results corroborate the geology of the Cathaysia Block: the initiation of the extensional regime in the Cathaysia Block occurring was probably triggered by roll-back of the slowly subducting slab. PMID:28182640

  10. Compression-extension transition of continental crust in a subduction zone: A parametric numerical modeling study with implications on Mesozoic-Cenozoic tectonic evolution of the Cathaysia Block.

    PubMed

    Zuo, Xuran; Chan, Lung Sang; Gao, Jian-Feng

    2017-01-01

    The Cathaysia Block is located in southeastern part of South China, which situates in the west Pacific subduction zone. It is thought to have undergone a compression-extension transition of the continental crust during Mesozoic-Cenozoic during the subduction of Pacific Plate beneath Eurasia-Pacific Plate, resulting in extensive magmatism, extensional basins and reactivation of fault systems. Although some mechanisms such as the trench roll-back have been generally proposed for the compression-extension transition, the timing and progress of the transition under a convergence setting remain ambiguous due to lack of suitable geological records and overprinting by later tectonic events. In this study, a numerical thermo-dynamical program was employed to evaluate how variable slab angles, thermal gradients of the lithospheres and convergence velocities would give rise to the change of crustal stress in a convergent subduction zone. Model results show that higher slab dip angle, lower convergence velocity and higher lithospheric thermal gradient facilitate the subduction process. The modeling results reveal the continental crust stress is dominated by horizontal compression during the early stage of the subduction, which could revert to a horizontal extension in the back-arc region, combing with the roll-back of the subducting slab and development of mantle upwelling. The parameters facilitating the subduction process also favor the compression-extension transition in the upper plate of the subduction zone. Such results corroborate the geology of the Cathaysia Block: the initiation of the extensional regime in the Cathaysia Block occurring was probably triggered by roll-back of the slowly subducting slab.

  11. Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

    SciTech Connect

    Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.

    1992-01-01

    FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime.

  12. Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

    SciTech Connect

    Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.

    1992-12-31

    FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime.

  13. Earthquakes in stable continental crust

    SciTech Connect

    Johnson, A.C.; Kanter, L.R. )

    1990-03-01

    Earthquakes can strike even in stable crust, well away from the familiar earthquake zones at the edges of tectonic plates, but their mere occurrence is both a source of concern in planning critical facilities such as nuclear power plants. The authors sought answers to two major questions: Just how much seismic activity does take place within the stable parts of continents And are there specific geologic features that make some areas of stable crust particularly susceptible to earthquakes They began by studying North America alone, but it soon became clear that the fairly short record of these rare events on a single continent would not provide enough data for reliable analysis. Hence, they decided to substitute space for time--to survey earthquake frequency and distribution in stable continental areas worldwide. This paper discusses their findings.

  14. Rift asymmetry and continental uplift

    NASA Astrophysics Data System (ADS)

    Doglioni, Carlo; Carminati, Eugenio; Bonatti, Enrico

    2003-06-01

    The topography of ocean ridges and rifts show a distinct asymmetry. The eastern sides of the East Pacific Rise, the Mid-Atlantic Ridge, and the NW Indian Ridge are, on average, 100-300 m more elevated than the conjugate flank to the west. The asymmetry is maintained when bathymetry is plotted versus the square root of crustal age. A comparable topographic asymmetry occurs in the Red Sea and Baikal rifts where the "eastern" continental shoulders are more elevated. We suggest that depleted and lighter asthenosphere generated below the ocean ridge was shifted "eastward" relative to the lithosphere, determining a density deficit below the eastern flank. The eastward migration of the lighter Atlantic asthenosphere below the African continent could eventually have contributed to the anomalous postrift uplift of Africa. This model suggests that the "westward" drift of the lithosphere relative to the underlying mantle might be a global phenomenon.

  15. 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.

  16. 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.

  17. Detecting spatial regimes in ecosystems

    EPA Science Inventory

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological ...

  18. Detecting spatial regimes in ecosystems

    EPA Science Inventory

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological ...

  19. 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)

  20. 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.

  1. 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)

  2. 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.

  3. 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

  4. Plasma confinement regimes and collective modes characterizing them

    SciTech Connect

    Coppi, B.; Zhou, T.

    2012-10-15

    A unified theory is presented for the modes that are excited at the edge of the plasma column and are important signatures of the advanced confinement regimes into which magnetically confined plasmas can be driven. In particular, the so-called EDA H-Regime, the Elmy H-Regime, and the I-Regime are considered. The modes that are identified theoretically have characteristics that are consistent with or have anticipated those of the modes observed experimentally for each of the investigated regimes. The phase velocities, the produced transport processes, the frequencies, the wavelengths, and the consistency with the direction of spontaneous rotation are the factors considered for comparison with the relevant experiments. The quasi-coherent mode [I. Cziegler, Ph.D. dissertation, Massachusetts Institute of Technology, Cambridge, MA, 2011] that is present in the EDA H-Regime has a phase velocity in the direction of the ion diamagnetic velocity in the plasma reference frame. Consequently, this is identified as a ballooning mode near finite Larmor radius marginal stability involving the effects of transverse ion viscosity and other dissipative effects. In this regime, impurities are driven outward by the combined effects of the local temperature gradients of the impurities and their thermal conductivity, while in the Elmy H-Regime impurities are driven toward the center of the plasma column. In the I-Regimes, the excited 'Heavy Particle' modes [B. Coppi and T. Zhou, Phys. Plasmas 19, 012302 (2012); Phys. Lett. A 375, 2916 (2011)] are not of the ballooning kind and are shown to expel the impurities toward the plasma edge in the presence of significant fluctuations. These modes can have a finite frequency of oscillation with a phase velocity in the direction of the electron diamagnetic velocity or they can be nearly purely growing, explaining why there are I-Regimes where fluctuations are not observed. Instead, the modes considered for the Elmy H-Regime are of the ballooning

  5. Continental Growth and the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Dhuime, B.; Hawkesworth, C. J.; Robinson, R. A. J.; Cawood, P. A.

    2014-12-01

    Detrital sedimentary rocks provide average samples of the continental crust formed at different times and in different places. Some materials are more susceptible to erosion and/or to preservation bias than others, and one issue is to understand how the compositions of a range of source rocks are then recorded in the sediments. Here we considered two different approaches to model the growth of the continental crust: (i) The variation of Nd isotopes in continental shales with different deposition ages, which requires a correction of the bias induced by preferential erosion of younger rocks through an erosion parameter usually referred to as 'K'. The determination of K, and the extent to which it varies in different erosion systems, thus have fundamental implications for the models of continental growth based on radiogenic isotopes in continental sediments. (ii) The variations in U-Pb, Hf and O isotopes in detrital zircons, from 'modern' sediments sampled worldwide. In this approach, O isotopes are used to screen 'hybrid' Hf model ages (i.e. ages resulting from mixing processes of crustal material from different ages) from Hf model ages that represent actual crust formation ages. These two approaches independently suggest that the continental crust has been generated continuously, but with a marked decrease in the continental growth rate at ~3 Ga. The >4 Ga to ~3 Ga period is characterised by relatively high net rates of continental growth (~3.0 km3.a-1), which are similar to the rates at which new crust is generated, and destroyed, at the present time. Net growth rates are much lower since 3 Ga (~0.8 km3.a-1), which may be attributed to higher rates of destruction of continental crust. The inflexion in the continental growth curve at ~3 Ga indicates a change in the way the crust was generated and preserved. This change may be linked to onset of subduction-driven plate tectonics and discrete subduction zones.

  6. Multicycle sediments on the continental shelf of Cadiz (SW Spain)

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Mas, J. M.; Moral, J. P.; Sánchez, A.; Dominguez, S.; Muñoz-Perez, J. J.

    2003-07-01

    The study of recent sedimentation in the Gulf of Cadiz continental shelf (SW Europe) is of interest due to its proximity to the Strait of Gibraltar, where the Atlantic and Mediterranean waters are interchanged and the Western Mediterranean Alpidic Orogen closes through the Gibraltar Arch. The existence of relict materials hinders the distinction of the past and present hydrodynamic regimes in present day sediments. An adequate combination of techniques has allowed the establishment of the multicyclic character of the sediments, as well as the stages undergone by the terrigenous grains. Different stages were identified: eolian and energetic fluvial provenance, chemical alterations acquired in a pedological environment, and a marine coastal origin. To verify the source areas, textural and mineralogical features of marine sediments were compared with those found in geological units from fluvial basins. Three zones were differentiated: (a) a sandy littoral, which receives local sediment supplies; (b) a clayey zone between the Guadalquivir River and Cadiz, controlled by contributions from this river provenant of the Iberian Massif and Betic Mountain range; and (c) a sandy continental shelf, between Cadiz and the Cape of Trafalgar, with a low rate of supplies coming from the Guadalete and Barbate rivers, which include materials from the Occidental Betic Mountain range and Neogene units.

  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. Anomalous heat flow belt along the continental margin of Brazil

    NASA Astrophysics Data System (ADS)

    Hamza, Valiya M.; Vieira, Fabio P.; Silva, Raquel T. A.

    2017-06-01

    A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100-300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceará) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that "tectonic bonding" between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth's internal heat at shallow depths.

  9. Influence of dynamic topography on landscape evolution and passive continental margin stratigraphy

    NASA Astrophysics Data System (ADS)

    Ding, Xuesong; Salles, Tristan; Flament, Nicolas; Rey, Patrice

    2017-04-01

    Quantifying the interaction between surface processes and tectonics/deep Earth processes is one important aspect of landscape evolution modelling. Both observations and results from numerical modelling indicate that dynamic topography - a surface expression of time-varying mantle convection - plays a significant role in shaping landscape through geological time. Recent research suggests that dynamic topography also has non-negligible effects on stratigraphic architecture by modifying accommodation space available for sedimentation. In addition, dynamic topography influences the sediment supply to continental margins. We use Badlands to investigate the evolution of a continental-scale landscape in response to transient dynamic uplift or subsidence, and to model the stratigraphic development on passive continental margins in response to sea-level change, thermal subsidence and dynamic topography. We consider a circularly symmetric landscape consisting of a plateau surrounded by a gently sloping continental plain and a continental margin, and a linear wave of dynamic topography. We analyze the evolution of river catchments, of longitudinal river profiles and of the χ values to evaluate the dynamic response of drainage systems to dynamic topography. We calculate the amount of cumulative erosion and deposition, and sediment flux at shoreline position, as a function of precipitation rate and erodibility coefficient. We compute the stratal stacking pattern and Wheeler diagram on vertical cross-sections at the continental margin. Our results indicate that dynamic topography 1) has a considerable influence on drainage reorganization; 2) contributes to shoreline migration and the distribution of depositional packages by modifying the accommodation space; 3) affects sediment supply to the continental margin. Transient dynamic topography contributes to the migration of drainage divides and to the migration of the mainstream in a drainage basin. The dynamic uplift

  10. Change in the circulation regime in the stratified saline Lake Shira (Siberia, Republic of Khakassia)

    NASA Astrophysics Data System (ADS)

    Belolipetskii, V. M.; Degermendzhi, A. G.; Genova, S. N.; Rogozin, D. Y.

    2017-06-01

    The in-situ data on the vertical structure and stability of the vertical stratification of saline Lake Shira over the past decade (2007-2015) are analyzed. Simplified mathematical models have shown that strong wind in the autumn of 2014 together with rather thick ice in the winter of 2015 caused a change in the circulation regime of this water reservoir from meromictic (incomplete mixing) to holomictic (compete mixing). Based on the results obtained, a circulation regime for deep saline lakes located in the continental climate zone, in particular, in the arid zones of Southern Siberia (Khakassia, Transbaikal, and Altai) can be predicted under various climate scenarios of the future.

  11. 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

  12. 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

  13. 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

  14. Magmatic expressions of continental lithosphere removal

    NASA Astrophysics Data System (ADS)

    Wang, Huilin; Currie, Claire A.

    2015-10-01

    Gravitational lithosphere removal in continental interior has been inferred from various observations, including anomalous surface deflections and magmatism. We use numerical models and a simplified theoretical analysis to investigate how lithosphere removal can be recognized in the magmatic record. One style of removal is a Rayleigh-Taylor-type instability, where removal occurs through dripping. The associated magmatism depends on the lithosphere thermal structure. Four types of magmatism are predicted: (1) For relatively hot lithosphere (e.g., back arcs), the lithosphere can be conductively heated and melted during removal, while the asthenosphere upwells and undergoes decompression melting. If removal causes significant lithospheric thinning, the deep crust may be heated and melted. (2) For moderately warm lithosphere (e.g., average Phanerozoic lithosphere) in which the lithosphere root has a low density, only the lithosphere may melt. (3) If the lithosphere root has a high density in moderately warm lithosphere, only asthenosphere melt is predicted. (4) For cold lithosphere (e.g., cratons), no magmatism is induced. An alternate style of removal is delamination, where dense lithosphere peels along Moho. In most cases, the lithosphere sinks too rapidly to melt. However, asthenosphere can upwell to the base of the crust, resulting in asthenospheric and crustal melts. In delamination, magmatism migrates laterally with the detachment point; in contrast, magmatism in Rayleigh-Taylor-type instability has a symmetric shape and converges toward the drip center. The models may explain the diversity of magmatism observed in areas with inferred lithosphere removal, including the Puna Plateau and the southern Sierra Nevada.

  15. 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.

  16. Laboratory Exploration of Multiple Zonal Jet Regimes

    NASA Astrophysics Data System (ADS)

    Smith, C. A.; Speer, K. G.; Griffiths, R. W.

    2012-12-01

    The differentially heated, rotating annulus has classically been used to study wave interactions within a single, baroclinic jet. At high rotation rates, the baroclinic instability of the flow leads to a transition to a turbulent, eddy-dominated regime. In the presence of a topographic beta effect, the flow has been observed to produce multiple, meandering zonal jets that are qualitatively similar to those found in planetary atmospheres and in the Antarctic Circumpolar Current (ACC). Our study builds on previous annulus experiments [1] by making observations further within this new regime. We observe with PIV and other techniques how the structure of the flow responds to changes in various parameters such as tank geometry, gradient in the Coriolis parameter, rotation rate, and differential thermal forcing. By not employing the more typical direct forcing of small scales, but by applying a large scale forcing over the annulus gap width, this study allows the varying effects of eddy scale selection, enstrophy cascade, etc. to naturally generate flow that more closely resembles planetary atmospheres and the ACC. We seek nondimensional parameters that significantly control zonation in a real fluid. These observations will provide a metric for the comparison of various theoretical models for multiple zonal jet formation. Other properties of the jets, such as their migration, meandering, bifurcation, and merging, can also be observed in an idealized situation and compared to numerical simulations. Ultimately, this will aid the testing and development of sub-grid-scale parameterizations for the multiple zonal jet regime that remain robust in the face of multiple forcing parameters. [1] Wordsworth, R. D., Read, P. L., & Yamazaki, Y. H. (2008). Turbulence, waves, and jets in a differentially heated rotating annulus experiment Physics of Fluids, 20(12), 126602.Streak photograph of suspended particles visualizing the flow representative of multiple zonal jets

  17. 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.

  18. Multimode optomechanical system in the quantum regime.

    PubMed

    Nielsen, William Hvidtfelt Padkær; Tsaturyan, Yeghishe; Møller, Christoffer Bo; Polzik, Eugene S; Schliesser, Albert

    2017-01-03

    We realize a simple and robust optomechanical system with a multitude of long-lived (Q > 10(7)) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry-Perot resonator detects these modes' motion with a measurement rate (96 kHz) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures (10 K). Reaching this quantum regime entails, inter alia, quantum measurement backaction exceeding thermal forces and thus strong optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to -2.4 dB (-3.6 dB if corrected for detection losses) and bandwidths ≲90 kHz. The multimode nature of the membrane and Fabry-Perot resonators will allow multimode entanglement involving electromagnetic, mechanical, and spin degrees of freedom.

  19. Multimode optomechanical system in the quantum regime

    NASA Astrophysics Data System (ADS)

    Hvidtfelt Padkær Nielsen, William; Tsaturyan, Yeghishe; Møller, Christoffer Bo; Polzik, Eugene S.; Schliesser, Albert

    2017-01-01

    We realize a simple and robust optomechanical system with a multitude of long-lived (Q > 107) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry–Perot resonator detects these modes’ motion with a measurement rate (96 kHz) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures (10 K). Reaching this quantum regime entails, inter alia, quantum measurement backaction exceeding thermal forces and thus strong optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to ‑2.4 dB (‑3.6 dB if corrected for detection losses) and bandwidths ≲90 kHz. The multimode nature of the membrane and Fabry–Perot resonators will allow multimode entanglement involving electromagnetic, mechanical, and spin degrees of freedom.

  20. 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.

  1. Pulse regime in formation of fractal fibers

    NASA Astrophysics Data System (ADS)

    Smirnov, B. M.

    2016-11-01

    The pulse regime of vaporization of a bulk metal located in a buffer gas is analyzed as a method of generation of metal atoms under the action of a plasma torch or a laser beam. Subsequently these atoms are transformed into solid nanoclusters, fractal aggregates and then into fractal fibers if the growth process proceeds in an external electric field. We are guided by metals in which transitions between s and d-electrons of their atoms are possible, since these metals are used as catalysts and filters in interaction with gas flows. The resistance of metal fractal structures to a gas flow is evaluated that allows one to find optimal parameters of a fractal structure for gas flow propagation through it. The thermal regime of interaction between a plasma pulse or a laser beam and a metal surface is analyzed. It is shown that the basic energy from an external source is consumed on a bulk metal heating, and the efficiency of atom evaporation from the metal surface, that is the ratio of energy fluxes for vaporization and heating, is 10-3-10-4 for transient metals under consideration. A typical energy flux ( 106 W/cm2), a typical surface temperature ( 3000 K), and a typical pulse duration ( 1 μs) provide a sufficient amount of evaporated atoms to generate fractal fibers such that each molecule of a gas flow collides with the skeleton of fractal fibers many times.

  2. Pulse regime in formation of fractal fibers

    SciTech Connect

    Smirnov, B. M.

    2016-11-15

    The pulse regime of vaporization of a bulk metal located in a buffer gas is analyzed as a method of generation of metal atoms under the action of a plasma torch or a laser beam. Subsequently these atoms are transformed into solid nanoclusters, fractal aggregates and then into fractal fibers if the growth process proceeds in an external electric field. We are guided by metals in which transitions between s and d-electrons of their atoms are possible, since these metals are used as catalysts and filters in interaction with gas flows. The resistance of metal fractal structures to a gas flow is evaluated that allows one to find optimal parameters of a fractal structure for gas flow propagation through it. The thermal regime of interaction between a plasma pulse or a laser beam and a metal surface is analyzed. It is shown that the basic energy from an external source is consumed on a bulk metal heating, and the efficiency of atom evaporation from the metal surface, that is the ratio of energy fluxes for vaporization and heating, is 10{sup –3}–10{sup –4} for transient metals under consideration. A typical energy flux (~10{sup 6} W/cm{sup 2}), a typical surface temperature (~3000 K), and a typical pulse duration (~1 μs) provide a sufficient amount of evaporated atoms to generate fractal fibers such that each molecule of a gas flow collides with the skeleton of fractal fibers many times.

  3. 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.

  4. 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.

  5. Potential evapotranspiration and continental drying

    USGS Publications Warehouse

    Milly, Paul C.D.; Dunne, Krista A.

    2016-01-01

    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.

  6. 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-depend