77 FR 24734 - Outer Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-25

... Continental Shelf (OCS) Renewable Energy Program Leasing for Marine Hydrokinetic Technology Testing Offshore... found online at: http://www.boem.gov/Renewable-Energy-Program/State-Activities/Florida.aspx . [[Page.... FOR FURTHER INFORMATION CONTACT: Michelle Morin, BOEM Office of Renewable Energy Programs, 381 Elden...

Dynamics of subduction, accretion, exhumation and slab roll-back: Mediterranean scenarios

NASA Astrophysics Data System (ADS)

Tirel, C.; Brun, J.; Burov, E. B.; Wortel, M. J.; Lebedev, S.

2010-12-01

A dynamic orogen reveals various tectonic processes brought about by subduction: accretion of oceanic and continental crust, exhumation of UHP-HP rocks, and often, back-arc extension. In the Mediterranean, orogeny is strongly affected by slab retreat, as in the Aegean and Tyrrhenian Seas. In order to examine the different dynamic processes in a self-consistent manner, we perform a parametric study using the fully coupled thermo-mechanical numerical code PARAFLAM. The experiments reproduce a subduction zone in a slab pull mode, with accretion of one (the Tyrrhenian case) and two continental blocks (the Aegean case) that undergo, in sequence, thrusting, burial and exhumation. The modeling shows that despite differences in structure between the two cases, the deformation mechanisms are fundamentally similar and can be described as follows. The accretion of a continental block at the trench beneath the suture zone begins with its burial to UHP-HP conditions and thrusting. Then the continental block is delaminated from its subducting lithosphere. During the subduction-accretion process, the angle of the subducting slab increases due to the buoyancy of the continental block. When the oceanic subduction resumes, the angle of the slab decreases to reach a steady-state position. The Aegean and Tyrrhenian scenarios diverge at this stage, due naturally to the differences of their accretion history. When continental accretion is followed by oceanic subduction only, the continental block that has been accreted and detached stays at close to the trench and does not undergo further deformation, despite the continuing rollback. The extensional deformation is located further within the overriding plate, resulting in continental breakup and the development of an oceanic basin, as in the Tyrrhenian domain. When the continental accretion is followed first by oceanic subduction and then by accretion of another continental block, however, the evolution of the subduction zone is different. The angle of the subducting slab increases again, following the arrival of the second continental block. The first continental block is now disconnected from the trench and is strongly heated by the asthenosphere that rises to just below the Moho. The locus of extension, originally in the overriding plate, moves to the first continental block, resulting in the development of metamorphic core complexes, as in the Aegean domain. Simultaneously, the second continent undergoes burial to UHP-HP conditions, thrusting and exhumation.

Continental faunal exchange and the asymmetrical radiation of carnivores.

PubMed

Pires, Mathias M; Silvestro, Daniele; Quental, Tiago B

2015-10-22

Lineages arriving on islands may undergo explosive evolutionary radiations owing to the wealth of ecological opportunities. Although studies on insular taxa have improved our understanding of macroevolutionary phenomena, we know little about the macroevolutionary dynamics of continental exchanges. Here we study the evolution of eight Carnivora families that have migrated across the Northern Hemisphere to investigate if continental invasions also result in explosive diversification dynamics. We used a Bayesian approach to estimate speciation and extinction rates from a substantial dataset of fossil occurrences while accounting for the incompleteness of the fossil record. Our analyses revealed a strongly asymmetrical pattern in which North American lineages invading Eurasia underwent explosive radiations, whereas lineages invading North America maintained uniform diversification dynamics. These invasions into Eurasia were characterized by high rates of speciation and extinction. The radiation of the arriving lineages in Eurasia coincide with the decline of established lineages or phases of climate change, suggesting differences in the ecological settings between the continents may be responsible for the disparity in diversification dynamics. These results reveal long-term outcomes of biological invasions and show that the importance of explosive radiations in shaping diversity extends beyond insular systems and have significant impact at continental scales. © 2015 The Author(s).

Continental faunal exchange and the asymmetrical radiation of carnivores

PubMed Central

Pires, Mathias M.; Silvestro, Daniele; Quental, Tiago B.

2015-01-01

Lineages arriving on islands may undergo explosive evolutionary radiations owing to the wealth of ecological opportunities. Although studies on insular taxa have improved our understanding of macroevolutionary phenomena, we know little about the macroevolutionary dynamics of continental exchanges. Here we study the evolution of eight Carnivora families that have migrated across the Northern Hemisphere to investigate if continental invasions also result in explosive diversification dynamics. We used a Bayesian approach to estimate speciation and extinction rates from a substantial dataset of fossil occurrences while accounting for the incompleteness of the fossil record. Our analyses revealed a strongly asymmetrical pattern in which North American lineages invading Eurasia underwent explosive radiations, whereas lineages invading North America maintained uniform diversification dynamics. These invasions into Eurasia were characterized by high rates of speciation and extinction. The radiation of the arriving lineages in Eurasia coincide with the decline of established lineages or phases of climate change, suggesting differences in the ecological settings between the continents may be responsible for the disparity in diversification dynamics. These results reveal long-term outcomes of biological invasions and show that the importance of explosive radiations in shaping diversity extends beyond insular systems and have significant impact at continental scales. PMID:26490792

Dynamics of Mid-Palaeocene North Atlantic rifting linked with European intra-plate deformations.

PubMed

Nielsen, Søren B; Stephenson, Randell; Thomsen, Erik

2007-12-13

The process of continental break-up provides a large-scale experiment that can be used to test causal relations between plate tectonics and the dynamics of the Earth's deep mantle. Detailed diagnostic information on the timing and dynamics of such events, which are not resolved by plate kinematic reconstructions, can be obtained from the response of the interior of adjacent continental plates to stress changes generated by plate boundary processes. Here we demonstrate a causal relationship between North Atlantic continental rifting at approximately 62 Myr ago and an abrupt change of the intra-plate deformation style in the adjacent European continent. The rifting involved a left-lateral displacement between the North American-Greenland plate and Eurasia, which initiated the observed pause in the relative convergence of Europe and Africa. The associated stress change in the European continent was significant and explains the sudden termination of a approximately 20-Myr-long contractional intra-plate deformation within Europe, during the late Cretaceous period to the earliest Palaeocene epoch, which was replaced by low-amplitude intra-plate stress-relaxation features. The pre-rupture tectonic stress was large enough to have been responsible for precipitating continental break-up, so there is no need to invoke a thermal mantle plume as a driving mechanism. The model explains the simultaneous timing of several diverse geological events, and shows how the intra-continental stratigraphic record can reveal the timing and dynamics of stress changes, which cannot be resolved by reconstructions based only on plate kinematics.

Numerical modeling of Farallon Plate flat-slab subduction: Influence of lithosphere structure and rheology on slab dynamics

NASA Astrophysics Data System (ADS)

Liu, X.; Currie, C. A.

2017-12-01

The subducted Farallon plate is believed to have evolved to a flat geometry underneath North America plate during Late Cretaceous, triggering Laramide deformation within the continental interior. However, the mechanism that caused the oceanic slab to flatten and the factors that control the flat-slab depth remain uncertain. In this work, we use 2D thermal-mechanical models using the SOPALE code to study the subduction dynamics from 90 Ma to 50 Ma. During this period, an oceanic plateau (Shatsky Conjugate) is inferred to have subducted beneath western North America and interacted with the continental lithosphere, including areas of thicker lithosphere such as the Colorado Plateau and Wyoming Craton. Based on seismic tomography and plate reconstruction data sets, we built a set of models to examine the influence of the structure and rheology of the oceanic and continental plates on slab dynamics. Models include a 600 km wide oceanic plateau consisting of 18 km thick crust and a 36 km thick underlying harzburgite layer, and we ran a series of model experiments to test different continental thicknesses (80 km, 120 km, & 180 km) and continental mantle lithosphere strengths (approximating conditions from wet olivine to dry olivine). Consistent with earlier studies, we find that creation of a long flat slab requires a buoyant oceanic plateau (i.e., non-eclogitized crust) and trenchward motion of the continent. In addition, our models demonstrate the upper plate has an important control on slab dynamics. A flat slab requires either a thin continent or, if the continent is thick, its mantle lithosphere must be relatively weak so that it can be displaced by the flattening slab. The depth of the flat slab is mainly controlled by two factors: (1) the continental thickness and (2) the strength of the continental mantle lithosphere. For the same initial lithosphere thickness (120 km), a shallower flat slab ( 90 km depth) occurs for the weakest mantle lithosphere ( wet olivine) compared to 120 km depth for strong ( dry) mantle lithosphere because the flat slab removes the lowermost weak lithosphere. Moreover, an even deeper slab ( 130 km) can be found underneath the weakest but thicker continental lithosphere (180 km). Future models will focus on how the flat slab may induce hydration and deformation for the overriding continental plate.

Estimation of Future PM2.5- and Ozone-related Mortality over the Continental United States in a Changing Climate: An application of High-resolution Dynamical Downscaling Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Jian; Fu, Joshua S.; Huang, Kan

This paper evaluates the PM2.5- and ozone-related mortality at present (2000s) and in the future (2050s) over the continental United States by using the Environmental Benefits Mapping and Analysis Program (BenMAP-CE). Atmospheric chemical fields are simulated by WRF/CMAQ (horizontal resolution: 12 × 12km), applying the dynamical downscaling technique from global climate-chemistry models under the Representative Concentration Pathways scenario (RCP 8.5). Future air quality results predict that the annual mean PM2.5 concentrations in continental US will decrease nationwide, especially in the eastern US and west coast. However, the ozone concentration is projected to decrease in the Eastern US but increase inmore » the Western US. Future mortality is evaluated under two scenarios (1) holding future population and baseline incidence rate at the present level and (2) decreasing the future baseline incidence rate but increasing the future population. For PM2.5, the entire continental US presents a decreasing trend of PM2.5-related mortality by the 2050s in Scenario (1), primarily resulting from the emissions reduction. While in Scenario (2), almost half of the continental states show a rising tendency of PM2.5-related mortality, due to the dominant influence of population growth. In particular, the highest PM2.5-related deaths and the biggest discrepancy between present and future PM2.5-related deaths will both occur in California in 2050s. For the ozone-related premature mortality, the simulation shows nation-wide rising tendency in 2050s under both two scenarios, mainly due to the increase of ozone concentration and population in the future. Furthermore, the uncertainty analysis shows that the effect of the all causes mortality is much larger than for specific causes. This assessment is the result of the accumulated uncertainty of generating datasets. The uncertainty range of ozone-related all cause premature mortality is narrower than the PM2.5-related all cause mortality, due to its smaller standard deviation of beta parameter.« less

The Continental Project: A Model Program for School to Work Transition for Students with Disabilities.

ERIC Educational Resources Information Center

Peterson, Patricia; Ellsworth, J'Anne; Penny, Dave

The Continental Project is a school-to-work transition program for students with disabilities. The 6-year old program, which is located at a country club and golf course, serves more than 20 students per year and has successfully transitioned 45 young adults with moderate to severe handicaps into the workforce. The program is a cooperative effort…

Continental underplating after slab break-off

NASA Astrophysics Data System (ADS)

Magni, V.; Allen, M. B.; van Hunen, J.; Bouilhol, P.

2017-09-01

We present three-dimensional numerical models to investigate the dynamics of continental collision, and in particular what happens to the subducted continental lithosphere after oceanic slab break-off. We find that in some scenarios the subducting continental lithosphere underthrusts the overriding plate not immediately after it enters the trench, but after oceanic slab break-off. In this case, the continental plate first subducts with a steep angle and then, after the slab breaks off at depth, it rises back towards the surface and flattens below the overriding plate, forming a thick horizontal layer of continental crust that extends for about 200 km beyond the suture. This type of behaviour depends on the width of the oceanic plate marginal to the collision zone: wide oceanic margins promote continental underplating and marginal back-arc basins; narrow margins do not show such underplating unless a far field force is applied. Our models show that, as the subducted continental lithosphere rises, the mantle wedge progressively migrates away from the suture and the continental crust heats up, reaching temperatures >900 °C. This heating might lead to crustal melting, and resultant magmatism. We observe a sharp peak in the overriding plate rock uplift right after the occurrence of slab break-off. Afterwards, during underplating, the maximum rock uplift is smaller, but the affected area is much wider (up to 350 km). These results can be used to explain the dynamics that led to the present-day crustal configuration of the India-Eurasia collision zone and its consequences for the regional tectonic and magmatic evolution.

Quaternary geophysical framework of the northeastern North Carolina coastal system

USGS Publications Warehouse

Thieler, E.R.; Foster, D.S.; Mallinson, D.M.; Himmelstoss, E.A.; McNinch, J.E.; List, J.H.; Hammar-Klose, E.S.

2013-01-01

The northeastern North Carolina coastal system, from False Cape, Virginia, to Cape Lookout, North Carolina, has been studied by a cooperative research program that mapped the Quaternary geologic framework of the estuaries, barrier islands, and inner continental shelf. This information provides a basis to understand the linkage between geologic framework, physical processes, and coastal evolution at time scales from storm events to millennia. The study area attracts significant tourism to its parks and beaches, contains a number of coastal communities, and supports a local fishing industry, all of which are impacted by coastal change. Knowledge derived from this research program can be used to mitigate hazards and facilitate effective management of this dynamic coastal system.

The Lithospheric Geoid as a Constraint on Plate Dynamics

NASA Astrophysics Data System (ADS)

Richardson, R. M.; Coblentz, D. D.

2015-12-01

100 years after Wegener's pioneering work there is still considerable debate about the dynamics of present-day plate motions. A better understanding of present-day dynamics is key to a better understanding of the supercontinent cycle. The Earth's gravity field is one of the primary data sets to help constrain horizontal density contrasts, and hence plate dynamic forces. Previous work has shown that the global average for the geoid step up from old oceanic lithosphere across passive continental margins to stable continental lithosphere is about 6-9m, and the global average for the geoid anomaly associated with cooling oceanic lithosphere (the so-called "ridge push") is 10-12m. The ridge geoid anomaly corresponds to a net force of ~3x1012N/m (averaged over the thickness of the lithosphere) due to 'ridge push.' However, for individual continental margins and mid-ocean ridge systems, there is considerable variation in the geoid step and geoid anomaly and consequently the associated forces contributing to the stress field. We explore the variation in geoid step across passive continental margins looking for correlations with age of continental breakup (and hence place within the supercontinent cycle), hot spot tracks, continental plate velocities, long-wavelength geoid energy (that may be masking signal), and small scale convection. For mid-ocean ridges, we explore variations in geoid anomaly looking for correlations with plate spreading rates, hot spot tracks, long-wavelength geoid energy (that may be masking signal), and small scale convection. We use a band-pass spherical harmonic filter on the full geoid (e.g., EGM2008-WGS84, complete to spherical harmonic degree and order 2159) between orders 6 and 80. The evaluation of the role of spatial variations in the geoid gradient for cooling oceanic lithosphere and across the continental margin in the dynamics of the intraplate stress field requires high spatial resolution modeling. We perform a high resolution finite element analysis (~35,000 elements for a spatial resolution of approximately 50 km) for the North American plate, where previous lower resolution modeling has shown the importance of the lithospheric cooling (ridge push) force to model the broad scale stress patterns observed from the middle of the continent to the Mid-Atlantic ridge.

Regional magnetic anomaly constraints on continental breakup

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1986-01-01

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

75 FR 16833 - Preliminary Revised 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2007-2012

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... Continental Shelf (OCS) Oil and Gas Leasing Program for 2007-2012 AGENCY: Minerals Management Service... (MMS) requests comments on the Preliminary Revised 5-Year OCS Oil and Gas Leasing Program for 2007... Elden Street, MS-4010; Herndon, Virginia 20170-4817. Please reference ``Remand of the 2007-2012 OCS Oil...

Drought Prediction Site Specific and Regional up to Three Years in Advance

NASA Astrophysics Data System (ADS)

Suhler, G.; O'Brien, D. P.

2002-12-01

Dynamic Predictables has developed proprietary software that analyzes and predicts future climatic behavior based on past data. The programs employ both a regional thermodynamic model together with a unique predictive algorithm to achieve a high degree of prediction accuracy up to 36 months. The thermodynamic model was developed initially to explain the results of a study on global circulation models done at SUNY-Stony Brook by S. Hameed, R.G. Currie, and H. LaGrone (Int. Jour. Climatology, 15, pp.852-871, 1995). The authors pointed out that on a time scale of 2-70 months the spectrum of sea level pressure is dominated by the harmonics and subharmonics of the seasonal cycle and their combination tones. These oscillations are fundamental to an understanding of climatic variations on a sub-regional to continental basis. The oscillatory nature of these variations allows them to be used as broad based climate predictors. In addition, they can be subtracted from the data to yield residuals. The residuals are then analyzed to determine components that are predictable. The program then combines both the thermodynamic model results (the primary predictive model) with those from the residual data (the secondary model) to yield an estimate of the future behavior of the climatic variable. Spatial resolution is site specific or aggregated regional based upon appropriate length (45 years or more monthly data) and reasonable quality weather observation records. Most climate analysis has been based on monthly time-step data, but time scales on the order of days can be used. Oregon Climate Division 1 (Coastal) precipitation provides an example relating DynaPred's method to nature's observed elements in the early 2000s. The prediction's leading dynamic factors are the strong seasonal in the primary model combined with high secondary model contributions from planet Earth's Chandler Wobble (near 15 months) and what has been called the Quasi-Triennial Oscillation (QTO, near 36 months) in equatorial regions. Examples of regional aggregate and site-specific predictions previously made blind forward and publicly available (AASC Annual Meetings 1998-2002) will be shown. Certain climate dynamics features relevant to extrema prediction and specifically drought prediction will then be discussed. Time steps presented will be monthly. Climate variables examined are mean temperature and accumulated precipitation. NINO3 SST, interior continental and marine/continental transition area examples will be shown. http://www.dynamicpredictables.com

Summaries of FY 1993 geosciences research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-12-01

The Department of Energy supports research in the geosciences in order to provide a sound foundation of fundamental knowledge in those areas of the geosciences that are germane to the DOE`s many missions. The Geosciences Research Program is supported by the Office of Energy Research. The participants in this program include DOE laboratories, academic institutions, and other governmental agencies. These activities are formalized by a contract or grant between the DOE and the organization performing the work, providing funds for salaries, equipment, research materials, and overhead. The summaries in this document, prepared by the investigators, describe the scope of themore » individual programs. The Geosciences Research Program includes research in geophysics, geochemistry, resource evaluation, solar-terrestrial interactions, and their subdivisions including earth dynamics, properties of earth materials, rock mechanics, underground imaging, rock-fluid interactions, continental scientific drilling, geochemical transport, solar-atmospheric physics, and modeling, with emphasis on the interdisciplinary areas.« less

USArray Imaging of North American Continental Crust

NASA Astrophysics Data System (ADS)

Ma, Xiaofei

The layered structure and bulk composition of continental crust contains important clues about its history of mountain-building, about its magmatic evolution, and about dynamical processes that continue to happen now. Geophysical and geological features such as gravity anomalies, surface topography, lithospheric strength and the deformation that drives the earthquake cycle are all directly related to deep crustal chemistry and the movement of materials through the crust that alter that chemistry. The North American continental crust records billions of years of history of tectonic and dynamical changes. The western U.S. is currently experiencing a diverse array of dynamical processes including modification by the Yellowstone hotspot, shortening and extension related to Pacific coast subduction and transform boundary shear, and plate interior seismicity driven by flow of the lower crust and upper mantle. The midcontinent and eastern U.S. is mostly stable but records a history of ancient continental collision and rifting. EarthScope's USArray seismic deployment has collected massive amounts of data across the entire United States that illuminates the deep continental crust, lithosphere and deeper mantle. This study uses EarthScope data to investigate the thickness and composition of the continental crust, including properties of its upper and lower layers. One-layer and two-layer models of crustal properties exhibit interesting relationships to the history of North American continental formation and recent tectonic activities that promise to significantly improve our understanding of the deep processes that shape the Earth's surface. Model results show that seismic velocity ratios are unusually low in the lower crust under the western U.S. Cordillera. Further modeling of how chemistry affects the seismic velocity ratio at temperatures and pressures found in the lower crust suggests that low seismic velocity ratios occur when water is mixed into the mineral matrix, and the combination of high temperature and water may point to small amounts of melt in the lower crust of Cordillera.

Along-slope variability of barotropic transport in the Nordic Seas: Simplified dynamics tested against observations

NASA Astrophysics Data System (ADS)

Aaboe, S.; NøSt, O. A.; Hansen, E.

2009-03-01

The present study combines simple geostrophic considerations and observational data to examine the along-slope evolution of the barotropic transport following the continental slope in the Nordic Seas and Arctic Ocean. Following geostrophic theory, the transport evolution is calculated from bottom densities in five different transects within the Nordic Seas. This theoretically predicted transport evolution is compared with transports estimated directly from velocity measurements. Between the Faroe-Shetland Channel and the Svinøy section off southern Norway, across the Fram Strait (below 800 m), and between the Fram Strait and the Greenland Sea the agreement is generally good between geostrophic theory and observations. This indicates that many aspects of the barotropic flow in these regions are captured by geostrophic dynamics. Between the eastern and western Fram Strait above 800 m and between Svinøy and the eastern Fram Strait the observed flow fields differ to a large extent from the flow field predicted by geostrophic dynamics, indicating that ageostrophic dynamics play a more important role in these regions. The barotropic transport differences between the eastern and western Fram Strait contain information about the barotropic transport evolution along the entire Arctic continental slope. The good agreement between observations and theory across the strait (below 800 m) therefore indicates that the flow along the deeper part of the Arctic continental slope is well described by geostrophic dynamics. According to our results, the noticeably more baroclinic nature of the flow in the western Fram Strait, compared with the eastern strait, can then be ascribed to water mass modifications along the Arctic continental slope.

Carbon Dynamics on the Louisiana Continental Shelf and Cross-Shelf Feeding of Hypoxia

EPA Science Inventory

Large-scale hypoxia regularly develops during the summer on the Louisiana continental shelf. Traditionally, hypoxia has been linked to the vast winter and spring nutrient inputs from the Mississippi River and its distributary, the Atchafalaya River. However, recent studies indica...

Spatiotemporal chlorophyll-a dynamics on the Louisiana continental shelf derived from a dual satellite imagery algorithm

EPA Science Inventory

A monthly time series of remotely sensed chlorophyll-a (Chlars) over the Louisiana continental shelf (LCS) was developed and examined for its relationship to river discharge, nitrate concentration, total phosphorus concentration, photosynthetically available radiation (PAR), wind...

The Athabasca Granulite Terrane and Evidence for Dynamic Behavior of Lower Continental Crust

NASA Astrophysics Data System (ADS)

Dumond, Gregory; Williams, Michael L.; Regan, Sean P.

2018-05-01

Deeply exhumed granulite terranes have long been considered nonrepresentative of lower continental crust largely because their bulk compositions do not match the lower crustal xenolith record. A paradigm shift in our understanding of deep crust has since occurred with new evidence for a more felsic and compositionally heterogeneous lower crust than previously recognized. The >20,000-km2 Athabasca granulite terrane locally provides a >700-Myr-old window into this type of lower crust, prior to being exhumed and uplifted to the surface between 1.9 and 1.7 Ga. We review over 20 years of research on this terrane with an emphasis on what these findings may tell us about the origin and behavior of lower continental crust, in general, in addition to placing constraints on the tectonic evolution of the western Canadian Shield between 2.6 and 1.7 Ga. The results reveal a dynamic lower continental crust that evolved compositionally and rheologically with time.

Measurement of sediment and crustal thickness corrected RDA for 2D profiles at rifted continental margins: Applications to the Iberian, Gulf of Aden and S Angolan margins

NASA Astrophysics Data System (ADS)

Cowie, Leanne; Kusznir, Nick

2014-05-01

Subsidence analysis of sedimentary basins and rifted continental margins requires a correction for the anomalous uplift or subsidence arising from mantle dynamic topography. Whilst different global model predictions of mantle dynamic topography may give a broadly similar pattern at long wavelengths, they differ substantially in the predicted amplitude and at shorter wavelengths. As a consequence the accuracy of predicted mantle dynamic topography is not sufficiently good to provide corrections for subsidence analysis. Measurements of present day anomalous subsidence, which we attribute to mantle dynamic topography, have been made for three rifted continental margins; offshore Iberia, the Gulf of Aden and southern Angola. We determine residual depth anomaly (RDA), corrected for sediment loading and crustal thickness variation for 2D profiles running from unequivocal oceanic crust across the continental ocean boundary onto thinned continental crust. Residual depth anomalies (RDA), corrected for sediment loading using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average or from anomalous uplift or subsidence. Gravity anomaly inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic reflection data has been used to determine Moho depth, calibrated using seismic refraction, and oceanic crustal basement thickness. Crustal basement thicknesses derived from gravity inversion together with Airy isostasy have been used to correct for variations of crustal thickness from a standard oceanic thickness of 7km. The 2D profiles of RDA corrected for both sediment loading and non-standard crustal thickness provide a measurement of anomalous uplift or subsidence which we attribute to mantle dynamic topography. We compare our sediment and crustal thickness corrected RDA analysis results with published predictions of mantle dynamic topography from global models.

Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 4. User's manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The final report for the project is presented in five volumes. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism in California. This volume is the User's Guide. It includes the following topics: Introduction and Summary Guide; Input Data Files; Gravity Model Programs; Economic Effects Model Programs; Consumer Surplus Model Programs; References; and Appendices.

Microbial Communities in Sediments across the Louisiana Continental Shelf

EPA Science Inventory

The Louisiana continental Shelf (LCS) is a dynamic system that receives discharges from two large rivers. It has a stratified water column that is mixed by winter storms, hypoxic bottom water from spring to fall, and a muddy seafloor with highly mixed surficial sediments. Spatia...

Progress towards Continental River Dynamics modeling

NASA Astrophysics Data System (ADS)

Yu, Cheng-Wei; Zheng, Xing; Liu, Frank; Maidment, Daivd; Hodges, Ben

2017-04-01

The high-resolution National Water Model (NWM), launched by U.S. National Oceanic and Atmospheric Administration (NOAA) in August 2016, has shown it is possible to provide real-time flow prediction in rivers and streams across the entire continental United States. The next step for continental-scale modeling is moving from reduced physics (e.g. Muskingum-Cunge) to full dynamic modeling with the Saint-Venant equations. The Simulation Program for River Networks (SPRNT) provides a computational approach for the Saint-Venant equations, but obtaining sufficient channel bathymetric data and hydraulic roughness is seen as a critical challenge. However, recent work has shown the Height Above Nearest Drainage (HAND) method can be applied with the National Elevation Dataset (NED) to provide automated estimation of effective channel bathymetry suitable for large-scale hydraulic simulations. The present work examines the use of SPRNT with the National Hydrography Dataset (NHD) and HAND-derived bathymetry for automated generation of rating curves that can be compared to existing data. The approach can, in theory, be applied to every stream reach in the NHD and thus provide flood guidance where none is available. To test this idea we generated 2000+ rating curves in two catchments in Texas and Alabama (USA). Field data from the USGS and flood records from an Austin, Texas flood in May 2015 were used as validation. Large-scale implementation of this idea requires addressing several critical difficulties associated with numerical instabilities, including ill-posed boundary conditions generated in automated model linkages and inconsistencies in the river geometry. A key to future progress is identifying efficient approaches to isolate numerical instability contributors in a large time-space varying solution. This research was supported in part by the National Science Foundation under grant number CCF-1331610.

A novel representation of groundwater dynamics in large-scale land surface modelling

NASA Astrophysics Data System (ADS)

Rahman, Mostaquimur; Rosolem, Rafael; Kollet, Stefan

2017-04-01

Land surface processes are connected to groundwater dynamics via shallow soil moisture. For example, groundwater affects evapotranspiration (by influencing the variability of soil moisture) and runoff generation mechanisms. However, contemporary Land Surface Models (LSM) generally consider isolated soil columns and free drainage lower boundary condition for simulating hydrology. This is mainly due to the fact that incorporating detailed groundwater dynamics in LSMs usually requires considerable computing resources, especially for large-scale applications (e.g., continental to global). Yet, these simplifications undermine the potential effect of groundwater dynamics on land surface mass and energy fluxes. In this study, we present a novel approach of representing high-resolution groundwater dynamics in LSMs that is computationally efficient for large-scale applications. This new parameterization is incorporated in the Joint UK Land Environment Simulator (JULES) and tested at the continental-scale.

Comprehensive lake dynamics mapping at continental scales using Landsat 8

USDA-ARS?s Scientific Manuscript database

Inland lakes, important water resources, play a crucial role in the global water cycle and are sensitive to global warming and human activities. There clearly is a pressing need to understand temporal and spatial variations of lakes at global and continental scales. The recent operation of Landsat...

Continent-continent collision in southern Alps studied

NASA Astrophysics Data System (ADS)

Henyey, T.; Stern, T.; Molnar, P.

Developing a scientific plan for geophysical study of the Southern Alps, New Zealand, was the focus of a workshop convened from April 5 to 10 at Victoria University in Wellington, New Zealand. The study is a cooperative effort between U.S. and New Zealand scientists. The workshop was convened by F. Davey, Institute for Geological and Nuclear Sciences, Wellington, New Zealand; T. Stern, Victoria University, Wellington; and T. Henyey and D. Okaya, University of Southern California, Los Angeles. It was sponsored by the National Science Foundation Continental Dynamics Program with assistance from the New Zealand Institute of Geological and Nuclear Sciences and Victoria University.

Sea Level Change due to Time-Dependent Long-Wavelength Dynamic Topography Inferred from Plate Tectonic Reconstructions

NASA Astrophysics Data System (ADS)

Conrad, Clinton P.; Steinberger, Bernhard; Torsvik, Trond H.

2017-04-01

Earth's surface is deflected vertically by stresses associated with convective mantle flow. Although dynamic topography is important for both sea level change and continental uplift and subsidence, the time history of dynamic topography is difficult to constrain because the time-dependence of mantle flow is not known. However, the motions of the tectonic plates contain information about the mantle flow patterns that drive them. In particular, we show that the longest wavelengths of mantle flow are tightly linked to the dipole and quadrupole moments (harmonic degrees 1 and 2) of plate motions. This coupling allows us to infer patterns of long-wavelength mantle flow, and the associated dynamic topography, from tectonic plate motions. After calibrating this linkage using models of present-day mantle flow, we can use reconstructions of global plate motions to infer the basic patterns of long-wavelength dynamic topography back to 250 Ma. We find relatively stable dynamic uplift persists above large-scale mantle upwelling beneath Africa and the Central Pacific. Regions of major downwelling encircled the periphery of these stable upwellings, alternating between primarily east-west and north-south orientations. The amplitude of long-wavelength dynamic topography was likely largest in the Cretaceous, when global plate motions were fastest. Continental motions over this time-evolving dynamic topography predict patterns of continental uplift and subsidence that are confirmed by geological observations of continental surfaces relative to sea level. Net uplift or subsidence of the global seafloor can also induce eustatic sea level changes. We infer that dispersal of the Pangean supercontinent away from stable upwelling beneath Africa may have exposed the seafloor to an increasingly larger area of growing positive dynamic topography during the Mesozoic. This net uplift of the seafloor caused 60 m of sea level rise during the Triassic and Jurassic, ceasing in the Cenozoic once continents fully override degree-2 downwellings. These sea level changes represent a significant component of the estimated 200 m of sea level variations during the Phanerozoic, which exhibit a similar temporal pattern.

Mapping continental-scale biomass burning and smoke palls from the space shuttle

NASA Technical Reports Server (NTRS)

Lulla, Kamlesh; Helfert, Michael

1992-01-01

Space shuttle photographs have been used to map the areal extent of Amazonian smoke palls associated with biomass burning. Areas covered with smoke have increased from approximately 300,000 sq km to continental-size smoke palls of approximately 3,000,000 sq km. The smoke palls interpreted from the STS-48 data indicate that this phenomenon is persistent. Astronaut observations of such dynamic and vital environmental phenomena indicate the possibility of intergrating the earth observation capabilities of all space platforms in future modeling of the earth's dynamic processes.

Assessment of the U. S. outer continental shelf environmental studies program. 1. Physical oceanography. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Federal responsibility for oil and gas development on the U.S. outer continental shelf (OCS) resides with the Minerals Management Service (MMS) of the U.S. Department of the Interior (DOI). The DOI's Environmental Studies Program (ESP) is the program through which MMS conducts environmental studies on the OCS and collects information to prepare environmental impact statements (EISs). It appeared to MMS in 1986 that the time was ripe to assess the status of the present program and to explore the needs for future studies. MMS requested an evaluation of the adequacy and applicability of ESP studies, a review of the generalmore » state of knowledge in the appropriate disciplines, and recommendations for future studies. Three panels were established, one of which, the Physical Oceanography Panel, investigated the physical oceanographic aspects of the ESP, the subject of the report, which is the first of three in a series. In reviewing the ESP's physical oceanography program, the panel evaluated the quality and relevance of studies carried out in waters under federal control, which extend from the limits of state jurisdictions (3-12 miles offshore) and include the central and outer continental shelf waters and the continental slope.« less

Predicting and testing continental vertical motion histories since the Paleozoic

NASA Astrophysics Data System (ADS)

Zhang, Nan; Zhong, Shijie; Flowers, Rebecca M.

2012-02-01

Dynamic topography at the Earth's surface caused by mantle convection can affect a range of geophysical and geological observations including bathymetry, sea-level change, continental flooding, sedimentation and erosion. These observations provide important constraints on and test of mantle dynamic models. Based on global mantle convection models coupled with the surface plate motion history, we compute dynamic topography and its history for the last 400 Ma associated with Pangea assembly and breakup, with particular focus on cratonic regions. We propose that burial-unroofing histories of cratons inferred from thermochronology data can be used as a new diagnostic to test dynamic topography and mantle dynamic models. Our models show that there are currently two broad dynamic topography highs in the Pacific and Africa for the present-day Earth that are associated with the broad, warm structures (i.e., superplumes) in the deep mantle, consistent with previous proposals of dynamical support for the Pacific and African superswells. Our models reveal that Pangea assembly and breakup, by affecting subduction and mantle upwelling processes, have significant effects on continental vertical motions. Our models predict that the Slave craton in North America subsides before Pangea assembly at 330 Ma but uplifts significantly from 330 Ma to 240 Ma in response to pre-Pangea subduction and post-assembly mantle warming. The Kaapvaal craton of Africa is predicted to undergo uplift from ~180 Ma to 90 Ma after Pangea breakup, but its dynamic topography remains stable for the last 90 Ma. The predicted histories of elevation change for the Slave and Kaapvaal cratons compare well with the burial-unroofing histories inferred from thermochronology studies, thus supporting our dynamic models including the development of the African superplume mantle structure. The vertical motion histories for other cratons can provide further tests of and constraints on our mantle dynamic models.

Plankton community respiration, net ecosystem metabolism, and oxygen dynamics on the Louisiana continental shelf: implications for hypoxia

EPA Science Inventory

We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column metabolism and the formation of hypoxia (dissolved oxygen <2 mg L-1) in the region. Water column community respiration rates (WR) were measured on 10 cr...

Rheology of K-feldspar aggregates and its implications for dynamics of continental lower crust

NASA Astrophysics Data System (ADS)

Chen, J.; Jin, Z.; Shi, F.; Zhang, J.

2015-12-01

Rheology of feldspar-dominated rocks controls many important processes fundamental to understanding the dynamics of continental lower crust. K-feldspar mineral is an important constituent mineral for continental lower crust and the Precambrian terranes. However, the rheological properties of K-feldspar have not been well quantified. We have performed triaxial compression experiments on natural K-feldspar (88 ppm wt. H2O) aggregates at 1.5 GPa and 1273 - 1373 K using a modified 5GPa Griggs apparatus. The hot-pressed specimens are wrapped in a thin layer of Nickel foil and sealed in 9mm long Platinum jackets along with overlying alumina pistons. Fitting of our preliminary data indicates that the deformation occurred in the dislocation creep regime with a stress exponent of ~3.3 and an activation energy of ~512 kJ/mol. Comparison of our results to previous studies indicates that K-feldspar is stronger than granulite but weaker than eclogite and dry olivine aggregates. These results suggest that K-feldspar likely serves as a strong phase in continental lower crust and the Precambrian terrane.

Mapping land cover change over continental Africa using Landsat and Google Earth Engine cloud computing.

PubMed

Midekisa, Alemayehu; Holl, Felix; Savory, David J; Andrade-Pacheco, Ricardo; Gething, Peter W; Bennett, Adam; Sturrock, Hugh J W

2017-01-01

Quantifying and monitoring the spatial and temporal dynamics of the global land cover is critical for better understanding many of the Earth's land surface processes. However, the lack of regularly updated, continental-scale, and high spatial resolution (30 m) land cover data limit our ability to better understand the spatial extent and the temporal dynamics of land surface changes. Despite the free availability of high spatial resolution Landsat satellite data, continental-scale land cover mapping using high resolution Landsat satellite data was not feasible until now due to the need for high-performance computing to store, process, and analyze this large volume of high resolution satellite data. In this study, we present an approach to quantify continental land cover and impervious surface changes over a long period of time (15 years) using high resolution Landsat satellite observations and Google Earth Engine cloud computing platform. The approach applied here to overcome the computational challenges of handling big earth observation data by using cloud computing can help scientists and practitioners who lack high-performance computational resources.

Mapping land cover change over continental Africa using Landsat and Google Earth Engine cloud computing

PubMed Central

Holl, Felix; Savory, David J.; Andrade-Pacheco, Ricardo; Gething, Peter W.; Bennett, Adam; Sturrock, Hugh J. W.

2017-01-01

Quantifying and monitoring the spatial and temporal dynamics of the global land cover is critical for better understanding many of the Earth’s land surface processes. However, the lack of regularly updated, continental-scale, and high spatial resolution (30 m) land cover data limit our ability to better understand the spatial extent and the temporal dynamics of land surface changes. Despite the free availability of high spatial resolution Landsat satellite data, continental-scale land cover mapping using high resolution Landsat satellite data was not feasible until now due to the need for high-performance computing to store, process, and analyze this large volume of high resolution satellite data. In this study, we present an approach to quantify continental land cover and impervious surface changes over a long period of time (15 years) using high resolution Landsat satellite observations and Google Earth Engine cloud computing platform. The approach applied here to overcome the computational challenges of handling big earth observation data by using cloud computing can help scientists and practitioners who lack high-performance computational resources. PMID:28953943

30 CFR 256.1 - Purpose.

Code of Federal Regulations, 2011 CFR

2011-07-01

... LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Outer Continental Shelf Oil, Gas, and... administer a leasing program for oil, gas and sulphur. The procedures under which the Secretary will exercise...

78 FR 47748 - Right-of-Way Grant of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-06

...-Way Grant of Submerged Lands on the Outer Continental Shelf to Support Renewable Energy Development... will use Form 0009 to issue a renewable energy right-of- way (ROW) grant on the Outer Continental Shelf....gov/Renewable-Energy Program/ Regulatory-Information/Index.aspx. DATES: The ROW grant form will be...

The Continental Margin of East Asia: a collage of multiple plates formed by convergence and extension from multiple directions

NASA Astrophysics Data System (ADS)

Mao, J.; Wang, T.; Ludington, S.; Qiu, Z.; Li, Z.

2017-12-01

East Asia is one of the most complex regions in the world. Its margin was divided into 4 parts: Northeast Asia, North China, South China and Southeast Asia. During the Phanerozoic, continental plates of East Asia have interacted successively with a) the Paleo Tethyan Ocean, b) the Tethyan and Paleo Pacific Oceans and c) the Pacific and Indian. In the Early Mesozoic, the Indosinian orogeny is characterized by the convergence and extension within multiple continental plates, whereas the Late Mesozoic Yanshanian orogeny is characterized by both convergence and compression due to oceanic subduction and by widespread extension. We propose this combination as "East Asia Continental Margin type." Except in Northeast Asia, where Jurassic and Cretaeous accretionary complexes are common, most magmatic rocks are the result of reworking of ancient margins of small continental plates; and oceanic island arc basalts and continental margin arc andesites are largely absent. Because South China is adjacent to the western margin of the Pacific Plate, some effects of its westward subduction must be unavoidable, but juvenile arc-related crust has not been identified. The East Asian Continental Margin is characterized by magmatic rocks that are the result of post-convergent tectonics, which differs markedly from the active continental margins of both South and North America. In summary, the chief characteristics of the East Asian Continental Margin are: 1) In Mesozoic, the periphery of multiple blocks experienced magmatism caused by lithospheric delamination and thinning in response to extension punctuated by shorter periods of convergence. 2) The main mechanism of magma generation was the partial melting of crustal rocks, due to underplating by upwelling mafic magma associated with the collapse of orogenic belts and both extension and compression between small continental blocks. 3) During orogeny, mostly high Sr/Y arc-related granitoids formed, whereas during post-orogenic times, A-type granitoids formed. 4) These dynamics are the result of subduction and extension of the oceanic plates that bordered East Asia. 5) The complex mosaic of geology and geochemistry is the result of compositional variation in the deep lithosphere, as well as variation in the dynamics of oceanic plate movements.

Large fluctuations of shallow seas in low-lying Southeast Asia driven by mantle flow

NASA Astrophysics Data System (ADS)

Zahirovic, Sabin; Flament, Nicolas; Dietmar Müller, R.; Seton, Maria; Gurnis, Michael

2016-09-01

The Sundaland continental promontory, as the core of Southeast Asia, is one of the lowest lying continental regions, with half of the continental area presently inundated by a shallow sea. The role of mantle convection in driving long-wavelength topography and vertical motion of the lithosphere in this region has often been ignored when interpreting regional stratigraphy, including a widespread Late Cretaceous-Eocene unconformity, despite a consensus that Southeast Asia is presently situated over a large-amplitude dynamic topography low resulting from long-term post-Pangea subduction. We use forward numerical models to link mantle flow with surface tectonics and compare predicted trends of dynamic topography with eustasy and regional paleogeography to determine the influence of mantle convection on regional basin histories. A Late Cretaceous collision of Gondwana-derived terranes with Sundaland choked the active margin, leading to slab breakoff and a ˜10-15 Myr-long subduction hiatus. A subduction hiatus likely resulted in several hundred meters of dynamic uplift and emergence of Sundaland between ˜80 and 60 Ma and may explain the absence of a Late Cretaceous-Eocene sedimentary record. Renewed subduction from ˜60 Ma reinitiated dynamic subsidence of Sundaland, leading to submergence from ˜40 Ma despite falling long-term global sea levels. Our results highlight a complete "down-up-down" dynamic topography cycle experienced by Sundaland, with transient dynamic topography manifesting as a major regional unconformity in sedimentary basins.

Carbon and oxygen dynamics on the Louisiana continental shelf: role of water column primary production and respiration

EPA Science Inventory

We conducted a multi-year study of the Louisiana continental shelf (LCS) to better understand the linkages between water column net metabolism and the formation of hypoxia (dissolved oxygen <2 ml O2 L-1) in the region. Rates of water column community respiration (R) and primary p...

Continental Scientific Drilling Program.

DTIC Science & Technology

1979-01-01

Institute of Technology ALBERT W. BALLY, Shell Oil Company, Houston HUBERT L. BARNES, Pennsylvania State University ARTHUR L. BOETTCHER, University of...San Marcos arch near Victoria, Texas. Information from a hole would answer fundamental questions about ancient continental margins and would complement...did the uplift begin in this area? Is the crust continental or oceanic? Area 3 (Figure A-7), positioned upon the San Marcos arch to avoid the thick

Transition to Glass: Pilot Training for High-Technology Transport Aircraft

DTIC Science & Technology

1999-05-01

training programs D. Training considerations STUDY METHODOLOGY A. Basic questions and premises B. Questionnaires: attitude scales, demography , and flying...product of many tributaries, including the original Continental ("Old Continental" as it is called by pilots), Pioneer , Texas International, Frontier...to the southwest and later Hawaii. In 1953 Continental acquired Pioneer Airlines, with 16 destinations in the west. Six moved the company from El

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.

Morphology and sediment dynamics of the northern Catalan continental shelf, northwestern Mediterranean Sea

NASA Astrophysics Data System (ADS)

Durán, Ruth; Canals, Miquel; Sanz, José Luis; Lastras, Galderic; Amblas, David; Micallef, Aaron

2014-01-01

The northern Catalan continental shelf, in the northwestern Mediterranean Sea, extends along 200 km from the Cap de Creus submarine canyon to the Llobregat Delta, in the vicinity of the city of Barcelona. In this paper we present the results of a systematic investigation of this area by means of very high-resolution multibeam bathymetry to fully assess its morphological variability. The causative factors and processes determining such variability are subsequently interpreted. The shelf is divided in three segments by two prominent submarine canyons: the northernmost Roses Shelf is separated from the intermediate La Planassa Shelf by the La Fonera Canyon, while the boundary between the La Planassa Shelf and the southernmost Barcelona Shelf is marked by the Blanes Canyon. These two canyons are deeply incised in the continental margin, with their heads located at only 0.8 and 5 km from the shore, respectively. The seafloor character reflects the influence of external controlling factors on the geomorphology and sediment dynamics of the northern continental shelf of Catalonia. These factors are the geological setting, the volume and nature of sediment input, and the type and characteristics of processes leading to sediment redistribution, such as dense shelf water cascading (DSWC) and eastern storms. The interaction of all these factors determines sediment dynamics and allows subdividing the northern Catalan continental shelf into three segments: the erosional-depositional Roses Shelf to the north, the non-depositional La Planassa Shelf in the middle, and the depositional Barcelona Shelf to the south. Erosional features off the Cap de Creus Peninsula and an along-shelf subdued channel in the outer shelf illustrate prevailing sediment dynamics in the Roses segment, which is dominated by erosional processes, local sediment accumulations and the southward bypass of sediment. The rocky character of the seafloor immediately north of the Blanes Canyon head demonstrates that neither significant sediment inputs from the Tordera River nor from the northern sources reach the southern part of the La Planassa Shelf. Palaeo-shorelines depict a number of paleodeltas with steep delta fronts on the drowned Barcelona Shelf.

Effect of rheological approximations on slab detachment in 3D numerical simulations of continental collision

NASA Astrophysics Data System (ADS)

Pusok, Adina E.; Kaus, Boris; Popov, Anton

2017-04-01

It is commonly accepted that slab detachment results from the development of extensional stresses within the subducting slab. Subduction slowdown due to arrival of buoyant continental material at the trench is considered to cause such stress build up in the slab. Following slab detachment, slab pull partially or completely loses its strength and hot asthenosphere may flow through the slab window, which can have major consequences for continental collision. The dynamics of slab detachment has been extensively studied in 2D (i.e. analytical and numerical), but 3D models of slab detachment during continental collision remain largely unexplored. Some of the previous 3D models have investigated the role of an asymmetric margin on the propagation of slab detachment (van Hunen and Allen, 2011), the impact of slab detachment on the curvature of orogenic belts (Capitanio and Replumaz, 2013), the role of the collision rate on slab detachment depth (Li et al., 2013) or the effect of along-trench variations on slab detachment (Duretz et al., 2014). However, rheology of mantle and lithosphere is known to have a major influence on the dynamics of subduction. Here, we explore a range of different rheological approximations to understand their sensitivity on the possible scenarios. We employ the code LaMEM (Kaus et al., 2016) to perform 3D simulations of subduction/continental collision in an integrated lithospheric and upper-mantle scale model. The models exhibit a wide range of behaviours depending on the rheological law employed: from linear, to temperature-dependent visco-elasto-plastic rheology that takes into account both diffusion and dislocation creep. For example, we find that slab dynamics varies drastically between end member models: in viscous approximations, slab detachment is slow, dominated by viscous thinning, while for a non-linear visco-elasto-plastic rheology, slab detachment is relatively fast, dominated by plastic breaking and inducing strong mantle flow in the slab window. Moreover, in models of viscous approximation, slab break-off starts in the slab interior due tot the nature of slab necking, while in models of non-linear visco-elasto-plastic rheology, slab tear will first occur at the edges of the continental collision.

Insight into collision zone dynamics from topography: numerical modelling results and observations

NASA Astrophysics Data System (ADS)

Bottrill, A. D.; van Hunen, J.; Allen, M. B.

2012-11-01

Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.

30 CFR 256.1 - Purpose.

Code of Federal Regulations, 2010 CFR

2010-07-01

... MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF SULPHUR OR OIL AND GAS IN THE OUTER CONTINENTAL SHELF Outer Continental Shelf Oil, Gas, and Sulphur Management, General § 256.1... Secretary of the Interior (Secretary) will exercise the authority to administer a leasing program for oil...

A numerical investigation of continental collision styles

NASA Astrophysics Data System (ADS)

Ghazian, Reza Khabbaz; Buiter, Susanne J. H.

2013-06-01

Continental collision after closure of an ocean can lead to different deformation styles: subduction of continental crust and lithosphere, lithospheric thickening, folding of the unsubducted continents, Rayleigh-Taylor (RT) instabilities and/or slab break-off. We use 2-D thermomechanical models of oceanic subduction followed by continental collision to investigate the sensitivity of these collision styles to driving velocity, crustal and lithospheric temperature, continental rheology and the initial density difference between the oceanic lithosphere and the asthenosphere. We find that these parameters influence the collision system, but that driving velocity, rheology and lithospheric (rather than Moho and mantle) temperature can be classified as important controls, whereas reasonable variations in the initial density contrast between oceanic lithosphere and asthenosphere are not necessarily important. Stable continental subduction occurs over a relatively large range of values of driving velocity and lithospheric temperature. Fast and cold systems are more likely to show folding, whereas slow and warm systems can experience RT-type dripping. Our results show that a continent with a strong upper crust can experience subduction of the entire crust and is more likely to fold. Accretion of the upper crust at the trench is feasible when the upper crust has a moderate to weak strength, whereas the entire crust can be scraped-off in the case of a weak lower crust. We also illustrate that weakening of the lithospheric mantle promotes RT-type of dripping in a collision system. We use a dynamic collision model, in which collision is driven by slab pull only, to illustrate that adjacent plates can play an important role in continental collision systems. In dynamic collision models, exhumation of subducted continental material and sediments is triggered by slab retreat and opening of a subduction channel, which allows upward flow of buoyant materials. Exhumation continues after slab break-off by reverse motion of the subducting plate (`eduction') caused by the reduced slab pull. We illustrate how a simple force balance of slab pull, slab push, slab bending, viscous resistance and buoyancy can explain the different collision styles caused by variations in velocity, temperature, rheology, density differences and the interaction with adjacent plates.

Paleomagnetism of sedimentary cores from the Ross Sea outer shelf and continental slope (PNRA-ROSSLOPE II Project)

NASA Astrophysics Data System (ADS)

Macrì, Patrizia; Sagnotti, Leonardo; Caricchi, Chiara; Colizza, Ester

2016-04-01

We carried out a paleomagnetic and rock magnetic study of 4 gravity cores sampled in the Ross Sea continental slope of the area to the east of Pennell-Iselin banks. The cores (RS14-C1, C2, C3 and ANTA99-C20) consist of hemipelagic fine-grained (silty-clays) sediments with an IRD component. Rock magnetic and paleomagnetic measurements were carried out at 1-cm spacing on u-channel samples. The data indicate that the cored sediments carry a well-defined characteristic remanent magnetization (ChRM) and have a valuable potential to reconstruct dynamics and amplitude of the geomagnetic field variation at high southern latitudes (ca. 75°S) during the Holocene and the late Pleistocene. The paleomagnetic and rock magnetic data are integrated in a multidisciplinary context which includes previous geological, geophysical, oceanographic and morpho-bathimetric data obtained in the same area in the frame of the PNRA/ROSSLOPE (Past and present sedimentary dynamic in the ROSS Sea: a multidisciplinary approach to study the continental slope) Project. The main aim of the project is to investigate the relation between present and past water mass circulation and to provide a basis for paleoceanographic reconstructions and for the development of a depositional model of the modern processes active along the continental slope.

75 FR 17155 - Preparation of an Environmental Assessment (EA) for Proposed Outer Continental Shelf (OCS) Oil...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-05

... all requirements of NEPA, the Coastal Zone Management Act, Outer Continental Shelf Lands Act, and... consistent with each affected state's federally approved Coastal Zone Management program. Finally, the MMS...-circulation modeling, ecological effects of oil and gas activities, and hurricane impacts on coastal...

76 FR 7518 - Outer Continental Shelf Air Regulations Consistency Update for Alaska

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-10

... ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 55 [EPA-R10-OAR-2011-0045; FRL-9265-3] Outer Continental Shelf Air Regulations Consistency Update for Alaska AGENCY: Environmental Protection Agency (``EPA... Greaves, Federal and Delegated Air Programs Unit, U.S. Environmental Protection Agency, Region 10, 1200...

Atmospheric water vapor transport: Estimation of continental precipitation recycling and parameterization of a simple climate model. M.S. Thesis

NASA Technical Reports Server (NTRS)

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

1991-01-01

The advective transport of atmospheric water vapor and its role in global hydrology and the water balance of continental regions are discussed and explored. The data set consists of ten years of global wind and humidity observations interpolated onto a regular grid by objective analysis. Atmospheric water vapor fluxes across the boundaries of selected continental regions are displayed graphically. The water vapor flux data are used to investigate the sources of continental precipitation. The total amount of water that precipitates on large continental regions is supplied by two mechanisms: (1) advection from surrounding areas external to the region; and (2) evaporation and transpiration from the land surface 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. 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. In a separate, but related, study estimates of ocean to land water vapor transport are used to parameterize an existing simple climate model, containing both land and ocean surfaces, that is intended to mimic the dynamics of continental climates.

Summaries of FY 92 geosciences research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-12-01

The Department of Energy supports research in the geosciences in order to provide a sound foundation of fundamental knowledge in those areas of the geosciences that are germane to the Department of Energy's many missions. The Division of Engineering and Geosciences, part of the Office of Basic Energy Sciences of the Office of Energy Research, supports the Geosciences Research Program. The participants in this program include Department of Energy laboratories, academic institutions, and other governmental agencies. These activities are formalized by a contract or grant between the Department of Energy and the organization performing the work, providing funds for salaries,more » equipment, research materials, and overhead. The summaries in this document, prepared by the investigators, describe the scope of the individual programs. The Geosciences Research Program includes research in geophysics, geochemistry, resource evaluation, solar-terrestrial interactions and their subdivisions including Earth dynamics, properties of Earth materials, rock mechanics, underground imaging, rock-fluid interactions, continental scientific drilling, geochemical transport, solar/atmospheric physics, and modeling, with emphasis on the interdisciplinary areas. All such research is related either directly or indirectly to the Department of Energy's long-range technological needs.« less

Anomalous Subsidence at Rifted Continental Margins: Distinguishing Mantle Dynamic Topography from Anomalous Oceanic Crustal Thickness

NASA Astrophysics Data System (ADS)

Cowie, L.; Kusznir, N. J.

2012-12-01

It has been proposed that some continental rifted margins have anomalous subsidence histories and that at breakup they were elevated at shallower bathymetries than the isostatic response of classical rift models (McKenzie 1978) would predict. The existence of anomalous syn or post breakup subsidence of this form would have important implications for our understanding of the geodynamics of continental breakup and rifted continental margin formation, margin subsidence history and the evolution of syn and post breakup depositional systems. We have investigated three rifted continental margins; the Gulf of Aden, Galicia Bank and the Gulf of Lions, to determine whether the oceanic crust in the ocean-continent transition of these margins has present day anomalous subsidence and if so, whether it is caused by mantle dynamic topography or anomalous oceanic crustal thickness. Residual depth anomalies (RDA) corrected for sediment loading, using flexural backstripping and decompaction, have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous oceanic bathymetry and subsidence at these margins. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions from Crosby & McKenzie (2009). Non-zero sediment corrected RDAs may result from anomalous oceanic crustal thickness with respect to the global average, or from mantle dynamic uplift. Positive RDAs may result from thicker than average oceanic crust or mantle dynamic uplift; negative RDAs may result from thinner than average oceanic crust or mantle dynamic subsidence. Gravity inversion incorporating a lithosphere thermal gravity anomaly correction and sediment thickness from 2D seismic data has been used to determine Moho depth and oceanic crustal basement thickness. The reference Moho depths used in the gravity inversion have been calibrated against seismic refraction Moho depths. The gravity inversion crustal basement thicknesses together with Airy isostasy have been used to predict a "synthetic" gravity derived RDA. Sediment corrected RDA for oceanic crust in the Gulf of Aden are positive (+750m) indicating anomalous uplift with respect to normal subsidence. Gravity inversion predicts normal thickness oceanic crust and a zero "synthetic" gravity derived RDA in the oceanic domain. The difference between the positive sediment corrected RDA and the zero "synthetic" gravity derived RDA, implies that the anomalous subsidence reported in the Gulf of Aden is the result of mantle dynamic uplift. For the oceanic crust outboard of Galicia Bank both the sediment corrected RDA and the "synthetic" gravity derived RDA are negative (-800m) and of similar magnitude, indicating anomalous subsidence, which is the result of anomalously thin oceanic crust, not mantle dynamic topography. We conclude that there is negligible mantle dynamic topography influencing the Galicia Bank region. In the Gulf of Lions, gravity inversion predicts thinner than average oceanic crust. Both sediment corrected RDA (-1km) and "synthetic" gravity derived RDA (-500m) are negative. The more negative sediment corrected RDA compared with the "synthetic" gravity derived RDA implies that the anomalous subsidence in the Gulf of Lions is the result of mantle dynamic subsidence as well as thinner than average oceanic crust.

Insights from 3D numerical simulations on the dynamics of the India-Asia collision zone

NASA Astrophysics Data System (ADS)

Pusok, A. E.; Kaus, B.; Popov, A.

2013-12-01

The dynamics of the India-Asia collision zone remains one of the most remarkable topics of the current research interest: the transition from subduction to collision and uplift, followed by the rise of the abnormally thick Tibetan plateau, and the deformation at its Eastern and Western syntaxes, are processes still not fully understood. Models that have addressed this topic include wholescale underthrusting of Indian lithospheric mantle under Tibet, distributed homogeneous shortening or the thin-sheet model, slip-line field model for lateral extrusion or lower crustal flow models for the exhumation of the Himalayan units and lateral spreading of the Tibetan plateau. Of these, the thin-sheet model has successfully illustrated some of the basic physics of continental collision and has the advantage of a 3D model being reduced to 2D, but one of its major shortcomings is that it cannot simultaneously represent channel flow and gravitational collapse of the mantle lithosphere, since these mechanisms require the lithosphere to interact with the underlying mantle, or to have a vertically non-homogeneous rheology. As a consequence, 3D models are emerging as powerful tools to understand the dynamics of coupled systems. However, because of yet recent developments and various complexities, the current 3D models simulating the dynamics of continent collision zones have relied on certain explicit assumptions, such as replacing part of the asthenosphere with various types of boundary conditions that mimic the effect of mantle flow, in order to focus on the lithospheric/crustal deformation. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We present qualitative results on lithospheric and upper-mantle scale simulations in which the Indian lithosphere is subducted and/or indented into Asia. We investigate the way deep processes affect continental tectonics at convergent margins, addressing the role the continent subduction and indentation plays on the development of continental tectonics during convergence and we discuss the implications these offer for the Asian tectonics. Acknowledgements: Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on MOGON (ZDV Mainz computing center) and JUQUEEN (Jülich high-performance computing center).

Insight into collision zone dynamics from topography: numerical modelling results and observations

NASA Astrophysics Data System (ADS)

Bottrill, A. D.; van Hunen, J.; Allen, M. B.

2012-07-01

Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away from the base of the overriding plate. Also during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate causes the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. This uplift and subsidence pattern correlates well with our modelled topography changes.

Satellite observation of particulate organic carbon dynamics on the Louisiana continental shelf

EPA Science Inventory

Particulate organic carbon (POC) plays an important role in coastal carbon cycling and the formation of hypoxia. Yet, coastal POC dynamics are often poorly understood due to a lack of long-term POC observations and the complexity of coastal hydrodynamic and biogeochemical process...

Scientific Drilling of Impact Craters - Well Logging and Core Analyses Using Magnetic Methods (Invited)

NASA Astrophysics Data System (ADS)

Fucugauchi, J. U.; Perez-Cruz, L. L.; Velasco-Villarreal, M.

2013-12-01

Drilling projects of impact structures provide data on the structure and stratigraphy of target, impact and post-impact lithologies, providing insight on the impact dynamics and cratering. Studies have successfully included magnetic well logging and analyses in core and cuttings, directed to characterize the subsurface stratigraphy and structure at depth. There are 170-180 impact craters documented in the terrestrial record, which is a small proportion compared to expectations derived from what is observed on the Moon, Mars and other bodies of the solar system. Knowledge of the internal 3-D deep structure of craters, critical for understanding impacts and crater formation, can best be studied by geophysics and drilling. On Earth, few craters have yet been investigated by drilling. Craters have been drilled as part of industry surveys and/or academic projects, including notably Chicxulub, Sudbury, Ries, Vredefort, Manson and many other craters. As part of the Continental ICDP program, drilling projects have been conducted on the Chicxulub, Bosumtwi, Chesapeake, Ries and El gygytgyn craters. Inclusion of continuous core recovery expanded the range of paleomagnetic and rock magnetic applications, with direct core laboratory measurements, which are part of the tools available in the ocean and continental drilling programs. Drilling studies are here briefly reviewed, with emphasis on the Chicxulub crater formed by an asteroid impact 66 Ma ago at the Cretaceous/Paleogene boundary. Chicxulub crater has no surface expression, covered by a kilometer of Cenozoic sediments, thus making drilling an essential tool. As part of our studies we have drilled eleven wells with continuous core recovery. Magnetic susceptibility logging, magnetostratigraphic, rock magnetic and fabric studies have been carried out and results used for lateral correlation, dating, formation evaluation, azimuthal core orientation and physical property contrasts. Contributions of magnetic studies on impact age, cratering, target-impactite stratigraphy, ejecta, impact dynamics, hydrothermal alterations and post-impact processes are presented. The challenges and perspectives of drilling studies of impact craters are discussed.

Paleomagnetic and Magnetostratigraphic Studies in Drilling Projects of Impact Craters - Recent Studies, Challenges and Perspectives

NASA Astrophysics Data System (ADS)

Fucugauchi, J. U.; Velasco-Villarreal, M.; Perez-Cruz, L. L.

2013-05-01

Paleomagnetic studies have long been successfully carried out in drilling projects, to characterize the borehole columns and to investigate the subsurface structure and stratigraphy. Magnetic susceptibility logging and magnetostratigraphic studies provide data for lateral correlation, formation evaluation, azimuthal core orientation, physical properties, etc., and are part of the tools available in the ocean and continental drilling programs. The inclusion of continuous core recovery in scientific drilling projects have greatly expanded the range of potential applications of paleomagnetic and rock magnetic studies, by allowing laboratory measurements on core samples. For this presentation, we concentrate on drilling studies of impact structures and their usefulness for documenting the structure, stratigraphy and physical properties at depth. There are about 170-180 impact craters documented in the terrestrial record, which is a small number compared to what is observed in the Moon, Mars, Venus and other bodies of the solar system. Of the terrestrial impact craters, only a few have been studied by drilling. Some craters have been drilled as part of industry exploration surveys and/or academic projects, including notably the Sudbury, Ries, Vredefort, Manson and many other craters. As part of the Continental ICDP program, drilling projects have been conducted on the Chicxulub, Bosumtwi, Chesapeake and El gygytgyn craters. Drilling of terrestrial craters has proved important in documenting the shallow stratigraphy and structure, providing insight on the cratering and impact dynamics. Questions include several that can only be addressed by retrieving core samples and laboratory analyses. Paleomagnetic, rock magnetic and fabric studies have been conducted in the various craters, which are here summarized with emphasis on the Chicxulub crater and Yucatan carbonate platform. Chicxulub is buried under a kilometer of younger sediments, making drilling an essential tool. Oil exploration included several boreholes, and additionally we have drilled 11 boreholes with continuous core recovery. Contributions and limitations of paleomagnetism for investigating the impact age, crater stratigraphy, cratering, ejecta emplacement, impact dynamics, hydrothermal system and post-impact processes are discussed.

Sedimentary Framework of an Inner Continental Shelf Sand-Ridge System, West-Central Florida

NASA Astrophysics Data System (ADS)

Locker, S. D.; Hine, A. C.; Wright, A. K.; Duncan, D. S.

2002-12-01

The west-central Florida inner continental shelf is a dynamic environment subject to current flows on a variety of temporal and spatial scales. A site survey program, undertaken in support of the Office of Naval Research's Mine Burial prediction program, is focused on the sedimentary framework and sediment accumulation patterns in 10-18 meters water depth. Our specific goals are to image the shallow subsurface and to monitor changes in bedform distribution patterns that coincide with physical processes studies ongoing in the area. Methods of study include side-scan sonar imaging, boomer and chirp subbottom profiling, and sedimentary facies analysis using surface sediment sampling and vibracoring. A well-defined sand-ridge system was imaged, trending oblique to the west-Florida coastline. The side-scan clearly shows that there is extensive three-dimensional structure within these large-scale NW-SE trending sedimentary bedforms. The sand ridges commonly are approximately 1 km wide and 4-8 km in length. The characteristics of these ridges are distinctly different than the sand ridges in < 8 m water that we have previously studied. Ridges in the offshore area tend to be thicker, have a flatter morphology, and exhibit fewer smaller-scale sand waves. Sand-ridge thickness ranges 2-3 meters, and typically consists of fining upward medium to fine quartz sand facies with occasional centimeter-scale coarser-grained carbonate-rich intervals. Time series investigations tracking the shift in position of the sand ridge margins have found undetectable net annual movement. However significant resuspension and bedform development accompanies high-energy events such as winter cold front passage. Thus the large-scale bedforms (sand ridges) are in a state of dynamic equilibrium with the average annual hydrodynamic regime. Repeated field surveys will focus on monitoring small-scale sedimentological and stratal framework changes that will be integrated with the quantitative process studies.

Ice Streams as the Critical Link Between the Interior Ice Reservoir of the Antarctic Ice Sheet and the Global Climate System - a WISSARD Perspective (Invited)

NASA Astrophysics Data System (ADS)

Tulaczyk, S. M.; Beem, L.; Walter, J. I.; Hossainzadeh, S.; Mankoff, K. D.

2010-12-01

Fast flowing ice streams represent crucial features of the Antarctic ice sheet because they provide discharge ‘valves’ for the interior ice reservoir and because their grounding lines are exposed to ocean thermal forcing. Even with no/little topographic control ice flow near the perimeter of a polar ice sheet self-organizes into discrete, fast-flowing ice streams. Within these features basal melting (i.e. lubrication for ice sliding) is sustained through elevated basal shear heating in a region of thin ice that would otherwise be characterized by basal freezing and slow ice motion. Because faster basal ice motion is typically associated with faster subglacial erosion, ice streams tend to localize themselves over time by carving troughs into underlying rocks and sediments. Debris generated by this erosional activity is carried to the continental shelf and/or continental slope where it may be deposited at very high rates, rivaling these associated with deposition by some of the largest rivers on Earth. In terms of their hydrologic and geological functions, Antarctic ice streams play pretty much the same role as rivers do on non-glaciated continents. However, understanding of their dynamics is still quite rudimentary, largely because of the relative inaccessibility of the key basal and marine boundaries of ice streams where pertinent measurements need to be made. The present elevated interest in predicting future contribution of Antarctica to global sea level changes is driving ambitious research programs aimed at scientific exploration of these poorly investigated environments that will play a key role in defining the response of the ice sheet to near future climate changes. We will review one of these programs, the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) with particular focus on its planned contributions to understanding of ice stream dynamics.

Cleavage of a Gulf of Mexico Loop Current eddy by a deep water cyclone

NASA Astrophysics Data System (ADS)

Biggs, D. C.; Fargion, G. S.; Hamilton, P.; Leben, R. R.

1996-09-01

Eddy Triton, an anticyclonic eddy shed by the Loop Current in late June 1991, drifted SW across the central Gulf of Mexico in the first 6 months of 1992, along the ``southern'' of the three characteristic drift paths described by Vukovich and Crissman [1986] from their analyses of 13 years of advanced very high resolution radiometer sea surface temperature data. An expendable bathythermograph (XBT) and conductivity-temperature-depth (CTD) transect of opportunity through Triton at eddy age 7 months in January 1992 found that eddy interior stood 23 dyn. cm higher than periphery; this gradient drove an anticyclonic swirl transport of 9-10 Sv relative to 800 dbar. At eddy age 9-10 months and while this eddy was in deep water near 94°W, it interacted with a mesoscale cyclonic circulation and was cleaved into two parts. The major (greater dynamic centimeters) piece drifted NW to end up in the ``eddy graveyard'' in the NW corner of the gulf, while the minor piece drifted SW and reached the continental margin of the western gulf off Tuxpan. This southern piece of Eddy Triton then turned north to follow the 2000-m isobath to about 24°N and later coalesced with what remained of the major fragment. Because Eddy Triton's cleavage took place just before the start of marine mammals (GulfCet) and Louisiana-Texas physical oceanography (LATEX) field programs, the closely spaced CTD, XBT, and air dropped XBT (AXBT) data that were gathered on the continental margin north of 26°N in support of these programs allow a detailed look at the northern margin of the larger fragment of this eddy. Supporting data from the space-borne altimeters on ERS 1 and TOPEX/POSEIDON allow us to track both pieces of Eddy Triton in the western Gulf and follow their spin down in dynamic height, coalescence, and ultimate entrainment in January 1993 into another anticyclonic eddy (Eddy U).

Middle Miocene environmental and climatic evolution at the Wilkes Land margin, East Antarctica

NASA Astrophysics Data System (ADS)

Sangiorgi, Francesca; Bijl, Peter; Passchier, Sandra; Salzmann, Ulrich; Schouten, Stefan; Pross, Jörg; Escutia, Carlota; Brinkhuis, Henk

2015-04-01

Integrated Ocean Drilling Program (IODP) Expedition 318 successfully drilled a Middle Miocene (~ 17 - 12.5 Ma) record from the Wilkes Land Margin at Site U1356A (63°18.6138'S, 135°59.9376'E), located at the transition between the continental rise and the abyssal plain at 4003 mbsl. We present a multiproxy palynological (dinoflagellate cyst, pollen and spores), sedimentological and organic geochemical (TEX86, MBT/CBT) study, which unravels the environmental and climate variability across the Miocene Climatic Optimum (MCO, ~17-15 Ma) and the Mid Miocene Climate Transition (MMCT). Several independent lines of evidence suggest a relatively warm climate during the MCO. Dinocyst and pollen assemblage diversity at the MCO is unprecedented for a Neogene Antarctic record and indicates a temperate, sea ice-free marine environment, with woody sub-antarctic vegetation with elements of forest/shrub tundra and peat lands along the coast. These results are further confirmed by relatively warm TEX86-derived Sea Surface Temperatures and mild MBT-derived continental temperatures, and by the absence of glacially derived deposits and very few ice-rafted clasts. A generally colder but highly dynamic environment is suggested for the interval 15-12.5 Ma.

Evolution of continental-scale drainage in response to mantle dynamics and surface processes: An example from the Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Sembroni, Andrea; Molin, Paola; Pazzaglia, Frank J.; Faccenna, Claudio; Abebe, Bekele

2016-05-01

Ethiopia offers an excellent opportunity to study the effects and linkage between mantle dynamics and surface processes on landscape evolution. The Ethiopian Highlands (NW Ethiopia), characterized by a huge basaltic plateau, is part of the African Superswell, a wide region of dynamically-supported anomalously high topography related to the rising of the Afar plume. The initiation and steadiness of dynamic support beneath Ethiopia has been explored in several studies. However the presence, role, and timing of dynamic support beneath Ethiopia and its relationship with continental flood basalts volcanism and surface processes are poorly defined. Here, we present a geomorphological analysis of the Ethiopian Highlands supplying new constraints on the evolution of river network. We investigated the general topographic features (filtered topography, swath profiles, local relief) and the river network (river longitudinal profiles) of the study area. We also apply a knickpoint celerity model in order to provide a chronological framework to the evolution of the river network. The results trace the long-term progressive capture of the Ethiopian Highlands drainage system and confirm the long-term dynamic support of the area, documenting its impact on the contrasting development of the Blue Nile and Tekeze basins.

Evolution of continental-scale drainage in response to mantle dynamics and surface processes: an example from the Ethiopian Highlands.

NASA Astrophysics Data System (ADS)

Sembroni, Andrea; Molin, Paola; Pazzaglia, Frank J.; Faccenna, Claudio; Abebe, Bekele

2016-04-01

Ethiopia offers an excellent opportunity to study the effects and linkage between mantle dynamics and surface processes on landscape evolution. The Ethiopian Highlands (NW Ethiopia), characterized by a huge basaltic plateau, is part of the African Superswell, a wide region of dynamically-supported anomalously high topography related to the rising of the Afar plume. The initiation and steadiness of dynamic support beneath Ethiopia has been explored in several studies. However the presence, role, and timing of dynamic support beneath Ethiopia and its relationship with continental flood basalts volcanism and surface processes are poorly defined. Here, we present a geomorphological analysis of the Ethiopian Highlands supplying new constrains on the evolution of river network. We investigated the general topographic features (filtered topography, swath profiles, local relief) and the river network (river longitudinal profiles) of the study area. We also apply a knickpoint celerity model in order to provide a chronological framework to the evolution of the river network. The results trace the long-term progressive capture of the Ethiopian Highlands drainage system and confirm the long-term dynamic support of the area, documenting its impact on the contrasting development of the Blue Nile and Tekeze basins.

Analysis of combined data sets yields trend estimates for vulnerable spruce-fir birds in northern United States

Treesearch

Joel Ralston; David I. King; William V. DeLuca; Gerald J. Niemi; Michale J. Glennon; Judith C. Scarl; J. Daniel Lambert

2015-01-01

Continental-scale monitoring programs with standardized survey protocols play an important role in conservation science by identifying species in decline and prioritizing conservation action. However, rare, inaccessible, or spatially fragmented communities may be underrepresented in continental-scale surveys. Data on these communities often come from decentralized,...

Estimation of future PM2.5- and ozone-related mortality over the continental United States in a changing climate: An application of high-resolution dynamical downscaling technique.

PubMed

Sun, Jian; Fu, Joshua S; Huang, Kan; Gao, Yang

2015-05-01

This paper evaluates the PM2.5- and ozone-related mortality at present (2000s) and in the future (2050s) over the continental United States by using the Environmental Benefits Mapping and Analysis Program (BenMAP-CE). Atmospheric chemical fields are simulated by WRF/CMAQ (horizontal resolution: 12×12 km), applying the dynamical downscaling technique from global climate-chemistry model under the Representative Concentration Pathways scenario (RCP 8.5). Future air quality results predict that the annual mean PM2.5 concentration in continental U.S. decreases nationwide, especially in the Eastern U.S. and west coast. However, the ozone concentration is projected to decrease in the Eastern U.S. but increase in the Western U.S. Future mortality is evaluated under two scenarios (1) holding future population and baseline incidence rate at the present level and (2) using the projected baseline incidence rate and population in 2050. For PM2.5, the entire continental U.S. presents a decreasing trend of PM2.5-related mortality by the 2050s in Scenario (1), primarily resulting from the emissions reduction. While in Scenario (2), almost half of the continental states show a rising tendency of PM2.5-related mortality, due to the dominant influence of population growth. In particular, the highest PM2.5-related deaths and the biggest discrepancy between present and future PM2.5-related deaths both occur in California in 2050s. For the ozone-related premature mortality, the simulation shows nation-wide rising tendency in 2050s under both scenarios, mainly due to the increase of ozone concentration and population in the future. Furthermore, the uncertainty analysis shows that the confidence interval of all causes mortality is much larger than that for specific causes, probably due to the accumulated uncertainty of generating datasets and sample size. The confidence interval of ozone-related all cause premature mortality is narrower than the PM2.5-related all cause mortality, due to its smaller standard deviation of the concentration-mortality response factor. The health impact of PM2.5 is more linearly proportional to the emission reductions than ozone. The reduction of anthropogenic PM2.5 precursor emissions is likely to lead to the decrease of PM2.5 concentrations and PM2.5 related mortality. However, the future ozone concentrations could increase due to increase of the greenhouse gas emissions of methane. Thus, to reduce the impact of ozone related mortality, anthropogenic emissions including criteria pollutant and greenhouse gas (i.e. methane) need to be controlled.

Finite strain calculations of continental deformation. I - Method and general results for convergent zones. II - Comparison with the India-Asia collision zone

NASA Technical Reports Server (NTRS)

Houseman, G.; England, P.

1986-01-01

The present investigation has the objective to perform numerical experiments on a rheologically simple continuum model for the continental lithosphere. It is attempted to obtain a better understanding of the dynamics of continental deformation. Calculations are presented of crustal thickness distributions, stress, strain, strain rate fields, latitudinal displacements, and finite rotations, taking into account as basis a model for continental collision which treats the litoshphere as a thin viscous layer subject to indenting boundary conditions. The results of this paper support the conclusions of England and McKenzie (1982) regarding the role of gravity in governing the deformation of a thin viscous layer subject to indenting boundary conditions. The results of the experiments are compared with observations of topography, stress and strain rate fields, and palaeomagnetic latitudinal displacements in Asia.

Dynamics of Volunteering in Older Europeans

ERIC Educational Resources Information Center

Hank, Karsten; Erlinghagen, Marcel

2010-01-01

Purpose: To investigate the dynamics of volunteering in the population aged 50 years or older across 11 Continental European countries. Design and Methods: Using longitudinal data from the first 2 waves of the Survey of Health, Ageing and Retirement in Europe, we run multivariate regressions on a set of binary-dependent variables indicating…

Deglaciation and glacial erosion: a joint control on magma productivity by continental unloading

NASA Astrophysics Data System (ADS)

Sternai, Pietro; Caricchi, Luca; Castelltort, Sebastien

2016-04-01

Glacial-interglacial cycles affect the processes through which water and rocks are redistributed across the Earth's surface, thereby linking solid-Earth and climate dynamics. Regional and global scale studies suggest that continental lithospheric unloading due to ice melting during the transition to interglacials leads to increased continental magmatic, volcanic and degassing activity. Such a climatic forcing on the melting of the Earth's interior, however, has always been evaluated without considering the additional continental unloading associated with erosion. Current datasets relating to the evolution of erosion rates are typically limited by temporal resolutions that are too low or span too short time intervals to allow for direct comparisons between the contributions from ice melting and erosion to continental unloading at the timescale of the late Pleistocene glacial cycles. Yet, they provide a fundamental observational basis on which to calibrate numerical predictions. Here, we present and discuss numerical results involving synthetic but realistic topographies, ice caps and glacial erosion rates suggesting that erosion may be as important as deglaciation in affecting continental unloading, sub-continental decompression melting and magma productivity. Thus, the timing and magnitude of deglaciation and erosion must be characterized if the forcing of climate change on the continental magmatic/volcanic activity is to be extracted from the remnants of eroded volcanic centers. Our study represents an additional step towards a more general understanding of the links between a changing climate, glacial processes and the melting of the solid Earth.

Geochemistry of the Amazon Estuary

USGS Publications Warehouse

Smoak, Joseph M.; Krest, James M.; Swarzenski, Peter W

2006-01-01

The Amazon River supplies more freshwater to the ocean than any other river in the world. This enormous volume of freshwater forces the estuarine mixing out of the river channel and onto the continental shelf. On the continental shelf, the estuarine mixing occurs in a very dynamic environment unlike that of a typical estuary. The tides, the wind, and the boundary current that sweeps the continental shelf have a pronounced influence on the chemical and biological processes occurring within the estuary. The dynamic environment, along with the enormous supply of water, solutes and particles makes the Amazon estuary unique. This chapter describes the unique features of the Amazon estuary and how these features influence the processes occurring within the estuary. Examined are the supply and cycling of major and minor elements, and the use of naturally occurring radionuclides to trace processes including water movement, scavenging, sediment-water interaction, and sediment accumulation rates. The biogeochemical cycling of carbon, nitrogen, and phosphorus, and the significances of the Amazon estuary in the global mass balance of these elements are examined.

Earth resources programs at the Langley Research Center. Part 2: Coastal zone oceanography program

NASA Technical Reports Server (NTRS)

Bressette, W. E.

1972-01-01

The approaches used to develop the coastal zone oceanic research program are outlined, and activities in the areas of satellite application, estuaries, continental shelf and environmental modeling are briefly described.

Flocculation, heavy metals (Cu, Pb, Zn) and the sand-mud transition on the Adriatic continental shelf, Italy

USGS Publications Warehouse

George, D.A.; Hill, P.S.; Milligan, T.G.

2007-01-01

Across a limited depth range (5-10 m) on many continental shelves, the dominant sediment size changes from sand to mud. This important boundary, called the sand-mud transition (SMT), separates distinct benthic habitats, causes a significant change in acoustic backscatter, represents a key facies change, and delimits more surface-reactive mud from less surface-reactive sand. With the goal of improving dynamical understanding of the SMT, surficial sediments were characterized across two SMTs on the Adriatic continental shelf of Italy. Geometric mean diameter, specific surface area (SSA), mud fraction (<63 ??m) and heavy metal concentrations were all measured. The SMT related to the Tronto River is identified between 15 and 20 m water depth while the SMT associated with the Pescara River varies between 15 and 25 m water depth. The sediment properties correlate with a new, process-based sedimentological parameter that quantifies the fraction of the sediment in the seabed that was delivered as flocs. These correlations suggest that floc dynamics exert strong influence over sediment textural properties and metal concentrations. Relative constancy in the depth of the SMT along this portion of the margin and its lack of evolution over a period during which sediment input to the margin has dramatically decreased suggest that on the Adriatic continental shelf energy is the dominant control on the depth of the SMT. ?? 2006 Elsevier Ltd. All rights reserved.

Spatial variations in dietary organic matter sources modulate the size and condition of fish juveniles in temperate lagoon nursery sites

NASA Astrophysics Data System (ADS)

Escalas, Arthur; Ferraton, Franck; Paillon, Christelle; Vidy, Guy; Carcaillet, Frédérique; Salen-Picard, Chantal; Le Loc'h, François; Richard, Pierre; Darnaude, Audrey Michèle

2015-01-01

Effective conservation of marine fish stocks involves understanding the impact, on population dynamics, of intra-specific variation in nursery habitats use at the juvenile stage. In some regions, an important part of the catching effort is concentrated on a small number of marine species that colonize coastal lagoons during their first year of life. To determine the intra-specific variation in lagoon use by these fish and their potential demographic consequences, we studied diet spatiotemporal variations in the group 0 juveniles of a highly exploited sparid, the gilthead seabream (Sparus aurata L.), during their ∼6 months stay in a NW Mediterranean lagoon (N = 331, SL = 25-198 mm) and traced the origin of the organic matter in their food webs, at two lagoon sites with contrasted continental inputs. This showed that the origin (marine, lagoonal or continental) of the organic matter (OM) available in the water column and the sediment can vary substantially within the same lagoon, in line with local variations in the intensity of marine and continental inputs. The high trophic plasticity of S. aurata allows its juveniles to adapt to resulting differences in prey abundances at each site during their lagoon residency, thereby sustaining high growth irrespective of the area inhabited within the lagoon. However, continental POM incorporation by the juveniles through their diet (of 21-37% on average depending on the site) is proportional to its availability in the environment and could be responsible for the greater fish sizes (of 28 mm SL on average) and body weights (of 40.8 g on average) observed at the site under continental influence in the autumn, when the juveniles are ready to leave the lagoon. This suggests that continental inputs in particulate OM, when present, could significantly enhance fish growth within coastal lagoons, with important consequences on the local population dynamics of the fish species that use them as nurseries. As our results indicate that continental OM can represent up to 62% of the flesh of the juveniles originating from these ecosystems, particular care should be taken to preserve or improve the chemical quality of riverine inputs to coastal lagoons.

Enhancing continental-scale understanding of agriculture: Integrating the National Ecological Observatory Network (NEON) with existing research networks to address global change.

NASA Astrophysics Data System (ADS)

Kelly, G.

2015-12-01

Over the past decade, there has been a resurgence of interest in the sustainability of the world's food system and its contributions to feeding the world's population as well as to ensuring environmental sustainability of the planet. The elements of this grand challenge are by now well known. Analysis of agricultural sustainability is made more challenging by the fact that the local responses to these global drivers of change are extremely variable in space and time due to the biophysical and geopolitical heterogeneity across the United States, and the world. Utilizing research networks allows the scientific community to leverage existing knowledge, models and data to develop a framework for understanding the interplay between global change drivers, regional, and continental sustainability of US agriculture. For example, well-established instrumented and calibrated research networks will allow for the examination of the potential tradeoffs between: 1) crop production, 2) land use and carbon emissions and sequestration, 3) groundwater depletion, and 4) nitrogen dynamics. NEON represents a major investment in scientific infrastructure in support of ecological research at a continental scale and is intended to address multiple ecological grand challenges. NEON will collect data from automated sensors and sample organisms and ecological variables in 20 eco-climatic domains. We will provide examples of how NEON's full potential can be realized when these data are combined with long term experimental results and other sensor networks [e.g., Ameriflux, Fluxnet, the Long-term Ecological Research Program (LTER), the Long-term Agroecosystem Research Network (LTAR)], Critical Zone Observatory (CZO).

Climate-driven Shifting in Distribution Patterns of Calanus sinicus Brodsky in the Continental Shelf Waters of the Northwest Pacific Ocean

NASA Astrophysics Data System (ADS)

Yang, Q.; Liu, H.; Yan, Q. L.; Fan, J. F.

2016-02-01

Large-scale variations in zooplankton dynamics, including the poleward movements and earlier timing of life cycle events, have been widely observed over recent decades. The biogeographical shifts are often related to the increasing sea surface temperature or the long-term climatological change, such as the North Atlantic Oscillation (NAO), the El Niño Southern Oscillation (NESO) and the Pacific Decadal Oscillation (PDO). The Copepod Calanus sinicus Brodsky plays an important trophic role in the continental shelf waters of the Northwest Pacific Ocean as a grazer of phytoplankton and main food source for many ecologically and commercially important fish, such as sardine and anchovy. Because of its importance in marine ecosystem dynamics, C. sinicus was selected as one of the "keystone species" in the China-GLOBEC program. In this study, we examined the shifts in spatial patterns of the species within its distribution domain - the Yellow Sea and the northern East China Sea in the 1950s, 1980s and 2010s. We used contour mapping and a mathematical model to locate the geographical distribution center of the species. We found a significant relationship (r=0.594, P<0.05) between the monthly PDO index and the latitudes of the distribution center of C. sinicus, and a lag of two months for copepods to respond the PDO index. Our findings imply a northward shifting in the distribution center, and the northern Yellow Sea is becoming a new distribution center as another possible over-summering site of C. sinicus.

Global geodynamic models constrained by tectonic reconstructions including plate deformation

NASA Astrophysics Data System (ADS)

Gurnis, M.; Flament, N.; Spasojevic, S.; Williams, S.; Seton, M.; Müller, R. D.

2011-12-01

In order to investigate the effect of mantle flow on the Earth's surface, imposing the kinematics predicted by plate reconstructions in global convection models has become common practice. Such models are valuable to investigate the effect of the mantle flow beneath the lithosphere on surface topography. Changes in surface topography due to lithospheric deformation are so far not part of top-down tectonic models in which plates are treated as rigid in traditional tectonic reconstructions. We introduce a new generation of geodynamic models that are based on tectonic reconstructions with deforming plates at both passive and convergent margins. These models allow us to investigate the relationships between lithospheric deformation and mantle flow, and their combined effects on surface topography. In traditional tectonic reconstructions, continents are represented as rigid blocks that either overlap or are separated by gaps in full-fit reconstructions. Reconstructions that include a global network of topological plate polygons avoid continental overlaps and gaps, but velocities are still derived on the basis of the Euler poles for rigid blocks. To resolve these issues, we developed a series of deforming plate models using the open source plate modeling software GPlates. For a given area, our methodology requires the relative motions between major rigid continental blocks, and a definition of the regions in which continental lithosphere deformed between these blocks. We use geophysical and geological data to define the limit between rigid and deforming areas, and the deformation history of non-rigid blocks. The velocity field predicted by these reconstructions is then used as a time-dependent surface boundary condition in global 3-D geodynamic models. To incorporate the continental lithosphere in our global models, we embed compositionally distinct crust and continental lithosphere within the thermal lithosphere. We define three isostatic columns of different thickness and buoyancy based on the tectonothermal age of the continents: Archean, Proterozoic and Phanerozoic. In the fourth isostatic column, the oceans, the thickness of the thermal lithosphere is assimilated using the half-space cooling model. We also use this capacity to define the thickness of the thermal lithosphere for different continental types, with the exception of the deforming areas that are fully dynamic. Finally, we introduce a new slab assimilation method in which the thermal structure of the slab, derived analytically, is progressively assimilated in the upper mantle into the dynamic models. This method not only improves the continuity of slabs in our models, but it also allows us to model flat slab segments that are particularly relevant for dynamic topography. This new generation of models allows us to analyse the contributions of continental deformation and of mantle flow to surface topography. We compare our results to geological and geophysical data, including stratigraphy, paleo-altimetry, paleo-environment and mantle tomography. This allows us to place constraints on key model parameters and to refine our knowledge of plate-mantle interactions during continental deformation.

From Dynamic Global Vegetation Modelling to Real-World regional and local Application

NASA Astrophysics Data System (ADS)

Steinkamp, J.; Forrest, M.; Kamm, K.; Leiblein-Wild, M.; Pachzelt, A.; Werner, C.; Hickler, T.

2015-12-01

Dynamic (global) vegetation models (DGVM) can be applied to any spatial resolution on the local, national, continental and global scale given suitable climatic and geographic input forcing data. LPJ-GUESS, the main DGVM applied in our research group, uses the plant functional type (PFT) concept in the global setup with typically about 10-20 tree PFTs (subdivided into tropical, temperate and boreal) and two herbaceous PFTs by default. When modelling smaller spatial extents, such as continental (e.g. Europe/North America) national domains, or individual sites (e.g. Frankfurt, Germany), i.e. the scale of decision making, it becomes necessary to refine the PFT representation, the model initialization and validation and, in some case, to include additional processes. I will present examples of LPJ-GUESS applications at the continental to local scale performed by our working group including i.) a European simulation representing the main tree species and Mediterranean shrubs, ii.) a climate impact study for Turkey, iii.) coupled dynamic large grazer-vegetation modelling across Africa and, iv.) modelling an allergenic and in Europe invasive shrub (Ambrosia artemisiifolia), iv.) simulating water usage by an oak-pine forest stand near Frankfurt, and v.) stand specific differences in modelling at the FACE sites. Finally, I will present some thoughts on how to advance the models in terms of more detailed and realistic PFT or species parameterizations accounting for adaptive functional trait responses also within species.

Two Decades of WRF/CMAQ simulations over the continental United States: New approaches for performing dynamic model evaluation and determining confidence limits for ozone exceedances

EPA Science Inventory

Confidence in the application of models for forecasting and regulatory assessments is furthered by conducting four types of model evaluation: operational, dynamic, diagnostic, and probabilistic. Operational model evaluation alone does not reveal the confidence limits that can be ...

Circumpolar variation in periodicity and synchrony among gypsy moth populations

Treesearch

Derek M. Johnson; Andrew M. Liebhold; Ottar N. Bjornstad; Michael L. Mcmanus; Michael L. Mcmanus

2005-01-01

Previous studies or insect dynamics have detected spatial synchrony in intraspecific population dynamics up to, but not exceeding, 1000 km. Oddly, interspecific synchrony has recently been reported at distances well over 1000 km (at continental and circumpolar scales). While the authors implicated climatic effects as the cause for the apparent largescale interspecific...

Nutrient Distributions, Transports, and Budgets on the Inner Margin of a River-Dominated Continental Shelf

DTIC Science & Technology

2013-10-02

and budgets on the inner margin of a river-dominated continental shelf, J. Geophys. Res. Oceans , 118, 4822–4838, doi:10.1002/jgrc.20362. 1...13/10.1002/jgrc.20362 4822 JOURNAL OF GEOPHYSICAL RESEARCH: OCEANS , VOL. 118, 4822–4838, doi:10.1002/jgrc.20362, 2013 Report Documentation Page Form...shelf, and current velocities obtained from a three-dimensional (3-D) hydro- dynamic model (the Navy Coastal Ocean Model). The budget terms were used to

Current kinematics and dynamics of Africa and the East African Rift System

NASA Astrophysics Data System (ADS)

Stamps, D. S.; Flesch, L. M.; Calais, E.; Ghosh, A.

2014-06-01

Although the East African Rift System (EARS) is an archetype continental rift, the forces driving its evolution remain debated. Some contend buoyancy forces arising from gravitational potential energy (GPE) gradients within the lithosphere drive rifting. Others argue for a major role of the diverging mantle flow associated with the African Superplume. Here we quantify the forces driving present-day continental rifting in East Africa by (1) solving the depth averaged 3-D force balance equations for 3-D deviatoric stress associated with GPE, (2) inverting for a stress field boundary condition that we interpret as originating from large-scale mantle tractions, (3) calculating dynamic velocities due to lithospheric buoyancy forces, lateral viscosity variations, and velocity boundary conditions, and (4) calculating dynamic velocities that result from the stress response of horizontal mantle tractions acting on a viscous lithosphere in Africa and surroundings. We find deviatoric stress associated with lithospheric GPE gradients are ˜8-20 MPa in EARS, and the minimum deviatoric stress resulting from basal shear is ˜1.6 MPa along the EARS. Our dynamic velocity calculations confirm that a force contribution from GPE gradients alone is sufficient to drive Nubia-Somalia divergence and that additional forcing from horizontal mantle tractions overestimates surface kinematics. Stresses from GPE gradients appear sufficient to sustain present-day rifting in East Africa; however, they are lower than the vertically integrated strength of the lithosphere along most of the EARS. This indicates additional processes are required to initiate rupture of continental lithosphere, but once it is initiated, lithospheric buoyancy forces are enough to maintain rifting.

2014 & 2015 Loop Current Observations from a Gulf of Mexico Public-Private Ocean Observing Collaboration

NASA Astrophysics Data System (ADS)

Leung, P.; Perry, R.; Sharma, N.; Zwissler, C.; McCall, W.; Bouchard, R. H.; Martin, K. M.

2016-02-01

In 2008, Shell Exploration & Production Company and NOAA formed a collaboration to explore joint opportunities for monitoring the Gulf of Mexico outer continental shelf (OCS). Since then, industry, academic, private, and government partners have been working to build an adaptive ocean observing program that leverages and integrates the complementary strengths of each partner. The program includes vessel and rig-mounted ADCPs, buoys, remote sensing, and profiling gliders with advanced numerical modeling. In this presentation, we focus on 2014 and 2015 program observations of the Gulf physical environment. The 2014 season was characterized by strong Loop Current (LC) circulation with persistent currents (3.5+ knots) extending as far north as 29oN. A number of eddies impacted the Mississippi Canyon region from May to November with one (Eddy Lazarus) undergoing several separation and reattachment cycles. During Lazarus reattachment, the fresh inflow resulted in rapid northward surge of strong currents at and onto the Louisiana continental shelf resulting in advection of Mississippi River waters into the outer OCS. Advection led to higher than average offshore surface and near-surface production atypical for the OCS. The combination of fast, persistent LC speeds and dynamic eddies impacted operations throughout the eastern, central, and western Gulf regions. The 2015 season is active. The size and intensity of eddies (4 at time of publication) are impacting industry and glider operations and forecasting of the LC. Eddies Nautilus and Olympus (250nm wide, 4 knot currents) remain in the central Gulf impacting activities from the Mississippi Canyon to Walker Ridge. Integrating real-time observations with numerical modeling provides the collaboration an opportunity to observe unique features in real-time. Furthermore, data sharing from this program is providing valuable, near real-time data for the community to better understand annual variability of the LC and eddies.

Monitoring challenges and innovative ideas

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Neill, R.V.; Hunsaker, C.T.; Levine, D.A.

1990-01-01

Monitoring programs are difficult to design even when they focus on specific problems. Ecosystems are complex, and it is often impossible to predetermine what aspects of system structure or dynamics will respond to a specific insult. It is equally difficult to interpret whether a response is a stabilizing compensatory mechanism or a real loss of capacity to maintain the ecosystem. The problems are compounded in a broad monitoring program designed to assess ecosystem health'' at regional and continental scales. It is challenging in the extreme to monitor ecosystem response, at any scale, to past insults as well as an unknownmore » future array of impacts. The present paper will examine some of the fundamental issues and challenges raised by large-scale monitoring efforts. The challenges will serve as a framework and as an excuse to discuss several important topics in more detail. Following the discussion of challenges, we suggest some basic innovations that could be important across a range of monitoring programs. The innovations include integrative measures, innovative methodology, and creative interpretation. 59 refs., 1 tab.« less

Transforming SWAT for continental-scale high-resolution modeling of floodplain dynamics: opportunities and challenges

NASA Astrophysics Data System (ADS)

Rajib, A.; Merwade, V.; Liu, Z.; Lane, C.; Golden, H. E.; Tavakoly, A. A.; Follum, M. L.

2017-12-01

There have been many initiatives to develop frameworks for continental-scale modeling and mapping floodplain dynamics. The choice of a model for such needs should be governed by its suitability to be executed in high performance cyber platforms, ability to integrate supporting hydraulic/hydrodynamic tools, and ability to assimilate earth observations. Furthermore, disseminating large volume of outputs for public use and interoperability with similar frameworks should be considered. Considering these factors, we have conducted a series of modeling experiments and developed a suite of cyber-enabled platforms that have transformed Soil and Water Assessment Tool (SWAT) into an appropriate model for use in a continental-scale, high resolution, near real-time flood information framework. Our first experiment uses a medium size watershed in Indiana, USA and attempts burning-in a high resolution, National Hydrography Dataset Plus(NHDPlus) into the SWAT model. This is crucial with a view to make the outputs comparable with other global/national initiatives. The second experiment is built upon the first attempt to add a modified landscape representation in the model which differentiates between the upland and floodplain processes. Our third experiment involves two separate efforts: coupling SWAT with a hydrodynamic model LISFLOOD-FP and a new generation, low complexity hydraulic model AutoRoute. We have executed the prototype "loosely-coupled" models for the Upper Mississippi-Ohio River Basin in the USA, encompassing 1 million square km drainage area and nearly 0.2 million NHDPlus river reaches. The preliminary results suggest reasonable accuracy for both streamflow and flood inundation. In this presentation, we will also showcase three cyber-enabled platforms, including SWATShare to run and calibrate large scale SWAT models online using high performance computational resources, HydroGlobe to automatically extract and assimilate multiple remotely sensed earth observations in model sub-basins, and SWATFlow to visualize/download streamflow and flood inundation maps through an interactive interface. With all these transformational changes to enhance and support SWAT, it is expected that the model can be a sustainable alternative in the Global Flood Partnership program.

Intraplate mafic magmatism: New insights from Africa and N. America

NASA Astrophysics Data System (ADS)

Ebinger, C. J.; van der Lee, S.; Tepp, G.; Pierre, S.

2017-12-01

Plate tectonic concepts consider that continental interiors are stable, with magmatism and strain localized to plate boundaries. We re-evaluate the role of pre-existing and evolving lithospheric heterogeneities in light of perspectives afforded by surface to mantle results from active and ancient rift zones in Africa and N. America. Our process-oriented approach addresses the localization of strain and magmatism and stability of continental plate interiors. In both Africa and N. America, geophysical imaging and xenolith studies reveal that thick, buoyant, and chemically distinct Archaean cratons with deep roots may deflect mantle flow, and localize magmatism and strain over many tectonic cycles. Studies of the Colorado Plateau and East African rift reveal widespread mantle metasomatism, and high levels of magma degassing along faults and at active volcanoes. The volcanoes and magmatic systems show a strong dependence on pre-existing heterogeneities in plate structure. Syntheses of the EarthScope program ishow that lateral density contrasts and migration of volatiles that accumulated during subduction can refertilize mantle lithosphere, and enable volatile-rich magmatism beneath relatively thick continental lithosphere. For example, the passive margin of eastern N. America shows uplift and magmatism long after the onset of seafloor spreading, demonstrating the dynamic nature of coupling between the lithosphere, asthenosphere, and deeper mantle. As demonstrated by the East African Rift, the Mid-Continent Rift, and other active and ancient rift zones, the interiors of continents, including thick, cold Archaean cratons are not immune to mafic magmatism and tectonism. Recent studies in N. America and Africa reveal ca. 1000 km-wide zones of dynamic uplift, low upper mantle velocities, and broadly distributed strain. The distribution of magmatism and volatile release, in combination with geophysical signals, indicates a potentially convective origin for widespread intraplate earthquakes and magmatism, across areas broader than the surface expression of rifting. Integrated geophysical, geological and geochemical studies reveal large volumes and rates of magmatism at rift zones, provoking re-evaluation of crustal accretion and carbon and water cycles, as well as earthquake and volcanic hazards.

Downslope flow across the Ross Sea shelf break (Antarctica)

NASA Astrophysics Data System (ADS)

Bergamasco, A.; Budillon, G.; Carniel, S.; Defendi, V.; Meloni, R.; Paschini, E.; Sclavo, M.; Spezie, G.

2003-12-01

The analysis of some high-resolution hydrological data sets acquired during the 1997, 1998, 2001 and 2003 austral summers across the Ross Sea continental shelf break are here presented. The main focus of these cruises carried out in the framework of the Italian National Antarctic Program was the investigation of the downslope flow of the dense waters originated inside the Ross Sea. Such dense waters, flow near the bottom and, reaching the continental shelf break, ventilate the deep ocean. Two Antarctic continental shelf mechanisms can originate dense and deep waters. The former mechanism involves the formation, along the Victoria Land coasts, of a dense and saline water mass, the High Salinity Shelf Water (HSSW). The HSSW formation is linked to the rejection of salt into the water column as sea ice freezes, especially during winter, in the polynya areas, where the ice is continuously pushed offshore by the strong katabatic winds. The latter one is responsible of the formation of a supercold water mass, the Ice Shelf Water (ISW). The salt supplied by the HSSW recirculated below the Ross Ice Shelf, the latent heat of melting and the heat sink provided by the Ross Ice Shelf give rise to plumes of ISW, characterized by temperatures below the sea-surface freezing point. The dense shelf waters migrate to the continental shelf-break, spill over the shelf edge and descend the continental slope as a shelf-break gravity current, subject to friction and possibly enhanced by topographic channelling. Friction, in particular, breaks the constraint of potential vorticity conservation, counteracting the geostrophic tendency for along slope flow. The density-driven downslope motion or cascading entrains ambient water, namely the lower layer of the CDW, reaches a depth where density is the same and spreads off-slope. In fact, the cascading event is inhibited by friction without entrainment. The downslope processes are important for the ocean and climate system because they play a crucial role in the formation of oceanic deep water responsible for ocean/continental shelf exchange of organic carbon, suspended material and dissolved gases around Antarctica. In this context, this work presents the analysis of the 1997, 2001 and 2003 high-resolution surveys carried out in the western Ross Sea near Cape Adare, where the HSSW flows down the continental slope. The second study area was investigated during the 1998 survey of the Italian National Programme for Antarctic Research of the CLIMA Project, in order to follow the ISW overflow path at the shelf break in the central Ross Sea. A 3D primitive equation model was also implemented as a first step in the construction of a high-resolution process study model to explore the dynamical constraints involved in the downslope motion.

The STRATAFORM Project: U.S. Geological Survey geotechnical studies

USGS Publications Warehouse

Minasian, Diane L.; Lee, Homa J.; Locat, Jaques; Orzech, Kevin M.; Martz, Gregory R.; Israel, Kenneth

2001-01-01

This report presents physical property logs of core samples from an offshore area near Eureka, CA. The cores were obtained as part of the STRATAFORM Program (Nittrouer and Kravitz, 1995, 1996), a study investigating how present sedimentation and sediment transport processes influence long-term stratigraphic sequences preserved in the geologic record. The core samples were collected during four separate research cruises to the northern California study area, and data shown in the logs of the cores were collected using a multi-sensor whole core logger. The physical properties collected are useful in identifying stratigraphic units, ground-truthing acoustic imagery and sub-bottom profiles, and in understanding mass movement processes. STRATA FORmation on Margins was initiated in 1994 by the Office of Naval Research, Marine Geology and Geophysics Department as a coordinated multi-investigator study of continental-margin sediment transport processes and stratigraphy (Nittrouer and Kravitz, 1996). The program is investigating the stratigraphic signature of the shelf and slope parts of the continental margins, and is designed to provide a better understanding of the sedimentary record and a better prediction of strata. Specifically, the goals of the STRATAFORM Program are to (Nittrouer and Kravitz, 1995): - determine the geological relevance of short-term physical processes that erode, transport, and deposit particles and those processes that subsequently rework the seabed over time scales - improve capabilities for identifying the processes that form the strata observed within the upper ~100 m of the seabed commonly representing 104-106 years of sedimentation. - synthesize this knowledge and bridge the gap between time scales of sedimentary processes and those of sequence stratigraphy. The STRATAFORM Program is divided into studies of the continental shelf and the continental slope; the geotechnical group within the U.S. Geological Survey provides support to both parts of the project.

Dynamic topography in subduction zones: insights from laboratory models

NASA Astrophysics Data System (ADS)

Bajolet, Flora; Faccenna, Claudio; Funiciello, Francesca

2014-05-01

The topography in subduction zones can exhibit very complex patterns due to the variety of forces operating this setting. If we can deduce the theoretical isostatic value from density structure of the lithosphere, the effect of flexural bending and the dynamic component of topography are difficult to quantify. In this work, we attempt to measure and analyze the topography of the overriding plate during subduction compared to a pure shortening setting. We use analog models where the lithospheres are modeled by thin-sheet layers of silicone putty lying on low-viscosity syrup (asthenosphere). The model is shorten by a piston pushing an oceanic plate while a continental plate including a weak zone to localize the deformation is fixed. In one type of experiments, the oceanic plate bends and subducts underneath the continental one; in a second type the two plates are in contact without any trench, and thus simply shorten. The topography evolution is monitored with a laser-scanner. In the shortening model, the elevation increases progressively, especially in the weak zone, and is consistent with expected isostatic values. In the subduction model, the topography is characterized, from the piston to the back-wall, by a low elevation of the dense oceanic plate, a flexural bulge, the trench forming a deep depression, the highly elevated weak zone, and the continental upper plate of intermediate elevation. The topography of the upper plate is consistent with isostatic values for very early stages, but exhibits lower elevations than expected for later stages. For a same amount of shortening of the continental plate, the thickening is the same and the plate should have the same elevation in both types of models. However, comparing the topography at 20, 29 and 39% of shortening, we found that the weak zone is 0.4 to 0.6 mm lower when there is an active subduction. Theses values correspond to 2.6 to 4 km in nature. Although theses values are high, there are of the same order as dynamic topography and could represent the dynamic effect of the slab sinking into the asthenosphere and lowering the elevation of the upper plate.

The Potential of Carbonyl Sulfide as a Tracer for Gross Primary Productivity at Flux Tower Sites

USDA-ARS?s Scientific Manuscript database

Regional/continental scale studies of atmospheric carbonyl sulfide (OCS) seasonal dynamics and leaf level studies of plant OCS uptake have shown a close relationship to CO2 dynamics and uptake, suggesting potential for OCS as a tracer for gross primary productivity (GPP). Canopy CO2 and OCS differen...

Carbon Dioxide Cycling And The Climate of Ancient Earth

NASA Technical Reports Server (NTRS)

Zahnle, Kevin; Sleep, Norman H.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

Carbon Dioxide Cycling and the Climate of Ancient Earth

NASA Technical Reports Server (NTRS)

Zahnle, Kevin; Sleep, Norman H.

2001-01-01

The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 5. Program logic manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The final report for the project is presented in five volumes. This volume is the Programmer's Manual. It covers: a system overview, attractiveness component of gravity model, trip-distribution component of gravity model, economic-effects model, and the consumer-surplus model. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism.

California State Waters Map Series: offshore of Tomales Point, California

USGS Publications Warehouse

Johnson, Samuel Y.; Dartnell, Peter; Golden, Nadine E.; Hartwell, Stephen R.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Watt, Janet Tilden; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Krigsman, Lisa M.; Sliter, Ray W.; Lowe, Erik N.; Chinn, John L.; Johnson, Samuel Y.; Cochran, Susan A.

2015-01-01

Potential marine benthic habitats in the Offshore of Tomales Point map area range from unconsolidated continental-shelf sediment, to rocky continental-shelf substrate, to unconsolidated estuary sediments. Rocky-shelf outcrops and rubble are considered to be promising potential habitats for rockfish and lingcod, both of which are recreationally and commercially important species. Dynamic bedforms, such as the sand waves at the mouth of Tomales Bay, are considered potential foraging habitat for juvenile lingcod and possibly migratory fishes, as well as for forage fish such as Pacific sand lance.

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

High-resolution coupled ice sheet-ocean modeling using the POPSICLES model

NASA Astrophysics Data System (ADS)

Ng, E. G.; Martin, D. F.; Asay-Davis, X.; Price, S. F.; Collins, W.

2014-12-01

It is expected that a primary driver of future change of the Antarctic ice sheet will be changes in submarine melting driven by incursions of warm ocean water into sub-ice shelf cavities. Correctly modeling this response on a continental scale will require high-resolution modeling of the coupled ice-ocean system. We describe the computational and modeling challenges in our simulations of the full Southern Ocean coupled to a continental-scale Antarctic ice sheet model at unprecedented spatial resolutions (0.1 degree for the ocean model and adaptive mesh refinement down to 500m in the ice sheet model). The POPSICLES model couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), with the BISICLES ice-sheet model (Cornford et al., 2012) using a synchronous offline-coupling scheme. Part of the PISCEES SciDAC project and built on the Chombo framework, BISICLES makes use of adaptive mesh refinement to fully resolve dynamically-important regions like grounding lines and employs a momentum balance similar to the vertically-integrated formulation of Schoof and Hindmarsh (2009). Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests like MISMIP3D (Pattyn et al., 2013) and realistic configurations (Favier et al. 2014). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). For the POPSICLES Antarctic-Southern Ocean simulations, ice sheet and ocean models communicate at one-month coupling intervals.

Subglacial meltwater channels on the Antarctic continental shelf

NASA Astrophysics Data System (ADS)

Kirkham, J. D.; Hogan, K.; Dowdeswell, J. A.; Larter, R. D.; Arnold, N. S.; Nitsche, F. O.; Golledge, N. R.

2017-12-01

Extensive submarine channel networks exist on the Antarctic continental shelf. The genesis of the channels has been attributed to the flow of subglacial meltwater beneath a formerly more expansive Antarctic Ice Sheet (AIS), implying that there was an active subglacial hydrological system beneath the past AIS which influenced its ice flow dynamics and mass-loss behaviour. However, the dimensions of the channels are inconsistent with the minimal quantities of meltwater produced under the AIS at present; consequently, their formative mechanism, and its implications for past ice-sheet dynamics, remain unresolved. Here, analysis of >100,000 km2 of multibeam bathymetric data is used to produce the most comprehensive inventory of Antarctic submarine channelised landforms to date. Over 2700 bedrock channels are mapped across four locations on the inner continental shelves of the Bellingshausen and Amundsen Seas. Morphometric analysis reveals highly similar distributions of channel widths, depths, cross-sectional areas and geometric properties, with subtle differences present between channels located in the Bellingshausen Sea compared to those situated in the Amundsen Sea region. The channels are 75-3400 m wide, 3-280 m deep, 160-290,000 m2 in cross-sectional area, and exhibit V-shaped cross-sectional geometries that are typically eight times as wide as they are deep. The features are comparable, but substantially larger, than the system of channels known as the Labyrinth in the McMurdo Dry Valleys whose genesis has been attributed to catastrophic outburst floods, sourced from subglacial lakes, during the middle Miocene. A similar process origin is proposed for the channels observed on the Antarctic continental shelf, formed through the drainage of relict subglacial lake basins, including some 59 identified using submarine geomorphological evidence and numerical modelling calculations. Water is predicted to accumulate in the subglacial lakes over centuries to millennia and to drain over daily to monthly timescales, potentially influencing past ice-sheet dynamics.

Graph Theory-Based Technique for Isolating Corrupted Boundary Conditions in Continental-Scale River Network Hydrodynamic Simulation

NASA Astrophysics Data System (ADS)

Yu, C. W.; Hodges, B. R.; Liu, F.

2017-12-01

Development of continental-scale river network models creates challenges where the massive amount of boundary condition data encounters the sensitivity of a dynamic nu- merical model. The topographic data sets used to define the river channel characteristics may include either corrupt data or complex configurations that cause instabilities in a numerical solution of the Saint-Venant equations. For local-scale river models (e.g. HEC- RAS), modelers typically rely on past experience to make ad hoc boundary condition adjustments that ensure a stable solution - the proof of the adjustment is merely the sta- bility of the solution. To date, there do not exist any formal methodologies or automated procedures for a priori detecting/fixing boundary conditions that cause instabilities in a dynamic model. Formal methodologies for data screening and adjustment are a critical need for simulations with a large number of river reaches that draw their boundary con- dition data from a wide variety of sources. At the continental scale, we simply cannot assume that we will have access to river-channel cross-section data that has been ade- quately analyzed and processed. Herein, we argue that problematic boundary condition data for unsteady dynamic modeling can be identified through numerical modeling with the steady-state Saint-Venant equations. The fragility of numerical stability increases with the complexity of branching in river network system and instabilities (even in an unsteady solution) are typically triggered by the nonlinear advection term in Saint-Venant equations. It follows that the behavior of the simpler steady-state equations (which retain the nonlin- ear term) can be used to screen the boundary condition data for problematic regions. In this research, we propose a graph-theory based method to isolate the location of corrupted boundary condition data in a continental-scale river network and demonstrate its utility with a network of O(10^4) elements. Acknowledgement: This research is supported by the National Science Foundation un- der grant number CCF-1331610.

National Marine Sanctuaries as Sentinel Sites for a Demonstration Marine Biodiversity Observation Network (MBON)

NASA Astrophysics Data System (ADS)

Muller-Karger, F. E.; Chavez, F.; Gittings, S.; Doney, S. C.; Kavanaugh, M.; Montes, E.; Breitbart, M.; Kirkpatrick, B. A.; Anderson, D. M.; Tartt, M.

2016-02-01

The U.S. Federal government (NOAA and NASA), academic researchers, and private partners are implementing a Demonstration Marine Biodiversity Observation Network (MBON) to monitor changes in marine biodiversity within two US National Marine Sanctuaries (NMS): Florida Keys and Monterey Bay. The overarching goal is to observe and understand life, from microbes to whales, in different coastal and continental shelf habitats. The specific objectives are to 1) Establish a protocol for MBON information to dynamically update Sanctuary status and trends reports; 2) Define an efficient set of observations required for implementing a useful MBON; 3) Develop technology for biodiversity assessments including emerging environmental DNA (eDNA) and remote sensing to coordinate with classical sampling; 4) Integrate and synthesize information in coordination with other MBON projects, the Smithsonian Institution's Tennenbaum Marine Observatories Network (TMON), the Integrated Ocean Observing System (IOOS), the international Group on Earth Observations Biodiversity Observation Network(GEO BON), and the UNESCO-IOC Ocean Biogeographic Information System (OBIS); and 5) Understand the linkages between marine biodiversity, ecosystem processes, and the social-economic context of a region. Pilot projects have been implemented within the Florida Keys and Monterey Bay NMS. Limited observations will be collected at the Flower Garden Banks NMS. These encompass a range of marine environments, including deep sea, continental shelves, and coastal habitats including estuaries, wetlands, and coral reefs. The program will use novel eDNA techniques and ongoing observations to evaluate diversity. Multidisciplinary remote sensing will be used to evaluate dynamic 'seascapes'. The MBON will facilitate and enable regional biodiversity assessments, and contributes to addressing U.N. Sustainable Development Goal 14 to conserve and sustainably use marine resources.

Regional biomass stores and dynamics in forests of coastal Alaska

Treesearch

Mikhaill A. Yatskov; Mark E. Harmon; Olga N. Krankina; Tara M. Barrett; Kevin R. Dobelbower; Andrew N. Gray; Becky Fasth; Lori Trummer; Toni L. Hoyman; Chana M. Dudoit

2015-01-01

Coastal Alaska is a vast forested region (6.2 million ha) with the potential to store large amounts of carbon in live and dead biomass thus influencing continental and global carbon dynamics. The main objectives of this study were to assess regional biomass stores, examine the biomass partitioning between live and dead pools, and evaluate the effect of disturbance on...

A New View of Dynamic River Networks

NASA Astrophysics Data System (ADS)

Perron, J. T.; Willett, S.; McCoy, S. W.

2014-12-01

River networks are the main conduits that transport water, sediment, and nutrients from continental interiors to the oceans. They also shape topography as they erode through bedrock. These hierarchical networks are dynamic: there are numerous examples of apparent changes in the topology of river networks through geologic time. But these examples are geographically scattered, the evidence can be ambiguous, and the mechanisms that drive changes in river networks are poorly understood. This makes it difficult to assess how pervasive river network reorganization is, how it operates, and how the interlocking river basins that compose a given landscape are changing through time. Recent progress has improved the situation. We describe three developments that have dramatically advanced our understanding of dynamic river networks. First, new topographic, geophysical and geochronological measurement techniques are revealing the rate and extent of river network adjustment. Second, laboratory experiments and computational models are clarifying how river networks respond to tectonic and climatic perturbations at scales ranging from local to continental. Third, spatial analysis of genetic data is exposing links between landscape evolution, biological evolution, and the development of biodiversity. We highlight key problems that remain unsolved, and suggest ways to build on recent advances that will bring dynamic river networks into even sharper focus.

Short and long term evolution of deep giant submarine dunes in continental shelf environment: the example of the 'Banc du Four' (Western Brittany, France)

NASA Astrophysics Data System (ADS)

Franzetti, M.; Le Roy, P.; Garlan, T.; Delacourt, C.; Thibaud, R.; Cancouet, R.; Graindorge, D.; Prunier, C.; Sukhovich, A.; Deschamps, A.

2013-12-01

The deep sandwave dynamics is still in debate. Understanding the migration processes and the resulting evolution of their 3D internal architecture are scientifically challenging. To address these questions we realized two swath bathymetry surveys complemented with seismic reflection across the large sandwaves field named 'Banc du Four'. It is located offshore the Western Brittany and is composed of more 500 dunes. Some of the dunes' wavelengths and heights exceed 1000m and 30m respectively placing them among the largest dunes ever described. Equilibrium laws obtained from our morphological analysis are not completely in agreement with those described in previous studies of similar structures in shallow waters. Relatively high migration velocities on deep continental shelves (from 3 to 20m.yr-1) attest of their still present dynamical equilibrium. Internal-external morphological and kinematical analyses show the existence of two different dynamic regimes. Interpretation of the seismic reflection data allowed reconstructing long-term evolution of the sandbank and the establishment of progressive connections between stepped submarine channels and tidal dynamics during the last sea-level rise.

30 CFR 250.1614 - Mud program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Mud program. 250.1614 Section 250.1614 Mineral... OPERATIONS IN THE OUTER CONTINENTAL SHELF Sulphur Operations § 250.1614 Mud program. (a) The quantities, characteristics, use, and testing of drilling mud and the related drilling procedures shall be designed and...

30 CFR 250.913 - When must I resubmit Platform Verification Program plans?

Code of Federal Regulations, 2011 CFR

2011-07-01

... CONTINENTAL SHELF Platforms and Structures Platform Verification Program § 250.913 When must I resubmit Platform Verification Program plans? (a) You must resubmit any design verification, fabrication... 30 Mineral Resources 2 2011-07-01 2011-07-01 false When must I resubmit Platform Verification...

U.S. Eastern Continental Shelf Carbon Cycling (USECoS): Modeling, Data Assimilation, and Analysis

NASA Technical Reports Server (NTRS)

Mannino, Antonio

2008-01-01

Although the oceans play a major role in the uptake of fossil fuel CO2 from the atmosphere, there is much debate about the contribution from continental shelves, since many key shelf fluxes are not yet well quantified: the exchange of carbon across the land-ocean and shelf-slope interfaces, air-sea exchange of CO2, burial, and biological processes including productivity. Our goal is to quantify these carbon fluxes along the eastern U.S. coast using models quantitatively verified by comparison to observations, and to establish a framework for predicting how these fluxes may be modified as a result of climate and land use change. Our research questions build on those addressed with previous NASA funding for the USECoS (U.S. Eastern Continental Shelf Carbon Cycling) project. We have developed a coupled biogeochemical ocean circulation model configured for this study region and have extensively evaluated this model with both in situ and remotely-sensed data. Results indicate that to further reduce uncertainties in the shelf component of the global carbon cycle, future efforts must be directed towards 1) increasing the resolution of the physical model via nesting and 2) making refinements to the biogeochemical model and quantitatively evaluating these via the assimilation of biogeochemical data (in situ and remotely-sensed). These model improvements are essential for better understanding and reducing estimates of uncertainties in current and future carbon transformations and cycling in continental shelf systems. Our approach and science questions are particularly germane to the carbon cycle science goals of the NASA Earth Science Research Program as well as the U.S. Climate Change Research Program and the North American Carbon Program. Our interdisciplinary research team consists of scientists who have expertise in the physics and biogeochemistry of the U.S. eastern continental shelf, remote-sensing data analysis and data assimilative numerical models.

Pandemic influenza computer model (no soundtrack)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Los Alamos National Lab

2009-05-01

Simulation of a pandemic flu outbreak in the continental United States, initially introduced by the arrival of 10 infected individuals in Los Angeles. ----------The spatiotemporal dynamics of the prevalence (number of symptomatic cases at any point in

Impact of atmospheric CO2 levels on continental silicate weathering

NASA Astrophysics Data System (ADS)

Beaulieu, E.; GoddéRis, Y.; Labat, D.; Roelandt, C.; Oliva, P.; Guerrero, B.

2010-07-01

Anthropogenic sources are widely accepted as the dominant cause for the increase in atmospheric CO2 concentrations since the beginning of the industrial revolution. Here we use the B-WITCH model to quantify the impact of increased CO2 concentrations on CO2 consumption by weathering of continental surfaces. B-WITCH couples a dynamic biogeochemistry model (LPJ) and a process-based numerical model of continental weathering (WITCH). It allows simultaneous calculations of the different components of continental weathering fluxes, terrestrial vegetation dynamics, and carbon and water fluxes. The CO2 consumption rates are estimated at four different atmospheric CO2 concentrations, from 280 up to 1120 ppmv, for 22 sites characterized by silicate lithologies (basalt, granite, or sandstones). The sensitivity to atmospheric CO2 variations is explored, while temperature and rainfall are held constant. First, we show that under 355 ppmv of atmospheric CO2, B-WITCH is able to reproduce the global pattern of weathering rates as a function of annual runoff, mean annual temperature, or latitude for silicate lithologies. When atmospheric CO2 increases, evapotranspiration generally decreases due to progressive stomatal closure, and the soil CO2 pressure increases due to enhanced biospheric productivity. As a result, vertical drainage and soil acidity increase, promoting CO2 consumption by mineral weathering. We calculate an increase of about 3% of the CO2 consumption through silicate weathering (mol ha-1 yr-1) for 100 ppmv rise in CO2. Importantly, the sensitivity of the weathering system to the CO2 rise is not uniform and heavily depends on the climatic, lithologic, pedologic, and biospheric settings.

Homogenization of regional river dynamics by dams and global biodiversity implications.

PubMed

Poff, N Leroy; Olden, Julian D; Merritt, David M; Pepin, David M

2007-04-03

Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. Extensive construction of dams by humans has greatly dampened the seasonal and interannual streamflow variability of rivers, thereby altering natural dynamics in ecologically important flows on continental to global scales. The cumulative effects of modification to regional-scale environmental templates caused by dams is largely unexplored but of critical conservation importance. Here, we use 186 long-term streamflow records on intermediate-sized rivers across the continental United States to show that dams have homogenized the flow regimes on third- through seventh-order rivers in 16 historically distinctive hydrologic regions over the course of the 20th century. This regional homogenization occurs chiefly through modification of the magnitude and timing of ecologically critical high and low flows. For 317 undammed reference rivers, no evidence for homogenization was found, despite documented changes in regional precipitation over this period. With an estimated average density of one dam every 48 km of third- through seventh-order river channel in the United States, dams arguably have a continental scale effect of homogenizing regionally distinct environmental templates, thereby creating conditions that favor the spread of cosmopolitan, nonindigenous species at the expense of locally adapted native biota. Quantitative analyses such as ours provide the basis for conservation and management actions aimed at restoring and maintaining native biodiversity and ecosystem function and resilience for regionally distinct ecosystems at continental to global scales.

Continental Basalts and Mantle Xenoliths

NASA Astrophysics Data System (ADS)

Zartman, Robert E.

In this decade of the International Lithosphere Program, much scientific attention is being directed toward the deep continental crust and subadjacent mantle. The petrologic, geochemical, and isotopic signatures of basaltic magmas, which transect much of the lithosphere as they ascend from their site of melting, and of contained cognate and accidental xenoliths, which are found along the path of ascent, give us, perhaps, the best clues to composition and structure in the third dimension. Continental Basalts and Mantle Xenoliths provides an opportunity to sample the British school of thought on subjects such as differences between oceanic and continental basalts, effects of mantle metasomatism, and relationships between events in the subcontinental mantle and those in the overlying crust. This volume is recommended by the publisher as being of interest to senior undergraduates and postgraduate researchers; I would extend that readership to all scientists who seek access to a potpourri of recent findings and current ideas in a rapidly evolving field of research.

Dynamical downscaling inter-comparison for high resolution climate reconstruction

NASA Astrophysics Data System (ADS)

Ferreira, J.; Rocha, A.; Castanheira, J. M.; Carvalho, A. C.

2012-04-01

In the scope of the project: "High-resolution Rainfall EroSivity analysis and fORecasTing - RESORT", an evaluation of various methods of dynamic downscaling is presented. The methods evaluated range from the classic method of nesting a regional model results in a global model, in this case the ECMWF reanalysis, to more recently proposed methods, which consist in using Newtonian relaxation methods in order to nudge the results of the regional model to the reanalysis. The method with better results involves using a system of variational data assimilation to incorporate observational data with results from the regional model. The climatology of a simulation of 5 years using this method is tested against observations on mainland Portugal and the ocean in the area of the Portuguese Continental Shelf, which shows that the method developed is suitable for the reconstruction of high resolution climate over continental Portugal.

Mapping national scale land cover disturbance for the continental United States, 2006 to 2010

NASA Astrophysics Data System (ADS)

Hansen, M. C.; Potapov, P. V.; Egorov, A.; Roy, D. P.; Loveland, T. R.

2011-12-01

Data from the Web-Enabled Landsat Data (WELD) project were used to quantify forest cover loss and bare ground gain dynamics for the continental United States at a 30 meter spatial resolution from 2006 to 2010. Results illustrate the land cover dynamics associated with forestry, urbanization and other medium to long-term cover conversion processes. Ephemeral changes, such as crop rotations and fallows or inundation, were not quantified. Forest disturbance is pervasive at the national-scale, while increasing bare ground is found in growing urban areas as well as in mining regions. The methods applied are an outgrowth of the Vegetation Continuous Field (VCF) method, initially employed with MODIS data and then WELD data to map percent cover variables. As in our previous work with MODIS in mapping forest change, we applied the VCF method to characterize forest cover loss and bare ground gain probability per pixel. Additional themes will be added to provide a more comprehensive picture of national-scale land dynamics based on these initial results using WELD.

Selected data fron continental scientific drilling core holes VC-1 and VC-2a, Valles Caldera, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musgrave, J.A.; Goff, F.; Shevenell, L.

1989-02-01

This report presents geochemical and isotopic data on rocks and water and wellbore geophysical data from the Continental Scientific Drilling Program core holes VC-1 and VC-2a, Valles Caldera, New Mexico. These core holes were drilled as a portion of a broader program that seeks to answer fundamental questions about magma, water/rock interactions, ore deposits, and volcanology. The data in this report will assist the interpretation of the hydrothermal system in the Jemez Mountains and will stimulate further research in magmatic processes, hydrothermal alteration, ore deposits, hydrology, structural geology, and hydrothermal solution chemistry. 37 refs., 36 figs., 28 tabs.

Continental Scientific Drilling Program Data Base

NASA Astrophysics Data System (ADS)

Pawloski, Gayle

The Continental Scientific Drilling Program (CSDP) data base at Lawrence Livermore National Laboratory is a central repository, cataloguing information from United States drill holes. Most holes have been drilled or proposed by various federal agencies. Some holes have been commercially funded. This data base is funded by the Office of Basic Energy Sciences of t he Department of Energy (OBES/DOE) to serve the entire scientific community. Through the unrestricted use of the database, it is possible to reduce drilling costs and maximize the scientific value of current and planned efforts of federal agencies and industry by offering the opportunity for add-on experiments and supplementing knowledge with additional information from existing drill holes.

Using an empirical and rule-based modeling approach to map cause of disturbance in U.S

Treesearch

Todd A. Schroeder; Gretchen G. Moisen; Karen Schleeweis; Chris Toney; Warren B. Cohen; Zhiqiang Yang; Elizabeth A. Freeman

2015-01-01

Recently completing over a decade of research, the NASA/NACP funded North American Forest Dynamics (NAFD) project has led to several important advancements in the way U.S. forest disturbance dynamics are mapped at regional and continental scales. One major contribution has been the development of an empirical and rule-based modeling approach which addresses two of the...

30 CFR 250.1909 - What are management's general responsibilities for the SEMS program?

Code of Federal Regulations, 2012 CFR

2012-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL... intervals specified in the SEMS program and at least annually, review the SEMS program to determine if it... recommendations of that review. (e) Develop and endorse a written description of your safety and environmental...

30 CFR 250.1909 - What are management's general responsibilities for the SEMS program?

Code of Federal Regulations, 2013 CFR

2013-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL... intervals specified in the SEMS program and at least annually, review the SEMS program to determine if it... recommendations of that review. (e) Develop and endorse a written description of your safety and environmental...

30 CFR 250.1909 - What are management's general responsibilities for the SEMS program?

Code of Federal Regulations, 2014 CFR

2014-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL... intervals specified in the SEMS program and at least annually, review the SEMS program to determine if it... recommendations of that review. (e) Develop and endorse a written description of your safety and environmental...

Community Building at Honors Programs in Continental Europe

ERIC Educational Resources Information Center

Brinkel, Nico; van Rees, Floris; Ruis, Margit; Sloots, Florian

2015-01-01

Many universities in the United States and Europe offer honors programs to meet the demands of gifted and intelligent students. One of the standard goals of these programs is to build an intellectual learning community. Establishing a community can be difficult because it requires that students show an active attitude and initiative. Many…

Meso-Cenozoic tectonic evolution of the SE Brazilian continental margin: Petrographic, kinematic and dynamic analysis of the onshore Araruama Lagoon Fault System

NASA Astrophysics Data System (ADS)

Souza, Pricilla Camões Martins de; Schmitt, Renata da Silva; Stanton, Natasha

2017-09-01

The Ararauama Lagoon Fault System composes one of the most prominent set of lineaments of the SE Brazilian continental margin. It is located onshore in a key tectonic domain, where the basement inheritance rule is not followed. This fault system is characterized by ENE-WSW silicified tectonic breccias and cataclasites showing evidences of recurrent tectonic reactivations. Based on field work, microtectonic, kinematic and dynamic analysis, we reconstructed the paleostresses in the region and propose a sequence of three brittle deformational phases accountable for these reactivations: 1) NE-SW dextral transcurrence; 2) NNW-SSE dextral oblique extension that evolved to NNW-SSE "pure" extension; 3) ENE-WSW dextral oblique extension. These phases are reasonably correlated with the tectonic events responsible for the onset and evolution of the SE onshore rift basins, between the Neocretaceous and Holocene. However, based on petrographic studies and supported by regional geological correlations, we assume that the origin of this fault system is older, related to the Early Cretaceous South Atlantic rifting. This study provides significant information about one of the main structural trends of the SE Brazilian continental margin and the tectonic events that controlled its segmentation, since the Gondwana rifting, and compartmentalization of its onshore sedimentary deposits during the Cenozoic.

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

NASA Astrophysics Data System (ADS)

Roy, M.; Rios, D.; Cosburn, K.

2017-12-01

Shear between the moving lithosphere and the underlying asthenospheric mantle can produce dynamic pressure gradients that control patterns of melt migration by percolative flow. Within continental interiors these pressure gradients may be large enough to focus melt migration into zones of low dynamic pressure and thus influence the surface distribution of magmatism. We build upon previous work to show that for a lithospheric keel that protrudes into the "mantle wind," spatially-variable melt migration can lead to spatially-variable thermal weakening of the lithosphere. Our models treat advective heat transfer in porous flow in the limit that heat transfer between the melt and surrounding matrix dominates over conductive heat transfer within either the melt or the solid alone. The models are parameterized by a heat transfer coefficient that we interpret to be related to the efficiency of heat transfer across the fluid-rock interface, related to the geometry and distribution of porosity. Our models quantitatively assess the viability of spatially variable thermal-weakening caused by melt-migration through continental regions that are characterized by variations in lithospheric thickness. We speculate upon the relevance of this process in producing surface patterns of Cenozoic magmatism and heatflow at the Colorado Plateau in the western US.

Constraints on the dynamics of melt migration, flow and emplacement across the continental crust

NASA Astrophysics Data System (ADS)

Cavalcante, Carolina; Viegas, Gustavo

2015-04-01

The presence of partial melting during deformation produces a drastic change in the rheological behavior of the continental crust. The rock strength decreases with melt fractions as low as ~0.7 %. At pressure/temperature conditions typical of the middle crust, melt-bearing systems may play a critical role in the processes of strain localization and in the overall strength of the continental lithosphere. In eastern Brazil, Neoproterozoic tectonics are often associated with wide partial melting and shear zone development, that promote the exhumation of mid- to lower crustal layers where compositionally heterogeneous anatexites with variable melt fractions and leucosome structures are exposed. The leucosomes usually form interconnected networks of magma that reflect the high melt content present during deformation. In this contribution we address two case studies encompassing the dynamics of melt flow at magma chambers, represented by the Carlos Chagas anatexite, and the mechanisms of melt migration and channeling through shear zones, in which the Patos shear zone serves as an analogue. Through detailed petrostructural studies of anatexites exposed at these settings, we aim to demonstrate the way melt deforms and localizes strain, the different patterns of melt flow pathways across the crust, and the implications for the mechanical behaviour of the Earth's lithosphere during orogenic deformation.

Investigating biogeographic boundaries of the Sunda shelf: A phylogenetic analysis of two island populations of Macaca fascicularis.

PubMed

Klegarth, A R; Sanders, S A; Gloss, A D; Lane-deGraaf, K E; Jones-Engel, L; Fuentes, A; Hollocher, H

2017-08-01

Cyclical submergence and re-emergence of the Sunda Shelf throughout the Pleistocene served as a dynamic biogeographic landscape, across which long-tailed macaques (Macaca fascicularis) have migrated and evolved. Here, we tested the integrity of the previously reported continental-insular haplotype divide reported among Y and mitochondrial DNA lineages across multiple studies. The continental-insular haplotype divide was tested by heavily sampling wild macaques from two important biogeographic regions within Sundaland: (1) Singapore, the southernmost tip of continental Asia and (2) Bali, Indonesia, the southeastern edge of the Indonesian archipelago, immediately west of Wallace's line. Y DNA was haplotyped for samples from Bali, deep within the Indonesian archipelago. Mitochondrial D-loop from both islands was analyzed against existing data using Maximum Likelihood and Bayesian approaches. We uncovered both "continental" and "insular" Y DNA haplotypes in Bali. Between Singapore and Bali we found 52 unique mitochondrial haplotypes, none of which had been previously described. Phylogenetic analyses confirmed a major haplogroup division within Singapore and identified five new Singapore subclades and two primary subclades in Bali. While we confirmed the continental-insular divide among mtDNA haplotypes, maintenance of both Y DNA haplotypes on Bali, deep within the Indonesian archipelago calls into question the mechanism by which Y DNA diversity has been maintained. It also suggests the continental-insular designation is less appropriate for Y DNA, leading us to propose geographically neutral Y haplotype designations. © 2017 Wiley Periodicals, Inc.

Ocean Drilling Program Leg 178 (Antarctic Peninsula): Sedimentology of glacially influenced continental margin topsets and foresets

USGS Publications Warehouse

Eyles, N.; Daniels, J.; Osterman, L.E.; Januszczak, N.

2001-01-01

Ocean Drilling Program Leg 178 (February-April 1998) drilled two sites (Sites 1097 and 1103) on the outer Antarctic Peninsula Pacific continental shelf. Recovered strata are no older than late Miocene or early Pliocene (<4.6 Ma). Recovery at shallow depths in loosely consolidated and iceberg-turbated bouldery sediment was poor but improved with increasing depth and consolidation to allow description of lithofacies and biofacies and interpretation of depositional environment. Site 1097 lies on the outer shelf within Marguerite Trough which is a major outlet for ice expanding seaward from the Antarctic Peninsula and reached a maximum depth drilled of 436.6 m below the sea floor (mbsf). Seismic stratigraphic data show flat-lying upper strata resting on strata that dip gently seaward. Uppermost strata, to a depth of 150 mbsf, were poorly recovered, but data suggest they consist of diamictites containing reworked and abraded marine microfauna. This interval is interpreted as having been deposited largely as till produced by subglacial cannibalization of marine sediments (deformation till) recording ice sheet expansion across the shelf. Underlying gently dipping strata show massive, stratified and graded diamictite facies with common bioturbation and slump stuctures that are interbedded with laminated and massive mudstones with dropstones. The succession contains a well-preserved in situ marine microfauna typical of open marine and proglacial marine environments. The lower gently dipping succession at Site 1097 is interpreted as a complex of sediment gravity flows formed of poorly sorted glacial debris. Site 1103 was drilled in that part of the continental margin that shows uppermost flat-lying continental shelf topsets overlying steeper dipping slope foresets seaward of a structural mid-shelf high. Drilling reached a depth of 363 mbsf with good recovery in steeply dipping continental slope foreset strata. Foreset strata are dominated by massive and chaotically stratified diamictites interbedded with massive and graded sandstones and mudstones. The sedimentary record and seismic stratigraphy is consistent with deposition on a continental slope from debris flows and turbidity currents released from a glacial source. Data from Sites 1097 and 1103 suggest the importance of aggradation of the Antarctic Peninsula continental shelf by tilt deposition and progradation of the slope by mass flow. This may provide a model for the interpretation of Palaeozoic and Proterozoic glacial successions that accumulated on glacially influenced continental margins.

Data file: the 1976 Atlantic Margin Coring (AMCOR) Project of the U.S. Geological Survey

USGS Publications Warehouse

Poppe, Lawrence J.; Poppe, Lawrence J.

1981-01-01

In 1976, the U.S. Geological Survey conducted the Atlantic Margin Coring Project (AMCOR) to obtain information on stratigraphy, hydrology and water chemistry, mineral resources other than petroleum hydrocarbons, and geotechnical engineering properties at sites widely distributed along the Continental Shelf and Slope of the Eastern United States (Hathaway and others, 1976, 1979). This program's primary purpose was to investigate a broad variety of sediment properties, many of which had not been previously studied in this region. Previous studies of sediments recovered by core drilling in this region were usually limited to one or two aspects of the sediment properties (Hathaway and others, 1979, table 2). The AMCOR program was limited by two factors: water depth and penetration depth. Because the ship selected for the program, the Glomar Conception, lacked dynamic positioning capability, its anchoring capacity determined the maximum water depth in which drilling could take place. Although it was equipped to anchor in water 450 m deep and did so successfully at one site, we attmepted no drilling in water depths greater than 300 m. Strong Gulf Stream currents at the one attempted deep (443 m) site frustrated attempts to "spud in" to begin the hole.

Continental rifting and the origin of Beta Regio, Venus

NASA Technical Reports Server (NTRS)

Mcgill, G. E.; Steenstrup, S. J.; Barton, C.; Ford, P. G.

1981-01-01

Topographic maps based on Pioneer Venus altimetry suggest that Beta Regio, an elevated feature centered at 27 deg N, 282 deg E, is analogous to domes associated with continental rift systems on earth. This interpretation is consistent with the commonly quoted analogy between the East African rift system and the topography of the region from Beta Regio southward to Phoebe Regio. If Beta Regio is a dome, major structural uplift of the crust of Venus is implied, suggesting a more dynamic upper mantle than would be the case if Beta Regio were simply a large volcanic construct.

The life cycle of continental rifts: Numerical models of plate tectonics and mantle convection.

NASA Astrophysics Data System (ADS)

Ulvrova, Martina; Brune, Sascha; Williams, Simon

2017-04-01

Plate tectonic processes and mantle convection form a self-organized system whose surface expression is characterized by repeated Wilson cycles. Conventional numerical models often capture only specific aspects of plate-mantle interaction, due to imposed lateral boundary conditions or simplified rheologies. Here we study continental rift evolution using a 2D spherical annulus geometry that does not require lateral boundary conditions. Instead, continental extension is driven self-consistently by slab pull, basal drag and trench suction forces. We use the numerical code StagYY to solve equations of conservation of mass, momentum and energy and transport of material properties. This code is capable of computing mantle convection with self-consistently generated Earth-like plate tectonics using a pseudo-plastic rheology. Our models involve an incompressible mantle under the Boussinesq approximation with internal heat sources and basal heating. Due to the 2D setup, our models allow for a comparably high resolution of 10 km at the mantle surface and 15 km at the core mantle boundary. Viscosity variations range over 7 orders of magnitude. We find that the causes for rift initiation are often related to subduction dynamics. Some rifts initiate due to increasing slab pull, others because of developing trench suction force, for instance by closure of an intra-oceanic back-arc basin. In agreement with natural settings, our models reproduce rifts forming in both young and old collision zones. Our experiments show that rift dynamics follow a characteristic evolution, which is independent of the specific setting: (1) continental rifts initiate during tens of million of years at low extension rates (few millimetres per year) (2) the extension velocity increases during less than 10 million years up to several tens of millimetres per year. This speed-up takes place before lithospheric break-up and affects the structural architecture of rifted margins. (3) high divergence rates persist until break-up is achieved and often reduce several tens of millions of years after continental separation. By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration during the transition from phase 1 to phase 2 induces elevated convergence rates at the opposite side of the continents. This leads to enhanced subduction velocities, e.g. between North America and the Farallon plate 200 million years ago, or to the closure of potential back-arc basins such as in the proto-Andean ranges of South America. Post-rift deceleration occurs when the global plate system re-equilibrates after the phase of enhanced stress during continental rupture. This phenomenon of a plate slow-down after mechanical rupture occurred in the real-world aftermath of Australia-Antarctica separation, South Atlantic opening, and North Atlantic break-up.

Modeling a three-dimensional river plume over continental shelf using a 3D unstructured grid model

USGS Publications Warehouse

Cheng, R.T.; Casulli, V.; ,

2004-01-01

River derived fresh water discharging into an adjacent continental shelf forms a trapped river plume that propagates in a narrow region along the coast. These river plumes are real and they have been observed in the field. Many previous investigations have reported some aspects of the river plume properties, which are sensitive to stratification, Coriolis acceleration, winds (upwelling or downwelling), coastal currents, and river discharge. Numerical modeling of the dynamics of river plumes is very challenging, because the complete problem involves a wide range of vertical and horizontal scales. Proper simulations of river plume dynamics cannot be achieved without a realistic representation of the flow and salinity structure near the river mouth that controls the initial formation and propagation of the plume in the coastal ocean. In this study, an unstructured grid model was used for simulations of river plume dynamics allowing fine grid resolution in the river and in regions near the coast with a coarse grid in the far field of the river plume in the coastal ocean, in the vertical, fine fixed levels were used near the free surface, and coarse vertical levels were used over the continental shelf. The simulations have demonstrated the uniquely important role played by Coriolis acceleration. Without Coriolis acceleration, no trapped river plume can be formed no matter how favorable the ambient conditions might be. The simulation results show properties of the river plume and the characteristics of flow and salinity within the estuary; they are completely consistent with the physics of estuaries and coastal oceans.

Change in morphology and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York between 2011 and 2014: Analysis of hurricane impact

USGS Publications Warehouse

Schwab, William C.; Baldwin, Wayne E.; Warner, John C.; List, Jeffrey; Denny, Jane F.; Liste Munoz, Maria; Safak, Ilgar

2017-01-01

Seafloor mapping investigations conducted on the lower shoreface and inner continental shelf offshore of Fire Island, New York in 2011 and 2014, the period encompassing the impacts of Hurricanes Irene and Sandy, provide an unprecedented perspective regarding regional inner continental shelf sediment dynamics during large storm events. Analyses of these studies demonstrate that storm-induced erosion and sediment transport occurred throughout the study area in water depths up to 30 m. Acoustic backscatter patterns were observed to move from ~1 m to 450 m with a mean of 20 m and movement tended to decrease with increasing water depth. These patterns indicate that both of the primary inner continental shelf sedimentary features in the study area, linear sorted bedforms offshore of eastern Fire Island and shoreface-attached sand ridges offshore of central and western Fire island, migrated alongshore to the southwest. The migration of the sorted bedforms represents the modification of an active ravinement surface and is thought to have liberated a significant volume of sediment. Comparison of isopach maps of sediment thickness show that the volume of modern sediment composing the lower shoreface and shoreface-attached sand ridges decreased by ~2.8 × 106 m3 across the ~73 km2 of common seafloor mapped in both surveys. However, a similar analysis for the relatively calmer 15-yr period prior to 2011 revealed significant accretion. This allows speculation that the shoreface-attached sand ridges are maintained over decadal timescales via sediment supplied through erosion of Pleistocene outwash and lower Holocene transgressive channel-fill deposits exposed on the inner continental shelf, but that the sand ridges also periodically erode and move to the southwest during large storm events. Analyses show that significant storminduced erosion and sediment transport occurs far seaward of the 5 to 9 m depth of closure assumed for Fire Island, where it is thought that an onshore-directed sediment flux from the inner continental shelf to the littoral system is required to balance the coastal sediment budget. It is also thought that the morphology of the shoreface-attached sand ridges controls the persistent shape of the adjacent shoreline through modification of incident waves. Thus, we suggest that the sediment dynamics of the inner continental shelf and both storminduced and anthropogenic modification of the field of shoreface-attached sand ridges be considered in future coastal resiliency planning.

Eastern U.S. Continental Shelf Carbon Budget: Integrating Models,Data Assimilation, and Analysis

NASA Technical Reports Server (NTRS)

Hofmann, Eileen; Mannino, Antonio; McClain, Charles R.

2007-01-01

The U.S. East Coast Continental Shelf (USECoS) project was initiated in 2004 with the overall goal of developing carbon budgets for Mid-Atlantic and South Atlantic regions of the eastern U.S. coast. We addressed this goal through a series of specific research questions that were designed to understand carbon inputs and fates in the two regions, dominant food web pathways for carbon cycling, and similarities/differences in carbon cycling in the two continental shelf systems. The USECoS project represents a major effort to simultaneously synthesize and integrate diverse data sets, field measurements, models, and modeling approaches. We expect that the type of approach taken here will result in more insight than would be possible if each component of the program moved forward independently. The primary significance of this project is in providing a strong quantitative basis for the development of future observational and modeling studies of carbon budgets of continental shelf systems. A strong aspect of the USECoS project is the integration of modeling and extensive physical, chemical, and biological data sets, which provides an opportunity for modeling and data analyses to inform one another from the outset. This research is particularly germane to NASA's carbon cycle research focus and coastal research initiative and the U.S. Climate Change Research Program, all of which support the goals of the North American Carbon Program. We highlight primary approaches that have been used, and some of the challenges and results that have come from interactions among our team of investigators. The global scale and interdisciplinary nature of the science questions that we now face in Earth Science are such that integrated teams of investigators are needed to address them.

76 FR 70156 - Proposed 5-Year Outer Continental Shelf (OCS) Oil and Gas Leasing Program for 2012-2017

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-10

.... BOEM requests comments from states, local governments, native groups, Tribes, the oil and gas industry... Analysis for the OCS 5-Year Program 2012-2017: Theory and Methodology (BOEM 050-2011), a paper containing a...

78 FR 55230 - Safety and Environmental Management System Requirements for Vessels on the U.S. Outer Continental...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-10

... that incorporates the management program and principles of API RP 75 is appropriate for vessels engaged... which would incorporate the management program and principles of API RP 75. Table 1 shows the current... to develop, implement, and maintain a SEMS that incorporates the management program and principles of...

Academic Quality Control: The Case of College Programs on Military Bases.

ERIC Educational Resources Information Center

Bailey, Stephen K.

The quality of college programs at 13 U.S. military bases and the activities of various agencies for maintaining quality control were evaluated. Based on site visits to military bases in the continental United States and Hawaii in 1978, some academic programs appeared to have few standards and practices that promote quality. It is claimed that…

Ocean Dynamics: Vietnam DRI

DTIC Science & Technology

2014-09-30

floor. OBJECTIVES To identify the phenomena involved in the cascade of energy from mesoscales to turbulent scales. In particular, we wish to quantify the...data from the profiler to the surface buoy. The WW Iridium telemetry system was tested on the WW moored over the continental shelf. Telemetry...2580 email: ajlucas@ucsd.edu Award: N00014-12-1-0635 LONG-TERM GOALS To gain a more complete understanding of ocean dynamical processes

Dynamics of continental rift propagation: the end-member modes

NASA Astrophysics Data System (ADS)

Van Wijk, J. W.; Blackman, D. K.

2005-01-01

An important aspect of continental rifting is the progressive variation of deformation style along the rift axis during rift propagation. In regions of rift propagation, specifically transition zones from continental rifting to seafloor spreading, it has been observed that contrasting styles of deformation along the axis of rift propagation are bounded by shear zones. The focus of this numerical modeling study is to look at dynamic processes near the tip of a weak zone in continental lithosphere. More specifically, this study explores how modeled rift behavior depends on the value of rheological parameters of the crust. A three-dimensional finite element model is used to simulate lithosphere deformation in an extensional regime. The chosen approach emphasizes understanding the tectonic forces involved in rift propagation. Dependent on plate strength, two end-member modes are distinguished. The stalled rift phase is characterized by absence of rift propagation for a certain amount of time. Extension beyond the edge of the rift tip is no longer localized but occurs over a very wide zone, which requires a buildup of shear stresses near the rift tip and significant intra-plate deformation. This stage represents a situation in which a rift meets a locked zone. Localized deformation changes to distributed deformation in the locked zone, and the two different deformation styles are balanced by a shear zone oriented perpendicular to the trend. In the alternative rift propagation mode, rift propagation is a continuous process when the initial crust is weak. The extension style does not change significantly along the rift axis and lengthening of the rift zone is not accompanied by a buildup of shear stresses. Model predictions address aspects of previously unexplained rift evolution in the Laptev Sea, and its contrast with the tectonic evolution of, for example, the Gulf of Aden and Woodlark Basin.

Improving global paleogeographic reconstructions since the Devonian using paleobiology

NASA Astrophysics Data System (ADS)

Cao, Wenchao; Zahirovic, Sabin; Williams, Simon; Flament, Nicolas; Müller, Dietmar

2017-04-01

Paleogeographic reconstructions are important to understand past eustatic and regional sea level change, the tectonic evolution of the planet, hydrocarbon genesis, and to constrain and interpret the dynamic topography predicted by time-dependent global mantle convection models. Several global paleogeographic compilations have been published, generally presented as static snapshots with varying temporal resolution and fixed spatial resolution. Published paleogeographic compilations are tied to a particular plate motion model, making it difficult to link them to alternative digital plate tectonic reconstructions. In order to address this issue, we developed a workflow to reverse-engineer reconstructed paleogeographies to their present-day coordinates and link them to any reconstruction model. Published paleogeographic compilations are also tied to a given dataset. We used fossil data from the Paleobiology Database to identify inconsistencies between fossils paleoenvironments and paleogeographic reconstructions, and to improve reconstructed terrestrial-marine boundaries by resolving these inconsistencies. We used the improved reconstructed paleogeographies to estimate the surface areas of global paleogeographic features (shallow marine environments, landmasses, mountains and ice sheets), to investigate the global continental flooding history since the late Paleozoic, which has inherent links to global eustasy as well as dynamic topography. Finally, we discuss the relationships between our modeled emerged land area and total continental area through time, continental growth models, and strontium isotope (87Sr/86Sr) signatures in ocean water. Our study highlights the flexibility of digital paleogeographic models linked to state-of-the-art plate tectonic reconstructions in order to better understand the interplay of continental growth and eustasy, with wider implications for understanding Earth's paleotopography, ocean circulation, and the role of mantle convection in shaping long-wavelength topography.

Random-access technique for modular bathymetry data storage in a continental shelf wave refraction program

NASA Technical Reports Server (NTRS)

Poole, L. R.

1974-01-01

A study was conducted of an alternate method for storage and use of bathymetry data in the Langley Research Center and Virginia Institute of Marine Science mid-Atlantic continental-shelf wave-refraction computer program. The regional bathymetry array was divided into 105 indexed modules which can be read individually into memory in a nonsequential manner from a peripheral file using special random-access subroutines. In running a sample refraction case, a 75-percent decrease in program field length was achieved by using the random-access storage method in comparison with the conventional method of total regional array storage. This field-length decrease was accompanied by a comparative 5-percent increase in central processing time and a 477-percent increase in the number of operating-system calls. A comparative Langley Research Center computer system cost savings of 68 percent was achieved by using the random-access storage method.

76 FR 23331 - Outer Continental Shelf (OCS) Scientific Committee (SC); Announcement of Plenary Session

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-26

...., biology/ecology, physical sciences, and social sciences) to review the specific studies plans of the... Studies Program, Environmental Division, Bureau of Ocean Energy Management, Regulation and Enforcement... feasibility, appropriateness, and scientific value of the OCS Environmental Studies Program to the Secretary...

Developing partnerships for implementing continental-scale citizen science programs at the local-level

NASA Astrophysics Data System (ADS)

Newman, S. J.; Henderson, S.; Ward, D.

2012-12-01

Project BudBurst is a citizen science project focused on monitoring plant phenology that resides at the National Ecological Observatory Network (NEON, Inc). A central question for Project BudBurst and other national outreach programs is: what are the most effective means of engaging and connecting with diverse communities throughout the country? How can continental scale programs like NEON's Project BudBurst engage audiences in such a way as to be relevant at both the local and continental scales? Staff with Project BudBurst pursued partnerships with several continental scale organizations: the National Wildlife Refuge System, the National Park Service, and botanic gardens to address these questions. The distributed nature of wildlife refuges, national parks, and botanic gardens around the country provided the opportunity to connect with participants locally while working with leadership at multiple scales. Project BudBurst staff talked with hundreds of staff and volunteers prior to setting a goal of obtaining and developing resources for several Refuge Partners, a pilot National Park partner, and an existing botanic garden partner during 2011. We were especially interested in learning best practices for future partnerships. The partnership efforts resulted in resource development for 12 Refuge partners, a pilot National Park partner, and 2 botanic garden partners. Early on, the importance of working with national level leaders to develop ownership of the partner program and input about resource needs became apparent. Once a framework for the partnership program was laid out, it became critical to work closely with staff and volunteers on the ground to ensure needs were met. In 2012 we began to develop an online assessment to allow our current and potential partners to provide feedback about whether or not the partnership program was meeting their needs and how the program could be improved. As the year progressed, the timeline for resource development became more of a suggestion than a set schedule. Maintaining flexibility was critical to the success of the partnerships. Unanticipated fieldwork, new priorities within organizations, and differing levels of involvement from partner staff, advisory boards, or Friends groups, led to varying resource development timelines. The distributed nature of and the willingness of partner staff and volunteers to implement Project BudBurst at their facilities have broadened the participation of the public in this program more than could have been accomplished alone. The new partners benefit from the free and customized education and outreach materials provided by Project BudBurst, while Project BudBurst benefits from the local knowledge and contacts with the public from the partner organizations.

Where does subduction initiate and die? Insights from global convection models with continental drift

NASA Astrophysics Data System (ADS)

Ulvrova, Martina; Williams, Simon; Coltice, Nicolas; Tackley, Paul

2017-04-01

Plate tectonics is a prominent feature on Earth. Together with the underlying convecting mantle, plates form a self-organized system. In order to understand the dynamics of the coupled system, subduction of the lithospheric plates plays the key role since it links the exterior with the interior of the planet. In this work we study subduction initiation and death with respect to the position of the continental rafts. Using thermo-mechanical numerical calculations we investigate global convection models featuring self-consistent plate tectonics and continental drifting employing a pseudo-plastic rheology and testing the effect of a free surface. We consider uncompressible mantle convection in Boussinesq approximation that is basaly and internaly heated. Our calculations indicate that the presence of the continents alterns stress distribution within a certain distance from the margins. Intra-oceanic subudction initiation is favorable during super-continent cycles while the initiation at passive continental margin prevails when continents are dispersed. The location of subduction initiation is additionally controlled by the lithospheric strength. Very weak lithosphere results in domination of intra-oceanic subduction initiation. The subduction zones die more easily in the vicinity of the continent due to the strong rheological contrast between the oceanic and continental lithosphere. In order to compare our findings with subduction positions through time recorded on Earth, we analyse subduction birth in global plate reconstruction back to 410 My.

Relief evolution of the Continental Rift of Southeast Brazil revealed by in situ-produced 10Be concentrations in river-borne sediments

NASA Astrophysics Data System (ADS)

Salgado, André Augusto Rodrigues; Rezende, Eric de Andrade; Bourlès, Didier; Braucher, Régis; da Silva, Juliana Rodrigues; Garcia, Ricardo Alexandrino

2016-04-01

This study aims to quantify the denudation dynamics of the Brazilian passive margin along a segment of the Continental Rift of Southeast Brazil. The denudation rates of 30 basins that drain both horsts of the continental rift, including the mountain ranges of the Serra do Mar (seaside horst); and the Serra da Mantiqueira (continental horst); were derived from 10Be concentrations measured in sand-sized river sediment. The mean denudation rate ranges from 9.2 m Ma-1 on the plateau of the Serra do Mar to 37.1 m Ma-1 along the oceanic escarpment of the Serra do Mar. The seaward-facing scarps of both mountain ranges exhibit mean denudation rates that are approximately 1.5 times those of the inland-facing scarps. The escarpments of the horst nearer to the ocean (Serra do Mar) exhibit higher denudation rates (mean 30.2 m Ma-1) than the escarpments of the continental horst (Serra da Mantiqueira) (mean 16.5 m Ma-1). The parameters that impact these denudation rates include the catchment relief, the slope gradient, the rock and the climate. The incongruent combination of a mountainous landscape and moderate to low 10Be-based denudation rates averaging at ∼20 m Ma-1 suggests a reduction in intraplate tectonic activity beginning in the Middle Quaternary or earlier.

Precipitation-Lightning Relationships on a Global Basis and a Study of Tropical Continental Convection in TRMM Brazil

NASA Technical Reports Server (NTRS)

Williams, Earle R.

2001-01-01

This report is concerned with a summary of work completed under NASA Grant NAG5-4778 entitled: "Precipitation-Lightning Relationships on a Global Basis", with a supplement entitled: "A Study of Tropical Continental Convection in TRMM/Brazil". Several areas of endeavor are summarized, some of them concerned directly with the observations from the TRMM satellite, and others focussing on ground based measurements in the NASA TRMM LBA field program in Brazil.

Corrigendum to ;Stirring by deep cyclones and the evolution of Denmark strait overflow water observed at Line W; [Deep-Sea Res. I 109, 10-26

NASA Astrophysics Data System (ADS)

Andres, M.; Toole, J. M.; Torres, D. J.; Smethie, W. M.; Joyce, T. M.; Curry, R. G.

2017-03-01

The Line W program was a 10-year study (2004-2014) to investigate variability in the Deep Western Boundary Current (DWBC) and the nearby ocean interior south of New England. Line W stretches from the Middle Atlantic Bight continental slope southeastward towards Bermuda along a satellite altimeter track and is roughly orthogonal to the 2500-3500 m isobaths along the continental slope here (Fig. 1a).

Oil-Spill Analysis: Gulf of Mexico Outer Continental Shelf (OCS) Lease Sales, Eastern Planning Area, 2003-2007 and Gulfwide OCS Program, 2003-2042

NASA Astrophysics Data System (ADS)

2002-09-01

The Federal Government plans to offer U.S. Outer Continental Shelf (OCS) lands in the Eastern Planning Area of the Gulf of Mexico (GOM) for oil and gas leasing. This report summarizes results of that analysis, the objective of which was to estimate the risk of oil-spill contact to sensitive offshore and onshore environmental resources and socioeconomic features from oil spills accidentally occurring from the OCS activities.

Seasonal and inter-annual dynamics of suspended sediment at the mouth of the Amazon river: The role of continental and oceanic forcing, and implications for coastal geomorphology and mud bank formation

NASA Astrophysics Data System (ADS)

Gensac, Erwan; Martinez, Jean-Michel; Vantrepotte, Vincent; Anthony, Edward J.

2016-04-01

Fine-grained sediments supplied to the Ocean by the Amazon River and their transport under the influence of continental and oceanic forcing drives the geomorphic change along the 1500 km-long coast northward to the Orinoco River delta. The aim of this study is to give an encompassing view of the sediment dynamics in the shallow coastal waters from the Amazon River mouth to the Capes region (northern part of the Amapa region of Brazil and eastern part of French Guiana), where large mud banks are formed. Mud banks are the overarching features in the dynamics of the Amazon-Orinoco coast. They start migrating northward in the Capes region. Suspended Particulate Matter (SPM) concentrations were calculated from satellite products (MODIS Aqua and Terra) acquired over the period 2000-2013. The Census-X11 decomposition method used to discriminate short-term, seasonal and long-term time components of the SPM variability has rendered possible a robust analysis of the impact of continental and oceanic forcing. Continental forcing agents considered are the Amazon River water discharge, SPM concentration and sediment discharge. Oceanic forcing comprises modelled data of wind speed and direction, wave height and direction, and currents. A 150 km-long area of accretion is detected at Cabo Norte that may be linked with a reported increase in the river's sediment discharge concurrent with the satellite data study period. We also assess the rate of mud bank migration north of Cabo Norte, and highlight its variability. Although we confirm a 2 km y-1 migration rate, in agreement with other authors, we show that this velocity may be up to 5 km y-1 along the Cabo Orange region, and we highlight the effect of water discharge by major rivers debouching on this coastal mud belt in modulating such rates. Finally, we propose a refined sediment transport pattern map of the region based on our results and of previous studies in the area such as the AMASSEDS programme, and discuss the relationship between sediment transport and accumulation patterns and the coastal geomorphology of this region.

The Effect of Plumes on the Dynamics of Supercontinents in a Self-Consistent Plate Tectonics Setting

NASA Astrophysics Data System (ADS)

Jain, C.; Rozel, A.; Tackley, P. J.

2014-12-01

Strong mantle plumes arising from the deep mantle can impose stresses on the continents, thereby facilitating continental rifting and disrupting the supercontinent cycle (Storey, Nature 1995; Santosh et al., Gondwana Research 2009). In recent years, several studies have characterized the relation between the location of the plumes and the continents, but with contradicting observations. While Heron and Lowman (GRL, 2010; Tectonophysics, 2011) propose regions where downwelling has ceased (irrespective of overlying plate) as the preferred location for plumes, O'Neill et al. (Gondwana Research, 2009) show an anti-correlation between the average positions of subducting slabs at continental margins, and mantle plumes at continental/oceanic interiors. Extent of continental motion depends on the heat budget of the mantle (CMB heat flux, radiogenic heating, mantle cooling). CMB heat flux is not well defined; however, the recent determination of core's high thermal conductivity requires a CMB heat flow of at least 12 TW (de Koker et al., PNAS 2012; Pozzo et al., Nature 2012; Gomi et al., PEPI 2013), much higher than early estimates of 3-4 TW (Lay et al., Nature 2008). Thus, it is necessary to characterize the effect of increased CMB heat flux on mantle dynamics. In almost all mantle convection simulations, the top boundary is treated as a free-slip surface whereas Earth's surface is a deformable free surface. Unlike free-slip, a free surface boundary condition allows for the development of topography and leads to realistic single-sided (asymmetric) subduction (Crameri et al., GJI 2012; Crameri et al., GRL 2012). Using StagYY code (Tackley, PEPI 2008), we test (i) the impact of increased basal heating on mantle dynamics with continents and self-consistent plate tectonics, including whether plumes prefer to develop under continents; (ii) the influence of a free surface on continents using the 'sticky air' approach, in which a low density and a small viscosity fluid layer is added to the top of the model. The existing model from Rolf et al. (EPSL 2012) is developed further but with weaker continents.

Onshore-offshore movement of jumbo squid (Dosidicus gigas) on the continental shelf

NASA Astrophysics Data System (ADS)

Stewart, Julia S.; Gilly, William F.; Field, John C.; Payne, John C.

2013-10-01

Jumbo squid (Dosidicus gigas) have greatly extended their range in the California Current System, where they forage on a variety of ecologically and economically important species that inhabit both coastal and offshore mesopelagic regions. Swimming abilities and behavior are important factors in assessing the impacts of this range expansion, particularly in regard to foraging in conjunction with onshore-offshore movement over the continental shelf. Here we describe a study of horizontal movements by jumbo squid along and across the continental shelf off Washington, USA, using acoustic tags in association with the Census of Marine Life's Pacific Ocean Shelf Tracking Program (POST) receiver arrays. We detected frequent movements along the shelf break, movement onto the shelf at night, and no evidence of movement as a cohesive school. Our results demonstrate feasibility of using acoustic tags and arrays to document horizontal movements of jumbo squid along and across the continental shelf. This is important in order to determine how those movements overlap with those of other ecologically and commercially important fish species.

Integrated Remote Sensing and Wavelet Analyses for Screening Short-term Teleconnection Patterns in Northeast America

EPA Science Inventory

Global sea surface temperature (SST) anomalies have a demonstrable effect on vegetation dynamics and precipitation patterns throughout the continental U.S. SST variations have been correlated with greenness (vegetation densities) and precipitation via ocean-atmospheric interactio...

Footprint of recycled water subsidies downwind of Lake Michigan

USDA-ARS?s Scientific Manuscript database

Continental evaporation is a significant and dynamic flux within the atmospheric water budget, but few methods provide robust observational constraints on the large-scale hydroclimatological and hydroecological impacts of this ‘recycled-water’ flux. We demonstrate a geospatial analysis that provides...

Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

USGS Publications Warehouse

Levin, Lisa A.; Liu, Kon-Kee; Emeis, Kay-Christian; Breitburg, Denise L.; Cloern, James; Deutsch, Curtis; Giani, Michele; Goffart, Anne; Hofmann, Eileen E.; Lachkar, Zouhair; Limburg, Karin; Liu, Su-Mei; Montes, Enrique; Naqvi, Wajih; Ragueneau, Olivier; Rabouille, Christophe; Sarkar, Santosh Kumar; Swaney, Dennis P.; Wassman, Paul; Wishner, Karen F.

2014-01-01

The ocean’s continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services including primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

NASA Astrophysics Data System (ADS)

Levin, Lisa A.; Liu, Kon-Kee; Emeis, Kay-Christian; Breitburg, Denise L.; Cloern, James; Deutsch, Curtis; Giani, Michele; Goffart, Anne; Hofmann, Eileen E.; Lachkar, Zouhair; Limburg, Karin; Liu, Su-Mei; Montes, Enrique; Naqvi, Wajih; Ragueneau, Olivier; Rabouille, Christophe; Sarkar, Santosh Kumar; Swaney, Dennis P.; Wassman, Paul; Wishner, Karen F.

2015-01-01

The oceans' continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins, (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services. These include primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

Mapping continental-scale biomass burning and smoke palls over the Amazon basin as observed from the Space Shuttle

NASA Technical Reports Server (NTRS)

Helfert, Michael R.; Lulla, Kamlesh P.

1990-01-01

Space Shuttle and Skylab-3 photography has been used to map the areal extent of Amazonian smoke palls associated with biomass burning (1973-1988). Areas covered with smoke have increased from approximately 300,000 sq km in 1973 to continental-size smoke palls measuring approximately 3,000,000 sq km in 1985 and 1988. Mapping of these smoke palls has been accomplished using space photography mainly acquired during Space Shuttle missions. Astronaut observations of such dynamic and vital environmental phenomena indicate the possibility of integrating the earth observation capabilities of all space platforms in future Global Change research.

30 CFR 250.911 - If my platform is subject to the Platform Verification Program, what must I do?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false If my platform is subject to the Platform Verification Program, what must I do? 250.911 Section 250.911 Mineral Resources BUREAU OF SAFETY AND... CONTINENTAL SHELF Platforms and Structures Platform Verification Program § 250.911 If my platform is subject...

30 CFR 250.911 - If my platform is subject to the Platform Verification Program, what must I do?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false If my platform is subject to the Platform Verification Program, what must I do? 250.911 Section 250.911 Mineral Resources BUREAU OF SAFETY AND... CONTINENTAL SHELF Platforms and Structures Platform Verification Program § 250.911 If my platform is subject...

30 CFR 250.911 - If my platform is subject to the Platform Verification Program, what must I do?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false If my platform is subject to the Platform Verification Program, what must I do? 250.911 Section 250.911 Mineral Resources BUREAU OF SAFETY AND... CONTINENTAL SHELF Platforms and Structures Platform Verification Program § 250.911 If my platform is subject...

78 FR 65705 - Request for Comments on the Annual Progress Report on the Outer Continental Shelf (OCS) Oil and...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-01

... (Five Year Program). The Annual Progress Report is available for review at: www.boem.gov/Five-Year-Program-Annual-Progress-Report/ . Information on the Five Year Program is available online at http://www... final on August 27, 2012, after the required 60-day congressional review period. Section 18(e) of the...

28 CFR 0.40 - General functions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... proposed acquisitions under the Savings and Loan Holding Company Amendments of 1967 (12 U.S.C. 1730a(e...)), furnishing advice on oil and gas leasing under the Outer Continental Shelf Lands Act Amendments of 1978 (43 U... programs or agreements and small business production or raw material pools, the national defense program...

28 CFR 0.40 - General functions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... proposed acquisitions under the Savings and Loan Holding Company Amendments of 1967 (12 U.S.C. 1730a(e...)), furnishing advice on oil and gas leasing under the Outer Continental Shelf Lands Act Amendments of 1978 (43 U... programs or agreements and small business production or raw material pools, the national defense program...

28 CFR 0.40 - General functions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... proposed acquisitions under the Savings and Loan Holding Company Amendments of 1967 (12 U.S.C. 1730a(e...)), furnishing advice on oil and gas leasing under the Outer Continental Shelf Lands Act Amendments of 1978 (43 U... programs or agreements and small business production or raw material pools, the national defense program...

28 CFR 0.40 - General functions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... proposed acquisitions under the Savings and Loan Holding Company Amendments of 1967 (12 U.S.C. 1730a(e...)), furnishing advice on oil and gas leasing under the Outer Continental Shelf Lands Act Amendments of 1978 (43 U... programs or agreements and small business production or raw material pools, the national defense program...

Marine Program Annual Report 1973.

ERIC Educational Resources Information Center

New Hampshire Univ., Durham. Marine Program.

This report describes the activities of a program designed to develop the information and systems necessary for managing the Continental Shelf and Coastal Zone of Northern New England. Ten research areas or projects are discussed: aquaculture, biology and ecology, coastal oceanography, buoy systems studies, man in the sea, marine platforms and…

Special Topics Courses - A Happy Medium between Mini-Courses and Full-Coverage Courses.

ERIC Educational Resources Information Center

Carpenter, John R.; And Others

1979-01-01

Describes a special topics program which allows students some choice in content to be studied. Topics include Continental Drift and Ice Ages, Geology and National Parks, the Coast of South Carolina, and Medical Geology. Student evaluations indicate positive attitudes towards the program. (MA)

Ecological Condition of Coastal Ocean Waters along the U.S. Western Continental Shelf: 2003

EPA Science Inventory

The western National Coastal Assessment program of EPA, in conjunction with the NOAA National Ocean Service, west coast states (WA, OR, and CA), and the Southern California Coastal Water Research Project Bight ’03 program, assessed the ecological condition of soft sediment habita...

Global changes in biogeochemical cycles in response to human activities

NASA Technical Reports Server (NTRS)

Moore, Berrien, III; Melillo, Jerry

1994-01-01

The main objective of our research was to characterize biogeochemical cycles at continental and global scales in both terrestrial and aquatic ecosystems. This characterization applied to both natural ecosystems and those disturbed by human activity. The primary elements of interest were carbon and nitrogen and the analysis sought to quantify standing stocks and dynamic cycling processes. The translocation of major nutrients from the terrestrial landscape to the atmosphere (via trace gases) and to fluvial systems (via leaching, erosional losses, and point source pollution) were of particular importance to this study. Our aim was to develop the first generation of Earth System Models. Our research was organized around the construction and testing of component biogeochemical models which treated terrestrial ecosystem processes, aquatic nutrient transport through drainage basins, and trace gas exchanges at the continental and global scale. A suite of three complementary models were defined within this construct. The models were organized to operate at a 1/2 degree latitude by longitude level of spatial resolution and to execute at a monthly time step. This discretization afforded us the opportunity to understand the dynamics of the biosphere down to subregional scales, while simultaneously placing these dynamics into a global context.

The importance of planetary rotation period for ocean heat transport.

PubMed

Cullum, J; Stevens, D; Joshi, M

2014-08-01

The climate and, hence, potential habitability of a planet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions. However, previous studies of planetary climate have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans, which neglects or misrepresents the effect of the ocean in the total heat transport. Even the majority of studies with a dynamic ocean have used a simple so-called aquaplanet that has no continental barriers, which is a configuration that dramatically changes the ocean dynamics. Here, the significance of the response of poleward ocean heat transport to planetary rotation period is shown with a simple meridional barrier--the simplest representation of any continental configuration. The poleward ocean heat transport increases significantly as the planetary rotation period is increased. The peak heat transport more than doubles when the rotation period is increased by a factor of ten. There are also significant changes to ocean temperature at depth, with implications for the carbon cycle. There is strong agreement between the model results and a scale analysis of the governing equations. This result highlights the importance of both planetary rotation period and the ocean circulation when considering planetary habitability.

A multidisciplinary Earth science research program in China

NASA Astrophysics Data System (ADS)

Dong, Shuwen; Li, Tingdong; Gao, Rui; Hou, Hesheng; Li, Yingkang; Zhang, Shihong; Keller, G. Randy; Liu, Mian

2011-09-01

Because China occupies a large and geologically complex region of central and eastern Asia, the country may hold the keys to resolving many basic problems in the Earth sciences, such as how continental collision with India produced China's interconnected array of large intraplate structures, and what links exist between these structures and natural resources. To learn more, the Chinese government has launched SinoProbe, a major research initiative focusing on multidisciplinary imaging of the three-dimensional (3-D) structure and composition of the Chinese continental lithosphere and its evolution through geologic history. This effort is also motivated by China's need for a comprehensive and systematic evaluation of its natural resources and a better understanding of potential geohazards. SinoProbe is funded by the Chinese Ministry of Finance, managed by the Chinese Ministry of Land and Resources, and organized by the Chinese Academy of Geological Sciences. More than 960 investigators and engineers are currently involved with the program, not counting international collaborators. Most of them are affiliated with the Chinese Academy of Geological Sciences, the Chinese Academy of Sciences, the Ministry of Education (i.e., universities), and the China Earthquake Administration. The initial phase of the program (2008-2012), with funding equivalent to about US$164 million, is testing the feasibility of new technologies in geophysical and geochemical exploration and deep continental drilling by focusing on a series of profiles (Figure 1).

Tick-, mosquito-, and rodent-borne parasite sampling designs for the National Ecological Observatory Network

USGS Publications Warehouse

Springer, Yuri P.; Hoekman, David; Johnson, Pieter T. J.; Duffy, Paul A.; Hufft, Rebecca A.; Barnett, David T.; Allan, Brian F.; Amman, Brian R.; Barker, Christopher M.; Barrera, Roberto; Beard, Charles B.; Beati, Lorenza; Begon, Mike; Blackmore, Mark S.; Bradshaw, William E.; Brisson, Dustin; Calisher, Charles H.; Childs, James E.; Diuk-Wasser, Maria A.; Douglass, Richard J.; Eisen, Rebecca J.; Foley, Desmond H.; Foley, Janet E.; Gaff, Holly D.; Gardner, Scott L.; Ginsberg, Howard; Glass, Gregory E.; Hamer, Sarah A.; Hayden, Mary H.; Hjelle, Brian; Holzapfel, Christina M.; Juliano, Steven A.; Kramer, Laura D.; Kuenzi, Amy J.; LaDeau, Shannon L.; Livdahl, Todd P.; Mills, James N.; Moore, Chester G.; Morand, Serge; Nasci, Roger S.; Ogden, Nicholas H.; Ostfeld, Richard S.; Parmenter, Robert R.; Piesman, Joseph; Reisen, William K.; Savage, Harry M.; Sonenshine, Daniel E.; Swei, Andrea; Yabsley, Michael J.

2016-01-01

Parasites and pathogens are increasingly recognized as significant drivers of ecological and evolutionary change in natural ecosystems. Concurrently, transmission of infectious agents among human, livestock, and wildlife populations represents a growing threat to veterinary and human health. In light of these trends and the scarcity of long-term time series data on infection rates among vectors and reservoirs, the National Ecological Observatory Network (NEON) will collect measurements and samples of a suite of tick-, mosquito-, and rodent-borne parasites through a continental-scale surveillance program. Here, we describe the sampling designs for these efforts, highlighting sampling priorities, field and analytical methods, and the data as well as archived samples to be made available to the research community. Insights generated by this sampling will advance current understanding of and ability to predict changes in infection and disease dynamics in novel, interdisciplinary, and collaborative ways.

Heat flow pattern in the gas hydrate drilling areas of northern south china sea and the implication for further study

NASA Astrophysics Data System (ADS)

Wang, Lifeng; Sha, Zhibin

2015-04-01

Numerous seismic reflection profiles have been acquired by China Geological Survey (CGS) in the Northern Slope of South China Sea (SCS), clearly indicating widespread occurrence of free gases and/or gas hydrates in the sediments. In the year 2007 and 2013 respectively the gas hydrate samples are successfully recovered during two offshore drilling exploratory programs. Results of geothermal data during previous field studies along the north continental margin, however, show that the gas hydrate sites are associated with high geothermal background in contrast to the other offshore ones where the gas hydrates are more likely to be found in the low geothermal regional backgrounds. There is a common interesting heat flow pattern during the two drilling expeditions that the gas hydrate occurrences coincide with the presences of comparatively low geothermal anomalies against the high thermal background which is mainly caused by concentrated fluid upward movements into the stability zone (GHSZ) detected by the surface heat flow measurements over the studied fields. The key point for understanding the coupling between the presences of the gas hydrates and heat flow pattern at regional scale is to know the cause of high heat flows and the origin of forming gases at depth. We propose that these high heat flows are attributed to elevated shallow fault-fissure system due to the tectonic activities. A remarkable series of vertical faults and fissures are common on the upper continental slope and the forming gases are thought to have migrated with hot advective fluid flows towards seafloor mainly via fault-fissure system from underlying source rocks which are deeper levels than those of the GHSZ. The present study is based on an extensive dataset on hydrate distribution and associated temperature field measurements collected in the vicinity of studied areas during a series of field expeditions organized within the framework of national widely collaborative projects. Those observations bring new insights to our growing understanding of the stability of this dynamic hydrate reservoir in the continental margin shallow subsurface, and alert us that occurrence patterns may be more complex than previously thought. So the future aim of this program is to better understand the factors constraining the distribution of hydrate deposits, and the processes involved in gas hydrate formation.

Preliminary results from 2017 OGS Explora cruise to the Ross Sea continental slope

NASA Astrophysics Data System (ADS)

Rebesco, Michele; De Santis, Laura; Gales, Jenny; Kim, Sookwan; Liu, Yanguang; Sauli, Chiara; Cuffaro, Marco; Bergamasco, Andrea; Colleoni, Florence; Kovacevic, Vedrana; Olivo, Elisabetta; Florindo-Lopez, Cristian; Codiglia, Riccardo; Zgur, Fabrizio; Accettella, Daniela; Gordini, Emiliano; Visnovic, Paolo; Tomini, Isabella; Mansutti, Paolo; Sterzai, Paolo

2017-04-01

OGS Explora is back to Antarctica for three projects focused on the Ross Sea eastern continental slope: EU/FP7-EUROFLEETS (http://www.eurofleets.eu) ANTSSS, PNRA (Programma Nazionale Di Ricerche in Antartide) ODYSSEA, and PNRA WHISPERS. These projects employ three main methods: 1) geophysics (multichannel seismic reflection, sub-bottom and multibeam morphobathymetric survey); 2) geology (gravity corer and box-corer); oceanography (CTD, LADCP, turbulence). The general objective is to contribute to the understanding of past and present ocean dynamics and glacial history of this Antarctic sector. In particular, to find evidence (in the geometry and distribution of the stratigraphic sequences) of Miocene-Pleistocene West Antarctic Ice Sheet and East Antarctic Ice Sheet advances and retreats and of their effects on Ross Sea Bottom Water formation and dynamics. The gravity cores provide the chronological control for the Quaternary. Deep sea drilling (through IODP Exp. 374, whose additional alternative sites are surveyed during this cruise) will provide the chronological control for the pre-Quaternary seismic sequences.

Cradles and museums of Antarctic teleost biodiversity.

PubMed

Dornburg, Alex; Federman, Sarah; Lamb, April D; Jones, Christopher D; Near, Thomas J

2017-09-01

Isolated in one of the most extreme marine environments on Earth, teleost fish diversity in Antarctica's Southern Ocean is dominated by one lineage: the notothenioids. Throughout the past century, the long-term persistence of this unique marine fauna has become increasingly threatened by regional atmospheric and, to a lesser extent oceanic, warming. Developing an understanding of how historical temperature shifts have shaped source-sink dynamics for Antarctica's teleost lineages provides critical insight for predicting future demographic responses to climate change. We use a combination of phylogenetic and biogeographic modelling to show that high-latitude Antarctic nearshore habitats have been an evolutionary sink for notothenioid species diversity. Contrary to expectations from island biogeographic theory, lower latitude regions of the Southern Ocean that include the northern Antarctic Peninsula and peripheral island archipelagos act as source areas to continental diversity. These peripheral areas facilitate both the generation of new species and repeated colonization of nearshore Antarctic continental regions. Our results provide historical context to contemporary trends of global climate change that threaten to invert these evolutionary dynamics.

A new instrument system to investigate sediment dynamics on continental shelves

USGS Publications Warehouse

Cacchione, D.A.; Drake, D.E.

1979-01-01

A new instrumented tripod, the GEOPROBE system, has been constructed and used to collect time-series data on physical and geological parameters that are important in bottom sediment dynamics on continental shelves. Simultaneous in situ digital recording of pressure, temperature, light scattering, and light transmission, in combination with current velocity profiles measured with a near-bottom vertical array of electromagnetic current meters, is used to correlate bottom shear generated by a variety of oceanic processes (waves, tides, mean flow, etc.) with incipient movement and resuspension of bottom sediment. A bottom camera system that is activated when current speeds exceed preset threshold values provides a unique method to identify initial sediment motion and bed form development. Data from a twenty day deployment of the GEOPROBE system in Norton Sound, Alaska, during the period September 24 - October 14, 1976 show that threshold conditions for sediment movement are commonly exceeded, even in calm weather periods, due to the additive effects of tidal currents, mean circulation, and surface waves. ?? 1979.

High-Resolution geophysical data from the inner continental shelf at Vineyard Sound, Massachusetts

USGS Publications Warehouse

Andrews, Brian D.; Ackerman, Seth D.; Baldwin, Wayne E.; Foster, David S.; Schwab, William C.

2013-01-01

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have mapped approximately 340 square kilometers of the inner continental shelf in Vineyard Sound, Massachusetts, under a cooperative mapping program. The geophysical data collected between 2009 and 2011 by the U.S. Geological Survey as part of this program are published in this report. The data include (1) swath bathymetry from interferometric sonar, (2) acoustic backscatter from sidescan sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These data were collected to support research on the influence of sea-level change and sediment supply on coastal evolution and sediment transport processes and to provide baseline seabed characterization information required for management of coastal and offshore resources within the coastal zone of Massachusetts.

Continental United States Military Housing Inspection National Capital Region

DTIC Science & Technology

2015-08-13

that was flaking, peeling, or chalking. JBAB did not have an asbestos management program, plan, or an appointed asbestos program manager...housing partner to ensure inspection and maintenance plan is achieved; and • Implement an asbestos management plan and appoint an asbestos program...select environmental health and safety requirements, such as those for drinking water, radon, asbestos , and lead based paint. We conducted this

Anomalous Subsidence at the Ocean Continent Transition of the Gulf of Aden Rifted Continental Margin

NASA Astrophysics Data System (ADS)

Cowie, Leanne; Kusznir, Nick; Leroy, Sylvie

2013-04-01

It has been proposed that some rifted continental margins have anomalous subsidence and that at break-up they were elevated at shallower bathymetries than the isostatic response predicted by classical rift models (McKenzie, 1978). The existence of anomalous syn- or early-post break-up subsidence of this form would have important implications for our understanding of the geodynamics of continental break-up and sea-floor spreading initiation. We have investigated subsidence of the young rifted continental margin of the eastern Gulf of Aden, focussing on the western Oman margin (break-up age 17.6 Ma). Lucazeau et al. (2008) have found that the observed bathymetry here is approximately 1 km shallower than the predicted bathymetry. In order to examine the proposition of an anomalous early post break-up subsidence history of the Omani Gulf of Aden rifted continental margin, we have determined the subsidence of the oldest oceanic crust adjacent to the continent-ocean boundary (COB) using residual depth anomaly (RDA) analysis corrected for sediment loading and oceanic crustal thickness variation. RDAs corrected for sediment loading using flexural backstripping and decompaction have been calculated by comparing observed and age predicted oceanic bathymetries in order to identify anomalous subsidence of the Gulf of Aden rifted continental margin. Age predicted bathymetric anomalies have been calculated using the thermal plate model predictions of Crosby and McKenzie (2009). Non-zero RDAs at the Omani Gulf of Aden rifted continental margin can be the result of non standard oceanic crustal thickness or the effect of mantle dynamic topography or a non-classical rift and break-up model. Oceanic crustal basement thicknesses from gravity inversion together with Airy isostasy have been used to predict a "synthetic" gravity RDA, in order to determine the RDA contribution from non-standard oceanic crustal thickness. Gravity inversion, used to determine crustal basement thickness, incorporates a lithosphere thermal gravity anomaly correction and uses sediment thicknesses from 2D seismic data. Reference Moho depths used in the gravity inversion have been calibrated against seismic refraction Moho depths. The difference between the sediment corrected RDA and the "synthetic" gravity derived RDA gives the component of the RDA which is not due to variations in oceanic crustal thickness. This RDA corrected for sediment loading and crustal thickness variation has a magnitude between +600m and +1000m (corresponding to anomalous uplift) and is comparable to that reported (+1km) by Lucazeau et al. (2008). We are unable to distinguish whether this anomalous uplift is due to mantle dynamic topography or anomalous subsidence with respect to classical rift model predictions.

A probabilistic tornado wind hazard model for the continental United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hossain, Q; Kimball, J; Mensing, R

A probabilistic tornado wind hazard model for the continental United States (CONUS) is described. The model incorporates both aleatory (random) and epistemic uncertainties associated with quantifying the tornado wind hazard parameters. The temporal occurrences of tornadoes within the continental United States (CONUS) is assumed to be a Poisson process. A spatial distribution of tornado touchdown locations is developed empirically based on the observed historical events within the CONUS. The hazard model is an aerial probability model that takes into consideration the size and orientation of the facility, the length and width of the tornado damage area (idealized as a rectanglemore » and dependent on the tornado intensity scale), wind speed variation within the damage area, tornado intensity classification errors (i.e.,errors in assigning a Fujita intensity scale based on surveyed damage), and the tornado path direction. Epistemic uncertainties in describing the distributions of the aleatory variables are accounted for by using more than one distribution model to describe aleatory variations. The epistemic uncertainties are based on inputs from a panel of experts. A computer program, TORNADO, has been developed incorporating this model; features of this program are also presented.« less

30 CFR 250.1614 - Mud program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Sulphur Operations § 250.1614... shall comply with requirements concerning mud control, mud test and monitoring equipment, mud quantities...

Sulfate and MSA Aerosol Dynamics in the Marine Boundary Layer

DTIC Science & Technology

1997-09-30

Kilauea Volcano as they move out over the Pacific Ocean, to understand what happens to marine and continental aerosols when they mix. This dataset will...SULFATE AND MSA AEROSOL DYNAMICS IN THE MARINE BOUNDARY LAYER P.I. - Barry J. Huebert Department of Oceanography University of Hawaii 1000 Pope Rd...6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) University of Hawaii

Modeling annual mallard production in the prairie-parkland region

USGS Publications Warehouse

Miller, M.W.

2000-01-01

Biologists have proposed several environmental factors that might influence production of mallards (Anas platyrhynchos) nesting in the prairie-parkland region of the United States and Canada. These factors include precipitation, cold spring temperatures, wetland abundance, and upland breeding habitat. I used long-term historical data sets of climate, wetland numbers, agricultural land use, and size of breeding mallard populations in multiple regression analyses to model annual indices of mallard production. Models were constructed at 2 scales: a continental scale that encompassed most of the mid-continental breeding range of mallards and a stratum-level scale that included 23 portions of that same breeding range. The production index at the continental scale was the estimated age ratio of mid-continental mallards in early fall; at the stratum scale my production index was the estimated number of broods of all duck species within an aerial survey stratum. Size of breeding mallard populations in May, and pond numbers in May and July, best modeled production at the continental scale. Variables that best modeled production at the stratum scale differed by region. Crop variables tended to appear more in models for western Canadian strata; pond variables predominated in models for United States strata; and spring temperature and pond variables dominated models for eastern Canadian strata. An index of cold spring temperatures appeared in 4 of 6 models for aspen parkland strata, and in only 1 of 11 models for strata dominated by prairie. Stratum-level models suggest that regional factors influencing mallard production are not evident at a larger scale. Testing these potential factors in a manipulative fashion would improve our understanding of mallard population dynamics, improving our ability to manage the mid-continental mallard population.

Pan-Continental Droughts in North America over the Last Millennium

NASA Technical Reports Server (NTRS)

Cook, Benjamin I.; Smerdon, Jason E.; Seager, Richard; Cook, Edward R.

2014-01-01

Regional droughts are common in North America, but pan-continental droughts extending across multiple regions, including the 2012 event, are rare relative to single-region events. Here, the tree-ring-derived North American Drought Atlas is used to investigate drought variability in four regions over the last millennium, focusing on pan-continental droughts. During the Medieval Climate Anomaly (MCA), the central plains (CP), Southwest (SW), and Southeast (SE) regions experienced drier conditions and increased occurrence of droughts and the Northwest (NW) experienced several extended pluvials. Enhanced MCA aridity in the SW and CP manifested as multidecadal megadroughts. Notably, megadroughts in these regions differed in their timing and persistence, suggesting that they represent regional events influenced by local dynamics rather than a unified, continental-scale phenomena. There is no trend in pan-continental drought occurrence, defined as synchronous droughts in three or more regions. SW, CP, and SE (SW+CP+SE) droughts are the most common, occurring in 12 percent of all years and peaking in prevalence during the twelfth and thirteenth centuries; patterns involving three other regions occur in about 8 percent of years. Positive values of the Southern Oscillation index (La Nina conditions) are linked to SW, CP, and SE (SW+CP+SE) droughts and SW, CP, and NW (SW+CP+NW) droughts, whereas CP, NW, and SE (CP+NW+SE) droughts are associated with positive values of the Pacific decadal oscillation and Atlantic multidecadal oscillation. While relatively rare, pan-continental droughts are present in the paleo record and are linked to defined modes of climate variability, implying the potential for seasonal predictability. Assuming stable drought teleconnections, these events will remain an important feature of future North American hydroclimate, possibly increasing in their severity in step with other expected hydroclimate responses to increased greenhouse gas forcing.

Patterns in stable isotope ratios of particulate material from the eastern US continental shelf

EPA Science Inventory

Stable isotope measurements of nitrogen and carbon (δ15N, δ13C) in estuarine, nearshore, and open ocean ecosystems are often utilized in order to characterize human influences, elucidate food web dynamics, or better understand nitrogen cycling. Reliable information a...

30 CFR 250.455 - What are the general requirements for a drilling fluid program?

Code of Federal Regulations, 2014 CFR

2014-07-01

... drilling fluid program? 250.455 Section 250.455 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.455 What are the general...

30 CFR 250.455 - What are the general requirements for a drilling fluid program?

Code of Federal Regulations, 2013 CFR

2013-07-01

... drilling fluid program? 250.455 Section 250.455 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.455 What are the general...

30 CFR 250.455 - What are the general requirements for a drilling fluid program?

Code of Federal Regulations, 2012 CFR

2012-07-01

... drilling fluid program? 250.455 Section 250.455 Mineral Resources BUREAU OF SAFETY AND ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.455 What are the general...

30 CFR 250.455 - What are the general requirements for a drilling fluid program?

Code of Federal Regulations, 2010 CFR

2010-07-01

... drilling fluid program? 250.455 Section 250.455 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.455 What are the general requirements for a...

76 FR 4093 - Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-24

... Drilling Programs in the Chukchi and Beaufort Seas, AK AGENCY: National Marine Fisheries Service (NMFS... harassment, by Shell Offshore Inc. (Shell) incidental to offshore exploration drilling on Outer Continental... drilling programs in 2010. ADDRESSES: The applications related to this action are available by writing to...

30 CFR 250.455 - What are the general requirements for a drilling fluid program?

Code of Federal Regulations, 2011 CFR

2011-07-01

... drilling fluid program? 250.455 Section 250.455 Mineral Resources BUREAU OF OCEAN ENERGY MANAGEMENT, REGULATION, AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.455 What are...

National Workplace Literacy Program (NWLP) at Chinatown Manpower Project, Inc. Final Performance Report.

ERIC Educational Resources Information Center

Tse, Ivy Au

The Chinatown Manpower Project continued as the education partner in a Workplace Literacy Program (WLP) for the Chinese garment workers in New York City. Local 23-25, Union of Needletrades, Industrial and Textile Employees, was the union partner; the Greater Blouse, Skirt & Undergarment Association, Inc., and the Continental Garment Manufacturers…

3D geodynamic models for the development of opposing continental subduction zones: The Hindu Kush-Pamir example

NASA Astrophysics Data System (ADS)

Liao, Jie; Gerya, Taras; Thielmann, Marcel; Webb, A. Alexander G.; Kufner, Sofia-Katerina; Yin, An

2017-12-01

The development of opposing continental subduction zones remains scantly explored in three dimensions. The Hindu Kush-Pamir orogenic system at the western end of the Himalayan orogen provides a rare example of continental collision linked to two opposing intra-continental subduction zones. The subducted plates feature a peculiar 3D geometry consisting of two distinct lithospheric fragments with different polarities, subduction angles and slab-curvatures beneath the Hindu Kush and Pamir, respectively. Using 3D geodynamic modeling, we simulate possible development of two opposing continental subduction zones to understand the dynamic evolution of the Hindu Kush-Pamir orogenic system. Our geodynamic model reproduces the major tectonic elements observed: (1) the deeper subduction depth, the steeper dip angle and the southward offset of the Hindu Kush subduction zone relative to the Pamir naturally occur if convergence direction of the subducting Indian plate and dip-direction of the Hindu Kush subduction zone match. (2) The formation of the highly asymmetrically curved Pamir region and the south-dipping subduction is promoted by the initial geometry of the indenting Indian lithosphere together with the existence of a major strike-slip fault on the eastern margin of the Pamir region. (3) Subduction of only the lower continental crust during continental collision can occur if the coupling between upper and lower crusts is weak enough to allow a separation of these two components, and that (4) the subduction of mainly lower crust then facilitates that conditions for intermediate-depth seismicity can be reached. (5) The secondary tectonic features modeled here such as strike-slip-fault growth, north-northwest striking extension zone, and lateral flow of the thickened ductile upper crust are comparable to the current tectonics of the region. (6) Model results are further compared to the potentially similar orogenic system, i.e., the Alpine orogen, in terms of the curved Western Alpine arc and the two opposing subducted slabs beneath the Alps and the Dinarides.

Upwelling rebound, ephemeral secondary pycnoclines, and the creation of a near-bottom wave guide over the Monterey Bay continental shelf

USGS Publications Warehouse

Cheriton, Olivia M.; McPhee-Shaw, Erika E.; Storlazzi, Curt D.; Rosenberger, Kurt J.; Shaw, William J.; Raanan, Ben Y.

2014-01-01

Several sequential upwelling events were observed in fall 2012, using measurements from the outer half of the continental shelf in Monterey Bay, during which the infiltration of dense water onto the shelf created a secondary, near-bottom pycnocline. This deep pycnocline existed in concert with the near-surface pycnocline and enabled the propagation of near-bottom, cold, semidiurnal internal tidal bores, as well as energetic, high-frequency, nonlinear internal waves of elevation (IWOE). The IWOE occurred within 20 m of the bottom, had amplitudes of 8–24 m, periods of 6–45 min, and depth-integrated energy fluxes up to 200 W m−1. Iribarren numbers (<0.03) indicate that these IWOE were nonbreaking in this region of the shelf. These observations further demonstrate how regional upwelling dynamics and the resulting bulk, cross-margin hydrography is a first-order control on the ability of internal waves, at tidal and higher frequencies, to propagate through continental shelf waters.

Comparative phylogeography clarifies the complexity and problems of continental distribution that drove A. R. Wallace to favor islands

PubMed Central

Riddle, Brett R.

2016-01-01

Deciphering the geographic context of diversification and distributional dynamics in continental biotas has long been an interest of biogeographers, ecologists, and evolutionary biologists. Thirty years ago, the approach now known as comparative phylogeography was introduced in a landmark study of a continental biota. Here, I use a set of 455 studies to explore the current scope of continental comparative phylogeography, including geographic, conceptual, temporal, ecological, and genomic attributes. Geographically, studies are more frequent in the northern hemisphere, but the south is catching up. Most studies focus on a Quaternary timeframe, but the Neogene is well represented. As such, explanations for geographic structure and history include geological and climatic events in Earth history, and responses include vicariance, dispersal, and range contraction-expansion into and out of refugia. Focal taxa are biased toward terrestrial or semiterrestrial vertebrates, although plants and invertebrates are well represented in some regions. The use of various kinds of nuclear DNA markers is increasing, as are multiple locus studies, but use of organelle DNA is not decreasing. Species distribution models are not yet widely incorporated into studies. In the future, continental comparative phylogeographers will continue to contribute to erosion of the simple vicariance vs. dispersal paradigm, including exposure of the widespread nature of temporal pseudocongruence and its implications for models of diversification; provide new templates for addressing a variety of ecological and evolutionary traits; and develop closer working relationships with earth scientists and biologists in a variety of disciplines. PMID:27432953

Comparative phylogeography clarifies the complexity and problems of continental distribution that drove A. R. Wallace to favor islands.

PubMed

Riddle, Brett R

2016-07-19

Deciphering the geographic context of diversification and distributional dynamics in continental biotas has long been an interest of biogeographers, ecologists, and evolutionary biologists. Thirty years ago, the approach now known as comparative phylogeography was introduced in a landmark study of a continental biota. Here, I use a set of 455 studies to explore the current scope of continental comparative phylogeography, including geographic, conceptual, temporal, ecological, and genomic attributes. Geographically, studies are more frequent in the northern hemisphere, but the south is catching up. Most studies focus on a Quaternary timeframe, but the Neogene is well represented. As such, explanations for geographic structure and history include geological and climatic events in Earth history, and responses include vicariance, dispersal, and range contraction-expansion into and out of refugia. Focal taxa are biased toward terrestrial or semiterrestrial vertebrates, although plants and invertebrates are well represented in some regions. The use of various kinds of nuclear DNA markers is increasing, as are multiple locus studies, but use of organelle DNA is not decreasing. Species distribution models are not yet widely incorporated into studies. In the future, continental comparative phylogeographers will continue to contribute to erosion of the simple vicariance vs. dispersal paradigm, including exposure of the widespread nature of temporal pseudocongruence and its implications for models of diversification; provide new templates for addressing a variety of ecological and evolutionary traits; and develop closer working relationships with earth scientists and biologists in a variety of disciplines.

Geology of continental margins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

With continued high interest in offshore petroleum exploration, the 1977 AAPG Short Course presents the latest interpretations of new data bearing on the geology and geophysics of continental margins. Seven well-known earth scientists have organized an integrated program covering major topics involved in the development of ocean basins and continental margins with emphasis on the slopes and rises. The discussion of plate tectonics and evolution of continental margins is followed by presentations on the stratigraphy and structure of pull-apart and compressional margins. Prospective petroleum source rocks, their organic content, rate of burial, and distribution on slopes and rises of differentmore » margin types is covered. Prospective reservoir rock patterns are related to depositional processes and to the sedimentary and structural histories for different types of continental margins. Finally, the seismic recognition of depositional facies on slopes and rises for different margin types with varying rates of sediment supply during eustatic sea-level changes are discussed. The course with this syllabus offers an invaluable opportunity for explorationists to refresh their understanding of the geology associated with an important petroleum frontier. In addition, the course sets forth a technical frame of reference for the case-histoy papers to be presented later in the AAPG Research Symposium on the Petroleum Potential of Slopes, Rises, and Plateaus.« less

75 FR 71734 - Outer Continental Shelf (OCS), Scientific Committee (SC)

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-24

... program covers a wide range of field and laboratory studies in biology, chemistry, and physical... SC has 15 vacancies in the following disciplines: Biological oceanography/marine biology; social...

Sedimentological fingerprint of modern and ancient meltwater outbursts across Antarctic continental shelves and slopes

NASA Astrophysics Data System (ADS)

Anderson, J. B.; Simkins, L. M.; Prothro, L. O.

2016-12-01

On formerly glaciated Antarctic continental shelves, the crystalline inner shelf is commonly dissected by linked subglacial lake and channel systems; however, signatures of meltwater are rare within subglacial and glacial-marine deposits on the middle to outer continental shelf. Recent observations of ice-marginal landforms incised by meltwater channels in the western Ross Sea indicate pulses of meltwater outbursts at marine-based grounding lines during deglaciation of the continental shelf. Here we present sedimentological evidence of meltwater outbursts and associated plumes from new and legacy cores collected on the continental shelf and slope within the Ross Sea, Amundsen Sea, and Marguerite Bay. Discrete fine-grained silt deposits are found overlying till and within proximal grounding line deposits and open-marine diatomaceous sediments. The deposits are massive to laminated, contain little to no coarser material, moderately sorted and dominated by a 10 μm grain-size mode. Grain-size measurements show no indication of winnowing; therefore, we interpret these deposits as meltwater deposits, transported by subglacial meltwater drainage systems to the grounding line and dispersed further seaward by meltwater plumes. The similarity of the deposits down-core and between shelf and slope sites within the Ross Sea, Amundsen Sea, and Marguerite Bay indicate that sorting and/or production of the fine silts occurs due to subglacial hydrodynamic processes. These distinctive meltwater deposits within the stratigraphic record provide an accessible proxy for identifying meltwater discharge from the Antarctic Ice Sheet and potentially be used to correlate cores on and off the continental shelf. Dating events on the continental shelf is notoriously difficult; therefore, deeper ocean records offer an easier means of bracketing the timing of meltwater discharge events. Longer records of ice dynamics from off the continental shelf are commonly used to reconstruct IRD records, and now can be used to reconstruct meltwater discharge histories, perhaps even extending back to warmer periods when the Antarctic Ice Sheet was a more temperate system that experienced seasonal surface melt, similar to the modern Greenland Ice Sheet.

Impacts of Suspended Sediment and Estuarine - Shelf Exchange Pathways on Shelf Ecosystem Dynamics in the Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Wiggert, J. D.; Pan, C.; Dinniman, M. S.; Lau, Y.; Fitzpatrick, P. J.; O'Brien, S. J.; Bouchard, C.; Quas, L. M.; Miles, T. N.; Cambazoglu, M. K.; Dykstra, S. L.; Dzwonkowski, B.; Jacobs, G. A.; Church, I.; Hofmann, E. E.

2017-12-01

A circulation model based on the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System, with coupled biogeochemical and sediment transport modules, has been implemented for Mississippi Sound and the adjacent continental shelf region. The model has 400-m horizontal resolution, 24 vertical layers, and includes wetting/drying capability to resolve shallow inshore regions. The circulation model was spun-up using oceanographic initial and lateral boundary conditions provided by a 1-km resolution regional implementation of the Navy Coastal Ocean Model (NCOM) in the Gulf of Mexico. The biogeochemical module includes multiple size classes of phytoplankton, zooplankton and detritus, a fish larvae compartment, and explicitly tracks dissolved oxygen with benthic cycling interaction. The sediment transport model is implemented based on benthic mapping data that provides bottom sediment type distributions and spatio-temporal validation. A regionally specific atmospheric forcing product that provides improved spatial and temporal resolution, including diurnal sea breeze impacts, has been developed and applied. Model experiments focus on periods when comprehensive ship-based sampling was deployed by the CONCORDE (Consortium for Coastal River-Dominated Ecosystems) research program, which was established to investigate the complex fine-scale biological, chemical and physical interactions in a marine system controlled by pulsed-river plume dynamics. Biophysical interactions and biogeochemical variability associated with estuarine - shelf exchanges between nearshore lagoonal estuarine waters and the continental shelf revealed by the model provide new insight into how seasonal variation of hydrological forcing conditions influence ecological and biogeochemical processes in the highly productive Northern Gulf region. Application of the COAWST-based model system with and without inclusion of the sediment transport module demonstrates how suspended sediment in the nearshore waters influences inner shelf ecosystem function through impacts exerted on the in situ light environment and particle aggregation-mediated organic matter fluxes.

The Impact of Detailed Snow Physics on the Simulation of Snow Cover and Subsurface Thermodynamics at Continental Scales

NASA Technical Reports Server (NTRS)

Stieglitz, Marc; Ducharne, Agnes; Koster, Randy; Suarez, Max; Busalacchi, Antonio J. (Technical Monitor)

2000-01-01

The three-layer snow model is coupled to the global catchment-based Land Surface Model (LSM) of the NASA Seasonal to Interannual Prediction Project (NSIPP) project, and the combined models are used to simulate the growth and ablation of snow cover over the North American continent for the period 1987-1988. The various snow processes included in the three-layer model, such as snow melting and re-freezing, dynamic changes in snow density, and snow insulating properties, are shown (through a comparison with the corresponding simulation using a much simpler snow model) to lead to an improved simulation of ground thermodynamics on the continental scale.

Measurements of slope currents and internal tides on the Continental Shelf and slope off Newport Beach, California

USGS Publications Warehouse

Rosenberger, Kurt J.; Noble, Marlene A.; Norris, Benjamin

2014-01-01

An array of seven moorings housing current meters and oceanographic sensors was deployed for 6 months at 5 sites on the Continental Shelf and slope off Newport Beach, California, from July 2011 to January 2012. Full water-column profiles of currents were acquired at all five sites, and a profile of water-column temperature was also acquired at two of the five sites for the duration of the deployment. In conjunction with this deployment, the Orange County Sanitation District deployed four bottom platforms with current meters on the San Pedro Shelf, and these meters provided water-column profiles of currents. The data from this program will provide the basis for an investigation of the interaction between the deep water flow over the slope and the internal tide on the Continental Shelf.

Topographic Evolution and Climate Aridification during Continental Collision: Insights from Computer Simulations

PubMed Central

2015-01-01

How do the feedbacks between tectonics, sediment transport and climate work to shape the topographic evolution of the Earth? This question has been widely addressed via numerical models constrained with thermochronological and geomorphological data at scales ranging from local to orogenic. Here we present a novel numerical model that aims at reproducing the interaction between these processes at the continental scale. For this purpose, we combine in a single computer program: 1) a thin-sheet viscous model of continental deformation; 2) a stream-power surface-transport approach; 3) flexural isostasy allowing for the formation of large sedimentary foreland basins; and 4) an orographic precipitation model that reproduces basic climatic effects such as continentality and rain shadow. We quantify the feedbacks between these processes in a synthetic scenario inspired by the India-Asia collision and the growth of the Tibetan Plateau. We identify a feedback between erosion and crustal thickening leading locally to a <50% increase in deformation rates in places where orographic precipitation is concentrated. This climatically-enhanced deformation takes place preferentially at the upwind flank of the growing plateau, specially at the corners of the indenter (syntaxes). We hypothesize that this may provide clues for better understanding the mechanisms underlying the intriguing tectonic aneurisms documented in the Himalayas. At the continental scale, however, the overall distribution of topographic basins and ranges seems insensitive to climatic factors, despite these do have important, sometimes counterintuitive effects on the amount of sediments trapped within the continent. The dry climatic conditions that naturally develop in the interior of the continent, for example, trigger large intra-continental sediment trapping at basins similar to the Tarim Basin because they determine its endorheic/exorheic drainage. These complex climatic-drainage-tectonic interactions make the development of steady-state topography at the continental scale unlikely. PMID:26244662

Topographic Evolution and Climate Aridification during Continental Collision: Insights from Computer Simulations.

PubMed

Garcia-Castellanos, Daniel; Jiménez-Munt, Ivone

2015-01-01

How do the feedbacks between tectonics, sediment transport and climate work to shape the topographic evolution of the Earth? This question has been widely addressed via numerical models constrained with thermochronological and geomorphological data at scales ranging from local to orogenic. Here we present a novel numerical model that aims at reproducing the interaction between these processes at the continental scale. For this purpose, we combine in a single computer program: 1) a thin-sheet viscous model of continental deformation; 2) a stream-power surface-transport approach; 3) flexural isostasy allowing for the formation of large sedimentary foreland basins; and 4) an orographic precipitation model that reproduces basic climatic effects such as continentality and rain shadow. We quantify the feedbacks between these processes in a synthetic scenario inspired by the India-Asia collision and the growth of the Tibetan Plateau. We identify a feedback between erosion and crustal thickening leading locally to a <50% increase in deformation rates in places where orographic precipitation is concentrated. This climatically-enhanced deformation takes place preferentially at the upwind flank of the growing plateau, specially at the corners of the indenter (syntaxes). We hypothesize that this may provide clues for better understanding the mechanisms underlying the intriguing tectonic aneurisms documented in the Himalayas. At the continental scale, however, the overall distribution of topographic basins and ranges seems insensitive to climatic factors, despite these do have important, sometimes counterintuitive effects on the amount of sediments trapped within the continent. The dry climatic conditions that naturally develop in the interior of the continent, for example, trigger large intra-continental sediment trapping at basins similar to the Tarim Basin because they determine its endorheic/exorheic drainage. These complex climatic-drainage-tectonic interactions make the development of steady-state topography at the continental scale unlikely.

Potential geologic hazards and constraints for blocks in proposed North Atlantic OCS Oil and gas lease sale 52

USGS Publications Warehouse

Carpenter, G.B.; Cardinell, A.P.; Francois, D.K.; Good, L.K.; Lewis, R.L.; Stiles, N.T.

1982-01-01

Analysis of high-resolution geophysical data collected over 540 blocks tentatively selected for leasing in proposed OCS Oil and Gas Lease Sale 52 (Georges Bank) revealed a number of potential geologic hazards to oil and gas exploration and development activities: evidence of mass movements and shallow gas deposits on the continental slope. No potential hazards were observed on the continental shelf or rise. Other geology-related problems, termed constraints because they pose a relatively low degree of risk and can be routinely dealt with by the use of existing technology have been observed on the continental shelf. Constraints identified in the proposed sale area are erosion, sand waves, filled channels and deep faults. Piston cores were collected for geotechnical analysis at selected locations on the continental slope in the proposed lease sale area. The core locations were selected to provide information on slope stability and to establish the general geotechnical properties of the sediments. Preliminary results of a testing program suggest that the surficial sediment cover is stable with respect to mass movement.

Publications - GMC 252 | Alaska Division of Geological & Geophysical

Science.gov Websites

DGGS GMC 252 Publication Details Title: Kemik sandstone - petrology, physical properties, and facies of Continental Margins Program, 1995, Kemik sandstone - petrology, physical properties, and facies of outcrop

Microphytobenthos production potential and contribution to bottom layer oxygen dynamics on the inner Louisiana continental shelf

EPA Science Inventory

To investigate the relative importance of microphytobenthos (MPB) oxygen (O2) production on a river-dominated shelf, we made sediment core incubation measurements of MPB O2 production and sediment O2 consumption, and compared these to water-column measures of primary production ...

Carbon dynamics and sequestration in urban turfgrass ecosystems

USDA-ARS?s Scientific Manuscript database

Urbanization is a global trend. Turfgrass covers 1.9% of land in the continental US. Here we review existing literature associated with carbon (C) pools, sequestration, and nitrous oxide emission of urban turfgrass ecosystems. Turfgrasses exhibit significant carbon sequestration (0.34–1.4 Mg ha-1 ye...

Interactions between Freshwater Input, Light, and Phytoplankton Dynamics on the Louisiana Continental Shelf.

EPA Science Inventory

Light attenuation (kd), chlorophyll a (chl a), and primary production (PP) were measured across the Louisiana shelf, encompassing the area of the shelf where summer hypoxia forms, on 7 spring/summer cruises from 2005 to 2007. Shelf-wide average kd (1/m) co-varied with Mississipp...

Incorporating Cutting Edge Scientific Results from the Margins-Geoprisms Program into the Undergraduate Curriculum, Rupturing Continental Lithosphere Part I: Introducing Seismic Interpretation and Isostasy Principles Using Gulf of California Examples

NASA Astrophysics Data System (ADS)

Lamb, M. A.; Cashman, S. M.; Dorsey, R. J.; Bennett, S. E. K.; Loveless, J. P.; Goodliffe, A. M.

2014-12-01

The NSF-MARGINS Program funded a decade of research on continental margin processes. The NSF-GeoPRISMS Mini-lesson Project, funded by NSF-TUES, is designed to integrate the significant findings from the MARGINS program into open-source college-level curriculum. The Gulf of California (GOC) served as the focus site for the Rupturing Continental Lithosphere initiative, which addressed several scientific questions: What forces drive rift initiation, localization, propagation and evolution? How does deformation vary in time and space, and why? How does crust evolve, physically and chemically, as rifting proceeds to sea-floor spreading? What is the role of sedimentation and magmatism in continental extension? We developed two weeks of curriculum designed for an upper-division structural geology, tectonics or geophysics course. The curriculum includes lectures, labs, and in-class activities that can be used as a whole or individually. The first set of materials introduces the RCL initiative to students and has them analyze the bathymetry and oblique-rifting geometry of the GOC in an exercise using GeoMapApp. The second set of materials has two goals: (1) introduce students to fundamental concepts of interpreting seismic reflection data via lectures and in-class interpretation of strata, basement, and faults from recent GOC seismic data, and (2) encourage students to discover the structural geometry and rift evolution, including the east-to-west progression of faulting and transition from detachment to high-angle faulting in the northern GOC, and changes in deformation style from north to south. In the third set of materials, students investigate isostatic affects of sediment fill in GOC oblique rift basins. This activity consists of a problem set, introduced in a lecture, where students integrate their findings from the previous bathymetry- and seismic-interpretation exercises.

History of Concurrency. The Controversy of Military Acquisition Program Schedule Compression

DTIC Science & Technology

1986-09-01

33 The Manhattan Project . ........... 35 Post-War Acquisition . . . . ...... 40 The Lockheed Skunk Works ........ 42 iii Era of Controversy...been involved Vin the Manhattan Project (47:55). The concurrency concept and the innovative foundation of the Air Force Ballistic Missile Program...inter- F4 continental oallistic missile. To snorten the program’s development time they drew upon lessons from the Manhattan Project and made three

Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean

PubMed Central

Kendall, Brian; Creaser, Robert A.; Reinhard, Christopher T.; Lyons, Timothy W.; Anbar, Ariel D.

2015-01-01

It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event. A depositional age of 2495 ± 14 million years and an initial 187Os/188Os of 0.34 ± 0.19 were obtained for rhenium- and molybdenum-rich black shales. The initial 187Os/188Os is higher than the mantle/extraterrestrial value of 0.11, pointing to mild environmental oxygenation and oxidative mobilization of rhenium, molybdenum, and radiogenic osmium from the upper continental crust and to contemporaneous transport of these metals to seawater. By contrast, stratigraphically overlying black shales are rhenium- and molybdenum-poor and have a mantle-like initial 187Os/188Os of 0.06 ± 0.09, indicating a reduced continental flux of rhenium, molybdenum, and osmium to seawater because of a drop in environmental O2 levels. Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean. PMID:26702438

Trophic Ecology and Movement Patters of Tiger Sharks (Galeocerdo Cuvier) off the Western North Atlantic Coastal and Continental Shelf Waters

NASA Astrophysics Data System (ADS)

Sancho, G.; Edman, R.; Frazier, B.; Bubley, W.

2016-02-01

Understanding the trophic dynamics and habitat utilization of apex predators is central to inferring their influence on different marine landscapes and to help design effective management plans for these animals. Tiger sharks (Galeocerdo cuvier) are abundant in shelf and offshore Gulf Stream waters of the western North Atlantic Ocean, and based on movements from individuals captured in Florida and Bahamas, seem to avoid coastal and shelf waters off South Carolina and Georgia. This contradicts reports of tiger sharks regularly being caught nearshore by anglers in these states, indicating that separate sub-populations may exist in the western North Atlantic. In the present study we captured Tiger Sharks in coastal waters off South Carolina in 2014 and 2015 in order to describe their movement patterns through acoustic and satellite tagging, and trophic dynamics through stable isotope analyses. Movement data show that these tiger sharks repeatedly visit particular inshore areas and mainly travel over the continental shelf, but rarely venture offshore beyond the continental shelf edge. Ongoing C and N stable isotope analyses of muscle, blood and skin tissues from adult and juvenile tiger sharks, as well as from potential prey species and primary producers, will help determine if their diets are based on inshore, shelf or offshore based food webs. Tiger sharks exploiting nearshore environments and shelf waters have much higher probabilities of interacting with humans than individuals occupying far offshore Gulf Stream habitats.

Data file, Continental Margin Program, Atlantic Coast of the United States: vol. 2 sample collection and analytical data

USGS Publications Warehouse

Hathaway, John C.

1971-01-01

The purpose of the data file presented below is twofold: the first purpose is to make available in printed form the basic data relating to the samples collected as part of the joint U.S. Geological Survey - Woods Hole Oceanographic Institution program of study of the Atlantic continental margin of the United States; the second purpose is to maintain these data in a form that is easily retrievable by modern computer methods. With the data in such form, repeate manual transcription for statistical or similar mathematical treatment becomes unnecessary. Manual plotting of information or derivatives from the information may also be eliminated. Not only is handling of data by the computer considerably faster than manual techniques, but a fruitful source of errors, transcription mistakes, is eliminated.

Financial Management Regulation. Volume 13. Nonappropriated Funds Policy and Procedures.

DTIC Science & Technology

1994-08-22

located in the continental United States, Alaska, territory made pursuant to the Act of 17 July and Hawaii are subject to the following 1952 (66 Stat...17 0404 D ISCO U N TS ....................................................... 17 0405 PROMPT PAYMENT ACT ...PROGRAM ............................. B-10 B0410 RANDOLPH SHEPPARD ACT -VENDING FACILITY PROGRAM FOR THE BL IN D

30 CFR 250.456 - What safe practices must the drilling fluid program follow?

Code of Federal Regulations, 2010 CFR

2010-07-01

... INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Drilling Fluid Requirements § 250.456 What safe practices must the drilling fluid program follow... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What safe practices must the drilling fluid...

Land Use Induced Hydroclimatic Variability Over Large Deforested Areas in Southern Amazon Rainforest

NASA Astrophysics Data System (ADS)

Khanna, J.; Medvigy, D.

2017-12-01

Contemporary Amazonian deforestation, which occurs at scales of a few hundreds of kilometers, has been found to induce systematic changes in the regional dry season precipitation. The replacement of rough forest with smooth pasture induces a low level atmospheric convergence and uplift in the downwind and divergence and subsidence in the upwind deforested areas. The resulting precipitation change is about ±30% of the deforested area mean in the two regions respectively. Compared with the increase in non-precipitating cloudiness triggered by small scale clearings prevalent in the early phases of deforestation, this `dynamical mesoscale circulation' can have regional ecological impacts by altering precipitation seasonality and in turn ecosystem dynamics. However, the seasonality and variability of this phenomenon hasn't been studied. Using observations and numerical simulations this study investigates the relationships between the dynamical mechanism and the local- and continental-scale atmospheric conditions to understand the physical controls on this phenomenon on the inter-annual, inter-seasonal and daily time scales. We find that the strength of the dynamical mechanism is controlled mostly by regional scale thermal and dynamical conditions of the boundary layer and not the continental and global scale atmospheric state. The lifting condensation level (thermodynamic control) and wind speed (dynamic control) within the boundary layer have the largest and positive correlations with the dipole strength, which is true although not always significant across time scales. Due to this dependence it is found to be strongest during parts of the year when the atmosphere is relatively stable. Hence, overall this phenomenon is found to be the prevalent convective triggering mechanism during the dry and parts of transition seasons (especially spring), significantly affecting the hydroclimate during this period.

Comparison between remote sensing and a dynamic vegetation model for estimating terrestrial primary production of Africa.

PubMed

Ardö, Jonas

2015-12-01

Africa is an important part of the global carbon cycle. It is also a continent facing potential problems due to increasing resource demand in combination with climate change-induced changes in resource supply. Quantifying the pools and fluxes constituting the terrestrial African carbon cycle is a challenge, because of uncertainties in meteorological driver data, lack of validation data, and potentially uncertain representation of important processes in major ecosystems. In this paper, terrestrial primary production estimates derived from remote sensing and a dynamic vegetation model are compared and quantified for major African land cover types. Continental gross primary production estimates derived from remote sensing were higher than corresponding estimates derived from a dynamic vegetation model. However, estimates of continental net primary production from remote sensing were lower than corresponding estimates from the dynamic vegetation model. Variation was found among land cover classes, and the largest differences in gross primary production were found in the evergreen broadleaf forest. Average carbon use efficiency (NPP/GPP) was 0.58 for the vegetation model and 0.46 for the remote sensing method. Validation versus in situ data of aboveground net primary production revealed significant positive relationships for both methods. A combination of the remote sensing method with the dynamic vegetation model did not strongly affect this relationship. Observed significant differences in estimated vegetation productivity may have several causes, including model design and temperature sensitivity. Differences in carbon use efficiency reflect underlying model assumptions. Integrating the realistic process representation of dynamic vegetation models with the high resolution observational strength of remote sensing may support realistic estimation of components of the carbon cycle and enhance resource monitoring, providing suitable validation data is available.

The Importance of Planetary Rotation Period for Ocean Heat Transport

PubMed Central

Stevens, D.; Joshi, M.

2014-01-01

Abstract The climate and, hence, potential habitability of a planet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions. However, previous studies of planetary climate have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans, which neglects or misrepresents the effect of the ocean in the total heat transport. Even the majority of studies with a dynamic ocean have used a simple so-called aquaplanet that has no continental barriers, which is a configuration that dramatically changes the ocean dynamics. Here, the significance of the response of poleward ocean heat transport to planetary rotation period is shown with a simple meridional barrier—the simplest representation of any continental configuration. The poleward ocean heat transport increases significantly as the planetary rotation period is increased. The peak heat transport more than doubles when the rotation period is increased by a factor of ten. There are also significant changes to ocean temperature at depth, with implications for the carbon cycle. There is strong agreement between the model results and a scale analysis of the governing equations. This result highlights the importance of both planetary rotation period and the ocean circulation when considering planetary habitability. Key Words: Exoplanet—Oceans—Rotation—Climate—Habitability. Astrobiology 14, 645–650. PMID:25041658

Toward a comprehensive landscape vegetation monitoring framework

NASA Astrophysics Data System (ADS)

Kennedy, Robert; Hughes, Joseph; Neeti, Neeti; Larrue, Tara; Gregory, Matthew; Roberts, Heather; Ohmann, Janet; Kane, Van; Kane, Jonathan; Hooper, Sam; Nelson, Peder; Cohen, Warren; Yang, Zhiqiang

2016-04-01

Blossoming Earth observation resources provide great opportunity to better understand land vegetation dynamics, but also require new techniques and frameworks to exploit their potential. Here, I describe several parallel projects that leverage time-series Landsat imagery to describe vegetation dynamics at regional and continental scales. At the core of these projects are the LandTrendr algorithms, which distill time-series earth observation data into periods of consistent long or short-duration dynamics. In one approach, we built an integrated, empirical framework to blend these algorithmically-processed time-series data with field data and lidar data to ascribe yearly change in forest biomass across the US states of Washington, Oregon, and California. In a separate project, we expanded from forest-only monitoring to full landscape land cover monitoring over the same regional scale, including both categorical class labels and continuous-field estimates. In these and other projects, we apply machine-learning approaches to ascribe all changes in vegetation to driving processes such as harvest, fire, urbanization, etc., allowing full description of both disturbance and recovery processes and drivers. Finally, we are moving toward extension of these same techniques to continental and eventually global scales using Google Earth Engine. Taken together, these approaches provide one framework for describing and understanding processes of change in vegetation communities at broad scales.

Computer simulations of large asteroid impacts into oceanic and continental sites--preliminary results on atmospheric, cratering and ejecta dynamics

USGS Publications Warehouse

Roddy, D.J.; Schuster, S.H.; Rosenblatt, M.; Grant, L.B.; Hassig, P.J.; Kreyenhagen, K.N.

1987-01-01

Computer simulations have been completed that describe passage of a 10-km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics caused by impact of the asteroid into both oceanic and continental sites. The asteroid was modeled as a spherical body moving vertically at 20 km/s with a kinetic energy of 2.6 ?? 1030 ergs (6.2 ?? 107 Mt ). Detailed material modeling of the asteroid, ocean, crustal units, sedimentary unit, and mantle included effects of strength and fracturing, generic asteroid and rock properties, porosity, saturation, lithostatic stresses, and geothermal contributions, each selected to simulate impact and geologic conditions that were as realistic as possible. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock wave followed by a highly shock compressed and heated air mass. Rapid expansion of this shocked air created a large low-density region that also expanded away from the impact area. Shock temperatures in air reached ???20,000 K near the surface of the uplifting crater rim and were as high as ???2000 K at more than 30 km range and 10 km altitude. Calculations to 30 s showed that the shock fronts in the air and in most of the expanding shocked air mass preceded the formation of the crater, ejecta, and rim uplift and did not interact with them. As cratering developed, uplifted rim and target material were ejected into the very low density, shock-heated air immediately above the forming crater, and complex interactions could be expected. Calculations of the impact events showed equally dramatic effects on the oceanic and continental targets through an interval of 120 s. Despite geologic differences in the targets, both cratering events developed comparable dynamic flow fields and by ???29 s had formed similar-sized transient craters ???39 km deep and ???62 km across. Transient-rim uplift of ocean and crust reached a maximum altitude of nearly 40 km at ???30 s and began to decay at velocities of 500 m/s to develop large-tsunami conditions. After ???30 s, strong gravitational rebound drove both craters toward broad flat-floored shapes. At 120 s, transient crater diameters were ???80 km (continental) and ???105 km (oceanic) and transient depths were ???27 km; crater floors consisting of melted and fragmented hot rock were rebounding rapidly upward. By 60 s, the continental crater had ejected ???2 ?? 1014 t, about twice the mass ejected from the oceanic crater. By 120 s, ???70,000 km3 (continental) and ???90,000 km3 (oceanic) target material were excavated (no mantle) and massive ejecta blankets were formed around the craters. We estimate that in excess of ???70% of the ejecta would finally lie within ???3 crater diameters of the impact, and the remaining ejecta (???1013 t), including the vaporized asteroid, would be ejected into the atmosphere to altitudes as high as the ionosphere. Effects of secondary volcanism and return of the ocean over hot oceanic crater floor could also be expected to contribute substantial material to the atmosphere. ?? 1987.

Crustal growth in subduction zones

NASA Astrophysics Data System (ADS)

Vogt, Katharina; Castro, Antonio; Gerya, Taras

2015-04-01

There is a broad interest in understanding the physical principles leading to arc magmatisim at active continental margins and different mechanisms have been proposed to account for the composition and evolution of the continental crust. It is widely accepted that water released from the subducting plate lowers the melting temperature of the overlying mantle allowing for "flux melting" of the hydrated mantle. However, relamination of subducted crustal material to the base of the continental crust has been recently suggested to account for the growth and composition of the continental crust. We use petrological-thermo-mechanical models of active subduction zones to demonstrate that subduction of crustal material to sublithospheric depth may result in the formation of a tectonic rock mélange composed of basalt, sediment and hydrated /serpentinized mantle. This rock mélange may evolve into a partially molten diapir at asthenospheric depth and rise through the mantle because of its intrinsic buoyancy prior to emplacement at crustal levels (relamination). This process can be episodic and long-lived, forming successive diapirs that represent multiple magma pulses. Recent laboratory experiments of Castro et al. (2013) have demonstrated that reactions between these crustal components (i.e. basalt and sediment) produce andesitic melt typical for rocks of the continental crust. However, melt derived from a composite diapir will inherit the geochemical characteristics of its source and show distinct temporal variations of radiogenic isotopes based on the proportions of basalt and sediment in the source (Vogt et al., 2013). Hence, partial melting of a composite diapir is expected to produce melt with a constant major element composition, but substantial changes in terms of radiogenic isotopes. However, crustal growth at active continental margins may also involve accretionary processes by which new material is added to the continental crust. Oceanic plateaus and other crustal units may collide with continental margins to form collisional orogens and accreted terranes in places where oceanic lithosphere is recycled back into the mantle. We use thermomechanical-petrological models of an oceanic-continental subduction zone to analyse the dynamics of terrane accretion and its implications to arc magmatisim. It is shown that terrane accretion may result in the rapid growth of continental crust, which is in accordance with geological data on some major segments of the continental crust. Direct consequences of terrane accretion may include slab break off, subduction zone transference, structural reworking, formation of high-pressure terranes and partial melting (Vogt and Gerya., 2014), forming complex suture zones of accreted and partially molten units. Castro, A., Vogt, K., Gerya, T., 2013. Generation of new continental crust by sublithospheric silicic-magma relamination in arcs: A test of Taylor's andesite model. Gondwana Research, 23, 1554-1566. Vogt, K., Castro, A., Gerya, T., 2013. Numerical modeling of geochemical variations caused by crustal relamination. Geochemistry, Geophysics, Geosystems, 14, 470-487. Vogt, K., Gerya, T., 2014. From oceanic plateaus to allochthonous terranes: Numerical Modelling. Gondwana Research, 25, 494-508

An Overview of the NASA Energy and Water cycle Study (NEWS) and the North American Water Program (NAWP)

NASA Astrophysics Data System (ADS)

Houser, P. R.

2014-12-01

NEWS: 10 years ago, NASA established the NASA Energy and Water-cycle Study (NEWS), whose long-term grand challenge is to document and enable improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. The NEWS program builds upon existing NASA-supported basic research in atmospheric physics and dynamics, radiation, climate modeling, and terrestrial hydrology. While these NASA programs fund research activities that address individual aspects of the global energy and water cycles, they are not specifically designed to generate a coordinated result. NEWS developed the first coordinated attempt to describe the complete global energy and water cycle using existing and forthcoming satellite and ground based observations, and laying the foundation for essential NEWS developments in model representations of atmospheric energy and water exchange processes. This comprehensive energy and water data analysis program exploited crucial datasets, some requiring complete re-processing, and new satellite measurements. NAWP: Dramatically changing climates has had an indelible impact on North America's water crisis. To decisively address these challenges, we recommend that NAWP coalesce an interdisciplinary, international and interagency effort to make significant contributions to continental- to decision-scale hydroclimate science and solutions. By entraining, integrating and coordinating the vast array of interdisciplinary observational and prediction resources available, NAWP will significantly advance skill in predicting, assessing and managing variability and changes in North American water resources. We adopt three challenges to organize NAWP efforts. The first deals with developing a scientific basis and tools for mitigating and adapting to changes in the water supply-demand balance. The second challenge is benchmarking; to use incomplete and uncertain observations to assess water storage and quality dynamics, and to characterize the information content of water cycle predictions in a way that allows for model improvement. The final challenge is to establish clear pathways to inform water managers, practitioners and decision makers about newly developed tools, observations and research results.

Ocean processes at the Antarctic continental slope

PubMed Central

Heywood, Karen J.; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D.; Queste, Bastien Y.; Stevens, David P.; Wadley, Martin; Thompson, Andrew F.; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K.; Smith, Walker

2014-01-01

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean–atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

Ocean processes at the Antarctic continental slope.

PubMed

Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

2014-07-13

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

Remote Versus Local Forcing of Chlorophyll Variability in the South Atlantic Bight

NASA Technical Reports Server (NTRS)

Signorini, Sergio R.; McClain, Charles R.

2006-01-01

This TM documents results of analyses addressing the local versus remote forcing of chlorophyll variability on the shelf and slope regions of the South Atlantic Bight (SAB) based on satellite-derived products and a limited amount of in situ data. This study is part of a larger multi-disciplinary, multi-institutional effort to study the Eastern U.S. Continental Shelf carbon budget (U.S. Eastern Continental Shelf Carbon Budget: Modeling, Data Assimilation, and Analysis, U.S. ECoS), a project funded by the NASA Earth System Enterprise Interdisciplinary Science Program that started in the summer of 2004.

Hydrodynamic Environment and Ecosystem Diversity at two Deep-Sea Marine Protected Areas in Southern Biscay

NASA Astrophysics Data System (ADS)

González-Pola, C.; Ivey, G. N.; Jones, N. L.; Sanchez, F.; Kelly, S. M.; Bluteau, C.; Somavilla, R.

2016-02-01

Two nearby offshore deep sea areas in Southern Bay of Biscay (northern Spain), hosting valuable ecosystems, have been recently declared marine protected areas. The first one is Le Danois Bank, a seamount-like feature connected to the continental shelf by a saddle. The second one is the Aviles Canyon System (ACS) that breaks the continuity of the northern Spanish continental shelf. A number of observational multidisciplinary programs carried out within the last decade allowed a detailed identification of habitats and biological communities. As a long-term goal these programs aimed to understand the ecosystem functioning as a whole with the implicit focus in associated circulation and dynamics. The observational record includes deep sea photogrametry as well as standard hydrography and long-term mooring lines. A lander system provided high-frequency currents and thermal structure tens meters above bottom together with time lapse photographs at selected sites. Different characteristic habitats from sedimentary to rocky, associated with different fisheries, were described both in Le Danois Bank and the ACS. These include sponge aggregations and deep water corals. Noteworthy structured coral reefs only appeared in a relatively small area in one of the tributaries of the ACS (La Gaviera Canyon), where local near-bottom currents were stronger than anywhere else in the region. The development and violent breaking of an internal tidal bore was the main feature of such hotspot. Analytic estimates confirmed that La Gaviera is the only canyon were large patches of the seafloor are critical or near-critical to the semidiurnal internal tide and nearby upper flanks show also large patches of critical seafloor and large body forcing. A year-long near-bottom current record captured the development of three benthic storms, events lasting several days in which currents increases up to 3-fold the tidal max speeds and direction swings rapidly, losing the uniformity of tidal regime.

Ocean Circulation and Dynamics on the West Antarctic Peninsula Continental Shelf

DTIC Science & Technology

2007-09-01

Physical Oceanography, and Wolfgang Schneider, Renato Quifiones, Silvio Pantoja, Samuel Hormaz6bal and Oscar Pizarro all helped me learn more about how to be...Rohardt, G., Krause , G., 1992. The Antarctic coastal current in the southeastern Weddell Sea. Polar Biology 12 (2), 171-182. 178 Flagg, C. N

Influence of Boundary Conditions on Regional Air Quality Simulations-Analysis of AQMEII Phase 3 Results

EPA Science Inventory

This presentation focuses on the dynamic evaluation of the CMAQ model over the continental United States using multi-decadal simulations for the period from 1990 to 2010 to examine how well the changes in observed ozone air quality induced by variations in meteorology and/or emis...

Variation in germination capacity and seedling growth of water primroses in contrasting climates from two invaded continental ranges

USDA-ARS?s Scientific Manuscript database

Aquatic ecosystems are vulnerable to biological invasions, and will also be strongly impacted by climate change. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity. Many aquatic invasive plants rely on clonal reprod...

Assessing the Role of Seafloor Weathering in Global Geochemical Cycling

NASA Astrophysics Data System (ADS)

Farahat, N. X.; Abbot, D. S.; Archer, D. E.

2015-12-01

Low-temperature alteration of the basaltic upper oceanic crust, known as seafloor weathering, has been proposed as a mechanism for long-term climate regulation similar to the continental climate-weathering negative feedback. Despite this potentially far-reaching impact of seafloor weathering on habitable planet evolution, existing modeling frameworks do not include the full scope of alteration reactions or recent findings of convective flow dynamics. We present a coupled fluid dynamic and geochemical numerical model of low-temperature, off-axis hydrothermal activity. This model is designed to explore the the seafloor weathering flux of carbon to the oceanic crust and its responsiveness to climate fluctuations. The model's ability to reproduce the seafloor weathering environment is evaluated by constructing numerical simulations for comparison with two low-temperature hydrothermal systems: A transect east of the Juan de Fuca Ridge and the southern Costa Rica Rift flank. We explore the sensitivity of carbon uptake by seafloor weathering on climate and geology by varying deep ocean temperature, seawater dissolved inorganic carbon, continental weathering inputs, and basaltic host rock in a suite of numerical experiments.

Free oscillations in a climate model with ice-sheet dynamics

NASA Technical Reports Server (NTRS)

Kallen, E.; Crafoord, C.; Ghil, M.

1979-01-01

A study of stable periodic solutions to a simple nonlinear model of the ocean-atmosphere-ice system is presented. The model has two dependent variables: ocean-atmosphere temperature and latitudinal extent of the ice cover. No explicit dependence on latitude is considered in the model. Hence all variables depend only on time and the model consists of a coupled set of nonlinear ordinary differential equations. The globally averaged ocean-atmosphere temperature in the model is governed by the radiation balance. The reflectivity to incoming solar radiation, i.e., the planetary albedo, includes separate contributions from sea ice and from continental ice sheets. The major physical mechanisms active in the model are (1) albedo-temperature feedback, (2) continental ice-sheet dynamics and (3) precipitation-rate variations. The model has three-equilibrium solutions, two of which are linearly unstable, while one is linearly stable. For some choices of parameters, the stability picture changes and sustained, finite-amplitude oscillations obtain around the previously stable equilibrium solution. The physical interpretation of these oscillations points to the possibility of internal mechanisms playing a role in glaciation cycles.

Surficial sediments along the inner Continental shelf of Maine

USGS Publications Warehouse

Kelley, J.T.; Dickson, S.M.

1999-01-01

Through 10 years of support from the Minerals Management Service-Association of American State Geologists' Continental Margins Program we have mapped along the Maine coast, seaward to the 100 m isobath. In all, 1,773 bottom sample stations were occupied, 3,358 km of side-scan sonar and 5,011 km of seismic reflection profiles were gathered. On the basis of these data, a surficial sediment map was created for the Maine inner continental shelf during the Year 8 project, and cores and seismic data were collected to evaluate sand thickness during Years 9 and 10. Sand covers only 8% of the Maine shelf, and is concentrated seaward of beaches off southern Maine in water depths less than 60 m. Sand occurs in three depositional settings: (1) in shoreface deposits connected dynamically to contemporary beaches; (2) in submerged deltas associated with lower sea-level positions; and (3) in submerged lowstand shoreline positions between 50 and 60 m. Seismic profiles over the shoreface off Saco Bay, Wells Embayment, and off the Kennebec River mouth each imaged a wedge-shaped acoustic unit which tapered off between 20 and 30 m. Cores determined that this was sand that was underlain by a variable but thin (commonly < 1 m) deposit of estuarine muddy sand and a thick deposit of glacial-marine mud. Off Saco Bay, more than 55 million m3 of sand exists in the shoreface, compared with about 22 million m3 on the adjacent beach and dunes. Seaward of the Kennebec River, a large delta deposited between 13 ka and the present time holds more than 300 million m3 of sand and gravel. The best sorted sand is on the surface nearshore, with increasing amounts of gravel offshore and mud beneath the surficial sand sheet. Bedforms indicate that the surficial sand is moved by waves to at least 55 m depth. Seaward of the Penobscot River, no significant sand or gravel was encountered. Muddy estuarine sediments overlie muddy glacial-marine sediment throughout the area offshore area of this river. No satifactory explanation is offered for lack of a sandy delta seaward of Maine's largest river. Lowstand-shoreline deposits were cored in many places in Saco Bay and off the Kennebec River mouth. Datable materials from cores indicated that the lowstand occurred around 10.5 ka off the Kennebec. Cores did not penetrate glacial-marine sediment in the lowstand deposits, and seismic profiles were ambiguous about the vertical extent of sand in these units. For these reasons, no total thickness of sand was determined from the lowstand deposits, but given the area of the surficial sand, the volume is probably in the hundreds of millions of cubic meters.Through 10 years of support from the Minerals Management Service, the Association of American State Geologists' Continental Margins Program have mapped along the Maine coast, seaward to the 100 m isobath. In all, 1,773 bottom samples stations were occupied, 3,358 km of side-scan sonar and 5,011 km of seismic reflection profiles were gathered. On the basis of these data, a surficial sediment map was created for the Maine inner continental shelf during the year 8 project, and cores and seismic data were collected to evaluate sand thickness during year 9 and year 10.

Heat Content and Ice Draft Variability over the Slope of the Chukchi Sea from 2016-2017 Ocean Moorings

NASA Astrophysics Data System (ADS)

Muenchow, A.; Ryan, P. A.; Badiey, M.; Elmer, C.; Eickmeier, J.

2017-12-01

The shallow-water component of the Canada Basin Acoustic Propagation Experiment (CANAPE) will quantify how ocean properties vary at daily to seasonal time scales over the outer continental shelf of the Chukchi Sea. We here describe initial results related to a weak sound channel above warm Atlantic and below seasonally modulated surface waters. It coincides with the cold halocline layer that often slopes up- or downward at the edge of the continental shelf in response to surface forcing. Sloping topography supports isopycnal oscillations whose time scales vary from hours to months. These Kelvin or Rossby waves will become more pronounced in a increasingly dynamic, wind-forced Arctic Ocean with a diminished, thinner, and more mobile ice cover.

Project BudBurst: Continental-scale citizen science for all seasons

NASA Astrophysics Data System (ADS)

Henderson, S.; Newman, S. J.; Ward, D.; Havens-Young, K.; Alaback, P.; Meymaris, K.

2011-12-01

Project BudBurst's (budburst.org) recent move to the National Ecological Observatory Network (NEON) has benefitted both programs. NEON has been able to use Project BudBurst as a testbed to learn best practices, network with experts in the field, and prototype potential tools for engaging people in continental-scale ecology as NEON develops its citizen science program. Participation in Project BudBurst has grown significantly since the move to NEON. Project BudBurst is a national citizen science initiative designed to engage the public in observations of phenological (plant life cycle) events that raise awareness of climate change, and create a cadre of informed citizen scientists. Citizen science programs such as Project BudBurst provide the opportunity for students and interested laypersons to actively participate in scientific research. Such programs are important not only from an educational perspective, but because they also enable scientists to broaden the geographic and temporal scale of their observations. The goals of Project BudBurst are to 1) increase awareness of phenology as an area of scientific study; 2) Increase awareness of the impacts of changing climates on plants at a continental-scale; and 3) increase science literacy by engaging participants in the scientific process. From its 2008 launch in February, this on-line educational and data-entry program, engaged participants of all ages and walks of life in recording the timing of the leafing and flowering of wild and cultivated species found across the continent. Thus far, thousands of participants from all 50 states have submitted data. This presentation will provide an overview of Project BudBurst and will report on the results of the 2010 field campaign and discuss plans to expand Project BudBurst in 2012 including the use of mobile phones applications for data collection and reporting from the field. Project BudBurst is co-managed by the National Ecological Observatory Network and the Chicago Botanic Garden.

Regional assessment of sediment contamination from marshes to the continental shelf: Results of the western component of the US EPA National Coastal Assessment

EPA Science Inventory

The US EPA National Coastal Assessment (NCA) program on the U.S. West Coast was designed as a pilot project to explore assessment of new components of coastal resources not previously incorporated in the NCA. The Western Regional component of the NCA program began with a two yea...

46 CFR Sec. 7 - Operation under current GAA/MSTS Southeast Asia Program.

Code of Federal Regulations, 2013 CFR

2013-10-01

... provisions of NSA Order 35 (OPR-2) to the particular circumstances of the present GAA/MSTS Southeast Asia... General Agency operations not related to the current GAA/MSTS Southeast Asia Program, NSA Order 35 (OPR-2... lieu of those appearing in sections 3 and 4 of NSA Order 35 (OPR-2). Continental United States ports do...

46 CFR Sec. 7 - Operation under current GAA/MSTS Southeast Asia Program.

Code of Federal Regulations, 2012 CFR

2012-10-01

... provisions of NSA Order 35 (OPR-2) to the particular circumstances of the present GAA/MSTS Southeast Asia... General Agency operations not related to the current GAA/MSTS Southeast Asia Program, NSA Order 35 (OPR-2... lieu of those appearing in sections 3 and 4 of NSA Order 35 (OPR-2). Continental United States ports do...

46 CFR Sec. 7 - Operation under current GAA/MSTS Southeast Asia Program.

Code of Federal Regulations, 2010 CFR

2010-10-01

... provisions of NSA Order 35 (OPR-2) to the particular circumstances of the present GAA/MSTS Southeast Asia... General Agency operations not related to the current GAA/MSTS Southeast Asia Program, NSA Order 35 (OPR-2... lieu of those appearing in sections 3 and 4 of NSA Order 35 (OPR-2). Continental United States ports do...

46 CFR Sec. 7 - Operation under current GAA/MSTS Southeast Asia Program.

Code of Federal Regulations, 2014 CFR

2014-10-01

... provisions of NSA Order 35 (OPR-2) to the particular circumstances of the present GAA/MSTS Southeast Asia... General Agency operations not related to the current GAA/MSTS Southeast Asia Program, NSA Order 35 (OPR-2... lieu of those appearing in sections 3 and 4 of NSA Order 35 (OPR-2). Continental United States ports do...

46 CFR Sec. 7 - Operation under current GAA/MSTS Southeast Asia Program.

Code of Federal Regulations, 2011 CFR

2011-10-01

... provisions of NSA Order 35 (OPR-2) to the particular circumstances of the present GAA/MSTS Southeast Asia... General Agency operations not related to the current GAA/MSTS Southeast Asia Program, NSA Order 35 (OPR-2... lieu of those appearing in sections 3 and 4 of NSA Order 35 (OPR-2). Continental United States ports do...

Puerto Rico's forest inventory: adapting the forest inventory and analysis program to a Caribbean island.

Treesearch

T. J. Brandeis

2003-01-01

Rapid Changes in vegetation over short distances, high species diversity, and fragmented landscape challege the implementation of the Forest service's Forest inventory and Analysis (FIA)program on Puerto Rico. Applying the hexagonal FIA grid as used on the continental United States, the Forest service is installing a new forest sampling and monitoring framework...

Progress toward developing field protocols for a North American marsh bird monitoring program

Treesearch

Courtney J. Conway; Steven T. A. Timmermans

2005-01-01

Populations of many marsh-dependent birds appear to be declining, but we currently lack a continental program that provides estimates of population trends for most secretive marshbirds. The survey protocol outlined here is a standardized survey methodology being used on a pilot basis at National Wildlife Refuges and other protected wetland areas across North America...

FY 1986 science budget overview

NASA Astrophysics Data System (ADS)

Richman, Barbara T.; Robb, David W.

Continental lithosphere research, scientific ocean drilling, investigative surveys in the Exclusive Economic Zone, and the Mars Observer were among those programs that fared best in the federal budget proposal for fiscal year (FY) 1986 that President Ronald Reagan sent to Congress last week. However, the Sea Grant and Coastal Zone Management programs were among those that fell victim to the budget ax once again.

Supercontinents, mantle dynamics and plate tectonics: A perspective based on conceptual vs. numerical models

NASA Astrophysics Data System (ADS)

Yoshida, Masaki; Santosh, M.

2011-03-01

The periodic assembly and dispersal of supercontinents through the history of the Earth had considerable impact on mantle dynamics and surface processes. Here we synthesize some of the conceptual models on supercontinent amalgamation and disruption and combine it with recent information from numerical studies to provide a unified approach in understanding Wilson Cycle and supercontinent cycle. Plate tectonic models predict that superdownwelling along multiple subduction zones might provide an effective mechanism to pull together dispersed continental fragments into a closely packed assembly. The recycled subducted material that accumulates at the mantle transition zone and sinks down into the core-mantle boundary (CMB) provides the potential fuel for the generation of plumes and superplumes which ultimately fragment the supercontinent. Geological evidence related to the disruption of two major supercontinents (Columbia and Gondwana) attest to the involvement of plumes. The re-assembly of dispersed continental fragments after the breakup of a supercontinent occurs through complex processes involving 'introversion', 'extroversion' or a combination of both, with the closure of the intervening ocean occurring through Pacific-type or Atlantic-type processes. The timescales of the assembly and dispersion of supercontinents have varied through the Earth history, and appear to be closely linked with the processes and duration of superplume genesis. The widely held view that the volume of continental crust has increased over time has been challenged in recent works and current models propose that plate tectonics creates and destroys Earth's continental crust with more crust being destroyed than created. The creation-destruction balance changes over a supercontinent cycle, with a higher crustal growth through magmatic influx during supercontinent break-up as compared to the tectonic erosion and sediment-trapped subduction in convergent margins associated with supercontinent assembly which erodes the continental crust. Ongoing subduction erosion also occurs at the leading edges of dispersing plates, which also contributes to crustal destruction, although this is only a temporary process. The previous numerical studies of mantle convection suggested that there is a significant feedback between mantle convection and continental drift. The process of assembly of supercontinents induces a temperature increase beneath the supercontinent due to the thermal insulating effect. Such thermal insulation leads to a planetary-scale reorganization of mantle flow and results in longest-wavelength thermal heterogeneity in the mantle, i.e., degree-one convection in three-dimensional spherical geometry. The formation of degree-one convection seems to be integral to the emergence of periodic supercontinent cycles. The rifting and breakup of supercontinental assemblies may be caused by either tensional stress due to the thermal insulating effect, or large-scale partial melting resulting from the flow reorganization and consequent temperature increase beneath the supercontinent. Supercontinent breakup has also been correlated with the temperature increase due to upwelling plumes originating from the deeper lower mantle or CMB as a return flow of plate subduction occurring at supercontinental margins. The active mantle plumes from the CMB may disrupt the regularity of supercontinent cycles. Two end-member scenarios can be envisaged for the mantle convection cycle. One is that mantle convection with dispersing continental blocks has a short-wavelength structure, or close to degree-two structure as the present Earth, and when a supercontinent forms, mantle convection evolves into degree-one structure. Another is that mantle convection with dispersing continental blocks has a degree-one structure, and when a supercontinent forms, mantle convection evolves into degree-two structure. In the case of the former model, it would take longer time to form a supercontinent, because continental blocks would be trapped by different downwellings thus inhibiting collision. Although most of the numerical studies have assumed the continent/supercontinent to be rigid or nondeformable body mainly because of numerical limitations as well as a simplification of models, a more recent numerical study allows the modeling of mobile, deformable continents, including oceanic plates, and successfully reproduces continental drift similar to the processes and timescales envisaged in Wilson Cycle.

Global assessment of benthic nepheloid layers and linkage with upper ocean dynamics

NASA Astrophysics Data System (ADS)

Gardner, Wilford D.; Richardson, Mary Jo; Mishonov, Alexey V.

2018-01-01

Global maps of the maximum bottom concentration, thickness, and integrated particle mass in benthic nepheloid layers are published here to support collaborations to understand deep ocean sediment dynamics, linkage with upper ocean dynamics, and assessing the potential for scavenging of adsorption-prone elements near the deep ocean seafloor. Mapping the intensity of benthic particle concentrations from natural oceanic processes also provides a baseline that will aid in quantifying the industrial impact of current and future deep-sea mining. Benthic nepheloid layers have been mapped using 6,392 full-depth profiles made during 64 cruises using our transmissometers mounted on CTDs in multiple national/international programs including WOCE, SAVE, JGOFS, CLIVAR-Repeat Hydrography, and GO-SHIP during the last four decades. Intense benthic nepheloid layers are found in areas where eddy kinetic energy in overlying waters, mean kinetic energy 50 m above bottom (mab), and energy dissipation in the bottom boundary layer are near the highest values in the ocean. Areas of intense benthic nepheloid layers include the Western North Atlantic, Argentine Basin in the South Atlantic, parts of the Southern Ocean and areas around South Africa. Benthic nepheloid layers are weak or absent in most of the Pacific, Indian, and Atlantic basins away from continental margins. High surface eddy kinetic energy is associated with the Kuroshio Current east of Japan. Data south of the Kuroshio show weak nepheloid layers, but no transmissometer data exist beneath the Kuroshio, a deficiency that should be remedied to increase understanding of eddy dynamics in un-sampled and under-sampled oceanic areas.

MANAGING COASTAL DATA

EPA Science Inventory

To answer broad-scale questions on environmental conditions, the Environmental Monitoring and Assessment Program (EMAP) and its partners have collected estuarine and coastal data from hundreds of stations along the coasts of the continental United States. Types of data include w...

Applicability of NASA contract quality management and failure mode effect analysis procedures to the USGS Outer Continental Shelf oil and gas lease management program

NASA Technical Reports Server (NTRS)

Dyer, M. K.; Little, D. G.; Hoard, E. G.; Taylor, A. C.; Campbell, R.

1972-01-01

An approach that might be used for determining the applicability of NASA management techniques to benefit almost any type of down-to-earth enterprise is presented. A study was made to determine the following: (1) the practicality of adopting NASA contractual quality management techniques to the U.S. Geological Survey Outer Continental Shelf lease management function; (2) the applicability of failure mode effects analysis to the drilling, production, and delivery systems in use offshore; (3) the impact on industrial offshore operations and onshore management operations required to apply recommended NASA techniques; and (4) the probable changes required in laws or regulations in order to implement recommendations. Several management activities that have been applied to space programs are identified, and their institution for improved management of offshore and onshore oil and gas operations is recommended.

The Cora Lake Shear Zone: Strain Localization in an Ultramylonitic, Deep Crustal Shear Zone, Athabasca Granulite Terrain, Western Churchill Province, Canada

NASA Astrophysics Data System (ADS)

Regan, S.; Williams, M. L.; Mahan, K. H.; Orlandini, O. F.; Jercinovic, M. J.; Leslie, S. R.; Holland, M.

2012-12-01

Ultramylonitic shear zones typically involve intense strain localization, and when developed over large regions can introduce considerable heterogeneity into the crust. The Cora Lake shear zone (CLsz) displays several 10's to 100's of meters-wide zones of ultramylonite distributed throughout its full 3-5 km mylonitized width. Detailed mapping, petrography, thermobarometry, and in-situ monazite geochronology suggest that it formed during the waning phases of granulite grade metamorphism and deformation, within one of North America's largest exposures of polydeformed lower continental crust. Anastomosing zones of ultramylonite contain recrystallized grain-sizes approaching the micron scale and might appear to suggest lower temperature mylonitization. However, feldspar and even clinopyroxene are dynamically recrystallized, and quantitative thermobarometry of syn-deformational assemblages indicate high P and T conditions ranging from 0.9 -10.6 GPa and 775-850 °C. Even at these high T's, dynamic recovery and recrystallization were extremely limited. Rocks with low modal quartz have extremely small equilibrium volumes. This is likely the result of inefficient diffusion, which is further supported by the unannealed nature of the crystals. Local carbonate veins suggests that H2O poor, CO2 rich conditions may have aided in the preservation of fine grain sizes, and may have inhibited dynamic recovery and recrystallization. The Cora Lake shear zone is interpreted to have been relatively strong and to have hardened during progressive deformation. Garnet is commonly fractured perpendicular to host rock fabric, and statically replaced by both biotite and muscovite. Pseudotachylite, with the same sense of shear, occurs in several ultramylonitized mafic granulites. Thus, cataclasis and frictional melt are interpreted to have been produced in the lower continental crust, not during later reactivation. We suggest that strengthening of rheologically stiffer lithologies led to extreme localization, and potentially earthquakes in quartz-absent hardened lithologies. Cora Lake shearing represents the culmination of a deformation trend of increasing strength, strain partitioning, and localization within a polydeformed, strengthened lower continental crust.

Near-real-time mosaics from high-resolution side-scan sonar

USGS Publications Warehouse

Danforth, William W.; O'Brien, Thomas F.; Schwab, W.C.

1991-01-01

High-resolution side-scan sonar has proven to be a very effective tool for stuyding and understanding the surficial geology of the seafloor. Since the mid-1970s, the US Geological Survey has used high-resolution side-scan sonar systems for mapping various areas of the continental shelf. However, two problems typically encountered included the short range and the high sampling rate of high-resolution side-scan sonar systems and the acquisition and real-time processing of the enormous volume of sonar data generated by high-resolution suystems. These problems were addressed and overcome in August 1989 when the USGS conducted a side-scan sonar and bottom sampling survey of a 1000-sq-km section of the continental shelf in the Gulf of Farallones located offshore of San Francisco. The primary goal of this survey was to map an area of critical interest for studying continental shelf sediment dynamics. This survey provided an opportunity to test an image processing scheme that enabled production of a side-scan sonar hard-copy mosaic during the cruise in near real-time.

Large earthquakes and creeping faults

USGS Publications Warehouse

Harris, Ruth A.

2017-01-01

Faults are ubiquitous throughout the Earth's crust. The majority are silent for decades to centuries, until they suddenly rupture and produce earthquakes. With a focus on shallow continental active-tectonic regions, this paper reviews a subset of faults that have a different behavior. These unusual faults slowly creep for long periods of time and produce many small earthquakes. The presence of fault creep and the related microseismicity helps illuminate faults that might not otherwise be located in fine detail, but there is also the question of how creeping faults contribute to seismic hazard. It appears that well-recorded creeping fault earthquakes of up to magnitude 6.6 that have occurred in shallow continental regions produce similar fault-surface rupture areas and similar peak ground shaking as their locked fault counterparts of the same earthquake magnitude. The behavior of much larger earthquakes on shallow creeping continental faults is less well known, because there is a dearth of comprehensive observations. Computational simulations provide an opportunity to fill the gaps in our understanding, particularly of the dynamic processes that occur during large earthquake rupture and arrest.

The George V Land Continental Margin (East Antarctica): new Insights Into Bottom Water Production and Quaternary Glacial Processes from the WEGA project

NASA Astrophysics Data System (ADS)

Caburlotto, A.; de Santis, L.; Lucchi, R. G.; Giorgetti, G.; Damiani, D.; Macri', P.; Tolotti, R.; Presti, M.; Armand, L.; Harris, P.

2004-12-01

The George Vth Land represents the ending of one of the largest subglacial basin (Wilkes Basin) of the East Antarctic Ice Sheet (EAIS). Furthermore, its coastal areas are zone of significant production of High Salinity Shelf Water (HSSW). Piston and gravity cores and high resolution echo-sounding (3.5 kHz) and Chirp profiles collected in the frame of the joint Australian and Italian WEGA (WilkEs Basin GlAcial History) project provide new insights into the Quaternary history of the EAIS and the HSSW across this margin: from the sediment record filling and draping valleys and banks along the continental shelf, to the continuous sedimentary section of the mound-channel system on the continental rise. The discovery of a current-lain sediment drift (Mertz Drift, MD) provides clues to understanding the age of the last glacial erosive events, as well as to infer flow-pathways of bottom-water masses changes. The MD shows disrupted, fluted reflectors due to glacial advance during the LGM (Last Glacial Maximum) in shallow water, while undisturbed sediment drift deposited at greater water depth, indicates that during the LGM the ice shelf was floating over the deep sector of the basin. The main sedimentary environment characterising the modern conditions of the continental rise is dominated by the turbiditic processes with a minor contribution of contour currents action. Nevertheless, some areas (WEGA Channel) are currently characterised by transport and settling of sediment through HSSW, originating in the shelf area. This particular environment likely persisted since pre-LGM times. It could indicate a continuous supply of sedimentary material from HSSW during the most recent both glacial and interglacial cycles. This would be consistent with the results obtained in the continental shelf suggesting that the Ice Sheet was not grounding over some parts of the continental shelf. Furthermore, the comparison of the studied area with other Antarctic margins indicate that, contrary to what happens on the Antarctic Peninsula margin, the relation between the Quaternary sedimentation and the glacial - interglacial cycles are less evident in the lithofacies observed on the continental rise area. This characteristic suggests a different glacial dynamic along the Wilkes Land continental margin that is less sensitive to the small climatic changes, with respect to the western (Antarctic Peninsula) margin.

Polar continental margins: Studies off East Greenland

NASA Astrophysics Data System (ADS)

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

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

Continental drilling for paleoclimatic records: Recommendations from an international workshop

USGS Publications Warehouse

Colman, Steve M.

1995-01-01

The Workshop, entitled "Continental Drilling for Paleoclimate Records", was sponsored by the Past Global Changes (PAGES) Project, a core project of the International Geosphere-Biosphere Programme (IGBP) and by the GeoForschungsZentrum, Potsdam, Germany, in conjunction with the International Continental Drilling Programme (ICDP). The impetus for the meeting was the need for long continental paleoclimate records that will fill gaps left by the marine and ice-core records and provide information on time and spatial scales that are relevant to human activities. Further impetus came from a perceived need to balance the forecasts and reconstructions of climate models with information on actual behavior of the climate system on the continents. The meeting was organized by Steven M. Colman, Suzanne A.G. Leroy, and Jörg F.W. Negendank and was held at the GeoForschungsZentrum, Potsdam, Germany, June 30-July 2, 1995. Because the Workshop was primarily a working meeting, a relatively small number of participants were invited (Appendix 3). Leaders of the PAGES Pole-Equator-Pole (PEP) transects and existing large-lake drilling programs, along with a mixture of technical experts, were the primary group of attendees.

Isotope and fatty acid trends along continental shelf depth gradients: Inshore versus offshore hydrological influences on benthic trophic functioning

NASA Astrophysics Data System (ADS)

Chouvelon, T.; Schaal, G.; Grall, J.; Pernet, F.; Perdriau, M.; A-Pernet, E. J.; Le Bris, H.

2015-11-01

Anthropogenic activities and land-based inputs into the sea may influence the trophic structure and functioning of coastal and continental shelf ecosystems, despite the numerous opportunities and services the latter offer to humans and wildlife. In addition, hydrological structures and physical dynamics potentially influence the sources of organic matter (e.g., terrestrial versus marine, or fresh material versus detrital material) entering marine food webs. Understanding the significance of the processes that influence marine food webs and ecosystems (e.g., terrestrial inputs, physical dynamics) is crucially important because trophic dynamics are a vital part of ecosystem integrity. This can be achieved by identifying organic matter sources that enter food webs along inshore-offshore transects. We hypothesised that regional hydrological structures over wide continental shelves directly control the benthic trophic functioning across the shelf. We investigated this issue along two transects in the northern ecosystem of the Bay of Biscay (north-eastern Atlantic). Carbon and nitrogen stable isotope analysis (SIA) and fatty acid analysis (FAA) were conducted on different complementary ecosystem compartments that include suspended particulate organic matter (POM), sedimentary organic matter (SOM), and benthic consumers such as bivalves, large crustaceans and demersal fish. Samples were collected from inshore shallow waters (at ∼1 m in depth) to more than 200 m in depth on the offshore shelf break. Results indicated strong discrepancies in stable isotope (SI) and fatty acid (FA) compositions in the sampled compartments between inshore and offshore areas, although nitrogen SI (δ15N) and FA trends were similar along both transects. Offshore the influence of a permanently stratified area (described previously as a ;cold pool;) was evident in both transects. The influence of this hydrological structure on benthic trophic functioning (i.e., on the food sources available for consumers) was especially apparent across the northern transect, due to unusual carbon isotope compositions (δ13C) in the compartments. At stations under the cold pool, SI and FA organism compositions indicated benthic trophic functioning based on a microbial food web, including a significant contribution of heterotrophic planktonic organisms and/or of SOM, notably in stations under the cold pool. On the contrary, inshore and shelf break areas were characterised by a microalgae-based food web (at least in part for the shelf break area, due to slope current and upwelling that can favour fresh primary production sinking on site). SIA and FAA were relevant and complementary tools, and consumers better medium- to long-term system integrators than POM samples, for depicting the trophic functioning and dynamics along inshore-offshore transects over continental shelves.

30 CFR 252.3 - Oil and gas data and information to be provided for use in the OCS Oil and Gas Information Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Oil and gas data and information to be provided for use in the OCS Oil and Gas Information Program. 252.3 Section 252.3 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OUTER CONTINENTAL SHELF (OCS) OIL AND GAS INFORMATION PROGRAM § 252.3 Oil and gas data and...

Renewed classification within Goniurosaurus (Squamata: Eublepharidae) uncovers the dual roles of a continental island (Hainan) in species evolution.

PubMed

Liang, Bin; Zhou, Run-Bang; Liu, Yan-Lin; Chen, Bei; Grismer, L Lee; Wang, Ning

2018-06-12

Continental islands are often dynamic in regard to the origin and evolution of their biota. Although colonizations from mainland Southeast Asia to Hainan Island have been reported, the role of Hainan Island as a source for continental biota has not been considered. Goniurosaurus is a genus comprised of nocturnal ground geckos. We reexamined the evolutionary history of Goniurosaurus using both molecular phylogenetics and morphological comparisons. All phylogenetic trees recovered G. zhoui as sister to G. hainanensis + G. lichtenfelderi, which together are the sister lineage of G. bawanglingensis. The recovery of this "Hainan clade" contradicts previous classifications that placed G. bawanglingensis within the G. luii group. Moreover, ancestral trait reconstruction revealed that body band number might have decreased two or three times independently within Goniurosaurus from four to three. The divergence between the continental G. luii group and the Hainan clade was estimated at ∼34.7 Mya (CI = 22.3-48.6), possibly correlating with the vicariance event between Hainan Island and the mainland. G. lichtenfelderi diverged from G. hainanensis very recently, which might be associated with a historical dispersal event from Hainan Island to Vietnam during glacial periods. Our study improves the understanding of Goniurosaurus systematics and reveals the important role of Hainan Island in bidirectional colonizations. Copyright © 2018 Elsevier Inc. All rights reserved.

A New Paradigm for New Oceans

NASA Astrophysics Data System (ADS)

Foulger, G. R.; Doré, A. G.; Franke, D.; Geoffroy, L.; Gernigon, L.; Hole, M.; Hoskuldsson, A.; Julian, B. R.; Kusznir, N.; Martinez, F.; Natland, J. H.; Peace, A.; Petersen, K. D.; Schiffer, C.; Stephenson, R.; Stoker, M. S.

2017-12-01

The original simple theory of plate tectonics had to be refined to accommodate second-order geological features such as back-arc basins and continental deformation zones. We propose an additional refinement that is required by complexities that form and persist in new oceans when inhomogeneous continental lithosphere/tectosphere disintegrates. Such complexities include continual plate-boundary reorganizations and migrations, distributed continental material in the ocean, propagating and dying ridges, and sagging, flexing and tilting in the oceans and at continent-ocean boundary zones. Reorganizations of stress and motion persist, resulting in variable orientations over short distances, tectonic reactivations, complex plate boundary configurations including multiple triple junctions, and the formation and abandonment of oceanic microplates. Resulting local compressions and extensions are manifest as bathymetric anomalies, vertical motions, and distributed volcanism at various times and places as the new ocean grows. Examples of regions that exhibit some or all of these features include the North Atlantic, the Rio Grande Rise/Walvis Ridge region of the South Atlantic, and the Seychelles-Mauritius region in the Indian Ocean. We suggest that these complexities arise as a result of the formation of new spreading plate boundaries by rifts propagating through continental lithosphere/tectosphere that is anisotropic as a result of inherited structure/composition and/or a sub-lithospheric mantle destabilized by lithospheric-controlled processes. Such scenarios result in complicated disintegration of continents and local persistent dynamic instability in the new ocean.

High regional climate sensitivity over continental China constrained by glacial-recent changes in temperature and the hydrological cycle.

PubMed

Eagle, Robert A; Risi, Camille; Mitchell, Jonathan L; Eiler, John M; Seibt, Ulrike; Neelin, J David; Li, Gaojun; Tripati, Aradhna K

2013-05-28

The East Asian monsoon is one of Earth's most significant climatic phenomena, and numerous paleoclimate archives have revealed that it exhibits variations on orbital and suborbital time scales. Quantitative constraints on the climate changes associated with these past variations are limited, yet are needed to constrain sensitivity of the region to changes in greenhouse gas levels. Here, we show central China is a region that experienced a much larger temperature change since the Last Glacial Maximum than typically simulated by climate models. We applied clumped isotope thermometry to carbonates from the central Chinese Loess Plateau to reconstruct temperature and water isotope shifts from the Last Glacial Maximum to present. We find a summertime temperature change of 6-7 °C that is reproduced by climate model simulations presented here. Proxy data reveal evidence for a shift to lighter isotopic composition of meteoric waters in glacial times, which is also captured by our model. Analysis of model outputs suggests that glacial cooling over continental China is significantly amplified by the influence of stationary waves, which, in turn, are enhanced by continental ice sheets. These results not only support high regional climate sensitivity in Central China but highlight the fundamental role of planetary-scale atmospheric dynamics in the sensitivity of regional climates to continental glaciation, changing greenhouse gas levels, and insolation.

Continental shelf processes affecting the oceanography of the South Atlantic Bight: Progress report, June 1, 1987 to May 31, 1988. [FLEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atkinson, L.P.

This study of continental shelf processes affecting the oceanography of the South Atlantic Bight (SAB) is part of the interdisciplinary DOE-sponsored South Atlantic Bight Program. Our part of the program involves hydrographic and nutrient characteristics of the region. Current research efforts in the SAB Program are being focused on the inner shelf region where effects of bottom friction, local wind forcing, river and estuarine discharge, and tides, which are all small scale processes, are important. Our major accomplishment during the past year was the completion of the FLEX (Fall Experiment) field study. Since most of our data collection is computerized,more » preliminary hydrographic data analysis was done on board ship during the cruise and preliminary results are available. These results will be presented in this report. We are just beginning our standard data processing and data analysis procedures. We continued the processing and analysis of SPREX data collected during April 1985. Work has also continued on the older GABEX I and II data sets. 8 refs., 19 figs., 2 tabs.« less

Double subduction of continental lithosphere, a key to form wide plateau

NASA Astrophysics Data System (ADS)

Replumaz, Anne; Funiciello, Francesca; Reitano, Riccardo; Faccenna, Claudio; Balon, Marie

2016-04-01

The mechanisms involved in the creation of the high and wide topography, like the Tibetan Plateau, are still controversial. In particular, the behaviour of the indian and asian lower continental lithosphere during the collision is a matter of debate, either thickening, densifying and delaminating, or keeping its rigidity and subducting. But since several decades seismicity, seismic profiles and global tomography highlight the lithospheric structure of the Tibetan Plateau, and make the hypotheses sustaining the models more precise. In particular, in the western syntaxis, it is now clear that the indian lithosphere subducts northward beneath the Hindu Kush down to the transition zone, while the asian one subducts southward beneath Pamir (e.g. Negredo et al., 2007; Kufner et al., 2015). Such double subduction of continental lithospheres with opposite vergence has also been inferred in the early collision time. Cenozoic volcanic rocks between 50 and 30 Ma in the Qiangtang block have been interpreted as related to an asian subduction beneath Qiangtang at that time (De Celles et al., 2011; Guillot and Replumaz, 2013). We present here analogue experiments silicone/honey to explore the subduction of continental lithosphere, using a piston as analogue of far field forces. We explore the parameters that control the subductions dynamics of the 2 continental lithospheres and the thickening of the plates at the surface, and compare with the Tibetan Plateau evolution. We show that a continental lithosphere is able to subduct in a collision context, even lighter than the mantle, if the plate is rigid enough. In that case the horizontal force due to the collision context, modelled by the piston push transmitted by the indenter, is the driving force, not the slab pull which is negative. It is not a subduction driving by the weight of the slab, but a subduction induced by the collision, that we could call "collisional subduction".

Magma-poor vs. magma-rich continental rifting and breakup in the Labrador Sea

NASA Astrophysics Data System (ADS)

Gouiza, M.; Paton, D.

2017-12-01

Magma-poor and magma-rich rifted margins show distinct structural and stratigraphic geometries during the rift to breakup period. In magma-poor margins, crustal stretching is accommodated mainly by brittle faulting and the formation of wide rift basins shaped by numerous graben and half-graben structures. Continental breakup and oceanic crust accretion are often preceded by a localised phase of (hyper-) extension where the upper mantle is embrittled, serpentinized, and exhumed to the surface. In magma-rich margins, the rift basin is narrow and extension is accompanied by a large magmatic supply. Continental breakup and oceanic crust accretion is preceded by the emplacement of a thick volcanic crust juxtaposing and underplating a moderately thinned continental crust. Both magma-poor and magma-rich rifting occur in response to lithospheric extension but the driving forces and processes are believed to be different. In the former extension is assumed to be driven by plate boundary forces, while in the latter extension is supposed to be controlled by sublithospheric mantle dynamics. However, this view fails in explaining observations from many Atlantic conjugate margins where magma-poor and magma-rich segments alternate in a relatively abrupt fashion. This is the case of the Labrador margin where the northern segment shows major magmatic supply during most of the syn-rift phase which culminate in the emplacement of a thick volcanic crust in the transitional domain along with high density bodies underplating the thinned continental crust; while the southern segment is characterized mainly by brittle extension, mantle seprentinization and exhumation prior to continental breakup. In this work, we use seismic and potential field data to describe the crustal and structural architectures of the Labrador margin, and investigate the tectonic and mechanical processes of rifting that may have controlled the magmatic supply in the different segments of the margin.

15 CFR 930.81 - Multiple permit review.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT FEDERAL CONSISTENCY WITH APPROVED COASTAL MANAGEMENT PROGRAMS Consistency for Outer Continental... applicable to OCS-related federal license or permit activities affecting any coastal use or resource which...

15 CFR 930.81 - Multiple permit review.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT FEDERAL CONSISTENCY WITH APPROVED COASTAL MANAGEMENT PROGRAMS Consistency for Outer Continental... applicable to OCS-related federal license or permit activities affecting any coastal use or resource which...

15 CFR 930.81 - Multiple permit review.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT FEDERAL CONSISTENCY WITH APPROVED COASTAL MANAGEMENT PROGRAMS Consistency for Outer Continental... applicable to OCS-related federal license or permit activities affecting any coastal use or resource which...

15 CFR 930.81 - Multiple permit review.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT FEDERAL CONSISTENCY WITH APPROVED COASTAL MANAGEMENT PROGRAMS Consistency for Outer Continental... applicable to OCS-related federal license or permit activities affecting any coastal use or resource which...

15 CFR 930.81 - Multiple permit review.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE OCEAN AND COASTAL RESOURCE MANAGEMENT FEDERAL CONSISTENCY WITH APPROVED COASTAL MANAGEMENT PROGRAMS Consistency for Outer Continental... applicable to OCS-related federal license or permit activities affecting any coastal use or resource which...

California State Waters Map Series--Hueneme Canyon and vicinity, California

USGS Publications Warehouse

Johnson, Samuel Y.; Dartnell, Peter; Cochrane, Guy R.; Golden, Nadine E.; Phillips, Eleyne L.; Ritchie, Andrew C.; Kvitek, Rikk G.; Greene, H. Gary; Krigsman, Lisa M.; Endris, Charles A.; Clahan, Kevin B.; Sliter, Ray W.; Wong, Florence L.; Yoklavich, Mary M.; Normark, William R.

2012-01-01

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Hueneme Canyon and vicinity map area lies within the eastern Santa Barbara Channel region of the Southern California Bight. The area is part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation - at least 90° - since the early Miocene has been proposed for the Western Transverse Ranges, and the region is presently undergoing north-south shortening. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area, which is offshore of the Oxnard plain and west of and along the trend of the south flank of the Santa Monica Mountains, lies at the east end of the Santa Barbara littoral cell, characterized by west-to-east littoral transport of sediment derived mainly from coastal watersheds. The Hueneme Canyon and vicinity map area in California's State Waters is characterized by two major physiographic features: (1) the nearshore continental shelf, and (2) the Hueneme and Mugu Submarine Canyon system, which, in the map area, includes Hueneme Canyon and parts of three smaller, unnamed headless canyons incised into the shelf southeast of Hueneme Canyon. The shelf is underlain by tens of meters of interbedded upper Quaternary shelf, estuarine, and fluvial deposits that formed as sea level fluctuated in the last several hundred thousand years. Hueneme Canyon extends about 15 km offshore from its canyon head near the dredged navigation channel of the Port of Hueneme. The canyon is relatively deep (about 150 m at the California's State Waters limit) and steep (canyon flanks as steep as 25° to 30°). Historically, Hueneme Canyon functioned as the eastern termination of the Santa Barbara littoral cell by trapping all eastward littoral drift, not only feeding the large Hueneme submarine fan but acting as the major conduit of sediment to the deep Santa Monica Basin; however, recent dredging programs needed to maintain Channel Islands Harbor and the Port of Hueneme have moved the nearshore sediment trapped by jetties and breakwaters to an area southeast of the Hueneme Canyon head. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft sediment and isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Hueneme Canyon and vicinity map area are related directly to the geomorphology and sedimentary processes that are the result of its Quaternary geologic history. The two basic megahabitats in the map area are Shelf (continental shelf) and Flank (continental slope). The flat seafloor of the continental shelf in the Hueneme Canyon and vicinity map area is dynamic, as indicated by mobile sand sheets and coarser grained scour depressions. The active Hueneme Canyon provides considerable relief to the continental shelf in the map area, and its irregular morphology of eroded walls, landslide scarps, and deposits and gullies provide promising habitat for groundfish, crabs, shrimp, and other marine benthic organisms. Most invertebrates observed in the map area during camera ground-truth field operations are found on the edge of Hueneme Canyon, which may be an important area of recruitment and retention to other invertebrates and fishes. The smaller, more subtle, nonactive headless canyons located primarily on the continental slope also offer relief that provides habitat for groundfish and other organisms.

Integrating deep Earth dynamics in paleogeographic reconstructions of Australia

NASA Astrophysics Data System (ADS)

Heine, Christian; Müller, R. Dietmar; Steinberger, Bernhard; DiCaprio, Lydia

2010-03-01

It is well documented that the Cenozoic progressive flooding of Australia, contemporaneous with a eustatic sea level fall, requires a downward tilting of the Australian Plate towards the SE Asian subduction system. Previously, this large-scale, mantle-convection driven dynamic topography effect has been approximated by computing the time-dependent vertical shifts and tilts of a plane, but the observed subsidence and uplift anomalies indicate a more complex interplay between time-dependent mantle convection and plate motion. We combine plate kinematics with a global mantle backward-advection model based on shear-wave mantle tomography, paleogeographic data, eustatic sea level estimates and basin stratigraphy to reconstruct the Australian flooding history for the last 70 Myrs on a continental scale. We compute time-dependent dynamic surface topography and continental inundation of a digital elevation model adjusted for sediment accumulation. Our model reveals two evolving dynamic topography lows, over which the Australian plate has progressively moved. We interpret the southern low to be caused by sinking slab material with an origin along the eastern Gondwana subduction zone in the Cretaceous, whereas the northern low, which first straddles northern Australia in the Oligocene, is mainly attributable to material subducted north and northeast of Australia. Our model accounts for the Paleogene exposure of the Gulf of Carpentaria region at a time when sea level was much higher than today, and explains anomalous Late Tertiary subsidence on Australia's northern, western and southern margins. The resolution of our model, which excludes short-wavelength mantle density anomalies and is restricted to depths larger than 220 km, is not sufficient to model the two well recorded episodes of major transgressions in South Australia in the Eocene and Miocene. However, the overall, long-wavelength spatio-temporal pattern of Australia's inundation record is well captured by combining our modelled dynamic topography with a recent eustatic sea level curve. We suggest that the apparent Late Cenozoic northward tilting of Australia was a stepwise function of South Australia first moving away northwards from the Gondwana subduction-related dynamic topography low in the Oligocene, now found under the Australian-Antarctic Discordance, followed by a drawing down of northern Australia as it overrode a slab burial ground now underlying much of the northern half of Australia, starting in the Miocene. Our model suggests that today's geography of Australia is strongly dependent on mantle forces. Without mantle convection, which draws Australia down by up to 300 m, nearly all of Australia's continental shelves would be exposed. We conclude that dissecting the interplay between eustasy and mantle-driven dynamic topography is critical for understanding hinterland uplift, basin subsidence, the formation and destruction of shallow epeiric seas and their facies distribution, but also for the evolution of petroleum systems.

Breakup Style and Magmatic Underplating West of the Lofoten Islands, Norway, Based on OBS Data.

NASA Astrophysics Data System (ADS)

Breivik, A. J.; Faleide, J. I.; Mjelde, R.; Murai, Y.; Flueh, E. R.

2014-12-01

The breakup of the Northeast Atlantic in the Early Eocene was magma-rich, forming the major part of the North Atlantic Igneous Province (NAIP). This is seen as extrusive and intrusive magmatism in the continental domain, and as a thicker than normal oceanic crust produced the first few million years after continental breakup. The maximum magma productivity and the duration of excess magmatism varies along the margins of Northwest Europe and East Greenland, to some extent as a function of the distance from the Iceland hotspot. The Vøring Plateau off mid-Norway is the northernmost of the margin segments in northwestern Europe with extensive magmatism. North of the plateau, magmatism dies off towards the Lofoten Margin, marking the northern boundary of the NAIP here. In 2003, as part of the Euromargins Program we collected an Ocean Bottom Seismometer (OBS) profile from mainland Norway, across the Lofoten Islands, and out into the deep ocean. Forward velocity modeling using raytracing reveals a continental margin that shows transitional features between magma-rich and magma-poor rifting. On one hand, we detect an up to 2 km thick and 40-50 km wide magmatic underplate of the outer continent, on the other hand, continental thinning is greater and intrusive magmatism less than farther south. Continental breakup also appears to be somewhat delayed compared to breakup on the Vøring Plateau, consistent with increased extension. This indicates that magmatic diking, believed to quickly lead to continental breakup of volcanic margins and thus to reduce continental thinning, played a much lesser role here than at the plateau. Early post-breakup oceanic crust is up to 8 km thick, less than half of that observed farther south. The most likely interpretation of these observations, is that the source for the excess magmatism of the NAIP was not present at the Lofoten Margin during rifting, and that the excess magmatism actually observed was the result of lateral transport from the south around breakup time.

The Potential of Carbonyl Sulfide as a Proxy for Gross Primary Production at Flux Tower Sites

USDA-ARS?s Scientific Manuscript database

Regional and continental scale studies of the seasonal dynamics of atmospheric carbonyl sulfide (OCS) mole fractions and leaf-level studies of plant OCS exchange have shown a close relationship with those for CO2. CO2 has sinks and sources within terrestrial ecosystems, but the primary terrestrial e...

30 CFR 250.432 - How do I obtain a departure to diverter design and installation requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Diverter System Requirements § 250.432 How do I obtain a departure to diverter... diverter line for floating drilling operations on a dynamically positioned drillship Maintain an...

30 CFR 250.432 - How do I obtain a departure to diverter design and installation requirements?

Code of Federal Regulations, 2013 CFR

2013-07-01

... ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Diverter System Requirements § 250.432 How do I obtain a... least 8 inches. (d) Use a single diverter line for floating drilling operations on a dynamically...

30 CFR 250.432 - How do I obtain a departure to diverter design and installation requirements?

Code of Federal Regulations, 2014 CFR

2014-07-01

... ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Diverter System Requirements § 250.432 How do I obtain a... least 8 inches. (d) Use a single diverter line for floating drilling operations on a dynamically...

30 CFR 250.432 - How do I obtain a departure to diverter design and installation requirements?

Code of Federal Regulations, 2012 CFR

2012-07-01

... ENVIRONMENTAL ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Diverter System Requirements § 250.432 How do I obtain a... least 8 inches. (d) Use a single diverter line for floating drilling operations on a dynamically...

Multi-Annual Data Products on Turbulent Heat Fluxes at the Local and Continental Scale Using AATSR and FY-2 Data

NASA Astrophysics Data System (ADS)

Menenti, M.; Ghafarian, H.; Tang, B.; Faivre, R.; Colin, J.; Jia, L.; Roupios, L.

2013-01-01

This paper summarizes the results of studies carried in the framework of the Dragon 2 Program - Project 5322 Key Eco-Hydrological Parameters Retrieval and Land Data Assimilation System Development in a Typical Inland River Basin of Chinas Arid Region. The investigations were focused on monitoring the fluxes of energy and water at the land-atmosphere interface across a range of spatial scales, using multi-spectral radiometric data collected by space-borne imaging radiometers. At the local scale a new approach to parameterize heat and vapour fluxes was developed and applied using Computational Fluid Dynamics to describe state and dynamics of the boundary layer over the heterogeneous and 3D structured land surface. An airborne scanning LIDAR was used to capture in detail surface geometry. Over the large area of the Qinghai-Tibet Plateau a land-atmospheric model was used to characterize the atmospheric Planetary Boundary Layer. The effect of land surface heterogeneity and structure on the exchange of heat and water was captured using the bi-angular observations of brightness temperature provided by the AATSR imaging radiometer. The heat and water flux densities were calculated hourly with Feng-Yun C, D and E VISSR data over the Qinghai-Tibet Plateau and the headwaters of main rivers around it.

USArray Imaging of Continental Crust in the Conterminous United States

NASA Astrophysics Data System (ADS)

Ma, Xiaofei; Lowry, Anthony R.

2017-12-01

The thickness and bulk composition of continental crust provide important constraints on the evolution and dynamics of continents. Crustal mineralogy and thickness both may influence gravity anomalies, topographic elevation, and lithospheric strength, but prior to the inception of EarthScope's USArray, seismic measurements of crustal thickness and properties useful for inferring lithology are sparse. Here we improve upon a previously published methodology for joint inversion of Bouguer gravity anomalies and seismic receiver functions by using parameter space stacking of cross correlations of modeled synthetic and observed receiver functions instead of standard H-κ amplitude stacking. The new method is applied to estimation of thickness and bulk seismic velocity ratio, vP/vS, of continental crust in the conterminous United States using USArray and other broadband network data. Crustal thickness variations are reasonably consistent with those found in other studies and show interesting relationships to the history of North American continental formation. Seismic velocity ratios derived in this study are more robust than in other analyses and hint at large-scale variations in composition of continental crust. To interpret the results, we model the pressure-/temperature-dependent thermodynamics of mineral formation for various crustal chemistries, with and without volatile constituents. Our results suggest that hydration lowers bulk crustal vP/vS and density and releases heat in the shallow crust but absorbs heat in the lowermost crust (where plagioclase breaks down to pyroxene and garnet resulting in higher seismic velocity). Hence, vP/vS variations may provide a useful proxy for hydration state in the crust.

Inferring Source Regions and Supply Mechanisms of Iron in the Southern Ocean from Satellite Data

NASA Astrophysics Data System (ADS)

Graham, R. M.

2016-02-01

In many biogeochemical models a large shelf sediment iron flux is prescribed through the seafloor over all areas of bathymetry shallower than 1000 m. Here we infer the likely location of shelf sediment iron sources by identifying where mean annual satellite chlorophyll concentrations are enhanced over shallow bathymetry ( < 1000 m). We show that mean annual chlorophyll concentrations are not visibly enhanced over areas of shallow bathymetry located more than 500 km from a coastline. Chlorophyll concentrations > 2 mg m-3are only found within 50 km of a continental or island coastline. These results suggest that large sedimentary iron fluxes only exist on continental or island shelves. Large sedimentary iron fluxes are unlikely to be found on isolated seamounts and submerged plateaus. We further compare satellite chlorophyll concentrations to the position of ocean fronts to assess the relative role of horizontal advection and upwelling for supplying iron to the ocean surface. Sharp gradients in chlorophyll concentrations are observed across western boundary currents. Large chlorophyll blooms develop where western boundary currents detach from the continental shelves and turn eastwards into the Southern Ocean. Chlorophyll concentrations are enhanced along contours of sea surface height extending off continental and island shelves. These observations support the hypothesis that bioavailable iron from continental shelves is entrained into western boundary currents and advected into the Sub-Antarctic Zone along the Dynamical Subtropical Front. Likewise, iron from island shelves is entrained into nearby fronts and advected downstream. Mean annual chlorophyll concentrations are very low in open ocean regions with large modelled upwelling velocities, where fronts cross over topographic ridges. These results suggests that open ocean upwelling is unlikely to deliver iron to the surface from deep sources such as hydrothermal vents.

Two-layer Crustal Structure of the Contiguous United States from Joint Inversion of USArray Receiver Functions and Gravity

NASA Astrophysics Data System (ADS)

Ma, X.; Lowry, A. R.

2015-12-01

The composition and thickness of crustal layering is fundamental to understanding the evolution and dynamics of continental lithosphere. Lowry and Pérez-Gussinyé (2011) found that the western Cordillera of the United States, characterized by active deformation and high heat flow, is strongly correlated with low bulk crustal seismic velocity ratio. They interpreted this observation as evidence that quartz controls continental tectonism and deformation. We will present new imaging of two-layer crustal composition and structure from cross-correlation of observed receiver functions and model synthetics. The cross-correlation coefficient of the two-layer model increases significantly relative to an assumed one-layer model, and the lower crustal thickness map from raw two-layer modeling (prior to Bayesian filtering with gravity models and Optimal Interpolation) clearly shows Colorado plateau and Appalachian boundaries, which are not apparent in upper crustal models, and also the high vP/vS fill the most of middle continental region while low vP/vS are on the west and east continental edge. In the presentation, we will show results of a new algorithm for joint Bayesian inversion of thickness and vP/vS of two-layer continental crustal structure. Recent thermodynamical modeling of geophysical models based on lab experiment data (Guerri et al., 2015) found that a large impedance contrast can be expected in the midcrust due to a phase transition that decreases plagioclase and increases clinopyroxene, without invoking any change in crustal chemistry. The depth of the transition depends on pressure, temperature and hydration, and in this presentation we will compare predictions of layer thicknesses and vP/vS predicted by mineral thermodynamics to those we observe in the USArray footprint.

Interannual evolutions of (sub)mesoscale dynamics in the Bay of Biscay and the English Channel

NASA Astrophysics Data System (ADS)

Charria, G.; Vandermeirsch, F.; Theetten, S.; Yelekçi, Ö.; Assassi, C.; Audiffren, N. J.

2016-02-01

In a context of global change, ocean regions as the Bay of the Biscay and the English Channel represent key domains to estimate the local impact on the coasts of interannual evolutions. Indeed, the coastal (considering in this project regions above the continental shelf) and regional (including the continental slope and the abyssal plain) environments are sensitive to the long-term fluctuations driven by the open ocean, the atmosphere and the watersheds. These evolutions can have impacts on the whole ecosystem. To understand and, by extension, forecast evolutions of these ecosystems, we need to go further in the description and the analysis of the past interannual variability over decadal to pluri-decadal periods. This variability can be described at different spatial scales from small (< 1 km) to basin scales (> 100 km). With a focus on smaller scales, the modelled dynamics, using a Coastal Circulation Model on national computing resources (GENCI/CINES), is discussed from interannual simulations (10 to 53 years) with different spatial (4 km to 1 km) and vertical (40 to 100 sigma levels) resolutions compared with available in situ observations. Exploring vorticity and kinetic energy based diagnostics; dynamical patterns are described including the vertical distribution of the mesoscale activity. Despite the lack of deep and spatially distributed observations, present numerical experiments draw a first picture of the 3D mesoscale distribution and its evolution at interannual time scales.

High-Resolution Lithosphere Viscosity and Dynamics Revealed by Magnetotelluric Imaging

NASA Astrophysics Data System (ADS)

Liu, L.; Hasterok, D. P.

2016-12-01

An accurate viscosity structure is critical to truthfully modeling continental lithosphere dynamics, especially at spatial scales of <200 km where active tectonic deformation and volcanism occur. However, the effective viscosity structure of the lithosphere remains a key challenge in geodynamics due to the intimate involvement of viscosity with time and its dependence on many factors including strain rate, plastic failure, composition, and grain size. Current efforts on inferring the detailed lithosphere viscosity structure are sparse and large uncertainties and discrepancies still exist. Here we report an attempt to infer the effective lithospheric viscosity from a high-resolution magnetotelluric (MT) survey across the western United States. The high sensitivity of MT fields to the presence of electrically conductive fluids makes it a promising proxy for determining mechanical strength variations throughout the lithosphere. We demonstrate how a viscosity structure, approximated from electrical resistivity, results in a geodynamic model that successfully predicts short-wavelength surface topography, lithospheric deformation, and mantle upwelling beneath recent volcanism. The results indicate that lithosphere viscosity structure rather than the buoyancy structure is the dominant controlling factor for short-wavelength topography and intra-plate deformation in tectonically active regions. We further show that this viscosity is consistent with and more effective than that derived from laboratory-based rheology. We therefore propose that MT imaging provides a practical observational constraint for quantifying the dynamic evolution of the continental lithosphere.

Assessing streamflow sensitivity to variations in glacier mass balance

USGS Publications Warehouse

O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis

2014-01-01

The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.

What are the Effects of Protest Fear?

DTIC Science & Technology

2014-06-01

Program AT&L Acquisition, Technology, and Logistics BPA blanket purchase agreement CONUS continental United States COR...they have awarded a task/delivery order against an IDIQ contract (or Blanket Purchase Agreement [ BPA ]) in order to avoid a bid protest. The data shows

75 FR 76632 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Increased Safety Measures for...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-09

...? * * * * * (d) In areas containing permafrost, setting depths for conductor and surface casing based on the anticipated depth of the permafrost. Your program must provide protection from thaw subsidence and freezeback...

Mapping the extent of thinned continental crust across the Orphan Basin, offshore Newfoundland, Canada, using a combination of vintage and new seismic refraction/wide-angle reflection data

NASA Astrophysics Data System (ADS)

Welford, J. Kim; Dehler, Sonya; Funck, Thomas

2017-04-01

The SIGNAL (Seismic Investigations off Greenland, Newfoundland and Labrador) 2009 cruise was undertaken by the Geological Survey of Canada (GSC) and the Geological Survey of Denmark and Greenland (GEUS), with scientific contributions from Dalhousie University, to collect refraction/wide-angle reflection (RWAR) profiles as part of each country's continental shelf program under UNCLOS (United Nations Convention on the Law of the Sea) Article 76. Line 1 extended from the Bonavista Platform off Newfoundland, across the Orphan Basin, to Orphan Knoll and beyond into oceanic crust. The line followed the same track as an earlier seismic refraction line and ocean-bottom seismometer (OBS) locations were chosen to complement and to extend the original station coverage. The final crustal velocity model across Orphan Basin shows thinned continental crust (15 to 20 km thick) beneath most of the basin with thinner crust (10 km thick) immediately outboard of the Bonavista Platform, interpreted as a failed rift zone. Seaward of the failed rift, the velocity structure of the thinned continental crust is generally uniform over 250 km toward Orphan Knoll. Immediately outboard of Orphan Knoll, the crust thins to 8 km and exhibits a velocity structure consistent with oceanic crust. The results from modelling of the combined refraction/wide-angle reflection dataset support an extension of Canada's continental shelf beyond the seaward limits of the Orphan Basin.

Predictive Modeling of Risk Associated with Temperature Extremes over Continental US

NASA Astrophysics Data System (ADS)

Kravtsov, S.; Roebber, P.; Brazauskas, V.

2016-12-01

We build an extremely statistically accurate, essentially bias-free empirical emulator of atmospheric surface temperature and apply it for meteorological risk assessment over the domain of continental US. The resulting prediction scheme achieves an order-of-magnitude or larger gain of numerical efficiency compared with the schemes based on high-resolution dynamical atmospheric models, leading to unprecedented accuracy of the estimated risk distributions. The empirical model construction methodology is based on our earlier work, but is further modified to account for the influence of large-scale, global climate change on regional US weather and climate. The resulting estimates of the time-dependent, spatially extended probability of temperature extremes over the simulation period can be used as a risk management tool by insurance companies and regulatory governmental agencies.

Evidence for a palaeo-subglacial lake on the Antarctic continental shelf

PubMed Central

Kuhn, Gerhard; Hillenbrand, Claus-Dieter; Kasten, Sabine; Smith, James A.; Nitsche, Frank O.; Frederichs, Thomas; Wiers, Steffen; Ehrmann, Werner; Klages, Johann P.; Mogollón, José M.

2017-01-01

Subglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized. Here we present evidence for a palaeo-subglacial lake on the Antarctic continental shelf. A distinct sediment facies recovered from a bedrock basin in Pine Island Bay indicates deposition within a low-energy lake environment. Diffusive-advection modelling demonstrates that low chloride concentrations in the pore water of the corresponding sediments can only be explained by initial deposition of this facies in a freshwater setting. These observations indicate that an active subglacial meltwater network, similar to that observed beneath the extant ice sheet, was also active during the last glacial period. It also provides a new framework for refining the exploration of these unique environments. PMID:28569750

Multidisciplinary scientific program of investigation of the structure and evolution of the Demerara marginal plateau

NASA Astrophysics Data System (ADS)

Loncke, Lies; Basile, Christophe; Roest, Walter; Graindorge, David; Mercier de Lépinay, Marion; Klinghelhoefer, Frauke; Heuret, Arnauld; Pattier, France; Tallobre, Cedric; Lebrun, Jean-Frédéric; Poetisi, Ewald; Loubrieu, Benoît; Iguanes, Dradem, Margats Scientific Parties, Plus

2017-04-01

Mercier de Lépinay et al. published in 2016 an updated inventory of transform passive margins in the world. This inventory shows that those margins represent 30% of continental passive margins and a cumulative length of 16% of non-convergent margins. It also highlights the fact that many submarine plateaus prolong transform continental margins, systematically at the junction of oceanic domains of different ages. In the world, we identified twenty of those continental submarine plateaus (Falklands, Voring, Demerara, Tasman, etc). Those marginal plateaus systematically experiment two phases of deformation: a first extensional phase and a second transform phase that allows the individualization of those submarine reliefs appearing on bathymetry as seaward continental-like salients. The understanding of the origin, nature, evolution of those marginal plateaus has many scientific and economic issues. The Demerara marginal plateau located off French Guiana and Surinam belongs to this category of submarine provinces. The French part of this plateau has been the locus of a first investigation in 2003 in the framework of the GUYAPLAC cruise dedicated to support French submissions about extension of the limit of the continental shelf beyond 200 nautical miles. This cruise was the starting point of a scientific program dedicated to geological investigations of the Demerara plateau that was sustained by different cruises and collaborations (1) IGUANES (2013) that completed the mapping of this plateau including off Surinam, allowed to better understand the segmentation of the Northern edge of this plateau, and to evidence the combined importance of contourite and mass-wasting processes in the recent sedimentary evolution of this domain, (2) Collaboration with TOTAL (Mercier de Lépinay's PhD thesis) that allowed to better qualify the two main phases of structural evolution of the plateau respectively during Jurassic times for its Western border, Cretaceous times for its Northern and Eastern border (2) DRADEM (2016) (see poster session) that better mapped the continental slope domain of the transform margin north of the Demerara plateau and was dedicated to the dredging of rocks outcropping on the continental slope, suspected to be Cretaceous in age and older, (3) MARGATS (2016) (see poster session) that was dedicated to the better understanding of the internal structure of the plateau and its different margins using multi-channels seismic and refraction methods. The combination of all those experiments allow us to paint an integrated portrait of the Demerara marginal plateau - that may be very useful in understanding the processes involved (1) in the individualization of such plateaus (volcanism, heritages, kinematics, …) (2) in their evolution (subsidence, mass-wasting processes, domains of deep-sea current acceleration). In the future, those scientific advances may allow to better define the natural resources associated with such marginal domains.

Sediment Dynamics and Geohazards offshore Uruguay and Northern Argentina: First Results from the multi-disciplinary Meteor-Cruise M78-3

NASA Astrophysics Data System (ADS)

Krastel, Sebastian; Freudenthal, Tim; Hanebuth, Till; Preu, Benedict; Schwenck, Tilmann; Strasser, Michael; Violante, Roberto; Wefer, Gerold; Winkelmann, Daniel

2010-05-01

About 90% of the sediments generated by weathering and erosion on land get finally deposited at the ocean margins. The sediment distribution processes and landscape evolution on land are relatively well understood, but comparably little is known about the role and relative importance of marine sediment dynamics in controlling the architectural evolution of ocean margins. Important players include hemi-pelagic settling, down-slope and current-controlled along-slope sediment transport, depositional and post-depositional sedimentary processes (e.g. consolidation and diagenesis), as well as the destabilization of sediment bodies and their erosion. Submarine landslides in this context thus may represent an important sediment transport process, but also a major geo-hazard due to the increasing number of offshore constructions as well as their potential to instantaneously displace large water masses triggering waves in densely populated coastal areas. Here we present first results from a seagoing expedition that aimed at investigating the interaction processes of sediment redistribution, partitioning, deposition and diagenesis from the coast to the deep-sea along the western South-Atlantic passive continental margin. During RV Meteor Cruise M78/3 in May-July 2009 the shelf, slope and rise offshore Argentina and Uruguay have been investigated by means of hydroacoustic and seismic mapping as well as geological sampling with conventional coring tools as well as the new MARUM seafloor drill rig (MeBo) that revealed recovery of geological strata sampled from up to 50m below seafloor. The working area is characterized by a high amount of fluvial input by the Rio de la Plata river. The continental slope is relatively wide and shows average slope gradients between 1 and 2.5 but locally higher slope gradients may occur (>5). The transition for the continental rise with low slope gradients is found in ~ 3000m water depth. The working area is located in a highly dynamic oceanographic regime. Cold Antarctic water masses of the northward flowing Malvina current meet warm water masses of the southward flowing Brazil current in the working area. Various types of sediment instabilities have been imaged in geophysical and core data, documenting particularly the continental slope offshore Uruguay to be locus of frequent submarine landslides. Apart from individual landslides, however, gravitational downslope sediment transport along the continental slope is restricted to the prominent Mar del Plata Canyon and possibly to smaller canyons indentified in the bathymetric data. The location of the canyons might be controlled by tectonics. In contrast, many morphological features (e.g. progradational terraces and slope parallel scarps with scour-geometries) reveal that sediment transport is predominantly influenced/controlled by strong contour bottom currents. This suggests a significant impact of the western boundary currents on the overall architectural evolution of the margin. Future studies using the acquired geophysical, sedimentological, physical property and geochemical data will (i) quantify the relative contribution of gravitational down-slope vs. along-slope processes through time in shaping this ocean margin and how it relates to the global ocean circulation pattern and sea-level change through time, (ii) investigate depositional and post-depositional processes and how they control submarine slope stability and submarine landslide initiation and (iii) explore the interaction and relative contribution of the various processes in controlling margin evolution, sediment dynamics and geohazard off Uruguay and Northern Argentina.

Dynamics of hydrocarbon vents: Focus on primary porosity

NASA Astrophysics Data System (ADS)

Johansen, C.; Shedd, W.; Abichou, T.; Pineda-Garcia, O.; Silva, M.; MacDonald, I. R.

2012-12-01

This study investigated the dynamics of hydrocarbon release by monitoring activity of a single vent at a 1215m deep site in the Gulf of Mexico (GC600). An autonomous camera, deployed by the submersible ALVIN, was programmed to capture a close-up image every 4 seconds for approximately 3.5 hours. The images provided the ability to study the gas hydrate outcrop site (that measured 5.2x16.3cm3) in an undisturbed state. The outcrop included an array of 38 tube-like vents through which dark brown oil bubbles are released at a rate ranging from 8 bubbles per minute to 0 bubbles per minute. The average release of bubbles from all the separate vents was 59.5 bubbles per minute, equating the total volume released to 106.38cm per minute. The rate of bubble release decreased toward the end of the observation interval, which coincided approximately with the tidal minimum. Ice worms (Hesiocaeca methanicola, Desbruyères & Toulmond, 1998) were abundant at the vent site. The image sequence showed the ice-worms actively moving in and out of burrows in the mound. It has been speculated that Hesiocaeca methanicola contribute to gas hydrate decomposition by creating burrows and depressions in the gas hydrate matrix (Fisher et al, 2000). Ice worm burrows could generate pathways for the passage of oil and gas through the gas hydrate mound. Gas hydrates commonly occur along active and/or passive continental margins (Kennicutt et al, 1988a). The release of oil and gas at this particular hydrocarbon seep site is along a passive continental margin, and controlled primarily by active salt tectonics as opposed to the movement of continental tectonic plates (Salvador, 1987). We propose a descriptive model governing the release of gas and oil from deep sub-bottom reservoirs at depths of 3000-5000m (MacDonald, 1998), through consolidated and unconsolidated sediments, and finally through gas hydrate deposits at the sea floor. The oil and gas escape from the source rock and/or reservoir through at least three degrees of porosity (i.e. traveling through faulted consolidated sediment, unconsolidated sediment, and finally the gas hydrate outcroppings as described here). The oil and gas travel from the sub-bottom reservoir along, what is thought, an interface between the salt and sediment, and then up a fault in the consolidated sediment. When it reaches the unconsolidated sediments, vertical pathways bifurcate due to lack of sediment strength to allow for the oil and gas to reach different clusters of hydrocarbon vents at the sea floor. Hydrocarbon vents are formed and sustained by a combination of pressure, temperature, and gas solubility (Peltzer & Brewer, 2000) creating persistent primary porosity conduits, from which the bubbles escape at different rates depending on the size of the tubes. Previous research has been carried out in order to determine the effect of temperature fluxes on hydrocarbon outcroppings (MacDonald et al, 2005), however, a focus on the dynamics at this level of primary porosity is lacking. By determining the rate and size of bubbles and pore size distribution of the hydrocarbon outcropping, we can explore the hydraulic properties. Therefore, examination of biological and physical effects, such as the role of ice-worms, and the effect of tides, allow for a better understanding of the dynamics and persistency of hydrocarbon vent outcroppings.

Overpressure, Flow Focusing, Compaction and Slope Stability on the continental slope: Insights from IODP Expedition 308

NASA Astrophysics Data System (ADS)

Flemings, P. B.

2010-12-01

Integrated Ocean Drilling Program Expepedition 308 used direct measurements of pore pressure, analysis of hydromechanical properties, and geological analysis to illuminate how sedimentation, flow focusing, overpressure, and slope stability couple beneath the seafloor on the deepwater continental slope in the Gulf of Mexico. We used pore pressure penetrometers to measure severe overpressures (60% of the difference between lithostatic stress and hydrostatic pressure) that extend from the seafloor for 100’s of meters. We ran uniaxial consolidation experiments on whole core and found that although permeability is relatively high near the seafloor, the sediments are highly compressible. As a result, the coefficient of consolidation (the hydraulic diffusivity) is remarkably constant over a large range of effective stresses. This behavior accounts for the high overpressure that begins near the seafloor and extends to depth. Forward modeling suggests that flow is driven laterally along a permeable unit called the Blue Unit. Calculations suggest that soon after deposition, lateral flow lowered the effective stress and triggered the submarine landslides that we observe. Later in the evolution of this system, overpressure may have pre-conditioned the slope to failure by earthquakes. Results from IODP Expedition 308 illustrate how pore pressure and sedimentation control the large-scale form of continental margins, how submarine landslides form, and provide strategies for designing stable drilling programs.

Airborne measurements of total reactive odd nitrogen (NO(y))

NASA Technical Reports Server (NTRS)

Huebler, G.; Fahey, D. W.; Ridley, B. A.; Gregory, G. L.; Fehsenfeld, F. C.

1992-01-01

Airborne total reactive odd nitrogen measurements were made during August and September 1986 over the continental United States and off the west coast over the Pacific Ocean during NASA's Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation 2 program. Measurements were made in the marine and continental boundary layer and the free troposphere up to 6.1 km altitude. NO(y) mixing ratios between 24 pptv and more than 1 ppbv were found, with median values of 101 pptv in the marine boundary layer, 298 pptv in the marine free troposphere, and 288 pptv in the continental free troposphere, respectively. The marine troposphere exhibited layered structure which was also seen in the simultaneously measured ozone mixing ratio and dew point temperature. The averaged vertical NO(y) profile over the ocean does not show a distinct gradient. The NO(y) mixing ratio over the continent decreases with increasing altitude. The latter is consistent with our understanding that the continents are the major source region for these gases.

Research Advances in the Screwworm Eradication Program over the Past 25 Years

USDA-ARS?s Scientific Manuscript database

Screwworms, Cochliomyia hominivorax (Coquerel) (Calliphoridae: Chrysomyinae), are devastating pests of warm blooded animals that cause significant economic damage to livestock. The successful campaign to eradicate screwworms from continental North America using the sterile insect technique, led by t...

What are the Effects of Protest Fear?

DTIC Science & Technology

2014-06-17

Acquisition Professional Development Program AT&L Acquisition, Technology, and Logistics BPA blanket purchase agreement CONUS continental United States...Blanket Purchase Agreement [ BPA ]) in order to avoid a bid protest. The data shows that 88 respondents had done so throughout their career with 4,139

15 CFR 923.53 - Federal consistency procedures.

Code of Federal Regulations, 2011 CFR

2011-01-01

... MANAGEMENT COASTAL ZONE MANAGEMENT PROGRAM REGULATIONS Coordination, Public Involvement and National Interest...); (3) For States anticipating coastal zone effects from Outer Continental Shelf (OCS) activities, the..., which in the opinion of the State agency are likely to significantly affect the coastal zone and thereby...

15 CFR 923.53 - Federal consistency procedures.

Code of Federal Regulations, 2010 CFR

2010-01-01

... MANAGEMENT COASTAL ZONE MANAGEMENT PROGRAM REGULATIONS Coordination, Public Involvement and National Interest...); (3) For States anticipating coastal zone effects from Outer Continental Shelf (OCS) activities, the..., which in the opinion of the State agency are likely to significantly affect the coastal zone and thereby...

The ANGWIN Antarctic Research Program: First Results on Coordinated Trans-Antarctic Gravity Wave Measurements

NASA Astrophysics Data System (ADS)

Taylor, M. J.; Pautet, P. D.; Zhao, Y.; Nakamura, T.; Ejiri, M. K.; Murphy, D. J.; Moffat-Griffin, T.; Kavanagh, A. J.; Takahashi, H.; Wrasse, C. M.

2014-12-01

ANGWIN (ANrctic Gravity Wave Instrument Network) is a new "scientist driven" research program designed to develop and utilize a network of Antarctic atmospheric gravity wave observatories, operated by different nations working together in a spirit of close scientific collaboration. Our research plan has brought together colleagues from several international institutions, all with a common goal to better understand the large "continental-scale" characteristics and impacts of gravity waves on the Mesosphere and Lower Thermosphere (MLT) environment over Antarctica. ANGWIN combines complementary measurements obtained using new and existing aeronomy instrumentation with new modeling capabilities. To date, our activities have focused on developing coordinated airglow image data of gravity waves in the MLT region at the following sites: McMurdo (US), Syowa (Japan), Davis (Australia), Halley (UK), Rothera (UK), and Comandante Ferraz (Brazil). These are all well-established international research stations that are uniformly distributed around the continental perimeter, and together with ongoing measurements at South Pole Station they provide unprecedented coverage of the Antarctic gravity wave field and its variability during the extended polar winter season. This presentation introduces the ANGWIN program and research goals, and presents first results on trans-Antarctic wave propagation using coordinated measurements during the winter season 2011. We also discuss future plans for the development of this exciting program for Antarctic research.

Assessing the carbon consequences of western juniper (Juniperus occidentalis) encroachment across Oregon, USA

Treesearch

John L. Campbell; Robert E. Kennedy; Warren B. Cohen; Richard F. Miller

2012-01-01

Our ability to assess the continental impacts of woody encroachment remains compromised by the paucity of studies quantifying regional encroachment rates. This knowledge gap is especially apparent when it comes to quantifying the impact of woody encroachment on large-scale carbon dynamics. In this study, we use a combination of aerial photography from 1985-1986 and...

Measurement of inter- and intra-annual variability of landscape fire activity at a continental scale: The Australian case

Treesearch

Grant J. Williamson; Lynda D. Prior; Matt Jolly; Mark A. Cochrane; Brett P. Murphy; David M. J. S. Bowman

2016-01-01

Climate dynamics at diurnal, seasonal and inter-annual scales shape global fire activity, although difficulties of assembling reliable fire and meteorological data with sufficient spatio-temporal resolution have frustrated quantification of this variability. Using Australia as a case study, we combine data from 4760 meteorological stations with 12 years of satellite-...

Ecology of snowshoe hares in southern boreal and montane forests [Chapter 7

Treesearch

Karen E. Hodges

2000-01-01

Snowshoe hares occur in many of the montane and sub-boreal forests of the continental United States, as well as throughout the boreal forests of Canada and Alaska. Population dynamics in their southern range were previously thought to be noncyclic, in contrast to the strong 10-year fluctuation that typifies boreal populations of snowshoe hares. Time series data and...

Impacts of increasing drought on forest dynamics, structure, diversity, and management

Treesearch

James S. Clark; Louis Iverson; Christopher W. Woodall

2016-01-01

At the time of this writing in 2015, drought conditions have sustained over much of the continental United States for up to 4 years. Drought, a moisture limitation resulting from below average precipitation, high temperatures, or both, represents a departure from the "mean climate" of a region—and more frequent and severe droughts change this mean climate....

How well do terrestrial biosphere models simulate coarse-scale runoff in the contiguous United States?

Treesearch

C.R. Schwalm; D.N. Huntzinger; R.B. Cook; Y. Wei; I.T. Baker; R.P. Neilson; B. Poulter; Peter Caldwell; G. Sun; H.Q. Tian; N. Zeng

2015-01-01

Significant changes in the water cycle are expected under current global environmental change. Robust assessment of present-day water cycle dynamics at continental to global scales is confounded by shortcomings in the observed record. Modeled assessments also yield conflicting results which are linked to differences in model structure and simulation protocol. Here we...

Mothers' Search for Infant Child Care: The Dynamic Relationship between Availability and Desirability in a Continental European Welfare State

ERIC Educational Resources Information Center

Vandenbroeck, M.; De Visscher, S.; Van Nuffel, K.; Ferla, J.

2008-01-01

The availability, affordability, and desirability of quality child care are matters of concern, especially for children raised in poverty, given the literature showing that young children raised in poverty can benefit from early access to quality care. The unique features of the Brussels context enable us to look at the connection between…

Spatial and Temporal Strain Distribution Along the Central Red Sea Rift - A Study of the Hamd-Jizil Basin in Saudi Arabia

NASA Astrophysics Data System (ADS)

Szymanski, E.; Stockli, D.; Johnson, P.; Kattan, F. H.; Al Shamari, A.

2006-12-01

Numerous models exploring the rupturing modes and mechanisms of continental lithosphere are based on geological evidence from the Red Sea/Gulf of Suez rift system. Individually, the Red Sea basin is the prototype for many models of orthogonal continental rifting. Despite being a classic example of continental extension, many temporal and spatial strain distribution aspects, as well as the dynamic evolution of the rift architecture of the Red Sea, remain poorly constrained. Critical data come mostly from the Gulf of Suez and the Egyptian and Yemeni margins of the Red Sea; the rift flanks in Sudan and Saudi Arabia have remained largely unstudied, leaving a large information gap along the central portions of the rift system. Improving continental lithosphere rupture models requires an absolute understanding of the timing and magnitude of strain partitioning along the full rift flank. This study focuses on the development of extensional structures, syn- extensional sedimentary deposits, and rift-related Tertiary basaltic volcanism along the central flank of the rift system in Saudi Arabia. Geo- and thermochronometric techniques are used to elucidate the evolution of inboard and outboard strain markers manifested by structurally-controlled extensional basins that parallel the trend of the main Red Sea rift. Constraints on the dynamics of rift flank deformation are achieved through the collection of thermochronometric transects that traverse both the entire Arabian shield and individual normal faults that bound inland basins. Preliminary results show inland basins as asymmetric half-grabens filled by tilted Cenozoic sedimentary strata and separated by exhumed basement fault blocks. The most prominent extensional basin is the NW-trending Hamd-Jizil basin, located north of Madinah, measuring ~200 km along strike and up to 20 km in width. The Hamd-Jizil basin is structurally characterized by two half-grabens exposing a series of syn-rift siliciclastic sedimentary sections below Tertiary basalts. In certain areas, thick basalt sequences provide basin infill and appear faulted by a younger series of normal faults. Work continues on the production of further geo- and thermochronologic data for the Tertiary basalt sequences as well as the entire rift flank region.

Phylogenetic Lineages and Postglacial Dispersal Dynamics Characterize the Genetic Structure of the Tick, Ixodes ricinus, in Northwest Europe

PubMed Central

Røed, Knut H.; Kvie, Kjersti S.; Hasle, Gunnar; Gilbert, Lucy; Leinaas, Hans Petter

2016-01-01

Dispersal and gene flow are important mechanisms affecting the dynamics of vectors and their pathogens. Here, patterns of genetic diversity were analyzed in many North European populations of the tick, Ixodes ricinus. Population sites were selected within and between areas separated by geographical barriers in order to evaluate the importance of tick transportation by birds in producing genetic connectivity across open sea and mountain ranges. The phylogenetic analyses of the mitochondrial control region and the cytochrome b gene revealed two distinct clades with supported sub-clades, with three genetic lineages: GB and WNo associated with Great Britain and western Norway respectively, and Eu with a wider distribution across continental Europe in agreement with much lower efficiency of tick dispersal by birds than by large mammals. The results suggest different ancestry of I. ricinus colonizing Britain and the rest of northern Europe, possibly from different glacial refuges, while ticks from western Norway and continental Europe share a more recent common ancestry. Demographic history modeling suggests a period of strong increase in tick abundance coincident with progression of the European Neolithic culture, long after their post-glacial colonization of NW Europe. PMID:27907193

Evolutionary dynamics at high latitudes: speciation and extinction in polar marine faunas

PubMed Central

Clarke, Andrew; Crame, J. Alistair

2010-01-01

Ecologists have long been fascinated by the flora and fauna of extreme environments. Physiological studies have revealed the extent to which lifestyle is constrained by low temperature but there is as yet no consensus on why the diversity of polar assemblages is so much lower than many tropical assemblages. The evolution of marine faunas at high latitudes has been influenced strongly by oceanic cooling during the Cenozoic and the associated onset of continental glaciations. Glaciation eradicated many shallow-water habitats, especially in the Southern Hemisphere, and the cooling has led to widespread extinction in some groups. While environmental conditions at glacial maxima would have been very different from those existing today, fossil evidence indicates that some lineages extend back well into the Cenozoic. Oscillations of the ice-sheet on Milankovitch frequencies will have periodically eradicated and exposed continental shelf habitat, and a full understanding of evolutionary dynamics at high latitude requires better knowledge of the links between the faunas of the shelf, slope and deep-sea. Molecular techniques to produce phylogenies, coupled with further palaeontological work to root these phylogenies in time, will be essential to further progress. PMID:20980314

Quantification of subsurface pore pressure through IODP drilling

NASA Astrophysics Data System (ADS)

Saffer, D. M.; Flemings, P. B.

2010-12-01

It is critical to understand the magnitude and distribution of subsurface pore fluid pressure: it controls effective stress and thus mechanical strength, slope stability, and sediment compaction. Elevated pore pressures also drive fluid flows that serve as agents of mass, solute, and heat fluxes. The Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) have provided important avenues to quantify pore pressure in a range of geologic and tectonic settings. These approaches include 1) analysis of continuous downhole logs and shipboard physical properties data to infer compaction state and in situ pressure and stress, 2) laboratory consolidation testing of core samples collected by drilling, 3) direct downhole measurements using pore pressure probes, 3) pore pressure and stress measurements using downhole tools that can be deployed in wide diameter pipe recently acquired for riser drilling, and 4) long-term monitoring of formation pore pressure in sealed boreholes within hydraulically isolated intervals. Here, we summarize key advances in quantification of subsurface pore pressure rooted in scientific drilling, highlighting with examples from subduction zones, the Gulf of Mexico, and the New Jersey continental shelf. At the Nankai, Costa Rican, and Barbados subduction zones, consolidation testing of cores samples, combined with analysis of physical properties data, indicates that even within a few km landward of the trench, pore pressures in and below plate boundary décollement zones reach a significant fraction of the lithostatic load (λ*=0.25-0.91). These results document a viable and quantifiable mechanism to explain the mechanical weakness of subduction décollements, and are corroborated by a small number of direct measurements in sealed boreholes and by inferences from seismic reflection data. Recent downhole measurements conducted during riser drilling using the modular formation dynamics tester wireline tool (MDT) in a forearc basin ~50 km from the trench document hydrostatic pore pressures in the basin fill down to ~1500 mbsf, and illustrate a promising technique for obtaining pore pressure and stress magnitude. In the Gulf of Mexico, we used pore pressure penetrometers to measure severe overpressures (λ*=0.7); a comprehensive program of consolidation testing on recovered core samples confirms elevated pore pressures due to rapid sedimentation, reflecting disequilibrium compaction. Similarly, along the New Jersey continental shelf, analysis of porosity data from downhole logs and augmented by geotechnical testing of cores demonstrates elevated pore pressures in the shallow subsurface. In both offshore New Jersey and the Gulf of Mexico, integration of direct measurements, geotechnical testing, and hydrodynamic modeling illustrate how flow is focused along permeable layers to reduce effective stress and drive submarine landslides. In sum, pore pressure observations made through the ODP and IODP provide insight into how pore pressure controls the large-scale form of passive and active continental margins, how submarine landslides form, and provide strategies for engineering deep boreholes.

Transport processes near coastal ocean outfalls

USGS Publications Warehouse

Noble, M.A.; Sherwood, C.R.; Lee, Hooi-Ling; Xu, Jie; Dartnell, P.; Robertson, G.; Martini, M.

2001-01-01

The central Southern California Bight is an urbanized coastal ocean where complex topography and largescale atmospheric and oceanographic forcing has led to numerous sediment-distribution patterns. Two large embayments, Santa Monica and San Pedro Bays, are connected by the short, very narrow shelf off the Palos Verdes peninsula. Ocean-sewage outfalls are located in the middle of Santa Monica Bay, on the Palos Verdes shelf and at the southeastern edge of San Pedro Bay. In 1992, the US Geological Survey, together with allied agencies, began a series of programs to determine the dominant processes that transport sediment and associated pollutants near the three ocean outfalls. As part of these programs, arrays of instrumented moorings that monitor currents, waves, water clarity, water density and collect resuspended materials were deployed on the continental shelf and slope information was also collected on the sediment and contaminant distributions in the region. The data and models developed for the Palos Verdes shelf suggest that the large reservoir of DDT/DDE in the coastal ocean sediments will continue to be exhumed and transported along the shelf for a long time. On the Santa Monica shelf, very large internal waves, or bores, are generated at the shelf break. The near-bottom currents associated with these waves sweep sediments and the associated contaminants from the shelf onto the continental slope. A new program underway on the San Pedro shelf will determine if water and contaminants from a nearby ocean outfall are transported to the local beaches by coastal ocean processes. The large variety of processes found that transport sediments and contaminants in this small region of the continental margin suggest that in regions with complex topography, local processes change markedly over small spatial scales. One cannot necessarily infer that the dominant transport processes will be similar even in adjacent regions.

Analysis of Dynamics in Bays and Coastal Waters Impacted by Hurricanes

NASA Astrophysics Data System (ADS)

Li, C.; Lin, H.; Chen, C.

2012-12-01

The dynamical processes in coastal bays/estuaries and continental shelf are mostly tidally and wind driven. Under severe weather conditions such as hurricanes and tropical storms, the process is much more dynamic and variable. In an attempt to illustrate the dynamical regimes in coastal bays and adjacent coastal ocean, we have simulated circulation and storm tides in the northern Gulf of Mexico forced by 49 hurricanes, respectively; among which 4 are the most recent real hurricanes: Hurricane Katrina and Hurricane Rita of 2005, and Hurricane Gustav and Hurricane Ike of 2008. The other 45 hurricanes are hypothetical in their tracks, but based on the real hurricanes in terms of forcing conditions. More specifically, these 45 hurricanes are divided into five groups, each corresponding to one of these four real hurricanes plus a group for hypothetical Category 5 hurricanes, based on the information of Hurricane Katrina, except that the strength of the hurricane is increased to Category 5. Using otherwise the same forcing conditions of the hurricanes, we apply variations of each of the hurricane tracks with roughly the same moving speed. Each group has a total of 9 simulations (with 9 different tracks). Our model allows inundation of wetland, and low lying lands on the coast and around the Louisiana Bays. The model for the hurricane storm tide was done with an implementation of the Finite Volume Coastal Ocean Model, or FVCOM. Our analysis of the results reveals rich dynamical processes in the bays and estuaries and on the adjacent continental shelf. It involves various oscillations, depending on the hurricane conditions and track history and positions, long waves, under the influence of earth rotation, and currents. The protruding delta, bathymetry, and the setup of the bays all play some roles in shaping the dynamics, water movement, inundation, and receding of the storm surges.

Sea ice and oceanic processes on the Ross Sea continental shelf

NASA Astrophysics Data System (ADS)

Jacobs, S. S.; Comiso, J. C.

1989-12-01

We have investigated the spatial and temporal variability of Antarctic sea ice concentrations on the Ross Sea continental shelf, in relation to oceanic and atmospheric forcing. Sea ice data were derived from Nimbus 7 scanning multichannel microwave radiometer (SMMR) brightness temperatures from 1979-1986. Ice cover over the shelf was persistently lower than above the adjacent deep ocean, averaging 86% during winter with little month-to-month or interannual variability. The large spring Ross Sea polynya on the western shelf results in a longer period of summer insolation, greater surface layer heat storage, and later ice formation in that region the following autumn. Newly identified Pennell and Ross Passage polynyas near the continental shelf break appear to be maintained in part by divergence above a submarine bank and by upwelling of warmer water near the slope front. Warmer subsurface water enters the shelf region year-round and will retard ice growth and enhance heat flux to the atmosphere when entrained in the strong winter vertical circulation. Temperatures at 125-m depth on a mooring near the Ross Ice Shelf during July 1984 averaged 0.15°C above freezing, sufficient to support a vertical heat flux above 100 W/m2. Monthly average subsurface ocean temperatures along the Ross Ice Shelf lag the air temperature cycle and begin to rise several weeks before spring ice breakout. The coarse SMMR resolution and dynamic ice shelf coastlines can compromise the use of microwave sea ice data near continental boundaries.

Physical oceanography of continental shelves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, J.S.; Beardlsey, R.C.; Blanton, J.O.

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 studiesmore » 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.« less

The composition and structure of volcanic rifted continental margins in the North Atlantic: Further insight from shear waves

NASA Astrophysics Data System (ADS)

Eccles, Jennifer D.; White, Robert S.; Christie, Philip A. F.

2011-07-01

Imaging challenges caused by highly attenuative flood basalt sequences have resulted in the understanding of volcanic rifted continental margins lagging behind that of non-volcanic rifted and convergent margins. Massive volcanism occurred during break-up at 70% of the passive margins bordering the Atlantic Ocean, the causes and dynamics of which are still debated. This paper shows results from traveltime tomography of compressional and converted shear wave arrivals recorded on 170 four-component ocean bottom seismometers along two North Atlantic continental margin profiles. This traveltime tomography was performed using two different approaches. The first, a flexible layer-based parameterisation, enables the quality control of traveltime picks and investigation of the crustal structure. The second, with a regularised grid-based parameterisation, requires correction of converted shear wave traveltimes to effective symmetric raypaths and allows exploration of the model space via Monte Carlo analyses. The velocity models indicate high lower-crustal velocities and sharp transitions in both velocity and Vp/Vs ratios across the continent-ocean transition. The velocities are consistent with established mixing trends between felsic continental crust and high magnesium mafic rock on both margins. Interpretation of the high quality seismic reflection profile on the Faroes margin confirms that this mixing is through crustal intrusion. Converted shear wave data also provide constraints on the sub-basalt lithology on the Faroes margin, which is interpreted as a pre-break-up Mesozoic to Paleocene sedimentary system intruded by sills.

Counter-intuitive features of the dynamic topography unveiled by tectonically realistic 3D numerical models of mantle-lithosphere interactions

NASA Astrophysics Data System (ADS)

Burov, Evgueni; Gerya, Taras

2013-04-01

It has been long assumed that the dynamic topography associated with mantle-lithosphere interactions should be characterized by long-wavelength features (> 1000 km) correlating with morphology of mantle flow and expanding beyond the scale of tectonic processes. For example, debates on the existence of mantle plumes largely originate from interpretations of expected signatures of plume-induced topography that are compared to the predictions of analytical and numerical models of plume- or mantle-lithosphere interactions (MLI). Yet, most of the large-scale models treat the lithosphere as a homogeneous stagnant layer. We show that in continents, the dynamic topography is strongly affected by rheological properties and layered structure of the lithosphere. For that we reconcile mantle- and tectonic-scale models by introducing a tectonically realistic continental plate model in 3D large-scale plume-mantle-lithosphere interaction context. This model accounts for stratified structure of continental lithosphere, ductile and frictional (Mohr-Coulomb) plastic properties and thermodynamically consistent density variations. The experiments reveal a number of important differences from the predictions of the conventional models. In particular, plate bending, mechanical decoupling of crustal and mantle layers and intra-plate tension-compression instabilities result in transient topographic signatures such as alternating small-scale surface features that could be misinterpreted in terms of regional tectonics. Actually thick ductile lower crustal layer absorbs most of the "direct" dynamic topography and the features produced at surface are mostly controlled by the mechanical instabilities in the upper and intermediate crustal layers produced by MLI-induced shear and bending at Moho and LAB. Moreover, the 3D models predict anisotropic response of the lithosphere even in case of isotropic solicitations by axisymmetric mantle upwellings such as plumes. In particular, in presence of small (i.e. insufficient to produce solely any significant deformation) uniaxial extensional tectonic stress field, the plume-produced surface and LAB features have anisotropic linear shapes perpendicular to the far-field tectonic forces, typical for continental rifts. Compressional field results in singular sub-linear folds above the plume head, perpendicular to the direction of compression. Small bi-axial tectonic stress fields (compression in one direction and extension in the orthogonal direction) result in oblique, almost linear segmented normal or inverse faults with strike-slip components (or visa verse , strike-slip faults with normal or inverse components)

The initiation and tectonic regimes of the Cenozoic extension in the Bohai Bay Basin, North China revealed by numerical modelling

NASA Astrophysics Data System (ADS)

Li, Lu; Qiu, Nansheng

2017-06-01

In this study the dynamic aspects of the Cenozoic extension in the Bohai Bay Basin are considered in the context of initial thickness of the crust and lithosphere, tectonic force, strain rate and thermal rheology, which are directly or indirectly estimated from a pure shear extensional model. It is accordingly reasonable to expect that, in the Bohai Bay Basin, the thickness variation could be present prior to the initiation of extension. The extensional deformation is localized by a thickness variation of the crust and lithosphere and the heterogeneity of the initial thickness plays an important role in rifting dynamics. The onset of rifting requires a critical tectonic force (initial tectonic force) to be applied, which then immediately begins to decay gradually. Rifting will only occur when the total effective buoyancy force of the subducting slab reaches a critical level, after a certain amount of subduction taking place. The magnitude of the tectonic force decreases with time in the early phase of rifting, which indicates the weakening due to the increase in geothermal gradient. In order to deform the continental lithosphere within the currently accepted maximum magnitude of the force derived from subducted slab roll-back, the following conditions should be satisfied: (1) the thickness of the continental lithosphere is significantly thin and less than 125 km and (2) the lithosphere has a wet and hot rheology, which provides implications for rheological layering in continental lithosphere. Our results are strongly supported by the ;crème brûlée; model, in which the lower crust and mantle are relatively ductile.

Rhythmic behaviour of marine benthopelagic species and the synchronous dynamics of benthic communities

NASA Astrophysics Data System (ADS)

Aguzzi, Jacopo; Sbragaglia, Valerio; Tecchio, Samuele; Navarro, Joan; Company, Joan B.

2015-01-01

Light-intensity cycles drive the relentless motion of species in the oceans, and water column migrants may cyclically make contact with the seabed, hence influencing the temporal dynamism of benthic ecosystems. The influence of light on this process remains largely unknown to date. In this study, we focus on the occurrence of day-night changes in benthic communities on the western Mediterranean continental shelf (100 m depth) and slope (400 m depth) as a potential result of a behaviourally sustained benthopelagic coupling. We analysed fluctuations in species abundance based on trawling at hourly intervals over a 4-day period as a proxy of activity rhythms at the seabed. We also measured light in situ to assess how the depth-related decrease of its intensity influences species rhythms and the occurrence of the putative benthopelagic synchronisation. Temporal similarities in the catch patterns for different species were screened by dendrogram analysis. On the continental shelf, species performing diel migrations (i.e., over a 24 h period) that were either vertical (i.e., benthopelagic) or horizontal across depths (i.e., nektobenthic) clustered together separately from the more sedentary endobenthic and epibenthic species. At the same depth, waveform analysis showed a significant diurnal increase in the catch of water column species and benthic species at night. Such coupling was absent on the continental slope, where light intensity was several orders of magnitude lower than that on the shelf. Our data indicate that diel activity rhythms, which are well known for vertical pelagic migrators, are also evident in the benthos. We discuss the role of light as a major evolutionary driver shaping the composition and biodiversity of benthic communities via visual predation.

Dynamics and the Wilson Cycle: An EarthScope vision

NASA Astrophysics Data System (ADS)

Ebinger, Cynthia; Humphreys, Eugene; Williams, Michael; van der Lee, Suzan; Levin, Vadim; Webb, Laura; Becker, Thorsten

2017-04-01

Wilson's model has two major components, each with distinctive observables. Initial subduction of ocean lithosphere collides continents across a closing ocean basin, creating a mountain range; rifting then initiates within the collisional orogeny and progresses to create oceanic spreading and creation of a new ocean basin. Subduction eventually initiates near the old, cold, and heavily sedimented continental margin, leading to subduction, and repeating the cycle. This model is largely kinematic in nature, and predictive in application. We re-evaluate the Wilson Cycle in light of process-oriented perspectives afforded by the surface to mantle Earthscope results. Repeating episodes of mountain building by means of continental collisions remains clear, but new observations augment or diverge from Wilson's concepts. A 'new' component stems from observations from both the East and West coasts: translational fault systems played critical roles in continental accretion, collision, and rifting. Earthscope data sets also have enabled imaging of the structure of western U.S. lithosphere with unprecedented detail. From new and existing data sets, we conclude that collision occurs in 'ribbons' in large part linked to the shapes of the landmasses colliding landmasses, and deformation includes a major component of transform tectonics. Post-orogenic gravitational collapse may occur far inboard of the site of collision. A third 'new' feature is that plate coupling with the mantle leads to deformation outside the classic Wilson Cycle. For example, the passive margin of eastern N. America shows tectonic activity, uplift, and magmatism long after the onset of seafloor spreading, demonstrating the dynamic nature of lithosphere-asthenosphere coupling. A 'fourth' observation is that lateral density contrasts and volatile migration during subduction and collision effectively refertilize mantle lithosphere, and pre-condition later tectonic cycles.

Relative Linkages of Chlorophyll-a with the Hydroclimatic and Biogeochemical Variables across the Continental U.S. (CONUS)

NASA Astrophysics Data System (ADS)

Ahmed, M. H.; Abdul-Aziz, O. I.

2017-12-01

Chlorophyll-a (Chl-a) is a key indicator for stream water quality and ecological health. The characterization of interplay between Chl-a and its numerous hydroclimatic and biogeochemical drivers is complex, and often involves multicollinear datasets. A systematic data analytics methodology was employed to determine the relative linkages of stream Chl-a with its dynamic environmental drivers at 50 stream water quality monitoring stations across the continental U.S. Multivariate statistical techniques of principal component analysis (PCA) and factor analysis (FA), in concert with Pearson correlation analysis, were applied to evaluate interrelationships among hydroclimatic, biogeochemical, and biological variables. Power-law based partial least square regression (PLSR) models were developed with a bootstrap Monte Carlo procedure (1000 iterations) to reliably estimate the comparative linkages of Chl-a by resolving multicollinearity in the data matrices (Nash-Sutcliff efficiency = 0.50-87). The data analytics suggested four environmental regimes of stream Chl-a, as dominated by nutrient, climate, redox, and hydro-atmospheric contributions, respectively. Total phosphorous (TP) was the most dominant driver of stream Chl-a in the nutrient controlled regime. Water temperature demonstrated the strongest control of Chl-a in the climate-dominated regime. Furthermore, pH and stream flow were found to be the most important drivers of Chl-a in the redox and hydro-atmospheric component dominated regimes, respectively. The research led to a significant reduction of dimensionality in the large data matrices, providing quantitative and qualitative insights on the dynamics of stream Chl-a. The findings would be useful to manage stream water quality and ecosystem health in the continental U.S. and around the world under a changing climate and environment.

Numerical modeling of continental lithospheric weak zone over plume

NASA Astrophysics Data System (ADS)

Perepechko, Y. V.; Sorokin, K. E.

2011-12-01

The work is devoted to the development of magmatic systems in the continental lithosphere over diffluent mantle plumes. The areas of tension originating over them are accompanied by appearance of fault zones, and the formation of permeable channels, which are distributed magmatic melts. The numerical simulation of the dynamics of deformation fields in the lithosphere due to convection currents in the upper mantle, and the formation of weakened zones that extend up to the upper crust and create the necessary conditions for the formation of intermediate magma chambers has been carried out. Thermodynamically consistent non-isothermal model simulates the processes of heat and mass transfer of a wide class of magmatic systems, as well as the process of strain localization in the lithosphere and their influence on the formation of high permeability zones in the lower crust. The substance of the lithosphere is a rheologic heterophase medium, which is described by a two-velocity hydrodynamics. This makes it possible to take into account the process of penetration of the melt from the asthenosphere into the weakened zone. The energy dissipation occurs mainly due to interfacial friction and inelastic relaxation of shear stresses. The results of calculation reveal a nonlinear process of the formation of porous channels and demonstrate the diversity of emerging dissipative structures which are determined by properties of both heterogeneous lithosphere and overlying crust. Mutual effect of a permeable channel and the corresponding filtration process of the melt on the mantle convection and the dynamics of the asthenosphere have been studied. The formation of dissipative structures in heterogeneous lithosphere above mantle plumes occurs in accordance with the following scenario: initially, the elastic behavior of heterophase lithosphere leads to the formation of the narrow weakened zone, though sufficiently extensive, with higher porosity. Further, the increase in the width of the weakened area with a small decrease in porosity occurs due to the increase of inelastic stresses. The longitudinal scale of the structure remain unchanged. The evolution of intraplate magmatic systems associated with weakened zones is accompanied by the formation of intermediate intracrustal magma chambers. This work was financially supported by the project #24.1.2, the program of RAS #24.

Evolution of plant growth and defense in a continental introduction.

PubMed

Agrawal, Anurag A; Hastings, Amy P; Bradburd, Gideon S; Woods, Ellen C; Züst, Tobias; Harvey, Jeffrey A; Bukovinszky, Tibor

2015-07-01

Substantial research has addressed adaptation of nonnative biota to novel environments, yet surprisingly little work has integrated population genetic structure and the mechanisms underlying phenotypic differentiation in ecologically important traits. We report on studies of the common milkweed Asclepias syriaca, which was introduced from North America to Europe over the past 400 years and which lacks most of its specialized herbivores in the introduced range. Using 10 populations from each continent grown in a common environment, we identified several growth and defense traits that have diverged, despite low neutral genetic differentiation between continents. We next developed a Bayesian modeling approach to account for relationships between molecular and phenotypic differences, confirming that continental trait differentiation was greater than expected from neutral genetic differentiation. We found evidence that growth-related traits adaptively diverged within and between continents. Inducible defenses triggered by monarch butterfly herbivory were substantially reduced in European populations, and this reduction in inducibility was concordant with altered phytohormonal dynamics, reduced plant growth, and a trade-off with constitutive investment. Freedom from the community of native and specialized herbivores may have favored constitutive over induced defense. Our replicated analysis of plant growth and defense, including phenotypically plastic traits, suggests adaptive evolution following a continental introduction.

77 FR 57572 - Notice of Arrival on the Outer Continental Shelf

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-18

... program currently requires NOA information for those vessels, facilities, and Mobile Offshore Drilling... Lendvay, Commercial Vessel Compliance, Foreign and Offshore Vessel Compliance Division (CG-CVC-2), U.S... 2254), which required NOA information for those vessels, facilities and Mobile Drilling Units (MODUs...

Fish tissue contamination in the mid-continental great rivers of the United States

EPA Science Inventory

The great rivers of the central United States (Upper Mississippi, Missouri and Ohio rivers) are significant economic and cultural resources, but their ecological condition is not well quantified. The Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP...

Best Practices & Outstanding Initiatives

ERIC Educational Resources Information Center

Training, 2011

2011-01-01

In this article, "Training" editors recognize innovative and successful learning and development programs and practices. They share best practices from Automatic Data Processing, Inc., Farmers Insurance Group, FedEx Express, InterContinental Hotels Group, and Oakwood Temporary Housing. They also present the outstanding initiatives of EMD Serono,…

Stress Field in Brazil with Focal Mechanism: Regional and Local Patterns

NASA Astrophysics Data System (ADS)

Dias, F.; Assumpcao, M.

2013-05-01

The knowledge of stress field is fundamental not only to understand driving forces and plate deformation but also in the study of intraplate seismicity. The stress field in Brazil has been determined mainly using focal mechanisms and a few breakout data and in-situ measurements. However the stress field still is poorly known in Brazil. The focal mechanisms of recent earthquakes (magnitude lower than 5 mb) were studied using waveform modeling. We stacked the record of several teleseismic stations ( delta > 30°) stacked groups of stations separated according to distance and azimuth. Every record was visually inspected and those with a good signal/noise ratio (SNR) were grouped in windows of ten degrees distance and stacked. The teleseismic P-wave of the stacked signals was modeled using the hudson96 program of Herrmann seismology package (Herrmann, 2002) and the consistency of focal mechanism with the first-motion was checked. Some events in central Brazil were recorded by closer stations (~ 1000 km) and the moment tensor was determined with the ISOLA code (Sokos & Zahradnik, 2008). With the focal mechanisms available in literature and those obtained in this work, we were able to identify some patterns: the central region shows a purely compressional pattern (E-W SHmax), which is predicted by regional theoretical models (Richardson & Coblentz, 1996 and the TD0 model of Lithgow & Bertelloni, 2004). Meanwhile in the Amazon we find an indication of SHmax oriented in the SE-NW direction, probably caused by the Caribbean plate interaction (Meijer, 1995). In northern coastal region, the compression rotates following the coastline, which indicates an important local component related to spreading effects at the continental/oceanic transition (Assumpção, 1998) and flexural stresses caused by sedimentary load in Amazon Fan. We determine the focal mechanism of several events in Brazil using different techniques according to the available data. The major difficulty is to determine focal mechanism of low magnitudes events (< 5.0 mb) using distant s seismograph stations. We find examples of stress perturbations induced by local effects (e.g. flexure and continental spreading). The results of this work should be useful for future numerical modeling of intraplate stress field. Assumpção,M.,1998.Seismicity and stresses in the Brazilian passive margin. Bull. Seism. Soc. Am., 88(1),160-169. Herrmann, R. B. (2002). Computer programs in seismology, St. Louis University Earthquake Center, St. Louis, Missouri, www.eas.slu .edu/eqc/eqccps.html. Lithgow-Bertelloni, C., & J.H. Guynn, 2004. Origin of the lithospheric stress field. J. Geophys. Res., 109, B01408, doi:10.1029/2003JB002467. Meijer, P.T., 1995. Dynamics of active continental margins: the Andes and the Aegean regions. PhD Thesis, Utrecht University, The Netherlands. Sokos, E., Zahradnik, J., (2008). ISOLA a Fortran code and a Matlab GUI to perform multiple-point source inversion of seismic data, Computers and Geosciences, 34, 967-97. Watts, A. B., M. Rodger, C. Peirce, C. J. Greenroyd, and R. W. Hobbs (2009). Seismic structure, gravity anomalies, and flexure of the Amazon continental margin, NE Brazil, J. Geophys. Res., 114, B07103, doi:10.1029/2008JB006259.

Cross-continental comparison of the functional composition and carbon allocation of two altitudinal forest transects in Ecuador and Rwanda.

NASA Astrophysics Data System (ADS)

Bauters, Marijn; Bruneel, Stijn; Demol, Miro; Taveirne, Cys; Van Der Heyden, Dries; Boeckx, Pascal; Kearsley, Elizabeth; Cizungu, Landry; Verbeeck, Hans

2016-04-01

Tropical forests are key actors in the global carbon cycle. Predicting future responses of these forests to global change is challenging, but important for global climate models. However, our current understanding of such responses is limited, due to the complexity of forest ecosystems and the slow dynamics that inherently form these systems. Our understanding of ecosystem ecology and functioning could greatly benefit from experimental setups including strong environmental gradients in the tropics, as found on altitudinal transects. We setup two such transects in both South-America and Africa, focussing on shifts in carbon allocation, forest structure and functional composition. By a cross-continental comparison of both transects, we will gain insight in how different or alike both tropical forests biomes are in their responses, and how universal the observed adaption mechanisms are.

Clay mineral continental amplifier for marine carbon sequestration in a greenhouse ocean.

PubMed

Kennedy, Martin J; Wagner, Thomas

2011-06-14

The majority of carbon sequestration at the Earth's surface occurs in marine continental margin settings within fine-grained sediments whose mineral properties are a function of continental climatic conditions. We report very high mineral surface area (MSA) values of 300 and 570 m(2) g in Late Cretaceous black shales from Ocean Drilling Program site 959 of the Deep Ivorian Basin that vary on subcentennial time scales corresponding with abrupt increases from approximately 3 to approximately 18% total organic carbon (TOC). The observed MSA changes with TOC across multiple scales of variability and on a sample-by-sample basis (centimeter scale), provides a rigorous test of a hypothesized influence on organic carbon burial by detrital clay mineral controlled MSA. Changes in TOC also correspond with geochemical and sedimentological evidence for water column anoxia. Bioturbated intervals show a lower organic carbon loading on mineral surface area of 0.1 mg-OC m(-2) when compared to 0.4 mg-OC m(-2) for laminated and sulfidic sediments. Although either anoxia or mineral surface protection may be capable of producing TOC of < 5%, when brought together they produced the very high TOC (10-18%) apparent in these sediments. This nonlinear response in carbon burial resulted from minor precession-driven changes of continental climate influencing clay mineral properties and runoff from the African continent. This study identifies a previously unrecognized land-sea connection among continental weathering, clay mineral production, and anoxia and a nonlinear effect on marine carbon sequestration during the Coniacian-Santonian Oceanic Anoxic Event 3 in the tropical eastern Atlantic.

From Caprio's lilacs to the USA National Phenology Network

USGS Publications Warehouse

Schwartz, Mark D.; Betancourt, Julio L.; Weltzin, Jake F.

2012-01-01

Continental-scale monitoring is vital for understanding and adapting to temporal changes in seasonal climate and associated phenological responses. The success of monitoring programs will depend on recruiting, retaining, and managing members of the public to routinely collect phenological observations according to standardized protocols. Here, we trace the development of infrastructure for phenological monitoring in the US, culminating in the USA National Phenology Network, a program that engages scientists and volunteers.

Extreme mass flux from the glaciated, collisional St. Elias Orogen: Preliminary results from IODP Expedition 341 (Invited)

NASA Astrophysics Data System (ADS)

Gulick, S. P.; Jaeger, J. M.

2013-12-01

Integrated Ocean Drilling Program Expedition 341 drilled a cross-margin transect to investigate the linkages between global climate change, modification of the dynamics of surficial processes, and subsequent tectonic responses. The Gulf of Alaska (GoA) borders the St. Elias orogen, the highest coastal mountain range on Earth. Exp. 341 drilled five sites within a regional seismic reflection grid that spans from the distal Surveyor Fan to the continental shelf. More than 3000 m of high-quality core coupled with seismic reflection profiles collected with nested vertical resolution allows us to address the major objectives of drilling in the GoA. These objectives were to: 1) document the tectonic response of an active orogenic system to late Miocene to recent climate change; 2) establish the timing of advance/retreat phases of the northern Cordilleran ice sheet to test its relation to dynamics of other global ice sheets; 3) implement an expanded source-to-sink study of the interactions between glacial, tectonic, and oceanographic processes responsible for creation of one of the thickest Neogene high-latitude continental margin sequences; 4) understand the dynamics of productivity, nutrients, freshwater input to the ocean, and ocean circulation in the northeast Pacific and their role in the global carbon cycle, and 5) document the spatial and temporal behavior of the geomagnetic field at extremely high temporal resolution in an under-sampled region of the globe. The Exp. 341 cross-margin transect discovered transitions in sediment accumulation rates from >100 m/Ma at the distal site to > 1000 m/Ma in the proximal fan, slope and on the continental shelf that provide a telescoping view of strata formation from the Miocene to the Holocene. Complete recovery and development of spliced sedimentary records of the Pleistocene through Holocene were achieved at the distal, proximal, and slope Sites U1417, U1418, and U1419, respectively, because of exceptional piston core recovery coupled with real-time stratigraphic correlation. The 800-m deep U1417 records Miocene to Recent deposition in the distal Surveyor Fan including the onset of glaciation at the Plio-Pleistocene boundary when accumulation rates doubled to ~100 m/Myr. Site U1418 contains an expanded middle to late Pleistocene sedimentary record that also includes significant increases in sediment accumulation from ~400 m/Myr in the middle Pleistocene to >1200 m/Myr in the late Pleistocene. Slope Site U1421 and shelf Site U1420, proximal to or overridden by the Bering Glacier during glaciations, provided cores penetrating thick sequences of poorly sorted, glacigenic sediments ranging from mud to boulders. All five sites include the middle Pleistocene to Holocene and demonstrate exceptional accumulation rates. The sediments are dominantly glacigenic while containing evidence for direct interaction of tectonic and glacial erosion and sedimentation. Glacial ice, glacigenic sediment routing and glacial extents are driven by tectonic morphology at the orogen and individual thrust-sheet scales. Sediment accumulation, tempered by accommodation, perturbs fault patterns and drives positive feedback within the orogen to produce an extreme example of mass flux from orogen to deep-sea.

Submarine landslides along the eastern Mediterranean Israeli continental slope - a possible source for tsunami

NASA Astrophysics Data System (ADS)

Katz, O.; Reuven, E.; Aharonov, E.

2013-12-01

Numerous shallow submarine slope failures (scars and deposits) are observed in recent high resolution bathymetric grids of the continental slope off the Israeli eastern Mediterranean coast. The nature of these slope failures is currently not comprehensively understood as well as the question of whether the eastern Mediterranean continental slope is continuously or episodically unstable. This question is relevant to tsunami hazard along the densely populated eastern Mediterranean shores. We report here first steps towards understanding the present state of this submarine landslide system, which include mapping and analyzing the geology of the landslides and the hosting slopes. The continental slope extends from water depths of about 150 to more than 1000 meters with a slope of less than 5 degrees in general. Bathymetric grids with pixel resolution of 15 m till water depth of 700 m and 50 m till water depth of 1700 m were used. Analyzing the bathymetry revealed three main submarine surface features on the continental slope: (a) numerous shallow landslides, within the upper sequence of the post-Messenian sediments. Landslide widths range between hundreds to thousand of meters at the scar, with scar heights up to hundred meters. The toes of the landslides are not always mapable and lay up to a few kilometers down slope from the scar. Slope angles within the scars are 5 degrees to more than 15 degrees. In general landslides size decreases from south to north where their head scar depth turns to be shallower northwards. At least two types of landslides were detected: presumably young slides with sharp scars and presumably old slides with secondary slides and secondary drainage systems developed within the scar area; (b) a few kilometers long, north striking step-like lineaments. Step heights are up to 100 meters and the slopes are up to 20 degrees. The offset between parallel steps is less than a kilometer to a few kilometers. Analyzing seismic lines, the steps are interpreted as surface expressions of growth faults rooted at the Messinian evaporates up to 1.5 kilometers below surface; (c) a few north striking channels were also detected with steep walls of more than 15 degrees, up to two kilometers width and a few kilometers length. The nature of these channels is not clear yet although apparently they are also a surface expressions of the growth faults rooted at the Messinian evaporates. Field relations show that the landslides, both young and old, either emerge from the over-steepened steps, or are displaced by them, and hence submarine landslides and steps are apparently contemporaneous. In addition this suggests that salt dynamics at depth is a main drive for at least some of these shallow slides. The above preliminary results testify to the complicated and highly dynamic nature of the studied continental slope, yet to be revealed.

40 CFR 71.2 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... control agency for the area in which a part 71 permit, permit modification, or permit renewal is being... requirement of the program to control air pollution from outer continental shelf sources, under section 328 of... particular change. Delegate agency means the State air pollution control agency, local agency, other State...

40 CFR 71.2 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... control agency for the area in which a part 71 permit, permit modification, or permit renewal is being... requirement of the program to control air pollution from outer continental shelf sources, under section 328 of... particular change. Delegate agency means the State air pollution control agency, local agency, other State...

40 CFR 71.2 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... control agency for the area in which a part 71 permit, permit modification, or permit renewal is being... requirement of the program to control air pollution from outer continental shelf sources, under section 328 of... particular change. Delegate agency means the State air pollution control agency, local agency, other State...

77 FR 39508 - Commercial Wind Lease Issuance and Site Assessment Activities on the Atlantic Outer Continental...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-03

... public of the availability of the EA for review and to solicit public comments on the EA. The EA can be found online at http://www.boem.gov/Renewable-Energy-Program/Smart-from-the-Start/Index.aspx . Authority...

Persistent organic pollutants in fish tissue in the mid-continental great rivers of the United States

EPA Science Inventory

The great rivers of the central United States (Upper Mississippi, Missouri, and Ohio rivers) are significant economic and cultural resources, but their ecological condition is not well quantified. The Environmental Monitoring and Assessment Program for Great River Ecosystems (EMA...

Topographic asymmetry of the South Atlantic from global models of mantle flow and lithospheric stretching

NASA Astrophysics Data System (ADS)

Flament, Nicolas; Gurnis, Michael; Williams, Simon; Seton, Maria; Skogseid, Jakob; Heine, Christian; Dietmar Müller, R.

2014-02-01

The relief of the South Atlantic is characterized by elevated passive continental margins along southern Africa and eastern Brazil, and by the bathymetric asymmetry of the southern oceanic basin where the western flank is much deeper than the eastern flank. We investigate the origin of these topographic features in the present and over time since the Jurassic with a model of global mantle flow and lithospheric deformation. The model progressively assimilates plate kinematics, plate boundaries and lithospheric age derived from global tectonic reconstructions with deforming plates, and predicts the evolution of mantle temperature, continental crustal thickness, long-wavelength dynamic topography, and isostatic topography. Mantle viscosity and the kinematics of the opening of the South Atlantic are adjustable parameters in thirteen model cases. Model predictions are compared to observables both for the present-day and in the past. Present-day predictions are compared to topography, mantle tomography, and an estimate of residual topography. Predictions for the past are compared to tectonic subsidence from backstripped borehole data along the South American passive margin, and to dynamic uplift as constrained by thermochronology in southern Africa. Comparison between model predictions and observations suggests that the first-order features of the topography of the South Atlantic are due to long-wavelength dynamic topography, rather than to asthenospheric processes. The uplift of southern Africa is best reproduced with a lower mantle that is at least 40 times more viscous than the upper mantle.

Topographic asymmetry of the South Atlantic from global models of mantle flow and lithospheric stretching

NASA Astrophysics Data System (ADS)

Flament, Nicolas; Gurnis, Michael; Williams, Simon; Seton, Maria; Skogseid, Jakob; Heine, Christian; Müller, Dietmar

2014-05-01

The relief of the South Atlantic is characterized by elevated passive continental margins along southern Africa and eastern Brazil, and by the bathymetric asymmetry of the southern oceanic basin where the western flank is much deeper than the eastern flank. We investigate the origin of these topographic features in the present and over time since the Jurassic with a model of global mantle flow and lithospheric deformation. The model progressively assimilates plate kinematics, plate boundaries and lithospheric age derived from global tectonic reconstructions with deforming plates, and predicts the evolution of mantle temperature, continental crustal thickness, long-wavelength dynamic topography, and isostatic topography. Mantle viscosity and the kinematics of the opening of the South Atlantic are adjustable parameters in multiple model cases. Model predictions are compared to observables both for the present-day and in the past. Present-day predictions are compared to topography, mantle tomography, and an estimate of residual topography. Predictions for the past are compared to tectonic subsidence from backstripped borehole data along the South American passive margin, and to dynamic uplift as constrained by thermochronology in southern Africa. Comparison between model predictions and observations suggests that the first-order features of the topography of the South Atlantic are due to long-wavelength dynamic topography, rather than to asthenospheric processes. We find the uplift of southern Africa to be best reproduced with a lower mantle that is at least 40 times more viscous than the upper mantle.

Trend and dynamic cause of sediment particle size on the adjacent continental shelf of the Yangtze Estuary

NASA Astrophysics Data System (ADS)

Yang, Yun-ping; Zhang, Ming-jin; Li, Yi-tian; Fan, Yong-yang

2016-12-01

Based on the measured data in recent 20 years, the variation trends of the median grain size of the surface sediment, the sand-silt boundary and the mud area on the adjacent continental shelf of the Yangtze Estuary were analyzed in depth, and the effects of natural mechanism and human activities were discussed. The results show that: (1) In recent years (2006-2013), the median grain size of sediment and the distribution pattern of grouped sediments in the adjacent continental shelf area to the Yangtze Estuary have presented no obvious change compared with those before 2006; (2) The median diameter of the surface sediment in the continental shelf area displayed a coarsening trend with the decrease of sediment discharge from the basin and the drop in suspended sediment concentration in the shore area; (3) In 2004-2007, the sand-silt boundary in the north part (31°30'N) of the continental shelf area presented no significant changes, while that in the south part (31°30'S) moved inwards; In 2008-2013, both the sand-silt boundaries in the north and south parts of the continental shelf area moved inwards, mainly due to the fact that in the dry season, a relatively enhanced hydrodynamic force of the tides was generated in the Yangtze River, as well as a decreased suspended sediment concentration and a flow along the banks in North Jiangsu; (4) The mud area where the maximum deposition rate is found in the Yangtze Estuary, tends to shrink due to the drop in sediment discharge from the basin, and the decrease in suspended sediment concentration in the shore area and erosion in the delta. Moreover, it tended to shift to the south at the same time because the implement of the training works on the deep-water channel of the North Passage changed the split ratio between the North and South Passages with an increase in the power of the discharged runoff in the South Passage.

Dynamics of dissolved organic carbon in a stream during a quarter century of forest succession

Treesearch

Judy L. Meyer; Jackson Webster; Jennifer Knoepp; E.F. Benfield

2014-01-01

Dissolved organic carbon (DOC) is a heterogeneous mixture of compounds that makes up a large fraction of the organic matter transported in streams. It plays a significant role in many ecosystems. Riverine DOC links organic carbon cycles of continental and oceanic ecosystems. It is a significant trophic resource in stream food webs. DOC imparts color to lakes,...

Tectonics of the central Andes

NASA Technical Reports Server (NTRS)

Bloom, Arthur L.; Isacks, Bryan L.; Fielding, Eric J.; Fox, Andrew N.; Gubbels, Timothy L.

1989-01-01

Acquisition of nearly complete coverage of Thematic Mapper data for the central Andes between about 15 to 34 degrees S has stimulated a comprehensive and unprecedented study of the interaction of tectonics and climate in a young and actively developing major continental mountain belt. The current state of the synoptic mapping of key physiographic, tectonic, and climatic indicators of the dynamics of the mountain/climate system are briefly reviewed.

Tidal Dynamics and Mixing Over Steep Topography

DTIC Science & Technology

1994-06-01

California continental shelf have been observed at several locations (Huthnance, 1989). Shea and Broenkow (1982) observed large 33 tidally related...enhanced transport inside the canyon (Huthnance, 1989). This type of pressure gradient supports the conceptual model proposed by Shea and Broenkow (1982...predicted an enhanced internal tide up-canyon and near the bottom, verified by observations of strong internal tides by Shea and Broenkow (1982) at

Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea

USGS Publications Warehouse

Gardner, J.V.; Dean, W.E.; Vallier, T.L.

1980-01-01

Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian Islands and the outer continental shelf and slope, indicates that Holocene sediment dynamics cannot be used to explain the observed distribution of surface sediment derived from the Aleutian Islands. We suggest that this pattern is relict and resulted from sediment dynamics during lower sea levels of the Pleistocene. ?? 1980.

Computer modeling of large asteroid impacts into continental and oceanic sites: Atmospheric, cratering, and ejecta dynamics

NASA Technical Reports Server (NTRS)

Roddy, D. J.; Schuster, S. H.; Rosenblatt, M.; Grant, L. B.; Hassig, P. J.; Kreyenhagen, K. N.

1988-01-01

Numerous impact cratering events have occurred on the Earth during the last several billion years that have seriously affected our planet and its atmosphere. The largest cratering events, which were caused by asteroids and comets with kinetic energies equivalent to tens of millions of megatons of TNT, have distributed substantial quantities of terrestrial and extraterrestrial material over much or all of the Earth. In order to study a large-scale impact event in detail, computer simulations were completed that model the passage of a 10 km-diameter asteroid through the Earth's atmosphere and the subsequent cratering and ejecta dynamics associated with impact of the asteroid into two different targets, i.e., an oceanic site and a continental site. The calcuations were designed to broadly represent giant impact events that have occurred on the Earth since its formation and specifically represent an impact cratering event proposed to have occurred at the end of Cretaceous time. Calculation of the passage of the asteroid through a U.S. Standard Atmosphere showed development of a strong bow shock that expanded radially outward. Behind the shock front was a region of highly shock compressed and intensely heated air. Behind the asteroid, rapid expansion of this shocked air created a large region of very low density that also expanded away from the impact area. Calculations of the cratering events in both the continental and oceanic targets were carried to 120 s. Despite geologic differences, impacts in both targets developed comparable dynamic flow fields, and by approx. 29 s similar-sized transient craters approx. 39 km deep and approx. 62 km across had formed. For all practical purposes, the atmosphere was nearly completely removed from the impact area for tens of seconds, i.e., air pressures were less than fractions of a bar out to ranges of over 50 km. Consequently, much of the asteroid and target materials were ejected upward into a near vacuum. Effects of secondary volcanism and return of the ocean over hot oceanic crater floor could also be expected to add substantial solid and vaporized material to the atmosphere, but these conditions were not studied.

Paleobathymetric grids of the Cenozoic Southern Ocean - Opening the door towards improved reconstructions of the Southern Ocean's past

NASA Astrophysics Data System (ADS)

Hochmuth, K.; Gohl, K.; Leitchenkov, G. L.; Sauermilch, I.; Whittaker, J. M.; De Santis, L.; Olivo, E.; Uenzelmann-Neben, G.; Davy, B. W.

2017-12-01

Although the Southern Ocean plays a fundamental role in the global climate and ocean current system, paleo-ocean circulation models of the Southern Ocean suffer from missing boundary conditions. A more accurate representation of the geometry of the seafloor and their dynamics over long time-scales are key for enabling more precise reconstructions of the development of the paleo-currents, the paleo-environment and the Antarctic ice sheets. The accurate parameterisation of these models controls the meaning and implications of regional and global paleo-climate models. The dynamics of ocean currents in proximity of the continental margins is also controlled by the development of the regional seafloor morphology of the conjugate continental shelves, slopes and rises. The reassessment of all available reflection seismic and borehole data from Antarctica as well as its conjugate margins of Australia, New Zealand, South Africa and South America, allows us to create paleobathymetric grids for various time slices during the Cenozoic. Those grids inform us about sediment distribution and volume as well a local sedimentation rates. The earliest targeted time slice of the Eocene/Oligocene Boundary marks a significant turning point towards an icehouse climate. From latest Eocene to earliest Oligocene the Southern Ocean changes fundamentally from a post greenhouse to an icehouse environment with the establishment of a vast continental ice sheet on the Antarctic continent. With the calculated sediment distribution maps, we can evaluate the dynamics of the sedimentary cover as well as the development of structural obstacles such as oceanic plateaus and ridges. The ultimate aim of this project is - as a community based effort - to create paleobathymetric grids at various time slices such as the Mid-Miocene Climatic Optimum and the Pliocene/Pleistocene, and eventually mimic the time steps used within the modelling community. The observation of sediment distribution and local sediment volumes open the door towards more sophisticated paleo-topograpy studies of the Antarctic continent and more detailed studies of the paleo-circulation. Local paleo - water depths at the oceanic gateways or the position of paleo-shelf edges highly influence the regional circulation patterns supporting more elaborated climate models.

A Systematic Evaluation of Noah-MP in Simulating Land-Atmosphere Energy, Water, and Carbon Exchanges Over the Continental United States

NASA Astrophysics Data System (ADS)

Ma, Ning; Niu, Guo-Yue; Xia, Youlong; Cai, Xitian; Zhang, Yinsheng; Ma, Yaoming; Fang, Yuanhao

2017-11-01

Accurate simulation of energy, water, and carbon fluxes exchanging between the land surface and the atmosphere is beneficial for improving terrestrial ecohydrological and climate predictions. We systematically assessed the Noah land surface model (LSM) with mutiparameterization options (Noah-MP) in simulating these fluxes and associated variations in terrestrial water storage (TWS) and snow cover fraction (SCF) against various reference products over 18 United States Geological Survey two-digital hydrological unit code regions of the continental United States (CONUS). In general, Noah-MP captures better the observed seasonal and interregional variability of net radiation, SCF, and runoff than other variables. With a dynamic vegetation model, it overestimates gross primary productivity by 40% and evapotranspiration (ET) by 22% over the whole CONUS domain; however, with a prescribed climatology of leaf area index, it greatly improves ET simulation with relative bias dropping to 4%. It accurately simulates regional TWS dynamics in most regions except those with large lakes or severely affected by irrigation and/or impoundments. Incorporating the lake water storage variations into the modeled TWS variations largely reduces the TWS simulation bias more obviously over the Great Lakes with model efficiency increasing from 0.18 to 0.76. Noah-MP simulates runoff well in most regions except an obvious overestimation (underestimation) in the Rio Grande and Lower Colorado (New England). Compared with North American Land Data Assimilation System Phase 2 (NLDAS-2) LSMs, Noah-MP shows a better ability to simulate runoff and a comparable skill in simulating Rn but a worse skill in simulating ET over most regions. This study suggests that future model developments should focus on improving the representations of vegetation dynamics, lake water storage dynamics, and human activities including irrigation and impoundments.

Authigenic Carbonate Formation on the Peru Margin; New Insights from IODP Site 1230

NASA Astrophysics Data System (ADS)

Abdullajintakam, S.; Naehr, T. H.

2015-12-01

Fluid seepage of reduced organic compounds such as methane impacts the geology and biology of the seabed by inducing complex, microbially mediated biogeochemical processes. Authigenic carbonates serve as one of the few permanent records of these of dynamic biogeochemical interactions that involve methanogenesis, methanotrophy, sulfate reduction and carbonate precipitation. Meister et al. (2007) investigated deep-sea dolomite formation at Sites 1227-1229 on the Peru margin, where dolomite precipitation occurs in association with organic carbon-rich continental margin sediments. Geochemical and petrographic studies indicated episodic dolomite precipitation at a dynamic sulfate methane transition zone (SMTZ). Variations in δ13C values of these dolomites between +15‰ and -15‰ were attributed to non-steady state conditions as a result of the upward and downward migration of the SMTZ. Our study aims to better understand the biogeochemical processes associated with authigenic carbonate precipitation in this dynamic deep-sea setting. We focused our efforts on IODP Site 1230, which is a gas-hydrate-bearing site that shows sulphate consumption within the uppermost 10 m below the seafloor as well as high methane production. Using a multi proxy approach, we combined X-ray diffraction, stable isotope geochemistry, and trace metal analysis of authigenic carbonates to elucidate conditions for authigenic carbonate formation. Results from Site 1230 are compared to Sites 1227 and 1229, which lacks gas hydrates and is characterized by high pore water sulfate and low methane concentrations. This study contributes to a more comprehensive understanding of authigenic carbonate formation and associated biogeochemical processes in continental margin sediments. Meister, P., Mckenzie, J. A., Vasconcelos, C., Bernasconi, S., Frank, M., Gutjhar, M. and SCHRAG, D. P. (2007), Dolomite formation in the dynamic deep biosphere: results from the Peru Margin. Sedimentology, 54: 1007-1032.

No association between the use of Bti for mosquito control and the dynamics of non-target aquatic invertebrates in French coastal and continental wetlands.

PubMed

Lagadic, Laurent; Schäfer, Ralf B; Roucaute, Marc; Szöcs, Eduard; Chouin, Sébastien; de Maupeou, Jérôme; Duchet, Claire; Franquet, Evelyne; Le Hunsec, Benoit; Bertrand, Céline; Fayolle, Stéphanie; Francés, Benoît; Rozier, Yves; Foussadier, Rémi; Santoni, Jean-Baptiste; Lagneau, Christophe

2016-05-15

The environmental safety of Bacillus thuringiensis subsp. israelensis (Bti) is still controversial, mainly because most of the previous field studies on its undesired effects were spatially limited and did not address the relationship between community similarity and application time and frequency. No general statement can therefore be drawn on the usage conditions of Bti that insure protection of non-target organisms. The present study was conducted in eight sites distributed over the main geographical sectors where mosquito control is implemented in mainland France and Corsica. Changes in non-target aquatic invertebrates were followed at elapsed time after repeated applications of two Bti formulations (VectoBac® WDG or 12AS) up to four consecutive years. We examined the influence of both larvicide treatments and environmental variables on community dynamics and dissimilarity between treated and control areas. As it can be argued that chironomids are the most vulnerable group of non-target invertebrates, we scrutinised potential Bti-related effects on the dynamics of their community. The use of VectoBac® WDG and 12AS in coastal and continental wetlands had no immediate or long-term detectable effect on the taxonomic structure and taxa abundance of non-target aquatic invertebrate communities, including chironomids. This applied to the main habitats where mosquito larvae occur, regardless of their geographic location. Flooding, whose frequency and duration depend on local meteorological and hydrological conditions, was identified as the main environmental driver of invertebrate community dynamics. Our findings add support to the environmental safety of currently available Bti formulations when following recommended application rates and best mosquito control practices. Copyright © 2016 Elsevier B.V. All rights reserved.

Environmental geologic studies on the southeastern United States Atlantic Outer Continental Shelf, 1977-1978

USGS Publications Warehouse

Popenoe, Peter; Popenoe, Peter

1981-01-01

This report is a summary of the second year of marine environmental research activities by the U.S. Geological Survey (USGS) on the southeaster U.S. Atlantic Continental Margin, in accordance with with Memorandum of Understanding (MOU) AA551-MU8-13 between the USGS and the Bureau of Land Management (BLM). The report covers studies whose fieldwork was conducted during the period from 1 October 1977 to 30 September 1978. The results of the first year of study are reported in Popenoe (1978a and b) and as U.S. Department of Commerce NTIS report PB 300-820. The purpose of these investigations is to provide basic geologic and oceanographic data to the BLM Outer Continental Shelf (OCS) Marine Environmental Studies Program in support of management decisions which relate to possible development of oil and gas resources of the continental shelf. The objectives of the USGS-BLM geologic research program for fiscal year 1978 (FY-78) were 1) to determine the sedimentation rates and processes on the upper slope and inner Blake Plateau; 2) to determine the distribution, areal extent, and vertical characteristics of geological features supportive of biological communities; 3) to monitor the transport of bottom sediment across the OCS, evaluate its possible effect on pollutant transfer along the seabed and the potential of sediment as a pollutant sink, determine the implications of erosion/deposition on pipeline emplacement, and aid the interpretation of chemical, biological, and physical data; 4) to determine the concentration levels of chosen trace metals and silica in three chemically defined fractions of the suspended particulate matter (seston); 5) to study the shelf edge and slope near areas of oil and gas interest, and the northern portion of the Blake Plateau for evidence of slope instability and other geologic hazards, and 6) to determine the depth and rate of sediment mixing caused by large storms and/or by benthic organisms and where possible to estimate the rate of active sediment accumulation.

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Mark P.; Petersen, Walt A.; Bansemer, Aaron

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms-1 supported growth of hail and large rain drops. Data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

Ecological Functioning in Two Mid-Atlantic Bight Submarine Canyons: Macrofauna Community Trends and the Role of Canyon Specific Processes

NASA Astrophysics Data System (ADS)

Robertson, C.; Bourque, J. R.; Davies, A. J.; Duineveld, G.; Mienis, F.; Brooke, S.; Ross, S. W.; Demopoulos, A. W.

2016-02-01

Submarine canyons are complex systems, acting as major conduits of organic matter along continental shelves and promoting gradients in food resources, turbidity flows, habitat heterogeneity, and areas of sediment resuspension and deposition. In the western North Atlantic, a large multidisciplinary program was conducted in two major Mid-Atlantic Bight (MAB) canyons (Baltimore and Norfolk canyons). This Atlantic Deepwater Canyons project was funded by BOEM, NOAA, and USGS. Here we investigate the `canyon effect' on benthic ecosystem ecology and functioning of two canyon systems by defining canyon specific processes influencing MAB shelf benthic community trends. Sediment cores were collected in 2012 and 2013 with a NIOZ box corer along the main axes ( 180-1200m) of Baltimore and Norfolk Canyon and at comparable depths on the adjacent continental slope. Whole community macrofaunal (>300 μm) abundance and biomass data provided insight into community trends across depth and biogeochemical gradients by coupling diversity metrics and biological trait analyses with sediment biogeochemistry and hydrodynamic data. The canyons exhibited clear differences in sediment profiles, hydrodynamic regimes and enrichment depocenters as well as significantly distinct infauna communities. Interestingly, both canyons showed bimodal distributions in abundances and diversity of infauna and a shallowing of species maxima which was not present on adjacent slopes. We hypothesize that physical canyon processes are important regulators in the depth of observed species maxima and community functioning on the MAB shelf, on local and regional scales. Unique sediment dynamics, organic enrichment, and hydrographic conditions were significant factors in structuring benthic community differences in MAB canyons The study provides a complete benthic infaunal appraisal of two canyon systems in the western Atlantic, incorporating biogeochemistry and oceanography to increase our understanding of canyon ecosystem ecology and provide baseline information on canyon functioning.

Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf

USGS Publications Warehouse

Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra L.; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

2014-01-01

The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187–207 g C m−2 y−1, which are consistent with observed values (47–351 g C m−2 y−1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

Productivity and linkages of the food web of the southern region of the western Antarctic Peninsula continental shelf

NASA Astrophysics Data System (ADS)

Ballerini, Tosca; Hofmann, Eileen E.; Ainley, David G.; Daly, Kendra; Marrari, Marina; Ribic, Christine A.; Smith, Walker O.; Steele, John H.

2014-03-01

The productivity and linkages in the food web of the southern region of the west Antarctic Peninsula continental shelf were investigated using a multi-trophic level mass balance model. Data collected during the Southern Ocean Global Ocean Ecosystem Dynamics field program were combined with data from the literature on the abundance and diet composition of zooplankton, fish, seabirds and marine mammals to calculate energy flows in the food web and to infer the overall food web structure at the annual level. Sensitivity analyses investigated the effects of variability in growth and biomass of Antarctic krill (Euphausia superba) and in the biomass of Antarctic krill predators on the structure and energy fluxes in the food web. Scenario simulations provided insights into the potential responses of the food web to a reduced contribution of large phytoplankton (diatom) production to total primary production, and to reduced consumption of primary production by Antarctic krill and mesozooplankton coincident with increased consumption by microzooplankton and salps. Model-derived estimates of primary production were 187-207 g C m-2 y-1, which are consistent with observed values (47-351 g C m-2 y-1). Simulations showed that Antarctic krill provide the majority of energy needed to sustain seabird and marine mammal production, thereby exerting a bottom-up control on higher trophic level predators. Energy transfer to top predators via mesozooplanton was a less efficient pathway, and salps were a production loss pathway because little of the primary production they consumed was passed to higher trophic levels. Increased predominance of small phytoplankton (nanoflagellates and cryptophytes) reduced the production of Antarctic krill and of its predators, including seabirds and seals.

Mineral resource management of the Outer Continental Shelf : leasing procedures, evaluation of resources, and supervision of production operations on leased lands of the Outer Continental Shelf

USGS Publications Warehouse

Adams, Maurice V.; John, C.B.; Kelly, R.F.; LaPointe, A.E.; Meurer, R.W.

1975-01-01

An important function of the Geological Survey is the evaluation and management of the mineral resources of the Outer Continental Shelf, particularly with respect to oil and gas, salt, and sulfur. Production of oil and gas from the Outer Continental Shelf of the United States has increased substantially over the past 20 years and represents an increasing percentage of total United States production. As discovery of major onshore production of oil and gas has become more difficult, the search has moved into the surrounding waters where submerged sedimentary formations are conducive to the accumulation of oil and gas. Increased energy demands of recent years have accelerated the pace of offshore operations with a corresponding improvement in technology as exploration and development have proceeded farther from shore and into deeper water. While improved technology and enforcement of more stringent regulations have made offshore operations safer, it is unrealistic to believe that completely accident-free operations can ever be achieved. Only slightly more than six percent of the world's continental terrace is adjacent to the United States, but less than one percent has been explored for oil and gas. Since the lead time for the development of offshore oil and gas resources can be as much as a decade, they do not provide an immediate energy supply but should be viewed in the light of a near-term source with a potential of becoming a medium-range source of supply pending the development of alternative energy sources. Revenues from the Outer Continental Shelf are deposited to the general fund of the United States Treasury. A major portion of these funds is allocated to the Land and Water Conservation Fund, the largest Federal grant-in-aid program of assistance to States, counties, and cities for the acquisition and development of public parks, open space, and recreation lands and water.

Making continental-scale environmental programs relevant locally for educators with Project BudBurst

NASA Astrophysics Data System (ADS)

Goehring, L.; Henderson, S.; Wasser, L.; Newman, S. J.; Ward, D.

2012-12-01

Project BudBurst is a national citizen science initiative designed to engage non professionals in observations of phenological (plant life cycle) events that raise awareness of climate change, and create a cadre of informed citizen scientists. Citizen science programs such as Project BudBurst provide excellent opportunities for educators and their students to actively participate in scientific research. Such programs are important not only from an educational perspective, but because they also enable scientists to broaden the geographic and temporal scale of their observations. The goals of Project BudBurst are to 1) increase awareness of phenology as an area of scientific study; 2) increase awareness of the impacts of changing climates on plants at a continental-scale; and 3) increase science literacy by engaging participants in the scientific process. From its 2008 launch, this on-line program has engaged participants of all ages and walks of life in recording the timing of the leafing and flowering of wild and cultivated species found across the continent, and in contemplating the meaning of such data in their local environments. Thus far, thousands of participants from all 50 states have submitted data. This presentation will provide an overview of Project BudBurst educational resources and share lessons learned from educators in implementing the program in formal and informal education settings. Lesson plans and tips from educators will be highlighted. Project BudBurst is co-managed by the National Ecological Observatory Network and the Chicago Botanic Garden.

40 CFR 70.2 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... program to control air pollution from outer continental shelf sources, under section 328 of the Act; (12... other functionally-equivalent opening. General permit means a part 70 permit that meets the requirements of § 70.6(d). Major source means any stationary source (or any group of stationary sources that are...

40 CFR 70.2 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... program to control air pollution from outer continental shelf sources, under section 328 of the Act; (12... other functionally-equivalent opening. General permit means a part 70 permit that meets the requirements of § 70.6(d). Major source means any stationary source (or any group of stationary sources that are...

40 CFR 70.2 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... program to control air pollution from outer continental shelf sources, under section 328 of the Act; (12... other functionally-equivalent opening. General permit means a part 70 permit that meets the requirements of § 70.6(d). Major source means any stationary source (or any group of stationary sources that are...

An Entrepreneur Sees Profits in the Future of His "Power Campus."

ERIC Educational Resources Information Center

Blumenstyk, Goldie

1998-01-01

The new president of American InterContinental University bought the for-profit institution and plans to distinguish it from others by offering students fast-paced programs providing "good return" on tuition investment. The growth strategy is built on the concept of "power campuses": new branches specializing in business…

30 CFR 281.1 - Purpose and applicability.

Code of Federal Regulations, 2011 CFR

2011-07-01

... INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF... a leasing program for minerals other than oil, gas, and sulphur in the OCS. The rules in this part apply exclusively to leasing activities for minerals other than oil, gas, and sulphur in the OCS...

76 FR 30184 - Outer Continental Shelf (OCS) Renewable Energy Program Interim Policy Leasing for Marine...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-24

... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management, Regulation and Enforcement [Docket..., Regulation and Enforcement (BOEMRE), Interior. ACTION: Notice of Intent (NOI) to Prepare an Environmental... technology testing facility located on the OCS, in accordance with the Department of the Interior and the...

HumRRO Research on Officer Training.

ERIC Educational Resources Information Center

McClellan, William A.; And Others

This document records the four presentations on officer training and education research programs made by members of the Human Resources Research Organization (HumRRO) staff at a briefing sponsored by the Office of the Deputy Chief of Staff for Individual Training at Headquarters, U.S. Continental Army Command in July 1970. The presentations…

76 FR 56683 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Revisions to Safety and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-14

... implementation of SEMS programs, and establishing requirements for reporting unsafe working conditions. In... be under investigation, the event further illustrates the importance of ensuring safe operations on... safer and with appropriate protections for workers and the environment. BOEMRE may consider further...

Mantle convection and the distribution of geochemical reservoirs in the silicate shell of the Earth

NASA Astrophysics Data System (ADS)

Walzer, Uwe; Hendel, Roland

2010-05-01

We present a dynamic 3-D spherical-shell model of mantle convection and the evolution of the chemical reservoirs of the Earth`s silicate shell. Chemical differentiation, convection, stirring and thermal evolution constitute an inseparable dynamic system. Our model is based on the solution of the balance equations of mass, momentum, energy, angular momentum, and four sums of the number of atoms of the pairs 238U-206Pb, 235U-207Pb, 232Th-208Pb, and 40K-40Ar. Similar to the present model, the continental crust of the real Earth was not produced entirely at the start of the evolution but developed episodically in batches [1-7]. The details of the continental distribution of the model are largely stochastic, but the spectral properties are quite similar to the present real Earth. The calculated Figures reveal that the modeled present-day mantle has no chemical stratification but we find a marble-cake structure. If we compare the observational results of the present-day proportion of depleted MORB mantle with the model then we find a similar order of magnitude. The MORB source dominates under the lithosphere. In our model, there are nowhere pure unblended reservoirs in the mantle. It is, however, remarkable that, in spite of 4500 Ma of solid-state mantle convection, certain strong concentrations of distributed chemical reservoirs continue to persist in certain volumes, although without sharp abundance boundaries. We deal with the question of predictable and stochastic portions of the phenomena. Although the convective flow patterns and the chemical differentiation of oceanic plateaus are coupled, the evolution of time-dependent Rayleigh number, Rat , is relatively well predictable and the stochastic parts of the Rat(t)-curves are small. Regarding the juvenile growth rates of the total mass of the continents, predictions are possible only in the first epoch of the evolution. Later on, the distribution of the continental-growth episodes is increasingly stochastic. Independently of the varying individual runs, our model shows that the total mass of the present-day continents is not generated in a single process at the beginning of the thermal evolution of the Earth but in episodically distributed processes in the course of geological time. This is in accord with observation. Finally, we present results regarding the numerical method, implementation, scalability and performance. References [1] Condie, K. C., Episodie continental growth models: Afterthoughts and extensions, Tectonophysics, 322 (2000), 153-162. [2] Davidson, J. P. and Arculus, R. J., The significance of Phanerozoic arc magmatism in generating continental crust, in Evolution and Differentiation of the Continental Crust, edited by M. Brown and T. Rushmer (2006), 135-172, Cambridge Univ. Press, Cambridge, UK. [3] Hofmann, A. W., Sampling mantle heterogeneity through oceanic basalts: Isotopes and trace elements, in Treatise on Geochemistry, Vol. 2: The Mantle and the Core, edited by R. W. Carlson (2003), 61-101, Elsevier, Amsterdam. [4] Rollinson, H., Crustal generation in the Archean, in Evolution and Differentiation of the Continental Crust, edited by M. Brown and T. Rushmer (2006), 173-230, Cambridge Univ. Press, Cambridge, UK: [5] Taylor, S. R. and McLennan, S. M., Planetary Crusts. Their Composition, Origin and Evolution. (2009), 1-378, Cambridge Univ. Press, Cambridge, UK. [6] Walzer, U. and Hendel, R., Mantle convection and evolution with growing continents. J. Geophys. Res. 113 (2008), B09405, doi: 10.1029/2007JB005459 [7] http://www.igw.uni-jena.de/geodyn

Coastal Environment, Bathymetry and Physical Oceanography along the Beaufort, Chukchi and Bering Seas.

DTIC Science & Technology

1980-01-01

Unit No. 347 , Vol. III, Chukchi-Beaufort Sea, 409 pp. 3. Hopkins, D.M. and R.W. Hartz, 1978, Coastal morphology, coastal erosion, and barrier islands of...U.S. Department of Commerce, Alaska Outer Continental Shelf Environmental Assessment Program Final Report, Research Unit No. 347 , vol. III, Chukchi...Assessment Program Final Report, Research Univ No. 347 , vol. II, Bering Sea, 443 pp. 3. U.S. Department of Commerce, 1964, Pacific and Arctic Coasts

3D dynamics of crustal deformation driven by oblique subduction: Northern and Central Andes

NASA Astrophysics Data System (ADS)

Schütt, Jorina M.; Whipp, David M., Jr.

2017-04-01

The geometry and relative motion of colliding plates will affect how and where they deform. In oblique subduction systems, factors such as the dip angle of the subducting plate and the convergence obliquity, as well as the presence of weak zones in the overriding plate, all influence how oblique convergence is partitioned onto various fault systems in the overriding plate. The partitioning of strain into margin-normal slip on the plate-bounding fault and horizontal shearing on a strike-slip system parallel to the margin is mainly controlled by the margin-parallel shear forces acting on the plate interface and the strength of the continental crust. While these plate interface forces are influenced by the dip angle of the subducting plate (i.e., the length of plate interface in the frictional domain) and the obliquity angle between the normal to the plate margin and the plate convergence vector, the strength of the continental crust in the upper plate is strongly affected by the presence or absence of weak zones such as regions of arc volcanism, pre-existing fault systems, or boundaries of stronger crustal blocks. In order to investigate which of these factors are most important in controlling how the overriding continental plate deforms, we compare results of lithospheric-scale 3D numerical geodynamic experiments from two regions in the north-central Andes: the Northern Volcanic Zone (NVZ; 5°N - 3°S) and adjacent Peruvian Flat Slab Segment (PFSS; 3°S -14°S). The NVZ is characterized by a 35° subduction dip angle with an obliquity angle of about 40°, extensive volcanism and significant strain partitioning in the continental crust. In contrast, the PFSS is characterized by flat subduction (the slab flattens beneath the continent at around 100 km depth for several hundred kilometers), an obliquity angle of about 20°, no volcanism and minimal strain partitioning. The plate geometry and convergence obliquity for these regions are incorporated in 3D (1600 x 1600 x 160 km) numerical experiments of oceanic subduction beneath a continent, focusing on the conditions under which strain partitioning occurs in the continental plate. In addition to different slab geometries and obliquity angles, we consider the effect of a continental crustal of uniform strength (friction angle Φ=15^°) versus one including a weak zone in the continental crust (Φ=4^°) that runs parallel to the margin. Results of our experiments show that the obliquity angle has the largest effect on initiating strain partitioning, as expected based on strain partitioning theory, but strain partitioning is clearly enhanced by the presence of a continental weakness. Margin-parallel mass transport velocities in the continental sliver are similar to the values observed in the NVZ (about 1 cm/year) in models with a continental weakness and twice as high as those without. In addition, a shallower subduction angle results in formation of a wider continental sliver. Based upon our results, the lack of strain partitioning observed in the PFSS results from both a low convergence obliquity and lack of a weak zone in the continent, even though the shallow subduction should make strain partitioning more favorable.

SEAWAT: A Computer Program for Simulation of Variable-Density Groundwater Flow and Multi-Species Solute and Heat Transport

USGS Publications Warehouse

Langevin, Christian D.

2009-01-01

SEAWAT is a MODFLOW-based computer program designed to simulate variable-density groundwater flow coupled with multi-species solute and heat transport. The program has been used for a wide variety of groundwater studies including saltwater intrusion in coastal aquifers, aquifer storage and recovery in brackish limestone aquifers, and brine migration within continental aquifers. SEAWAT is relatively easy to apply because it uses the familiar MODFLOW structure. Thus, most commonly used pre- and post-processors can be used to create datasets and visualize results. SEAWAT is a public domain computer program distributed free of charge by the U.S. Geological Survey.

Regional Geology Web Map Application Development: Javascript v2.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Glenn

This is a milestone report for the FY2017 continuation of the Spent Fuel, Storage, and Waste, Technology (SFSWT) program (formerly Used Fuel Disposal (UFD) program) development of the Regional Geology Web Mapping Application by the Idaho National Laboratory Geospatial Science and Engineering group. This application was developed for general public use and is an interactive web-based application built in Javascript to visualize, reference, and analyze US pertinent geological features of the SFSWT program. This tool is a version upgrade from Adobe FLEX technology. It is designed to facilitate informed decision making of the geology of continental US relevant to themore » SFSWT program.« less

Oceanic heat pulses fueling moisture transport towards continental Europe across the mid-Pleistocene transition

NASA Astrophysics Data System (ADS)

Bahr, A.; Kaboth, S.; Hodell, D.; Zeeden, C.; Fiebig, J.; Friedrich, O.

2018-01-01

The mid-Pleistocene Transition (MPT; approx. 1.2-0.7 Ma), is characterized by growing Northern Hemisphere ice sheets and the shift from a 41 kyr to a 100 kyr glacial-interglacial cyclicity. Concomitant to the growth of large ice sheets, atmospheric and oceanic circulation pattern have changed. One key feature of the North Atlantic is the wind-driven Subtropical Gyre, a major provider of heat and moisture for continental Europe. Here, we investigate changes in the strength and spatial configuration of the Subtropical Gyre during the MPT and its impact on the continental moisture balance. To reconstruct Subtropical Gyre dynamics, we conducted paired δ18O and Mg/Ca analyses on the deep-dwelling foraminifera Globorotalia inflata from Iberian Margin Site U1385 yielding thermocline temperature (Ttherm) variability between 1400 and 500 ka at the eastern boundary of the Subtropical Gyre. Long-term trends of Ttherm at Site U1385 oppose the North Atlantic climatic evolution of progressively intensified glacials during the MPT. Particularly, glacials MIS 20 and 18 were marked by warm thermocline waters off Iberia. We infer that a southward shift of the (sub)polar front displaced the source region of thermocline waters within the Subtropical Gyre from high to mid-latitudes. In addition, a strong Mediterranean Outflow Water production during the MPT caused the advection of warm waters to Iberia. Humid conditions during MIS 20 and 18 in SE Europe indicate that atmospheric moisture derived from this warm water might have been advected deep into continental Europe and contributed to enhanced growth of Alpine glaciers.

Fire activity and hydrological dynamics in the past 5700 years reconstructed from Sphagnum peatlands along the oceanic-continental climatic gradient in northern Poland

NASA Astrophysics Data System (ADS)

Marcisz, Katarzyna; Gałka, Mariusz; Pietrala, Patryk; Miotk-Szpiganowicz, Grażyna; Obremska, Milena; Tobolski, Kazimierz; Lamentowicz, Mariusz

2017-12-01

Fire is a critical component of many ecosystems and, as predicted by various climate models, fire activity may increase significantly in the following years due to climate change. Therefore, knowledge about the past fire activity of various ecosystems is highly important for future nature conservation purposes. We present results of high-resolution investigation of fire activity and hydrological changes in northern Poland. We analyzed microscopic charcoal from three Sphagnum-dominated peatlands located on the south of Baltic, on the oceanic-continental (west-east) climatic gradient, and reconstructed the history of fire in the last 5700 years. We hypothesize that air circulation patterns are highly important for local fire activity, and that fire activity is more intensive in peatlands influenced by continental air masses. We have found out that forest fires have been occurring regularly since the past millennia and were linked to climatic conditions. We show that fire activity (related to climate and fuel availability) was significantly higher in sites dominated by continental climate (northeastern Poland) than in the site located under oceanic conditions (northwestern Poland)-microscopic charcoal influx was 13.3 times higher in the eastern study site of the gradient, compared to the western study site. Recorded fire activity patterns were different between the sites in a long timescale. Moreover, most of the recorded charcoal peaks occurred during high water tables. Rising human pressure has caused droughts and water table instability, and substantial increase in fire activity in the last 400 years.

Multiple sources and extensive degradation of terrestrial sedimentary organic matter across an energetic, wide continental shelf

NASA Astrophysics Data System (ADS)

Zhu, Chun; Wagner, Thomas; Pan, Jian-Ming; Pancost, Richard D.

2011-08-01

The fate of organic carbon in marine sediments is closely linked to atmospheric CO2 concentrations and thus to climate variability over geological time scales. The East China Sea (ECS) is characterized not only by massive terrestrial organic matter (TOM) inputs from the Yangtze (Changjiang) River but also by a shallow (<130 m) and broad (>500 km) continental shelf with widespread relict sands, such that it is distinct from other continental margins. We examine the diagenesis of sedimentary TOM and the impacts of relict sands on TOM in the ECS. The results reveal that bulk δ13Corg values correlate with terrestrial biomarker concentrations in muddy and accumulative areas; in contrast, depleted δ13Corg values around -24.5‰ co-occur with almost absent terrestrial biomarkers in sandy/erosional areas. We suggest that mixing of contemporary TOM and marine OM dominates in the muddy/accumulative shelf areas, whereas a putative relict OM, associated with relict sands, appears to be significant in many sandy/erosional shelf areas. Given the global occurrence of relict sands, a persistent amount of relict OC (e.g., 0.1%) may complicate TOM budget calculations. In addition, our observations reveal that TOM is extensively partitioned and degraded in the estuary and continues to be partitioned and degraded during the along-shore and across-shelf transport, which is reflected by decreases in terrestrial biomarker concentrations and increases in degradation indices. This study highlights the unique and dynamic role of shallow and wide continental shelves with massive relict sands on TOM cycling.

Last Glacial Maximum to Holocene climate evolution controlled by sea-level change, Leeuwin Current, and Australian Monsoon in the Northwestern Australia

NASA Astrophysics Data System (ADS)

Ishiwa, T.; Yokoyama, Y.; McHugh, C.; Reuning, L.; Gallagher, S. J.

2017-12-01

The transition from cold to warm conditions during the last deglaciation influenced climate variability in the Indian Ocean and Pacific as a result of submerge of continental shelf and variations in the Indonesian Throughflow and Australian Monsoon. The shallow continental shelf (< 200 m water depth) developed along the northwestern Australian margin is influenced by the Australian Monsoon and Leeuwin Current (one of branch of the Indonesian Throughflow). The International Ocean Discovery Program Expedition 356 Indonesian Throughflow drilled in the northwestern Australian shallow continental shelf and recovered an interval from the Last Glacial Maximum to Holocene in Site U1461. Radiocarbon dating on macrofossils, foraminifera, and bulk organic matter provided a precise age-depth model, leading to high-resolved paleoclimate reconstruction. X-ray elemental analysis results are interpreted as an indicator of sedimentary environmental changes. The upper 20-m part of Site U1461 apparently records the climate transition from the LGM to Holocene in the northwestern Australia, which could be associated with sea-level change, Leeuwin Current activity, and the Australian Monsoon.

Temporal and Spatial Scales of Sub-Continental Mantle Convection: Comparison of Modern and Geological Observations of Dynamic Support

NASA Astrophysics Data System (ADS)

Jones, S. M.; Lovell, B.; Crosby, A. G.

2011-12-01

The topographies of Africa and Antarctica form patterns of interlocking swells. The admittance between swell topography and free-air gravity indicates that these swells are dynamically supported by mantle convection, with swell diameters of 1850±450 km and full heights between 800 and 1800 m. The implication is that mantle convection not only supports swells surrounding hotspots but also influences topography across the entire surface areas of Africa and Antarctica. Topographic swells and associated gravity anomalies with diameters over 1000 km are observed on other continents and throughout the oceans. Numerical models support the idea that dynamically supported swell topography is a worldwide phenomenon. We investigate whether dynamically supported swells are also observed throughout the geological record, focussing on intensively studied Mesozoic- Cenozoic sedimentary rocks around Britain and Ireland. Since 200 Ma, this region was affected by three dynamically supported swells that peaked during the Middle Jurassic, Early Cretaceous and Eocene (c. 175, 146 and 56 Ma), each several thousand kilometres in diameter, and the region now lies on the edge of the modern swell centred on Iceland. The diameters and maximum heights of the Mesozoic British swells and the modern African and Antarctic swells are similar. The ancient British swells grew in 5--10 Myr and decayed over 20--30 Myr, suggesting vertical motion rates comparable to those estimated from geomorphological studies of Africa. Igneous production rate and swell height are not correlated in the modern and the geological records. Vertical motions of Britain and Ireland, a typical piece of continental lithosphere far from a destructive plate boundary, have been demonstrably affected by convective support for over half of the past 200 Ma period. Mantle convection should be considered as a common control on regional sea-level at time periods from 10s down to 1 Myr or less, and with vertical motion rates in the order 10s to 100s m/Myr.

Phosphate rock formation and marine phosphorus geochemistry: the deep time perspective.

PubMed

Filippelli, Gabriel M

2011-08-01

The role that phosphorite formation, the ultimate source rock for fertilizer phosphate reserves, plays in the marine phosphorus (P) cycle has long been debated. A shift has occurred from early models that evoked strikingly different oceanic P cycling during times of widespread phosphorite deposition to current thinking that phosphorite deposits may be lucky survivors of a series of inter-related tectonic, geochemical, sedimentological, and oceanic conditions. This paradigm shift has been facilitated by an awareness of the widespread nature of phosphogenesis-the formation of authigenic P-bearing minerals in marine sediments that contributes to phosphorite formation. This process occurs not just in continental margin sediments, but in deep sea oozes as well, and helps to clarify the driving forces behind phosphorite formation and links to marine P geochemistry. Two processes come into play to make phosphorite deposits: chemical dynamism and physical dynamism. Chemical dynamism involves the diagenetic release and subsequent concentration of P-bearing minerals particularly in horizons, controlled by a number of sedimentological and biogeochemical factors. Physical dynamism involves the reworking and sedimentary capping of P-rich sediments, which can either concentrate the relatively heavy and insoluble disseminated P-bearing minerals or provide an episodic change in sedimentology to concentrate chemically mobilized P. Both processes can result from along-margin current dynamics and/or sea level variations. Interestingly, net P accumulation rates are highest (i.e., the P removal pump is most efficient) when phosphorites are not forming. Both physical and chemical pathways involve processes not dominant in deep sea environments and in fact not often coincide in space and time even on continental margins, contributing to the rarity of high-quality phosphorite deposits and the limitation of phosphate rock reserves. This limitation is becoming critical, as the human demand for P far outstrips the geologic replacement for P and few prospects exist for new discoveries of phosphate rock. Copyright © 2011 Elsevier Ltd. All rights reserved.

U.s. Geological survey core drilling on the atlantic shelf.

PubMed

Hathaway, J C; Poag, C W; Valentine, P C; Manheim, F T; Kohout, F A; Bothner, M H; Miller, R E; Schultz, D M; Sangrey, D A

1979-11-02

The first broad program of scientific shallow drilling on the U.S. Atlantic continental shelf has delineated rocks of Pleistocene to Late Cretaceous age, including phosphoritic Miocene strata, widespread Eocene carbonate deposits that serve as reflective seismic markers, and several regional unconformities. Two sites, off Maryland and New Jersey, showed light hydrocarbon gases having affinity to mature petroleum. Pore fluid studies showed that relatively fresh to brackish water occurs beneath much of the Atlantic continental shelf, whereas increases in salinity off Georgla and beneath the Florida-Hatteras slope suggest buried evaporitic strata. The sediment cores showed engineering properties that range from good foundation strength to a potential for severe loss of strength through interaction between sediments and man-made structures.

Statistical cyclicity of the supercontinent cycle

NASA Astrophysics Data System (ADS)

Rolf, T.; Coltice, N.; Tackley, P. J.

2014-04-01

Supercontinents like Pangea impose a first-order control on Earth's evolution as they modulate global heat loss, sea level, climate, and biodiversity. In a traditional view, supercontinents form and break up in a regular, perhaps periodic, manner in a cycle lasting several 100 Myr as reflected in the assembly times of Earth's major continental aggregations: Columbia, Rodinia, and Pangea. However, modern views of the supercontinent cycle propose a more irregular evolution on the basis of an improved understanding of the Precambrian geologic record. Here we use fully dynamic spherical mantle convection models featuring plate-like behavior and continental drift to investigate supercontinent formation and breakup. We further dismiss the concept of regularity but suggest a statistical cyclicity in which the supercontinent cycle may have a characteristic period imposed by mantle and lithosphere properties, but this is hidden in immense fluctuations between different cycles that arise from the chaotic nature of mantle flow.

Rippled scour depressions on the inner continental shelf off central California

USGS Publications Warehouse

Cacchione, David A.; Drake, David E.; Grant, William D.; Tate, George B.

1984-01-01

Side-scan sonar records taken during the recent Coastal Ocean Dynamics Experiment (CODE) show elongate, shore-normal tippled depressions of low relief on the inner continental shelf off central California between Bodega Bay and Point Arena. These features extend up to 2 kin from the coast into water depths of up to 65 m. The proposed mechanism for their generation is storm- generated bottom currents associated with coastal downwelling during the late fall and winter which scour the surficial fine-sand sediment and expose the coarser-sand substrate in the depressions. The zones of most intense erosion and the irregular spacing of the features may be controlled by submerged rock ledges and other prominent coastal features. The large straight-crested ripples within the depres- sions (heights to 40 cm; wavelengths to 1.7 m) are probably formed by large-amplitude, long-period surface waves generated by winter storms.

Gulf of Mexico physical-oceanography program final report: years 1 and 2. Volume 1. Executive summary. Technical report, 1983-1985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

In 1982, Minerals Management Service (MMS) initiated a multi-year program under contract with Science Applications International Corp. (SAIC) to study the physical oceanography of the Gulf of Mexico as part of its outer continental shelf environmental-studies programs. This particular program, called the Gulf of Mexico Physical Oceanography Program (GOMPOP), has two primary goals: (1) develop a better understanding and description of conditions and processes governing Gulf circulation; and (2) establish a data base that could be used as initial and boundary conditions by a companion MMS-funded numerical circulation-modeling program. The report presents results from the first two of three yearsmore » of observations in the eastern Gulf.« less

Clay mineral continental amplifier for marine carbon sequestration in a greenhouse ocean

PubMed Central

Kennedy, Martin J.; Wagner, Thomas

2011-01-01

The majority of carbon sequestration at the Earth’s surface occurs in marine continental margin settings within fine-grained sediments whose mineral properties are a function of continental climatic conditions. We report very high mineral surface area (MSA) values of 300 and 570 m2 g in Late Cretaceous black shales from Ocean Drilling Program site 959 of the Deep Ivorian Basin that vary on subcentennial time scales corresponding with abrupt increases from approximately 3 to approximately 18% total organic carbon (TOC). The observed MSA changes with TOC across multiple scales of variability and on a sample-by-sample basis (centimeter scale), provides a rigorous test of a hypothesized influence on organic carbon burial by detrital clay mineral controlled MSA. Changes in TOC also correspond with geochemical and sedimentological evidence for water column anoxia. Bioturbated intervals show a lower organic carbon loading on mineral surface area of 0.1 mg-OC m-2 when compared to 0.4 mg-OC m-2 for laminated and sulfidic sediments. Although either anoxia or mineral surface protection may be capable of producing TOC of < 5%, when brought together they produced the very high TOC (10–18%) apparent in these sediments. This nonlinear response in carbon burial resulted from minor precession-driven changes of continental climate influencing clay mineral properties and runoff from the African continent. This study identifies a previously unrecognized land–sea connection among continental weathering, clay mineral production, and anoxia and a nonlinear effect on marine carbon sequestration during the Coniacian-Santonian Oceanic Anoxic Event 3 in the tropical eastern Atlantic. PMID:21576498

Impacts of tropospheric ozone and climate change on net primary productivity and net carbon exchange of China’s forest ecosystems

Treesearch

Wei Ren; Hanqin Tian; Bo Tao; Art Chappelka; Ge Sun; et al

2011-01-01

Aim We investigated how ozone pollution and climate change/variability have interactively affected net primary productivity (NPP) and net carbon exchange (NCE) across China’s forest ecosystem in the past half century. Location Continental China. Methods Using the dynamic land ecosystem model (DLEM) in conjunction with 10-km-resolution gridded historical data sets (...

Two Decades of WRF/CMAQ simulations over the continental ...

EPA Pesticide Factsheets

Confidence in the application of models for forecasting and regulatory assessments is furthered by conducting four types of model evaluation: operational, dynamic, diagnostic, and probabilistic. Operational model evaluation alone does not reveal the confidence limits that can be associated with modeled air quality concentrations. This paper presents novel approaches for performing dynamic model evaluation and for evaluating the confidence limits of ozone exceedances using the WRF/CMAQ model simulations over the continental United States for the period from 1990 to 2010. The methodology presented here entails spectral decomposition of ozone time series using the KZ filter to assess the variations in the strengths of the synoptic (i.e., weather-induced variation) and baseline (i.e., long-term variation attributable to emissions, policy, and trends) forcings embedded in the modeled and observed concentrations. A method is presented where the future year observations are estimated based on the changes in the concentrations predicted by the model applied to the current year observations. The proposed method can provide confidence limits for ozone exceedances for a given emission reduction scenario. We present and discuss these new approaches to identify the strengths of the model in representing the changes in simulated O3 air quality over the 21-year period. The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates

Modeling the Dynamics and Export of Dissolved Organic Matter in the Northeastern U.S. Continental Shelf

NASA Technical Reports Server (NTRS)

Druon, J.N.; Mannino, A.; Signorini, Sergio R.; McClain, Charles R.; Friedrichs, M.; Wilkin, J.; Fennel, K.

2009-01-01

Continental shelves are believed to play a major role in carbon cycling due to their high productivity. Particulate organic carbon (POC) burial has been included in models as a carbon sink, but we show here that seasonally produced dissolved organic carbon (DOC) on the shelf can be exported to the open ocean by horizontal transport at similar rates (1-2 mol C/sq m/yr) in the southern U.S. Mid-Atlantic Bight (MAB). The dissolved organic matter (DOM) model imbedded in a coupled circulation-biogeochemical model reveals a double dynamics: the progressive release of dissolved organic nitrogen (DON) in the upper layer during summer increases the regenerated primary production by 30 to 300%, which, in turns ; enhances the DOC production mainly from phytoplankton exudation in the upper layer and solubilization of particulate organic matter (POM) deeper in the water column. This analysis suggests that DOM is a key element for better representing the ecosystem functioning and organic fluxes in models because DOM (1) is a major organic pool directly related to primary production, (2) decouples partially the carbon and nitrogen cycles (through carbon excess uptake, POM solubilization and DOM mineralization) and (3) is intimately linked to the residence time of water masses for its distribution and export.

A coordinated set of ecosystem research platforms open to international research in ecotoxicology, AnaEE-France.

PubMed

Mougin, Christian; Azam, Didier; Caquet, Thierry; Cheviron, Nathalie; Dequiedt, Samuel; Le Galliard, Jean-François; Guillaume, Olivier; Houot, Sabine; Lacroix, Gérard; Lafolie, François; Maron, Pierre-Alain; Michniewicz, Radika; Pichot, Christian; Ranjard, Lionel; Roy, Jacques; Zeller, Bernd; Clobert, Jean; Chanzy, André

2015-10-01

The infrastructure for Analysis and Experimentation on Ecosystems (AnaEE-France) is an integrated network of the major French experimental, analytical, and modeling platforms dedicated to the biological study of continental ecosystems (aquatic and terrestrial). This infrastructure aims at understanding and predicting ecosystem dynamics under global change. AnaEE-France comprises complementary nodes offering access to the best experimental facilities and associated biological resources and data: Ecotrons, seminatural experimental platforms to manipulate terrestrial and aquatic ecosystems, in natura sites equipped for large-scale and long-term experiments. AnaEE-France also provides shared instruments and analytical platforms dedicated to environmental (micro) biology. Finally, AnaEE-France provides users with data bases and modeling tools designed to represent ecosystem dynamics and to go further in coupling ecological, agronomical, and evolutionary approaches. In particular, AnaEE-France offers adequate services to tackle the new challenges of research in ecotoxicology, positioning its various types of platforms in an ecologically advanced ecotoxicology approach. AnaEE-France is a leading international infrastructure, and it is pioneering the construction of AnaEE (Europe) infrastructure in the field of ecosystem research. AnaEE-France infrastructure is already open to the international community of scientists in the field of continental ecotoxicology.

Shaping mobile belts by small-scale convection.

PubMed

Faccenna, Claudio; Becker, Thorsten W

2010-06-03

Mobile belts are long-lived deformation zones composed of an ensemble of crustal fragments, distributed over hundreds of kilometres inside continental convergent margins. The Mediterranean represents a remarkable example of this tectonic setting: the region hosts a diffuse boundary between the Nubia and Eurasia plates comprised of a mosaic of microplates that move and deform independently from the overall plate convergence. Surface expressions of Mediterranean tectonics include deep, subsiding backarc basins, intraplate plateaux and uplifting orogenic belts. Although the kinematics of the area are now fairly well defined, the dynamical origins of many of these active features are controversial and usually attributed to crustal and lithospheric interactions. However, the effects of mantle convection, well established for continental interiors, should be particularly relevant in a mobile belt, and modelling may constrain important parameters such as slab coherence and lithospheric strength. Here we compute global mantle flow on the basis of recent, high-resolution seismic tomography to investigate the role of buoyancy-driven and plate-motion-induced mantle circulation for the Mediterranean. We show that mantle flow provides an explanation for much of the observed dynamic topography and microplate motion in the region. More generally, vigorous small-scale convection in the uppermost mantle may also underpin other complex mobile belts such as the North American Cordillera or the Himalayan-Tibetan collision zone.

INTEX-NA: Intercontinental Chemical Transport Experiment - North America

NASA Technical Reports Server (NTRS)

Singh, Hanwant B.; Jacob, D.; Pfister, L.; Hipskind, R. Stephen (Technical Monitor)

2002-01-01

INTEX-NA is an integrated atmospheric chemistry field experiment to be performed over North America using the NASA DC-8 and P-3B aircraft as its primary platforms. It seeks to understand the exchange of chemicals and aerosols between continents and the global troposphere. The constituents of interest are ozone and its precursors (hydrocarbons, NOX and HOX), aerosols, and the major greenhouse gases (CO2, CH4, N2O). INTEX-NA will provide the observational database needed to quantify inflow, outflow, and transformations of chemicals over North America. INTEX-NA is to be performed in two phases. Phase A will take place during the period of May-August 2004 and Phase B during March-June 2006. Phase A is in summer when photochemistry is most intense and climatic issues involving aerosols and carbon cycle are most pressing, and Phase B is in spring when Asian transport to North America is at its peak. INTEX-NA will coordinate its activities with concurrent measurement programs including satellites (e. g. Terra, Aura, Envisat), field activities undertaken by the North American Carbon Program (NACP), and other U.S. and international partners. However, it is being designed as a 'stand alone' mission such that its successful execution is not contingent on other programs. Synthesis of the ensemble of observation from surface, airborne, and space platforms, with the help of global/regional models is an important It is anticipated that approximately 175 flight hours for each of the aircraft (DC-8 and P-3B) will be required for each Phase. Principal operational sites are tentatively selected to be Bangor, ME; Wallops Island, VA; Seattle, WA; Rhinelander, WI; Lancaster, CA; and New Orleans, LA. These coastal and continental sites can support large missions and are suitable for INTEX-NA objectives. The experiment will be supported by forecasts from meteorological and chemical models, satellite observations, surface networks, and enhanced O3,-sonde releases. In addition to characterizing Atlantic-outflow and Pacific-inflow, INTEX-NA will characterize air masses transported between the U.S., Canada, and Mexico. INTEX-NA will be the first continental scale inflow, outflow, and transformation experiment to be performed over North America. It will provide the most comprehensive observational data set to date to understand the O3/NOX/HOX/aerosol photochemical system and the carbon cycle. One of the critical needs of the carbon cycle research is to obtain large-scale vertical and horizontal concentration gradients of CO2, throughout the troposphere over continental source/sink regions. INTEX-NA is ideally suited to perform this role. Coastal and continental operational sites will allow us to develop a curtain profile of greenhouse gases (e. g. CO2,) and other key pollutants across North America. Such information is central to our quantitative understanding of chemical budgets on the continental scale. We expect to provide a number of satellite under-flights over land and water to test and validate observations from the appropriate satellite platform (e. g. Aura). We plan to develop strong collaborations with other national and international observational programs. Results from INTEX-NA should directly benefit the development of environmental policy for air quality and climate change.

Managing North American waterfowl in the face of uncertainty

USGS Publications Warehouse

Robbins, C.S.

1995-01-01

Informed management of waterfowl (or any animal population) requires management goals and objectives, the ability to implement management actions, periodic information about population and goal-related varlables, and knowledge of effects of management actions on population and goal-related variables. In North America, international treaties mandate a primary objective of protecting migratory bird populations, with a secondary objective of providing hunting opportunity in a manner compatible with such protection. Through the years, annual establishment of hunting regulations and acquisition and man-agement of habitat have been the primary management actions taken by federal agencies. Various information-gathering programs were established and, by the 1960s, had developed into arguably the best monitoring system in the world for continentally distributed animal populations. Retrospective analyses using estimates from this monitoring system have been used to investigate effects of management actions on waterfowl population and harvest dynamics, but key relationships arc still characterized by uncertainty. We recommend actively adaptive management as an approach that can meet short-term harvest objectives, while reducing uncertainty and ensuring sustainable populations over the long-term.

[Hyperbolic growth of marine and continental biodiversity through the phanerozoic and community evolution].

PubMed

Markov, A V; Korotaev, A V

2008-01-01

Among diverse models that are used to describe and interpret the changes in global biodiversity through the Phanerozoic, the exponential and logistic models (traditionally used in population biology) are the most popular. As we have recently demonstrated (Markov, Korotayev, 2007), the growth of the Phanerozoic marine biodiversity at genus level correlates better with the hyperbolic model (widely used in demography and macrosociology). Here we show that the hyperbolic model is also applicable to the Phanerozoic continental biota at genus and family levels, and to the marine biota at species, genus, and family levels. There are many common features in the evolutionary dynamics of the marine and continental biotas that imply similarity and common nature of the factors and mechanisms underlying the hyperbolic growth. Both marine and continental biotas are characterized by continuous growth of the mean longevity of taxa, by decreasing extinction and origination rates, by similar pattern of replacement of dominant groups, by stepwise accumulation of evolutionary stable, adaptable and "physiologically buffered" taxa with effective mechanisms of parental care, protection of early developmental stages, etc. At the beginning of the development of continental biota, the observed taxonomic diversity was substantially lower than that predicted by the hyperbolic model. We suggest that this is due, firstly, to the fact that, during the earliest stages of the continental biota evolution, the groups that are not preserved in the fossil record (such as soil bacteria, unicellular algae, lichens, etc.) played a fundamental role, and secondly, to the fact that the continental biota initially formed as a marginal portion of the marine biota, rather than a separate system. The hyperbolic dynamics is most prominent when both marine and continental biotas are considered together. This fact can be interpreted as a proof of the integrated nature of the biosphere. In the macrosociological models, the hyperbolic pattern of the world population growth arises from a non-linear second-order positive feedback between the demographic growth and technological development (more people - more potential inventors - faster technological growth - the carrying capacity of the Earth grows faster - faster population growth - more people - more potential inventors, and so on). Based on the analogy with macrosociological models and diverse paleontological data, we suggest that the hyperbolic character of biodiversity growth can be similarly accounted for by a non-linear second-order positive feedback between the diversity growth and community structure complexity. The feedback can work via two parallel mechanisms: 1) decreasing extinction rate (more taxa- higher alpha diversity, or mean number of taxa in a community - communities become more complex and stable - extinction rate decreases - more taxa, and so on) and 2) increasing origination rate (new taxa facilitate niche construction; newly formed niches can be occupied by the next "generation" of taxa). The latter possibility makes the mechanisms underlying the hyperbolic growth of biodiversity and human population even more similar, because the total ecospace of the biota is analogous to the "carrying capacity of the Earth" in demography. As far as new species can increase ecospace and facilitate opportunities for additional species entering the community, they are analogous to the "inventors" of the demographic models whose inventions increase the carrying capacity of the Earth. The hyperbolic growth of the Phanerozoic biodiverstiy suggests that "cooperative" interactions between taxa can play an important role in evolution, along with generally accepted competitive interactions. Due to this "cooperation", the evolution of biodiversity acquires some features of a self-accelerating process. Macroevolutionary "cooperation" reveals itself in: 1) increasing stability of communities that arises from alpha diversity growth; 2) ability of species to facilitate opportunities for additional species entering the community.

Temporal and Spatial Differences in Microbial Composition during the Manufacture of a Continental-Type Cheese

PubMed Central

O'Sullivan, Daniel J.; O'Sullivan, Orla; McSweeney, Paul L. H.; Sheehan, Jeremiah J.

2015-01-01

We sought to determine if the time, within a production day, that a cheese is manufactured has an influence on the microbial community present within that cheese. To facilitate this, 16S rRNA amplicon sequencing was used to elucidate the microbial community dynamics of brine-salted continental-type cheese in cheeses produced early and late in the production day. Differences in the microbial composition of the core and rind of the cheese were also investigated. Throughout ripening, it was apparent that cheeses produced late in the day had a more diverse microbial population than their early equivalents. Spatial variation between the cheese core and rind was also noted in that cheese rinds were initially found to have a more diverse microbial population but thereafter the opposite was the case. Interestingly, the genera Thermus, Pseudoalteromonas, and Bifidobacterium, not routinely associated with a continental-type cheese produced from pasteurized milk, were detected. The significance, if any, of the presence of these genera will require further attention. Ultimately, the use of high-throughput sequencing has facilitated a novel and detailed analysis of the temporal and spatial distribution of microbes in this complex cheese system and established that the period during a production cycle at which a cheese is manufactured can influence its microbial composition. PMID:25636841

Continental-scale Validation of MODIS-based and LEDAPS Landsat ETM+ Atmospheric Correction Methods

NASA Technical Reports Server (NTRS)

Ju, Junchang; Roy, David P.; Vermote, Eric; Masek, Jeffrey; Kovalskyy, Valeriy

2012-01-01

The potential of Landsat data processing to provide systematic continental scale products has been demonstrated by several projects including the NASA Web-enabled Landsat Data (WELD) project. The recent free availability of Landsat data increases the need for robust and efficient atmospheric correction algorithms applicable to large volume Landsat data sets. This paper compares the accuracy of two Landsat atmospheric correction methods: a MODIS-based method and the Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) method. Both methods are based on the 6SV radiative transfer code but have different atmospheric characterization approaches. The MODIS-based method uses the MODIS Terra derived dynamic aerosol type, aerosol optical thickness, and water vapor to atmospherically correct ETM+ acquisitions in each coincident orbit. The LEDAPS method uses aerosol characterizations derived independently from each Landsat acquisition and assumes a fixed continental aerosol type and uses ancillary water vapor. Validation results are presented comparing ETM+ atmospherically corrected data generated using these two methods with AERONET corrected ETM+ data for 95 10 km×10 km 30 m subsets, a total of nearly 8 million 30 m pixels, located across the conterminous United States. The results indicate that the MODIS-based method has better accuracy than the LEDAPS method for the ETM+ red and longer wavelength bands.

Regional inversion of GRACE data for continental water mass time-variations. Comparison with global hydrology models, classical spherical harmonics and "mascons" solutions

NASA Astrophysics Data System (ADS)

Seoane, L.; Ramillien, G.; Frappart, F.; Biancale, R.; Gratton, S.; Bourgogne, S.

2010-12-01

Time series of 2°-by-2° constrained/unconstrained GRACE geoid solutions have been computed with a 10-day resolution by using a new regional method recently implemented at GRGS (Toulouse, France). This approach uses the dynamical orbit analysis of GRACE Level-1 measurements, and specially accurate along-track KBRR residuals to estimate the continental water mass changes over large geographical regions. For validation, our GRACE-derived regional maps are compared to: (1) the global hydrological model outputs (WGHM, LaD, NOAH), (2) the NASA "mascons" solutions based on spherical harmonics and (3) the global solutions produced by GRGS and CSR, GFZ, JPL filtered with different methodologies (Gaussian, destriped and smoothed, ICA). In this study, we focus on the annual time scale of water mass redistributions occuring in drainage basins like Amazon or Congo. Each 2°-averaged surface element is characterized by its seasonal amplitude and phase. Even if the all sources are expected to provide quite comparable results for the continental water cycle, we suspect the residual differences are from smoothing effects of the spatial constraints included in the "mascons" solutions and the underestimating the seasonal amplitudes by global hydrological models.

Volcanic passive margins: another way to break up continents

PubMed Central

Geoffroy, L.; Burov, E. B.; Werner, P.

2015-01-01

Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle. PMID:26442807

Variability of High-Resolution Sea Surface Heights on a Broad, Shallow Continental Shelf

NASA Astrophysics Data System (ADS)

Crout, R. L.; Rice, A. E.

2017-12-01

Recent satellite altimeter technologies and processing methodologies are allowing investigation of the dynamics of the continental shelf as never before. The region seaward of 20 km from the coast is a region where winds, tides, currents, river discharge, and bathymetry interact. All of these are important parameters to understand when applying coastal altimetry to coastal sea level monitoring. Processing of 8 years (July 2008 to July 2016) of Jason-2 altimeter 20 Hz data from the L2 AVISO-PISTACH experimental products yields nearly 300 crossings of the broad continental shelf to the southeast of Delaware Bay from Cape May, NJ. Removal of a mean surface yields individual crossings that, plotted together, form an envelope that shows high water level variability near the coast. Water level changes near the coast begin at a hinge point that occurs approximately 50 km from shore in less than 30 meters of water. Comparison of individual Jason-2 passes with regional weather patterns, cold front passages, local winds, tides, surface currents, river discharge, and regional oceanography provides information regarding the forcing factors for these regional water levels. The water levels farther than 20 km from shore show similar patterns to the low pass filtered tide data at Cape May, NJ and respond primarily to regional forcing.

Volcanic passive margins: another way to break up continents.

PubMed

Geoffroy, L; Burov, E B; Werner, P

2015-10-07

Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

Global warming and ocean acidification through halted weathering feedback during the Middle Eocene Climatic Optimum

NASA Astrophysics Data System (ADS)

van der Ploeg, R.; Selby, D. S.; Cramwinckel, M.; Bohaty, S. M.; Sluijs, A.; Middelburg, J. J.

2016-12-01

The Middle Eocene Climatic Optimum (MECO) represents a 500 kyr period of global warming 40 million years ago associated with a rise in atmospheric CO2 concentrations, but its cause remains enigmatic. Moreover, on the timescale of the MECO, an increase in silicate weathering rates on the continents is expected to balance carbon input and restore the alkalinity of the oceans, but this is in sharp disagreement with observations of extensive carbonate dissolution. Here we show, based on osmium isotope ratios of marine sediments from three different sites, that CO2 rise and warming did not lead to enhanced continental weathering during the MECO, in contrast to expectations from carbon cycle theory. Remarkably, a minor shift to lower, more unradiogenic osmium isotope ratios rather indicates an episode of increased volcanism or reduced continental weathering. This disproves silicate weathering as a geologically constant feedback to CO2 variations. Rather, we suggest that global Early and Middle Eocene warmth diminished the weatherability of continental rocks, ultimately leading to CO2 accumulation during the MECO, and show the plausibility of this scenario using carbon cycle modeling simulations. We surmise a dynamic weathering feedback might explain multiple enigmatic phases of coupled climate and carbon cycle change in the Cretaceous and Cenozoic.

Soil Characterization and Site Response of Marine and Continental Environments

NASA Astrophysics Data System (ADS)

Contreras-Porras, R. S.; Huerta-Lopez, C. I.; Martinez-Cruzado, J. A.; Gaherty, J. B.; Collins, J. A.

2009-05-01

An in situ soil properties study was conducted to characterize both site and shallow layer sediments under marine and continental environments. Data from the SCoOBA (Sea of Cortez Ocean Bottom Array) seismic experiment and in land ambient vibration measurements on the urban areas of Tijuana, B. C., and Ensenada, B. C., Mexico were used in the analysis. The goal of this investigation is to identify and to analyze the effect of the physical/geotechnical properties of the ground on the site response upon seismic excitations in both marine and continental environments. The time series were earthquakes and background noise recorded within interval of 10/2005 to 10/2006 in the Gulf of California (GoC) with very-broadband Ocean Bottom Seismographs (OBS), and ambient vibration measurements collected during different time periods on Tijuana and Ensenada urban areas. The data processing and analysis was conducted by means of the H/V Spectral Ratios (HVSPR) of multi component data, the Random Decrement Method (RDM), and Blind Deconvolution (BD). This study presents ongoing results of a long term project to characterize the local site response of soil layers upon dynamic excitations using digital signal processing algorithms on time series, as well as the comparison between the results these methodologies are providing.

Multi-Agent Simulations of Earth's Dynamics: Towards a Virtual Laboratory for Plate Tectonics

NASA Astrophysics Data System (ADS)

Grigne, C.; Combes, M.; Tisseau, C.; LeYaouanq, S.; Parenthoen, M.; Tisseau, J.

2012-12-01

MACMA (Multi-Agent Convective MAntle) is a new tool developed at Laboratoire Domaines Océaniques (UMR CNRS 6538) and CERV-LabSTICC (Centre Européen de Réalité Virtuelle, UMR CNRS 6285) to simulate evolutive plates tectonics and mantle convection in a 2-D cylindrical geometry (Combes et al., 2012). In this approach, ridges, subduction zones, continents and convective cells are agents, whose behavior is controlled by analytical and phenomenological laws. These agents are autonomous entities which collect information from their environment and interact with each other. The dynamics of the system is mainly based on a force balance on each plate, that accounts for slab pull, ridge push, bending dissipation and viscous convective drag. Insulating continents are accounted for. Tectonic processes such as trench migration, plate suturing or continental breakup are controlled by explicit parameterizations. A heat balance is used to compute Earth's thermal evolution as a function of seafloor age distribution. We thereby obtain an evolutive system where the geometry and the number of tectonic plates are not imposed but emerge naturally from its dynamical history. Our approach has a very low computational cost and allows us to study the effect of a wide range of input parameters on the long-term thermal evolution of the Earth. MACMA can thus be seen as a 'plate tectonics virtual laboratory'. We can test not only the effect of input parameters, such as mantle initial temperature and viscosity, initial plate tectonics configuration, number and geometry of continents etc., but also study the effect of the analytical and empirical rules that we are using to describe the system. These rules can be changed at any time, and MACMA is an evolutive tool that can easily integrate new behavioral laws. Even poorly understood processes, that cannot be accounted for with differential equations, can be studied with this virtual laboratory. For Earth-like input parameters, MACMA yields plate velocities and heat flux that are in good agreement with observations. The long-term thermal evolution of the Earth obtained with our model shows a slow monotonous decrease of mantle mean temperature, with a cooling rate of around 50-100 K per billion years, which is in good agreement with petrological and geochemical constraints. Heat flux and plate velocities show a more irregular evolution, because tectonic events, such as a continental breakup, give rise to abrupt changes in Earth's surface dynamics and heat loss. Therefore MACMA is a powerful tool to study in a systematic way the effect of local events (subduction initiation, continental breakup, ridge vanishing) on plate reorganizations and global surface dynamics.

Galveston Symposium: Physical Oceanography of the Louisiana/Texas Continental Shelf

NASA Astrophysics Data System (ADS)

Mitchell, Thomas M.; Brown, Murray

The Minerals Management Service (MMS), Gulf of Mexico Outer Continental Shelf (OCS) Region sponsored a symposium on the Physical Oceanography of the Louisiana/Texas (LA/TX) Shelf in Galveston, Texas, on May 24-26, 1988. The symposium brought together a number of physical oceanographers, meteorologists, and ecologists to discuss the state of knowledge and to begin the planning process for a long-term study of shelf circulation covering the region from the mouth of the Mississippi River to approximately 24° latitude along the Mexican coast and from the shore out to a depth of approximately 500 m. The proposed study, to be a component of the ongoing MMS Environmental Studies Program, is expected to take place during the period 1989-1991. It is anticipated that the work will be done principally through contracts after a competitive procurement process. Specific charges to the participants were as follows:to assess the current state of knowledge concerning the circulation on the LA/TX shelfto identify significant gaps in that knowledgeto recommend a field measurement program to address these gapsto recommend a circulation modeling program for the LA/TX shelf that will improve MMS' oil spill risk assessmentsto identify and initiate coordination mechanisms and data-sharing arrangements with other proposed research efforts

Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

USGS Publications Warehouse

Evans, Kevin R.; Carlson, Paul R.; Hampton, Monty A.; Marlow, Michael S.; Barnes, Peter W.

2000-01-01

Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea floor structures. Sea-floor sediment on shallow banks is eroded by seasonal wave-generated currents. The winnowing action of the large storm waves results in concentrations of gravel over broad segments of the Kodiak shelf. Northeastern Gulf of Alaska -- Tectonic framework studies demonstrate that rocks of distant origin (Yakutat terrane) are currently attached to and moving with the Pacific Plate, as it collides with and is subducted beneath southern Alaska. This collision process has led to pronounced structural deformation of the continental margin and adjacent southern Alaska. Consequences include rapidly rising mountains and high fluvial and glacial sedimentation rates on the adjacent margin and ocean floor. The northeastern Gulf of Alaska shelf also has concentrations of winnowed (lag) gravel on Tarr Bank and on the outer shelf southeast of Yakutat Bay. Between Kayak Island and Yakutat Bay the outer shelf consists of pebbly mud (diamict). This diamict is a product of glacial marine sedimentation during the Pleistocene and is present today as a relict sediment. A prograding wedge of Holocene sediment consisting of nearshore sand grading seaward into clayey silt and silty clay covers the relict pebbly mud to mid-shelf and beyond. Shelf and slope channel systems transport glacially derived sediment across the continental margin into Surveyor Channel, an abyssal fan and channel system that reaches over 1,000 km to the Aleutian Trench.

78 FR 24731 - Taking Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to an...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-26

... Drilling Program in the Chukchi Sea, Alaska AGENCY: National Marine Fisheries Service (NMFS), National... conducting offshore exploration drilling on Outer Continental Shelf (OCS) leases in the Chukchi Sea, Alaska... incidental to COP's offshore exploration drilling in the Chukchi Sea during the 2014 open- [[Page 24732...

Implementation of Real-Time Bias-Adjusted O3 and PM2.5 Air Quality Forecasts and their Performance Evaluations during 2008 over the Continental United States

EPA Science Inventory

The National Oceanic and Atmospheric Administration (NOAA), in partnership with the United States Environmental Protection Agency (EPA), is operationally implementing an Air Quality Forecast (AQF) system. This program, which couples NOAA's North American Mesoscale (NAM) weather p...

30 CFR 252.6 - Freedom of Information Act requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Freedom of Information Act requirements. 252.6... CONTINENTAL SHELF (OCS) OIL AND GAS INFORMATION PROGRAM § 252.6 Freedom of Information Act requirements. (a... to the limitations of the Freedom of Information Act (5 U.S.C. 552), the regulations contained in 43...

78 FR 60892 - Outer Continental Shelf (OCS), Alaska OCS Region, Chukchi Sea Planning Area, Proposed Oil and Gas...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-10-02

..., concerning the importance of these areas or associated activities. 6. Submissions of Nominations, Requests... range of interest classifications and anticipated activity regarding the nominated area(s). Interested... on the importance of Hanna Shoal and Herald Shoal. While already excluded from the Program Area...

40 CFR 55.4 - Requirements to submit a notice of intent.

Code of Federal Regulations, 2011 CFR

2011-07-01

... intent. 55.4 Section 55.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) OUTER CONTINENTAL SHELF AIR REGULATIONS § 55.4 Requirements to submit a notice of... Regional Office, and at the same time shall submit copies of the NOI to the air pollution control agencies...

40 CFR 55.4 - Requirements to submit a notice of intent.

Code of Federal Regulations, 2010 CFR

2010-07-01

... intent. 55.4 Section 55.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) OUTER CONTINENTAL SHELF AIR REGULATIONS § 55.4 Requirements to submit a notice of... Regional Office, and at the same time shall submit copies of the NOI to the air pollution control agencies...

40 CFR 55.4 - Requirements to submit a notice of intent.

Code of Federal Regulations, 2014 CFR

2014-07-01

... intent. 55.4 Section 55.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) OUTER CONTINENTAL SHELF AIR REGULATIONS § 55.4 Requirements to submit a notice of... Regional Office, and at the same time shall submit copies of the NOI to the air pollution control agencies...

40 CFR 55.4 - Requirements to submit a notice of intent.

Code of Federal Regulations, 2012 CFR

2012-07-01

... intent. 55.4 Section 55.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) OUTER CONTINENTAL SHELF AIR REGULATIONS § 55.4 Requirements to submit a notice of... Regional Office, and at the same time shall submit copies of the NOI to the air pollution control agencies...

40 CFR 55.4 - Requirements to submit a notice of intent.

Code of Federal Regulations, 2013 CFR

2013-07-01

... intent. 55.4 Section 55.4 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) OUTER CONTINENTAL SHELF AIR REGULATIONS § 55.4 Requirements to submit a notice of... Regional Office, and at the same time shall submit copies of the NOI to the air pollution control agencies...

Surface atmospheric extremes (launch and transportation areas)

NASA Technical Reports Server (NTRS)

1974-01-01

Criteria are provided on atmospheric extremes from the surface to 150 meters for geographical locations of interest to NASA. Thermal parameters (temperature and solar radiation), humidity, precipitation, pressure, and atmospheric electricity (lightning and static) are presented. Available data are also provided for the entire continental United States for use in future space programs.

30 CFR 250.1915 - What training criteria must be in my SEMS program?

Code of Federal Regulations, 2014 CFR

2014-07-01

..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Safety... protection of the environment, and ensure that persons assigned to operate and maintain the facility possess... operating procedures, using periodic drills, to verify adequate retention of the required knowledge and...

30 CFR 250.1911 - What criteria for hazards analyses must my SEMS program meet?

Code of Federal Regulations, 2012 CFR

2012-07-01

..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Safety...., mobile offshore drilling units; floating production systems; floating production, storage and offloading... transportation activities for oil, gas, or sulphur from areas leased in the OCS. Facilities also include DOI...

30 CFR 250.1915 - What criteria for training must be in my SEMS program?

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL... training for the basic well-being of personnel and protection of the environment, and ensure that persons... understanding of, and adherence to, the current operating procedures, using periodic drills, to verify adequate...

30 CFR 250.1915 - What criteria for training must be in my SEMS program?

Code of Federal Regulations, 2012 CFR

2012-07-01

..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Safety... of personnel and protection of the environment, and ensure that persons assigned to operate and... to, the current operating procedures, using periodic drills, to verify adequate retention of the...

30 CFR 250.1915 - What training criteria must be in my SEMS program?

Code of Federal Regulations, 2013 CFR

2013-07-01

..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Safety... protection of the environment, and ensure that persons assigned to operate and maintain the facility possess... operating procedures, using periodic drills, to verify adequate retention of the required knowledge and...

78 FR 25100 - Outer Continental Shelf Scientific Committee; Announcement of Plenary Session

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-29

... the feasibility, appropriateness, and scientific value of the OCS Environmental Studies Program to the Secretary of the Interior through the Director of BOEM. The SC will review the relevance of the research and... will be an update from each region's Environmental Studies Chief on OCS activities and current issues...

Economic analysis of light brown apple moth using GIS and quantitative modeling

Treesearch

Glenn Fowler; Lynn Garrett; Alison Neeley; Roger Magarey; Dan Borchert; Brian Spears

2011-01-01

We conducted an economic analysis of the light brown apple moth (LBAM), (piphyas postvittana (Walker)), whose presence in California has resulted in a regulatory program. Our objective was to quantitatively characterize the economic costs to apple, grape, orange, and pear crops that would result from LBAM's introduction into the continental...

75 FR 63609 - Oil and Gas and Sulphur Operations in the Outer Continental Shelf-Safety and Environmental...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-15

... safety of the offshore facility, including ensuring that all contractors and subcontractors have safety... safety analysis (task level); (3) Procedures to verify that contractors are conducting their activities in accordance with the operator's SEMS program and an evaluation to ensure that contractors have the...

Determining the size of a complete disturbance landscape: multi-scale, continental analysis of forest change

Treesearch

Brian Buma; Jennifer K Costanza; Kurt Riitters

2017-01-01

The scale of investigation for disturbanceinfluenced processes plays a critical role in theoretical assumptions about stability, variance, and equilibrium, as well as conservation reserve and long-term monitoring program design. Critical consideration of scale is required for robust planning designs, especially when anticipating future disturbances whose exact...

The effect of plumes and a free surface on mantle dynamics with continents and self-consistent plate tectonics

NASA Astrophysics Data System (ADS)

Jain, Charitra; Rozel, Antoine; Tackley, Paul

2014-05-01

Rolf et al. (EPSL, 2012) and Coltice et al. (Science, 2012) investigated the thermal and dynamical influences of continents on plate tectonics and the thermal state of Earth's mantle, but they did not explicitly consider the influence of mantle plumes. When present, strong mantle plumes arising from the deep mantle can impose additional stresses on the continents, thereby facilitating continental rifting (Storey, Nature 1995; Santosh et al., Gondwana Research 2009) and disrupting the supercontinent cycle (Philips and Bunge, Geology 2007). In recent years, several studies have characterized the relation between the location of the plumes and the continents, but with contradicting observations. While Heron and Lowman (GRL, 2010; Tectonophysics, 2011) propose regions where downwelling has ceased (irrespective of overlying plate) as the preferred location for plumes, O'Neill et al. (Gondwana Research, 2009) show an anti-correlation between the average positions of subducting slabs at continental margins, and mantle plumes at continental/oceanic interiors. Continental motion is attributed to the viscous stresses imparted by the convecting mantle and the extent of this motion depends on the heat budget of the mantle. Core-mantle boundary (CMB) heat flux, internal heating from decay of radioactive elements, and mantle cooling contribute to this heat budget. Out of these sources, CMB heat flux is not well defined; however, the recent determination that the core's thermal conductivity is much higher than previously thought requires a CMB heat flow of at least 12 TW (de Koker et al., PNAS 2012; Pozzo et al., Nature 2012; Gomi et al., PEPI 2013), much higher than early estimates of 3-4 TW (Lay et al., Nature 2008). Thus, it is necessary to characterize the effect of increased CMB heat flux on mantle dynamics. In almost all mantle convection simulations, the top boundary is treated as a free-slip surface whereas Earth's surface is a deformable free surface. With a free-slip boundary condition, the uppermost part of the model is not allowed to move vertically. In contrast, a free surface boundary condition allows for the development of topography and leads to realistic single-sided (asymmetric) subduction (Crameri et al., GJI 2012; Crameri et al., GRL 2012). A free-slip surface may also create incorrect stresses in the model continents, forcing them to spread horizontally along the boundary to minimize the gravitational potential. This is something we aim to test here. Here, we test (i) the impact of increased basal heating on mantle dynamics with continents and self-consistent plate tectonics, including whether plumes prefer to develop under continents; (ii) the influence of a free surface on continents in the context of self-consistent plate tectonics. The existing model from Rolf et al. (EPSL 2012) is developed further but with weaker continents. A 'sticky-air' approach is used, in which a low density and a small viscosity fluid layer is added to the top of the model. We study these using StagYY code (Tackley, PEPI 2008), which uses a finite-volume discretization, a multigrid solver to obtain a velocity-pressure solution at each timestep on a staggered grid and tracers to track composition.

Birch Lecture : The Deep Roots of Continents

NASA Astrophysics Data System (ADS)

Jaupart, C.

2006-12-01

The roots of Archean continents are made of depleted and buoyant mantle and may extend to depths larger than 250 km. Such distinctive characteristics have key dynamical and geological consequences that we are only beginning to address. Thick roots provide large volume repositories for chemical elements that do not mix with Earth's convecting interior. Their large diffusive relaxation time implies long-term thermal disequilibrium with their radioactive heat sources and with the cooling of the mantle. Their negative thermal buoyancy may drive convective instabilities with implications for intracontinental deformation and magmatism as well as for continental growth. The dynamical behaviour of continental roots depends on the buoyancy ratio B, the ratio of the intrinsic (chemical) buoyancy of depleted lithospheric mantle and the density difference due to thermal expansion. The lithosphere can be mechanically stable and in thermal equilibrium with heat supplied by small-scale convection at the top of the asthenosphere. Sufficient cooling may result in an oscillatory convective instability whereby perturbations to the base of the lithosphere rise and fall periodically. The lithosphere seems to have developed in a state near that of instability with different thicknesses depending on its intrinsic buoyancy. It may have grown not only by chemical differentiation during melting, but also by oscillatory convection entraining chemically denser material from the asthenosphere. Mantle plumes have different effects on lithospheres of different thicknesses and compositions. For B values larger than about 0.6, plume material does not really penetrate into the lithosphere and spreads beneath it. In this case, the buoyancy force that is applied to the base of the lithosphere drives moderate thinning and extension over large horizontal distances. It takes values of B less than 0.6 to achieve true plume penetration with a significant vertical velocity component. In this case, thinning and extension get localized above the rising plume. In both cases, heated lithosphere material becomes convectively unstable after some time and entrains asthenospheric material as it rises. Temperatures in thick continental lithosphere do not adjust rapidly to secular changes of mantle temperature. Analysis of (P,T) data from xenolith studies indicates that the Earth's mantle has cooled at a rate of 80 K Ga-1 or less. Thick continental roots preserve a record of Archean processes and of Earth's evolution through geological ages. Deciphering this record may well be our next challenge.

Transfer of New Earth Science Understandings to Classroom Teaching: Lessons Learned From Teachers on the Leading Edge

NASA Astrophysics Data System (ADS)

Butler, R.; Ault, C.; Bishop, E.; Southworth-Neumeyer, T.; Magura, B.; Hedeen, C.; Groom, R.; Shay, K.; Wagner, R.

2006-05-01

Teachers on the Leading Edge (TOTLE) provided a field-based teacher professional development program that explored the active continental margin geology of the Pacific Northwest during a two-week field workshop that traversed Oregon from the Pacific Coast to the Snake River. The seventeen teachers on this journey of geological discovery experienced regional examples of subduction-margin geology and examined the critical role of geophysics in connecting geologic features with plate tectonic processes. Two examples of successful transfer of science content learning to classroom teaching are: (1) Great Earthquakes and Tsunamis. This topic was addressed through instruction on earthquake seismology; field observations of tsunami geology; examination of tsunami preparedness of a coastal community; and interactive learning activities for children at an Oregon Museum of Science and Industry (OMSI) Science Camp. Teachers at Sunnyside Environmental School in Portland developed a story line for middle school students called "The Tsunami Hotline" in which inquiries from citizens serve as launch points for studies of tsunamis, earthquakes, and active continental margin geology. OMSI Science Camps is currently developing a new summer science camp program entitled "Tsunami Field Study" for students ages 12-14, based largely on TOTLE's Great Earthquakes and Tsunamis Day. (2) The Grand Cross Section. Connecting regional geologic features with plate tectonic processes was addressed many times during the field workshop. This culminated with teachers drawing cross sections from the Juan de Fuca Ridge across the active continental margin to the accreted terranes of northeast Oregon. Several TOTLE teachers have successfully transferred this activity to their classrooms by having student teams relate earthquakes and volcanoes to plate tectonics through artistic renderings of The Grand Cross Section. Analysis of program learning transfer to classroom teaching (or lack thereof) clearly indicates the importance of pedagogical content knowledge and having teachers share their wisdom in crafting new earth science content knowledge into learning activities. These lessons and adjustments to TOTLE program goals and strategies may be valuable to other Geoscience educators seeking to prepare K-12 teachers to convey the discoveries of EarthScope's USArray and Plate Boundary Observatory experiments to their students.

Scientific Drilling in the Snake River Plain: Past, Present, and Future

NASA Astrophysics Data System (ADS)

Shervais, J. W.; Hanan, B. B.; Hughes, S. S.; Geist, D.; Vetter, S. K.

2006-12-01

The Snake River-Yellowstone volcanic province has long been linked to the concept of lithospheric drift over a fixed mantle thermal anomaly or hotspot. This concept is reinforced by seismic tomography that images this anomaly to depths around 500 km, but alternative proposals still present a serious challenge. Basaltic volcanism spans a significant age range and basaltic volcanism in the western SRP lies well off the hotspot track and cannot be related directly to the hotspot in any simple way. The plume-track age progression is documented by rhyolite volcanic centers, but even these represent extended time periods that overlap in age with adjacent centers. Scientific drilling projects carried out over the last two decades have made significant contributions to our understanding of both basaltic and rhyolitic volcanism associated with the Snake River-Yellowstone hotspot system. Because these drill holes also intercept sedimentary interbeds or, in the case of the western SRP, thick sections of Pliocene and Pleistocene sediments, they have also contributed to our understanding of basin formation by thermal collapse in the wake of the hotspot passage or by rifting, paleoclimate of the interior west, and groundwater systems in volcanic rocks. Many of these drill holes are associated with the Idaho National Laboratory (INL) in the eastern plain; others were drilled for geothermal or petroleum exploration. The latter include older holes that were not instrumented or logged in detail, but which still provide valuable stratigraphic controls. We focus here on the result of basalt drilling, which have been high-lighted in recent publications. Basaltic volcanism in the Snake River plain is dominated by olivine tholeiites that have major and trace element characteristics of ocean island basalt: the range in MgO is similar to MORB, but Ti, Fe, P, K, Sr, Zr and LREE/HREE ratios are all higher. Recent studies of basalts from the drill holes show that they evolved by fractionation in a mid-crustal sill complex that has been imaged seismically. Further, the chemical and isotopic systematics of these basalts require assimilation of consanguineous mafic material inferred to represent previously intruded sills. Major and trace element modeling suggest formation of the primary melts by melting of a source similar to E- MORB source. Trace element systematics document mixing between a plume-like source and a more depleted source that is not DMM. A similar more depleted source is inferred for Hawaii, suggesting that it is not continental lithosphere. Future scientific drilling in the SRP is the focus of Project HOTSPOT, a multi-disciplinary initiative that seeks to document time-space variations in the SRP-Yellowstone volcanic system. A workshop sponsored by the International Continental Drilling Program was held in May 2006 to develop a targeted program of scientific drilling that examines the entire plume-lithosphere system across a major lithospheric boundary, with holes targeting basalt, rhyolite, and sediments. These drill holes will complement geophysical studies of continental dynamics (e.g., Earthscope), as well as current studies centered on Yellowstone. Additional components of a targeted drilling program include studies of lacustrine sediments that document paleoclimate change in North America during the Pliocene—Pleistocene and fluid flow at deeper crustal levels.

Sediment dynamics and post-glacial evolution of the continental shelf around the Blanes submarine canyon head (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Durán, Ruth; Canals, Miquel; Lastras, Galderic; Micallef, Aaron; Amblas, David; Pedrosa-Pàmies, Rut; Sanz, José Luis

2013-11-01

The Blanes submarine canyon (BC) deeply incises the Catalan continental shelf in the NW Mediterranean Sea. As a consequence of the closeness (only 4 km) of its head to the coastline and the mouth of the Tordera River, the canyon has a direct influence on the shelf dispersal system as it collects large amounts of sediment, mainly during high-energy events. Multibeam bathymetry, backscatter imagery and very-high resolution seismic reflection profiles have allowed characterizing the morphology of the continental shelf around the canyon head, also identifying sediment sources and transport pathways into the canyon. The morphological data have also been used to reconstruct the evolution of the continental shelf during the last sea-level transgression so that the current understanding of shelf-to-canyon sediment exchanges through time could be improved. The continental shelf surrounding the BC consists of both depositional and erosional or non-depositional areas. Depositional areas display prominent sediment bodies, a generally smooth bathymetry and variable backscatter. These include: (i) an area of modern coarse-grained sediment accumulation that comprises the inner shelf; (ii) a modern fine-grained sedimentation area on the middle shelf offshore Tossa de Mar; and (iii) a modern sediment depleted area that covers most of the middle and outer shelf to the west of the canyon head. Erosional and non-depositional areas display a rough topography and high backscatter, and occur primarily to the east of the canyon head, where the arrival of river-fed inputs is very small. In agreement with this pattern, the continental shelf north and west of the canyon head likely is the main source of shelf sediment into the canyon. To the north, a pattern of very high backscatter extends from the coastline to the canyon head, suggesting the remobilization and off-shelf export of fines. Additionally, relict near-shore sand bodies developed over the Barcelona shelf that extend to the canyon head rim constitute a source of coarse sediment. High-energy processes, namely river floods and coastal storms, are the main controls over the river-shelf-canyon sediment exchange. River floods increase the delivery of terrigenous particles to the coastal system. Storms, mainly from the east, remobilize the sediment temporarily accumulated on the shelf towards the canyon head, so that the finer fractions are preferentially removed and a coarse lag is normally left on the shelf floor. Exceptionally, very strong storms also remove the coarse fractions from the shelf drive them into the canyon. Processes like dense shelf water cascading, which is much more intense in canyons to the north of BC, and the Northern Current also contribute to the transport of suspended sediment from far distant northern sources. During the last post-glacial transgression the BC had a strong influence on the evolution of the inner continental margin, as it interrupted the shelf sediment dispersal system by isolating the shelves to its north and south, named La Planassa and Barcelona shelves, respectively. The detailed study of the geomorphology and uppermost sediment cover of the continental shelf surrounding the Blanes submarine canyon yields insight into the past and present shelf sediment dynamics and the shelf-to-canyon sediment exchanges. The continental shelf near the canyon head consists of mosaic where erosional, or non-depositional, and depositional zones coexist. East of the canyon and offshore Tossa de Mar, the modern sediment deposition is mostly confined to the inner and middle shelf, whilst most of the La Planassa shelf is sediment depleted with numerous relict morphosedimentary features cropping out. Rocky outcrops, narrow ridges and relict coarse sand deposits suggesting erosion or non-deposition of fine sediments in modern times occupy the middle and outer shelf floor east and northeast of the canyon head. In contrast, north and west of the canyon head, the middle and outer shelf comprises several large relict sand bodies that point out to long-term deposition. However, the lack of modern sediments on top of these bodies supports active erosion or by-pass in present times. The morphology of the continental shelf near the canyon head records the imprint of the main factors controlling the shelf sediment-dispersal system and provides evidence for the main sources and transport pathways of sediment from the shelf into the canyon. The depletion of fine sediments on the continental shelf, as evidenced by backscatter data, suggests that the Blanes Canyon acts as a sediment trap collecting the finest fractions resuspended primarily from the adjacent shelf to the north. The main processes that control the shelf-to-canyon transfer of sediment are eastern storms, which enhance the off-shelf export of mainly fine sediment from the shelf. Particularly severe storms are also able to remobilize and transport coarse sediment from the shelf and also from the relict sand bodies into the canyon. Other processes, such as DSWC and the Northern Current, contribute to a lesser extent to the transport of sediment along the shelf and into the canyon. During the last post-glacial transgression, the BC played a crucial role in the shaping of the continental shelf surrounding it by cutting the littoral drift of sediment between the shelf areas to the north and south, thus severely modifying the across- and along-shelf sediment pathways. As a result, to the east of the canyon, the poor development of transgressive deposits indicates the prevalence of erosion and non-deposition associated to a limited sediment supply and an effective action of the littoral drift leading to a south-westward transport of sediment towards the canyon head. To the north and west of the canyon the morphology of the continental shelf changed significantly during the sea-level rise. At the early stage of the transgression, the sediment supplied by the Tordera River was discharged directly into the canyon, thus preventing deposition over the shelf. Later, the progressive sea-level rise favoured the development of large depositional bodies on the Barcelona shelf favoured by the increase of accommodation space and the augmenting distance between the river mouth and the canyon head. A drastic change in the configuration of the shelf occurred when the sea-level raised enough to flood the entire continental shelf. The along-shelf sediment transport between the shelf areas to the north and south of the canyon head was then restored and new sediment bodies were formed between the coastline and the canyon tip. At present, these sediment bodies constitute the primary source of coarse sediment into the BC. These results confirm that the Blanes submarine canyon head is highly dynamic and sensitive to a variety of processes that enhance the transport of sediment from the shelf into the canyon, particularly during major storms.

Sandwave Morphologies and Dynamics in a Continental Shelf Environment : Example of the Banc du Four (western Brittany, France)

NASA Astrophysics Data System (ADS)

Franzetti, M.; Garlan, T.; Le Roy, P.; Delacourt, C.; Cancouët, R.; Graindorge, D.; Deschamps, A.

2011-12-01

Marine sand dunes and sandbanks are mainly observed in continental tidal shelves (North Sea, South China Sea, North Atlantic America) and may be highly dynamic (for example up to 75 m/y in the Marsdiep inlet). So they may pose a potential risk to offshore installations and shipping. Multitemporal mapping of sandwaves, necessary to mitigate this hazard, is complicated by their dynamic character, which is still poorly understood especially in the offshore domain. In consequence, these structures are often defined as moribund at depths greater than 30 meters. The aim of this investigation is to study evolution of deeper (110 meters) complex set of sand bedforms : "Banc du Four" located in the Iroise Sea. The study area is exposed to strong tidal currents and storm waves at the junction of the Northeast Atlantic Ocean and the Western English Channel, conditions favorable to sediment dynamics. The bathymetric data, which form the basis of this study, are two Digital Terrain Modeling's (DTM's) derived from MultiBeam Echosounder (MBES) surveys : "Pourquoi-Pas?" oceanographic research vessel (R/V) in February 2009 (5 meters resolution DTM) and R/V "Albert Lucas" in August 2010 (2 meters resolution DTM). Sandwave parameters (water depth, shape, wavelength, height, symmetry index, ...) have been derived from the 2009 bathymetric data. The Banc du Four is characterized by a large sandbank (45 meters height and 2 km width) flanked by dune fields. The morphological characteristics of the dunes vary greatly (range 30 to 110 meters depth, 40 meters maximal height, 600 meters maximal width, symmetrical to asymmetrical, ...). However, this complexity can be explained by the involved sandwave dynamic (range 0 to 30 meters per year migration velocity). Spatial correlation method, applied on the two DTM's, are used to measure the migration rate. The high migration rates for deeper giant dunes bring to light the dynamic sandwave existence at depths exceeding 30-40 meters, contrary to previously accepted models. Dune asymmetry is proportional to migration rates and the lee side is always oriented towards the direction of movement. These relationships confirm the observations reported in the literature for shallower structures.

Crustal Structure of the Yakutat Microplate: Constraints from STEEP Wide-angle Seismic Data

NASA Astrophysics Data System (ADS)

Christeson, G. L.; van Avendonk, H.; Gulick, S. P.; Worthington, L.; Pavlis, T.

2008-12-01

In Fall 2008 we will conduct a seismic program focusing on the Yakutat microplate. As part of this study we plan to acquire two wide-angle profiles: an onshore-offshore northwest-southeast oriented profile extending from the Bering glacier onto the continental shelf and across the Dangerous River Zone, and an offshore northeast-southwest oriented profile extending from the ocean basin across the Transition fault and into Yakutat Bay. The sound source will be the R/V Langseth's tuned 6600 cu. in., 36 air gun array. Ocean bottom seismometers will be positioned at ~15 km spacing, and Texan seismometers at 1-4 km spacing across the Bering Glacier. Coincident deep-penetrating seismic reflection data will be acquired on the marine portion of both profiles using a 8-km, 640-channel solid hydrophone streamer. Existing models for the Yakutat microplate disagree as to whether it is a continental fragment attached to normal oceanic crust or an oceanic plateau, and if the deep structure changes from west to east across the Dangerous River Zone. In the continental fragment model uplift is concentrated along crustal-scale thrust faulting at the ocean crust boundary (Dangerous River Zone?) resulting in focused and rapid erosion. In the oceanic plateau model more distributed, regional uplift is expected which will produce widespread exhumation with net erosion potentially coupled with glacial cycles. Thus distinguishing between these models, which we expect to accomplish with our planned seismic program, is vital for linking tectonics to erosion on both spatial and temporal scales.

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE PAGES

Jensen, M. P.; Petersen, W. A.; Bansemer, A.; ...

2015-12-18

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms -1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

The Midlatitude Continental Convective Clouds Experiment (MC3E)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, M. P.; Petersen, W. A.; Bansemer, A.

The Midlatitude Continental Convective Clouds Experiment (MC3E), a field program jointly led by the U.S. Department of Energy’s Atmospheric Radiation Measurement program and the NASA Global Precipitation Measurement (GPM) Mission, was conducted in south-central Oklahoma during April – May 2011. MC3E science objectives were motivated by the need to improve understanding of midlatitude continental convective cloud system lifecycles, microphysics, and GPM precipitation retrieval algorithms. To achieve these objectives a multi-scale surface- and aircraft-based in situ and remote sensing observing strategy was employed. A variety of cloud and precipitation events were sampled during the MC3E, of which results from three deepmore » convective events are highlighted. Vertical structure, air motions, precipitation drop-size distributions and ice properties were retrieved from multi-wavelength radar, profiler, and aircraft observations for an MCS on 11 May. Aircraft observations for another MCS observed on 20 May were used to test agreement between observed radar reflectivities and those calculated with forward-modeled reflectivity and microwave brightness temperatures using in situ particle size distributions and ice water content. Multi-platform observations of a supercell that occurred on 23 May allowed for an integrated analysis of kinematic and microphysical interactions. A core updraft of 25 ms -1 supported growth of hail and large rain drops. As a result, data collected during the MC3E campaign is being used in a number of current and ongoing research projects and is available through the DOE ARM and NASA data archives.« less

Paleoclimate: A fresh look at glacial floods

USGS Publications Warehouse

Colman, S. M.

2002-01-01

Over the last 20 years, it has become clear that ice ages are characterized by glacial as well as climatic instability on millennial time scales. In his Perspective, Colman highlights two recent papers investigating the role of glacial meltwater and continental drainage in this instability. The results suggest a fundamental instability feedback between ocean circulation and ice sheet dynamics and provides an explanation for why instability was greatest at times of intermediate ice volume.

A fresh look at glacial foods

USGS Publications Warehouse

Colman, Steven M.

2002-01-01

Over the last 20 years, it has become clear that ice ages are characterized by glacial as well as climatic instability on millennial time scales. In his Perspective, Colman highlights two recent papers investigating the role of glacial meltwater and continental drainage in this instability. The results suggest a fundamental instability feedback between ocean circulation and ice sheet dynamics and provides an explanation for why instability was greatest at times of intermediate ice volume.

The Numerical Solution of Acoustic Propagation through Dispersive Moving Media

DTIC Science & Technology

2010-06-01

environments. The benthic nepheloid layer ( BNL ) is an example of a moving turbid water layer in the ocean. The BNL is characterized by changing vertical...this change. There are however situations where this assumption doesn’t hold. For example when a benthic nepheloid layer ( BNL ) is present. A BNL is...shoaling and breaking of internal waves on the continental shelf. The BNL is dynamic, characterized by changing vertical thickness, concentration and

OCS National Compendium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gould, G.J.; Karpas, R.M.; Slitor, D.L.

1991-06-01

The Minerals Management Service's (MMS) Outer Continental Shelf Information Program (OCSIP) is responsible for making available to affected coastal States, local governments, and other interested parties data and information related to the Outer Continental Shelf (OCS) Oil and Gas Program. Since its establishment through Section 26 of the OCS Lands Act (OCSLA) Amendments of 1978, OCSIP has prepared regional summary reports, updates, and indexes on leasing, exploration, development, and production activities to fulfill the mandates of the OCSLA Amendments. The OCSIP receives many requests for out-of-print summary reports, updates, and indexes. The purpose of the OCS National Compendium is tomore » consolidate these historical data and to present the data on an OCS-wide and regional scale. The single-volume approach allows the reader access to historical information and facilitates regional comparisons. The fold-out chart in the front of this publication provides the reader with a timeline (January 1988--November 1990) of events since publication of the last Compendium. Some of the events are directly related to the 5-year Oil and Gas Program, whereas others may or may not have an effect on the program. A predominantly graphic format is used in the report so that the large accumulation of data can be more readily comprehended. In some cases, it is not possible to update information through October 21, 1990, because of the nature of the data. For example, production data normally lags 3 months. 58 figs., 37 tabs.« less

Miocene tectonics of the Western Alboran domain: from mantle extensional exhumation to westward thrusting

NASA Astrophysics Data System (ADS)

Gueydan, F.; Frasca, G.; Brun, J. P.

2015-12-01

In the frame of the Africa-Europe convergence, the Mediterranean tectonic system presents a complex interaction between subduction rollback and upper-plate deformation during the Tertiary. The western Mediterranean is characterized by the exhumation of the largest subcontinental mantle massif worldwide (the Ronda Peridotite) and a narrow arcuate geometryacross the Gibraltar arc within the Betic-Rif belt (the internal part being called the Alboran domain), where the relationship between slab dynamics and surface tectonics is not well understood. New structural and geochronological data are used to argue for 1/ hyperstrechting of the continental lithosphere allowing extensional mantle exhumation to shallow depths, followed by 2/ lower miocene thrusting. Two Lower Miocene E-W-trending strike-slip corridors played a major role in the deformation pattern of the Alboran Domain, in which E-W dextral strike-slip faults, N60°-trending thrusts and N140°-trending normal faults developed simultaneously during dextral strike-slip simple shear. The inferred continuous westward translation of the Alboran Domain is accommodated by a major E-W-trending lateral ramp (strike-slip) and a N60°-trending frontal thrust. At lithosphere-scale, we interpret the observed deformation pattern as the upper-plate expression of a lateral slab tear and of its westward propagation since Lower Miocene. The crustal emplacement of the Ronda Peridotites occurred at the onset of this westward motion.The Miocene tectonics of the western Alboran is therefore marked by the inversion of a continental rift, triggered by shortening of the upper continental plate and accommodated by E-W dextral strike-slip corridors. During thrusting and westward displacement of the Alboran domain with respect to Iberia, the hot upper plate, which involved the previously exhumed sub-continental mantle, underwent fast cooling.

A numerical study of aerosol effects on the dynamics and microphysics of a deep convective cloud in a continental environment

NASA Astrophysics Data System (ADS)

Cui, Zhiqiang; Carslaw, Kenneth S.; Yin, Yan; Davies, Stewart

2006-03-01

The effects of aerosols on a deep convective cloud in a midlatitude continental environment are studied using an axisymmetric cloud model with a sectional treatment of aerosol and hydrometeor microphysical processes. Simulations are conducted using observations from the Cooperative Convective Precipitation Experiments (CCOPE). The isolated cloud occurred in an environment with low wind shear and with relatively dry air in the midtroposphere and upper troposphere. By varying the concentration of aerosol particles in the accumulation mode within realistic limits for a continental environment, the simulated cloud exhibited different properties. The overall impact as the aerosol concentration increased is that (1) the cloud development was inhibited; (2) the precipitation was suppressed; (3) the maximum values of liquid water content decreased, but the maximum values of droplet number concentration increased before the dissipating stage; (4) a clear tendency was found for ice crystals to be larger and less numerous in the anvil cloud; and (5) there was a significant reduction of the inflow in the lower 2 km of the atmosphere. In the relatively dry environment in the midtroposphere, the latent heat changes associated with the Wegener-Bergeron-Findeisen mechanism played an important role in the upper part of the cloud at altitudes below the homogeneous freezing level. In particular, immersion freezing and latent heat release were much more rapid in the base simulation than in the increased aerosol simulation. Less latent heat release and insufficient inflow together impeded the development of the cloud with the higher aerosol loading. Our simulations suggest that continental clouds existing below the homogeneous freezing level could show an opposite response of cloud top height and anvil crystal concentrations to changes in aerosol to what has previously been reported for clouds ascending to higher levels.

Assessment of submarine landslides hazard through geotechnical and rheological analysis of sediments on the French Atlantic continental slope

NASA Astrophysics Data System (ADS)

Toucanne, S.; Howlett, S.; Garziglia, S.; Silva Jacinto, R.; Courgeon, S.; Sabine, M.; Riboulot, V.; Marsset, B.

2016-12-01

In the aftermath of the devastating tsunami on the Japanese coast in 2011, a French multi-partnership project called TANDEM has been launched to assess the impact of tsunamis generated or propagated in the vicinity of French Channel and Atlantic coastlines. Tsunami are usually generated by earthquakes, but can also be triggered by submarine landslides. This study focuses on submarine landslides along the French Atlantic continental slope using data that were mainly collected in August 2015 during the GITAN cruise (R/V Pourquoi Pas?). Following geomorphological, geophysical and sedimentological analysis of the Bay of Biscay, efforts were oriented towards the determination of the sediment properties controlling landslide dynamics from in situ and laboratory measurements. Preliminary results show over 700 landslide scars on the French Atlantic continental slope, with most of them occurring between 400 and 1000m water depth and in canyon environments. The Plio-Quaternary sediments draping the majority of the Bay of Biscay are generally normally consolidated and composed of high plasticity clays. They show similar geomechanical properties throughout the area studied, with linear evolutions with depth and good reproducibility for rheological parameters such as Storage and Loss modulus. These similarities allow to extend geotechnical and rheological models to a regional scale in the Bay of Biscay. Our multi-disciplinary approach will provide the tools to assess continental slope failures and submarine landslides generation. Finally, we will aim to qualify and quantify the volumes and flow properties of sediment transported obtained through slope-stability modeling on SAMU-3D and rheology modelling on Nixes-SPH. These results will provide the TANDEM actors with the information necessary to simulate tsunami wave generation.

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.

High Resolution Land Use Land Cover Classification using Landsat Earth Observation Data for the Continental Africa

NASA Astrophysics Data System (ADS)

Midekisa, A.; Bennet, A.; Gething, P. W.; Holl, F.; Andrade-Pacheco, R.; Savory, D. J.; Hugh, S. J.

2016-12-01

Spatially detailed and temporally dynamic land use land cover data is necessary to monitor the state of the land surface for various applications. Yet, such data at a continental to global scale is lacking. Here, we developed high resolution (30 meter) annual land use land cover layers for the continental Africa using Google Earth Engine. To capture ground truth training data, high resolution satellite imageries were visually inspected and used to identify 7, 212 sample Landsat pixels that were comprised entirely of one of seven land use land cover classes (water, man-made impervious surface, high biomass, low biomass, rock, sand and bare soil). For model validation purposes, 80% of points from each class were used as training data, with 20% withheld as a validation dataset. Cloud free Landsat 7 annual composites for 2000 to 2015 were generated and spectral bands from the Landsat images were then extracted for each of the training and validation sample points. In addition to the Landsat spectral bands, spectral indices such as normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were used as covariates in the model. Additionally, calibrated night time light imageries from the National Oceanic and Atmospheric Administration (NOAA) were included as a covariate. A decision tree classification algorithm was applied to predict the 7 land cover classes for the periods 2000 to 2015 using the training dataset. Using the validation dataset, classification accuracy including omission error and commission error were computed for each land cover class. Model results showed that overall accuracy of classification was high (88%). This high resolution land cover product developed for the continental Africa will be available for public use and can potentially enhance the ability of monitoring and studying the state of the Earth's surface.

Strong Effects of a Shelfbreak Jet on Microbial Enzyme Activities

NASA Astrophysics Data System (ADS)

Hoarfrost, A.; Balmonte, J. P.; Ziervogel, K.; Ghobrial, S.; Gawarkiewicz, G.; Arnosti, C.

2016-02-01

The activities of extracellular enzymes are critical in initiating microbial cycling of organic carbon, yet the dynamics of heterotrophic enzyme activities in marine environments are still poorly understood. Variations at a given site in rates of activity and the spectrum of organic substrates hydrolyzed may depend upon environmental context. We measured the extracellular enzymatic hydrolysis of 13 high- and low-molecular-weight organic substrates in surface and bottom waters along a closely spaced 4-station transect at 71 W on the North Atlantic continental shelf, in the vicinity of the shelfbreak front. This transect intersects a robust upwelling cell that typically shows high biologic productivity, and is locatable by changes in T/S profiles and chl a concentrations along sharp spatial gradients. At the time of sampling, cold pool waters over the continental shelf were relatively cold, 3.5 Deg. C, compared to 12 Deg. C over the upper continental slope. Satellite thermal imagery indicated that shelf water extended offshore and interacted with a large crest of the Gulf Stream. The surface and bottom waters associated with the upwelling jet were characterized by enzyme activities a factor of 20 more rapid than closer inshore waters, and surface water chl a concentrations that were two to three times higher than the inshore waters. The spectrum of enzyme activities also differed markedly between surface and bottom waters both within the jet and at near-shore stations. Microbial extracellular enzymatic activities were strongly influenced by differences in their environmental context along the continental slope and shelfbreak front. Constraining the factors controlling heterotrophic activity across the diverse marine environment is an important step in understanding microbial controls on carbon cycling.

Initiation and long-term instability of the East Antarctic Ice Sheet.

PubMed

Gulick, Sean P S; Shevenell, Amelia E; Montelli, Aleksandr; Fernandez, Rodrigo; Smith, Catherine; Warny, Sophie; Bohaty, Steven M; Sjunneskog, Charlotte; Leventer, Amy; Frederick, Bruce; Blankenship, Donald D

2017-12-13

Antarctica's continental-scale ice sheets have evolved over the past 50 million years. However, the dearth of ice-proximal geological records limits our understanding of past East Antarctic Ice Sheet (EAIS) behaviour and thus our ability to evaluate its response to ongoing environmental change. The EAIS is marine-terminating and grounded below sea level within the Aurora subglacial basin, indicating that this catchment, which drains ice to the Sabrina Coast, may be sensitive to climate perturbations. Here we show, using marine geological and geophysical data from the continental shelf seaward of the Aurora subglacial basin, that marine-terminating glaciers existed at the Sabrina Coast by the early to middle Eocene epoch. This finding implies the existence of substantial ice volume in the Aurora subglacial basin before continental-scale ice sheets were established about 34 million years ago. Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs. Tunnel valleys associated with half of these glaciations indicate that a surface-meltwater-rich sub-polar glacial system existed under climate conditions similar to those anticipated with continued anthropogenic warming. Cooling since the late Miocene resulted in an expanded polar EAIS and a limited glacial response to Pliocene warmth in the Aurora subglacial basin catchment. Geological records from the Sabrina Coast shelf indicate that, in addition to ocean temperature, atmospheric temperature and surface-derived meltwater influenced East Antarctic ice mass balance under warmer-than-present climate conditions. Our results imply a dynamic EAIS response with continued anthropogenic warming and suggest that the EAIS contribution to future global sea-level projections may be under-estimated.

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.

Initiation and long-term instability of the East Antarctic Ice Sheet

NASA Astrophysics Data System (ADS)

Gulick, Sean P. S.; Shevenell, Amelia E.; Montelli, Aleksandr; Fernandez, Rodrigo; Smith, Catherine; Warny, Sophie; Bohaty, Steven M.; Sjunneskog, Charlotte; Leventer, Amy; Frederick, Bruce; Blankenship, Donald D.

2017-12-01

Antarctica’s continental-scale ice sheets have evolved over the past 50 million years. However, the dearth of ice-proximal geological records limits our understanding of past East Antarctic Ice Sheet (EAIS) behaviour and thus our ability to evaluate its response to ongoing environmental change. The EAIS is marine-terminating and grounded below sea level within the Aurora subglacial basin, indicating that this catchment, which drains ice to the Sabrina Coast, may be sensitive to climate perturbations. Here we show, using marine geological and geophysical data from the continental shelf seaward of the Aurora subglacial basin, that marine-terminating glaciers existed at the Sabrina Coast by the early to middle Eocene epoch. This finding implies the existence of substantial ice volume in the Aurora subglacial basin before continental-scale ice sheets were established about 34 million years ago. Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs. Tunnel valleys associated with half of these glaciations indicate that a surface-meltwater-rich sub-polar glacial system existed under climate conditions similar to those anticipated with continued anthropogenic warming. Cooling since the late Miocene resulted in an expanded polar EAIS and a limited glacial response to Pliocene warmth in the Aurora subglacial basin catchment. Geological records from the Sabrina Coast shelf indicate that, in addition to ocean temperature, atmospheric temperature and surface-derived meltwater influenced East Antarctic ice mass balance under warmer-than-present climate conditions. Our results imply a dynamic EAIS response with continued anthropogenic warming and suggest that the EAIS contribution to future global sea-level projections may be under-estimated.

Trichodesmium slicks associated with environmental conditions of continental shelf-break at the southwestern of the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Detoni, A. M. S.; Yunes, J. S., Sr.; Ciotti, Á. M.; Calil, P. H. R.; Tavano, V. M.

2016-02-01

Trichodesmium can accumulate high biomass, particularly in the oligotrophic regions of North and Tropical Atlantic, and North Pacific. Large Trichodesmium slicks have been reported in the South Atlantic as well, associated with the Brazil Currrent (BC) that flows southwards over the continental shelf-break. Regional variations of the width of the Brazilian continental shelf, as well as changes in the bottom topography, generate cyclonic and anti-cyclonic eddies as BC crosses the southeastern Brazil. Thus, the general conditions of the BC - characterized as a warm, saline and oligotrophic current - are expected to change not only with latitude but also by the influence of mesoscale instabilities. In this study, three oceanographic cruises were carried out to characterize the distribution of Trichodesmium along the southeastern Brazilian continental shelf-break and their relationship with temperature and upper layer nutrients concentrations. As in other oceanic regions, high concentrations of Trichodesmium (maximum 212.6 × 105 trichomes L-1) were observed in waters with temperatures between 22° C to 25° C, low nitrogen (< 2.4 μM), and moderate phosphate concentrations (> 0.08 μM), where wind speeds were low (< 11 m s-1). Generally, slicks were present where phosphate concentration in the upper 25 m was slightly higher than that of adjacent waters. Wind and hydrographic observations suggested that wind divergence at micro-regions (approximately 625 km2), as well as shelf-break dynamics can drive sporadic shelf-break upwelling, favouring Trichodesmium growth between 23° S to 28° S. Although shelf-break upwelling may occur along the entire domain of the BC flow, Trichodesmium densities were low at latitudes between 28° S to 33° S likely a result of the lower sea surface temperature.

Research and development program, fiscal year 1966

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1964-04-01

The biomedical program of the Laboratory of Nuclear Medicine and Radiation Biology for FY 1966 is conducted within the scope of the following categories: Somatic Effects of Radiation; Combating Detrimental Effects of Radiation; Molecular and Cellular Level Studies; Environmental Radiation Studies; Radiological and Health Physics and Instrumentation; Chemical Toxicity; Cancer Research; and Selected Beneficial Applications. The overall objectives of the Laboratory within these areas of the Biology and Medicine program may be summarized as follows: (1) investigation of the effects of ionizing radiation on living organisms and systems of biological significance; (2) investigation of the dynamic aspects of physiological andmore » biochemical processes in man, animals and plants and how these processes are modified by radiation and related pathological states; (3) the assessment and study of the immediate and long term consequences of the operation or detonation of nuclear devices on the fauna, and flora in man's environment and on man; (4) the development of methods of minimizing or preventing the detrimental effects of ionizing radiation; (5) research in, and development of, beneficial uses of ionizing radiation and radioactive substances in medicine and biology; (6) research in the development of new and more efficient radiation detection devices; (7) research, including field studies, as mutually agreed upon by the Commission and the University, in connection with the conduct of weapon tests and biomedical and civil effects experiments at such tests conducted at continental and overseas test sites; and (8) the conduct of training and educational activities in the biological and medical aspects of radiation and related fields.« less

Statistics of Stacked Strata on Experimental Shelf Margins

NASA Astrophysics Data System (ADS)

Fernandes, A. M.; Straub, K. M.

2015-12-01

Continental margin deposits provide the most complete record on Earth of paleo-landscapes, but these records are complex and difficult to interpret. To a seismic geomorphologist or stratigrapher, mapped surfaces often present a static diachronous record of these landscapes through time. We present data that capture the dynamics of experimental shelf-margin landscapes at high-temporal resolution and define internal hierarchies within stacked channelized and weakly channelized deposits from the shelf to the slope. Motivated by observations from acoustically-imaged continental margins offshore Brunei and in the Gulf of Mexico, we use physical experiments to quantify stratal patterns of sub-aqueous slope channels and lobes that are linked to delta-top channels. The data presented here are from an experiment that was run for 26 hours of experimental run time. Overhead photographs and topographic scans captured flow dynamics and surface aggradation/degradation every ten minutes. Currents rich in sediment built a delta that prograded to the shelf-edge. These currents were designed to plunge at the shoreline and travel as turbidity currents beyond the delta and onto the continental slope. Pseudo-subsidence was imposed by a slight base-level rise that generated accommodation space and promoted the construction of stratigraphy on the delta-top. Compensational stacking is a term that is frequently applied to deposits that tend to fill in topographic lows in channelized and weakly channelized systems. The compensation index, a metric used to quantify the strength of compensation, is used here to characterize deposits at different temporal scales on the experimental landscape. The compensation timescale is the characteristic time at which the accumulated deposits begins to match the shape of basin-wide subsidence rates (uniform for these experiments). We will use the compensation indices along strike transects across the delta, proximal slope and distal slope to evaluate the degree of compensation and the trends in the compensation time-scale, tied to a reduced degree of channelization in the down-slope direction.

Comparison of Antarctic Crustal Thickness from Gravity Inversion and Seismology: Evidence for Mantle Dynamic Uplift under Marie Byrd Land

NASA Astrophysics Data System (ADS)

Ferraccioli, F.; Kusznir, N. J.; Jordan, T. A.

2017-12-01

Using gravity anomaly inversion, we produce comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. Antarctic crustal thicknesses derived from gravity inversion are compared with seismic estimates from Baranov (2011) and An et al. (2015). We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the Bedmap 2 ice thickness and bedrock topography compilation south of 60 degrees south and relatively sparse constraints on sediment thickness. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica, which is penetrated by narrow continental rifts featuring relatively thinner crust. The largest crustal thicknesses predicted from gravity inversion lie in the region of the Gamburtsev Subglacial Mountains, and are consistent with seismic estimates. The East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system, is imaged by our inversion and appears to extend from the continental margin at the Lambert Rift (LR) to the South Pole region, a distance of 2500 km. Thin crust is predicted under the Ross Sea and beneath the West Antarctic Ice Sheet and delineates the regional extent of the broad West Antarctic Rift System (WARS). Substantial regional uplift is required under Marie Byrd Land to reconcile gravity and seismic estimates. A mantle dynamic uplift origin of the uplift is preferred to a thermal anomaly from a very young rift. The new crustal thickness map produced by this gravity inversion study support the hypothesis that one branch of the WARS links through to the De Gerlache sea-mounts (DG) and Peter I Island (PI) in the Bellingshausen Sea region, while another branch may link to the George V Sound Rift in the Antarctic Peninsula region.

New Insights into Passive Margin Development from a Global Deep Seismic Reflection Dataset

NASA Astrophysics Data System (ADS)

Bellingham, Paul; Pindell, James; Graham, Rod; Horn, Brian

2014-05-01

The kinematic and dynamic evolution of the world's passive margins is still poorly understood. Yet the need to replace reserves, a high oil price and advances in drilling technology have pushed the international oil and gas industry to explore in the deep and ultra-deep waters of the continental margins. To support this exploration and help understand these margins, ION-GXT has acquired, processed and interpreted BasinSPAN surveys across many of the world's passive margins. Observations from these data lead us to consider the modes of subsidence and uplift at both volcanic and non-volcanic margins. At non-volcanic margins, it appears that frequently much of the subsidence post-dates major rifting and is not thermal in origin. Rather the subsidence is associated with extensional displacement on a major fault or shear zone running at least as deep as the continental Moho. We believe that the subsidence is structural and is probably associated with the pinching out (boudinage) of the Lower Crust so that the Upper crust effectively collapses onto the mantle. Eventually this will lead to the exhumation of the sub-continental mantle at the sea bed. Volcanic margins present more complex challenges both in terms of imaging and interpretation. The addition of volcanic and plutonic material into the system and dynamic effects all impact subsidence and uplift. However, we will show some fundamental observations regarding the kinematic development of volcanic margins and especially SDRs which demonstate that the process of collapse and the development of shear zones within and below the crust are also in existence at this type of margin. A model is presented of 'magma welds' whereby packages of SDRs collapse onto an emerging sub-crustal shear zone and it is this collapse which creates the commonly observed SDR geometry. Examples will be shown from East India, Newfoundland, Brazil, Argentina and the Gulf of Mexico.

Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago.

PubMed

Næraa, T; Scherstén, A; Rosing, M T; Kemp, A I S; Hoffmann, J E; Kokfelt, T F; Whitehouse, M J

2012-05-30

Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens. These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate tectonic processes.

Global Fiducials Program Imagery: New Opportunities for Geospatial Research, Outreach, and Education

NASA Astrophysics Data System (ADS)

Price, S. D.

2012-12-01

MOLNIA, Bruce F., PRICE, Susan D. and, KING, Stephen E., U.S. Geological Survey (USGS), 562 National Center, Reston, VA 20192, sprice@usgs.gov The Civil Applications Committee (CAC), operated by the U.S. Geological Survey (USGS), is the Federal interagency committee that facilitates Federal civil agency access to U.S. National Systems space-based electro-optical (EO) imagery for natural disaster response; global change investigations; ecosystem monitoring; mapping, charting, and geodesy; and related topics. The CAC's Global Fiducials Program (GFP) has overseen the systematic collection of high-resolution imagery to provide geospatial data time series spanning a decade or more at carefully selected sites to study and monitor changes, and to facilitate a comprehensive understanding of dynamic and sensitive areas of our planet. Since 2008, more than 4,500 one-meter resolution EO images which comprise time series from 85 GFP sites have been released for unrestricted public use. Initial site selections were made by Federal and academic scientists based on each site's unique history, susceptibility, or environmental value. For each site, collection strategies were carefully defined to maximize information extraction capabilities. This consistency enhances our ability to understand Earth's dynamic processes and long-term trends. Individual time series focus on Arctic sea ice change; temperate glacier behavior; mid-continent wetland dynamics; barrier island response to hurricanes; coastline evolution; wildland fire recovery; Long-Term Ecological Resource (LTER) site processes; and many other topics. The images are available from a USGS website at no cost, in an orthorectified GeoTIFF format with supporting metadata, making them ideal for use in Earth science education and GIS projects. New on-line tools provide enhanced analysis of these time-series imagery. For additional information go to http://gfp.usgs.gov or http://gfl.usgs.gov.Bering Glacier is the largest and longest glacier in continental North America, with a length of 190 km, a width of 40 km, and an area of about 5,000 km2. In the nine years between the 1996 image and the 2005 image, parts of the terminus retreated by more than 5 km and thinned by as much as 100 m. Long-term monitoring of Bering Glacier will enable scientists to better understand the dynamics of surging glaciers as well as how changing Alaska climate is affecting temperate glacier environments.

Emergence of canine parvovirus subtype 2b (CPV-2b) infections in Australian dogs.

PubMed

Clark, Nicholas J; Seddon, Jennifer M; Kyaw-Tanner, Myat; Al-Alawneh, John; Harper, Gavin; McDonagh, Phillip; Meers, Joanne

2018-03-01

Tracing the temporal dynamics of pathogens is crucial for developing strategies to detect and limit disease emergence. Canine parvovirus (CPV-2) is an enteric virus causing morbidity and mortality in dogs around the globe. Previous work in Australia reported that the majority of cases were associated with the CPV-2a subtype, an unexpected finding since CPV-2a was rapidly replaced by another subtype (CPV-2b) in many countries. Using a nine-year dataset of CPV-2 infections from 396 dogs sampled across Australia, we assessed the population dynamics and molecular epidemiology of circulating CPV-2 subtypes. Bayesian phylogenetic Skygrid models and logistic regressions were used to trace the temporal dynamics of CPV-2 infections in dogs sampled from 2007 to 2016. Phylogenetic models indicated that CPV-2a likely emerged in Australia between 1973 and 1988, while CPV-2b likely emerged between 1985 and 1998. Sequences from both subtypes were found in dogs across continental Australia and Tasmania, with no apparent effect of climate variability on subtype occurrence. Both variant subtypes exhibited a classical disease emergence pattern of relatively high rates of evolution during early emergence followed by subsequent decreases in evolutionary rates over time. However, the CPV-2b subtype maintained higher mutation rates than CPV-2a and continued to expand, resulting in an increase in the probability that dogs will carry this subtype over time. Ongoing monitoring programs that provide molecular epidemiology surveillance will be necessary to detect emergence of new variants and make informed recommendations to develop reliable detection and vaccine methods. Copyright © 2017 Elsevier B.V. All rights reserved.

High Resolution Quaternary Seismic Stratigraphy of the New York Bight Continental Shelf

USGS Publications Warehouse

Schwab, William C.; Denny, J.F.; Foster, D.S.; Lotto, L.L.; Allison, M.A.; Uchupi, E.; Swift, B.A.; Danforth, W.W.; Thieler, E.R.; Butman, Bradford

2003-01-01

A principal focus for the U.S. Geological Survey (USGS) Coastal and Marine Geology Program (marine.usgs.gov) is regional reconnaissance mapping of inner-continental shelf areas, with initial emphasis on heavily used areas of the sea floor near major population centers. The objectives are to develop a detailed regional synthesis of the sea-floor geology in order to provide information for a wide range of management decisions and to form a basis for further investigations of marine geological processes. In 1995, the USGS, in cooperation with the U.S. Army Corps of Engineers (USACOE), New York District, began to generate reconnaissance maps of the continental shelf seaward of the New York - New Jersey metropolitan area. This mapping encompassed the New York Bight inner-continental shelf, one of the most heavily trafficked and exploited coastal regions in the United States. Contiguous areas of the Hudson Shelf Valley, the largest physiographic feature on this segment of the continental shelf, also were mapped as part of a USGS study of contaminated sediments (Buchholtz ten Brink and others, 1994; 1996). The goal of the reconnaissance mapping was to provide a regional synthesis of the sea-floor geology in the New York Bight area, including: (a) a description of sea-floor morphology; (b) a map of sea-floor sedimentary lithotypes; (c) the geometry and structure of the Cretaceous strata and Quaternary deposits; and (d) the geologic history of the region. Pursuing the course of this mapping effort, we obtained sidescan-sonar images of 100 % of the sea floor in the study area. Initial interpretations of these sidescan data were presented by Schwab and others, (1997a, 1997b, 2000a). High-resolution seismic-reflection profiles collected along each sidescan-sonar line used multiple acoustic sources (e.g., watergun, CHIRP, Geopulse). Multibeam swath-bathymetry data also were obtained for a portion of the study area (Butman and others, 1998;). In this report, we present a series of structural and sediment isopach maps and interpretations of the Quaternary evolution of the inner-continental shelf off the New York - New Jersey metropolitan area based on subbottom, sidescan-sonar, and multibeam-bathymetric data.

Origin and evolution of a submarine large igneous province: the Kerguelen Plateau and Broken Ridge, southern Indian Ocean

NASA Astrophysics Data System (ADS)

Frey, F. A.; Coffin, M. F.; Wallace, P. J.; Weis, D.; Zhao, X.; Wise, S. W.; Wähnert, V.; Teagle, D. A. H.; Saccocia, P. J.; Reusch, D. N.; Pringle, M. S.; Nicolaysen, K. E.; Neal, C. R.; Müller, R. D.; Moore, C. L.; Mahoney, J. J.; Keszthelyi, L.; Inokuchi, H.; Duncan, R. A.; Delius, H.; Damuth, J. E.; Damasceno, D.; Coxall, H. K.; Borre, M. K.; Boehm, F.; Barling, J.; Arndt, N. T.; Antretter, M.

2000-02-01

Oceanic plateaus form by mantle processes distinct from those forming oceanic crust at divergent plate boundaries. Eleven drillsites into igneous basement of Kerguelen Plateau and Broken Ridge, including seven from the recent Ocean Drilling Program Leg 183 (1998-99) and four from Legs 119 and 120 (1987-88), show that the dominant rocks are basalts with geochemical characteristics distinct from those of mid-ocean ridge basalts. Moreover, the physical characteristics of the lava flows and the presence of wood fragments, charcoal, pollen, spores and seeds in the shallow water sediments overlying the igneous basement show that the growth rate of the plateau was sufficient to form subaerial landmasses. Most of the southern Kerguelen Plateau formed at ˜110 Ma, but the uppermost submarine lavas in the northern Kerguelen Plateau erupted during Cenozoic time. These results are consistent with derivation of the plateau by partial melting of the Kerguelen plume. Leg 183 provided two new major observations about the final growth stages of the Kerguelen Plateau. 1: At several locations, volcanism ended with explosive eruptions of volatile-rich, felsic magmas; although the total volume of felsic volcanic rocks is poorly constrained, the explosive nature of the eruptions may have resulted in globally significant effects on climate and atmospheric chemistry during the late-stage, subaerial growth of the Kerguelen Plateau. 2: At one drillsite, clasts of garnet-biotite gneiss, a continental rock, occur in a fluvial conglomerate intercalated within basaltic flows. Previously, geochemical and geophysical evidence has been used to infer continental lithospheric components within this large igneous province. A continental geochemical signature in an oceanic setting may represent deeply recycled crust incorporated into the Kerguelen plume or continental fragments dispersed during initial formation of the Indian Ocean during breakup of Gondwana. The clasts of garnet-biotite gneiss are the first unequivocal evidence of continental crust in this oceanic plateau. We propose that during initial breakup between India and Antarctica, the spreading center jumped northwards transferring slivers of the continental Indian plate to oceanic portions of the Antarctic plate.

Assessing homeland chemical hazards outside the military gates: industrial hazard threat assessments for department of defense installations.

PubMed

Kirkpatrick, Jeffrey S; Howard, Jacqueline M; Reed, David A

2002-04-08

As part of comprehensive joint medical surveillance measures outlined by the Department of Defense, the US Army Center for Health Promotion and Preventive Medicine (USACHPPM) is beginning to assess environmental health threats to continental US military installations. A common theme in comprehensive joint medical surveillance, in support of Force Health Protection, is the identification and assessment of potential environmental health hazards, and the evaluation and documentation of actual exposures in both a continental US and outside a continental US setting. For the continental US assessments, the USACHPPM has utilized the US Environmental Protection Agency (EPA) database for risk management plans in accordance with Public Law 106-40, and the toxic release inventory database, in a state-of the art geographic information systems based program, termed the Consequence Assessment and Management Tool Set, or CATS, for assessing homeland industrial chemical hazards outside the military gates. As an example, the US EPA toxic release inventory and risk management plans databases are queried to determine the types and locations of industries surrounding a continental US military installation. Contaminants of concern are then ranked with respect to known toxicological and physical hazards, where they are then subject to applicable downwind hazard simulations using applicable meteorological and climatological data sets. The composite downwind hazard areas are mapped in relation to emergency response planning guidelines (ERPG), which were developed by the American Industrial Hygiene Association to assist emergency response personnel planning for catastrophic chemical releases. In addition, other geographic referenced data such as transportation routes, satellite imagery and population data are included in the operational, equipment, and morale risk assessment and management process. These techniques have been developed to assist military medical planners and operations personnel in determining the industrial hazards, vulnerability assessments and health risk assessments to continental United States military installations. These techniques and procedures support the Department of Defense Force Protection measures, which provides awareness of a terrorism threat, appropriate measures to prevent terrorist attacks and mitigate terrorism's effects in the event that preventive measures are ineffective.

77 FR 40376 - Outer Continental Shelf, Oil and Gas Lease Sales in the Central Gulf of Mexico Planning Area (CPA...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-09

..., archaeological and socioeconomic conditions or conflicts, or other information that might bear upon the potential leasing and development of this area. BOEM also seeks comments on possible conflicts between future OCS... Programs (CMPs). If possible, these comments should identify specific CMP policies of concern, the nature...

NOAA Office of Exploration and Research > About OER > Organization

Science.gov Websites

the break of the continental shelf between Virginia and New England. May 2011: OER EX Program hosts an Atlantic Basin Workshop to identify exploration targets for the 2012 EX field season. May 2011: OER -U.S. exploration and NOAA Ship Okeanos Explorer's (EX) maiden voyage. Jul 2009: Renewed Joint Project

30 CFR 250.1510 - What will MMS do if my training program does not comply with this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

... not comply with this subpart? 250.1510 Section 250.1510 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Well... one or more of the following enforcement actions: (a) Issue an Incident of Noncompliance (INC); (b...

Environmental Statement for Proposed Continental Operations Range.

DTIC Science & Technology

1974-12-17

out territories, recognize young, detect and locate prey , and evade predators . These functions could be critically affected, even if the animals appear... Sparrow 254. CaZamoapiza meZanocorye Lark Bunting 266. Spizella atrogularis evura 255. Paaaerculue 8andwichensia nevadensis* Black-chinned Sparrow ...and Evaluation Systems Program Office By ............. .....------------- Kirtland Air Force Base, New Mexico Distribution I Availability Codes I

Mexican forest inventory expands continental carbon monitoring

Treesearch

Alberto Sandoval Uribe; Sean. P. Healey; Gretchen G. Moisen; Rigoberto Palafox Rivas; Enrique Gonzalez Aguilar; Carmen Lourdes Meneses Tovar; Ernesto S. Diaz Ponce Davalos; Vanessa Silva Mascorro

2008-01-01

The terrestrial ecosystems of the North American continent represent a large reservoir of carbon and a potential sink within the global carbon cycle. The recent State of the Carbon Cycle Report [U.S. Climate Change Science Program (CCSP), 2007] identified the critical role these systems may play in mitigating effects of greenhouse gases emitted from fossil fuel...

30 CFR 250.282 - Do I have to conduct post-approval monitoring?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false Do I have to conduct post-approval monitoring... OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Plans and... monitoring? The Regional Supervisor may direct you to conduct monitoring programs. You must retain copies of...

30 CFR 250.282 - Do I have to conduct post-approval monitoring?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false Do I have to conduct post-approval monitoring... OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Plans and... monitoring? The Regional Supervisor may direct you to conduct monitoring programs. You must retain copies of...

30 CFR 250.282 - Do I have to conduct post-approval monitoring?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false Do I have to conduct post-approval monitoring... OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Plans and... monitoring? The Regional Supervisor may direct you to conduct monitoring programs. You must retain copies of...

Live via Satellite: Interactive Distant Learning in America's Rural Schools.

ERIC Educational Resources Information Center

Barker, Bruce O.

Advances in satellite technology hold great promise for offering a broad and varied curriculum in small rural schools. In 1985 and 1986 three vendors in the continental United States pioneered the offering of interactive satellite instruction for high school credit courses. The programs were: (1) German by Satellite offered by the College of Arts…

30 CFR 250.415 - What must my casing and cementing programs include?

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Applying for A Permit to Drill § 250.415 What must my casing and... in Deep Water Wells (incorporated by reference as specified in § 250.198), if you drill a well in...

30 CFR 250.411 - What information must I submit with my application?

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL AND GAS AND SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF Oil and Gas Drilling Operations Applying for A Permit to Drill § 250.411 What information must I... proposed well § 250.413 (c) Drilling prognosis § 250.414 (d) Casing and cementing programs § 250.415 (e...

Improved Aviation Readiness and Inventory Reductions Through Repair Cycle Time Reductions Using Modeling and Simulation.

DTIC Science & Technology

1997-12-01

three NADEP’s within the continental United States and fleet repair sites in Italy and Japan. These facilities are located to support specific...number order. This same morning, P&E’s have a last opportunity to edit the induction file through the Planner and Estimator Cancellation Program ( PECAN

Monitoring Ecosystems and Biodiversity at a Continental Scale--A Proposal for South America

Treesearch

Xavier Silva

2006-01-01

A monitoring system plan is being developed in South America to assess critically endangered ecoregions. The system will be based on a previous ecosystem and biodiversity inventory developed through a large gap analysis program in five South American ecoregions. The monitoring system will include three main elements: (1) Landscape Ecology: vegetation cover,...

30 CFR 250.905 - How do I get approval for the installation, modification, or repair of my platform?

Code of Federal Regulations, 2012 CFR

2012-07-01

... CONTINENTAL SHELF Platforms and Structures Platform Approval Program § 250.905 How do I get approval for the...) Application cover letter Proposed structure designation, lease number, area, name, and block number, and the type of facility your facility (e.g., drilling, production, quarters). The structure designation must...

Dynamics of the transfer of terrestrial organic matter in the late Quaternary turbiditic system of the Ogooué River (Gabon)

NASA Astrophysics Data System (ADS)

Mignard, Salomé; Mulder, Thierry; Martinez, Philippe; Garlan, Thierry

2016-04-01

In many cases (Hedges et al., 1995, Xing et al., 2011) the supply of terrestrial organic matter (OM) in the oceanic environment is confined to the continental and upper slope of continental margins. However, some recent studies (Huc et al., 2001, Baudin et al., 2010, Biscara et al., 2011, Stetten et al., 2015) demonstrated that significant amounts of continental OM can be transported and deposited in deep sea sediments. This transfer is more efficient in turbiditic systems which are linked to important river deltas. In such systems, the terrigenous influx are important and the downslope sediment-laden currents can indeed transport and rapidly bury important quantities of TOM transferred from the river mouth and the shelf to the abyssal plain. The turbiditic system associated with the Ogooué River offshore Gabon has been selected to study more precisely the modalities of transfer of continental OM from the shelf to the deep offshore. The works focuses on the concentration of OM in both hemipelagites and turbidites as well as the different parameters influencing the spatial distribution and concentration. For this study 10 cores located along the system from the continental shelf to the distal lobes have been selected. The quantity of OM in the sediments as well as its origin (continental vs marine) have been measured using bulk geochemical analyses (% OC, δ13Corg). The stratigraphy of the cores was determined using a combination of planktonic foraminiferal assemblages, δ18O on benthic foraminifers and 14C dates on planktonic foraminifers, and calcium carbonate content calibrated with XRF measurements. The studied cores contain various amounts of organic carbon ranging from 0.7wt% to more than 9wt%. The highest contents are found in turbidite beds where woody detritus and well preserved fragmentary leaf debris are concentrated. In the hemipelagic facies, organic matter is composed of a mixture of marine and land derived organic matter associated with clay-size sediments. This organic sedimentation is highly sensitive to the variations of the sea level due to the alternation between glacial and interglacial times. Glacial periods are characterized by higher amounts of organic matter in hemipelagic deposits, with a higher contribution of continental material, and by the presence of frequent organic rich turbiditic beds. On the contrary, during interglacial periods very few turbiditic events are recorded and the OM in hemipelagic sediments is mainly of marine origin and in lesser quantity. When the sea-level is high, the Ogooué delta is disconnected from the canyon heads and the sediments delivered by the river are deposited on the shelf and mobilized by the strong South-North coastal drift currents. During low sea-level periods, the river discharges its sediments rich in terrestrial OM directly in the canyons heads bypassing the shelf. The low sea level also generates increased erosion of the shelf sediments containing globally high rate of reworked continental OM.

Maintenance of Summer Monsoon Circulations: A Planetary-Scale Perspective.

NASA Astrophysics Data System (ADS)

Chen, Tsing-Chang

2003-06-01

The monsoon circulation, which is generally considered to be driven by the landmass-ocean thermal contrast, like a gigantic land-sea breeze circulation, exhibits a phase reversal in its vertical structure; a monsoon high aloft over a continental thermal low is juxtaposed with a midoceanic trough underlaid by an oceanic anticyclone. This classic monsoon circulation model is well matched by the monsoon circulation depicted with the observational data prior to the First Global Atmospheric Research Program (GARP) Global Experiment (FGGE). However, synthesizing findings of the global circulation portrayed with the post-FGGE data, it was found that some basic features of major monsoon circulations in Asia, North America, South America, and Australia differ from those of the classic monsoon circulation model. Therefore, a revision of the classic monsoon theory is suggested. With four different wave regimes selected to fit the horizontal dimensions of these monsoon circulations, basic features common to all four major monsoons are illustrated in terms of diagnostic analyses of the velocity potential maintenance equation (which relates diabatic heating and velocity potential) and the streamfunction budget (which links velocity potential and streamfunction) in these wave regimes. It is shown that a monsoon circulation is actually driven by the east-west differential heating and maintained dynamically by a balance between a vorticity source and advection. This dynamic balance is reflected by a spatial quadrature relationship between the monsoon divergent circulation and the monsoon high (low) at upper (lower) levels.

Application of WRF/Chem over the Continental U.S. under the AQMEII Phase II: Part 2. Evaluation of 2010 Application and Responses of Air Quality and Meteorology-Chemistry Interactions to Changes in Emissions and Meteorology from 2006 to 2010

EPA Science Inventory

The Weather Research and Forecasting model with Chemistry (WRF/Chem) simulation with the 2005 Carbon Bond (CB05) gas-phase mechanism coupled to the Modal for Aerosol Dynamics for Europe (MADE) and the Volatility Basis Set (VBS) approach for secondary organic aerosol (SOA) (MADE/V...

North American water availability under stress and duress: building understanding from simulations, observations and data products

NASA Astrophysics Data System (ADS)

Maxwell, R. M.; Condon, L. E.; Atchley, A. L.; Hector, B.

2017-12-01

Quantifying the available freshwater for human use and ecological function depends on fluxes and stores that are hard to observe. Evapotranspiration (ET) is the largest terrestrial flux of water behind precipitation but is observed with low spatial density. Likewise, groundwater is the largest freshwater store, yet is equally uncertain. The ability to upscale observations of these variables is an additional complication; point measurements are made at scales orders of magnitude smaller than remote sensing data products. Integrated hydrologic models that simulate continental extents at fine spatial resolution are now becoming an additional tool to constrain fluxes and address interconnections. For example, recent work has shown connections between water table depth and transpiration partitioning, and demonstrated the ability to reconcile point observations and large-scale inferences. Here we explore the dynamics of large hydrologic systems experiencing change and stress across continental North America using integrated model simulations, observations and data products. Simulations of aquifer depletion due to pervasive groundwater pumping diagnose both stream depletion and changes in ET. Simulations of systematic increases in temperature are used to understand the relationship between snowpack dynamics, surface and groundwater flow, ET and a changing climate. Remotely sensed products including the GRACE estimates of total storage change are downscaled using model simulations to better understand human impacts to the hydrologic cycle. These example applications motivate a path forward to better use simulations to understand water availability.

Paleogeographic constraints on continental-scale source-to-sink systems: Northern South America and its Atlantic margins

NASA Astrophysics Data System (ADS)

Bajolet, Flora; Chardon, Dominique; Rouby, Delphine; Dall'Asta, Massimo; Roig, Jean-Yves; Loparev, Artiom; Coueffe, Renaud

2017-04-01

Our work aims at setting the evolving boundary conditions of erosion and sediments transfer, transit, and onshore-offshore accumulations on northern South America and along its Atlantic margins. Since the Early Mesozoic, the source-to-sink system evolved under the interplay of four main processes, which are (i) volcanism and arc building along the proto-Andes, (ii) long-term dynamics of the Amazon incratonic basin, (iii) rifting, relaxation and rejuvenation of the Atlantic margins and (iv) building of the Andes. We compiled information available from geological maps and the literature regarding tectonics, plate kinematics, magmatism, stratigraphy, sedimentology (including paleoenvironments and currents) and thermochronology to produce a series of paleogeographic maps showing the tectonic and kinematic framework of continental areas under erosion (sources), by-pass and accumulation (sinks) over the Amazonian craton, its adjacent regions and along its Atlantic margins. The maps also allow assessing the relative impact of (i) ongoing Pacific subduction, (ii) Atlantic rifting and its aftermath, and (iii) Atlantic slab retreat from under the Caribbean domain on the distribution and activity of onshore/offshore sedimentary basins. Stratigraphic and thermochronology data are also used to assess denudation / vertical motions due to sediment transfers and lithosphere-asthenosphere interactions. This study ultimately aims at linking the sediment routing system to long-wavelength deformation of northern South America under the influence of mountain building, intracratonic geodynamics, divergent margin systems and mantle dynamics.

Shelf-Basin Exchange over the Continental Slope of the Chukchi Sea 2003/04 vs. 2016/17

NASA Astrophysics Data System (ADS)

Muenchow, A.; Elmer, C.; Badiey, M.; Eickmeier, J.; Ryan, P.

2017-12-01

The US Navy faces the "New Arctic" as a challenge to predict acoustic propagation from deep to shallow waters, because a less ice-covered Arctic Ocean is more dynamic and creates new and more complex sound channels. We here present context and preliminary results from the Canada Basin Acoustic Propagation Experiment (CANAPE) and focus on the Chukchi Sea between 100-m and 800-m isobaths. We explore temperature and density fields using ocean survey and mooring data that we collected in 2016 and 2017. We compare these "new" data to observations from prior decades.Remote sensing (SSMI and Sentinel-1) of sea ice, winds, and ocean hydrography all document change in large scale ocean forcing in our study area about 150 km west of Barrow, Alaska. The "new" surface forcing impacts both ocean dynamics and sound propagation over the Chukchi Slope. More specifically, we find warm water intrusions at 80-m depth near the 1026 kg/m3 density surface at 160 W longitude. Spatial extend and structure of this water varies both along and across the continental with eddy trains dispersing offshore. Temperature and sound speed signals exceed 1 C and 5 m/s, respectively, and have not been observed before. We note, that our study area is generally ice-covered in November, but was free of ice in 2016.

Offshore oil and gas activity impact. Hearings before the Committee on Energy and Natural Resources, US Senate, One Hundred Sixth Congress, First Session, January 27, 1999

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1999-07-01

The purpose of this hearing is hear of the impacts of offshore exploration and production activities on coastal states and communities as it relates to Senate Bill 25. This bill would remedy current inequities by redistributing 50 percent of the Outer Continental Shelf (OCS) revenues to three programs: coastal impact assistance, local park and recreation, and wildlife programs. Statements were heard from representatives from three of the Gulf Coast States, as well as Alaska.

LANDSAT-4 TM image data quality analysis for energy-related applications

NASA Technical Reports Server (NTRS)

Wukelic, G. E.; Foote, H. P.

1983-01-01

LANDSAT-4 Thematic Mapper (TM) data performance and utility characteristics from an energy research and technology perspective is evaluated. The program focuses on evaluating applicational implications of using such data, in combination with other digital data, for current and future energy research and technology activities. Prime interest is in using TM data for siting, developing and operating federal energy facilities. Secondary interests involve the use of such data for resource exploration, environmental monitoring and basic scientific initiatives such as in support of the Continental Scientific Drilling Program.

CSDMS2.0: Computational Infrastructure for Community Surface Dynamics Modeling

NASA Astrophysics Data System (ADS)

Syvitski, J. P.; Hutton, E.; Peckham, S. D.; Overeem, I.; Kettner, A.

2012-12-01

The Community Surface Dynamic Modeling System (CSDMS) is an NSF-supported, international and community-driven program that seeks to transform the science and practice of earth-surface dynamics modeling. CSDMS integrates a diverse community of more than 850 geoscientists representing 360 international institutions (academic, government, industry) from 60 countries and is supported by a CSDMS Interagency Committee (22 Federal agencies), and a CSDMS Industrial Consortia (18 companies). CSDMS presently distributes more 200 Open Source models and modeling tools, access to high performance computing clusters in support of developing and running models, and a suite of products for education and knowledge transfer. CSDMS software architecture employs frameworks and services that convert stand-alone models into flexible "plug-and-play" components to be assembled into larger applications. CSDMS2.0 will support model applications within a web browser, on a wider variety of computational platforms, and on other high performance computing clusters to ensure robustness and sustainability of the framework. Conversion of stand-alone models into "plug-and-play" components will employ automated wrapping tools. Methods for quantifying model uncertainty are being adapted as part of the modeling framework. Benchmarking data is being incorporated into the CSDMS modeling framework to support model inter-comparison. Finally, a robust mechanism for ingesting and utilizing semantic mediation databases is being developed within the Modeling Framework. Six new community initiatives are being pursued: 1) an earth - ecosystem modeling initiative to capture ecosystem dynamics and ensuing interactions with landscapes, 2) a geodynamics initiative to investigate the interplay among climate, geomorphology, and tectonic processes, 3) an Anthropocene modeling initiative, to incorporate mechanistic models of human influences, 4) a coastal vulnerability modeling initiative, with emphasis on deltas and their multiple threats and stressors, 5) a continental margin modeling initiative, to capture extreme oceanic and atmospheric events generating turbidity currents in the Gulf of Mexico, and 6) a CZO Focus Research Group, to develop compatibility between CSDMS architecture and protocols and Critical Zone Observatory-developed models and data.

Temporal and spatial differences in microbial composition during the manufacture of a continental-type cheese.

PubMed

O'Sullivan, Daniel J; Cotter, Paul D; O'Sullivan, Orla; Giblin, Linda; McSweeney, Paul L H; Sheehan, Jeremiah J

2015-04-01

We sought to determine if the time, within a production day, that a cheese is manufactured has an influence on the microbial community present within that cheese. To facilitate this, 16S rRNA amplicon sequencing was used to elucidate the microbial community dynamics of brine-salted continental-type cheese in cheeses produced early and late in the production day. Differences in the microbial composition of the core and rind of the cheese were also investigated. Throughout ripening, it was apparent that cheeses produced late in the day had a more diverse microbial population than their early equivalents. Spatial variation between the cheese core and rind was also noted in that cheese rinds were initially found to have a more diverse microbial population but thereafter the opposite was the case. Interestingly, the genera Thermus, Pseudoalteromonas, and Bifidobacterium, not routinely associated with a continental-type cheese produced from pasteurized milk, were detected. The significance, if any, of the presence of these genera will require further attention. Ultimately, the use of high-throughput sequencing has facilitated a novel and detailed analysis of the temporal and spatial distribution of microbes in this complex cheese system and established that the period during a production cycle at which a cheese is manufactured can influence its microbial composition. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Archean komatiite volcanism controlled by the evolution of early continents.

PubMed

Mole, David R; Fiorentini, Marco L; Thebaud, Nicolas; Cassidy, Kevin F; McCuaig, T Campbell; Kirkland, Christopher L; Romano, Sandra S; Doublier, Michael P; Belousova, Elena A; Barnes, Stephen J; Miller, John

2014-07-15

The generation and evolution of Earth's continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50-30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean-Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits.

Archean komatiite volcanism controlled by the evolution of early continents

PubMed Central

Mole, David R.; Fiorentini, Marco L.; Thebaud, Nicolas; Cassidy, Kevin F.; McCuaig, T. Campbell; Kirkland, Christopher L.; Romano, Sandra S.; Doublier, Michael P.; Belousova, Elena A.; Barnes, Stephen J.; Miller, John

2014-01-01

The generation and evolution of Earth’s continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50–30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean–Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits. PMID:24958873

Space-for-time substitution and the evolution of submarine canyons in a passive, progradational margin.

NASA Astrophysics Data System (ADS)

Micallef, Aaron; Ribó, Marta; Canals, Miquel; Puig, Pere; Lastras, Galderic; Tubau, Xavier

2013-04-01

40% of submarine canyons worldwide are located in passive margins, where they constitute preferential conduits of sediment and biodiversity hotspots. Recent studies have presented evidence that submarine canyons incising passive, progradational margins can co-evolve with the adjacent continental slope during long-term margin construction. The stages of submarine canyon initiation and their development into a mature canyon-channel system are still poorly constrained, however, which is problematic when attempting to reconstruct the development of passive continental margins. In this study we analyse multibeam echosounder and seismic reflection data from the southern Ebro margin (western Mediterranean Sea) to document the stages through which a first-order gully develops into a mature, shelf-breaching canyon and, finally, into a canyon-channel system. This morphological evolution allows the application of a space-for-time substitution approach. Initial gully growth on the continental slope takes place via incision and downslope elongation, with limited upslope head retreat. Gravity flows are the main driver of canyon evolution, whereas slope failures are the main agent of erosion; they control the extent of valley widening, promote tributary development, and their influence becomes more significant with time. Breaching of the continental shelf by a canyon results in higher water/sediment loads that enhance canyon development, particularly in the upper reaches. Connection of the canyon head with a paleo-river changes evolution dynamics significantly, promoting development of a channel and formation of depositional landforms. Morphometric analyses demonstrate that canyons develop into geometrically self-similar systems that approach steady-state and higher drainage efficiency. Canyon activity in the southern Ebro margin is pulsating and enhanced during sea level lowstands. Rapid sedimentation by extension of the palaeo-Millars River into the outermost shelf and upper slope is inferred as the source of gravity flows driving canyon evolution. Canyon morphology is shown to be maintained over the course of more than one fall and rise in sea-level. Our model of canyon evolution is applicable to other passive margins (e.g. Argentine continental margin).

Time-Frequency Variability of Kuroshio Meanders in Tokara Strait

NASA Astrophysics Data System (ADS)

Nakamura, H.; Yamashiro, T.; Nishina, A.; Ichikawa, H.

2006-12-01

The Kuroshio path in the northern Okinawa Trough, Japan, located between the continental slope and Tokara Strait, exhibits meandering motions with largest displacements in the East China Sea; these motions have dominant periods in the broad range of 30-90 days. Understanding the dynamic nature of such meanders is crucial to predicting small and large meanders of the Kuroshio path off the south coast of Japan. Previous numerical simulations suggest that the Kuroshio path meanders in the northern Okinawa Trough become nonstationary in variance because of changes in background states of the Kuroshio in the northern Okinawa Trough, but a detailed analysis based on observed data has yet to be performed. The purpose of the present study is to provide a detailed description of the time-frequency variability of Kuroshio path meanders observed in Tokara Strait. Three Kuroshio indicators were subjected to wavelet analysis for the period 1984-2004: the Kuroshio Position Index (KPI) in Tokara Strait, Kuroshio Volume Transport (KVT) in Tokara Strait, and the basal current velocity of the Kuroshio on the continental slope in the northern Okinawa Trough. The 30-90 day variance of the KPI shows a season-fixed nature, with larger amplitudes in the period December-July. The amplitude of the variance in this phenomenon is also modulated by interannual variations, with small variance recorded during 1989-1992, large variance during 1993-1998, and a return to small variance from 1999-2003. This interannual variation is positively correlated with that of the KVT. The largest variance of the KPI during February-April precedes the largest volume transport in April-May by about 1 month, suggesting that eddy vorticity flux strengthens the mean current field. Previous numerical simulations reproduce the recirculation gyre as a cyclonic eddy in the area between the continental slope and Tokara Strait; this gyre is analogous to the northern recirculation gyre associated with the eastward jet. On the basis of data from a moored current-meter situated on the continental slope, the genesis of the 30-90 day meanders within Tokara Strait is ascribed to nonlinear energy transfer from 8-25 day meanders on the continental slope.

Denudation of the continental shelf between Britain and France at the glacial–interglacial timescale

PubMed Central

Mellett, Claire L.; Hodgson, David M.; Plater, Andrew J.; Mauz, Barbara; Selby, Ian; Lang, Andreas

2013-01-01

The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial–interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and 14C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form. Sediment reworking over multiple sea-level cycles (Saalian–Eemian–early Weichselian) by fluvial, coastal and marine processes created a multi-lateral, multi-storey succession of palaeovalley-fills that are preserved as a strath terrace. The data presented here reveal a composite erosional and depositional record that has undergone a high degree of reworking over multiple sea-level cycles leading to the preferential preservation of sediments associated with the most recent glacial–interglacial period. PMID:24748702

A model study of sediment transport across the shelf break

NASA Astrophysics Data System (ADS)

Marchal, Olivier

2017-04-01

A variety of dynamical processes can contribute to the transport of material (e.g., particulate matter) across the shelf break - the region separating the continental shelf from the continental slope. Among these processes are (i) the reflection of internal waves on the outer shelf and upper slope, and (ii) the instability of hydrographic fronts, roughly aligned with isobaths, that are often present at the shelf break. On the one hand, internal waves reflecting on a sloping boundary can produce bottom shear stresses that are large enough to resuspend non-cohesive sediments into the water column. On the other hand, eddies shed from unstable shelf break fronts can incorporate into their core particle-rich waters from the outer shelf and upper slope, and transport these waters offshore. Here we present numerical experiments with a three-dimensional numerical model of ocean circulation and sediment transport, which illustrate the joint effect of internal waves and eddies on sediment transport across the shelf break. The model is based on the primitive equations and terrain-following coordinates. The model domain is square and idealized, comprising a flat continental shelf, a constant continental slope, and a flat abyssal basin. The model grid has O(1 km) horizontal resolution, so that (sub)mesoscale eddies observed in the vicinity of shelf breaks, such as south of New England, can be represented in detail. Internal waves are excited through the specification of a periodic variation in the across-slope component of velocity at the offshore boundary of the domain, and eddies are generated from the baroclinic instability of a shelf break jet that is initially in strict thermal wind balance. Numerical experiments are conducted that are characterized by (i) different slopes of internal wave characteristics relative to the continental slope, representing sub-critical, critical, and super-critical regimes, and (ii) different values for the dimensionless ratios that emerge from the linear stability analysis of shelf break fronts. Emphasis is placed on the physical conditions that are conducive to the formation and maintenance of bottom and intermediate nepheloid layers - the particle-rich layers that are often observed near oceanic margins in the traces of optical instruments.

Relationship between Mean Winds and Large 10-day Precipitation Anomalies over the Continental U.S.

NASA Technical Reports Server (NTRS)

Helfand, H. Mark

2008-01-01

To better understand the role of surface boundary forcing upon interannual and decadal variability of droughts and precipitation excesses over the continental U. S., an observational study has been carried out to better investigate the dynamical linkages between surface boundary forcing and droughts/floods. This study examines the relationship during the warm season between observed mean wind patterns on the 10-15 day time scale and anomalies in precipitation on that same time scale over the U. S. Each of the 7 cases of significant 10-day, warm-season drought over the U, S. since 1948 that has been investigated was accompanied by significant continental-scale ridging of the mean 10-day 250 mb wind pattern over the continental U.S. and a mid-Pacific relative maximum of 250 mb wind speed of at least 30 m/sec within 20 degrees of the international Date Line. This perhaps suggests the presence of a wave-guide phenomenon over the Pacific. The drought signal for each of these cases was still quite evident when averaged over the monthly time scale. While peak magnitudes of the precipitation anomalies were much larger for the 7 chosen cases of significant of precipitation excess were than for the drought cases none of the patterns of precipitation excess were as unambiguous or wide-spread as the drought cases. In only 2 to 3 cases was there evidence of a continental trough in the 250 mb winds. In fact, one case showed slight ridging over Canada and the extreme northern U.S. Strong southerly low-level jets, however, were evident in the 925 mb winds over south-central Texas or the nearby Gulf of Mexico in virtually all of the excessive precipitation cases, while the Great Plains LLJ was weak or displaced to the north of Texas in most of the drought cases. We will further investigate the asymmetry between droughts and precipitation excesses in their horizontal homogeneity and extent, in their temporal evolution, and in how the are forced by the combined effects of the mean 250 mb westerlies and the mean 925 mb southerly winds.

Plate Speed-up and Deceleration during Continental Rifting: Insights from Global 2D Mantle Convection Models.

NASA Astrophysics Data System (ADS)

Brune, S.; Ulvrova, M.; Williams, S.

2017-12-01

The surface of the Earth is divided into a jigsaw of tectonic plates, some carrrying continents that disperse and aggregate through time, forming transient supercontinents like Pangea and Rodinia. Here, we study continental rifting using large-scale numerical simulations with self-consistent evolution of plate boundaries, where continental break-up emerges spontaneously due to slab pull, basal drag and trench suction forces.We use the StagYY convection code employing a visco-plastic rheology in a spherical annulus geometry. We consider an incompressible mantle under the Boussinesq approximation that is basally and internally heated.We show that continental separation follows a characteristic evolution with three distinctive phases: (1) A pre-rift phase that typically lasts for several hundreds of millions of years with tectonic quiescence in the suture and extensional stresses that are slowly building up. (2) A rift phase that further divides into a slow rift period of several tens of millions of years where stresses continuously increase followed by a rift acceleration period featuring an abrupt stress drop within several millions of years. The speed-up takes place before lithospheric break-up and therefore affects the structural architecture of the rifted margins. (3) The drifting phase with initially high divergence rates persists over tens of millions of years until the system adjust to new conditions and the spreading typically slows down.By illustrating the geodynamic connection between subduction dynamics and rift evolution, our results allow new interpretations of plate tectonic reconstructions. Rift acceleration within the second phase of rifting is compensated by enhanced convergence rates at subduction zones. This model outcome predicts enhanced subduction velocities, e.g. between North America and the Farallon plate during Central Atlantic rifting 200 My ago, or closure of potential back-arc basins such as in the proto-Andean ranges of South America during South Atlantic opening. Post-rift deceleration occurs when the global plate system re-equilibrates after continental rupture. This phenomenon of a plate slow-down after mechanical rupture is recorded by observations from rifted margins between Australia-Antarctica and Greenland-Eurasia.

Denudation of the continental shelf between Britain and France at the glacial-interglacial timescale.

PubMed

Mellett, Claire L; Hodgson, David M; Plater, Andrew J; Mauz, Barbara; Selby, Ian; Lang, Andreas

2013-12-01

The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial-interglacial sea-level cycles rather than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and 14 C ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have been identified. The continental shelf in the eastern English Channel preserves a record of processes operating from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form. Sediment reworking over multiple sea-level cycles (Saalian-Eemian-early Weichselian) by fluvial, coastal and marine processes created a multi-lateral, multi-storey succession of palaeovalley-fills that are preserved as a strath terrace. The data presented here reveal a composite erosional and depositional record that has undergone a high degree of reworking over multiple sea-level cycles leading to the preferential preservation of sediments associated with the most recent glacial-interglacial period.

Structure of the Lithosphere-Asthenosphere Boundary Onshore and Offshore the California Continental Margin from Three-Dimensional Seismic Anisotropy

NASA Astrophysics Data System (ADS)

Gomez, C. D.; Escobar, L., Sr.; Rathnayaka, S.; Weeraratne, D. S.; Kohler, M. D.

2016-12-01

The California continental margin, a major transform plate boundary in continental North America, is the locus of complex tectonic stress fields that are important in interpreting both remnant and ongoing deformational strain. Ancient subduction of the East Pacific Rise spreading center, the rotation and translation of tectonic blocks and inception of the San Andreas fault all contribute to the dynamic stress fields located both onshore and offshore southern California. Data obtained by the ALBACORE (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) and the CISN (California Integrated Seismic Network) seismic array are analyzed for azimuthal anisotropy of Rayleigh waves from 80 teleseismic events at periods 16 - 78 s. Here we invert Rayleigh wave data for shear wave velocity structure and three-dimensional seismic anisotropy in the thee regions designated within the continental margin including the continent, seafloor and California Borderlands. Preliminary results show that seismic anisotropy is resolved in multiple layers and can be used to determine the lithosphere-asthenosphere boundary (LAB) in offshore and continental regions. The oldest seafloor in our study at age 25-35 Ma indicates that the anisotropic transition across the LAB occurs at 73 km +/- 25 km with the lithospheric fast direction oriented WNW-ESE, consistent with current Pacific plate motion direction. The continent region west of the San Andreas indicates similar WNW-ESE anisotropy and LAB depth. Regions east of the San Andreas fault indicate NW-SE anisotropy transitioning to a N-S alignment at 80 km depth north of the Garlock fault. The youngest seafloor (15 - 25 Ma) and outer Borderlands indicate a more complex three layer fabric where shallow lithospheric NE-SW fast directions are perpendicular with ancient Farallon subduction arc, a mid-layer with E-W fast directions are perpendicular to remnant fossil fabric, and the deepest layer indicates NW-SE fast directions below the LAB likely controlled by current Pacific plate motion. The inner Borderland indicates two layer anisotropic structure with a shallow NW-SE lithospheric fast direction that changes to NE-SW fast directions below the LAB, possibly consistent with the ancient subduction direction.

The first 50 years of the North American Breeding Bird Survey

USGS Publications Warehouse

Sauer, John; Ziolkowski, David; Pardieck, Keith L.; Smith, Adam C.; Hudson, Marie-Anne R.; Rodriguez, Vicente; Berlanga, Humberto; Niven, Daniel; Link, William

2017-01-01

The vision of Chandler (Chan) S. Robbins for a continental-scale omnibus survey of breeding birds led to the development of the North American Breeding Bird Survey (BBS). Chan was uniquely suited to develop the BBS. His position as a government scientist had given him experience with designing and implementing continental-scale surveys, his research background made him an effective advocate of the need for a survey to monitor pesticide effects on birds, and his prominence in the birding community gave him connections to infrastructure—a network of qualified volunteer birders who could conduct roadside surveys with standardized point counts. Having started in the eastern United States and the Atlantic provinces of Canada in 1966, the BBS now provides population change information for ∼546 species in the continental United States and Canada, and recently initiated routes in Mexico promise to greatly expand the areas and species covered by the survey. Although survey protocols have remained unchanged for 50 years, the BBS remains relevant in a changing world. Several papers that follow in this Special Section of The Condor: Ornithological Advances review how the BBS has been applied to conservation assessments, especially in combination with other large-scale survey data. A critical feature of the BBS program is an active research program into field and analytical methods to enhance the quality of the count data and to control for factors that influence detectability. Papers in the Special Section also present advances in BBS analyses that improve the utility of this expanding and sometimes controversial survey. In this Perspective, we introduce the Special Section by reviewing the history of the BBS, describing current analyses, and providing summary trend results for all species, highlighting 3 groups of conservation concern: grassland-breeding birds, aridland-breeding birds, and aerial insectivorous birds.

New Sedimentary Records from Contourite Drifts on the West Antarctic Continental Margin: Reconstruction of Palaeoenvironmental Changes during the Late Quaternary by Combining an Integrated Chronostratigraphic Approach with Multi-Proxy Investigations

NASA Astrophysics Data System (ADS)

Hillenbrand, C. D.; Crowhurst, S.; Channell, J. E. T.; Williams, M.; Hodell, D. A.; Xuan, C.; Allen, C. S.; Ehrmann, W. U.; Graham, A. G. C.; Larter, R. D.

2016-12-01

Giant sediment drifts located on the continental rise west of the Antarctic Peninsula and in the Bellingshausen Sea contain a high-resolution archive of ice sheet history in West Antarctica and of palaeoceanographic changes in the Southern Ocean. However, previous studies on sediment cores recovered from these contourite drifts, including Ocean Drilling Program (ODP) Leg 178, were compromised by lack of reliable high-resolution chronological control. This shortcoming is mainly caused by the very low abundance of calcareous microfossils in the sediments that are required for applying radiocarbon dating and stable oxygen isotope (δ18O) stratigraphy. Moreover, sediments assumed to have been deposited during glacial periods consist almost entirely of terrigenous detritus, i.e. they lack even siliceous microfossils that could be utilised for biostratigraphic purposes. International Ocean Discovery Program (IODP) proposal 732-Full2 aims to obtain continuous, high-resolution records from sites on the West Antarctic sediment drifts and to develop reliable age models for them. The strategy for achieving the second objective is to use a range of chronostratigraphic techniques, including relative geomagnetic palaeointensity (RPI) and δ18O stratigraphy, on sedimentary sequences recovered from the shallowest parts of the drift crests, where the preservation of calcareous microfossils is expected be higher than in deeper water. Here we present preliminary results of multi-proxy investigations on new piston and box cores recovered from the proposed drill sites during site survey investigation cruise JR298 of the RRS James Clark Ross in 2015. Apart from the integrated chronological approach, the new cores augment previous assessments of palaeoenvironmental change on the West Antarctic continental margin during glacial-interglacial cycles of the Late Quaternary.

Toward a Continental-Scale Mesonet: USDA National Resources Conservation Service SCAN and SNOTEL System

NASA Astrophysics Data System (ADS)

Schaffer, G.; Marks, D.

2004-12-01

Since 1978 snow deposition and SWE in the inter-mountain western US have been monitored by the NRCS SNOTEL (SNOwpack TELemetry) system. This revolutionary network utilizes Meteorburst technology to telemeter data back to a central location in near real-time. With a pilot program starting in 1991, NRCS introduced SCAN (Soil Climate and Analysis Network) adding a focus on soil moisture and climate in regions outside the intermountain west. In the mid-1990's SNOTEL sites began to be augmented to match the full climate instrumentation (air temperature, humidity, solar radiation, wind, and soil moisture and temperature in addition to precipitation, snow depth and SWE) of the SCAN system. At present there are nearly 700 SNOTEL sites in 12 states in the western US and Alaska, and over 100 SCAN sites in 40 states, Puerto Rico, and several foreign countries. Though SNOTEL was originally a western snow-monitoring network, differences between SCAN and SNOTEL have largely disappeared. The combined SNOTEL/SCAN system provides a continental-scale mesonet to support river basin to continental scale hydro-climatic analysis. The system is flexible and based on off-the-shelf data recording technology, allowing instrumentation, sampling and averaging intervals to be specified by site conditions, issues, or scientific questions. Because of the NRCS data management structure, all sites have active telemetery and provide near real-time access to data through the internet. An ongoing research program is directed to improved instrumentation for measuring precipitation, snow depth and SWE, and soil moisture and temperature. Future directions include expansion of the network to be more comprehensive, and to develop focused monitoring efforts to more effectively observe elevational and regional gradients, and to capture high intensity hydro-climatic events such as potential flooding from convective storms and rain-on-snow.

An East Siberian ice shelf during the Late Pleistocene glaciations: Numerical reconstructions

NASA Astrophysics Data System (ADS)

Colleoni, Florence; Kirchner, Nina; Niessen, Frank; Quiquet, Aurélien; Liakka, Johan

2016-09-01

A recent data campaign in the East Siberian Sea has revealed evidence of grounded and floating ice dynamics in regions of up to 1000 m water depth, and which are attributed to glaciations older than the Last Glacial Maximum (21 kyrs BP). The main hypothesis based on this evidence is that a small ice cap developed over Beringia and expanded over the East Siberian continental margin during some of the Late Pleistocene glaciations. Other similar evidence of ice dynamics that have been previously collected on the shallow continental shelves of the Arctic Ocean have been attributed to the penultimate glaciation, i.e. Marine Isotopes Stage 6 (≈140 kyrs BP). We use an ice sheet model, forced by two previously simulated MIS 6 glacial maximum climates, to carry out a series of sensitivity experiments testing the impact of dynamics and mass-balance related parameters on the geometry of the East Siberian ice cap and ice shelf. Results show that the ice cap developing over Beringia connects to the Eurasian ice sheet in all simulations and that its volume ranges between 6 and 14 m SLE, depending on the climate forcing. This ice cap generates an ice shelf of dimensions comparable with or larger than the present-day Ross ice shelf in West Antarctica. Although the ice shelf extent strongly depends on the ice flux through the grounding line, it is particularly sensitive to the choice of the calving and basal melting parameters. Finally, inhibiting a merging of the Beringia ice cap with the Eurasian ice sheet affects the expansion of the ice shelf only in the simulations where the ice cap fluxes are not large enough to compensate for the fluxes coming from the Eurasian ice sheet.

Urban Heat Island phenomenon in extreme continental climate (Astana, Kazakhstan)

NASA Astrophysics Data System (ADS)

Konstantinov, Pavel; Akhmetova, Alina

2015-04-01

Urban Heat Island (UHI) phenomenon is well known in scientific literature since first half of the 19th century [1]. By now a wide number of world capitals is described from climatological point of view, especially in mid-latitudes. In beginning of XXI century new studies focus on heat island of tropical cities. However dynamics UHI in extreme continental climates is insufficiently investigated, due to the fact that there isn't large cities in Europe and Northern America within that climate type. In this paper we investigate seasonal and diurnal dynamics UHI intensity for Astana, capital city of Kazakhstan (population larger than 835 000 within the city) including UHI intensity changes on different time scales. Now (since 1998) Astana is the second coldest capital city in the world after Ulaanbaatar, Mongolia [3] For this study we use the UHI investigation technology, described in [2]. According to this paper, we selected three stations: one located into city in high and midrise buildings area (including extensive lowrise and high-energy industrial - LCZ classification) and two others located in rural site (sparsely built or open-set and lightweight lowrise according LCZ classification). Also these stations must be close by distance (less than 100 km) and altitude. Therefore, first for Astana city were obtained numerical evaluations for UHI climate dynamics, UHI dependence of synoptic situations and total UHI climatology on monthly and daily averages. References: 1.Howard, L. (1833) The Climate of London, Deduced from Meteorological Observations. Volume 2, London. 2.Kukanova E.A., Konstantinov P.I. An urban heat islands climatology in Russia and linkages to the climate change In Geophysical Research Abstracts, volume 16 of EGU General Assembly, pages EGU2014-10833-1, Germany, 2014. Germany. 3.www.pogoda.ru.net