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Articles 211 - 240 of 275

Full-Text Articles in Earth Sciences

Detrital-Zircon Geochronology Of The Metasedimentary Rocks Of North-Western Graham Land, David L. Barbeau Jr, Justin T. Davis, Kendra E. Murray, Victor Valencia, George E. Gehrels, Khandaker M. Zahid, David J. Gombosi Jan 2009

Detrital-Zircon Geochronology Of The Metasedimentary Rocks Of North-Western Graham Land, David L. Barbeau Jr, Justin T. Davis, Kendra E. Murray, Victor Valencia, George E. Gehrels, Khandaker M. Zahid, David J. Gombosi

Faculty Publications

Metasedimentary rocks constitute an important but comparatively poorly understood part of the Antarctic Peninsula. Herein we report single-grain U-Pb detrital-zircon ages from samples of the Trinity Peninsula and Botany Bay Groups of north-western Graham Land. All studied samples are dominated by a large and narrowly defined population of late Palaeozoic zircons. Significant early–middle Palaeozoic and minor Neoproterozoic and Mesoproterozoic sub-populations constitute the majority of pre-Carboniferous grains. These detrital-zircon age populations are consistent with sediment derivation entirely from western Gondwana sources. Despite the clear Gondwana signatures, our data suggest that the Trinity Peninsula Group province was either a parautochthonous peri-Gondwanan terrane …

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Global Distribution Of Atmospheric Phosphorus Sources, Concentrations And Deposition Rates, And Anthropogenic Impacts, Natalie Mahowald, Timothy D. Jickells, Alex R. Baker, Paulo Artaxo, Claudia R. Benitez-Nelson, Gilles Bergametti, Tami C. Bond, Ying Chen, David D. Cohen, Barak Herut, Nilgun Kubilay, Remi Losno, Chao Luo, Willy Maenhaut, Kenneth A. Mcgee, Gregory S. Okin, Ronald L. Siefert, Seigen Tsukuda Dec 2008

Global Distribution Of Atmospheric Phosphorus Sources, Concentrations And Deposition Rates, And Anthropogenic Impacts, Natalie Mahowald, Timothy D. Jickells, Alex R. Baker, Paulo Artaxo, Claudia R. Benitez-Nelson, Gilles Bergametti, Tami C. Bond, Ying Chen, David D. Cohen, Barak Herut, Nilgun Kubilay, Remi Losno, Chao Luo, Willy Maenhaut, Kenneth A. Mcgee, Gregory S. Okin, Ronald L. Siefert, Seigen Tsukuda

Faculty Publications

[1] A worldwide compilation of atmospheric total phosphorus (TP) and phosphate (PO4) concentration and deposition flux observations are combined with transport model simulations to derive the global distribution of concentrations and deposition fluxes of TP and PO4. Our results suggest that mineral aerosols are the dominant source of TP on a global scale (82%), with primary biogenic particles (12%) and combustion sources (5%) important in nondusty regions. Globally averaged anthropogenic inputs are estimated to be ∼5 and 15% for TP and PO4, respectively, and may contribute as much as 50% to the deposition over the oligotrophic ocean where productivity may …

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Forcing And Dynamics Of Seafloor-Water Column Exchange On A Broad Continental Shelf, William B. Savidge, Ann Gargett, Richard A. Jahnke, James R. Nelson, Dana K. Savidge, R Timothy Short, George Voulgaris Dec 2008

Forcing And Dynamics Of Seafloor-Water Column Exchange On A Broad Continental Shelf, William B. Savidge, Ann Gargett, Richard A. Jahnke, James R. Nelson, Dana K. Savidge, R Timothy Short, George Voulgaris

Faculty Publications

Relict sediments of elevated permeability characterize the majority of continental shelves globally (Emery, 1968). In these settings, interactions between benthic boundary layer (BBL) flows and seabed topography generate pressure fluctuations that drive advective and dispersive porewater transport, dramatically increasing the magnitude and variability of porewater solute and particulate exchange across the sediment-water interface (Huettel et al., 1996; Huettel and Rusch, 2000). On broad shallow shelves with a relatively large area-to-volume ratio, the seafloor’s role is magnified. Energetic events may reorganize bedforms across a significant fraction of the shelf, leading to altered exchange dynamics that may persist long after the organizing …

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Si Cycle In The Cariaco Basin, Venezuela: Seasonal Variability In Silicate Availability And The Si:C:N Composition Of Sinking Particles, Robert Thunell, Claudia R. Benitez-Nelson, Frank Muller-Karger, Laura Lorenzoni, Kent Fanning, Mary Scranton, Ramon Varela, Yrene Astor Oct 2008

Si Cycle In The Cariaco Basin, Venezuela: Seasonal Variability In Silicate Availability And The Si:C:N Composition Of Sinking Particles, Robert Thunell, Claudia R. Benitez-Nelson, Frank Muller-Karger, Laura Lorenzoni, Kent Fanning, Mary Scranton, Ramon Varela, Yrene Astor

Faculty Publications

[1] A 9‐year time series of water column and sediment trap measurements was used to examine silicon cycling within the anoxic Cariaco Basin. The dynamic hydrographic regime within Cariaco Basin results in strong seasonal changes in nutrient availability and the Si:C:N of sinking particles. Upwelling in early winter injects silicic acid (Si(OH)4= ) and nitrate (NO3−) rich waters into the photic zone which stimulates primary production and results in opal fluxes in excess of 4 mmol Si m−2 d−1. However, even during upwelling, surface waters tend to be depleted (μM) in both Si(OH)4= and NO3− as a result …

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High-Resolution Surveys Along The Hot Spot–Affected Galapagos Spreading Center: 1. Distribution Of Hydrothermal Activity, Edward T. Baker, Rachel M. Haymon, Joseph A. Resing, Scott M. White, Sharon L. Walker, Ken C. Macdonald, Ko-Ichi Nakamura Sep 2008

High-Resolution Surveys Along The Hot Spot–Affected Galapagos Spreading Center: 1. Distribution Of Hydrothermal Activity, Edward T. Baker, Rachel M. Haymon, Joseph A. Resing, Scott M. White, Sharon L. Walker, Ken C. Macdonald, Ko-Ichi Nakamura

Faculty Publications

The spatial density of hydrothermal activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on hydrothermal activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95o to 89o42'W (~560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge …

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Lateral Circulation And Suspended Sediment Transport In A Curved Estuarine Channel: Winyah Bay, Sc, Usa, Yong Hoon Kim, George Voulgaris Sep 2008

Lateral Circulation And Suspended Sediment Transport In A Curved Estuarine Channel: Winyah Bay, Sc, Usa, Yong Hoon Kim, George Voulgaris

Faculty Publications

Shipborne vertical profiles of flow and suspended sediment concentration collected on a transect, across a curved, nonsymmetrical estuarine channel are presented. Analysis of the transient cross-channel momentum balance equation shows that the lateral circulation pattern is controlled by the interaction between centrifugal and lateral baroclinic forcings although those two might not be necessarily in balance as suggested earlier by Seim and Gregg (1997). Instead, differential along-channel advection and local acceleration appear to influence greatly lateral circulation dynamics. During ebb when the water column is highly stratified, the interaction between centrifugal acceleration and opposite-directed lateral baroclinic forcing results in weak lateral …

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Characterizing Subpixel Variability Of Low Resolution Radiometer Derived Soil Moisture Using High Resolution Radar Data, Ujjwal Narayan, Venkataraman Lakshmi Jun 2008

Characterizing Subpixel Variability Of Low Resolution Radiometer Derived Soil Moisture Using High Resolution Radar Data, Ujjwal Narayan, Venkataraman Lakshmi

Faculty Publications

Soil moisture estimates obtained using passive remote sensing from satellite platforms often suffer from the drawback of coarse spatial resolution. In this current work, low resolution soil moisture estimates from passive remote sensing are fused with high resolution radar backscatter data to produce soil moisture change estimates at the spatial resolution of radar. More specifically, soil moisture estimated from AMSR-E and TMI (separate cases) for a single 50 km × 50 km pixel has been fused with TRMM-PR backscatter data at 5 km resolution to produce soil moisture change estimates at 5 km resolution. A brief sensitivity analysis has been …

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Oligocene Deep Water Export From The North Atlantic And The Development Of The Antarctic Circumpolar Current Examined With Neodymium Isotopes, Howie Scher, Ellen E. Martin Jan 2008

Oligocene Deep Water Export From The North Atlantic And The Development Of The Antarctic Circumpolar Current Examined With Neodymium Isotopes, Howie Scher, Ellen E. Martin

Faculty Publications

Neodymium (Nd) isotopes were measured on 181 samples of fossil fish teeth recovered from Oligocene toMiocene sections at Ocean Drilling Program Site 1090 (3700 m water depth) on Agulhas Ridge in the Atlanticsector of the Southern Ocean. A long-term decreasing trend toward less radiogenic Nd isotope compositionsdominates the record. This trend is interrupted by shifts toward more radiogenic compositions near the early/lateOligocene boundary and the Oligocene/Miocene boundary. Overall, eNd values at Agulhas Ridge are moreradiogenic than at other Atlantic locations, and are similar to those at Indian Ocean locations. The pattern ofvariability is remarkably similar to Nd isotope results from …

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Tidal Asymmetry And Residual Circulation Over Linear Sandbanks And Their Implication On Sediment Transport: A Process-Oriented Numerical Study, Rosario Sanay, George Voulgaris, John C. Warner Dec 2007

Tidal Asymmetry And Residual Circulation Over Linear Sandbanks And Their Implication On Sediment Transport: A Process-Oriented Numerical Study, Rosario Sanay, George Voulgaris, John C. Warner

Faculty Publications

A series of process-oriented numerical simulations is carried out in order to evaluate the relative role of locally generated residual flow and overtides on net sediment transport over linear sandbanks. The idealized bathymetry and forcing are similar to those present in the Norfolk Sandbanks, North Sea. The importance of bottom drag parameterization and bank orientation with respect to the ambient flow is examined in terms of residual flow and overtide generation, and subsequent sediment transport implications are discussed. The results show that although the magnitudes of residual flow and overtides are sensitive to bottom roughness parameterization and bank orientation, the …

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Hunting For Hydrothermal Vents Along The Galápagos Spreading Center, Rachel M. Haymon, Edward T. Baker, Joseph A. Resing, Scott M. White, Ken C. Macdonald Dec 2007

Hunting For Hydrothermal Vents Along The Galápagos Spreading Center, Rachel M. Haymon, Edward T. Baker, Joseph A. Resing, Scott M. White, Ken C. Macdonald

Faculty Publications

No abstract provided.

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Relationship Between Vegetation Biophysical Properties And Surface Temperature Using Multisensor Satellite Data, Seungbum Hong, Venkataraman Lakshmi, Eric Small Nov 2007

Relationship Between Vegetation Biophysical Properties And Surface Temperature Using Multisensor Satellite Data, Seungbum Hong, Venkataraman Lakshmi, Eric Small

Faculty Publications

Vegetation is an important factor in global climatic variability and plays a key role in the complexinteractions between the land surface and the atmosphere. This study focuses on the spatial and temporalvariability of vegetation and its relationship with land–atmosphere interactions. The authors have analyzedthe vegetation water content (VegWC) from the Advanced Microwave Scanning Radiometer for EOS(AMSR-E), the leaf area index (LAI), the normalized difference vegetation index (NDVI), the land surfacetemperature (Ts), and the Moderate Resolution Imaging Spectroradiometer (MODIS). Three regions,which have climatically differing characteristics, have been selected: the North America Monsoon System(NAMS) region, the Southern Great Plains (SGP) region, and …

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Sea Surface Pco2‐Sst Relationships Across A Cold‐Core Cyclonic Eddy: Implications For Understanding Regional Variability And Air‐Sea Gas Exchange, Feizhou Chen, Wei‐Jun Cai, Claudia R. Benitez-Nelson, Yongchen Wang May 2007

Sea Surface Pco2‐Sst Relationships Across A Cold‐Core Cyclonic Eddy: Implications For Understanding Regional Variability And Air‐Sea Gas Exchange, Feizhou Chen, Wei‐Jun Cai, Claudia R. Benitez-Nelson, Yongchen Wang

Faculty Publications

[1] This study is designed to improve the understanding of how biologically productive, cold‐core cyclonic eddies affect sea surface pCO2 in the lee of the main Hawaiian Islands in the subtropical North Pacific Gyre. We identified three unique relationships between pCO2 and sea surface temperature (SST). A positive correlation between pCO2 and SST was observed in the waters surrounding the eddy suggesting surface CO2 is controlled primarily by thermodynamics. In contrast, a negative relationship was observed within the eddy core as a result of the upwelling of CO2‐enriched subsurface waters. A third relationship existed throughout the rest …

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Particulate Organic Carbon Fluxes Along Upwelling‐Dominated Continental Margins: Rates And Mechanisms, Robert Thunell, Claudia R. Benitez-Nelson, Ramon Varela, Yrene Astor, Frank Muller‐Karger Mar 2007

Particulate Organic Carbon Fluxes Along Upwelling‐Dominated Continental Margins: Rates And Mechanisms, Robert Thunell, Claudia R. Benitez-Nelson, Ramon Varela, Yrene Astor, Frank Muller‐Karger

Faculty Publications

[1] Time series sediment trap samples were used to examine the rates and mechanisms of particulate organic carbon (POC) flux at three continental margin locations, Santa Barbara Basin, Cariaco Basin, and Guaymas Basin, marked by seasonal upwelling and high primary production. The mean POC flux in Santa Barbara Basin (0.096 g m−2 d−1) is nearly twice that of Cariaco Basin and 4 times higher than that in Guaymas Basin, with all three sites having POC fluxes significantly higher than the open ocean average (0.007 g m−2 d−1). In Cariaco Basin, the only site with available primary production numbers, there is …

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Submarine Volcanic Morphology Of The Western Galapagos Based On Em300 Bathymetry And Mr1 Side-Scan Sonar, Jennifer B. Glass, D J. Fornari, Hillary F. Hall, Allison A. Cougan, Heidi A. Berkenbosch, Mark L. Holmes, Scott M. White, Giorgio De La Torre Mar 2007

Submarine Volcanic Morphology Of The Western Galapagos Based On Em300 Bathymetry And Mr1 Side-Scan Sonar, Jennifer B. Glass, D J. Fornari, Hillary F. Hall, Allison A. Cougan, Heidi A. Berkenbosch, Mark L. Holmes, Scott M. White, Giorgio De La Torre

Faculty Publications

A compilation of high-resolution EM300 multibeam bathymetric and existing MR1 side-scan sonar data was used to investigate the volcanic morphology of the flanks of the western Galapagos Islands. The data portray an assortment of constructional volcanic features on the shallow to deep submarine flanks of Fernandina, Isabela, and Santiago Islands, including rift zones and groups of cones that are considered to be the primary elements in constructing the archipelagic apron. Ten submarine rift zones were mapped, ranging in length from 5 to 20 km, comparable in length to western Canary Island rift zones but significantly shorter than Hawaiian submarine rift …

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Application Of The Empirical Mode Decomposition And Hilbert-Huang Transform To Seismic Reflection Data, Bradley M. Battista, Camelia C. Knapp, Tom Mcgee, Vaughn Goebel Jan 2007

Application Of The Empirical Mode Decomposition And Hilbert-Huang Transform To Seismic Reflection Data, Bradley M. Battista, Camelia C. Knapp, Tom Mcgee, Vaughn Goebel

Faculty Publications

Advancements in signal processing may allow for improved imaging and analysis of complex geologic targets found in seismic reflection data. A recent contribution to signal processing is the empirical mode decomposition (EMD) which combines with the Hilbert transform as the Hilbert- Huang transform (HHT). The EMD empirically reduces a time series to several subsignals, each of which is input to the same time-frequency environment via the Hilbert transform. The HHT allows for signals describing stochastic or astochastic processes to be analyzed using instantaneous attributes in the time-frequency domain. The HHT is applied herein to seismic reflection data to: (1) assess …

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A New View Of Ridge Segmentation And Near-Axis Volcanism At The East Pacific Rise, 8˚–12˚N, From Em300 Multibeam Bathymetry, Scott M. White, Rachel M. Haymon, S M. Carbotte Dec 2006

A New View Of Ridge Segmentation And Near-Axis Volcanism At The East Pacific Rise, 8˚–12˚N, From Em300 Multibeam Bathymetry, Scott M. White, Rachel M. Haymon, S M. Carbotte

Faculty Publications

New, high-resolution bathymetry for the East Pacific Rise between 8˚N and 12˚N was collected over a6 km wide swath centered on the ridge axis using the 30 kHz Simrad EM300 multibeam system. Thecoverage area corresponds latitudinally to the designated Ridge2000 Integrated Studies Site (ISS) for fastspreading ridges. The EM300 data, gridded at 30 m latitude by 50 m longitude, represent a greater than 4Ximprovement in horizontal resolution over previously available multibeam data and a 2X improvement indepth resolution. The new bathymetry was used to update the locations and hierarchy of ridge offsets forthis area. Among the many applications for this …

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Subtidal Inner Shelf Currents Off Cartagena De Indias, Caribbean Coast Of Colombia, Mauro Maza, George Voulgaris, Bulusu Subrahmanyam Nov 2006

Subtidal Inner Shelf Currents Off Cartagena De Indias, Caribbean Coast Of Colombia, Mauro Maza, George Voulgaris, Bulusu Subrahmanyam

Faculty Publications

Seasonal trends in inner shelf subtidal circulation off the coast of Cartagena de Indias, Colombia, are examined through the analysis of current profiles, hydrographic, meteorological and satellite data collected from 1999 to 2002. During the dry season (December–April) the water column is well-mixed and along-shelf currents flow southwestward following the steady trade winds. In the rainy season (May –November) the water column experiences continuous events of stratification and the along-shelf currents flow northeastward, opposing the weak southwestward winds. In the dry season the along shelfcirculation is mostly driven by wind forcing, while in the rainy season, the circulation is set …

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A Nd Isotopic Study Of Southern Sourced Waters And Indonesian Throughflow At Intermediate Depths In The Cenozoic Indian Ocean, Ellen E. Martin, Howie Scher Sep 2006

A Nd Isotopic Study Of Southern Sourced Waters And Indonesian Throughflow At Intermediate Depths In The Cenozoic Indian Ocean, Ellen E. Martin, Howie Scher

Faculty Publications

We present Nd isotopic data for fossil fish teeth recovered from the past 40 m.y. at ODP Site 757, currentlylocated at 1650m water depth on the Ninetyeast Ridge in the Indian Ocean. Although Site 757 sits in a regionstrongly influenced by weathering inputs from the Himalayas and volcanic inputs from the Indonesian arc, the pattern of Nd isotopic variations does not appear to respond to these potential sources of Nd. Instead, secular variations correlate to changes in the composition of intermediate to deep water masses bathing thesite and circulation patterns in the Indian Ocean. From ~40 to 10 Ma, eNd …

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Long-Term Volumetric Eruption Rates And Magma Budgets, Scott M. White, Joy A. Crisp, Frank J. Spera Mar 2006

Long-Term Volumetric Eruption Rates And Magma Budgets, Scott M. White, Joy A. Crisp, Frank J. Spera

Faculty Publications

A global compilation of 170 time-averaged volumetric volcanic output rates (Qe) is evaluated in terms of composition and petrotectonic setting to advance the understanding of long-term rates of magma generation and eruption on Earth. Repose periods between successive eruptions at a given site and intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>104 years) data were available. More silicic compositions, rhyolites and andesites, have a more limited range of eruption rates than basalts. Even when high Qe values contributed by flood basalts (9 ± 2 10[1]1 km3/yr) are removed, there is a trend in decreasing average Qe …

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Cross-Shore Variation Of Wind-Driven Flows On The Inner Shelf In Long Bay, South Carolina, United States, Benjamin T. Gutierrez, George Voulgaris, Paul A. Work Mar 2006

Cross-Shore Variation Of Wind-Driven Flows On The Inner Shelf In Long Bay, South Carolina, United States, Benjamin T. Gutierrez, George Voulgaris, Paul A. Work

Faculty Publications

The cross-shore structure of subtidal flows on the inner shelf (7 to 12 m water depth) of Long Bay, South Carolina, a concave-shaped bay, is examined through the analysis of nearly 80 days of near-bed (1.7–2.2 m above bottom) current observations acquired during the spring and fall of 2001. In the spring and under northeastward winds (upwelling favorable) a two-layered flow was observed at depths greater than 10 m, while closer to the shore the currents were aligned with the wind. The two-layered flow is attributed to the presence of stratification, which has been observed under similar conditions in the …

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The Effects Of Satellite-Derived Vegetation Cover Variability On Simulated Land–Atmosphere Interactions In The Nams, Toshi Matsui, Venkataraman Lakshmi, Eric Small Jan 2005

The Effects Of Satellite-Derived Vegetation Cover Variability On Simulated Land–Atmosphere Interactions In The Nams, Toshi Matsui, Venkataraman Lakshmi, Eric Small

Faculty Publications

Substantial evolution of Normalized Difference Vegetation Index (NVDI)-derived vegetation cover (Fg)exists in the southwestern United States and Mexico. The intraseasonal and wet-/dry-year fluctuations of Fgare linked to observed precipitation in the North American monsoon system (NAMS). The manner in whichthe spatial and temporal variability of Fg influences the land–atmosphere energy and moisture fluxes, andassociated likelihood of moist convection in the NAMS regions, is examined. For this, the regional climatemodel (RCM) is employed, with three different Fg boundary conditions to examine the influence ofintraseasonal and wet-/dry-year vegetation variability. Results show that a strong link exists between evaporativefraction (EF), surface temperature, and …

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New Standards For Reducing Gravity Data: The North American Gravity Database, William J. Hinze, Carlos Aiken, John Brozena, Bernard Coakley, David Dater, Guy Flanagan, Rene Forsberg, Thomas Hildenbrand, G. Randy Keller, James N. Kellogg, Robert Kucks, Xiong Li, Andre Mainville, Robert Morin, Mark Pilkington, Donald Plouff, Dhananjay Ravat, Daniel Roman, Jamie Urrutia-Fucugauchi, Marc Veronneau, Michael Webring, Daniel Winester Jan 2005

New Standards For Reducing Gravity Data: The North American Gravity Database, William J. Hinze, Carlos Aiken, John Brozena, Bernard Coakley, David Dater, Guy Flanagan, Rene Forsberg, Thomas Hildenbrand, G. Randy Keller, James N. Kellogg, Robert Kucks, Xiong Li, Andre Mainville, Robert Morin, Mark Pilkington, Donald Plouff, Dhananjay Ravat, Daniel Roman, Jamie Urrutia-Fucugauchi, Marc Veronneau, Michael Webring, Daniel Winester

Faculty Publications

The North American gravity database as well as databases from Canada, Mexico, and the United States are being revised to improve their coverage, versatility, and accuracy. An important part of this effort is revising procedures for calculating gravity anomalies, taking into account our enhanced computational power, improved terrain databases and datums, and increased interest in more accurately defining long-wavelength anomaly components. Users of the databases may note minor differences between previous and revised database values as a result of these procedures. Generally, the differences do not impact the interpretation of local anomalies but do improve regional anomaly studies. The most …

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Analysis Of Process Controls In Land Surface Hydrological Cycle Over The Continental United States, Tajdarul Hassan Syed, Venkataraman Lakshmi, Evan Paleologos, Dag Lohmann, Kenneth Mitchell, James S. Famiglietti Nov 2004

Analysis Of Process Controls In Land Surface Hydrological Cycle Over The Continental United States, Tajdarul Hassan Syed, Venkataraman Lakshmi, Evan Paleologos, Dag Lohmann, Kenneth Mitchell, James S. Famiglietti

Faculty Publications

The paper uses two years (1997–1999) of data from the North American Land Data Assimilation System at National Centers for Environmental Prediction to analyze the variability of physical variables contributing to the hydrological cycle over the conterminous United States. The five hydrological variables considered in this study are precipitation, top layer soil moisture (0–10 cm), total soil moisture (0–200 cm), runoff, and potential evaporation. There are two specific analyses carried out in this paper. In the first case the principal components of the hydrological cycle are examined with respect to the loadings of the individual variables. This helps to ascertain …

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Geomorphic Analysis Of Tidal Creek Networks, Karyn Inez Novakowski, Raymond Torres, L Robert Gardner, George Voulgaris May 2004

Geomorphic Analysis Of Tidal Creek Networks, Karyn Inez Novakowski, Raymond Torres, L Robert Gardner, George Voulgaris

Faculty Publications

The purpose of this study is to determine if concepts in terrestrial channel network analysis provide insight on intertidal creek network development and to present new metrics for their analysis. We delineated creek network geometry using high-resolution digital images of intertidal marsh near Georgetown, South Carolina. Analyses reveal that intertidal creek networks may be topologically random. Length-area relationships suggest that salt marsh and terrestrial networks have similar scaling properties, although the marsh networks are more elongate than terrestrial networks. To account for recurrent water exchange between creek basins at high tide, we propose that the landscape unit of geomorphic analyses …

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Effects Of Low Tide Rainfall On Intertidal Zone Material Cycling, Raymond Torres, Miguel A. Goni, George Voulgaris, Charles R. Lovell, James T. Morris Jan 2004

Effects Of Low Tide Rainfall On Intertidal Zone Material Cycling, Raymond Torres, Miguel A. Goni, George Voulgaris, Charles R. Lovell, James T. Morris

Faculty Publications

Sediment transport by rainfall-runoff processes is well documented for terrestrial landscapes but few studies have focused on rainfall-runoff effects in intertidal areas. Here we present geochemical analyses performed on sediment samples collected during low tide irrigation experiments, and tidal channel turbidity measurements taken during natural rainfall over North Inlet Marsh, South Carolina. Order of magnitude approximations indicate that a single 10 minute storm may entrain 8-15% of the local annual average sediment accumulation. This rainfall-entrained material is enriched in organic nitrogen and marine algal matter, and therefore of high nutritional quality.

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Links Between Snow Cover, Surface Skin Temperature, And Rainfall Variability In The North American Monsoon System, Toshi Matsui, Venkataraman Lakshmi, Eric Small Jun 2003

Links Between Snow Cover, Surface Skin Temperature, And Rainfall Variability In The North American Monsoon System, Toshi Matsui, Venkataraman Lakshmi, Eric Small

Faculty Publications

The influence of land–atmosphere interactions on the variability of the North American monsoon system(NAMS) is investigated using the Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder(TOVS) Pathfinder, the Climate Prediction Center (CPC) gauge precipitation, and observed snow water equivalent(SWE). Three hypotheses are tested regarding the connection between land surface variables and precipitationin the NAMS region. First, there is a weak negative correlation between 1 April SWE and subsequent surfacetemperature in the southern Rocky Mountains (SRM) region. However, this connection persists only until Juneand, therefore, cannot directly influence monsoon rainfall in July and August. Second, there is a negativecorrelation between SRM …

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Eocene To Miocene Magnetostratigraphy, Biostratigraphy, And Chemostratigraphy At Odp Site 1090 (Sub-Antarctic South Atlantic), J E T Channell, S Galeotti, Ellen E. Martin, K Billups, Howie Scher, J S. Stoner May 2003

Eocene To Miocene Magnetostratigraphy, Biostratigraphy, And Chemostratigraphy At Odp Site 1090 (Sub-Antarctic South Atlantic), J E T Channell, S Galeotti, Ellen E. Martin, K Billups, Howie Scher, J S. Stoner

Faculty Publications

At Ocean Drilling Program (ODP) Site 1090 (lat 42854.89S, long 8854.09E) locatedin a water depth of 3702 m on the Agulhas Ridge in the sub-Antarctic South Atlantic, ~300 m of middle Eocene to middle Miocenesediments were recovered with the advancedpiston corer (APC) and the extendedcore barrel (XCB). U-channel samplesfrom the 70–230 meters composite depth(mcd) interval provide a magnetic polaritystratigraphy that is extended to 380 mcd byshipboard whole-core and discrete sampledata. The magnetostratigraphy can be interpretedby the fit of the polarity-zone patternto the geomagnetic polarity time scale(GPTS) augmented by isotope data andbioevents with documented correlation tothe GPTS. Three normal-polarity subchrons(C5Dr.1n, C7Ar.1n, …

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Influence Of A Cyclonic Eddy On Microheterotroph Biomass And Carbon Export In The Lee Of Hawaii, Robert R. Bidigare, Claudia R. Benitez-Nelson, Carrie L. Leonard, Paul D. Quay, Michael L. Parsons, David G. Foley, Michael P. Seki Mar 2003

Influence Of A Cyclonic Eddy On Microheterotroph Biomass And Carbon Export In The Lee Of Hawaii, Robert R. Bidigare, Claudia R. Benitez-Nelson, Carrie L. Leonard, Paul D. Quay, Michael L. Parsons, David G. Foley, Michael P. Seki

Faculty Publications

[1] A multi‐platform sampling strategy was used to investigate carbon cycling in a cold‐core eddy that formed in the lee of Hawaii during September 2000. Microheterotroph biomass and 234Th‐derived carbon export rates within the eddy were 2 to 3 times higher than those observed for adjacent waters. If this eddy is representative of other cyclonic eddies that are frequently formed in the lee of Hawaii, then eddy activity may significantly enhance the areal efficiency of the biological pump and facilitate the transfer of organic carbon to organisms inhabiting the mesopelagic and abyssal‐benthic zones of this subtropical ecosystem.

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Probing Tectonic Topography In The Aftermath Of Continental Convergence In Central Europe, S Cloetingh, F Horvath, C Dinu, R A. Stephenson, G Bertotti, G Bada, L Matenco, D Garcia-Castellanos, P Andriessen, R Wortel, W Spakman, V Mocanu, C Langereis, W Krijgsman, J Fokkema, G Drykoningen, B Ambrosius, F Neubauer, L Fodor, T Dunai, E Willingshofer, A Nador, K Leever, M Tarapoanca, I Panea, I Vasiliev, G Paicu, A Van Der Hoven, James H. Knapp, Camelia C. Diaconescu, St Freimueller Mar 2003

Probing Tectonic Topography In The Aftermath Of Continental Convergence In Central Europe, S Cloetingh, F Horvath, C Dinu, R A. Stephenson, G Bertotti, G Bada, L Matenco, D Garcia-Castellanos, P Andriessen, R Wortel, W Spakman, V Mocanu, C Langereis, W Krijgsman, J Fokkema, G Drykoningen, B Ambrosius, F Neubauer, L Fodor, T Dunai, E Willingshofer, A Nador, K Leever, M Tarapoanca, I Panea, I Vasiliev, G Paicu, A Van Der Hoven, James H. Knapp, Camelia C. Diaconescu, St Freimueller

Faculty Publications

Continental topography is at the interface of processes taking place at depth in the Earth,at its surface,and above it.Topography influences society, not only in terms of slow processes of landscape change and earthquakes,but also in terms of how it affects climate.The Pannonian Basin–Carpathian Orogen System in Central and Eastern Europe represents a key natural laboratory for the development of a new generation of models for ongoing orogeny and its effect on continental topography development (Figure 1).This system comprises some of the best documented sedimentary basins in the world,located within the Alpine orogenic belt, at the transition between the western European …

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Magmatic Subsidence Of The East Pacific Rise (Epr) At 18˚14'S Revealed Through Fault Restoration Of Ridge Crest Bathymetry, S M. Carbotte, William B F Ryan, Wen Jin, Marie-Helene Cormier, Eric Bergmanis, John Sinton, Scott M. White Jan 2003

Magmatic Subsidence Of The East Pacific Rise (Epr) At 18˚14'S Revealed Through Fault Restoration Of Ridge Crest Bathymetry, S M. Carbotte, William B F Ryan, Wen Jin, Marie-Helene Cormier, Eric Bergmanis, John Sinton, Scott M. White

Faculty Publications

The fault restoration technique of De Chabalier and Avouac [1994] is applied to an ultra-highresolution bathymetry data set from the East Pacific Rise (EPR) at 18140S. Fault offsets are calculated and subtracted from the original seafloor bathymetry to examine the morphology of the unfaulted seafloor surface within an area encompassing the ridge axis 400 [1] 1600 m in dimension. The restored topography reveals a gently sloping seafloor 200 m wide, which slopes 5 inward toward the spreading axis. We attribute this inward sloping seafloor to subsidence within the axial trough due to subsurface magmatic deflation. The vertical deformation field extracted …

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