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Modeling of geochemical interactions between acidic and neutral fluids in the Onikobe Geothermal Reservoir

Description: Two types of fluids are encountered in the Onikobe geothermal reservoir, one is neutral and the other is acidic (pH=3). It is hypothesized that acidic fluid might be upwelling along a fault zone and that an impermeable barrier might be present between the acidic and neutral fluid zones. We carried out reactive geothermal transport simulations using TOUGHREACT (Xu and Pruess, 1998 and 2001) to test such a conceptual model. One-dimensional models were used to study the geochemical behavior due to mixing of the two fluids. Mn-rich smectite precipitated near the mixing front and is likely to form an impermeable barrier between regions with acidic and neutral fluids.
Date: January 10, 2003
Creator: Todaka, Norifumi; Akasaka, Chitoshi; Xu, Tianfu & Pruess, Karsten
Partner: UNT Libraries Government Documents Department

New results on the resistivity structure of Merapi Volcano(Indonesia), derived from 3D restricted inversion of long-offsettransient electromagnetic data

Description: Three long-offset transient electromagnetic (LOTEM) surveyswerecarried out at the active volcano Merapi in Central Java (Indonesia)during the years 1998, 2000, and 2001. The measurements focused on thegeneral resistivity structure of the volcanic edifice at depths of 0.5-2km and the further investigation of a southside anomaly. The measurementswere insufficient for a full 3D inversion scheme, which could enable theimaging of finely discretized resistivity distributions. Therefore, astable, damped least-squares joint-inversion approach is used to optimize3D models with a limited number of parameters. The mode ls feature therealistic simulation of topography, a layered background structure, andadditional coarse 3D blocks representing conductivity anomalies.Twenty-eight LOTEM transients, comprising both horizontal and verticalcomponents of the magnetic induction time derivative, were analyzed. Inview of the few unknowns, we were able to achieve reasonable data fits.The inversion results indicate an upwelling conductor below the summit,suggesting hydrothermal activity in the central volcanic complex. Ashallow conductor due to a magma-filled chamber, at depths down to 1 kmbelow the summit, suggested by earlier seismic studies, is not indicatedby the inversion results. In conjunction with an anomalous-density model,derived from arecent gravity study, our inversion results provideinformation about the southern geological structure resulting from amajor sector collapse during the Middle Merapi period. The density modelallows to assess a porosity range andthus an estimated vertical salinityprofile to explain the high conductivities on a larger scale, extendingbeyond the foothills of Merapi.
Date: June 14, 2006
Creator: Commer, Michael; Helwig, Stefan, L.; Hordt, Andreas; Scholl,Carsten & Tezkan, Bulent
Partner: UNT Libraries Government Documents Department

ARM Climate Research Facility Spectral Surface Albedo Value-Added Product (VAP) Report

Description: This document describes the input requirements, output data products, and methodology for the Spectral Surface Albedo (SURFSPECALB) value-added product (VAP). The SURFSPECALB VAP produces a best-estimate near-continuous high spectral resolution albedo data product using measurements from multifilter radiometers (MFRs). The VAP first identifies best estimates for the MFR downwelling and upwelling shortwave irradiance values, and then calculates narrowband spectral albedo from these best-estimate irradiance values. The methodology for finding the best-estimate values is based on a simple process of screening suspect data and backfilling screened and missing data with estimated values when possible. The resulting best-estimate MFR narrowband spectral albedos are used to determine a daily surface type (snow, 100% vegetation, partial vegetation, or 0% vegetation). For non-snow surfaces, a piecewise continuous function is used to estimate a high spectral resolution albedo at 1 min temporal and 10 cm-1 spectral resolution.
Date: July 15, 2011
Creator: McFarlane, S; Gaustad, K; Long, C & Mlawer, E
Partner: UNT Libraries Government Documents Department

Solar and Infrared Radiation Station (SIRS) Handbook

Description: The Solar Infrared Radiation Station (SIRS) provides continuous measurements of broadband shortwave (solar) and longwave (atmospheric or infrared) irradiances for downwelling and upwelling components. The following six irradiance measurements are collected from a network of stations to help determine the total radiative flux exchange within the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility: • Direct normal shortwave (solar beam) • Diffuse horizontal shortwave (sky) • Global horizontal shortwave (total hemispheric) • Upwelling shortwave (reflected) • Downwelling longwave (atmospheric infrared) • Upwelling longwave (surface infrared)
Date: July 1, 2005
Creator: Stoffel, T
Partner: UNT Libraries Government Documents Department

Influence of faults on groundwater flow and transport at YuccaMountain, Nevada

Description: Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how faults influence groundwater flow pathways and regional-scale macrodispersion. The 3-D model has a unique grid block discretization that facilitates the accurate representation of the complex geologic structure present in faulted formations. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and varied in displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. Simulations show that upward head gradients can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities, and the presence of permeable fault zones or faults with displacement only, not necessarily by upwelling from a deep aquifer. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high- and low-permeability layers at faults, and from upward flow within high-permeability fault zones. Conversely, large-scale channeling can occur as a result of groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different from that of the water table gradient, and isolated zones of contaminants can occur at the water table downgradient. By conducting both 2-D and 3-D simulations, we show that the 2-D cross-sectional models traditionally used to examine flow in faulted formations may not be appropriate. In addition, the influence of a particular type of fault cannot be generalized; depending on the location where contaminants enter the saturated zone, faults may either enhance or inhibit vertical dispersion.
Date: October 7, 1999
Creator: Cohen, Andrew J.B. & Sitar, Nicholas
Partner: UNT Libraries Government Documents Department

The Design and Analysis of Salmonid Tagging Studies in the Columbia Basin : Volume XVII : Effects of Ocean Covariates and Release Timing on First Ocean-Year Survival of Fall Chinook Salmon from Oregon and Washington Coastal Hatcheries.

Description: Effects of oceanographic conditions, as well as effects of release-timing and release-size, on first ocean-year survival of subyearling fall chinook salmon were investigated by analyzing CWT release and recovery data from Oregon and Washington coastal hatcheries. Age-class strength was estimated using a multinomial probability likelihood which estimated first-year survival as a proportional hazards regression against ocean and release covariates. Weight-at-release and release-month were found to significantly effect first year survival (p < 0.05) and ocean effects were therefore estimated after adjusting for weight-at-release. Negative survival trend was modeled for sea surface temperature (SST) during 11 months of the year over the study period (1970-1992). Statistically significant negative survival trends (p < 0.05) were found for SST during April, June, November and December. Strong pairwise correlations (r > 0.6) between SST in April/June, April/November and April/December suggest the significant relationships were due to one underlying process. At higher latitudes (45{sup o} and 48{sup o}N), summer upwelling (June-August) showed positive survival trend with survival and fall (September-November) downwelling showed positive trend with survival, indicating early fall transition improved survival. At 45{sup o} and 48{sup o}, during spring, alternating survival trends with upwelling were observed between March and May, with negative trend occurring in March and May, and positive trend with survival occurring in April. In January, two distinct scenarios of improved survival were linked to upwelling conditions, indicated by (1) a significant linear model effect (p < 0.05) showing improved survival with increasing upwelling, and (2) significant bowl-shaped curvature (p < 0.05) of survival with upwelling. The interpretation of the effects is that there was (1) significantly improved survival when downwelling conditions shifted to upwelling conditions in January (i.e., early spring transition occurred, p < 0.05), (2) improved survival during strong downwelling conditions (Bakun units < -250). Survival decreased during weak downwelling ...
Date: May 1, 2001
Creator: Burgess, Caitlin & Skalski, John R.
Partner: UNT Libraries Government Documents Department

Combined Plate Motion and Density Driven Flow in the Asthenosphere beneath Saudi Arabia: Evidence from Shearwave Splitting and Seismic Anisotropy

Description: Mantle anisotropy along the Red Sea and across the Arabian Peninsula was analyzed using shear-wave splitting recorded by stations from three different seismic networks: the largest, most widely distributed array of stations examined across the Arabian Peninsula to date. Stations near the Gulf of Aqaba display fast orientations aligned parallel to the Dead Sea Transform Fault, most likely related to the strike-slip motion between Africa and Arabia However, most of our observations across Arabia are statistically the same (at a 95% confidence level), with north-south oriented fast directions and delay times averaging about 1.4 s. Since end-member models of fossilized anisotropy and present-day asthenospheric flow do not adequately explain these observations, we interpret them as a combination of plate and density driven flow in the asthenosphere. Combining northeast oriented flow associated with absolute plate motion with northwest oriented flow associated with the channelized Afar upwelling along the Red Sea produces a north-south resultant that matches the observations and supports models of active rifting.
Date: September 8, 2006
Creator: Hansen, S; Schwartz, S; Al-Amri, A & Rodgers, A
Partner: UNT Libraries Government Documents Department

Surface Energy Balance System (SEBS) Handbook

Description: A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system at the Southern Great Plains (SGP), North Slope of Alaska (NSA), Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes.
Date: February 14, 2011
Creator: Cook, DR
Partner: UNT Libraries Government Documents Department

Observed 1970-2005 cooling of summer daytime temperatures in coastal California

Description: The study evaluated 1948-2004 summer (JJA) mean monthly air temperatures for two California air basins: SoCAB and SFBA. The study focuses on the more rapid post-1970 warming period, and its daily T{sub min} and T{sub max} values were used to produce average monthly values and spatial distributions of trends for each air basins. Additional analyses included T{sub D} values at two NWS sites, SSTs, NCEP reanalysis sea-level pressures, and GCM T{sub ave}-values. Results for all California COOP sites together showed increased JJA T{sub ave}-values; asymmetric warming, as T{sub min}-values increase faster than T{sub max}-values; and thus decreased DTR values. The spatial distribution of observed SoCAB and SFBA T{sub max} values exhibited a complex pattern, with cooling in low-elevation coastal-areas open to marine air penetration and warming at inland areas. Results also showed that decreased DTR values in the valleys arose from small increases at 'inland' sites combined with large decreases at 'coastal' sites. Previous studies suggest that cooling JJA T{sub max}-values in coastal California were due to increased irrigation, coastal upwelling, or cloud cover, while the current hypothesis is that they arises from GHG-induced global-warming of 'inland' areas, which results in increased sea breeze flow activity. Sea level pressure trends showed increases in the oceanic Pacific High and decreases in the central-California Thermal Low. The corresponding gradient thus showed a trend of 0.02 hPa 100-km{sup -1} decade{sup -1}, supportive of the hypothesis of increased sea breeze activity. Trends in T{sub D} values showed a larger value at coastal SFO than at inland SEC, which indicative of increased sea breeze activity; calculated SST trends (0.15 C decade{sup -1}) could also have increase T{sub D}-values. GCM model Tave-values showed warming that decreases from 0.13 C decade{sup -1} at inland California to 0.08 C decade{sup -1} at coastal areas. Significant societal impacts may ...
Date: May 15, 2009
Creator: Lebassi, B.; Gonzalez, J.; Fabris, D.; Maurer, E.; Miller, N.; Milesi, C. et al.
Partner: UNT Libraries Government Documents Department

Parameterizations in high resolution isopycnal wind-driven ocean models. Final report, August 1, 1992--January 31, 1996

Description: Development of a general quasi-isopycnal code suitable for numerical experimentation and test of parameterizations was the main goal of the proposed research. A versatile ocean modeling system, which the authors refer to as the Thermodynamic Ocean Modeling System (TOMS) is the result of this effort. TOMS is based on an Arbitrary Lagrangian Eulerian (ALE) vertical coordinate and is a hybrid between isopycnal and z-coordinate models. The modeling system is designed for oceanic and coastal flows where the aspect ratio is small. As part of the development effort, the authors also proposed to implement and test new numerical schemes, parameterizations of boundary layer flow and development and implementation of mixed layer physics in this model. The addition objectives for the proposed research were: (1) incorporate various mixed layer parameterizations; (2) implement and test the positive definite Arakawa and Hsu, (1990) scheme; (3) recode a version of the model for a highly parallel architecture; (4) determine effects of various parameterizations of islands, and; (5) determine the correct lateral boundary condition for boundary layer currents, as for instance the Gulf Stream, and other western boundary currents.
Date: March 1, 1996
Creator: Jensen, T.G. & Randall, D.A.
Partner: UNT Libraries Government Documents Department

Final Report: High Spectral Resolution Atmospheric Emitted Radiance Studies with the ARM UAV

Description: The active participation in the Atmospheric Radiation Measurement (ARM) Unmanned Airborne Vehicle (UAV) science team that was anticipated in the grant proposal was indefinitely delayed after the first year due to a programmatic decision to exclude the high spectral resolution observations from the existing ARM UAV program. However, this report shows that substantial progress toward the science objectives of this grant have made with the help of separate funding from NASA and other agencies. In the four year grant period (including time extensions), a new high spectral resolution instrument has been flown and has successfully demonstrated the ability to obtain measurements of the type needed in the conduct of this grant. In the near term, the third water vapor intensive observing period (WVIOP-3) in October 2000 will provide an opportunity to bring the high spectral resolution observations of upwelling radiance into the ARM program to complement the downwelling radiance observations from the existing ARM AERI instruments. We look forward to a time when the ARM-UAV program is able to extend its scope to include the capability for making these high spectral resolution measurements from a UAV platform.
Date: December 31, 1999
Creator: Revercomb, Henry E.
Partner: UNT Libraries Government Documents Department

A Year of Radiation Measurements at the North Slope of Alaska Second Quarter 2009 ARM and Climate Change Prediction Program Metric Report

Description: In 2009, the Atmospheric Radiation Measurement (ARM) Program and the Climate Change Prediction Program (CCPP) have been asked to produce joint science metrics. For CCPP, the second quarter metrics are reported in Evaluation of Simulated Precipitation in CCSM3: Annual Cycle Performance Metrics at Watershed Scales. For ARM, the metrics will produce and make available new continuous time series of radiative fluxes based on one year of observations from Barrow, Alaska, during the International Polar Year and report on comparisons of observations with baseline simulations of the Community Climate System Model (CCSM).
Date: April 15, 2009
Creator: McFarlane, S. A.; Shi, Y. & Long, C. N.
Partner: UNT Libraries Government Documents Department

Geothermal Modeling of the Raft River Geothermal Field

Description: This interim report presents the results to date of chemical modeling of the Raft River KGRA. Earlier work indicated a northwest-southeast anomaly in the contours. Modeling techniques applied to more complete data allowed further definition of the anomaly. Models described in this report show the source of various minerals in the geothermal water. There appears to be a regional heat source that gives rise to uniform conductive heat flow in the region, but convective flow is concentrated near the upwelling in the Crook well vicinity. Recommendations are made concerning field expansion and additional work needed to refine the overall reservoir model.
Date: November 1, 1979
Creator: Overton, H.L.; Chaney, R.E.; McAtee, D.L. & Graham, D.L.
Partner: UNT Libraries Government Documents Department

Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon

Description: Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high amounts of radiocarbon ({sup 14}C), whereas equatorial waters are influenced by the upwelling of low {sup 14}C water and have relatively low concentrations of {sup 14}C. We use a 250-year record of {Delta}{sup 14}C in a coral from southwestern Puerto Rico along with previously published coral {Delta}{sup 14}C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and from other studies indicate that the influence of either of the two water masses can change considerably on interannual to interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric {sup 14}C changes, thus masking the Suess effect at this site. A mixing model produced using coral {Delta}{sup 14}C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and 1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible mechanism to explain the observed switches between relatively low and relatively high {Delta}{sup 14}C values in the coral radiocarbon records.
Date: December 5, 2006
Creator: Kilbourne, K H; Quinn, T M; Guilderson, T P; Webb, R S & Taylor, F W
Partner: UNT Libraries Government Documents Department

Contribution to the development of DOE ARM Climate Modeling Best Estimate Data (CMBE) products: Satellite data over the ARM permanent and AMF sites: Final Report

Description: To support the LLNL ARM infrastructure team Climate Modeling Best Estimate (CMBE) data development, the University of North Dakota (UND)'s group will provide the LLNL team the NASA CERES and ISCCP satellite retrieved cloud and radiative properties for the periods when they are available over the ARM permanent research sites. The current available datasets, to date, are as follows: the CERES/TERRA during 200003-200812; the CERES/AQUA during 200207-200712; and the ISCCP during 199601-200806. The detailed parameters list below: (1) CERES Shortwave radiative fluxes (net and downwelling); (2) CERES Longwave radiative fluxes (upwelling) - (items 1 & 2 include both all-sky and clear-sky fluxes); (3) CERES Layered clouds (total, high, middle, and low); (4) CERES Cloud thickness; (5) CERES Effective cloud height; (6) CERES cloud microphysical/optical properties; (7) ISCCP optical depth cloud top pressure matrix; (8) ISCCP derived cloud types (r.g., cirrus, stratus, etc.); and (9) ISCCP infrared derived cloud top pressures. (10) The UND group shall apply necessary quality checks to the original CERES and ISCCP data to remove suspicious data points. The temporal resolution for CERES data should be all available satellite overpasses over the ARM sites; for ISCCP data, it should be 3-hourly. The spatial resolution is the closest satellite field of view observations to the ARM surface sites. All the provided satellite data should be in a format that is consistent with the current ARM CMBE dataset so that the satellite data can be easily merged into the CMBE dataset.
Date: May 18, 2012
Creator: Xie, B; Dong, X & Xie, S
Partner: UNT Libraries Government Documents Department

Evaluation of Using Caged Clams to Monitor Contaminated Groundwater Exposure in the Near-Shore Environment of the Hanford Site 300 Area

Description: The Asiatic clam (Corbicula fluminea) has been identified as an indicator species for locating and monitoring contaminated groundwater in the Columbia River. Pacific Northwest National Laboratory conducted a field study to explore the use of caged Asiatic clams to monitor contaminated groundwater upwelling in the 300 Area near-shore environment and assess seasonal differences in uranium uptake in relation to seasonal flow regimes of the Columbia River. Additional objectives included examining the potential effects of uranium accumulation on growth, survival, and tissue condition of the clams. This report documents the field conditions and procedures, laboratory procedures, and statistical analyses used in collecting samples and processing the data. Detailed results are presented and illustrated, followed by a discussion comparing uranium concentrations in Asiatic clams collected at the 300 Area and describing the relationship between river discharge, groundwater indicators, and uranium in clams. Growth and survival, histology, and other sources of environmental variation also are discussed.
Date: January 31, 2008
Creator: Larson, Kyle B.; Poston, Ted M. & Tiller, Brett L.
Partner: UNT Libraries Government Documents Department

Summary of Temperature Data Collected to Improve Emergence Timing Estimates for Chum and Fall Chinook Salmon in the Lower Columbia River, 1998-2004 Progress Report.

Description: From 1999 through 2004, Pacific Northwest National Laboratory collected temperature data from within chum and fall Chinook salmon spawning gravels and the overlying river at 21 locations in the Ives Island area approximately 5 km downstream from Bonneville Dam. Sample locations included areas where riverbed temperatures were elevated, potentially influencing alevin development and emergence timing. The study objectives were to (1) collect riverbed and river temperature data each year from the onset of spawning (October) to the end of emergence (June) and (2) provide those data in-season to fisheries management agencies to assist with fall Chinook and chum salmon emergence timing estimates. Three systems were used over the life of the study. The first consisted of temperature sensors deployed inside piezometers that were screened to the riverbed or the river within chum and fall Chinook salmon spawning areas. These sensors required direct access by staff to download data and were difficult to recover during high river discharge. The second system consisted of a similar arrangement but with a wire connecting the thermistor to a data logger attached to a buoy at the water surface. This system allowed for data retrieval at high river discharge but proved relatively unreliable. The third system consisted of temperature sensors installed in piezometers such that real-time data could be downloaded remotely via radio telemetry. After being downloaded, data were posted hourly on the Internet. Several times during the emergence season of each year, temperature data were downloaded manually and provided to management agencies. During 2003 and 2004, the real-time data were made available on the Internet to assist with emergence timing estimates. Examination of temperature data reveals several important patterns. Piezometer sites differ in the direction of vertical flow between surface and subsurface water. Bed temperatures in upwelling areas are more stable during salmon spawning ...
Date: October 1, 2005
Creator: Arntzen, E.; Geist, D. & Hanrahan, T.
Partner: UNT Libraries Government Documents Department

Coastal Upwelling and Mass Mortalities of Fishes and Invertebrates in the Northeastern Gulf of Mexico during Spring and Summer 1998: Final Report

Description: Report of the mass mortality of fish and invertebrates resulting from the 1998 El Nino in the northeastern Gulf of Mexico. Mortality was linked to a condition of near anoxia caused by a confluence of unusual oceanographic stratification associated with coastal upwelling, algal proliferation, and climatic conditions.
Date: September 1999
Creator: Collard, Sneed B & Lugo-Fernandez, Alexis
Partner: UNT Libraries Government Documents Department

Response to"Analysis of the Treatment, by the U.S. Department of Energy, of the FEP Hydrothermal Activity in the Yucca Mountain Performance Assessment" by Yuri Dublyansky

Description: This paper presents a rebuttal to Dublyansky (2007), which misrepresents technical issues associated with hydrothermal activity at the proposed Yucca Mountain nuclear waste repository and their importance to the long-term performance of the repository. In this paper, questions associated with hydrothermal activity are reviewed and the justification for exclusion of hydrothermal activity from performance assessment is presented. The hypothesis that hydrothermal upwelling into the present-day unsaturated zone has occurred at Yucca Mountain is refuted by the unambiguous evidence that secondary minerals and fluid inclusions in the unsaturated zone formed in an unsaturated environment from downward percolating meteoric waters. The thermal history at Yucca Mountain, inferred from fluid inclusion and isotopic data, is explained in terms of the tectonic extensional environment and associated silicic magmatism. The waning of tectonic extension over millions of years has led to the present-day heat flux in the Yucca Mountain region that is below average for the Great Basin. The long time scales of tectonic processes are such that any effects of a resumption of extension or silicic magmatism on hydrothermal activity at Yucca Mountain over the 10,000-year regulatory period would be negligible. The conclusion that hydrothermal activity was incorrectly excluded from performance assessment as asserted in Dublyansky (2007) is contradicted by the available technical and regulatory information.
Date: November 17, 2008
Creator: Houseworth, J.E. & Hardin, E.
Partner: UNT Libraries Government Documents Department

Joint seismic-geodynamic-mineral physical modelling of African geodynamics: A reconciliation of deep-mantle convection with surface geophysical constraints

Description: Recent progress in seismic tomography provides the first complete 3-D images of the combined thermal and chemical anomalies that characterise the unique deep mantle structure below the African continent. With these latest tomography results we predict flow patterns under Africa that reveal a large-scale, active hot upwelling, or superplume, below the western margin of Africa under the Cape Verde Islands. The scale and dynamical intensity of this West African superplume (WASP) is comparable to that of the south African superplume (SASP) that has long been assumed to dominate the flow dynamics under Africa. On the basis of this new tomography model, we find the dynamics of the SASP is strongly controlled by chemical contributions to deep mantle buoyancy that significantly compensate its thermal buoyancy. In contrast, the WASP appears to be entirely dominated by thermal buoyancy. New calculations of mantle convection incorporating these two superplumes reveal that the plate-driving forces due to the flow generated by the WASP is as strong as that due to the SASP. We find that the chemical buoyancy of the SASP exerts a strong stabilising control on the pattern and amplitude of shallow mantle flow in the asthenosphere below the southern half of the African plate. The asthenospheric flow predictions provide the first high resolution maps of focussed upwellings that lie below the major centres of Late Cenozoic volcanism, including the Kenya domes and Hoggar massif that lies above a remnant plume head in the upper mantle. Inferences of sublithospheric deformation from seismic anisotropy data are shown to be sensitive to the contributions of chemical buoyancy in the SASP.
Date: August 22, 2008
Creator: Forte, A M; Quere, S; Moucha, R; Simmons, N A; Grand, S P; Mitrovica, J X et al.
Partner: UNT Libraries Government Documents Department

The continental margin is a key source of iron to the HNLC North Pacific Ocean

Description: Here we show that labile particulate iron and manganese concentrations in the upper 500m of the Western Subarctic Pacific, an iron-limited High Nutrient Low Chlorophyll (HNLC) region, have prominent subsurface maxima between 100-200 m, reaching 3 nM and 600 pM, respectively. The subsurface concentration maxima in particulate Fe are characterized by a more reduced oxidation state, suggesting a source from primary volcagenic minerals such as from the Kuril/Kamchatka margin. The systematics of these profiles suggest a consistently strong lateral advection of labile Mn and Fe from redox-mobilized labile sources at the continental shelf supplemented by a more variable source of Fe from the upper continental slope. This subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing, and is likely a key source of bioavailable Fe to the HNLC North Pacific.
Date: January 15, 2008
Creator: Lam, P. J. & Bishop, J. K. B
Partner: UNT Libraries Government Documents Department

Burial, remineralization and utilization of organic matter at the sea floor under a strong western boundary current. Final report, May 1, 1992--April 30, 1995

Description: The overall goals of this project were to quantify the rates of organic carbon export from the southern mid-Atlantic Bight and to quantify the rates at which carbon is exchanged between the inorganic and organic pools within the bottom sediments. This information is necessary to constrain the role of the oceans in the control of carbon dioxide released to the atmosphere in association with energy production. During this project, in situ benthic flux chamber incubations have been performed at six sites on the continental slope and rise adjacent to Cape Hatteras. Based on the analysis of the time-series samples recovered during each experiment, the sea floor exchange rates of the major biogenic elements, oxygen, carbon, nitrogen, phosphorus and silicon were calculated. From the estimated benthic flux rates and the ancillary pore water and sediment analyses, the deposition, remineralization and burial rates of organic carbon to the sea floor in this area was evaluated. This information has been incorporated into regional and global assessments of organic carbon fluxes to the deep sea.
Date: August 24, 1995
Creator: Jahnke, R.A.
Partner: UNT Libraries Government Documents Department

On the Estimation of Clear-Sky Upwelling Shortwave and Longwave

Description: Previous work (Long and Ackerman 2000; Long 2004) has concentrated on estimation of the downwelling clear-sky irradiances and the calculation of the effect of clouds on the downwelling radiative energy budget. However, cloud forcing is defined for the difference between clear- and cloudy-sky net radiation, which includes the upwelling components. Thus, if we are to estimate the surface radiative cloud forcing, the means must be developed to estimate what the upwelling shortwave and longwave irradiance would be if the clouds were not present. Estimation of the upwelling longwave (LW) is particularly troublesome in that the emitted upwelling LW is a function of the total surface energy exchange including latent and sensible heat, which is related to but not necessarily always totally driven by the radiative exchange alone, but also involves the evolving soil and vegetation properties and changes in soil moisture amounts.
Date: March 18, 2005
Creator: Long, C.N.
Partner: UNT Libraries Government Documents Department

Inversion of Multi-Angle Radiation Measurement

Description: Our need to reconcile models and measurements in an efficient manner that allows for the operational retrieval of particle sizes for a two layer cloud led us to develop a new method for calculating the Green's functions for radiative transfer. The method uses the fact that doubling/adding codes can be easily used to calculate internal radiation fields at arbitrarily high resolution. We have also determined that the adjoint downwelling and upwelling vector radiation fields are simply related to the usual downwelling and upwelling vector radiation fields so that the entire Green's function can be determined from a single calculation. The Green's functions have then been used to calculate the particle sizes in a two layer cloud that are consistent with both the reflectance and polarization measurements. This approach may be of use in other applications where adjoint calculations are used, particularly if multiangle measurements are being analyzed.
Date: March 18, 2005
Creator: Cairns, B.; Alexandrov, M. Lacis, A. & Carlson, B.
Partner: UNT Libraries Government Documents Department