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Economic considerations for expanded feeding of livestock in the Pacific NorthwestGrimshaw, Paul R. 24 June 1971 (has links)
Several agricultural and related industry groups in the Pacific
Coast states have expressed concern about the competitive position
of these states in the production of feed grains and livestock products.
This study was directed toward the investigation of these
concerns.
In order to permit the real world situation, with its accompanying
multivariable reality, to be reduced to workable size, a
linear programming model was designed. The 48 contiguous states
were divided into five regions with smaller regions in the western
United States to permit a more detailed analysis of the West.
The quantities of feed grains produced in each state were
determined and summed for the states in a region. The quantities
of fed beef, pork, broilers, turkeys, eggs, and milk (the products
of the major grain consuming classes of livestock) demanded in each
state were computed.
A matrix of transportation costs between regions was developed
for feed grains and for the livestock products of the model. Regional weighted average prices received by farmers for each feed grain and
for each livestock product were determined.
The model was then utilized to indicate production of all the
livestock products required for consumption by region at the least
cost of producing the products.
Optimal solutions were obtained using 1968 and 1969 relative
prices and these solutions were analyzed. The analysis indicates
that generally the states which are deficit in beef, pork, broiler,
and egg production have a slight economic advantage in producing
these products for local consumption until the locally produced feed
supply is utilized. Each region in the model produced the milk consumed
in that region. Region I (Oregon and Washington) has traditionally
been self-sufficient in turkey production, and Region III
(California) has been a turkey exporting state. According to the
model, both of these regions should import the turkey consumed in
the region to derive optimum economic benefits. These conclusions
are based on the relative prices and transportation costs that
existed in 1968 and 1969.
After the solutions were obtained, the price of wheat in Region I
was varied using a parametric procedure available with the linear
programming package. Results of this analysis using 1968 and 1969
relative prices were described. The parametric analysis indicated
that at the 1968 price of wheat in Region I more than twice the
quantity of wheat allocated to livestock feeding in the basic model
could have been economically utilized and would have reduced costs
of producing the livestock products consumed in Region I.
The 1969 wheat price in Region I was sufficiently low that the
parametric analysis indicated an allocation of over four times the
quantity used in the basic model for livestock feeding. The basic
model utilized 1,043,000 tons of wheat for livestock feeding.
It can be concluded from the analysis that Region I could have
utilized much larger quantities of wheat for livestock feeding than
was allocated for feeding in the basic model. Based on the relative
feed ingredient costs that existed in 1968, Region I producers of
pork, broilers, eggs, and milk are competitive with other regions
in supplying the quantities of these products demanded for regional
consumption.
The 1969 relative prices made Region I even more competitive
in producing pork, broilers, eggs, and milk, and added beef production
as an economically advantageous alternative.
These conclusions are based only on feed ingredient and transportation
costs. If non-feed costs and relative feeder cattle costs
for beef production are included, Region I producers appear to have
a slight margin for producing beef,for local consumption until
locally produced feed supplies are exhausted. / Graduation date: 1972
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Character of the diatom assemblage spanning a depositional transition in the Eastern Equatorial Pacific Ocean at 6.6 MaBrookshire, Brian Neville, Jr. 17 February 2005 (has links)
Approximately 6.6 million years ago in the Eastern Equatorial Pacific a large increase in biogenic mass accumulation rates (MARs) occurred. This increased level of biogenic mass accumulation persisted until about 4.4 Ma at which time levels returned to those similar to before the transition at 6.6 Ma. The exact nature of the change that facilitated this transition in biogenic MARs, however, was not understood. Here we present the results of a study which characterizes the diatom assemblage spanning the depositional transition at 6.6 Ma from sediments taken from ODP Hole 850B. A close inspection of lithology reveals a clear change in lithology from a diatom nannofossil ooze to a nannofossil diatom ooze at 6.6 Ma. This transition is immediately followed by the occurrence of laminated diatom ooze (LDO). Diatom absolute abundance data reveals three levels of productivity associated with pre-transitional, post-transitional, and LDO formational sediments. An increase in the absolute abundance of Thalassionema nitzschioides was the major contributor to the formation of post-transitional, and LDO sediments. The known ecological preferences of this species indicate an overall increase in nutrient availability followed by sporadic changes in nutrient availability. These changes in nutrient availability could be associated with the establishment, or increase in strength, of an upwelling cell and/or the increase in nutrients made available via upwelling due to a shoaling of the thermocline.
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Development of an expert system for irrigation and fertilization management in the Pacific NorthwestCao, Weidong 23 October 1992 (has links)
Recent advances in computer technology have made possible the
development of expert systems. Expert systems are computer programs that
perform at the level of a human expert. Expert systems can help integrate and
apply diverse sources of information and expertise to problems of integrated
crop management. A prototype Crop Management eXpert (CMX) system has
been developed. The primary goal of CMX is to provide recommendations on
optimal irrigation and fertilization scheduling for wheat production in the Pacific
Northwest. This system can be used by farmers and/or extension agents.
OUS II Shell has been used as a implementation tool. To build this rule - based
expert system, a development strategy, commonly used in the construction of
expert systems, consisting of 1 ) identification; 2) conceptualization; 3)
formalization; 4) implementation; and 5) testing was applied.
CMX is composed of modules for irrigation and fertilization management.
For irrigation management, CMX is mainly involved in the irrigation scheduling
which is the major part of irrigation management. Irrigation strategies have been
applied in irrigation decision making. For each strategy, timing criteria which
generally consist of management allowed depletion, soil water potential, leaf
water potential, and water stress indices have been used. The system provides
farmers with irrigation scenarios which determine when and how much water to
apply.
CMX represents an integration of conventional computing and expert
systems technology designed to provide expert recommendations enabling
farmers to obtain the best return on their water and fertilizer investment. For
fertilization management, a variety of variables have been taken into considered.
Crop growth stages, soil moisture, nutrient analysis, protein requirement, and
application methods are important factors for the fertilizer decision making.
Several constraints have been used in optimal fertilizer advice.
CMX can focus only on relevant information, thus reducing the problem
space to a manageable size and significantly, improving the efficiency of the
system. The facility of the expert system to explain the decision-making process
enables users to better understand the underlying assumptions, facts, and
reasoning used to generate recommendations. The CMX prototype
demonstrates the feasibility of employing expert systems technology in
agricultural applications.
CMX has been validated and evaluated. The survey results showed that
this prototype was successful in capturing domain experts' knowledge as rules
and providing advice on the irrigation and fertilization management for wheat. / Graduation date: 1993
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Distribution of Pacific herring spawn in Yaquina Bay, Oregon, and observations on mortality through hatchingSteinfeld, James David 02 September 1971 (has links)
Studies were conducted during late winter and spring of 1970 to
establish the extent of spawning of Pacific herring (Clupea harengus
pallasi Valenciennes) in the Yaquina estuary, and to define the degree
of egg mortality on certain substrates. Routine surveillance of the
north shore of the estuary provided information on the length of the
spawning season, the number of separate spawnings which occurred,
the extent of spawning into brackish water, and the types of substrates
utilized for spawn deposition.
Random sampling of egg deposits at specific locations within the
estuary, and at frequent intervals following deposition provided estimates
of spawn mortality on two commonly used plant substrates,
Fucus sp. and Zostera sp. These included estimates of the amount of
eggs removed from the substrates prior to commencement of hatching,
and estimates of the mortality among eggs which remained attached
to the substrates. One series of samplings of a deposit of eggs on
Fucus was designed to establish the extent of bird predation on the
eggs.
Results from the spawn survey indicated that at least five
separate spawnings occurred during the season. Initial spawning took
place on February 5 in the lower estuary (from the south jetty to a
point three miles upriver from the mouth). Subsequent spawnings
occurred in the third, fifth, sixth, and seventh weeks following this
initial deposition, and appeared to take place exclusively in the middle
and upper estuary (from three and one half miles to ten miles upriver
from the mouth). Among the substrates observed with eggs Fucus
appeared to be the most extensively utilized, while localized deposits
were noted on Zostera, bare rocks and pilings. Spawning was predominantly
located on substrates lying above mean lower low water.
Analysis of the samples collected from four populations of eggs
deposited on Fucus, and one population deposited on Zostera revealed
that egg removal was extreme during the period of incubation. Recorded
losses from initially sampled populations of eggs on Fucus
ranged from 78% to 1OO% based on sample means. A 9l% loss was recorded
for the one Zostera population sampled.
A comparison of a protected with an unprotected segment of a
sampled population on Fucus indicated that birds contributed at least
80% to the removal of eggs from the unprotected segment. The observed
presence of birds on all of the sampling areas when eggs were
present suggests that predators accounted for the extensive losses
from these areas.
Analysis of the ratios of dead eggs to the total number of eggs in
samples collected from Fucus substrates provided estimates of natural
mortality. Low rates of mortality (about 20%) were recorded for two
populations sampled during a period in which the weather was cool and
moist, while considerably higher rates (about 50%) were observed in
samples from a population exposed to a dry and relatively warm climate.
Dessication of eggs was therefore indicated as a significant
cause of mortality of eggs remaining attached to substrates exposed to
drying conditions in the atmosphere.
In addition to these field studies, a study was conducted in the
laboratory to define the effects, on the survival of herring eggs to
hatching, of combinations of three environmental parameters: temperature,
salinity, and exposure to air. Groups of artificially fertilized
eggs were incubated in the 18 test environments provided by the different
combinations of three temperatures, three salinities, and exposure
and non-exposure to air. Survival of eggs to hatching remained
high (from 60% to 86% of total eggs in each environment) except for
eggs incubated in the highest temperature ( 11 °C.) and subjected to
eight hour exposure periods. Average survival in these environments
was 5.2% and 24.2% (for two replicates). These observations lend
support to the findings from the field sampling studies that survival
of herrings eggs can be tenuous when subjected to exposure to air. / Graduation date: 1972
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Cetacean Distribution in Ecuador: Spatial and Temporal Relationships between Ocean Fronts and the Apex Predator PopulationO'Hern, Julia 14 March 2013 (has links)
Five line transect surveys for marine mammals were conducted offshore of mainland Ecuador and the Galápagos Islands from 2008-2011. These data were used in conjunction with MODIS (Moderate Resolution Imaging Spectroradiometer) observations of ocean color and sea surface temperature (SST) to assess spatial and temporal relationships between surface oceanographic features and cetacean distribution within the Eastern Equatorial Pacific (EEP). Results from this study indicated that oceanographic processes affected cetacean distribution on inter-annual, seasonal, and weekly to monthly time scales. The spatial scales on which these processes affect cetacean distribution are small, the smallest associations being found at 4 km2 bin sizes, as well as 9 km2 and 36 km2 bin sizes. By utilizing ocean color and SST data from the MODIS instrument and analyzing variability of these parameters in addition to average concentration, cetacean distribution within the region was related to the locations of frontal boundaries. Cetaceans were grouped into two categories based on the trophic level and relative depths at which they forage. Cetaceans feeding nearer the ocean surface and lower on the trophic scale were generally found in cooler waters of higher average chlorophyll concentration and elevated variability. Those cetaceans feeding higher on the trophic scale and lower in the water column (mesopelagic and bathypelagic depths) were sighted within relatively warmer waters of reduced temperature variability near areas of high chlorophyll variability (though less variable and lower in average chlorophyll than surface feeding cetaceans), with little spatial and temporal lag between peak surface chlorophyll concentration and cetacean presence.
The EEP is a biologically productive region with many competing economic and environmental interests. Ecuador is home to one of the largest artisenal fishing fleets in South America, and entanglement of various cetacean species has been a known issue for several decades (Félix and Haase, 2006; Castro and Rosero, 2010). Seismic exploration, shipping, and tourism are also found on the busy waterways surrounding both mainland Ecuador and the archipelago. The results of this study provide additional insight into the mesoscale processes affecting the distribution and habitat use of cetaceans within the EEP and South American waters and to support ongoing ecosystem management efforts.
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Examination of the Molecular Epidemiology, Expansion, Population Structure, and Virulence of the Emerging Fungal Pathogen,<italic>Cryptococcus gattii</italic> in the United StatesByrnes, Edmond John January 2010 (has links)
<p><italic>Cryptococcus gattii</italic> has been actively emerging and adapting to the climates and environment in western North America, bringing with it life-threatening disease to humans and animals. Through systematic investigations of the dynamics of this pathogen in the United States, by studying outbreaks and individual cases, our studies have aimed to increase the understanding of the expansion, emergence, pathogenicity, molecular epidemiology, population structure, and speciation dynamics of this organism that had previously been largely restricted to tropical and sub-tropical climates of the world. <BR> <BR></p><p>Molecular sequence typing has revealed that there are four distinct <italic>C. gattii</italic> molecular types (VGI-VGIV). A major focus of our efforts to examine this pathogen in the United States surrounds the unprecedented <italic>C. gattii</italic> outbreak that emerged in British Columbia, Canada in 1999 and has since expanded throughout the Pacific Northwest region of the United States (Chapters 2, 3). This outbreak has resulted in a large number of infections in both humans and animals, including a high percentage of otherwise healthy individuals. The outbreak isolates are primarily molecular type VGIIa (the major genotype), VGIIb (the minor genotype), or VGIIc, a novel genotype that emerged in Oregon in approximately 2005. <BR> <BR></p><p>The North American Pacific Northwest harbors one of the highest incidences of <italic>C. gattii</italic> infections. In an expansion of molecular epidemiology and population analysis of both MLST and VNTR markers, we show that the VGIIc group is clonal and hypothesize it arose recently. The VGIIa/c outbreak lineages are sexually fertile and studies support ongoing recombination in the global VGII population. This illustrates two hallmarks of emerging outbreaks: high clonality and the emergence of novel genotypes via recombination. In macrophage and murine infections, the novel VGIIc genotype and VGIIa/major isolates from the United States are highly virulent compared to similar non-outbreak VGIIa/major-related isolates. Molecular analysis distinguishes clonal expansion of the VGIIa/major outbreak genotype from related but distinguishable less-virulent genotypes isolated from other geographic regions. Our evidence documents emerging hypervirulent genotypes in the United States that may expand further and provides insight into the possible molecular and geographic origins of the outbreak. <BR> <BR></p><p>While the outbreak is a significant public health concern, an overlooked but considerable disease burden attributable to <italic>C. gattii</italic> among HIV/AIDS patients in Southern California has also occurred (chapter 4). In our studies, we examined the molecular epidemiology, population structure, and virulence attributes of <italic>C. gattii</italic> isolates collected from a cohort of HIV/AIDS patients in Los Angeles County, California. We show that these isolates consist almost exclusively of VGIII molecular type (>93%), in contrast to the vast majority of VGII molecular type isolates found in the outbreak region. Based on molecular phylogenetic analysis, the global VGIII population structure can be divided into two groups, VGIIIa and VGIIIb. We show that isolates from the Californian patients are virulent in murine and macrophage models of infection, with VGIIIa significantly more virulent than VGIIIb. Several VGIII isolates are highly fertile and able to produce large numbers of spores that may serve as infectious propagules. Based on molecular analysis, the a and α VGIII MAT locus alleles are largely syntenic with limited rearrangements compared to the known VGI (a/α) and VGII (α) <italic>MAT</italic> loci, but each has unique characteristics including a distinct deletion flanking the 5' VGIII <italic>MAT</italic> <bold>a</bold> alleles. Fingerprinting analyses of the MAT locus shows that the α allele is more heterogeneous than the <bold>a</bold>allele. Our studies indicate that <italic>C. gattii</italic> VGIII is endemic in Southern California, with other isolates originating from the neighboring regions of Mexico, and in some rarer cases from Oregon and Washington state. Given that >1,000,000 cases of cryptococcal infection and >620,000 attributable mortalities occur annually in the context of the global AIDS pandemic, our findings suggest a significant burden of <italic>C. gattii</italic> infection in AIDS patients may be unrecognized, with potential prognostic and therapeutic implications. These results signify the need to classify pathogenic Cryptococcus cases and highlight possible host differences among the <italic>C. gattii</italic> molecular types, influencing infection of immunocompetent (VGI/VGII) vs. immunocompromised (VGIII/VGIV) hosts. <BR> <BR></p><p>In 2007, the first confirmed case of <italic>Cryptococcus gattii</italic> was reported in the state of North Carolina, USA (chapter 5). An otherwise healthy HIV- male patient presented with a large upper thigh cryptococcoma in February, which was surgically removed and the patient was started on long-term high-dose fluconazole treatment. In May of 2007, the patient presented to the emergency room with seizures. Magnetic resonance imaging revealed two large CNS lesions found to be cryptococcomas based on brain biopsy. Prior chest CT imaging had revealed small lung nodules indicating that <italic>C. gattii</italic> spores or desiccated yeast were likely inhaled into the lungs and dissemination occurred to both the leg and CNS. The patient's travel history included a visit throughout the San Francisco, California region in September-October of 2006, consistent with acquisition during this time period. Cultures from both the leg and brain biopsies were subjected to analysis. Both isolates were <italic>C. gattii</italic>, VGI molecular type. Based on molecular studies and virulence in a heterologous host model, the leg and brain isolates are identical, but the two differed in mating fertility. Two clinical isolates, one from a transplant recipient in San Francisco and the other from Australia, were identical to the North Carolina isolate at all markers tested. Closely related isolates that differ at only one or a few noncoding markers are present in the Australian environment. Our findings support a model in which <italic>C. gattii</italic> VGI was transferred from Australia to California, possibly though an association with its common host plant <italic>E. camaldulensis</italic>, and the patient was exposed in San Francisco and returned to present with disease in North Carolina. <BR> <BR></p><p>To elucidate the speciation dynamics between molecular types VGII and VGIII and what influence nuclear and mitochondrial genomes have on intracellular proliferation and hyoervirulence, we conducted a comprehensive analysis of progeny sets between these molecular types, including progeny sets of VGII<bold>a</bold> x VGIIIα and VGIIα x VGIII<bold>a</bold> crosses (chapter 6). Our analysis reveals that spore viability is exceedingly low, supporting that these are distinct species. We also found that the mitochondrial genome of virulent strains may be necessary but not fully sufficient to confer virulence characteristics. These studies show that each molecular type is likely a distinct species, which was further supported by high levels of diploid or aneuploid progeny, and also shed light into the possible control that both the mitochondrial and nuclear genomes may play in hypervirulence of <italic>C. gattii</italic> outbreak genotypes. Future analyses of both the regions regulating the virulence and also the generation of progeny sets between other species will further address the roles of both speciation and virulence evolution in <italic>C. gattii</italic>. <BR> <BR></p><p>Overall, the studies documented in this dissertation have increased the understanding of molecular epidemiology, population structures, fertility, phenotypic characteristics, virulence characterizations, and speciation of this expanding and emerging fungal pathogen in the United States. This dissertation adds a foundation to the studies of <italic>C. gattii</italic> in the United States and enables future research to be conducted in several critical areas to better understand and ultimately influence surveillance, prognosis, and treatment of patients and animals in future years.</p> / Dissertation
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Distribution of CH4 and N2O in natural waters around TaiwanTseng, Hsiao-Chun 29 July 2005 (has links)
Abstract
Methane (CH4) and nitrous oxide (N2O) are not only important but also long-lived greenhouse gases. Unfortunately, in Taiwan, although there are some data on CH4 emission from rivers and lakes there is no data about N2O emission from rivers, lakes and coasts. So this study investigated CH4 and N2O distribution in natural waters around Taiwan.
In Taiwan, the average CH4 concentration in rivers is about 3082¡Ó12399nM (n=152). The average CH4 concentration in mountain lakes is about 2899¡Ó7291nM (n=51). The average CH4 concentration in lower elevation lakes and reservoirs is about 1825¡Ó2755nM ppmv (n=95). The average CH4 concentration in near-shore waters is about 36.7¡Ó285nM (n=476). The CH4 distribution is rivers> mountain lakes>low-elevation lakes and reservoirs >seawater. In southeastern China, the average CH4 concentration in rivers is about 1029¡Ó2487nM ppmv (n=36). The average CH4 concentration of samples taken from rivers in southeastern China is lower than Taiwan rivers. But the highest CH4 concentration of all samples is in Chih-Kan river of southeastern China (14914nM), due to uneven population distribution as well as different levels of development among cities and suburbs.
In Taiwan, the average N2O concentration in rivers is about 32.8¡Ó69.1nM (n=58). In southeastern China, the average N2O concentration in rivers is about 29.7¡Ó9.05nM (n=36). The average N2O concentration in Taiwanese rivers is higher than found in southeastern China. This is likely because farmers in Taiwan use more synthetic fertilizers so the soil becomes full of N element, and then rivers and rains rinse the soil. This process has increased the concentration of N and N2O in rivers.
In summer, the average CH4 and N2O concentrations in northern Taiwan Strait are about 3.27¡Ó2.42nM and 7.22¡Ó0.62nM (n=7), respectively; and the average CH4 and N2O fluxes are about 0.17¡Ó0.43£gmol/m2/h and 0.14¡Ó0.26 £gmol/m2/h, respectively. The average CH4 and N2O concentrations in southern Taiwan Strait are about 3.35¡Ó1.97nM and10.31¡Ó2.51nM (n=30), respectively; and the average CH4 and N2O fluxes are about 0.04¡Ó0.09£gmol/m2/h and 0.19¡Ó0.22 £gmol/m2/h, respectively.
In winter, the average CH4 and N2O concentrations in northern Taiwan Strait are about 4.74¡Ó1.43nM and 8.41¡Ó0.46nM (n=9), respectively; and the average CH4 and N2O fluxes are about 0.10¡Ó0.14£gmol/m2/h and 0.008¡Ó0.033 £gmol/m2/h, respectively. The average CH4 and N2O concentrations in southern Taiwan Strait are about 4.70¡Ó2.42nM and 8.36¡Ó0.97nM (n=17), respectively; and the average CH4 and N2O fluxes are about 0.17¡Ó0.46£gmol/m2/h and 0.11¡Ó0.12 £gmol/m2/h, respectively. Taiwan Strait is a source of CH4 and N2O regardless of whether it is summer or winter.
In summer, the average CH4 and N2O concentrations in the South China Sea are about 4.34¡Ó2.33nM and 8.23¡Ó1.5nM (n=55), respectively; and the average CH4 and N2O fluxes are about 0.33¡Ó0.35£gmol/m2/h and 0.20¡Ó0.24 £gmol/m2/h, respectively. It is a source of CH4 and N2O to the atmosphere.
In summer, the average CH4 and N2O concentrations in the West Philippines Sea are about 3.18¡Ó1.57nM and 4.64¡Ó0.39nM (n=60), respectively; and the average CH4 and N2O fluxes are about 0.23¡Ó0.33£gmol/m2/h and -0.28¡Ó0.30 £gmol/m2/h, respectively. It is a source of CH4 but a sink of N2O to the atmosphere.
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Distribution and Modeling of Chlorofluorocarbons in the Northwestern Pacific OceanHwang, Hsing- Chih 17 January 2002 (has links)
Because CFC-11 and CFC-12 are extremely stable and purely anthropogenic and the CFCs enter the ocean through air-sea exchange at the sea surface, they serve as good tracers for studying the oceans. Since CFCs and tritium share similar characteristics such as their anthropogenic production, inertness to biological activities, a tritium box model applied to the North Atlantic Ocean by J. L. Sarmiento in 1983 is used to study the distribution of CFCs in the Northwest Pacific. This thesis attempts to use this model to calculate the past concentrations of CFCs in the atmosphere assuming equilibrium distribution between the surface ocean waters and the atmosphere in the source region of the oceans. The results may allow us to check the history of CFCs in the atmosphere.
The data used in this thesis are those reported by NOAA from three cruises: CO2-87 and CGC92 along 165oE and CO2-88 along 170oW, all from 40o to 10oN. This latitude range avoids the complex gyres and the sea-ice which may limit the air-sea exchange in the North, and also avoids the upwelling in the equatorial region. The outcrop of the 26.0 sq water is located at longitude about 52o-53oN along 165oE, but is located at about 40oN along 170oW. The outcrop will move southward in winter. The vertical distribution pattern of CFCs is similar to that of oxygen. Concentrations of CFCs in ocean water increase as potential temperature and salinity decrease. High latitudes of low temperature and salinity have high CFC solubility and high air-sea exchange rates, and are presumably the major areas for input of CFCs into the seawater. As the CFCs in the air increase over the years the concentrations of CFCs in the surface ocean water also increase but decrease with water depth. The solubility, F, of CFCs is a function of both temperature and salinity, but temperature prevails. The F values for CFC-11 and CFC-12 from 10o to 50oN along 165oE are 5.86-16.0 and 1.70-4.15 mmole/kg/ atm, respectively. The values along 170oW are, respectively, 6.60-22.2 and 1.89-5.55 mmole/kg/atm. The solubility of CFC-11 is about four times as large as that of CFC-12. The solubility of CFCs along 170oW is about 1.4 times along 165oE because of temperature and salinity differences. The exchange rate in the time scale for =1 year ranges 0.85-1.3 yr-1, CFC-11 has a mean of 0.99 yr-1, CFC-12 has a mean of about 1.04 yr-1. Along the isopycnal surface of sq=26.0, the highest exchange rate between two boxes is 2.34 yr-1, the lowest 0.06 yr-1. Based on the calculated concentrations of CFCs in the surface seawater from the atmospheric value in the past, apparent ages of the Mode Waters are similar for both CFC-11 and CFC-12. The apparent age along 165oE at 10oN is about 17 years on the defined isocypnal surface, and it is about 15 years along 170oW at 10oN. The spreading rate of CFCs in the Northwest Pacific is thus about 172-221 km/yr. During the 17 years, the annual increase in influx to the seawater is about 0.12 pM/kg/yr for CFC-11, and about 0.059 pM/kg/yr for CFC-12. The error in calculating atmosphere CFCs in the past is about 11 % for CFC-11, and 6 % for CFC-12.
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Modeling of 226Ra in the North Pacific OceanWu, Shih-Jen 18 February 2002 (has links)
A total of 10 vertical 226Ra profiles from the North Pacific was published as part of the GEOSECS program. These profiles are located on an east-west section along ~300N. The purpose of this thesis is to use one-dimensional and two-dimensional diffusion-advection models to estimate some important geochemical parameters.
There are some discrepancies between the modeling results and the observed tracer distributions due to restrictions on end-members in the models. Fitting the observed data to the model, one obtains values of the Z* between 0.8 and 1.0 km from potential temperature and that of JBa/w between 0.0020 and 0.0064 nM/kg/m from Ba.
Where Ba profiles are available, the corresponding 226Ra profiles are similar from the surface to the deep water, showing a linear correlation with a slope at 0.22 dpm/100nM or 4.4¡Ñ10-9 for the Ra/Ba molal ratio. The slope has an intercept of 0.48 nM/kg on the Ba axis.
That 226Ra is linearly correlated with Ba from surface water to deep water is probably because algebraic sum of the production term and the radioactive decay is nearly constant. Thus the revised model has a form equivalent to that for Ba.
Where Ba profiles are available, one can fit the observed data to the model to obtain the needed parameters with (JRa-£fCRa)/JBa as a constant. The upwelling velocity, w, obtained from model calculations on the Ba profiles is: 3.8 m/yr at 204; 4.8 m/yr at 212; 3.5 m/yr at 226, 1.2 m/yr at 224. These values are consistent with those (1 to 12m/yr) reported for the Pacific deep water based on other methods.
Fitting 226Ra profile data to the vertical one-dimensional diffusion-advection model for the in-situ production rate, J, and the associated upwelling velocity, w, one finds that J and w are coupled with a negative correlation. This is consistent with that reported in the literature.
Profiles from the northeast Pacific show a deep Ra maximum, with an ¡§excess¡¨ which extends westward while decreasing and finally vanishing in the northwest Pacific near Japan. A horizontal diffusivity of 5 ¡Ñ105 cm2/s was obtained based on this ¡§excess¡¨ 226Ra with a horizontal 1-D model by Chung and Craig (1980). A numerical finite-difference method is applied to the 2-D model fitting on the potential temperature data for the horizontal diffusivity, Kx. A Kx of 4.58 ¡Ñ105 cm2/s is obtained within the depth range of 1000m to 3000m. The value is 4.82 ¡Ñ105 cm2/s for the depth range from 1000m to 4000m. These two approaches yield nearly identical results.
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Character of the diatom assemblage spanning a depositional transition in the Eastern Equatorial Pacific Ocean at 6.6 MaBrookshire, Brian Neville, Jr. 17 February 2005 (has links)
Approximately 6.6 million years ago in the Eastern Equatorial Pacific a large increase in biogenic mass accumulation rates (MARs) occurred. This increased level of biogenic mass accumulation persisted until about 4.4 Ma at which time levels returned to those similar to before the transition at 6.6 Ma. The exact nature of the change that facilitated this transition in biogenic MARs, however, was not understood. Here we present the results of a study which characterizes the diatom assemblage spanning the depositional transition at 6.6 Ma from sediments taken from ODP Hole 850B. A close inspection of lithology reveals a clear change in lithology from a diatom nannofossil ooze to a nannofossil diatom ooze at 6.6 Ma. This transition is immediately followed by the occurrence of laminated diatom ooze (LDO). Diatom absolute abundance data reveals three levels of productivity associated with pre-transitional, post-transitional, and LDO formational sediments. An increase in the absolute abundance of Thalassionema nitzschioides was the major contributor to the formation of post-transitional, and LDO sediments. The known ecological preferences of this species indicate an overall increase in nutrient availability followed by sporadic changes in nutrient availability. These changes in nutrient availability could be associated with the establishment, or increase in strength, of an upwelling cell and/or the increase in nutrients made available via upwelling due to a shoaling of the thermocline.
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