Dissertations / Theses: 'Equatorial and regional oceanography' – Grafiati (2024)

Abstract:

Small changes in the sea-surface temperature (SST) distribution in the equatorial Pacific are known to have large consequences for the weather and climate on regional and even global scales. A detailed knowledge of the SST patterns is therefore necessary if we are to understand and predict these effects thoroughly. Effort has hitherto been concentrated on understanding the dynamics of the West Pacific Warm Pool, but attention is now shifting to the eastern Cold Tongue region. This thesis contributes to this programme by assessing the impact of one unique feature of the equatorial East Pacific; the presence on the equator of a medium-sized island group - the Galapagos Archipelago. The project is carried through using a combination of: in situ oceanographic data from ships and moorings; satellite SST and colour images; and diagnostics from both a sophisticated ocean general circulation model and a simplified (reduced gravity) model. Each model was run both with and without a representation of the Galapagos. It is found that under typical conditions the islands form the eastern boundary of the cold tongue; the lowest equatorial SSTs in the Pacific occur on the west coast of the main islands of the group. As well as preventing the cold tongue from extending any further east, the islands also cool the sea surface still further for a distance of some 1000 km to the west. For the first 100 km or so the cooling is of the order of 1C; on the larger scale it is more like 0.1C. This cooling is a result of hydraulically enhanced upwelling of waters from the Equatorial Undercurrent (EUC), which is best explained by a Bernoulli-type (non-rotating, non-linear) theory. This theory also predicts that water parcels in the EUC will undergo vertical excursions on their passage around the north and south coasts of the islands; these excursions are observed in at least one numerical model. Downstream of the archipelago the EUC usually reunites and executes inertial oscillations, meandering about the equator. Transport in the EUC is also reduced because of the presence of the islands, by 30-50% to the east of the islands and by up to 20% to the west. Enhanced SST variability north and south of the equator immediately to the west of the Galapagos indicates that tropical instability waves (TIWs) are more active here than they would be were the islands absent. This is due to a pair of barotropically unstable zonal jets originating at the northern and southern tips of the islands. These jets are consistent with the theory of low-frequency flow past equatorial islands on the beta plane (which predicts that the South Equatorial Current will split into two such jets on encountering such an island), although weaker jets are found in models with no representation of the Galapagos. As with the cold tongue, the islands form the eastern limit of the region where these jets are found.

Abstract:

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Includes bibliographical references (v.2, leaves 339-351).
This study focuses on the zonal weakening, eastern termination and seasonal variations of the Atlantic equatorial undercurrent (EUC). The main and most original contribution of the dissertation is a detailed analysis of the Atlantic EUC simulated by Philander and Pacanowski's (1986)general circulation model (GCM), which provides a novel description of the dynamical regimes governing various regions of a nonlinear stratified undercurrent. Only in a narrow deep western region of the simulation does one find an approximately inertial regime corresponding to zonal acceleration. Elsewhere frictional processes cannot be ignored. The bulk of the mid-basin model EUC terminates in the overlying westward surface flow while only a small fraction (the deeper more inertial layers) terminates at the eastern coast. In agreement with observations, a robust feature of the GCM not present in simpler models is the apparent migration of the EUC core from above the thermocline in the west to below it in the east. In the GCM, this happens because the eastward flow is eroded more efficiently by vertical friction above the base of the thermocline than by lateral friction at greater depths. This mechanism is a plausible one for the observed EUC. A scale analysis using a depth scale which decreases with distance eastwards predicts the model zonal transition between western inertial and eastern inertio-frictional regimes. Historical and recent observations and simple models of the equatorial and coastal eastern undercurrents are reviewed, and a new analysis of current measurements in the eastern equatorial Atlantic is presented. Although the measurements are inadequate for definitive conclusions, they suggest that Lukas' (1981) claim of a spring surge of the Pacific EUC to the eastern coast and a seasonal branching of the EUC into a coastal southeastward undercurrent may also hold for the Atlantic Ocean. To improve the agreement between observed and modelled strength of the eastern undercurrent, it is suggested that the eddy coefficient of horizontal mixing should be reduced in future GCM simulations.
by Sophie Huguette Claire Wacongne.
Ph.D.

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and, Woods Hole Oceanographic Institution, 1991.
GRSN 539404
Includes bibliographical references (p. 207-216).
by Esther Collison Brady.
Ph.D.

Abstract:

INDEJE, MATAYO. Prediction and Numerical Simulation of the Regional Climate of Equatorial Eastern Africa. (Under the direction of Dr. Fredrick H. M. Semazzi.). The objective in this investigation was to provide a better understanding of the mechanisms and physical processes responsible for climate variability over the equatorial eastern Africa, and explore potential for short-term climate prediction. Both statistical and numerical methods have been employed in this research. Application of cluster analysis yields 8 and 9 hom*ogeneous climatic zones respectively for the variability of the annual and seasonal rainfall. Regions that are prone to drought or floods during the different phases of El Niño-Southern Oscillation (ENSO) are delineated. Positive rainfall anomalies occur in much of the region during March-May (MAM) and October-December (OND) of the ENSO(0) years and negative anomalies dominate during the following ENSO(+1) years. These rainfall patterns are useful for short-term climate monitoring over the region. The relationship between the Quasi-Biennial Oscillation (QBO) in the lower stratospheric zonal winds and the long-rains of MAM is more significant in lagged than in simultaneous, with the most distinct relationships occurring over the western parts of the region. The QBO-index explains about 36% of the seasonal rainfall variance. There is a 60/63 percent likelihood for the occurrence of above/below normal rainfall during the westerly/easterly phase of the QBO-index. The NCAR Regional Climate Model (RegCM2) simulations have demonstrated the added value of the nesting approach in improving regional climate simulations. The model reproduces the observed characteristics of the Turkana low-level jet. The study has shown the importance of orographic forcing, the large-scale background monsoon flow and depth of the channel in the development and maintenance of the jet. Thermal and frictional forcing play equivalent roles as that of the large-scale winds in the formation of the jet. The identified regions of strong winds associated with the jet are important to the safety in the aviation industry and are also potential for alternative renewable energy resources in the form of wind energy. Large-scale orography is the most important factor. Divergence and anticyclonic vorticity partly explains the observed split in the jet cores. The dynamics of the flow in the channel and the dry conditions observed over the wider part of the valley is in partly explained by the Bernoulli theorem as applied to barotropic steady and non-viscous flows. Air-sea interaction phenomenon over the Indian Ocean, and the latitudinal location and intensity of the large-scale Walker and Hadley circulations are the main physical mechanisms responsible for the climate variability over the region during the wet and dry years. Abundant rainfall is associated with the presence of a midtropospheric cyclonic wind shear across the equator, and a negative vertical wind shear. Likewise, dry conditions are associated with the presence a strong westerly/southerly wind anomaly that occurs throughout the troposphere. Short-term climate prediction models developed in this study are capable of skillfully reproducing the space-time evolutions and distribution of the seasonal rainfall over the region, and specifically the observed floods that occurred during the 1997 ENSO year. Preliminary application of the RegCM2 in the prognostic mode successfully produces a 3-months projection of the extreme seasonal anomalies associated with the 1997 ENSO event. These models can be exploited further in operational short-term climate prediction over equatorial eastern Africa.

Abstract:

Patterns in polychaete abundance, body size and diversity were investigated at 12 sites between 4300 and 5000 m in the central Pacific and the north-east Atlantic. In the central Pacific, three of the sites (EqPac 0N, 2N and 5N) were observed to lie under high surface productivity regimes, and they were known to receive significant accumulations of food-rich phytodetrital material. The EqPac 9N, HOT 23N, DOMES A, ECHO 1 and PRA sites, which did not receive phytodetritus, were used as control sites with which to investigate the effect of this phytodetrital input. In the north Atlantic, one of the sites (PAP) was known to receive phytodetrital input, and one of the sites (MAP) had been subjected to a large-scale natural disturbance in the form of a turbidite emplacement. All specimens were identified to species level. Two families, the Pilargidae and Cirratulidae were selected for a more detailed alpha taxonomy assessment. New characters were developed for the identification of cirratulid thoracic fragments. Benthic polychaete abundance was correlated with surface productivity in both the Pacific and Atlantic Oceans. There was some evidence to suggest that there was a stronger benthic-pelagic link in the Pacific Ocean, where small changes in surface productivity generated larger changes in abundance than in the Atlantic Ocean. When data from previous studies are included, it is suggested that at levels of surface productivity above 200 gCm'2yr4, there is an upper limit to benthic polychaete abundance. Significant differences in body size between sites were found at species level, family level and for the entire polychaete taxon. At a species level, several abundant cosmopolitan deposit feeding species showed reduced body size in the food-rich phytodetrital sites. The only species to show increased body size in the food-rich sites were two predatory species. Polychaetes in the Atlantic Ocean responded more strongly in terms of body size reduction in phytodetrital sites than they did in the EqPac sites. Three hypotheses were put forward to explain these patterns: increased metabolic efficiency of large organisms in food-poor regions, seasonal recruitment pulses at phytodetrital sites and increased competition at phytodetrital sites. The former was favoured as the most likely explanation. Species diversity was shown to be highest in the phytodetrital sites in the central Pacific. It was hypothesised that this was the result of increased productivity, increased spatio-temporal heterogeneity and increased sediment heterogeneity at these sites. An increase in species diversity at phytodetrital Atlantic sites was not observed. The differences between north Atlantic and central Pacific sites were attributed to regional enrichment of local diversity in the Pacific. At the MAP turbidite site, alpha diversity was significantly lower than at other sites, and dominance was high, indicating the potential for large-scale natural disturbance in the abyss. A new spatio-temporal scale of disturbance was highlighted that may have evolutionary as well as ecological significance. Although levels of alpha diversity were generally shown to be high in the abyss compared to shallow water, the evidence did not suggest in favour of high beta diversity on scales of 1000 to 3000 km in either the central Pacific or north Atlantic. The low levels of beta diversity observed suggest that total species richness in the deep sea may not be as high as previously hypothesised, and that regional processes are likely to significantly impact local ecology in the deep-sea.

Abstract:

Includes bibliographical references (leaves 132-141).
Pierre Florenchie
This study is framed by three questions: firstly, could the Regional Oceanic Modelling System (ROMS) reproduce the seasonal cycle of the equatorial Atlantic? Secondly, what is the nature of the link between remote forcing in the western equatorial Atlantic and Benguela Niños/Niñas? Thirdly, what is the impact of these events on the equatorial Atlantic Ocean SST and circulation patterns? The results obtained suggest that the model is very sensitive to different wind stress forcing, particularly in respect of the impact on the mixed layer characteristics. As a result the equatorial upwelling is overestimated in both temporal and spatial scales.

Abstract:

The estimation of annual potential new production at a regional scale for the decade of the 1980s provides the main focus of this thesis. New production is the proportion of total primary production which relies on the uptake of NO₃-N by the phytoplankton while potential new production assumes that all the NO₃-N available to primary producers is assimilated. The Redfield ratio between carbon and nitrogen in the marine environment was used to express rates of potential new production in terms of carbon. In order to arrive at annual estimates of potential new production it was necessary to progress from the event-scale to the annual scale. This was achieved by the adoption of two novel methods of approach. Event-scale estimates of potential new production were made by assessing the amount of NO₃-N present in the nominal euphotic zone as a result of upwelling. Remotely-sensed images of sea surface temperature (SST) coincident with or shortly after upwelling events were used in combination with a derived relationship between SST and NO₃-N concentrations integrated over the depth range of the productive surface layer in the southern Benguela region. In this way it was possible to overcome the main shortcoming of passive satellite imagery by quantifying a sub-surface variable. The event-scale estimates of potential new production were extrapolated to the annual-scale by taking into account the dynamics of the system. Sea level fluctuation at the coast preceding upwelling events was found to be related to the event-scale estimates of introduced NO₃-N and hence used as a proxy for upwelling. Using a ten year record of sea level, estimates of annual potential new production, spanning the period June to May inclusive, were made for the period 1980/81 to 1989/90. Bibliography: pages 92-108.

Abstract:

Thesis (Ph. D.in Physical Oceanography)--Naval Postgraduate School, September 2003.
Dissertation supervisor: Mary L. Batteen. Includes bibliographical references (p. 109-123). Also available online.

Abstract:

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Global climate models project a 21st century strengthening of the Pacific Equatorial Undercurrent (EUC). The consequent increase in topographic upwelling of cool waters onto equatorial coral reef islands would mitigate warming locally and modulate the intensity of coral bleaching. However, EUC water is potentially more acidic and richer in dissolved inorganic nutrients (DIN), both widely considered detrimental to coral reef health. My analysis of the Simple Ocean Data Assimilation product indicates that the EUC has indeed strengthened over the past 130 years. This result provides an historical baseline and dynamical reference for future intensification. Additionally, I reared corals in laboratory experiments, co-manipulating food, light and CO2 (acidity) to test the role of nutrition in coral response to elevate CO2 conditions. Heterotrophy yields larger corals but CO2 sensitivity is independent of feeding. Conversely, factors that enhance zooxanthellate photosynthesis (light and DIN) reduce CO2 sensitivity. Corals under higher light also store more lipid but these reserves are not utilized to maintain calcification under elevated CO2 My results suggest that while mitigation of CO2 effects on calcification is not linked to energetic reserve, EUC fueled increases in DIN and productivity could reduce effects of elevated CO2 on coral calcification.
by Elizabeth Joan Drenkard.
Ph. D.

Abstract:

During extreme weather conditions such as hurricanes and nor'easters, both the currents and wind waves generated by the atmospheric forces are important. Although they may act and dominate on different temporal and spatial scales, their interactions and combined effects are without doubt significant. In this dissertation, a major effort has been made to couple an unstructured grid circulation model SELFE (semi-implicit, Eulerian-Lagrangian finite element model) and the WWM II (Wind Wave model II). Moreover, this new coupled model system can be executed in a parallel computational environment. After the coupled model was successfully built, the model was verified with ideal test cases, either through comparisons with analytic solutions or with laboratory experiments. It was further validated by field-measured data during two hurricane events. The SELFE-WWM II model framework described above was used to participate in a SURA testbed project that was recently funded by the NOAA IOOS program. The purpose was to improve the storm surge and inundation modeling skill throughout the Gulf of Mexico as well as along the U.S. East Coast. The coupled tide, surge, and wind wave models in two and three dimensions were tested and compared systematically. Two well-known cases were investigated in detail. One was the event of Hurricane Ike of 2008 in the Gulf of Mexico and the other was the April Nor'easter of 2007 in the Gulf of Maine. For the Gulf of Mexico study, the key scientific issue is the origin of the forerunner. It has long been recognized that the forerunner plays an important role in generating large hurricane-induced storm surge in the Gulf of Mexico. The forerunner is a phenomenon whereby water level throughout the vast coastal region was elevated days before the hurricane makes landfall. The forerunner can contribute significantly to the total water level that results subsequently during the primary surge when the hurricane makes landfall. The 2008 Hurricane Ike, which devastated the Galveston Bay along the Texas Coast, is a good example: 1.4 m out of 4.5 m maximum surge was contributed by the forerunner in the Gulf of Mexico. The consensus from initial results of multiple models indicates that the forerunner occurred as a result of Ekman set-up along the broad Louisiana-Texas (LATEX) shelf by the shore-parallel wind field. By contrast, the primary surge was dominated by the low pressure and the maximum wind along a path perpendicular to the shore as the hurricane made landfall. It was found that the cross-shore Ekman set-up is highly sensitive to the bottom boundary layer (BBL) dynamics, especially to the drag coefficient. Given the fact that the Gulf of Mexico is known to be rich in fluid mud, and near-bed flows generally are very weak under fair-weather conditions, one plausible hypothesis is that, during the stormy condition, the suspended sediment-induced density stratification is likely to be ubiquitously present at the bottom boundary layer. A sediment-transport model and wave-current bottom boundary layer sub-model including the sediment-induced stratification effect were coupled to the unstructured grid circulation and wind wave model (SELFE-WWM II) for simulating the forerunner during Hurricane Ike. The model results demonstrate that the bottom boundary layer dynamics have a significant effect on the velocity veering as well as the Ekman set-up across the shelf. In the Gulf of Maine study, the high-resolution coupled SELFE-WWM II model was applied in the Scituate Harbor, a small, shallow coastal embayment, south of Boston. The key issue for the study was the recurring inundation related to the role played by wind waves during nor'easter events. With limited observation data in the Scituate, the model result from SELFE was compared with that from FVCOM. The major findings are summarized as follows: (1) wind waves generated by the nor'easter can profoundly affect the coastal current by increasing the magnitude and altering its direction, (2) while the mean water level inside the Harbor stays the same, the total transport across the harbor mouth increases when wind waves are included, and (3) the total inundation area, primarily in the northern and southern basins within the Harbor, does increase when wind waves are included. There is a question as to why the inclusion of the wind waves did not cause the mean water level to change inside the Harbor while the inundation area was increased. The plausible explanation is that this lack of impact could be that the Stokes transport was small and the increase of water level by the wave set-up was compensated by the expansion of the inundation area in the shallow region.

Abstract:

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Includes bibliographical references (leaves 178-180).
Analysis of vertical profiles of absolute horizontal velocity collected in January 1981, February 1982 and April 1982 in the central equatorial Pacific as part of the Pacific Equatorial Ocean Dynamics (PEQUOD) program, revealed two significant narrow band spectral peaks in the zonal velocity records, centered at vertical wavelengths of 560 and 350 stretched meters (sm). Both signals were present in all three cruises, but the 350 sm peak showed a more steady character in amplitude and a higher signal-to-noise ratio. In addition, its vertical scales corresponded to the scales of the conspicuous alternating flows generically called the equatorial deep jets in the past (the same terminology will be used here). Meridional velocity and vertical displacement spectra did not show any such energetic features. Energy in the 560 sm band roughly doubled between January 1981 and April 1982. Time lagged coherence results suggested upward phase propagation at time scales of about 4 years. East-west phase lines computed from zonally lagged coherences, tilted downward towards the west, implying westward phase propagation. Estimates of zonal wavelength (on the order of 10000 km) and period based on these coherence calculations, and the observed energy meridional structure at this vertical wavenumber band, seem consistent, within experimental errors, with the presence of a first meridional mode long Rossby wave packet, weakly modulated in the zonal direction. The equatorial deep jets, identified with the peak centered at 350 sm, are best defined as a finite narrow band process in vertical wavenumber (311-400 sm), accounting for only 20% of the total variance present in the broad band energetic background. At the jets wavenumber band, latitudinal energy scaling compared well with Kelvin wave theoretical values and a general tilt of phase lines downward towards the east yielded estimates of 10000-16000 km for the zonal wavelengths.
by Rui Vasques de Melo Ponte.
Ph.D.

Abstract:

Polar zooplankton and fish safeguard against the seasonality of food availability by using the summer months to build large reserves of lipids, which in turn are utilized to meet the metabolic demands of apex predators such as penguins, seals, and whales. A warming trend in the northern part of the western Antarctic Peninsula (WAP) has led to a decrease in perennial and summer sea ice, an increase in heat content over the shelf, and lower phytoplankton biomass, which could affect prey quality. We compared prey quality, including elemental (C, N) content and ratios, total, neutral, and polar lipid content, and energy densities, of known top-predator prey items (krill Euphaush1 superba, 17Jysanoessa macrura, and Euphausia crystallorophias; and fish Pleuragramma antarcticum, and Electrona antarctica) along the W AP latitudinal gradient in January of 2009-20 II as part of the Palmer Antarctica Long-Term Ecological Research study. E. antarctica had the highest prey quality in terms of total lipid content and energy density, followed by T. macrura and P. antarcticum, then E. c1ystallorophias and E. superba. For all species, variations in carbon and nitrogen content were best correlated with by the animals' neutral lipid content, in that animals with larger neutral lipid stores had significantly higher carbon and lower nitrogen content. Across all sexes and maturity stages, E. superba in the South had ca. 20% higher total lipid content than E. superba in the North. Total lipid content was also significantly higher in the South for E. crystallorophias, though this was largely due to the presence of larger individuals in the south combined with a significant positive relationship between length vs. weight-specific total lipid content for this species. For all prey species except T. macrura, there was a positive relationship between latitude or 0-120 m integrated Chi a vs. lipid content (neutral, polar, or total lipids), and a negative relationship between 0-120 m mean water temperature vs. lipid content. Trends opposite to those above found for T. macrura, suggest an optimal habitat for this species in the northern W AP which is characterized by warmer temperatures and lower Chi a. Patterns in Chi a were more important than upper water column temperature in explaining the observed latitudinal trends. If regional warming persists, the prey quality trends described for E. superba, combined with their regional abundance decline in the northern, coastal W AP could affect the ability of apex predators that rely on E. superba to meet their energetics demands.

Abstract:

The Canadian Regional Climate Model (CRCM) has been used to investigate the effects of Gulf of Mexico sea surface temperature (SST) anomalies on the regional climate. Three sets of experiments have been performed, each consisting of a control run and with two different imposed Gulf SST anomalies. The first is a uniform increase or decrease of the SST by 5K over the entire Gulf. The second and third experiments use 5K SST anomalies of smaller extent, characteristic of warm core rings shed off the Loop Current in the Gulf. The experiments are carried out for either 15 or 30 days, and statistics are computed after discarding the first 5 days of the integration.
The response of the SST anomalies are qualitatively similar in the three cases, except the response to the anomaly over the entire Gulf is stronger due to the much larger extent of the anomaly. For a positive SST anomaly, precipitation and moisture over the Gulf and southeastern U.S. both increase. The 1000mb temperature field shows a clear warming over the Gulf and adjacent areas, delineating the imposed SST anomaly. A low level cyclonic circulation forms over the Gulf and southeastern U.S. region, while an anticyclonic circulation develops at the upper levels. The negative SST anomaly experiments show a qualitatively similar response, except it is of opposite sign with a smaller magnitude.

Abstract:

Water clarity is a key indicator of the ecosystem health in the Chesapeake Bay. Estuarine water clarity fluctuates due to external inputs from the watershed as well as processes occurring within the estuary itself, such as sediment resuspension and organic matter production. Therefore, water clarity requires study at multiple spatial and temporal scales and with multiple metrics. One local-scale process potentially influencing water clarity is shellfish aquaculture. One part of this dissertation examined how water quality and hydrodynamics varied among oyster farms as well as inside versus outside the extent of caged areas located in southern Chesapeake Bay. Current speed and water quality were measured within and adjacent to four oyster farms during two seasons. Results revealed minor effects of oyster farms on water quality, likely due to high background variability, relatively high flushing rates, relatively low oyster density, and small farm footprints. Minimal impacts overall suggest that low-density oyster farms located in adequately flushed areas are unlikely to negatively impact local water quality. At a larger spatial scale, another potential influence on water clarity is shoreline erosion. The second part of this dissertation examined the impact of shoreline erosion on water clarity via a numerical modeling study. Experiments were conducted to simulate realistic shoreline conditions representative of the early 2000s, increased shoreline erosion, and highly armored shorelines. Together, reduced shoreline erosion and the corresponding low seabed resuspension resulted in decreased concentrations of inorganic particles in surface waters, improving water clarity overall. However, clearer waters relaxed light limitation on phytoplankton, which often increased organic matter production, sometimes yielding opposite effects on water clarity according to different metrics. Clarity improved in mid-Bay central channel waters in terms of light attenuation depth, but simultaneously degraded in terms of Secchi depth because the resulting increase in organic matter decreased the water’s transparency. A final water clarity process considered was the long-term trend in water clarity from satellite remote sensing. The third part of this dissertation examined how remote sensing reflectance changed over time in Chesapeake Bay from 2002 to 2020 using the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on satellite Aqua. MODIS-Aqua remote sensing reflectance trends were evaluated from 2002 to 2020 at multiple wavelengths and spatial resolutions for surface waters of the Chesapeake Bay. Trends showed long-term decreasing reflectancein the upper estuary yet increasing reflectance in the lower estuary in the green wavelengths. Band ratios involving red-to-green and red-to-blue have decreased, suggesting improved water clarity, while green-to-blue ratios have increased over time, suggesting increasing contribution of phytoplankton to water cloudiness. Reflectance change over time relates well to observed decreases in total suspended solids and light attenuation, yet inconclusive trends in chlorophyll-a, suggesting a long-term change in particle properties such as size and composition that affect light scattering behavior.

Abstract:

The purpose of this essay is to investigate the origin of the large amount of precipitation that is present in the northern Ethiopian Highlands. With Moisture transport into the Ethiopian Highlands by Ellen Viste and Asgeir Sorteberg as a base, this essays intents to compare the same data but by focusing on a much smaller time scale. This frame was chosen to see if the data would deviate (i.e. a small and specific time scale versus a large and general time scale). Whilst the investigation by Viste and Sorteberg focuses on the two most rain rich months, July and August during 1998-2008, this essay focuses on only July during 2008. To investigate where the precipitation originates from, this essay has analyzed different meteorological parameters such as horizontal and vertical winds at different altitudes and the moisture content of these winds. This essay has like Viste’s and Sorteberg’s paper used ERA-Interim data as a basis. However the course of action has differed. This essay has made conclusions by visually drawing conclusions by studying the data images while Viste and Asgeir have drawn their conclusions by backtracking the wind to its origin. This investigations results showed that great amounts of moisture were transported into the highlands from the south-west, and to some extent also from the north. While the moisture transport from the south-west was large due to the level of moist in the air, these winds where fairly small and at low altitudes. The winds from the north were visible at higher altitudes and were stronger, however they carried much less water vapor. However, exactly how much each of these winds actually contributed to producing rain is more difficult to say. The results from Viste and Asgeir (2011) showed that the amount of moist that was transported into the highlands were about 46 percent more from the north compared to from the south. The contribution to moisture release within the area was however almost equally great from north and south. Both investigations thus showed that the largest amount of moist was transported from the south and north. What this study did however not address was how large amount of the entire moist that had contributed to rain. One anomaly of large amounts of precipitation was registered on the 20th of July 2008. This study looked closer into this which showed that large winds were registered this date as well as an upwind cell. One can presume that these winds carried large amounts of moisture, which previous results has shown, and that this might be an explanation to the large amount of precipitation that was measured on the 20th of July.

Abstract:

This paper will identify drinking water as a limited resource in a coastal community and recommend a Coastal Zone Management (CZM) protocol. It will include a global perspective and a United States (national) and County (regional) response to drinking water challenges. This perspective will include international comparisons of water as a decreasing global commodity and reflect security issues through a Threat and Risk Analysis, which will focus on biological contamination, accidental and terrorist initiated. The analysis will include a literature review and economic comparisons of municipal “tap” water costs vs. national and regional trends towards commercial bottled waters.This paper has five primary objectives. The first three are to define the sources of Broward County drinking water, provide usage by industry and municipalities and project future costs based on population growth, alternate sourcing and infrastructure costs to include protecting water sources and delivery systems. The fourth objective is to utilize a literature review to present the economic impact of the commercial bottled water industry, its effects on local water usage, projected costs, markets, and regional growth. The fifth objective considers a specific industry, Coca Cola, which is one of the largest receivers of Broward County drinking water.The conclusion includes a review of the impact of alternate water source costs incorporating security and threat assessment costs. Analysis compares Broward County municipal water prices with commercial bottled water consumer pricing via a survey format. The paper presents an economic based model of resource management, which includes recommendations for future strategies with which municipal authorities and professional water managers can maximize freshwater resource within a Coastal Zone Management paradigm.

Abstract:

A comprehensive hydrological study of large watersheds in Africa e.g. the Congo basin and the Nile basin has not been vigorously pursued for various reasons. One of the major reasons is the lack of adequate modeling tools that would not be very demanding in terms of input data needs and yet inclusive enough to cover such wide extents (over 3 million square kilometers for the Congo basin). Using a coupled run of the Community Atmospheric model (CAM3) and Community Land Model (CLM3) components of the Community Climate System of Models (CCSM), this study looks into the spatial and temporal variation of precipitation and river runoff in the Congo basin in the light of increasing trends in deforestation of the tropical forests. The effect of deforestation on precipitation and runoff is investigated by changing the land cover-type from the current configuration of broadleaf evergreen/deciduous, non-Artic grass and corn to a mostly grass type of vegetation. Discharge simulation for the river Congo is centered at the point of entrance to the Atlantic Ocean.Although the CLM3 does not presently simulate the observed river runoff to within at least one standard deviation it gives an opportunity to iteratively improve on the land surface parameterization with a possibility of future accurate prediction of mean monthly river runoffs under varying climate scenarios and land use practices. When forced with the National Center for Environment and Prediction (NCEP) re-analysis data the CLM3 runoff simulation results are relatively more stable and much closer to the observed. An improved CLM3 when coupled to CAM3 or other Global Climate Models is definitely a better tool for investigative studies on the regional hydrological cycle in comparison to the traditional methods. There was a slight reduction in rainfall in the first experiment which mimicked a severe form of deforestation and a slight increase in rainfall following low level of deforestation. These changes in rainfall were however statistically insignificant when compared to the control simulation. There was notable heterogeneity in the spatial distribution of the changes in rainfall following deforestation.

Abstract:

Dissertation (Ph.D. in Physical Oceanography) Naval Postgraduate School, September 1995.
Dissertation supervisor(s): Robert H. Bourke, Albert J. Semtner. "September 1995." Bibliography: p. 171-178. Also available online.

Abstract:

A Plataforma Continental Sul Brasileira (PCSB) é considerada uma importante região do litoral do Brasil, suas massas d’água e os processos dinâmicos apresentam um comportamento sazonal que imprime fortes efeitos no ecossistema costeiro. Com objetivo de caracterizar a Frente Subtropical de Plataforma (FSTP) e seu impacto na atmosfera, o presente trabalho utilizou o modelo acoplado oceano-atmosfera COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) para estudar, na região da PCSB, a distribuição das massas d’água e a variabilidade oceânica durante o ano de 2012. Assim como, o acoplamento oceano-atmosfera durante 10 dias do mês de junho de 2012, coincidentes com a realização do cruzeiro oceanográfico ACEx/SIMTECO. Os resultados de ambos os períodos de estudo foram comparados com observações históricas, com dados coletados in situ pelo cruzeiro ACEx/SIMTECO e com dados de satélite. Os resultados indicam que essa componente foi capaz de reproduzir as principais características termohalinas e a sazonalidade das águas que dominam a PCSB. A mistura entre as águas de plataforma subtropicais e subantárticas que ocorre na FSTP, apresentou uma clara mudança sazonal em seu volume. Como consequência da mistura e da oscilação sazonal de posição da FSTP, a estabilidade da coluna d´água dentro da PCSB também muda sazonalmente. Os valores de temperatura da superfície do mar (TSM) e altura da superfície do mar mostraram valores sazonais de REQM inferiores a 2°C e um skill médio superior a 0,75. Valores de velocidade sobre a plataforma para a Corrente Costeira do Brasil (CCB) chegam 0,6 (m.s-1), enquanto o transporte para a Corrente do Brasil (CB) e CCB foram de -7 a -44 Sv e -0,3 a 0,3 Sv, respectivamente. Os mapas sazonais de energia cinética média e energia cinética turbulenta representam o comportamento já conhecido da CB e ressaltam a importância do fluxo costeiro médio ao largo da costa da Argentina ao longo do ano. A comparação dos dados do modelo atmosférico, rodado no modo acoplado do COAWST, com dados observacionais indicam um satisfatório desempenho do modelo em representar as variáveis temperatura potencial, umidade relativa e específica, assim como os campos de vento na superfície do mar. O módulo atmosférico do COAWST foi também capaz de representar as variações da camada limite atmosférica marinha (CLAM), mesmo em condições sinóticas pré e pós-frontais como as observadas durante a realização do cruzeiro ACEx/SIMTECO. O presente trabalho apresenta, pela primeira vez para a região de estudo, resultados que demonstram a robustez do modelo regional COAWST em descrever o comportamento sinótico da atmosfera frente aos gradientes de TSM na região da PCSB. E oferece novos subsídios para o estudo do comportamento do sistema acoplado oceano-atmosfera nesta importante região da costa brasileira.
The South Brazilian Continental Shelf (SBCS) is considered an important region of Brazilian coast, their water masses and the dynamic processes present a seasonal behavior that has strong effects on the coastal ecosystem. In order to characterize the Subtropical Shelf Front (STSF) and its impact on the atmosphere, this work used the ocean-atmosphere coupled model COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) to study, in the SBCS region, the distribution of water massas and ocean variability during the year 2012. As well, the ocean-atmosphere coupling during 10 days of June 2012, coinciding with the ACEx/SIMTECO oceanographic cruise. The results of both study periods were compared with historical observations, data collected in situ by the ACEx/SIMTECO cruise and satellite data. The results indicate that this component was capable of reproducing the main thermohaline characteristics and the seasonality of dominant waters of the SBCS. The mixture between subtropical and subantarctic shelf waters that occurs in the STSF, showed a clear seasonal change in its volume. As consequence of mixing and seasonal STSF oscillation, the stability of the water column within the SBCS also changes seasonally. The values of sea surface temperature (SST) and sea surface height showed seasonal RMSE values below 2 °C and an average skill greater than 0,75. Velocity values on the shef for Brazilian Coastal Current (BCC) reach 0,6 (ms-1), while transport to Brazil Current (BC) and BCC were -7 to -44 Sv and -0, 3 to 0.3 Sv, respectively. The seasonal maps of medium kinetic energy and turbulent kinetic energy represent the behavior of the BC and highlight the importance of the average coastal flow off the coast of Argentina during the year. The comparison of data from the atmospheric model, run in coupled mode of COAWST, with observational data indicates a satisfactory performance of the model in representing the variables potential temperature, relative and specific humidity, as well as the wind fields at the surface of the sea. The atmospheric module of COAWST was able to represent the variations of marine atmospheric boundary layer (MABL), even in pré and post-frontal synoptic conditions such as those observed during the ACEx/SIMTECO cruise. The present work presents, for the first time in this region, results that demonstrate the robustness of the COAWST regional model in describing the synoptic behavior of the atmosphere in front of SST gradients in the SBCS region. And offers new subsidies for the study of the behavior of the ocean-atmosphere coupled system in this important region of the Brazilian coast.

Abstract:

This study aimed at describing the characteristics of daily precipitation and discharge extremes in the Adige river basin at the city of Trento. Annual maximum series for the period 1975−2014 were analyzed in terms of trends, seasonality indices and L-moments. A Mann-Kendall trend analysis showed a weak but significant signal of decreasing ex-tremes; the percentages of sites with significant negative trends were overall larger than the significance levels. Precipitation extremes were characterized primarily by autumn storms, while floods had a stronger seasonality with peaks occurring predominantly in June and July which indicated that the timing not solely explained by rainfall maxima. The Adige basin was found to be a hom*ogenous region with respect to precipitation, but the results did not support a corresponding assumption for discharge. A regional fre-quency analysis was performed for precipitation data and found both the Pearson type III and generalized normal distributions to be adequate regional frequency distributions. The extreme daily precipitation at Trento with a 100-year return period was estimated to be between 114 and 148 mm/d.
Egenskaperna hos extremvärden av dygnsnederbörd och -vattenföring i Adigeflodens av-rinningsområde vid staden Trento undersöktes. Serier med årsmaxima för perioden 1975–2014 analyserades med avseende på trender, säsongsindex och L-moment. Trendanalys med Mann-Kendallmetod antydde en svag men signifikant signal om minskande extrem-värden, då andelen mätstationer med signifikant negativa trender överlag var större än signifikansnivån. Den extrema nederbörden karakteriserades huvudsakligen av höststor-mar, medan vattenföringen hade en starkare säsongsbundenhet då maxima inträffade främst under juni och juli. Vattenföringens extremvärden kunde därmed inte enbart för-klaras av nederbördsmaxima. Avrinningsområdet kunde betraktas som en hom*ogen reg-ion för nederbörd, men resultaten gav inte stöd åt ett motsvarande antagande för vatten-föring. En regional frekvensanalys genomfördes för nederbördsdata och visade att Pear-son typ III och den generaliserade normalfördelningen var lämpliga regionala sannolik-hetsfördelningar. Över Trento uppskattades den extrema dygnsnederbörden med en åter-komstperiod på 100 år till mellan 114 och 148 mm/d.

Abstract:

Ocean tides worldwide have exhibited secular changes in the past century, simultaneous with a global secular rise in mean sea level (MSL). The combination of these two factors contributes to higher water levels, and may increase threats to coastal regions and populations over the next century. Equally as important as these long-term changes are the short-term fluctuations in sea levels and tidal properties. These fluctuations may interact to yield locally extreme water level events, especially when combined with storm surge. This study, presented in three parts, examines the relationships between tidal anomalies and MSL anomalies on yearly and monthly timescales, with a goal of diagnosing dynamical factors that may influence the long-term evolution of tides in the Pacific Ocean. Correlations between yearly averaged properties are denoted tidal anomaly trends (TATs), and will be used to explore interannual behavior. Correlations of monthly averaged properties are denoted seasonal tidal anomaly trends (STATs), and are used to examine seasonal behavior. Four tidal constituents are analyzed: the two largest semidiurnal (twice daily) constituents, M2 and S2, and the two largest diurnal (once daily) constituents, K1 and O1.

Part I surveys TATs and STATs at 153 Pacific Ocean tide gauges, and discusses regional patterns within the entire Pacific Ocean. TATs with statistically significant relations between MSL and amplitudes (A-TATs) are seen at 89% of all gauges; 92 gauges for M2, 66 for S2, 82 for K1, and 59 for O1. TATs with statistically significant relations between tidal phase (the relative timing of high water of the tide) and MSL (P-TATs) are observed at 55 gauges for M2, 47 for S2, 42 for K1, and 61 for O1. Significant seasonal variations (STATs) are observed at about a third of all gauges, with the largest concentration in Southeast Asia. The effect of combined A-TATs was also considered. At selected stations, observed tidal sensitivity with MSL was extrapolated forward in time to the predicted sea level in 2100. Results suggest that stations with large positive combined A-TATs produce total water levels that are greater than those predicted by an increase in MSL alone, increasing the chances of high-water events.

Part II examines the mechanisms behind the yearly (TAT) variability in the Western Tropical Pacific Ocean. Significant amplitude TATs are found at more than half of 26 gauges for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). For the lesser constituents analyzed (O1 and S2), significant trends are observed at ten gauges.

Part III analyzes the seasonal behavior of tides (STATs) at twenty tide gauges in the Southeast Asian waters, which exhibit variation by 10 – 30% of mean tidal amplitudes. A barotropic ocean tide model that considers the seasonal effects of MSL, stratification, and geostrophic and Ekman velocity is used to explain the observed seasonal variability in tides due to variations in monsoon-influenced climate forcing, with successful results at about half of all gauges. The observed changes in tides are best explained by the influence of non-tidal velocities (geostrophic and Ekman), though the effect of changing stratification is also an important secondary causative mechanism.

From the results of these surveys and investigations, it is concluded that short-term fluctuations in MSL and tidal properties at multiple time scales may be as important in determining the state of future water levels as the long-term trends. Global explanations for the observed tidal behavior have not been found in this study; however, significant regional explanations are found at the yearly time scale in the Solomon Sea, and at the seasonal time scale in Southeast Asia. It is likely that tidal sensitivity to annual and seasonal variations in MSL at other locations also are driven by locally specific processes, rather than factors with basin-wide coherence. (Abstract shortened by ProQuest.)

Abstract:

Vatten är vår viktigaste naturresurs och sedan EU:s ramdirektiv för vatten trädde i kraft år 2000 har vattenfrågor fått allt större uppmärksamhet. Likväl tas rent dricksvatten lätt för givet och skydd av vattenresurser prioriteras sällan i samhällsplaneringen. Det behöver därför finnas en samordnad och långsiktig planering för de vattenresurser som används eller i framtiden kan komma att användas för dricksvattenförsörjning. Genom en vattenförsörjningsplan kan dessa vattenresurser i större utsträckning synliggöras och prioriteras. Syftet med detta arbete är att utreda vilka aspekter som bör beaktas och vilka strategier som är verkningsfulla för att ta fram och implementera regionala vattenförsörjningsplaner. I arbetet har en sammanställning av befintliga regionala vattenförsörjningsplaner gjorts och ett antal intervjuer genomförts. En vattenförsörjningsplan bör dels beskriva vilka vattenresurser som finns, men också hur det nuvarande och framtida vattenbehovet ser ut. Vattenbehovet bör sedan ligga till grund för vilka vattenresurser som ska betraktas som viktigast för vattenförsörjningen. För att ge en rättvisande bild av vattenbehovet behöver hänsyn tas till bland annat bristområden och hur behovet varierar över tid. En viktig faktor för att en regional vattenförsörjningsplan ska implementeras effektivt också på lokal nivå är att det finns en bred förankring. Länsstyrelsen och kommunerna bör tillsammans lägga grunden för arbetet och även andra aktörer bör vara delaktiga. Det behöver också finnas ett politiskt stöd. Detta arbete visar att det hos både länsstyrelser och kommuner finns en vilja att arbeta strategiskt med sin vattenförsörjning. Resursbrist, bristande kommunikation, samordningssvårigheter och otydliga riktlinjer kan emellertid försvåra eller fördröja arbetet. Förhoppningen är att denna rapport ska kunna bidra med viss vägledning i arbetet med att ta fram, implementera och följa upp regionala vattenförsörjningsplaner.

Abstract:

California is headed into its fifth consecutive year of drought, and climate change is expected to bring more frequent and severe droughts to the state. The state’s water supply is susceptible to drought as seen from the effects of the current dry period. Besides the clear impacts of drought, there are less obvious environmental, economic, and social costs, such as land subsidence from groundwater overdraft, and the consequences of urban tree and green space loss. As a uniquely climate-independent source, desalinated water can stabilize California’s water supply and lessen some of these drought-related impacts. Although seawater desalination is touted as the most costly and energy-intensive method for augmenting water supply, if implemented in a feasible manner, the technology provides a range of positive benefits for drought-prone California in the long term.This thesis analyzes the economic and environmental costs of using desalination to mitigate the effects of drought in California. The thesis explores both Australian and Californian desalination facilities as case studies for evaluating the benefits and impacts of using different methods of desalination, in an effort to determine which method would be the most beneficial for securing California’s water supply. It concludes that lower-capacity, flexible desalination facilities would be useful along California’s coast, under some conditions. By generating a supply of desalinated water for coastal communities, more water from the state and federal water projects could be redirected to agricultural regions and inland communities that suffer the most from dry spells, and thereby lessen a number of drought-related environmental, economic, and social consequences.

Abstract:

The Cal Poly Pier (Pier) Master/Facility Plan (FP) document provides the vision of the future for the Pier, a marine science research facility. The Plan facilitates project development and management of the Pier while meeting university and department research goals. Specifically, the FP document establishes goals and strategies to direct long-term development of the Pier, streamlines agency approval and permit requirements, provides context for pier management, and assists the permitting process for future development as it relates to regulatory permits and programmatic growth on the Cal Poly Pier to help meet goals of the Center for Coastal Marine Sciences (CCMS). The Cal Poly Pier is the marine field station for the California Polytechnic State University San Luis Obispo (Cal Poly) CCMS and is one of several facilities that supports research and educational activities. The CCMS is a CSU Campus Center research organization that provides research and education activities as a part of Cal Poly’s overall mission while offering opportunities to interested parties beyond Cal Poly, such as private and public entities. The 3,057-foot long pier provides students, faculty, researchers, and other users unrivaled access to the marine environment of the Central Coast and fosters hands-on learning opportunities to progress marine research and science. The Master Plan name was changed to Facility Plan to streamline the plan approval process and to minimize the potential for errors.

Abstract:

La libre circulation en zone CEMAC est un long processus en Afrique centrale qui date de cinq décennies. Les pays membres de cette organisation sont toujours en tractation et font face à d'interminables signatures et accords y afférents. Son manque d'effectivité empêche les citoyens tels les Camerounais de migrer dans la sous-région, en l'occurrence vers le Gabon et la Guinée Equatoriale, très réticents à l'ouverture de leurs frontières aux ressortissants de la CEMAC. Ceux-ci justifient leur posture par une situation socioéconomique qu'ils entendent préserver. Le contexte limitatif rend pertinent le développement de stratégies de mobilité pour les acteurs migrants concernés. Des politiques migratoires contraignantes amènent ainsi les migrants venant du Cameroun à concentrer leur présence à la frontière commune à ces trois pays : Kyé-Ossi. Au fil du temps, cette localité de halte prolongée des migrants a connu une expansion spatiale rythmée par une croissance démographique issue principalement de la migration intérieure ; ce phénomène soutenu par le commerce développe et anime la coopération transfrontalière dans cette partie du monde. Du processus d'intégration fortement ralenti, on assiste ainsi à une dynamique frontalière grâce à l'anthropisation des migrants et aux actions étatiques de territorialisation qui accroissent davantage les mouvements humains vers cette frontière. A partir de Kyé-Ossi vont se développer de nouvelles expériences de migration et de mobilité. Grace à la dynamique familiale et de réseaux créée autour de la frontière, Kyé-Ossi devient une nouvelle base pour des mobilités internationales variées : courtes et longues durées vers le Gabon ou la Guinée Equatoriale, réseau pour l'immigration, zone de transit de longue durée pour une immigration ultérieure, réseau de passage et de chaine d'acteurs marchands pour d'autres camerounais à l'intérieur de ces pays. Les trois frontières se retrouvent ainsi habitées par les camerounais, lieux de vie où on observe une différenciation dans leur expression de citoyenneté en tant que Camerounais et ressortissants de la sous-région CEMAC. La démarche adoptée pour mener cette recherche mobilise un corpus méthodologique s'appuyant sur un travail de terrain initié depuis 2014. Il intègre à la fois des observations directes en contexte d'immersion, des administrations de questionnaires et entretiens auprès de cibles diverses. S'y ajoute un travail d'exploitation de supports écrits tels que les documents scientifiques, administratifs et médiatiques, ainsi que des images satellitaires. Les matériaux obtenus permettent d'interroger et d'apprécier les liens mobilités – dynamique sociospatiale dans un cadre pluri-frontalier – intégration sous-régionale. Elle vérifie l'hypothèse d'ouverture des frontières aux mobilités internationales du fait de la continuité territoriale produite par la dynamique frontalière et mobilitaire
Free movement of people in the CEMAC zone has been a long process in the Central Africa subregion for the last five decades. The member States of that organization are still negotiating, then facing endless agreements about free movement. Its lack of effectiveness hinders sub-regional citizens like Cameroonians to migrate within the sub-region, especially to Gabon and Equatorial Guinea. These countries are very reluctant to open their borders to CEMAC nationals, because of their higher socio-economic situation they are protecting. That obstacle induces actors to develop their own mobility strategies. In fact, rejection at the border causes Cameroonian migrants to settle in Kyé-Ossi, a Cameroonian town that borders those two countries. Over time, that settlement gradually led to spatial expansion enhanced by the demographic growth resulting mainly from internal migrations; this phenomenon poked up by trade expands and enlivens border cooperation in that region. With a stagnant integration process, we thus witness a frontier transformation through anthropization by migrants and territorialization of state, actions which further increase human movements to that border. So from Kyé-Ossi will be formed the new migratory and mobility lives. Due to the family and network dynamics created around the border, Kyé-Ossi thereby becomes a new turning point for different international mobilities: short and long journeys towards Gabon or Equatorial Guinea, network for immigration, long-term transit zone for a subsequent immigration in both countries, network of passing and actors system of trade for other Cameroonians inside these countries. Then the three border fronts tamed or inhabited by Cameroonians, living places where they undergo differentiation in their citizenship as Cameroonians and nationals of the CEMAC sub-region. The methodology adopted to carry out this research includes a corpus based on fieldwork conducted since 2014. Data-gathering integrates direct observations in ethnographic context, sample survey and interviews with various target informants. Has been added to the previous methods exploitation of written materials such as literary, administrative and media documents, as well as satellite images. The collected data allows us to question and appreciate the links among mobility - socio-spatial dynamics in a multi-frontier context – sub-regional integration. This aims to verify the hypothesis of border openness to international mobility due to land continuity resulting from the border and migratory dynamics

Abstract:

Thesis (Ph. D.)--Massachusetts Institute of Technology, 1988.
Supervised by Mark Cane and Philip Richardson. "January 1988." Funding provided by the National Science Foundation, grant numbers OCE 82-08744, and OCE 85-14885. Includes bibliographical references (p. 339-351).

Abstract:

Uranium and thorium isotopes are powerful and sensitive tracers of a wide range of oceanographic and environmental processes. This thesis makes use of these isotopes in deep sea sediments to reconstruct dust fluxes and deep ocean respired carbon storage over the last 350 kyr in the central equatorial Pacific. The paleoenvironmental information obtained through the application of these isotopes as proxies reveals important information about the Earth’s ocean and atmosphere, and their connectivity on millennial and glacial-interglacial timescales. In Chapter 1 of this thesis I introduce the proxies and principals employed in our paleoenvironmental reconstructions. Subsequently, the first section of this thesis explores the use of 230Thxs,0-derived 232Th fluxes as a proxy for aeolian dust deposition at three sites beneath the shifting Pacific Intertropical Convergence Zone (ITCZ). The new records presented here improve upon existing records of tropical Pacific dust fluxes by increasing the temporal resolution ~5 fold and adding almost an order of magnitude more data. Specifically, we reconstruct dust fluxes in two cores from 0-150 ka and from one core from 0-350 ka In addition to substantially improving constraints on tropical dust fluxes this work also utilizes the spatial transect of cores to infer past positions of the ITCZ on glacial-interglacial and millennial timescales. This proxy approach to reconstruct ITCZ position has only been applied and published once previously, in a relatively low-resolution study. Chapter 2, entitled “Large deglacial shifts of the Pacific Intertropical Convergence Zone,” presents evidence that the Pacific ITCZ experienced large shifts in latitudinal position, on millennial timescales during the penultimate deglaciation. The data resolve abrupt shifts in atmospheric circulation associated with deglaciation, in this case Termination II, at the boundary between the full glacial marine isotope stage (MIS) 6 and the peak interglacial MIS 5. These shifts are significant in that they appear to have occurred at the same time as changes in the North Atlantic driven by Heinrich Stadial 11 and may have played an important role in pushing the climate system over the threshold for deglaciation. Indeed, this study is the first to show evidence of a millennial-scale ITCZ response at the time of the Heinrich Event 11 catastrophic iceberg discharge event. Additionally, the data point to the existence of a previously unidentified millennial peak in northern hemisphere dust abundance during the penultimate deglaciation. In Chapter 3, “Climate-related response of dust flux to the central equatorial Pacific over the past 150 kyr,” records of dust flux are used to provide strong evidence for an association between high latitude stadial events and tropical dust fluxes during the last 150 kyr. These high-resolution observations permit the drawing of conclusions about the meridional location of the Pacific ITCZ during six Greenland stadials. As with the shift of the ITCZ during Heinrich Stadial 11, these events were associated with perturbations of the interhemispheric thermal gradient and coincident movement of the ITCZ presents an important constraint on the sensitivity of the tropical atmosphere to high latitude perturbations. The conclusions stemming from the interpretation of geochemical and paleoceanographic data presented in Chapters 2 and 3 are of broad relevance to a variety of geoscience disciplines that seek an understanding of the climate system. For example, these results confirm predictions made by modeling studies about the response of the ITCZ to high latitude climate forcing and provide an important new set of boundary conditions for modeling studies aimed at reconstructing changes in insolation forcing and tropical hydroclimate. The results show that paleo-reconstructions can constrain the magnitude of even abrupt ITCZ movement, demonstrating the potential to relate ITCZ changes to the magnitude of thermal forcing and to investigate thermal and hydrological components of other climate change events, past and future. Additionally, these results help improve understanding of the relationship between atmospheric dust abundance and climate, with implications for planetary albedo and micronutrient fertilization of the oceans. The second portion of this thesis focuses on using authigenic uranium (aU) to reconstruct deep water chemistry with implications for paleocirculation. Chapter 4, “Repeated storage of respired carbon in the equatorial Pacific Ocean over the last three glacial cycles,” presents evidence that the Pacific was a significant reservoir for respired carbon during glacial periods over at least the last 350 kyr. This reconstruction is based on the precipitation of the redox sensitive metal uranium as a proxy for deep water oxygen concentrations. Because any change in oceanic storage of respiratory carbon must be accompanied by corresponding changes in dissolved oxygen concentrations, data reflecting bottom water oxygenation are of value in addressing questions of glacial carbon sequestration. The record reveals periods of deep ocean aU deposition during each of the last three glacial maxima. Export productivity data indicate these intervals are not associated with local productivity increases, indicating episodic precipitation of aU occurs in response to basin-wide decreases in deep water oxygen concentrations. Not only does the aU record show the history of dissolved oxygen concentrations in the central equatorial Pacific, it also provides an opportunity for the reconciliation of records previously interpreted as incompatible with one another and with the storage of respired carbon. Synthesis of existing data suggests the existence of a ’floating’ pool of respired carbon between 2 and 3.5 km depth in the equatorial Pacific. This hypothesis permits the interpretation of existing proxy data reflecting abyssal LGM circulation and carbon storage without invoking a glacial watermass geometry significantly different from present. The new data and conclusions presented in Chapter 4 represent a significant advance in our understanding of where carbon was stored in the ocean during successive glacial periods. The perspective provided by the new aU time series is spatiotemporally unique and constitutes compelling evidence that hypotheses of marine carbon storage developed to explain the last glacial period are equally applicable to previous Pleistocene glacial periods. The three studies presented in this thesis provide strong support for the utility of U and Th series isotopes in paleoenvironmental reconstructions. Not only does this work demonstrate the range of paleoclimatic proxy data that can be obtained from isotopes of U and Th, it also illustrates the value of interpretations derived from their analysis. The records presented here represent a substantial contribution to our knowledge of marine hydroclimate and ocean circulation over the last 350 kyr and motivate additional high resolution paleoclimate work using isotopes of U and Th.

Abstract:

The tectonic opening and closing of ocean gateways played a key role in global climate change during the Cenozoic. Although changes in these gateways affected ocean circulation and heat transport, many of their paleoceanographic effects are still unknown. This dissertation examines the tectonic constriction of the Indonesian Seaway through the middle to late Miocene (i.e., 13.6 to 5.6 Ma) by studying changes in foraminiferal populations and stable isotopes (δ13C and δ18O). The purpose is to better understand the development of the Western Pacific Warm Pool (WPWP) and its interaction with the East Asian monsoon. To study this gateway, three locations are considered: Ocean Drilling Program Site 806 (Ontong Java Plateau, located in the heart of the modern WPWP) and Ocean Drilling Program Sites 1143 and 1146 (southern and northern South China Sea, respectively). At ∼12.1 Ma, tectonic constriction of the Indonesian Seaway and a succession of sea level falls resulted in the cessation of trans-equatorial Pacific circulation and the initiation of a circulation pattern resembling the modern day. The constriction and sea level falls also resulted in the piling of waters in the western equatorial Pacific (WEP), forming a proto-warm pool. At Ontong Java Plateau the proto-warm pool established La Niña-like conditions, initiated the Equatorial Undercurrent and strengthened the Trade Winds, and sustained productivity in the eastern equatorial Pacific (EEP). The sea level falls also greatly restricted flows through the South China Sea and consequently initiated a proto-warm pool in this basin. After ∼9.8 Ma, rising sea level weakened the proto-warm pools as an El Niño-like state became established across the Pacific. The shoaling thermocline in the WEP initiated an interval of increased biological productivity while the EEP underwent a “carbonate crash”. The “biogenic bloom” in the WEP after ∼9 Ma was due to renewed Northern Component Water production and/or Himalaya-Tibetan Plateau uplift. The bloom was most pronounced after ∼8.5, coincident with plateau uplift and intensification of the Indian/East Asian monsoons. After 6.5 Ma, reestablishment of La Niña-like conditions produced a resurgent proto-warm pool in the WEP and a “biogenic bloom” in the EEP.

Abstract:

The release of the Commonwealth's Australia's Oceans Policy (AOP) in 1998, introducedthe concept of integrated ecosystem-based oceans management to be implemented throughRegional Marine Plans. The South-east Regional Marine Plan (SERMP) was the first plandeveloped under AOP. Fisheries, being the third largest industry in the south-east region,play a significant role in the implementation of the SERMP. This thesis identifiesimplementation issues for Australian fisheries in the broader context of regional marineplanning. Specifically, fisheries and oceans management arrangements are analysed for theircapacities to meet the objectives of AOP, in terms of integration and conflict managementthat crosses jurisdictions and sectors, and also within the fisheries sector.This thesis argues that effective implementation of the SERMP will require an advancedcapacity for integration between sectors and jurisdictions. It also argues that theimplementation of the SERMP will require more innovative and focused approaches toconflict management, so that traditionally opposing interest groups can work towardscohesive integrated oceans management. This thesis examines the development andimplementation of the SERMP, supported by comparative analysis of international initiativesand other approaches to natural resource management. This analysis demonstrates thatfisheries require a carefully planned combination of instrumental and institutionalarrangements to address issues raised in the SERMP. Likewise, oceans managementcurrently addresses integration issues at the higher echelons of government but lacks theoperational support to effectively implement the SERMP. This thesis proposes the use ofkey tools that incorporate instrumental and institutional bases for integrated management thatembody ecosystem-based management principles and effective conflict managementtechniques. Australia has traditionally adopted a "negative" integration approach to natural resourcemanagement, whereby activities should not be inconsistent with overall objectives formanagement. This thesis concludes that Australia needs to progress towards a more"positive" approach to integration in oceans management by breaking through traditionalsectoral and jurisdictional mindsets in order to practically meet ecosystem-based objectives.This requires a more concentrated effort to build the integrative capacity from within sectors,such as fisheries, to meet the overall objectives of AOP.

Abstract:

A presente tese apresenta uma compilação de estudos da circulação dasuperficie no oceano ao largo do sudoeste da Península Ibérica, através dacombinação de dados obtidos a partir de deteção remota, observações directase modelação numérica. Com base nestas observações, a região oceanogrãficaa sudoeste da Peninsula Ibérica aparece como um sistema complexo cuja circulaçãoã superfície é a resposta ã acção conjunta dum campo de vento espacial/temporalmente variãvel, ã interação da circulação costeira com o campode vorticidade ao largo constrangido pela existência de gradientes de pressãoao longo da costa, e as interações desta circulação com o escoamento subsuperficialsujeito ã batimetria do fundo. A tese tenciona descrever e discutira oceanografia regional descendo desde a larga escala até os processos demesoescala.Os processos de larga escala mostraram uma associação dos regimes deafloramento costeiro forçado pelo vento com o índice da Oscilação do AtlânticoNorte. A heterogeneidade espacial do campo de ventos oceânico apareceuassociada aos principais cabos, e foi proposta como principal responsávelpela geração de actividade de mesoscala. Uma parte importante desta tesebaseou-se na descrição e análise dos processos de mesoescala locais, com maiorênfase num dos fenómenos mais desconhecidos na oceanografia regional, comoé o filamento de afloramento do Cabo de São Vicente. Quer observaçõesdirectas do filamento, quer o seu estudo com um modelo numérico mostraramque o filamento aparece associado a um meandro do jacto de afloramentoinserido num campo povoado de vórtices persistentes com os quais mostrainteração.
The present dissertation presents a compilation of studies about the surfacecirculatíon off the southwestern Iberian Peninsula. These studies are based onremotely sensed data, in situ observations and numerical modelling outputs.Based on these, the oceanographic region appears as a complex system whosesurface circulatíon expresses the response to a spatially and temporally variablewind field, to the interaction of coastal circulatíon with the offshore eddyfield constrained by the existence of along-shore pressure gradients, all subjectedto the interaction with topographically-steered sub-surface flows. Thedissertation attempts to describe and discuss the regional oceanography downscalingfrom the large-scale down to the mesoscale processes.Large-scale processes evídenced an association with the prevailingwind-driven upwelling/downwelling regime, in close relation with the NorthAtlantic Oscillation index. The spatial heterogeneity of the wind fieldappeared related to the influence of the most outstanding capes. This wasproposed as a major responsible for the generation of mesoscale activity.An important part of this dissertation was devoted to the description andanalysis of local mesoscale processes. Special emphasis was put in theCape St. Vincent upwelling filament, which is one of the most intriguingphenomena for local oceanographers. Both direct obervations and the studywith a numerical model revealed that the filament occurs associated withmeanders of the upwelling jet embedded in a persistent eddy field, with whichinteracts.

Abstract:

Thesis (Ph. D.)--University of Wisconsin--Madison, 1986.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 344-365).

Abstract:

Effective conservationstrategies for sea turtles require knowledge of animal movements and protectionof biologically important habitats and life history stages. For breeding adultsea turtles, understanding both their inshore and pelagic spatial patterns isimperative to the successful protection of the species and the accurateidentification of their vulnerabilities. This study provides insight into the inter-nesting,post-nesting, and foraging movements of green sea turtles (Chelonia mydas) that nest on Bioko Island, Equatorial Guinea, byusing satellite telemetry to track green turtles (n=12) during two nestingseasons (2017-18, 2018-19), and as they migrated to foraging grounds after thenesting season. These tracks were fit with a switching state space model tocharacterize movements, and then analyzed in relation to environmental andanthropogenic factors. Dive depth data was also used to determine utilizationpatterns within the water column. The 12 tagged turtles migrated for an averageof 1064 km to two distinct foraging grounds, with 10 migrating west for anaverage of 1115 km to the coastal waters of Ghana, and 2 migrating south for anaverage of 1563 km to the coastal waters of Angola. Migrating turtles used bothdirect, pelagic migration strategies, and biphasal, coastal strategies, whichincluded intermittent foraging throughout migrations. Dive depths varieddepending on behavior, with an average of 19.3 m during inter-nesting, 12.6 mduring migration and 8.5 m during foraging. Knowledge of inter-nesting habitatuse, migration patterns, and foraging ground locations will be critical for thedevelopment of marine conservation management plans in the Gulf of Guinea andaide in sea turtle conservation efforts throughout the area. Additionally, spatialand dive depth data can inform zonal fishing regulators and provide informationneeded for modifications to fishing practices and gear that is most likely toreduce sea turtle bycatch. These data will provide a more completeunderstanding of marine areas critical to sea turtle conservation and aide insustainable economic development in the Gulf of Guinea.

Abstract:

Massive amounts of 13 C-depleted carbon rapidly entered the ocean more than once during the early Paleogene, providing a geological framework for understanding future perturbations in carbon cycling, including ocean acidification. To assess the number of events and their impact on deep-sea carbonate accumulation, I have studied carbonate ooze units of the upper Paleocene-lower Eocene, which were deposited on a subsiding flank of the East Pacific Rise (ODP Site 1215). From this record several proxies were used to ascertain changes in carbonate dissolution: carbonate content, foraminiferal test fragmentation, and planktic/benthic foraminiferal ratio. Based on these analyses, 1 observe that carbonate preservation generally increased from the late Paleocene (56 Ma) through the early Eocene (51.5 Ma), after which it became poor to negligible. This trend was punctuated by four short-term intervals characterized by carbonate dissolution and pronounced negative d 18 O and d 13 C excursions. It is inferred that these were anomalously warm periods (hyperthermals) caused by massive and relative fast 13 C-depleted carbon injections. These correspond to the PETM (∼55.5 Ma), H1/ETM-2 (∼53.7 Ma), I1 (∼53.2 Ma), and K/X (∼52.5 Ma) events. I also calculated carbonate, planktic, and benthic foraminiferal mass accumulation rates for the Site 1215. These were used to comprehensively examine the history of carbonate accumulation in the equatorial Pacific Ocean throughout the early Paleogene. I deduce that in the long-term (>10 5 yr) the lysocline and calcite compensation depth (CCD) generally deepened between 55.4 and 51.5 Ma; but rapidly (≤10 5 yr) shoaled and subsequently overcompensated during and after the four intervals of massive carbon injection. Planktic foraminiferal assemblages found in the record of Site 1215 follow a predicted pattern for selective dissolution. Species of Acarinina are preferentially preserved over Morozovella, which are preferentially preserved over Subbotina, Igorina and Globanomalina. A tiny and previously overlooked species, Praetenuitella antica n.sp, is formally described in this manuscript. This species is also resistant to dissolution. The findings of this study provide firm constraints to model the short and long-term carbon cycle dynamics during the early Paleogene

Abstract:

Today, ocean modeling is fast developing as a versatile tool for the study of earth’s climate, local marine ecosystems and coastal engineering applications. Though the field of ocean modeling began in the early 1950s along with the development of climate models and primitive computers,even today, the state-of-the-art ocean models have their own limitations. Many issues still remain such as the uncertainity in the parameterisation of essential processes that occur on spatial andtemporal scales smaller than that can be resolved in model calculations, atmospheric forcing of the ocean and the boundary and initial conditions.The advent of data assimilation into ocean modeling has heralded a new era in the field of ocean modeling and oceanic sciences. “Data assimilation” is a methodology in which observationsare used to improve the forecasting skill of operational meteorological models.The study in the present thesis mainly focuses on obtaining a four dimensional realization (the spatial description coupled with the time evolution) of the oceanic flow that is simultaneously consistent with the observational evidence and with the dynamical equations of motion and toprovide initial conditions for predictions of oceanic circulation and tracer distribution.A good implementation of data assimilation can be achieved with the availability of large number of good quality observations of the oceanic fields as both synoptic and in-situ data. With the technology in satellite oceanography and insitu measurements advancing by leaps over the past two decades, good synoptic and insitu observations of oceanic fields have been achieved. The current and expected explosion in remotely sensed and insitu measured oceanographic data is ushering a new age of ocean modeling and data assimilation. The thesis presents results of analysisof the impact of data assimilation in an ocean general circulation model of the North Indian Ocean.In this thesis we have studied the impact of assimilation of temperature and salinity profiles from Argo floats and Sea Surface height anomalies from satellite altimeters in a Sigma-coordinate Indian Ocean model. An ocean data assimilation system based on the Regional Ocean Modeling System (ROMS) for the Indian Ocean is used. This model is implemented, validated and appliedin a climatological simulation experiment to study the circulation in the Indian Ocean. The validated model is then used for the implementation of the data assimilation system for the Indian Ocean region. This dissertation presents the qualitative and quantitative comparisons of the modelsimulations with and without subsurface temperature and salinity profiles and sea surface height anamoly data assimilation for the Indian Ocean region. This is the first ever reported data assimilation studies of the Argo subsurface temperature and salinity profile data with ROMS in the IndianOcean region.