Graduation date: 1992

Three folded maps in pocket. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references. / Microfiche. / x, 173 leaves, bound ill. (some col.), maps 29 cm

Indiana University-Purdue University Indianapolis (IUPUI) / Drivers that influence oceanic productivity are not clearly constrained. However, sea level changes during glacial cycles have been proposed as a potential driver for productivity variations observed over warm and cold climate periods. In order to determine this, additional oceanic paleoproductivity data collection is necessary to estimate the ocean’s feedback in response to a dynamic climate. The eastern equatorial Pacific (EEP) is an ideal site for productivity studies due to its high levels of nutrients and deep upwelling. This research examines the phosphorous and barite geochemisty of four EEP sites while also comparing the sites’ glacial and interglacial productivity variations to the geochemistry and productivity results of an independent central equatorial pacific site. Phosphorus and other elemental data were collected from sites 845, 848, 849, and 853 (ODP Leg 138). Using a Ba/Ti and P/Ti proxy (“excess” proxies), distinct productivity variations during glacial and interglacial periods were observed. While the age model for these sites has been estimated, the observed variations more than likely agree with high productivity during glacial periods and lower productivity during interglacial periods. Central equatorial Pacific cores RR0603-03TC and RR0603-03JC (IODP site survey cruise for Proposal 626) have been used as a reference for geochemical concentration parameters, as well as a comparison tool for productivity variations among the central and eastern sites. The central equatorial geochemistry results provided support for sea level changes driving paleoproductivity variations. The similar variation patterns displayed by the EEP’s geochemical data in this research could provide additional support for this hypothesis.

In the equatorial Pacific Ocean, earthquakes are used as an indicator of tectonic stress for normal faults in the Galapagos Spreading Center, transform faults along the East Pacific Rise and thrust faults in the Middle American subduction zone. Linkages between seafloor tectonic processes and oceanographic and lunar conditions were explored using time-series cross-correlation analyses on two different time scales. Data for earthquakes in the eastern tropical Pacific study area are obtained using the hydrophone arrays of the NOAA-VENTS Program. Hydroacoustic monitoring (listening to underwater sounds) provides scientists with a detailed dataset that includes even small earthquakes, starting as low as magnitude 0.6, that are not perceived by land-based seismographs. Data for sea surface heights (SSH) consist of two different datasets. On a moon's quarter time scale, SSH data used to investigate the influence of the earth tide and changes in oceanic conditions were remotely acquired by the altimeter on board the TOPEX/Poseidon (T/P) satellite. SSH data used to investigate the influence of the ocean tides were obtained from the Tidal Model Driver (Padman and Erofeeva 2003), that predicts SSH for locations every hour. The Geographic Information System (GIS) was used for the visual display of the data and to compute basic descriptive statistics. A lab-book was created for the educational-outreach section of this work, explaining step by step how GIS has been used. Significant results show correlations between normal faults and ocean tides and between the thrust fault and earth tides. Also, the Quebrada and the Discovery transform faults show high correlation of earthquake events, suggesting that at such temporal and spatial resolution, the plate moves as a rigid block. / Graduation date: 2006

A main concern in fisheries science has been to identify an accurate index of fish abundance. An underlying paradigm in the science has been that the amount of effort (calculated in hours and standardized for boat size) spent fishing was the best variable to be used to account for the variation in catches. The use of the ratio, catch per unit of effort (cpue), assumes that variations in fish abundance are due to human-controlled processes above the ocean's surface. It does not account for variation due to oceanographic processes that affect fish behaviour and movement patterns below the ocean's surface. This study investigated the possibility that oceanographic factors such as temperature, salinity and depth could have effects on the variations observed in the apparent abundance of a demersal rockfish, Pacific Ocean Perch (Sebastes alutus. Gilbert). Simultaneous monitoring of physical variables and fish abundance estimation was achieved by attaching oceanographic equipment to the fishing gear of commercial vessels, monitoring the acoustic equipment and sampling the fish catch. It was found that Perch prefer a temperature range from 6.7 °C, down to at least 4.8 °C and that their movement patterns are linked to the movement of these temperatures by coastal wind patterns. Perch prefer areas with steep bathymetry, characterized by frontal activity due to interactions between the local bathymetry and tidal currents. Concerns that sampling only from highly successful commercial vessels may have biased abundance estimates, prompted the analysis of historical records of fish catch and government research surveys. Analyses between different boat sizes, different areas and different seasons from the original historical data base and a corrected subset revealed that it was mainly differences between areas that was responsible for the biasing of estimates. Deeper areas predictably produced more fish for all sizes of boats, but were fished more often by the larger boats used in the study. Therefore the field abundance estimates are likely to be biased towards areas of larger perch concentrations. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 79-80. / by Andrew G. Hudson. / M.S.

No description available.

The Cocos Gap is a deeper portion, or saddle, of the Cocos Ridge and forms part of the western boundary of the Panama Basing It is probably typical of saddles within most submarine ridges, In order to determine the mechanisms controlling sediment dispersal, the nature and sources of the sediments at 23 core locations were defined by hydrodynamic size separation (> 63, 2- 63, <2 micron) and microscopic or X-ray diffraction analysis of the individual fractions. In addition, calcium carbonate, organic carbon, opal and quartz determinations were made for the total sediment. The silt sized fraction was resolved into eight textural modes, The coarse modes reflect the progressive breakage and winnowing of the corase fraction (foraminifera) under the influence of bottom currents and gravity. Above 2000 m mechanical breakdown, winnowing and relocation by bottom currents mask the effects of depth related dissolution of the carbonate fraction, Intermediate modes in general represent a transitional facies with both biogenic and terrigenous influences, while the finest modes characterize a distal regime of clay deposition, The clay fraction is amorphous material with very low percentages of well crystallized clays. Three main sources and transport paths were recognized, including one associated with the circulation of the Panama Basin. Sedimentation within the Gap is controlled by local processes, predominantly the interaction between tidally induced intensification of bottom water flow and directional (thermohaline) flow. The steep' ness of the sea floor slope is a major factor controlling the efficiency of winnowing of the sediment away from certain higher elevations (biogenic source areas) to the sheltered parts and flanks of the ridge. Superimposed upon this sediment dispersal is the influx of terrigenous material carried by directional bottom currents that operate as postulated upper and lower contour currents along the flanks of the ridge. The crest of the Cocos Gap acts as a catchment area for the biogenic components, while the adjacent more sloping region, the sub-plateau, acts as a source area. The extreme breakage of the foraminifera is most likely a function of the tidally induced intensification of the bottom water flow, characteristic of many shallow ridges, and is probably most significant in the subplateau. Hydrographic data indicates that there is no significant transport of bottom water across the Cocos Gap into the Panama Basin, but downslope transport of carbonate and siliceous fragments and minerals from the Gap into the basin is associated with cyclical tidal bottom water flow. / Graduation date: 1976

Graduation date: 1969

Phosphate, silicate and nitrate concentrations in the sea off the coast of Oregon were determined to study their seasonal distribution patterns. The water samples were collected monthly along the east-west hydrographic line off Newport, Oregon, from the shore to 165 miles (310 km) offshore. The samples were analyzed by both a Technicon Autoanalyzer® and by manual methods. Phosphate in January was greater than 0.5μM at the surface, increasing to a 3.3μM maximum at 1000m. A phosphate maximum occurred at 1000m throughout the year. With the onset of photosynthetic activity, there was a general decrease in surface concentrations. Concentrations decrease to less than 0.1μM in October with surface concentrations increasing in November and December, reaching a maximum in January. Silicate concentration was approximately 170μM at 2600m during the entire year. In January, surface silicate increased from less than 5μM offshore to 13μM nearshore; a weak silicate minimum was observed at a depth of 60m offshore and at 5m near the coast. In March nearshore surface concentrations were greater than 15μM due to increased coastal river runoff; the silicate concentrations of Oregon coastal rivers were 150-250μM. In July, a pronounced minimum occurred at 40-50m depth, where the concentration was less than 2μM. Summer surface concentrations were less than 2M offshore, increasing to 40μM nearshore as a result of coastal upwelling. Surface concentrations in October were generally less than 5FIM along the Newport hydrographic line with increased near shore concentrations due to river runoff. The nitrate maximum of 40-45μM existed at 1000- 1200m. In January surface concentrations ranged from 3μM offshore to 6μM nearshore. March values were lower, ranging from 11μM offshore to 5μM nearshore at NH-3 (6 km). In July patches of nitrate-free water were observed at 40-50m depth offshore, disappearing at 25 miles (46 km) off the coast, at station NH-25, as a result of the influence of upwelled and nitrate containing water. Late in October, nitrate concentrations were higher, 5-6μM, near the coast, and dropping to less than 0.1μM offshore. Patches of nitrate-free water were found from May to November. The existence of nitrate-free water near the surface indicated that the feature was formed by the photosynthetic activities of phytoplankton. The formation of the silicate minimum and oxygen maximum below or near the bottom of the Columbia River Plume during summer months indicated intense photosynthetic activity. Neither preformed phosphate nor preformed nitrate changed with depth below the layers of active photosynthetic processes. Preformed phosphate was generally 1.0-1.2μM below 200m with variation occurring in surface waters. For surface values, 1.2μM, the highest of the year, was observed in July in upwelled water; 0.4μM, the lowest, also occurred in July within the influence of the Columbia River Plume. The vertical distribution of preformed nitrate seemed to be random and may have reflected analytical techniques. The range was between 5 and 10μM with a maximum at 12μM. The 5μM values were found at approximately 200m with a maximum observed at 1000m deep. The highest surface values of preformed nitrate, 2.0-5.0μM, were observed in January and the lowest, 1.0-1.5μM, in July. March and October values were between the above extremes (1.1-2.0μM). / Graduation date: 1970