Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 48-53). / viii, 53 leaves, bound ill. (some col.) 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 72-79). / x, 79 leaves, bound ill. (some col.) 29 cm

Fifty fragments of young, fresh basalts from the Explorer Ridge, Paul Revere Ridge (Fracture Zone), Dellwood Knolls, and the J. Tuzo Wilson Knolls have been analysed for 12 major and minor elements, as well as 11 trace elements, by X-ray fluorescence spectrometry. Rare earth element concentrations in 25 of the samples have been determined by instrumental neutron activation, and Sr⁸⁷/Sr⁸⁶ ratios have been obtained for 11 of the basalts. The Explorer Ridge basalts have major element compositions similar to most mid-ocean ridge basalts (MORB), and can be classified as ferrobasalts, similar to those of the southern Juan de Fuca Ridge. The incompatible minor and trace elements K, Ti, Rb, Zr, and Nb are weakly to strongly enriched in the Explorer samples, with respect to MORB, part of which is the result of crystal fractionation. The observed trace element and light rare earth element (LREE) enrichment of many of the samples, particularly those from Explorer Deep, suggest that a weak hotspot may exist beneath the Explorer Deep. The adjacent ridge segments, Explorer Rift and the Southern Explorer Ridge, are erupting basalts both enriched and depleted in incompatible elements, which could be an indicator of a chemically heterogenous mantle source, or may be the result of intermittent injection of enriched magmas from the postulated hotspot beneath Explorer Deep into areas producing normal MORB. The enriched basalts do not have significantly different Sr⁸⁷/Sr⁸⁶ ratios from the depleted basalts. All the samples fall within the range of values typical for Juan de Fuca and Gorda Ridge basalts, and East Pacific Rise tholeiites in general. Thus, although the source areas for the 2 basalt types may differ chemically, they are similar radiogenically, unlike-other hypothetically plume-influenced areas such as the Mid-Atlantic Ridge at 45°N and the FAMOUS area. The basalts from the northwest and southeast Dellwood Knolls appear to be related by crystal fractionation, based on major element analysis. However, the very different REE patterns and Sr⁸⁷/Sr⁸⁶ ratios exhibited by the two knolls suggest that they have different mantle sources, one typically depleted (northwest knoll) and one chemically and radiogenically enriched (southeast knoll). In terms of their major and trace element chemistry, the J. Tuzo Wilson Knolls basalts are typical of late-stage volcanism on ocean islands associated with mantle plumes. The hawaiites strongly resemble alkali basalts dredged from several seamounts in the Pratt-Welker Chain, which are co-latitudinal with the J. Tuzo Wilson Knolls on a small circle about the Pacific-Hotspot pole of rotation. Geochronological evidence questions the hypothesis that the mantle plume responsible for Pratt-Welker volcanism is also the source for the J. Tuzo Wilson basalts. The existence of a second mantle plume, 300 km southeast of the first, would explain minor chemical and physiographical differences between the Knolls and the other Pratt-Welker seamounts, as well as the evidence for two phases of volcanism on the southeastern seamounts of the chain. A second plume also explains the coeval volcanism of Bowie Seamount and the J. Tuzo Wilson Knolls. Recent geophysical evidence suggests that the J. Tuzo Wilson Knolls are also part of the Explorer-Dellwood spreading system. Although the JTW basalts are plume-type basalts chemically, the situation appears to be somewhat analagous to other ridge segments where plumes are coincident with the ridge itself. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Deep-sea bamboo coral (Isidella sp.) SE000901A from the southern Oregon coast (water depth 1048m) provides a high-resolution record of variability of North Pacific Intermediate Water (NPIW) and carbon rain to the sea floor, related to coastal upwelling, from 1808 to 2000AD. Counting of annual layers in magnesium to calcium (Mg/Ca) variations, measured by electron microprobe analysis, yields a detailed age model that is transferred directly to records of carbon and oxygen isotope ratios (δ¹³C and δ¹⁸O) measured by isotope ratio mass spectrometry and trace element ratios measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). A significant linear relationship between δ¹³C and δ¹⁸O measured on the carbonate internode of the coral specimen revealed disequilibrium kinetic isotopic variations that depend on calcification rate. The stable isotopic time series are significantly correlated to cadmium to calcium ratios (Cd/Ca) in the carbonate internode, suggesting that cadmium uptake also reflects the rate of calcification. Comparison of phosphorus to calcium ratios (P/Ca) in the carbonate internode to historical records of oxygen concentrations of NPIW suggests that coralline P/Ca is related to the phosphate content of the ambient bottom water, which covaries inversely with oxygen concentration. Stable carbon and nitrogen isotopic ratios (δ¹³C and δ¹⁵N) were measured on two organic gorgonin nodes of our bamboo coral, but incomplete understanding of the gorgonin growth patterns and the difficulty in translating ages between the proteinaceous node and calcareous internode preclude detailed comparison between organic stable isotopes and the trace element and isotopic composition of the well-dated carbonate proxies. Based on correlation of the measured properties to historical variations in coastal upwelling, and high-latitude climate variability, we demonstrate the potential and challenges in using deep-sea bamboo corals to extend records of climate variability into the pre-historical past. / Graduation date: 2012

Understanding and modeling microbial responses and feedbacks to climate change is hampered by a lack of a framework in the pelagic environment by which to link local mechanism to large scale patterns. Where terrestrial ecology draws from landscape theory and practice to address issues of scale, the pelagic seascape concept is still in its infancy. We have applied the patch mosaic paradigm of landscape ecology to the study of the seasonal and interannual variability of the North Pacific to facilitate comparative analysis between pelagic ecosystems and provide spatiotemporal context for eulerian time-series studies. Using multivariate, 13-year climatologies of sea surface temperature, photosynthetically active radiation, and chlorophyll a derived from remote sensing observations, we classified hierarchical seascapes at monthly and interannual scales. These dynamic, objectively-determined seascapes offer improved hydrographic coherence relative to oceanic regions with subjectively defined and static boundaries (Chapter 2) and represent unique biogeochemical functioning (Chapter 2) and microbial communities (Chapter3). Furthermore they provide consilience between satellite studies and in situ observations (Chapter 4) and allow for objective comparison of ecosystem forcing (Chapters, 4 and 5). In Chapter 2, we rigorously tested the assumption that satellite-derived seascapes describe regions of biogeochemical coherence. The seasonal cycle of the North Pacific was characterized at three levels of spatiotemporal hierarchy and broader relevance of monthly ���resolved seascapes was assessed through analysis of variance (ANOVA) and multiple linear regression (MLR) analyses of nutrient, primary productivity, and pCO��� data. Distinct nutrient and primary productivity regimes were well-characterized in the coarsest two levels of hierarchy (ANOVA, R�� = 0.5-0.7). Finer scale partitioning was more relevant for pCO���. MLR analyses revealed differential forcing on pCO��� across seascapes and hierarchical levels and a 33 % reduction in mean model error with increased partitioning (from 18.5 ��atm to 12.0 ��atm pCO���). In Chapter 3 we verified the seascapes with in situ collections of microbial abundance and structure. Flow cytometry data was collected from two long term time series and several cruises spanning thousand kilometers of the NE Pacific; these data allowed us to quantify spatiotemporal patterns. In addition, multiple response permutation analysis revealed differences in community structure across discrete seascapes, in terms of both absolute and relative abundances. Principal component analysis of the assemblage supported seascape divisions and revealed structure along environmental gradients with strong associations with chlorophyll a and sea surface temperature and, to a lesser extent, with mixed layer depth and mean photosynthetically active radiation in the mixed layer. Differences of assemblage structure between seascapes and strength of environmental forcing were strong in the subarctic and transition zones, but less pronounced in the subtropics, suggesting satellite-detected changes in bulk properties that may be associated with local physiology or interannual shifts in seascape boundaries. Based on the work presented in Chapter 4, we discovered that interannual shifts in the boundaries of a transition seascape and two distinct oligotrophic subtropical seascapes affect the variability observed at benchmark time series Station ALOHA; the latter two seascapes oscillate in their contributions to the expansion of the entire subtropics. On interannual scales, in situ phytoplankton abundance (as measured by chl-a), net primary productivity (NPP), and the relative abundance of eukaryotic phytoplankton and Synechococcus sp. increased during periods of encroachment by the transition seascape. Conversely, the relative abundance of Prochlorococcus increased and chl ���a and NPP decreased when the highly oligotrophic seascape encroached on Station ALOHA. The dynamic range (~6 million km��) of subtropical expansion is born almost entirely by the transition zone - resulting in a transfer of ~1.2 Pg of total primary C production between a system primed for export production and one dominated by the microbial loop. In Chapter 5, we investigated multiple factors that contribute to the effectiveness of the biological pump in the transition seascape. Near-continuous measurements of net primary production (NPP), net community production (NCP) and several ecophysiological variables were collected in across subarctic, transition, and subtropical seascapes of the Northeast Pacific during August and September of 2008. Mesoscale processes and shifts in community structure contributed to high export efficiency in the subtropical seascape; the convergence of assemblage structure, high biomass, moderate NPP: NCP and high NCP contributed to biologically mediated air-sea exchange in the transition seascape. Furthermore, NPP and NCP were strongly spatially coupled in both the transition (r[subscript 1, 39]=0.70; p<0.0001) and subtropical seascapes (r[subscript 1, 45]= 0.68, p<0.0001), suggesting the possibility for empirical modeling efforts. This dissertation provides a first step to characterize the seascape variability in the NE Pacific and to understand the modulation of primary and export production in a critical transition region. The multivariate seascape approach described here provides spatiotemporal context for in situ studies and allows objective comparisons of systems' responses to climatic forcing. An integrated ocean observing system will require insight from in situ observations and experiments, ecosystem models, and satellite remote sensing. The results highlighted in this dissertation suggest that the pelagic seascape framework, through its capacity to scale both context and mechanism, may serve as an important and unifying component of such an observing system. / Graduation date: 2013

1-km MODIS observations of ship tracks off the west coast of the U.S. are used to characterize changes in cloud visible optical depths, cloud droplet radii, cloud cover fraction, and column cloud liquid water amount as low-level marine clouds respond to particle pollution from underlying ships. This study re-examines the finding of earlier studies based on Advanced Very High Resolution Radiometer (AVHRR) observations showing that when restricted to pixels overcast by low-level, single-layered cloud systems, the polluted clouds in the ship tracks had on average ~20% less liquid water than the nearby uncontaminated clouds. This study uses Moderate Imaging Spectroradiometer (MODIS) observations from the Terra and Aqua satellites and takes advantage of the 1.6 and 2.1-µm channels in addition to the 3.7-µm channel available on AVHRR to derive droplet effective radii. The additional channels allow for different and presumably more comprehensive analyses of the cloud properties. In addition, this study uses a retrieval scheme that accounts for the effects of partial cloudiness within the 1-km pixels on the retrieved cloud properties. An improved automated track finding scheme that allows for the selection of unpolluted clouds to be closer to the clouds identified as being polluted is also employed in this study. When restricted to overcast pixels, as was done in earlier studies, results from the Terra and Aqua MODIS observations indicate that cloud droplet effective radii are significantly smaller and cloud optical depths significantly larger for polluted pixels than for unpolluted pixels. Cloud top height does not change when clouds become polluted but cloud liquid water path decreases slightly but significantly. The decrease in cloud liquid water obtained with the MODIS observations was at most ~10%, much less than the 20% obtained with the AVHRR observations. This decrease, however, depended on the wavelength used to derive the droplet effective radii. Also, the clouds that were most sensitive to pollution were those with small optical depths and large droplet effective radii. / Graduation date: 2007

Approved for public release; distribution is unlimited. / The Tropical Cyclone Vorticity Tracking Program is used to identify vortices in the western North Pacific from the Navy Operational Global Atmospheric Prediction System (NOGAPS) analyses and forecasts during May- October 2002 and 2003. Based on the NOGAPS analyses, several parameters are different between the 23vortices that developed into storms during 2002 according to the Joint Typhoon Warning Center (JTWC) and the231 vortices that did not develop. After eliminating 127 vortices that did not persist at least 24 h, this left 104 nondevelopingcases. For the developing circulations, the average 850-mb relative vorticity value at the first JTWCwarningtime was 5.0 x 10-5 s-1, with an easterly deep layer wind shear of -1.8 m s-1. The average 850-mb relativevorticity maximum for the non-developing cases was 3.3 x 10-5 s-1, with a westerly vertical shear of 4.1 m s-1. TheNOGAPS model tends to over-forecast relative vorticity prior to formation time for both developers and nondevelopers.Especially for the 72-h and 96-h forecasts, the over-forecasting tendency leads to non-developingvortices meeting the threshold vorticity value of the developing vortices. The tendency for NOGAPS to forecastthe non-developing deep layer wind shear to become increasingly easterly with time is considered to be a majorfactor in these over-forecasts of formation. Some adjustments in the cumulus parameterization heating andmoistening plus convective momentum transport may improve these forecasts of tropical cyclone formation. / Captain, United States Air Force

Extratropical cyclones (ETCs) are a common feature of mid- and high-latitudes which, on a large scale, are a primary mechanism by which heat and moisture are transported from equator to pole. ETCs also exert a major impact at smaller scales. Communities along the western coast of Alaska face many types of impacts generated by the winds associated with ETCs, including storm surges, sea water intrusion into fresh water stores, and coastal erosion. Such “strong wind events”, which can occur independent of an ETC, can also generate hazardous sea states and associated impacts on shipping. With no roads, coastal Alaska relies heavily on marine and air transportation. Hazards posed to marine and air travel are often related to two main types of weather: wind and fog. Consultations with stakeholders in the marine transportation community have indicated more precisely specific aspects of poor weather, such as high wind events, that are problematic, including the idea that the periods between strong wind events, defined as lull periods, represent an important metric when planning travel between points of safe harbour. Three separate studies of storminess metrics in the North Pacific and Alaskan regions are presented. The first study presents both a comparison of two storm identification and tracking algorithms and an evaluation of the general characteristics of extratropical cyclones for the North Pacific as portrayed in two reanalyses. The second study applies a modified wind event identification algorithm to reanalysis data to evaluate the spatial climatological patterns of wind events in the circum-Arctic. The third study tests the statistical relationships and predictability of two measures of storm activity - cyclone track density (TDEN) and wind event frequency - in the North Pacific using teleconnection indices exhibiting local influence. The first study showed that the general patterns and trends of cyclone characteristics are similar between the two methods, though with increased values of cyclogenesis density, cyclolysis density, and track density when using the relative vorticity based method. A comparison between storm tracks for NCEP1 and the 56-member ensemble of the Twentieth Century Reanalysis v2 (20CR) shows distinct differences between the 20CR and NCEP1 mean climatology for main storminess indicators. The second study evaluated the spatial and temporal characteristics of wind events and introduced a novel indicator that characterizes periods of favorable weather between strong wind events that last 48-hours or longer, termed lull events. Lull periods were found to be an important consideration for northern marine operations – both economic and subsistence. Additionally, combinations of lull and wind event indicators, termed lull/storm winds (LSW), were analyzed and showed that preferred areas of wind events and lull events are not always spatially coherent. The third study tested the statistical relationships and predictability of two measures of storm activity - cyclone track density (TDEN) and wind event frequency - in the North Pacific using teleconnection indices with local influence for the winter period of 1950 - 2012. Two statistical modeling techniques are applied to evaluate linear and non-linear methods of prediction for the region. For both measures of storm activity, the North Pacific index, Niño 3.4 index, and the AO index were found to be the best predictors. Using a 23-year hindcast period (1980 – 2012), the region of highest wind event anomaly prediction skill is located in the western Bering Sea, with hindcast correlation values as high as +0.5 and root mean squared skill scores (RMSESS) 25% higher than climatology. Highest TDEN predictive skill from the 23-year hindcast is found in the southeast region of the North Pacific, near the California coastline, with correlation and RMSESS as high as +0.7 and 25 - 30%, respectively. / Graduate

Zhang, Wei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 184-203). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Graduation date: 1968