The principal salinity extrema and extremum surfaces of the
world ocean are described by the analysis and plotting of data from
885 hydrographic stations in the three major oceans, the Southern
Ocean, and the American Mediterranean Sea. The distributions of
salinity, temperature, depth, and density along the extremum surfaces,
plotted...
This thesis involves the interpretation of gravity and other
potential field anomalies caused by layers of varying thickness. The
partial differential equations of potential field theory are reviewed for
gravitational and magnetic force fields. A similar review is carried
out for steady-state heat transport and diffusion processes. For the
gravitational...
Straight, radial, erosional channels and fan-like deposits of tephra develop around steep-sided cones and composite volcanoes, but are not characteristic features of shield volcanoes. The channels and deposits normally are formed by explosive volcanic density currents which originate as nuées adrentes or base surges. The physical processes of explosive volcanic...
Recent organic-rich deposits on the Peru continental margin
occur along the upper slope (100-450 m) between about ll°S and 16°S
and along the lower continental slope (>2000 m). The upper slope
deposits reflect high biological production in response to coastal
upwelling, but preservation of organic matter is enhanced by the...
The mesoscale sea-surface circulation pattern within 400 km off Chile and between 18°S and 40°S latitude is described using chlorophyll and temperature images from the Coastal Zone Color Scanner NIMBUS-7 satellite. The data base is a set of four mosaics developed from band-3 (550 nm) images taken on June 4...
The purpose of this thesis is to provide a first look at the spatial and temporal distributions of dissolved organic material (DOM) off the Oregon coast of North America. While this paper is not a comprehensive examination of these distributions, several patterns are identified as promising candidates for continued research....
Many phytoplankton and macroalgae release dissolved organic carbon (DOC). Many macroalgae also produce and store secondary metabolites which in some case have been shown to deter their grazers. The metabolites may be released into the surrounding seawater and could inhibit primary production. On the other hand, some phytoplankton can use...
By implementing a series of mass-conserving nested high-resolution models down to approximately 1 km resolution that have realistic bathymetry, coastline, wind forcing and river run-off, the winter 1996-1997 shelf flow near Cape Mendocino, California, is simulated and compared with available observations from the Strata Formation on Margins (STRATAFORM) marine geology...
This study was part of the Antarctic Environment and Southern Ocean Study (AESOPS) program, whose main goal was to investigate the role of the biota in the carbon flux from the atmosphere to the interior of the ocean. We quantified the abundance of the major phytoplankton classes and examined the...
The influence of nitrate availability and irradiance on phytoplankton natural fluorescence was investigated in laboratory cultures of the marine diatom Thalassiosira weissflogii (Bacillariophyceae). Two cultures of phytoplankton, differing only in the nitrate-limited growth rate, were compared to learn how increases in irradiance influences natural fluorescence. Instrumentation was developed for these...
The microbial diversity associated with sulfide structures from three
different hydrothermal vent fields was examined using phylogenetic analysis
based on the small subunit ribosomal RNA gene (16S rDNA). Samples were
collected from sites at 9°N, Guaymas Basin and the Juan de Fuca Ridge and
analyzed with denaturing gradient gel electrophoresis...
Suspended particulate matter (SPM) in the Columbia River is a mixture of particles of several origins having varying physical and biogeochemical properties. The relative abundances of these freshwater particles changes with season and apparently also with tide. Prior investigation has quantified seasonal variation of organic material in both the Columbia...
In the past, classification systems for the analysis of morphodynamic variability have been developed in an attempt to understand large scale coastal behavior. The motivation behind the creation of these classification systems has been to provide a framework of analysis, in order to understand large scale response to seasonal variability,...
Two separate research projects are described here. One involves
development of a new analytical method for determination of Ba in seawater and
other natural waters. The other is a collaborative field study of the chemistry of
Lake Issyk-Kul, Kyrgyzstan.
The method project explored an ion chromatography-fluorescence detection
bench-top approach for...
Using wave and wind data from nearby buoys and gauges, real time
kinematic global positioning system (RTK-GPS) and light detection and ranging
(lidar) topographic survey data, and a robust video record, we have quantified the
Large Scale Coastal Behavior (LSCB) of a dissipative end member beach in the
Pacific Northwest....
Eight years (1994-2000) of data from the TOPEX/Poseidon satellite altimeter
are used to investigate the variability of the sea surface height and geostrophic
velocity of the California Current system. The TOPEX/Posiedon satellite measures
SSH along an exact-repeat set of groundtracks with a 10-day repeat cycle.
In the domain studied here...
The optical properties of randomly oriented, spheroidal marine particles are modeled using both numerical and analytical techniques. The optical properties examined are attenuation, scattering, absorption and backscattering. The optical properties are compared to those of equal-volume spheres. The optical properties of very small particles, relative to the wavelength of the...
The mesoscale circulation in the Gulf of California is investigated using a numerical model (Princeton Ocean Model). Forced by satellite-derived winds, the circulation in the gulf shows a complex pattern dominated in the southern gulf by multiple eddies. Near the coast and in most of the north gulf, the circulation...
A year-long field study was undertaken to investigate the influence of a number of physical and biological factors, specifically temperature, organic carbon content, and shrimp population dynamics on sediment reworking rates by the ghost shrimp Neotrypaea calforniensis. Because of its role as a structuring agent in estuaries along the West...
The organic content of the Columbia River suspended particulate matter (SPM) results from the input of autochthonous (phytoplankton) and allochthonous (terrestrial vascular plants) production. The contribution of these two sources appears seasonal and responds to factors such as rainfall, runoff, river flow, light and nutrients availability. While numerous studies have...
Longshore currents are frequently occurring phenomena capable of transporting beach sediments, causing accretion and erosion of the shoreline. Forcing mechanisms are understood and well modeled for cases of alongshore homogeneous and monotonic bathymetry, yet the extension of these models to complex and irregular bathymetry sometimes fails. To test and improve...
The ecology of the North Atlantic right whale (Eubalaena glacialis) was examined at three spatial scales during the summer and early fall on their northern feeding grounds. The diving and foraging behavior of right whales was investigated at spatial scales of hundreds to thousands of meters by tagging right whales...
We consider long planetary waves of annual period linearized about a steady, wind-driven subtropical (ST) gyre circulation. The circulation divides the gyre into an eastern zone (EZ) where only the surface layer is in steady motion and a western zone (WZ) where both the surface and the middle layer are...
During October 2000 the Po River, Italy's largest river, experienced a historically significant flood, producing a deposit on the adjacent prodelta. In December 2000 an event-response study of the deposit was conducted, and during the ensuing 16 months three additional sampling cruises were conducted to study the subsequent evolution of...
Mesoscale surveys to examine the relationship between the physical processes and biological response along the Antarctic Polar Front (PF) were conducted as part of the US JGOFS Southern Ocean Program during austral spring and summer 1997/98. Multiple crossings of the PF near 170° W, using a towed undulating instrument, provided...
The Cretaceous was a period of extreme climatic conditions accompanied
by major perturbations in ocean-atmosphere biogeochemical cycles. One of the
most intriguing features is the sporadic interruption of normal marine pelagic
sediment deposition by organic rich sediments deposited during oxygen-deficient
conditions (ocean anoxic events OAEs). A current model for the...
In situ optical measurements of spectral absorption and beam attenuation provide information on the fine scale horizontal and vertical variations in phytoplankton pigments and other measures of phytoplankton photophysiology and ecology in coastal waters. Phytoplankton pigment ratios from discrete sample analyses with High Performance Liquid Chromatography were compared to in...
Few studies have examined the partitioning of organic matter in upwelling systems,
despite the fact that these systems play a key role in carbon and nitrogen budgets in the
ocean. We examined the production and partitioning of phytoplankton-derived organic
matter in deck incubations off Oregon during the upwelling season. During...
The increase in modern atmospheric CO₂ concentration (360 ppm) from
pre-industrial levels (280 ppm) raises concern over the impact of anthropogenic
carbon dioxide input on atmospheric chemistry. For this reason, it is important to
understand the natural fluctuations of atmospheric carbon dioxide in the past. The
Vostok ice core record...
I compare the seasonal abundance variation, population dynamics, fecundity, egg hatching mechanism and success, and apostome ciliate parasites of the euphausiids Euphausia pac?fica and Thysanoessa spinfera from the Oregon coast, USA. Community structure and nearshore distributions were examined from bi-weekly oceanographic surveys (1970-1972). This region has a strong cross-shelf change...
The Oregon upwelling system is a region of high biomass and primary
productivity as well as strong mesoscale variability. In order to examine the
interaction of physical forcing and ecosystem dynamics, four 3-week sampling
cruises were conducted in the Oregon upwelling system as part of the Northeast
Pacific Global Ocean...
The Galapagos Islands, located off the coast of Ecuador, have a spatially diverse marine environment suitable for a variety of species with different climatic requirements. A year-long inventory program was carried out in 2000-2001 to provide baseline data on the abundances and distribution of coastal fish and macro-invertebrates. The purposes...
Anoxic sediment overlain by oxic seawater establishes a voltage gradient on the order of 0.7-0.8V across the sediment-water interface. This study follows Reimers et al. (2001) and Tender et al. (2002) who reported the development of a seafloor fuel cell to harvest electrical energy from this potential difference. Prototype fuel...
As concern grows about the long-term effects of increasing atmospheric CO₂
concentrations, it becomes increasingly important to understand the cycling of carbon
on Earth, particularly in the dynamic marine reservoir. Gas exchange and relatively
rapid ocean mixing times mean that the oceans play a significant role in determining
the atmospheric...
Discrete layers of phytoplankton and zooplankton were observed over the Oregon continental shelf in summer and fall of 2001 and summer 2002 using optical and acoustical technologies and a pump sampling system. Layers of phytoplankton had steep vertical gradients which were associated with gradients in density and local peaks in...
During two cruises in February and June of 2003, the erodibility of sediment along the western Adriatic Sea was measured using a "Gust erosion chamber". In addition, the surficial sediment properties were characterized through a suite physical and biological measurements including porosity, grain-size, inorganic carbon, organic carbon and colloidal carbohydrate....
The effects of wind forcing on coastal ocean circulation are studied using a
numerical modeling approach. The first region of interest is on the North Carolina
shelf, where the Coastal Ocean Processes (CoOP) Inner Shelf Study (ISS) took place
during August - November 1994. ISS observations are used to initialize,...
Westward transport of water vapor across the Panama Isthmus helps to
maintain the salinity contrast between the Atlantic and Pacific Oceans, important in
thermohaline circulation and global climate. Relatively low sea-surface salinities and a
strong, shallow pycnocline in the eastern Pacific warm pool (EPWP) region near
Central America reflect high...
Within systems characterized by substantial spatial and temporal variability, abundances of organisms tend to be higher in localized areas. Within the northern California Current system, the identification of such marine, biological hotspots would be of great importance to resource managers, conservationists, and research planners, and is consequently a growing area...
Numerical model and assimilation experiments were conducted in the tropical Pacific Ocean to obtain a better understanding of the processes that control the cold tongue surface mixed layer temperature balance during August 1999 to July 2004. The numerical model was first applied to test two hypotheses (asymmetric background currents and...
In the early 1980's the first evidence of biological alteration of basalt glass (sideromelane) was published. Since that time additional evidence, including DNA staining, isotopic abundance and chemical mapping, has come to light suggesting that this unique alteration of glass can be attributed to microbial activity. Microbial alteration textures have...
Coastal-based high-frequency (HF) radar systems are an increasingly used tool for measuring surface currents in the coastal ocean. These systems provide a spatial and temporal resolution not achievable with other methods. Standard-range sites typically generate hourly maps of surface currents on a 2km grid extending approximately 50km from shore while...
We present a study of the ocean circulation using state of the art numerical and data assimilation techniques. The second chapter of the thesis presents the development and application of generalized inversion to a simple dynamical model of Lake Kinneret. The intent was to develop the necessary tools to implement...
Thermohaline interleaving is an important mechanism for laterally fluxing salt, heat, and nutrients between oceanic water masses. Interleaving is driven by a release of potential energy resulting from the vastly differing diffusivities of heat and salt in seawater. The flows are composed of stacked intrusions that flux more buoyant and...
The longshore variability of the coastal response to hurricanes may be examined within the framework of a storm-impact scaling model that compares spatially-variable beach morphology and fluid forcing. The relative elevations of dune height and storm-induced water levels are used to define three impact regimes (swash, collision, and overwash), within...
Large barite (BaSO4) structures mark cold seeps in the southern San Clemente Basin. Barium flux to San Clemente sediments is two to three times greater than fluxes measured in surrounding California Borderland basins. Analyses of sediment trap material, water column samples, sediments and pore water indicate that expected bariumbearing mineral...
Marine sediments exceptionally rich in organic carbon, known as black shales, occur globally but intermittently in well correlated Cretaceous successions. The presence of black shales indicates that sporadic, ocean-wide interruption of normal respiration of marine organic matter during oxygen-deficient conditions has occurred. Submarine volcanism on a massive scale, related to...
The effects of alongshore variability in topography (banks and capes) and spatial variability in the wind forcing, including the wind-stress curl, on coastal ocean circulation are studied using a combination of observations and model simulations. Satellite sea surface temperature observations are used to describe the seasonal evolution of temperature fronts...
The microbial loop plays a crucial role in remineralization of organic matter and fuels recycled production in the aquatic environment. The capability of microbes to utilize particular compounds can be examined through their ectoenzyme (found outside the cell) activities using fluorogenic substrate analogs. These catalysts hydrolyze polymers otherwise too large...
The North Pacific subtropical gyre (NPSG), once considered to be a biological desert due to low primary production (PP) and its associated variability, has been found more productive and variable than previously thought. The environmental conditions controlling this relatively high PP variability are yet to be elucidated, despite important implications...
Tropical instability waves (TIWs) are prominent seasonal features in both the equatorial Pacific and Atlantic Oceans. This work quantifies their role in modulating the distributions of nutrients and phytoplankton biomass. Using an eight year record of biannual ship observations along the Tropical Atmosphere Ocean (TAO) buoy array, cruise sections crossing...
Modern upwelling conditions and corresponding oceanographic properties are investigated and reconstructed for the Late Quaternary. The oceanographic conditions considered influence diatom ecology and the record of fossil diatom frustules in the sediments.
Diatoms from modern sediments are evaluated as paleoceanographic proxies and transfer functions (TFs) are calibrated using the Imbrie...
Experiments were designed to answer key questions about diatom-derived organic matter cycling (i.e., production and degradation) in coastal systems. Dissolved organic matter (DOM) production was examined in axenic batch cultures of five diatom species. Dissolved organic carbon (DOC) release rates varied between species, but were significantly higher for all species...
Our view of phytoplankton has historically revolved around their inability to
control their location in space. The term phytoplankton itself underscores this
particular difference between phytoplankton and their sessile terrestrial counterparts.
Yet there are other differences between land plants and the phytoplankton that are
perhaps equally important, beyond this sessile-planktonic...
The mathematical and physical connections between three different ways of quantifying linear predictability in geophysical fluid systems are studied in a series of analytical and numerical models. Normal modes, as they are traditionally formulated in the instabilities theories of geophysical fluid dynamics, characterize the asymptotic development of disturbances to stationary...
Plate boundaries are commonly regions of complex, diffuse deformation with
the motion across the boundary accommodated by numerous structural systems, rather
than being narrow, discrete zones of deformation. One such boundary occurs where
the North American plate makes contact with Juan de Fuca, Gorda, and Pacific plates
along the west...
The biological transformation of dinitrogen gas (N2) into combined forms(termed N2 fixation) by certain genera of oceanic cyanobacteria represents the largest incoming flux of nitrogen to the global ocean. As such, biological nitrogen fixation
plays a significant role in the regulation of oceanic productivity and the export of
carbon and...
Nares Strait is one of three main passages of the Canadian Archipelago that
channels freshwater from the Arctic Ocean to the North Atlantic. There are very few
observations regarding the role of this region on the present day Arctic freshwater budget,
and even less regarding the changes in freshwater fluxes...
An autonomous, in-situ instrument was developed to detect dissolved copper in seawater, suitable for deployment on time scales from weeks to months. A commercially available in-situ nitrate analyzer (YSI 9600) was adapted to measure copper (II) in seawater by chemiluminescence. Modifications included construction of a photomultiplier (PMT) based detector and...
This research focuses on the development of new techniques to explore terrestrial-ocean climate linkages along the Pacific Northwest-northeast Pacific Ocean margin. This is done by investigating river response to climate change and by unraveling this history preserved in continental margin sediments. A significant component of this work centers on developing...
This investigation focuses on gaining a better understanding of the complex relationship between melt generation, source variability and mid-ocean ridge morphology. The approach adopted here uses a variety of geochemical techniques to evaluate the ability of 'global' models to predict regional scale geochemical variability associated with axial depth and axial...
Interactions between surface winds and meanders in mid-latitude sea surface temperature
(SST) fronts with horizontal length scales of 100-1000 km are investigated
from satellite observations and numerical simulations. Observations from the Sea-
Winds scatterometer on the QuikSCAT satellite show that the magnitude, direction,
curl, and divergence of the surface wind...
Waves are the primary input of energy in the nearshore region, and together with the currents forced through the transfer of momentum that occurs during the wave breaking process they are the principal mechanism for sediment transport in the nearshore. The basic physics of waves and currents are thought to...
Wave-induced circulation is the defining characteristic of the nearshore. Within this region, the constant feedback cycle between incoming waves, wave-generated currents, and the mobile sediment bed is responsible for the evolution of complex patterns in nearshore and beach morphology. Central to our understanding of this system is knowledge of the...
This research incorporates geochemical and helium isotopic analyses of Lau Basin volcanic glasses, along with helium isotopic analyses of water column hydrothermal plumes to better understand the processes that control the formation and evolution of this backarc basin. Lavas newly collected from the four southernmost segments of the Valu Fa...
This study was designed to identify and characterize areas of concentrated use and diving behavior of blue whales (Balaenoptera musculus) off the California coast. During the summer of 2004, thirteen blue whales were tagged with implantable Telonics ST-15 Argos satellite-monitored radio tags and five were tagged with Telonics ST-21 Argos...
In eastern boundary current upwelling ecosystems, mesoscale circulation features such as eddies and upwelling filaments play a prominent role in the transfer of water and the associated plankton from the productive nearshore to the oligotrophic deep sea. The relationship between mesoscale circulation, zooplankton distributions, and the across-shelf transport of coastal...
Two Autonomous Underwater Vehicle Gliders have alternated continuous sampling of a 45-nautical mile transect line (the Newport Hydrographic Line) across the Oregon continental shelf since April, 2006. Strong currents (>25cm/s) push the gliders off their trajectories as they survey this transect line, preventing them from sampling the historically occupied stations...
Diatoms are a ubiquitous group of plankton responsible for 20-40% of oceanic
primary production, and a higher fraction of organic matter export to the ocean
interior. Diatoms actively transport dissolved inorganic silicon into their cells, and
through the process of silicification (i.e. biogenic silica production) they build tough
and intricate...
Oceanic crust covers nearly 70% of the Earth's surface, of which, the upper,
sediment layer is estimated to harbor substantial microbial biomass. Marine crust;
however, extends several kilometers beyond this surficial layer, and includes the
basalt and gabbro layers. In particular, the basalt layer has high permeabilities which
allows for...
Experiments were conducted with two strains of the coccolithophorid Emiliania huxleyi. Previous experiments with CCMP1742 and 372 at a light intensity of 60 µEin/m²-s showed that during five-day periods of continuous darkness, strain 1742 was taking up nitrate from the media while strain 372 was not. The nitrate uptake in...
The inherent and apparent optical properties of different ocean regimes are the basis for all optical remote sensing of the ocean. Ecological information derived from remote sensors therefore relies on having a detailed understanding of how particulate backscattering and absorption contribute to the bulk optical signal. The absorption
characteristics of...
This thesis investigates the influence of early diagenesis on trace metal and
molybdenum isotope behavior in marine and lacustrine environments. Chapter one is a
synthesis of previous research in all the marine environments investigated, providing an
essential geochemical context for interpreting the observed behavior of Mo in these settings.
Chapter...
The local and remote sources of variability of the South Atlantic Ocean are investigated using a set of numerical experiments and satellite data. A global, eddy-permitting, numerical simulation is analyzed to investigate the dynamical links between the Antarctic Circumpolar Current (ACC) and the Malvinas Current (MC). The model results indicate...
A benthic microbial fuel cell (BMFC) is an electrochemical device that
generates current from the redox gradient at the sediment-water interface. Early
prototypes had anodes buried in anoxic sediments and cathodes in overlying water.
The BMFCs described in this dissertation are based on a chamber design that enables
the use...
We investigate, theoretically and experimentally, the problem of modeling depth-integrated (2DH) surf zone circulation on an alongshore-nonuniform natural beach, with waves approaching from an arbitrary angle. An approximate theoretical model is developed, which captures the important effect of advection in the alongshore dynamics, and shows that a nondimensional parameter Re[subscript]s...
Recent works have investigated use of the hydrogen isotopic composition of C₃₇ alkenones (δD[subscript K37s]), lipid biomarkers of certain haptophyte microalgae, as an independent paleosalinity proxy. I discuss herein the factors impeding such an application and identify the potential alternative use of δD[subscript K37s] measurements as a proxy for non-thermal,...
We examine the interactions and feedbacks between bathymetry, waves, currents, and
sediment transport. The first two pro jects focus on the use of remote sensing techniques
to expand our knowledge of the nearshore. Due to the plethora of snap-shot data that is
available from satellites and their distribution via Google...
The distribution of barite (BaSO₄) in marine sediments has long been studied as a proxy for paleoproductivity. While pure barite is known to be a stable mineral in oxic sediments, it is also known that variations in the Sr/Ba ratio influence its solubility and liability during early diagenesis. To extract...
The ecological interaction between the largest coastal predator, the gray whale (Eschrichtius robustus) and the most abundant shallow water marcrozooplanktonic prey, mysids, were examined in a poorly-understood predator-prey relationship along the central Oregon coast. From 2002-2008, 83 seasonal gray whales were identified. These whales returned each year around Memorial Day...
Greenland halibut (Reinhardtius hippoglossoides) have decreased in the eastern Bering Sea and Aleutian Islands since the 1970s. The reasons behind the poor recruitment are unknown, and important knowledge gaps of the ecology of the early life stages have been identified. The objectives of thesis research were (1) to examine geographic...
We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine...
The properties and evolution of nonlinear internal waves (NLIWs) depend
upon the background conditions within which waves form, propagate, and dissipate. As a result, the NLIW field on the New Jersey shelf displayed dramatic variability during the Shallow Water 2006 experiment. Wave variability was exhibited by 1) amplitudes that ranged...
At the Costa Rica Dome (CRD), upwelling associated with cyclonic circulation and the presence of a shallow thermocline support a highly productive biological habitat, exploited by marine fauna at several trophic levels. During January 2008, a cruise to the CRD by the R/V Pacific Storm was conducted to relocate blue...
The long-term evolution of Gaussian eddies is studied in an equivalent barotropic model using both linear and nonlinear quasi-geostrophic theory in an attempt to understand westward propagating satellite altimetry tracked mesoscale eddies. By examining both individual eddies and a large basin seeded with eddies, it is shown that long term...
During four cruises in July and September of 2008 and 2009, the shipboard X-band radar was tuned to detect the modulated bands of surface roughness caused by converging and diverging currents associated with high-frequency nonlinear internal wave (NLIW) packets. The data collected was used to quantify the propagation direction (ϴp),...
The marine climate of the Galapagos is spatially and seasonally
heterogeneous. A taxonomically comprehensive study of Galapagos zooplankton has
never been done. This study is an initial effort to establish the distribution and
community structure of zooplankton in the Archipelago. I collected zooplankton
samples by vertical tows over the Galapagos...
In the summer of 2007, a biophysical experiment was conducted to identify physical processes that determine the delivery of invertebrate larvae and juvenile rockfish to rocky intertidal and kelp forest communities in northern Monterey Bay, California. The experiment was sponsored by the Partnership for Interdisciplinary
Studies of Coastal Oceans (PISCO)...
Sediments of the central Chile margin record changes in ocean circulation and
continental erosion associated with large–scale climate change. Here Antarctic–
influenced Southern Ocean currents flow equatorward, forming a link between the high–
and low–latitude oceans. Part of this link, Antarctic Intermediate Water, is an important
conduit that ventilates South...
Salmon survival and eventual recruitment success have long been thought to be determined within the first summer following ocean migration. Juvenile growth during this period is largely influenced by ocean conditions such as temperature, prey availability, abundance, and quality. Shifts in these conditions due to climatic perturbations are particularly prevalent...
A Regional Ocean Modeling System (ROMS) application for the coastal region of Kenya and Tanzania (0-10° S, 38.7-46.98° E) was developed with the aim of better resolving the circulation patterns in the coastal region that is poorly represented in global models. The model has a horizontal resolution of 4 km,...
Summertime, wind-driven upwelling off the Oregon coast delivers nutrient rich water to the surface that fuels the autotrophic production of particulate organic carbon (POC). This POC can be transported horizontally by fluid motions and vertically by sinking to the bottom where it can be entrained in the benthic boundary layer...
Dramatic and ongoing changes pervading the Arctic and subarctic seas over
recent decades have motivated this effort to track and better understand hydrographic
variability using chemical tracers. Particular emphasis has been paid to differentiating
freshwater contributions to upper layers: namely Pacific water, meteoric water, and
sea-ice melt/formation.
Data collected in...
The copepod Calanus finmarchicus is the most important and biomass dominant mesozooplankter in the temperate-boreal North Atlantic. C. finmarchicus has an overwintering phase, termed diapause, during which it descends to great depths (300-2000m) and is metabolically quiescent for up to ten months. Changes in the currents at depth due to...
Small pelagic fish represent a critical trophic link between plankton and large predators in marine upwelling ecosystems such as the California Current System. Populations of these fish are highly variable over time and are characterized by extreme fluctuations in abundance, which have significant ecosystem impacts. The causes driving
this instability...
Phagotrophic protists are major consumers of microbial biomass in aquatic ecosystems. However, biochemical mechanisms underlying prey recognition and phagocytosis by protists are not well understood. We investigated the potential roles of cell signaling mechanisms in chemosensory response to prey, and in capture of prey cells, by a marine ciliate (Uronema...
Instability and turbulence in sheared, salt-fingering favorable stratification are studied
using three-dimensional direct numerical simulations (DNS). Salt-fingering favorable
stratification is gravitationally stable, because the unstable vertical gradient of salinity
is stabilized by temperature (warm, salty over cool, fresh water-masses). Salt-fingering
instability can occur at the interface of these different water-masses....
Under conditions of fixed N-limitation, as with most oligotrophic systems, the process of biological N₂ fixation (diazotrophy) is favored, provided the necessary trace elements and vitamins are sufficient. Despite the well understood contributions of N₂
fixation in oligotrophic regions, the nutritional and ecological controls of marine diazotrophs have not been...
This dissertation investigates the dynamics of the tidally modulated outflow from the Columbia River mouth using high resolution measurements of velocity, density and turbulent microstructure. At high tide, flow through the river mouth reverses from flood (onshore) to ebb (offshore). During ebb, buoyant fluid issues from the river mouth and...
