Oceanography Commons^™

Strong Mid-Depth Currents And A Deep Cyclonic Gyre In The Gulf Of Mexico, Wilton Sturges, Eric Chassignet, Tal Ezer

CCPO Publications

The main purpose of this work was to explore the possibility that the deep flow (~2000m) around the edges of the Gulf circulates in a cyclonic, or counter-clockwise direction. The existence of such flow was proposed on theoretical grounds but had not been previously documented. Our results are quite clear that such flow is reliably observed.

Fall 2003, Nsu Oceanographic Center

Currents

No abstract provided.

Wind-Induced Exchange In Semi-Enclosed Basins, Rosario Sanay

OES Theses and Dissertations

The wind-induced circulation over laterally varying bathymetry was investigated in homogeneous and in stratified systems using the three-dimensional Regional Ocean Model (ROMS). For homogeneous systems, the focus was to describe the influence of the earth's rotation on the lateral distribution of the flow with particular emphasis on the transverse circulation. Along-basin wind-stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain. Transverse circulation was important only at the head of the system where the water sank and reversed direction …

Summer 2003, Nsu Oceanographic Center

Currents

No abstract provided.

Chemical Characterization Of Ambient Aerosol Collected During The Northeast Monsoon Season Over The Arabian Sea: Labile-Fe(Ii) And Other Trace Metals, Anne M. Johansen, Michael R. Hoffmann

All Faculty Scholarship for the College of the Sciences

Ambient aerosol samples were collected over the Arabian Sea during the month of March of 1997, aboard the German R/V Sonne, as part of the German Joint Global Ocean Flux Study (JGOFS) project. This is the third study in a series of analogous measurements taken over the Arabian Sea during different seasons of the monsoon. Dichotomous high‐volume collector samples were analyzed for ferrous iron immediately after collection, while trace metals, anions, and cations were determined upon return to the laboratory. The main crustal component was geochemically well represented by the average crustal composition and amounted to 5.94 ± 3.08 …

Global Patterns Of Dissolved N, P And Si In Large Rivers, R. Eugene Turner, Nancy N. Rabalais, D. Justic', Q. Dortch

Faculty Publications

The concentration of dissolved inorganic nitrogen (DIN), dissolved nitrate-N, Total-N (TN), dissolved inorganic phosphate (DIP), total phosphorus (TP), dissolved silicate-Si (DSi) and their ratios in the world's largest rivers are examined using a global data base that includes 37% of the earth's watershed area and half its population. These data were compared to water quality in 42 subbasins of the relatively well-monitored Mississippi River basin (MRB) and of 82 small watersheds of the United States. The average total nitrogen concentration varies over three orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations …

Spring 2003, Nsu Oceanographic Center

Currents

No abstract provided.

Valuation Of Continuous And Intermittent Phragmites Control, R. Eugene Turner, R. S. Warren

Faculty Publications

Quantifying the relative value of Phragmites australis and Spartina alterniflora habitat is important to evaluate the benefits and risks of different attempts to address Phragmites expansion on the U.S. eastern seaboard. Two contrasting approaches commonly used to restore tidal marsh habitats invaded by Phragmites communities involve spraying Phragmites with herbicide only when its coverage of a particular marsh area is near or close to 100%. Alternatively, after the first application, herbicide is annually applied on any surviving patches of Phragmites present in a mosaic of other marsh vegetation. A model is introduced to evaluate the relative habitat value of these …

Engineering The Ocean, Marcia Mcnutt

IMSA Great Minds Program ®

Developments in microprocessors, artificial intelligence, and new forms of power and communications for autonomous systems are already bringing about a revolution in our ability to explore, experiment within, and ultimately understand Earth's last frontier: the ocean. It is inevitable, with this growing capability, that there will be pressure to use the same and similar technology to manipulate and enhance the ocean environment, just as we have our terrestrial environment. We will be able to fertilize the ocean to increase its productivity, adjust its climate in an attempt to halt natural and human-induced global change, harvest its internal energy to power …

Climatic Influences On Riverine Nitrate Flux: Implications For Coastal Marine Eutrophication And Hypoxia, Dubravko Justic, R. Eugene Turner, Nancy N. Rabalais

Faculty Publications

The average nitrate flux of the lower Mississippi River increased 3.3-fold between 1954–1967 and 1983–2000. During the same time period, the average nitrate concentration increased 2.3-fold while the average discharge increased 40%. Partitioning of the observed trend in nitrate flux among the two flux components, nitrate concentration and discharge, revealed that about 80% of the observed increase in flux could be explained by the increase in nitrate concentration. This indicates that a historical increase in the anthropogenic nutrient inputs has had a far greater impact on the lower Mississippi River nitrate flux than a change in climate. The influence of …

Charting Neptune's Realm: From Classical Mythology To Satellite Imagery, Osher Map Library And Smith Center For Cartographic Education

Osher Map Library Exhibition Catalogs

Charting Neptune's Realm: From Classical Mythology to Satellite Imagery.

April 4, 2000 to January 11, 2001

The charts in this exhibition explore how mariners have distinguished one piece of water from any other, by determining what phenomena can be delineated across the vast, trackless ocean and by developing notations to express those phenomena.

Experimental Investigation Of Elemental Incorporation In The Otoliths Of Larval And Juvenile Fish: Implications For Use As Environmental Recorders, Gretchen Bath Martin

Biological Sciences Theses & Dissertations

Innovative techniques for discerning fish stocks, identifying nursery habitats, locating spawning sites, tracing larval transport pathways, and quantifying the degree of population connectivity are required to meet the goals of sustainable management of marine capture fisheries. One of the most promising techniques is the use of elemental signatures in fish otoliths (ear stones), which record valuable life history data and serve as the link between fish and their environment. To validate the assumption that otolith elemental composition is a function of water elemental concentrations, and to address the possible effects of external variables such as temperature and salinity, the composition …

Effects Of Epiphyte Load On Optical Properties And Photosynthetic Potential Of The Seagrasses Thalassia Testudinum Banks Ex König And Zostera Marina L, Lisa A. Drake, Fred C. Dobbs, Richard C. Zimmerman

OES Faculty Publications

The biomass and optical properties of seagrass leaf epiphytes were measured to evaluate their potential impact on the photosynthetic performance of the seagrasses Thalassia testudinum Banks ex König (turtlegrass) and Zostera marina L. (eelgrass). Turtlegrass was obtained from oligotrophic waters near Lee Stocking Island, Bahamas; eelgrass was collected from a eutrophic environment in Monterey Bay, California. Leaf–epiphyte loads were characterized visually and quantified using measurements of their phospholipid biomass. Light absorption and reflectance of the intact epiphyte layer were determined spectrophotometrically. Turtlegrass epiphytes from the oligotrophic site absorbed a maximum of 36% of incident light in peak chlorophyll absorption …

A Biooptical Model Of Irradiance Distribution And Photosynthesis In Seagrass Canopies, Richard C. Zimmerman

OES Faculty Publications

Although extremely vulnerable to coastal eutrophication, seagrasses represent important structuring elements and sources of primary production in shallow waters. They also generate an optical signature that can be tracked remotely. Accurate knowledge of light absorption and scattering by submerged plant canopies permits the calculation of important plant- and ecosystem-level properties, including rates of photosynthesis, vegetation abundance, and distribution. The objectives of this study were to develop a realistic, yet simply parameterized two-flow model of plane irradiance distribution through a seagrass canopy submerged in an optically active water column, to evaluate its performance against in situ measurements, and to explore the …

Extracellular Enzyme Activity And Uptake Of Carbon And Nitrogen Along An Estuarine Salinity And Nutrient Gradient, Margaret R. Mulholland, Cindy Lee, Patricia M. Gilbert

OES Faculty Publications

Amino acid oxidation (AAO) and peptide hydrolysis (PH) are processes affecting the recycling of organic material and nutrients. We compared extracellular AAO and PH rates to C and N uptake rates along estuarine gradients of salinity, nutrients and productivity in the Pocomoke River, a subestuary of the Chesapeake Bay. This estuary is seasonally depleted in inorganic N, and rich in dissolved organic material (DOM) throughout the year. AAO, PH, and N uptake rates measured in 1999 and 2000 were not limited to particular size fractions measured, or to auto- or heterotrophic groups of organisms. At a station near the turbidity …

Sources Of Sediment Found In Sea Ice From The Western Arctic Ocean, New Insights Into Processes Of Entrainment And Drift Patterns, Dennis A. Darby

OES Faculty Publications

The geochemical fingerprint of entrained Fe oxide mineral grains in Arctic Ocean sea ice is used to determine precise sources of this sediment. This approach substantiates the importance of the Laptev Sea as a source of sea ice and even the presence of Russian ice in the Beaufort Sea off Alaska. Fe oxide grains from the Laptev Sea were found in floes in the Beaufort Sea, Chukchi Borderland, and central Arctic Ocean, demonstrating the importance of sea ice in distributing itself throughout the Arctic Ocean and the potential of transporting sediment from Russian rivers to North American shelves. Banks Island …

Methods And Models For Estimating Advective Pore Water Exchange In Tidal Flats, Timothy J. Shaw

Faculty Publications

No abstract provided.

The Variability Of Currents In The Yucatan Channel: Analysis Of Results From A Numerical Ocean Model, Tal Ezer, Lie-Yauw Oey, Hyun-Chul Lee, Wilton Sturges

CCPO Publications

The flow through the Yucatan Channel and into the Gulf of Mexico is a major component of the Gulf Stream and the subtropical gyre circulation. Surprisingly, however, little is known about the forcing and physical parameters that effect the current structures in the Channel. This paper attempts to improve our understanding of the flow through the Channel with a detailed analysis of the currents obtained from a primitive-equation model that includes the Gulf and the entire Caribbean Sea and forced by 6-hourly wind from ECMWF. The analysis includes two parts: First, the overall statistics of the model results, including the …

Near-Surface Currents In Desoto Canyon (1997–99): Comparison Of Current Meters, Satellite Observation, And Model Simulation, Dong-Ping Wang, Lie-Yauw Oey, Tal Ezer, Peter Hamilton

CCPO Publications

This study evaluates a data-assimilated model simulation of near-surface circulation in DeSoto Canyon (DSC), Gulf of Mexico, with emphasis on analyzing moored current-meter observations and comparing them with satellite data and model results. The study period is for two years from April 1997 to April 1999. The model results are from a high-resolution Gulf of Mexico model forced by analyzed wind and surface heat flux. Two types of data are used to deduce near-surface circulation: moored current meters at 13 locations in the DSC, and satellite sea level anomaly. The moored currents are mapped through multivariate objective analysis to produce …

Bio-Optical Properties Of The Labrador Sea, Glenn F. Cota, W. Glen Harrison, Trevor Platt, Shubha Sathyendranath, Venetia Stuart

CCPO Publications

Three cruises were conducted during fall and spring in the Labrador Sea to investigate the effects of bio-optical properties on satellite retrievals of phytoplankton chlorophyll in this important high-latitude ecosystem. Taxon-specific and regional differences were found. Diatoms had similar to 1.5 lower chlorophyll-specific absorption but significantly higher reflectance ratios than prymnesiophytes. Particulate absorption at 443 nm for total, phytoplankton, and "detrital'' fractions was related to chlorophyll, but values were lower than reported for lower latitudes. Decreased particulate absorption is attributed primarily to pigment packaging, while low backscattering to scattering ratios result from a lower relative abundance of bacteria and picophytoplankton …

Reversing Circulation Patterns In A Tropical Estuary, Arnoldo Valle-Levinson, Kathryn T. Bosley

CCPO Publications

A combination of current velocity and water density measurements was used to characterize the basic patterns of water exchange in the Gulf of Fonseca, a tropical estuary on the Pacific Ocean side of Central America. The measurements were obtained during spring and neap tides in March ( dry season) and June ( wet season) of 2001 and consisted of profiles of current velocity and density along four transects. From mid-March to mid-April a time series of hourly surface current velocity maps was also obtained with a high-frequency radar system of two antennas. The sampling transects and the radar coverage concentrated …

The Aqueous Phase Yield Of Alkyl Nitrates From Roo+No: Implications For Photochemical Production In Seawater, Elizabeth E. Dahl, Eric S. Saltzman, Warren J. De Bruyn

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Alkyl nitrates have been observed in remote oceanic regions of the troposphere and in the surface ocean. The mechanism for their production in the oceans is not known. A likely source is the reaction of ROO + NO (where R is an alkyl group). Steady-state laboratory experiments show that alkyl nitrates are produced in the aqueous phase via this reaction, with branching ratios of 0.23 +/- 0.04, 0.67 +/- 0.03, and 0.71 +/- 0.04 for methyl, ethyl, and propyl nitrate respectively. The branching ratios in aqueous solution are significantly higher than in the gas phase. Irradiation of surface seawaters yield …

Academic Fleet Renewal- Two Years Later, Larry Atkinson

CCPO Publications

(First paragraph) In November 2000, I wrote a Soapbox article on fleet renewal for Sea Technology. It is a little unsettling to see how slowly ideas move towards implementation. Nevertheless, we are making progress. In this editorial I will note a bit of that progress and try to guess where we will be in two more years.

Observations Of Cross Channel Structure Of Flow In An Energetic Tidal Channel, Mario Caceres, Arnoldo Valle-Levinson, Larry P. Atkinson

CCPO Publications

[1] Measurements of velocity and density profiles were made to describe the transverse structure of flow in Chacao Channel, Southern Chile (41.75 degreesS), where typical tidal velocities are similar to4 m/s. Current profiles were obtained with a 307.2 kHz Acoustic Doppler Current Profiler (ADCP) over 25 repetitions of a cross-channel transect during one semidiurnal tidal cycle. The 2.2 km long transect ran northeast/southwest across the channel. A northern channel (120 m deep) and a southern channel (85 m deep) were separated by Remolinos Rock, a pinnacle that rises to 20 m depth at similar to0.7 km from the southern side. …

Flow Induced By Upwelling Winds In An Equatorward Facing Bay: Gulf Of Arauco, Chile, Arnoldo Valle-Levinson, Larry P. Atkinson, Dante Figueroa, Leonardo Castro

CCPO Publications

[1] Shipborne observations of hydrographic and flow velocity profiles were combined with wind velocity measurements to describe the characteristics of the wind-induced flow in an equatorward facing bay of central Chile in South America. The measurements, which were taken from two transects and one anchor station, were made during late austral spring, between 4 and 10 December 2000. Most observations concentrated on Boca Grande, a transect that crossed the deep, northern ( equatorward) entrance to the bay. The other transect crossed the smaller and shallower, westward entrance to the bay, Boca Chica. The anchor station was located inside the bay, …

Winter 2003, Nsu Oceanographic Center

Currents

No abstract provided.