Physical Sciences and Mathematics Commons^™

The Effect Of Arctic River Hydrological Cycles On Arctic Ocean Circulation, Peter Becker

OES Theses and Dissertations

Understanding Arctic Ocean circulation may be critical to fully understanding the global oceanic salt and heat cycles and their response to climate variability. This thesis examines how one important aspect of Arctic Ocean circulation, the effect of freshwater inflow, may contribute to the variability of these cycles. The multiple roles that freshwater runoff performs in the Arctic Ocean include: (1) the formation of shelf and basin scale density currents; (2) maintenance of the strong density stratification; (3) control of the thickness and strength of the ice pack; and (4) control of deep convection. Sources and sinks of freshwater in the …

On The Interpentadal Variability Of The North Atlantic Ocean: Model Simulated Changes In Transport, Meridional Heat Flux And Coastal Sea Level Between 1955-1959 And 1970-1974, Tal Ezer, George L. Mellor, Richard J. Greatbatch

CCPO Publications

Previous studies by Greatbatch et al. (1991) indicate significant changes in the North Atlantic thermohaline structure and circulation between the pentads 1955–1959 and 1970–1974, using data analyzed by Levitus (1989a,b,c) and a simple diagnostic model by Mellor et al. (1982). In this paper these changes are modeled using a three-dimensional, free surface, coastal ocean model. Diagnostic and short-term prognostic calculations are used to infer the dynamically adjusted fields corresponding to the observed hydrographic and wind stress climatology of each pentad. While the results agree with earlier studies indicating that the Gulf Stream was considerably weaker (by about 30 Sv) during …

The Evolution Of Density-Driven Circulation Over Sloping Bottom Topography, G. H. Wheless, J. M. Klinck

CCPO Publications

The short timescale temporal evolution of buoyancy-driven coastal flow over sloping bottom topography is examined using a two-dimensional, vertically averaged numerical model. Winter shelf circulation driven by a coastal ''point source'' buoyancy flux is modeled by initiating a coastal outflow with density anomaly epsilon into well-mixed shelf water. The nonlinear interaction between the time-varying velocity and density field is represented by an advection-diffusion equation. Three cases are discussed: that of a buoyant (epsilon < 0) outflow, a neutral (epsilon = 0) outflow, and a dense (epsilon > 0) outflow. Results are similar to observations from well-mixed shelf areas and show that density-topography interactions are capable of substantially influencing coastal circulation. A negative (buoyant) coastal …

A Feasibility Study Of Dynamical Assimilation Of Tide Gauge Data In The Chesapeake Bay, Yvette H. Spitz

OES Theses and Dissertations

The feasibility of dynamical assimilation of surface elevation from tide gauges is investigated to estimate the bottom drag coefficient and surface stress as a first step in improving modeled tidal and wind-driven circulation in the Chesapeake Bay. A two-dimensional shallow water model and an adjoint variational method with a limited memory quasi-Newton optimization algorithm are used to achieve this goal.

Assimilation of tide gauge observations from ten permanent stations in the Bay and use of a two-dimensional model adequately estimate the bottom drag coefficient, wind stress and surface elevation at the Bay mouth. Subsequent use of these estimates in the …

Thermocline Circulation Driven At Surface Outcrops Of Isopycnal Surfaces, Gudavalli V. R. K. Vittal

OES Theses and Dissertations

Potential vorticity (PV) defined as: q = Δθ ^.(fk + Ω)

where θ is density anomaly, Ω (Δ x u) is relative vorticity, k is unit vertical vector and f the coriolis parameter, is used as a dynamical tracer to study the interior thermocline circulation. Using the generalized flux form of PV equation (Haynes and McIntyre, 1987), wind stress and buoyancy fluxes at surface outcrops of isopycnal surface are translated into PV fluxes. The PV flux condition so derived considers seasonal movement of the isopycnal outcrops and geostrophic turbulence.

A constant layer depth model, forced by the above flux …

Dynamics Of Dipoles In The Middle Atlantic Bight, Bruce L. Lipphardt Jr.

OES Theses and Dissertations

Beginning with the observations made by the Warm-Core Rings program in the early 1980's, several Gulf Stream warm-core rings (WCR's) in the Middle Atlantic Bight (MAB) have been observed with one or more cyclones around their periphery. These ring systems are observed in the slope water between the Gulf Stream's western boundary and the shelf break. Observations of ring systems have motivated a reanalysis of existing satellite surface temperature imagery, which revealed that multipole structure is common for both warm and cold core rings. This suggests that rings are better characterized as one part of multipole systems rather than as …

Growth Characteristics Downstream Of A Shallow Bump: Computation And Experiment, Ronald D. Joslin, Chester E. Grosch

CCPO Publications

Measurements of the velocity field created by a shallow bump on a wall revealed that an energy peak in the spanwise spectrum associated with the driver decays and an initially small-amplitude secondary mode rapidly grows with distance downstream of the bump. Linear theories could not provide an explanation for this growing mode. The present Navier-Stokes simulation replicates and confirms the experimental results. Insight into the structure of the flow was obtained from a study of the results of the calculations and is presented.

Description And Vorticity Analysis Of 50-Day Oscillations In The Western Tropical Region Of The Cme Model, Julie L. Mcclean, John M. Klinck

CCPO Publications

The WOCE Community Modeling Effort (CME) general circulation model of the North Atlantic was used to investigate the behavior, nature, and dynamics of 50-day oscillations seen in the meridional component of velocity between 5 degrees and 11 degrees N, 35 degrees and 55 degrees W. Oscillations of the meridional component of velocity, with a period of about 50 days, appear as the seasonal meander pattern of the North Equatorial Countercurrent starts to break down in December. They appear first near 35 degrees W and are advected westward. They have a westward phase velocity of about 0.1 m s(-1), wavelength of …

The Palmer Lter: A Long-Term Ecological Research Program At Palmer Station, Antarctica, Raymond C. Smith, Karen S. Baker, William R. Fraser, Eileen E. Hofmann, David M. Karl, John M. Klinck, Langdon B. Quetin, Barbara B. Prezelin, Robin M. Ross, Wayne Z. Trivelpiece, Maria Vernet

CCPO Publications

THE ANTARCTIC marine ecosystem-the assemblage of plants, animals, ocean, sea ice, and island components south of the Antarctic Convergence is among the largest readily defined ecosystems on Earth (36 X 106 km2 ) (Hedgpeth, 1977; Petit et al., 1991). This ecosystem is composed of an interconnected system of functionally distinct hydrographic and biogeochemical subdivisions (Treguer and Jacques, 1992) and includes open ocean, frontal regions, shelf-slope waters, sea ice, and marginal ice zones. Oceanic, atmospheric, and biogeochemical processes within this system are thought to be globally significant, have been infrequently studied, and are poorly understood relative to more accessible marine ecosystems …

Vorticity Balance Of Outcropping Isopycnals, G. T. Csanady, G. Vittal

CCPO Publications

The authors extend Marshall and Nurser's analysis of potential vorticity (PV) flux into outcropping isopycnic layers of the oceanic thermocline to the nonstationary case, allowing for the seasonal migration of isopycnal surfaces under surface heating and cooling. The most important new result is that the bulk of the surface PV flux arising from seasonal heating is used up in creating stratification as an isopycnal outcrop moves northward, extending the stratified layers of the thermocline. Residual PV transport (flux times the separation distance between adjacent isopycnals) reaching the interior thermocline is small in quiescent regions where only mean advection (connecting to …

Transport, Potential Vorticity, And Current/Temperature Structure Across Northwest Providence And Santaren Channels And The Florida Current Off Cay Sal Bank, Kevin D. Leaman, Peter S. Vertes, Larry P. Atkinson, Thomas N. Lee, Peter Hamilton, Evans Waddell

CCPO Publications

Currents and temperatures were measured using Pegasus current profilers across Northwest Providence and Santaren Channels and across the Florida Current off Cay Sal Bank during four cruises from November 1990 to September 1991. On average, Northwest Providence (1.2 Sv) and Santaren (1.8 Sv) contribute about 3 Sv to the total Florida Current transport farther north (e.g., 27°N). Partitioning of transport into temperature layers shows that about one-half of this transport is of ''18°C'' water (17°C-19.5°C); this can account for all of the ''excess'' 18°C water observed in previous experiments. This excess is thought to be injected into the 18°C layer …

Fisheries And Oceanography Off Galicia, Nw Spain: Mesoscale Spatial And Temporal Changes In Physical Processes And Resultant Patterns Of Biological Productivity, K. R. Tenore, M. Alonsonval, L. P. Atkinson, J. M. Cabanas, R. M. Cal, H. J. Campos, F. Castillejo, E. J, Chesney, N. Gonzalez, R. B. Hanson, C. R. Mcclain, A. Miranda, M. R. Roman, J. Sanchez, G. Santiago, L. Valdes, M. Varela, J. Yoder

CCPO Publications

The Galician shelf off NW Spain (43N degrees 9W degrees) exhibits mesoscale spatial and temporal changes in biological productivity associated with upwelling. Spatial heterogeneity results from local geomorphic and land-sea interactions superimposed on the large scale atmospheric processes that produce upwelling. Wind-induced upwelling events, commonly of short (i.e., week) duration, are more common in the summer than in the winter. A Series of cruises, including some time series sampling, and satellite imagery analysis showed that surface upwelling was more common and persistent on the northern coast compared with the western coast off the coastal embayments, the Rias Bajas. Nearshore off …

Influence Of Zooplankton Grazing On Free Dissolved Enzymes In The Sea, Alexander B. Bochdansky, Staša Puškarić, Gerhard J. Herndl

OES Faculty Publications

In the Northern Adriatic Sea, extracellular enzymatic activity was measured during a Lagrangian study following a drifting buoy for 40 h. Dissolved free enzymatic activity represented 20 to 70% of total activity depending on the type of enzyme. alpha- and beta-glucosidases exhibited a significantly higher free activity than proteolytic enzymes. In subsequent laboratory experiments we investigated the effect of zooplankton on the free enzyme pool. The 4-step approach included: (1) determination of the enzymatic activities in copepods (mainly Acartia clausi); (2) enzymatic activity in fecal pellets; (3) short- and long-term grazing experiments; and (4) degradability of free glucosidase in seawater. …

Elimination Of Dissolved Sulfide Interference In The Flow-Injection Determination Of Sigma-Co2 By Addition Of Molybdate, Rigel L. Lustwerk, David J. Burdige

OES Faculty Publications

A previously described flow injection method for the analysis of ΣCO₂ included the addition of ZnCl₂ to some samples before analysis in order to precipitate dissolved sulfide (which interferes with the method) as ZnS. However, the use of Zn²⁺ in samples with high concentrations of dissolved sulfide causes the coprecipitation of ZnCO₃, and in our experience with this technique, ZnCO₃ also precipitates even in the absence of dissolved sulfide. The addition of molybdate effectively complexes dissolved sulfide without interfering with the determination of ΣCO2 by this technique.

Thermohaline Structure Of An Eddy-Resolving North Atlantic Model: The Influence Of Boundary Conditions, John M. Klinck

CCPO Publications

A T-S volumetric census, with a resolution of 0.2 degrees C and 0.1 psu, for years 20-25 of the World Ocean Circulation Experiment Community Modeling Effort eddy-resolving simulation of the equatorial and North Atlantic Ocean, reveals how the thermohaline character of the model has changed from the initial conditions, which were taken from the Levitus climatology. Any changes in the thermohaline structure, other than stirring, mixing, or geostrophic adjustment of smoothed climatology, must be due to the boundary conditions, which are imposed at the surface and at four sponge layers (northern boundary, southern boundary, Labrador Sea and Mediterranean Sea), where …

The Oceanographer's Toolkit: Common Data Formats, Larry Atkinson, Steve Hankin

CCPO Publications

Imagine that you were handed a disk full of data saying nothing but, “Plot it up!” With common data formats that are machine independent and self-describing, you could do that and expect success.

Current Meter Observations In The Old Bahama Channel, L. P. Atkinson, T. Berger, P. Hamilton, E. Waddell, K. Leaman, T. N. Lee

CCPO Publications

Current meter observations were made at 50, 250, and 435 m in 495 m of water at the center of the Old Bahama Channel between November 1990 and November 1991. The mean speed at those depths was 2.6, 50, and 26 cm s^-1 toward the Straits of Florida. A maximum speed of 193 cm s^-1 was found at the 250-m level. There was evidence of a speed maximum between 50 and 250 m. Large internal diurnal tidal currents were observed that produced high shears in the water column under some conditions. Transport calculated from the single mooring using …

Mississippi River Flood Waters That Reached The Gulf Stream, Peter B. Ortner, Thomas N. Lee, Peter J. Milne, Rod G. Zika, M. Elizabeth Clarke, Guillermo P. Podesta, Peter K. Swart, Patricia A. Tester, Larry P. Atkinson, Walter R. Johnson

CCPO Publications

Distributions of physical, biological, and chemical parameters in Florida Keys coastal waters seaward of the reef track were surveyed on September 9 to 13, 1993, as part of a coordinated multidisciplinary study of surface transport processes. A band of low-salinity water was observed along the shoreward side of the Florida Current over the downstream extent of the survey from Miami to Key West. Biological and chemical indicators within the band, together with its large volume, satellite imagery, and a surface drifter trajectory suggested the recent Mississippi River flood as the source.

Seasonal Variability Of Heat And Mass Transport Process In The Upper Tropical Atlantic Ocean: A Numerical Model Study, Sang-Ki Lee

OES Theses and Dissertations

A simple 2.5 layer numerical model was developed and used to illustrate the seasonal variability of heat and mass transports in the upper tropical Atlantic Ocean, associated with the seasonal movement of the Inter-Tropical Convergence Zone (ITCZ). The model ocean was forced by seasonally varying climatological wind and heat flux fields. The entrainment at the base of the mixed layer was scaled by wind stress and shear at the bottom of the mixed layer. On an annual average, the northward transport of the tropical warm water is about 11 Sv, with roughly 10 Sv associated with entrainment of upper thermocline …

Time To Metamorphosis Of Blue Crab Callinectes Sapidus Megalopae: Effects Of Benthic Macroalgae, Robert D. Brumbaugh, John R. Mcconaugha

OES Faculty Publications

There is growing evidence that postlarvae (megalopae) of the blue crab Callinectes sapidus can slow the progression through the molt cycle while in offshore nursery grounds, and delay metamorphosis until reinvasion of coastal habitat occurs. However, the cues that trigger metamorphosis of megalopae are not well known. This study tested the hypothesis that the time to metamorphosis (TTM) from the postlarval megalops stage to the first crab stage is shortened in the presence of 2 potential macroalgal settlement substrates, Ulva lactuca (Chlorophyta), and Gracilaria spp. (Rhodophyta). Megalopae and test water were collected from 3 locations (offshore, at a coastal inlet, …