Upwelling-diffusion climate models have shown that radiative forcing changes in the ocean surface temperature penetrate only very slowly into the intermediate ocean whereas changes in deep water formation and basin scale upwelling can affect the water temperatures at intermediate depths sizably and quickly. Hence, both mechanisms could be involved in the warming of oceans at intermediate depths that has been observed. Seeing how the heat flux at the ocean-air interface has varied through time would give us an idea of the degree to which it accounts for the rise in intermediate water temperatures and hence the lack of a marked greenhouse warming signal in the temperature record This study also looks at the overall poleward heat transport in the oceans as well as in individual ocean basins and their variation over the years To achieve these goals, the heat flux at the ocean-air interface was calculated for the 1946-1991 period using the Comprehensive Ocean Atmosphere Data Set (COADS). The heat flux was broken down into the four components of shortwave flux, longwave flux, latent, and sensible heat and individual components were calculated by the bulk parameterization method The magnitudes of the individual heat flux calculations were found to depend critically on the parameterization scheme adopted. There was however no difference in the temporal variation or spatial pattern of the individual flux components due to the parameterization scheme adopted. The net heat flux values, in turn, depended on the choice of parameterization schemes and therefore have a high uncertainty in comparison to the greenhouse radiative forcing signal that is expected to be hiding in the ocean There seems to have been a period of high heat flux into the ocean that was tapering off at the beginning of the record being analyzed. From the early 1960s the net heat flux seems to have increased till about 1980 and resumed its decreasing trend since then. One of the three net flux calculations carried out seems to be close to a zero global average for much of the period being analyzed, and therefore, likely to be the real scenario The poleward heat flux calculations show that the Pacific Ocean shows higher magnitudes in the mid latitudes compared to the Atlantic and Indian Oceans. There seems to be a signficant variation in the poleward heat transport in the individual ocean basins over the years with an apparent shift occurring around 1980. (Abstract shortened by UMI.) / acase@tulane.edu

Organic and inorganic geochemical proxies from two cores in the northeastern (NE) and western Arabian Sea were employed to study orbital and suborbital climate variability of the Indian Ocean monsoons. In the NE Arabian Sea 230Th-nonnalized 232Th fluxes and authigenic uranium concentrations were interpreted as indicators for eolian input and paleo-productivity, respectively. The highest eolian fluxes occur at times consistent with the North Atlantic (NA) millennial-scale cold intervals recorded in the GISP2 ice core. Paleoproductivity was highest during warn interstadials when the SW monsoon was intensified. Maximum average eolian fluxes coincide with the timing of marine isotopic stage 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5 231Pa/230Th activity ratios and diatom biomarker fluxes were measured in sediments from NE Arabian Sea to examine the influence global thermohaline circulation (THC) over the last 50 ka. 231Pa/230Th were significantly higher than the production ratio of 0.093, which indicates exceptionally high rates of particle scavenging. Lower average 231Pa/230Th ratios occurred during the last glacial with lowest 231Pa/230Th ratios coinciding with the timing of Heinrich Events 1 - 5. In the Holocene, high 231pa/230Th ratios may indicate enhanced 231 Pa export from the southern to the northern Indian Ocean via intensified THC Organic biomarker fluxes and alkenone-derived sea surface temperatures (SST) were measured in sediments from the western Arabian Sea. The average glacial-Holocene temperature difference was ∼3°C with an interval of exceptionally low SSTs between 19 to 18.1 ka BP (15.3°C at 18.5 ka). The lowest SSTs coincided with highest cumulative biomarker fluxes. We propose that intensification of the winter NE monsoon winds during the glacial period resulted in cold SSTs, deep convective mixing, and enhanced primary productivity. Following the last termination, and within the Holocene, SSTs vary by ∼2°C with high CBFs occurring at times of relatively warmer SSTs. Transitioning from the glacial to the Holocene, diatom fluxes relative to the total flux of organisms increased, while those of coccolithophorids decreased. A shift in the planktonic ecosystem structure in the Arabian Sea may have important implications for the global biogeochemical cycle of carbon / acase@tulane.edu

Because of high sedimentation rates in the coastal ocean, particularly along river-dominated ocean margins, estuarine and coastal sediments can be important repositories for organic carbon derived from both allochthonous and autochthonous sources. The overall objective of this research was to investigate the sources of organic carbon and the coupling between organic carbon inputs and deposition on the Mississippi river-dominated Louisiana shelf using pigment and lignin biomarker analyses. During the course of these investigations a further goal was to conduct a comparison of two common methods of lignin analyses -- CuO oxidation and TMAH thermochemolysis Direct comparisons between data yielded from each method were determined to be not comparable. While conventional TMAH analyses can be employed more quickly and efficiently than the CuO method, CuO products appears more consistent and accurate in identifying bulk lignin sources within sediments, and were determined to be more appropriate in systems with low terrestrial organic matter such as the Louisiana shelf The spatial distribution of phytoplankton pigments in surface waters varied by season and appeared strongly influenced by river discharge. Total chlorophyll concentrations ranged up to 31nM in surface waters during the period of high river discharge, and up to 1.71 mg chla 100 mg OC-1 in the sediments during low river discharge. Diatoms made up the most abundant phytoplankton taxa in this system, contributing a substantial amount of the marine-derived organic carbon to surface waters and sediments on the shelf Concentrations of terrigenous organic matter were spatially variable across the shelf, and linked to distinct regions of sediment accumulation. The highest lignin concentrations (up to 4.7 mg lignin 100 mg OC-1 ) were found closest to the river mouth and in the shallow near shore regions of the study area. While there were no discernible seasonal differences in contributions of C3 and C4 terrestrial material to the sediments, the proportions of riverine-derived, marsh-derived, and phytoplankton-derived organic carbon varied according to season and location across the shelf / acase@tulane.edu

The treatment of scattering from submerged objects in an unbounded environment is of considerable interest to both the academic and technological communities. Several approaches have yielded results for different classes of problems and have proven manageable for the free environment case. The problem of scattering in a confined environment has proven more difficult to formulate in a form useful for calculation due to the coupling of effects from the scattered object with that of the boundaries. The purpose of this work is to propose a numerical scheme that will adequately describe scattering from realistic objects in a confined environment. Some of the realistic objects that are of interest are elongated objects such as spheroids and cylinders with rounded end-caps. Boundary conditions of interest range from those associated with rigid objects to those associated with elastic shells. We will start by developing the incident field in terms of Normal Mode theory. We next develop the near field scattered field. This will be obtained using a transition matrix that relates the incident field to the scattered field. The transition matrix which is obtained from the Extended Boundary Condition (EBC) method of Waterman does not account for boundaries other than that of the object. We then couple the solution with a waveguide solution to satisfy all boundary conditions. By appropriately coupling the two solutions we can satisfy all boundary conditions and preserve continuity of the solution throughout all space. The method that couples the solutions is an application of Huygens' principle. This application of Huygens' principle leads to a manageable direct solution of the problem. This method also satisfies all appropriate boundary conditions and yields a continuous solution throughout space. Details of this method will be presented along with examples / acase@tulane.edu

The air-sea interaction thermodynamics of the western equatorial Pacific, the Earth's largest region of warm SST, is a major component of the global climate system. Along the equator, warm pool thermodynamics and momentum are influenced by equatorial ocean visco-inertial boundary layer dynamics that occur within a few degrees of the equator because of the sign reversal of the Coriolis force. Designed to study this system, COARE Enhanced Monitoring Array (EMA) observations of temperature, salinity, velocity, and surface meteorology were centered at 0, 156°E from February 1992 through April 1994. They sampled variability on the equator over larger space/time-scales than the concurrent Intensive Flux Array (IFA) centered at 2°S, 156°E. The EMA data are examined within the context of the larger scale equatorial Pacific and the El Niño conditions that occurred at that time. There is a structural change in the equatorial Pacific near the dateline resulting from the winds that are strong, steady, and easterly in the east and generally weak, punctuated by westerly wind bursts, in the west. East of the dateline the EUC's speed and transport increases downstream, while in the west it tends to be zonally uniform, consistent with the extra-tropical ocean interior water pathways that tend to converge on the equator east of the dateline. At 0°, 156°E in the western Pacific deep, seasonal upwelling (appearing stronger after the peak of the 1991/92 El Niño than during the following weaker El Niño year) occurs within the thermocline in boreal summer with magnitudes as large as upwelling in the eastern Pacific cold tongue. This large upwelling is associated with large downward turbulent heat flux and large turbulent shear stress. While the inferred mixing is quantitatively inconclusive because of unresolved potential errors, it is consistent with the visco-inertial boundary layer concepts from early theory [e.g. Arthur 1960; Robinson 1960; Stommel 1960; and Charney and Spiegel 1971]. These findings suggest that the equatorial thermodynamics differ from those of the IFA. Further process experimentation is necessary to quantify these results.

No description available.

The shoaling of horizontally propagating internal waves may provide an important source of mixing and transport in estuaries and coastal seas. Parameterizing such effects in numerical models demands better understanding of several aspects of wave energetics, especially relating to horizontal energy flux and turbulence generation. Observations are needed to build this understanding. To address some of these issues in the estuarine context, an intensive field program was undertaken in Summer 2008 in the St. Lawrence Estuary, involving shore-based photogrammetry, ship-based surveys, and moorings that held conventional and turbulence-resolving sensors. The measurements reveal that waves generally arrived during the rising phase of the M2 tide. Shoreward of the 40m isobath, waves traversed the field site perpendicular to bathymetry, a pattern that continued as the waves transformed nonlinearly. A tight temperature-salinity relationship permits the estimation of the time-varying density field from a moored chain of temperature-depth recorders. A new method for inferring the heaved internal wave density field is developed, using a relaxation solver to determine the wave streamfunction. The method is applied to discrete events measured with acoustic Doppler profilers to estimate the kinetic and available potential energy, as well as the nonlinear horizontal energy flux. Acoustic Doppler velocimeters were used to infer near-bottom turbulent energetics, revealing two main features. First, a period of wave incidence had turbulence dissipation rates that exceeded values associated with tidal shear by an order of magnitude. Second, the evolving spectral signatures associated with a particular wave-shoaling event indicate that the turbulence is at least partly locally generated. A simple model for wave-induced turbulence is proposed based on the energy flux measurements. Generally, the results suggest that during the rising phase of the tide, energy input from shoaling waves is required to explain the observed levels of dissipation. Estimates of vertical diffusivity during times of wave shoaling are on average 3 times larger than values predicted by tidal shear alone.

The El Nino phenomenon has a major impact over wide regions of the Pacific and possibly all over the world. The purpose of this thesis was to study its effects, specifically along the coast of British Columbia. An analysis of sea-surface temperature, sea-surface salinity and sea-level height was made with respect to El Nino events. Based on the results of that analysis, a model was developed. The model uses Kelvin wave dynamics, and can be used to predict the approximate time and magnitude of the sea-surface temperature anomaly created by an El Nino event. This prediction can be useful for fishermen because the anomaly of temperature has a major effect on the distribution pattern of fish. In conclusion, an analysis of water temperature and salinity anomalies as a function of depth as well as offshore distance was made.

Thesis (Ph.D.)--The Ohio State University, 2006. / (UMI)AAI3238159. Adviser: K. C. Jezek. Source: Dissertation Abstracts International, Volume: 67-10, Section: B, page: 5629.

The Southern Ocean holds a unique place in our planet. It is home to the world’s longest and strongest ocean current, the Antarctic Circumpolar Current (or ACC), which is formed of jets (alternating velocity structures), thought to be significant surface transport barriers. The dynamical processes (particularly mixing processes) in the Southern Ocean are crucial to driving the global overturning circulation, which is in turn responsible for the global transport of heat, CO2, and nutrients. Despite the evident importance of the Southern Ocean to current and future climate, the important dynamical processes that occur there are poorly understood. This thesis attempts to contribute towards the understanding of some of the open questions in Southern Ocean dynamics. In particular, we investigate the effect that topography might have on the jets that form the ACC, with regards to their formation and in particular, their transport properties. Through a quasi-geostrophic model we investigate the properties of jets that form over a zonal slope in bottom topography, and find that the jets become tilted, aligning perpendicular to the large-scale barotropic potential vorticity gradient. As the jets tilt more, they become significantly more energetic, corresponding with an increase in across-jet transport. We compare various theories regarding the formation of such jets, involving linear analysis of the system. It is found that the analytical form of the Rossby wave frequencies correctly predicts the anisotropy of the energy spectra of simulations, and so the jet direction. Additionally, there is a need to characterise accurately the isopycnal mixing occurring throughout the Southern Ocean. We utilise satellite measurements to estimate isopycnal diffusivities in the Southern Ocean in two different studies. Using an effective diffusivity diagnostic to extend a previous study, we find reduced surface horizontal mixing at the latitudes of the ACC core. By comparing a tracer advection simulation with measurements from an experiment in the Southern Ocean, we find that simulations with a vertically averaged horizontal diffusivity of 20m2s−1 best match observations in the Pacific sector of the ACC.