One problem of interest to the oceanic engineering community is the detection and enhancement of internal wakes in open water synthetic aperture radar (SAR) images. Internal wakes, which occur when a ship travels in a stratified medium, have a "V" shape extending from the ship, and a chirp-like feature across each arm. The Radon transform has been applied to the detection and the enhancement problems in internal wake images to account for the linear features while the wavelet transform has been applied to the enhancement problem in internal wake images to account for the chirp-like features. Although the Radon transform accentuates linear features, there have been several difficulties applying this transform to the wake detection and enhancement problem because the transform is not localized. In a recent article by Copeland et. al., a localized Radon transform (LRT) was developed and was shown to reduce the speckle noise. In this dissertation, another derivation of the LRT is obtained which shows that this transform is equivalent to the Radon transform with a rectangular window function. Several properties not considered in the article are derived using the new formulation. Another transform which has been applied to internal wake images is the wavelet transform. In a recent paper by Teti et. al., the wavelet transform was applied to slices through internal wakes in SAR images. Although the wavelet transform reduced the speckle noise in SAR wake images, it required extracting a line from the image. In this dissertation, a wavelet localized Radon transform is developed which performs the wavelet transform on all lines in an image without explicitly extracting slices of the image. The fundamental theory for this transform is developed and several examples are considered. This transform is then expanded to include features which occur over a region with a significant length. The fundamental theory for this new transform, a localized Radon transform with a wavelet filter, is developed and several examples are provided. These new transforms are then incorporated into optimal and sub-optimal detection schemes for images with linear features, including ship wakes, which are contaminated by additive Gaussian noise.

The ability to conduct in-flight, absolute radiometric calibrations of ocean color sensors will determine their usefulness in the decade to come. On-board calibration systems are often integrated into the overall design of such sensors and have claimed uncertainty levels below 5%. Independent means of system calibration are needed to confirm that the sensor is accurately calibrated. Vicarious (i.e. ground-referencing) methods are an attractive way to conduct this verification. This research describes the development of in-flight, absolute radiometric calibration methods which reference dark (i.e. low-reflectance) sites. The high sensitivity of ocean color sensors results in saturation over bright surfaces. Low-reflectance targets, such as water bodies, are therefore required for their vicarious calibration. Sensitivity analyses of the reflectance-based and radiance-based techniques, when applied to a water target, are performed. Uncertainties in atmospheric parameters, surface reflectance measurements, and instrument characterization are evaluated for calibrations of a representative ocean color sensor. For a viewing geometry near the sun glint region, reflectance-based uncertainties range between 1.6% and 2.3% for visible and near-IR wavelengths; radiance-based uncertainties range between 6.8% and 20.5%. These studies indicate that better characterization of aerosol parameters is desired and that radiometer pointing accuracy must be improved to make the radiance-based method useful. The uncertainty estimates are evaluated using data from a field campaign at Lake Tahoe in June, 1995. This lake is located on the California-Nevada border and has optical characteristics similar to oceanic waters. Aircraft-based radiance data and surface measurements of water reflectance are used to calibrate visible and near infrared bands of the Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS). The vicariously-derived calibration coefficients are compared to those obtained from a preflight calibration of AVIRIS. The results agree at the 0.3-7.7% level for the reflectance-based technique, which is within the believed method uncertainties. Finally, as a consequence of this research, the testing and refinement of radiative transfer codes applicable to oceanic environments is accomplished. These modifications lead to an improvement in the prediction of top-of-atmosphere radiances over water targets.

A micrometeorological station was established on the sea ice at Tanquary Fiord, Northern Ellesmere Island, during the late spring and early summer period of 1964. [...]

<p> I present the development of instrumentation and methods for the measurement of coastal processes, ocean surface phenomena, and air-sea interaction in two parts. In the first, I discuss the development of a portable scanning lidar (light detection and ranging) system for manned aircraft and demonstrate its functionality for oceanographic and coastal measurements. Measurements of the Southern California coastline and nearshore surface wave fields from seventeen research flights between August 2007 and December 2008 are analyzed and discussed. The October 2007 landslide on Mt. Soledad in La Jolla, California was documented by two of the flights. The topography, lagoon, reef, and surrounding wave field of Lady Elliot Island in Australia's Great Barrier Reef were measured with the airborne scanning lidar system on eight research flights in April 2008. Applications of the system, including coastal topographic surveys, wave measurements, ship wake studies, and coral reef research, are presented and discussed. </p><p> In the second part, I detail the development of instrumentation packages for small (18 &ndash; 28 kg) unmanned aerial vehicles (UAVs) to measure momentum fluxes and latent, sensible, and radiative heat fluxes in the atmospheric boundary layer (ABL), and the surface topography. Fast-response turbulence, hygrometer, and temperature probes permit turbulent momentum and heat flux measurements, and short- and long-wave radiometers allow the determination of net radiation, surface temperature, and albedo. Careful design and testing of an accurate turbulence probe, as demonstrated in this thesis, are essential for the ability to measure momentum and scalar fluxes. The low altitude required for accurate flux measurements (typically assumed to be 30 m) is below the typical safety limit of manned research aircraft; however, it is now within the capability of small UAV platforms. Flight tests of two instrumented BAE Manta UAVs over land were conducted in January 2011 at McMillan Airfield (Camp Roberts, CA), and flight tests of similarly instrumented Boeing-Insitu ScanEagle UAVs were conducted in April 2012 at the Naval Surface Warfare Center, Dahlgren Division (Dahlgren, VA), where the first known direct flux measurements were made from low-altitude (down to 30 m) UAV flights over water (Potomac River). During the October 2012 Equatorial Mixing Experiment in the central Pacific aboard the R/V <i>Roger Revelle</i>, ship-launched and recovered ScanEagles were deployed in an effort to characterize the marine atmospheric boundary layer structure and dynamics. I present a description of the instrumentation, summarize results from flight tests, present preliminary analysis from UAV flights off of the <i>Revelle</i>, and discuss potential applications of these UAVs for marine atmospheric boundary layer studies.</p>

Generalized numerical models for simulating gas hydrate and free gas accumulation in marine sediments have been developed. These models include several physical processes such as phase equilibrium of gas hydrates, multiphase fluid flow in porous media, biogenic methane production, and sedimentation-compaction of sediments over geologic timescales. Non-dimensionalization of the models lead to the emergence of important dimensionless groups controlling these dynamic systems, such as the Peclet number, Damkohler number, and a sedimentation-compaction group that compares permeability to sedimentation rate. Exploring the entire parameter space of these dimensionless groups helps in delineating different modes of gas hydrate and free gas occurrence, e.g., no hydrate and hydrate with or without underlying free gas. Scaling schemes developed for these systems help in summarizing average gas hydrate saturation for hundreds of simulation results into two simple contour plots. The utility of these contour plots in predicting average hydrate saturation is shown through application to different geologic settings. The depth to the sulfate-methane transition (SMT) is also developed as an independent proxy for gas hydrate saturation for deep-source systems. It is shown through numerical modeling that scaled depth to the SMT correlates with the average gas hydrate flux through the gas hydrate stability zone (GHSZ). Later, analytical theory is developed for calculating steady-state concentration profiles as well as the complete gas hydrate saturation profile from the SMT depth. Application of this theory to several sites along Cascadia Margin indicates that SMT depth can be used as a fast and inexpensive proxy to get a first-order estimate of gas hydrate saturation, compared to expensive deep-drilling methods. The effect of overpressure development in low permeability gas hydrate systems is shown to have an important effect on gas hydrate and free gas saturations. Specifically, overpressure development decreases the net amount of gas hydrate and free gas in the system, in addition to extending the base of the hydrate stability zone below the seafloor by a relatively small depth. We also study the role of upward free gas migration in producing long, connected free gas columns beneath the gas hydrate layer. Finally, two-dimensional models are developed to study the effect of heterogeneities on gas hydrate and free gas distribution. Simulation results show that hydrate as well as free gas accumulates in relatively high saturations within these high permeability sediments, such as faults/fracture networks, dipping sand layers, and combinations of both, due to focused fluid flow.

The exchange of moisture and heat between the atmosphere and the Earth's surface fundamentally affect the dynamics and thermodynamics of the climate system. In order to trace moisture flow through the climate system and examine its impact on climate, a hydrologic cycle and a land energy balance have been developed and incorporated into a coupled climate-thermodynamic sea ice (CCSI) model. The expanded CCSI model has been tested by comparing computed climate parameters with available observations and GCM modeling results. In general, the expanded model does a good job in simulating the large scale features of the atmospheric circulation and precipitation in both space and time. The expanded model has been used to examine the possibility that increased levels of CO$\sb2$ in the atmosphere may induce the growth of Northern Hemisphere ice sheets. Results of the study indicate that if summer ice albedo is high enough, and there is some mechanism for initially maintaining ice through the summer season, then it may be possible to have ice sheet growth under the conditions CO$\sb2$ induced warming, mainly the result of decreased summer ice melt in response to the higher land ice albedo, and not an increase in precipitation. The expanded model has also been used to examine the impact of Milankovitch solar radiation variations on the climate system, to study the mechanisms that produce glacial-interglacial cycles, especially with respect to the initiation of ice sheets. The results show the Milankovitch solar radiation variations affect the climate system most in the polar regions with the mean annual surface air temperature varying directly in response to changes in the annually averaged incoming solar radiation. However, the seasonal variations in the surface air temperatures are much more complex with large magnitude variations for brief times during the year. The study indicates that ice sheets may start to grow under the conditions of low insolation that occurred at 25, 70, and 115 kyr BP and a land ice minimum albedo of 0.53, with the largest growth rate at 115 kyr BP, approximately when the current 100 kyr cycle began as observed in the geological record.

A new dynamic service model based on granular material rheology is presented. The service model is coupled to both a mixed-layer ocean model and a 1-layer thermodynamic atmospheric model which allows for an ice-albedo feedback. Land is represented by a 6-meter thick layer with a constant base temperature. A 10-year integration including both thermodynamic and dynamic effects and incorporating prescribed climatological wind stress and ocean current data was performed in order for the model to reach a stable periodic seasonal cycle. The commonly observed lead complexes, along which sliding and opening of adjacent ice floes occur in the Arctic sea-ice cover, are well reproduced in this simulation. In particular, shear lines extending from the western Canadian Archipelago toward the central Arctic, often observed in winter satellite images, are present. The ice edge is well positioned both in winter and summer using this thermodynamically coupled ocean-ice-atmosphere model. The results also yield a sea-ice circulation and thickness distribution over the Arctic which are in good agreement with observations. The model also produces an increase in ice formation associated with the dilatation of the ice medium along sliding lines. In this model, incident energy absorbed by the ocean melts ice laterally and warms the mixed layer, causing a smaller ice retreat in the summer. This cures a problem common to many existing thermodynamic-dynamic sea-ice models. / The origin and space-time evolution of Beaufort Sea ice anomalies are studied using data and the sea-ice model described above. In particular, the influence of river runoff, atmospheric temperature and wind anomalies in creating anomalous sea ice condition in the Beaufort Sea is studied. The sea-ice model is then used to track the position of an ice anomaly as it is transported by the Beaufort Gyre and the Transpolar Drift Stream out of the Arctic Basin. / It can be inferred from driftwood data collected in the Canadian Arctic Archipelago that very different sea-ice drift patterns were present in the Arctic Ocean during the Holocene. In this study, the sea-ice model described above is used to examine the different modes of Arctic sea-ice circulation during this period, and also to infer characteristics of century-to-millennial scale changes in Arctic atmospheric circulation. (Abstract shortened by UMI.)

The ocean currents flowing through the earth's main magnetic field are known to induce secondary magnetic fields. Hence, variations in the ocean circulation induce variations in the net magnetic field. This research is aimed at exploring the potential for using geomagnetic data to study variability in ocean circulation and climate. / First, general relativity theory is used to formally establish the proper set of electromagnetic equations to be used for observers in a rotating (accelerating) frame of reference observing a medium (the ocean, in this case) with relative velocity. Extra terms due to rotation are derived and described and a generalized Schiff's charge density is shown to be potentially significant for the application to ocean circulation. / We extend the theory of electromagnetic fields generated by ocean currents. Many analytical solutions are found for idealized ocean features including sheared flow, jets, and a Stommel gyre. Results indicate that the ocean-induced magnetic fields will typically have magnitudes of 10's-100's of nT within the ocean. Outside of the ocean, the magnitudes are smaller (typically 1-10 nT) but decay on scales set by the horizontal scale of the ocean feature. / We investigate the time-scales associated with the adjustment of electromagnetic fields generated by low-frequency ocean currents. We find that the time scales can be quite long, prohibiting a quasistatic assumption in the treatment of the electromagnetic fields generated by the important tidal, inertial, and diurnal-frequency ocean currents. / Three-dimensional explicit time-dependent and steady-state finite-difference numerical models are constructed to study the electromagnetic fields generated by more realistic ocean current and conductivity features. / The ocean currents generate electromagnetic forces on the fluid at the surface of the earth's core. If these forces lead to significant core motion, the effect of the oceans on the generation and variability of the earth's magnetic field may be nontrivial. We estimate the form and magnitude of these forces and make comparisons with observations. Despite many uncertainties, we find evidence to suggest the ocean forcing mechanism may be significant and conclude that this process should be further investigated in the context of a larger study. / This work indicates that it is likely that the geomagnetic record has captured oceanic signals. From a preliminary data analyses we find that aside from the oceanic tidal signals, the magnetic record shows other signals of possible oceanic origin including an apparent correlation between magnetic records from the equatorial Pacific and the Southern Oscillation Index. We discuss the prerequisites that are necessary to extract information about ocean circulation variability from the geomagnetic record.

<p> This study primarily focuses on sea ice variability in the Bering Sea, and its thermodynamic and dynamic controls. </p><p> First, the seasonal cycle of sea ice variability in the Bering Sea is studied using a global fine-resolution (1/10-degree) fully-coupled ocean and sea ice model forced with reanalysis atmospheric forcing for 1980-1989. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The modeled seasonal mean sea ice concentration strongly resembles satellite-derived observations. During winter, which dominates the annual mean, model sea ice is mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast, due to cold air from northerly winds and ice motion away from the coast. South of St. Lawrence Island, winds drive sea ice to drift southwestward from the north to the southwestern ice covered region. Along the ice edge in the western Bering, ice is melted by warm ocean water, which is carried by the Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric pattern seen in the ice edge. </p><p> Second, the year-to-year variability of sea ice in the Bering Sea for 1980-1989 is addressed. While thermodynamic processes dominate the variations in ice volume change in the Bering Sea on the large scale, dynamic processes are important locally near ice margins (both oceanic and land), where local dynamic and thermodynamic ice volume changes have opposite signs with large and similar amplitudes. The thermodynamic ice volume change is dominated by ice-air surface heat flux, which in turn is dominated by sensible heat flux, except near the southern ice edge where it is largely controlled by ocean-ice heat flux. This indicates that surface air temperature, which is specified from observations, strongly controls the ice volume tendency. Ice motion is generally consistent with winds driving the flow, except near certain straits in the north where ice motion largely follows ocean currents. </p><p> This study also addresses Greenland supraglacial lakes on top of ice and ice-dammed lakes adjacent to glaciers. Those surface lakes have been observed to fill and drain periodically, affecting the ice motion over land. This study provides observational constraints on the volume of water contained in and drained from the lakes, based on the repeat laser altimetry. </p>

The relationship between the Arctic and sub-Arctic sea-ice concentration (SIC) anomalies, particularly those associated with the Greenland and Labrador Seas' "Ice and Salinity Anomalies (ISAs)" occurring during the 1960s/1970s, 1970s/1980s, and 1980s/1990s, and the overlying atmospheric circulation (SLP) fluctuations is investigated using the Empirical Orthogonal Function (EOF) and Singular Value Decomposition (SVD) analysis methods. The data used are monthly SIC and SLP anomalies, which cover the Northern Hemisphere north of 450 and extend over the 38-year period 1954--1991. / One goal of the thesis is to describe the spatial and temporal variability of SIC and atmospheric circulation on interannual and decadal timescales. Another goal is to investigate the nature and strength of the air-ice interactions. The air-ice interactions are investigated in detail in the first SVD mode of the coupled variability, which is characterized by decadal-to-interdecadal timescales. Subsequently, the nature and strength of the air-ice interactions are studied in the second SVD mode, which shows a long-term trend. The interactions in the third SVD mode which has an interannual timescale are briefly mentioned. (Abstract shortened by UMI.)